CONSTRUCTION SYSTEM WITH PRE-MANUFACTURED HOLE PATTERNS

Abstract: A construction system having structural members with pre-manufactured rows of holes for fastening. A first kind of structural member (33, 35 and 35a in fig. 2) has a row of holes equally spaced at a distance N. A second kind of structural member for diagonal bracing (43 in fig. 2) has a row of holes equally spaced at a distance equal to the length of the hypotenuse of a right triangle with the other two sides having a length of N or a multiple of N. A third kind of structural member (24 in fig. 2) has two rows of holes equally spaced at a distance N, with the holes of one row perpendicularly intersecting the holes of the other row. Large diameter fasteners (60 in fig. 8), with a cross-hole for a crossing fastener, allow mounting two or more structural members at the same longitudinal disposition to perpendicular sides of a structural member of the third kind.

Description: CONSTRUCTION SYSTEM WITH PRE-MANUFACTURED HOLE PATTERNS BACKGROUND OF THE INVENTION This invention relates to construction systems which use structural members with premanufactured rows of holes. The user selects or cuts the appropriate lengths of members and fastens them together using the holes closest to the desired joint points. The fasteners are usually bolts and nuts. Such systems allow creation of customized structures without drilling holes, or using other manufacturing methods which require substantial equipment and/or special skills. Potential users of such systems are private individuals (do-it- yourselfers) , contractors, maintenance shops, research laboratories and others who have an occasional need for a customized structure, often on short notice. All such users will be referred to in the following as "do-it-yourselfers". When the holes are made in large quantity in an industrial environment, it can also be done more accurately, and at less cost, than is possible at home, at an outside job site or in a small shop set up for another type of activity. The cost involved in making drawings of a custom structure and having it made by a carpenter if wood, or a welder or fabrication shop if steel or aluminum, is high. It also takes considerable time, and the resulting structures are not easily modified. Thus, even if the material cost of a bolt-together system of structural members with premanufactured rows of holes is higher, mostly due to the need to provide more holes than actually will be used, the savings in not needing as many drawings, not having to communicate with an outside shop, the ease of modification, the reusability of components and the faster completion, can compensate for the extra material costs many times over. The potential of this concept has intrigued inventors for a long time, and a number of such systems have been developed. They are however often limited in what they allow to construct, lack strength and stiffness, are expensive and/or more difficult to use than is apparent on first sight. As a result, though some of these systems are available from industrial supply houses which specialize in storage equipment like shelving and pallet racks, rarely are they found in lumber yards, hardware stores and "home-center" type retail outlets which cater to the do-it-yourselfer. The Lemmon Patent One such system is described in U.S. Patent No. 4,620,747 (Lemmon, 1986). It uses wood as the preferred material. Figures 1, 2 and 3 of the patent illustrate the basic rectangular component of this system and its figures 9, 10, 11, 13 and 15 show various ways to construct with it. As its figures 1, 2 and 3 show, the hole pattern consists of two rows of equally spaced holes, one row through the wide sides and a second row perpendicular to the first row through the narrow sides. The holes in the second row have the same hole-to-hole spacing as those in the first row, but are located intermediate of them. Thus the holes in the two rows do not intersect each other. This system has a significant shortcoming in that it does not provide an easy way to install members perpendicular to each other in a "geometrically determined" way. "Geometrically determined" means in this context, that the members supposed to be perpendicular to each other, must be perpendicular to make the fasteners fit. The only practical way to do this with members with rows of equally spaced holes (and all rows having the same hole spacing) , is (usually) to create right triangles with the two short sides having lengths of three and four hole spacings and the long side five hole spacings, or multiples thereof. (In rare occasions right triangles can be created with the short sides having lengths of five and twelve hole spacings and the long side thirteen hole spacings.) Creating these "3,4,5" triangles is often awkward to do, particularly in a spatial structure. For instance if we would like to brace the structure of fig. 10 of above patent in all three perpendicular planes of the structure with these "3,4,5" triangles, it would require that the two members 10D be lowered one hole, so that three hole spacings are available on the vertical members IOC, and also that the members 10B on one side be moved to the other side of the members IOC they are attached to, to assure that the rows of holes in the top surfaces of members 10B on the left are a whole number of hole spacings, from those on the right. When structures as depicted in fig. 13 of above patent, with a "spreader" member, item 67, are used, bracing with "3,4,5" triangles in a plane through the spreader member and the member it attaches to, will be impossible because of the offset between the two rows of holes in the members. The offset between the two rows of holes makes it also impossible to connect two members perpendicular to each other, and in the same plane, to a third member. This is often desired when creating a structure, for instance to support a square or rectangular table top, shelving panel or floor surface along its four edges. It simply cannot be done with this system. The limitations associated with the offset between the two rows of holes bring up the question why this was done. The answer is quite simple, even obvious. If the offset would not exist, we would have two rows of intersecting holes. A fastener through one hole would prevent inserting a fastener through the intersecting hole of the other row. The Pedersen and Podell et al Patents The inventor of U.S. Patent No. 3,355,837 (Pedersen, 1967) found a solution to this problem. He uses two rows of intersecting perpendicular holes, which each have a large bore section and a small bore section. The large bore sections extend from one side past the intersection with the other hole, see fig. 3 of the patent, allowing this way insertion of a cylindrical member shown in its fig. 4. This cylindrical member has six threaded holes allowing fastening from all directions with bolts or threaded rods into those holes. This solution does obviously work, but it is expensive to drill all the holes in the basic members as stepped holes, while the additional cylindrical members also add to the cost and make it more laborious to install the fasteners. In addition, the fact that two sides of the members have large diameter bores and two sides small diameter bores creates an orientation problem. The users will have to constantly think about the proper orientation when assembling, and if by accident something is assembled the wrong way, it may require a substantial disassembly to correct. Like the Lemmon system, the Pedersen system can normally only provide geometrically determined perpendicularity through the use of "3,4,5" triangles, which is awkward in many situations. and requires many closely spaced holes to have sufficient versatility. U.S. Patent No. 4,389,808 (Podell et al, 1983) shows another solution allowing fasteners in perpendicular directions with centerlines crossing. It uses hollow structural members, open on one side, so that the bolts do not have to pass through the whole member, but can be inserted or provided with nuts from the inside. This appears to be a reasonable approach for the light-duty toy building sets it was developed for, but it will be very heavy, bulky and expensive if needing to take substantial loads. Because the structural members are not tubular, but have an open side, they will be weak and flexible in torsion, unless the walls are very thick. The Podell patent does not show any provisions for diagonal bracing. The Munσer and Kirby Patent U.S. Patent No. 3,814,416 (Munger and Kirby, 1974) uses also structural members with two rows of holes, the holes of one row being perpendicular to and intermediate of those of the other row, like previously discussed U.S. Patent No. 4,620,747 (Lemmon) . However, instead of the "spreader" members of the latter, this system uses rods or pipes going through the fastener holes to space members a certain distance apart. See its fig. 2, which shows such a pipe, item 30, and also shows that the members are kept in place with retaining collars, items 52 and 53, with setscrews 58 and 59. Setscrews are, however, not capable of holding reliably any significant load and this system is therefore only usable for light-duty applications as the playground climbing structures it was developed for. Note also that in the sample structure in its fig. 1, the inventors use the pipes with collars only in horizontal positions, in which all the significant loading is perpendicular to the pipes. Again, due to the fact that the two rows of perpendicular holes in the members are located intermediate of each other, this system does not allow installing two beams perpendicular to each other in the same plane to the same post and thus cannot support a square or rectangular table top, shelving panel or floor surface along its four edges. "Slotted Anαle" Patents The most common construction system using members with premanufactured rows of holes is usually referred to as "slotted angle". It typically consists of zinc-plated steel "angles" (L-shaped members) rolled from sheet metal, with an abundance of slotted and round holes in both flanges. Their manufacturers can provide so many holes because the relatively thin sheet metal is easily punched with presses, which is an inexpensive process compared to drilling. Slotted angle is usually sold in lengths of 10 or 12 feet and cut to size by the customer with a shearing tool. Slotted angle is awkward to use and often does not lead to good results for a number of reasons. One of them is the large number of slots and holes, in patterns whose functional rationale is often unclear. It appears that many manufacturers of this product think that the more slots and holes they provide the better it is for the customer. This makes it often unclear how to best bolt it together, as will be apparent from the following discussion of a few of the patents in this field. U.S. Patent No. 3,999,350 (MacKenzie, 1976) shows several configurations of slotted angle in its figures 1 through 5. Its figures 8 through 25 show the complexities of bolting slotted angle together. Note that Figure 12 shows bracing with a "3,4,5" triangle as mentioned before, using the most simple variety of slotted angle of this patent. The method typically used with slotted angle to join a post and two perpendicular horizontal beams together is shown in figs. 10, 13 and 20 of MacKenzie's patent. It has as a major shortcoming that the two horizontal beams are not at the same level, but offset vertically relative to each other by the flange thickness of the upper angle. This means that a table, shelving or floor panel can only be evenly supported at its four edges by adding filler strips, which not only increases cost and assembly time, but also is a very awkward operation as it is difficult to keep those filler strips in place. U.S. Patent No. 3,648,426 (Chaudhary, 1972) shows two more varieties in its figs. 1 and 3. This inventor, in contrast with the previous one, does not show how structures can be made with his invention, but particularly with the type shown in its figure 3, it appears that it must be complex. U.S. Patent No. 2,632,533 (MacKenzie, 1953) shows a more simple slotted angle configuration, including illustrations of how to use it. It uses holes slotted in a direction perpendicular to the length direction of the angles, as this patent application does for a mounting angle used in combination with the basic construction system. However, the arrangement of the slots in MacKenzie's patent, the slots being part of a pattern alternating those slots with round holes, is quite different and serves a completely different purpose. They accommodate the shift of the angles relative to each other due to flange thickness, when nested inside each other. In contrast, this patent application uses slots to accommodate manufacturing tolerances and to allow two different mounting positions, as will be discussed later. MacKenzie's patent also shows as an aid in mounting angles to each other at other angles than 90 degrees, for instance for diagonal bracing, a gusset plate, item C in figures 5 and 6. It is shaped as a quadrant of a circular plate, with radial rows of holes. However, such a gusset plate is very awkward and time consuming to use, and allows only a very limited number of relatively small attachment bolts, under some angles only one or two per joint. Further, sheet metal angles are not very stiff in torsion, resulting often in too flexible structures. Also, the relatively small bolts used with slotted angle, typically 1/4 or 5/16-inch diameter, do not always give sufficient holding power, particularly when mounted in slots. Finally, the shearing to length, which usually goes through one or more of the holes or slots, creates ugly ends with sharp corners. Because of these shortcomings, and in spite of the fact that industrial supply houses specializing in storage equipment often carry it, slotted angle is not used much in the industrial environment. It is rarely sold in retail outlets catering to the private do-it-yourselfer. OBJECTIVES In view of the foregoing, the objectives of this invention are to provide a versatile construction system of the type having structural members with pre-manufactured rows of holes, which: 1. Allows easy diagonal bracing for creating square relationships and providing strong and stiff structures. 2. Allows mounting two or more beams in the same plane perpendicular to each other to the same post. 3. Achieves both simplicity of assembly and modest cost by minimizing the number of holes and making them all the same size without steps. 4. Allows easy modification and disassembly, with removed parts being re-usable for new structures. 5. Allows do-it-yourselfers and shops not set up for making structures, to create accurate structures fast, by giving them structural members with highly accurate hole patterns, precut accurately to length. Making such accurate components is difficult to accomplish in a do-it- yourself environment, but can be achieved relatively easily and at a modest cost in an industrial environment through the use of advanced machinery, special tools and fixtures. Further more limited objectives will become apparent from the detailed description. SUMMARY OF THE INVENTION Briefly, the construction system of the present invention consists of: three types of structural members, three types of fastener assemblies, spacer members, and mounting angles. The three types of structural members in a preferred embodiment are: 1. Posts, square in cross section, with two lengthwise rows of holes through the sides, the holes of one row perpendicularly intersecting the holes of the other row. The holes all have the same size and are equally spaced at a distance N. 2. Beams, rectangular in cross section, with a single lengthwise row of holes through the wide sides. The holes have the same size as those in the posts, and are also equally spaced at a distance N. 3. Diagonals, rectangular in cross section, with a single lengthwise row of holes through the wide sides. The holes have the same size as those in the posts and beams, but are equally spaced at a distance equal to the hypotenuse of a right triangle, with the other two sides of the triangle having a length equal to N or a multiple of N. The lengths of those two sides can be the same or different. The three types of fastener assemblies are: 1. Straight-through fastener assemblies consisting of bolts, solid bars threaded at both ends, or pipes threaded at both ends, with an outside diameter slightly less than the size of the holes in the structural members, which can bolt together "sandwich style" two or more structural members with the appropriate number of nuts and washers. 2. Tee fastener assemblies, which consist of a first part which is like a straight-through fastener, except that it has in addition, a threaded cross-hole, and a second part, preferably an externally threaded cross-bolt, which fastens into this cross-hole and thereby can attach one or more structural members to a post perpendicular to the structural members fastened by the first part. The structural members attached by the cross-bolt are held in the proper location by an indexing sleeve around the cross-bolt or by providing the cross-bolt with an oversize indexing shank of the same diameter as the first part. 3. Crossing fastener assemblies, which consist of a first part like the one used for the tee fasteners, except that the cross-hole may or may not be threaded, a second part, preferably an externally threaded cross-bolt, which screws into this cross-hole or passes freely through it, and is long enough that a third part, preferably a nut or an internally threaded cross-bolt can be used to attach structural members from the other side. Structural members attached by the cross-bolts or nuts are again held in the proper location by indexing sleeves or oversize indexing shanks on the cross-bolts. The spacer members are tubular sleeves of varying length, which fit over fasteners, thereby allowing to space apart structural members while allowing full load transfer. The mounting angles are L-shaped members which allow attaching panels and other components to structural members, using other fastening means than the ones described. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows isometric views of the three types of structural members of this invention. Fig. 2 is an isometric view of a workbench frame constructed using a preferred embodiment of the invention. Fig. 3-A is a section through the workbench frame of fig. 2, as indicated in that figure with arrows 3. Fig. 3-B is a section through a narrower bench using a different diagonal bracing element. Fig. -A shows how discrete markings can show which side of a structural member is accurately located relative to the hole centers. Fig. 4-B shows how line marking can show which side of a structural member is accurately located relative to the hole centers. Fig. 5-A shows how discrete off-center markings can also indicate which end is located accurately relative to the hole centers. Fig. 5-B shows how off-center line marking can also indicate which end is located accurately relative to the hole centers. Fig. 6 is a section through a post of the workbench frame of fig. 2, as indicated in that figure with arrows 6. It shows how a tee fastener assembly can attach two beams or other structural members perpendicular to each other to the post. Figs. 7, 8 and 9 are sections similar to fig. 6 showing different tee fastener configurations. Fig. 10 shows a side view and an end view of an optional fastener configuration for the fastener assembly of fig. 8. Fig. 11 shows another optional fastener configuration. Fig. 12 is a section through a post showing a crossing fastener assembly attaching four structural members to the four sides of the post. Fig. 13 is a section similar to fig. 12 showing a different crossing fastener configuration. Fig. 14 is an isometric view of a small workbench frame constructed using long fasteners with spacers. Fig. 15 is an isometric view of a wide beam with an off-center row of holes attached to a post. Fig. 16 is an isometric view of a mounting angle. Fig. 17 is an isometric view showing how the mounting angles can be used to attach panels to structural members. Fig. 18 shows how the mounting angles can be used to support cross-beams such that their top surfaces are flush with those of the beams attached to. In the figures showing assemblies the fasteners are often omitted for clarity. If that is the case it is assumed that fasteners as depicted in other figures of the drawings are used. Of course, if dowels flush with the surface are used as fasteners, the pictorial representation will be the same as when there are no fasteners in the holes. DETAILED DESCRIPTION Basic Structural Components and Diagonal Bracing Fig. 1 shows the three basic structural components or members of this construction system. They are shown in the shape they would have in the preferred embodiment, which will be discussed in more detail later in this description. The posts 21, 22, 23 and longer ones not shown, have two lengthwise rows of holes through the sides, the holes of one row ideally perpendicularly intersecting the holes of the other row. Also, ideally the holes all have the same diameter and are equally spaced at a hole-center to hole-center distance N. N is a basic hole spacing chosen for the specific application of the construction system. The posts are primarily intended to be vertical supports, but can also be used in other orientations. The beams 31, 32, 33 and longer ones not shown, have a single lengthwise row of holes through the side. Ideally the holes have the same diameter as those in the posts and are equally spaced at the same hole-center to hole-center distance N. The beams are primarily intended to be horizontal ties between posts, and to be supports for horizontal surfaces, like table tops, shelving panels, floors, etc., but can also be used in other orientations. This construction system uses several types of diagonals, which ideally have like the beams a single lengthwise row of holes through the side. Also, ideally the holes have the same diameter as those in the posts and beams. Each type of diagonal has its own hole-center to hole-center distance for a specific bracing angle. This hole-center to hole-center distance equals the length S of the hypotenuse of a right triangle with one side adjacent the right angle having a length N or 2N and the other side adjacent the right angle having a length N, 2N, 3N or 4N. Hole spacings based on the hypotenuse of right triangles with one or both of the short sides equal to a larger multiple of N are also possible, but unlikely to be practical, except for very special situations. Diagonals based on a right triangle with both sides adjacent the right angle having a length N are shown in fig. 1. Those diagonals 41, 42, 43 and longer ones not shown, have their holes equally spaced at a hole-center to hole-center distance S equal to N times the-square-root-of-two, that is 1.414 times as far apart as those in the posts and beams. These diagonals are primarily intended to diagonally brace structures by being positioned under angles of 45 degrees with posts and beams, but can also be used in other orientations. Their ends can be cut square like the beams, but for reasons discussed later the pointed end configuration shown is preferred. A second type of diagonal, based on a right triangle with the sides adjacent the right angle having lengths of N and 2N, has a hole-center to hole-center distance S equal to N times the- square-root-of-five, that is 2.236 times as far apart as those in the posts and beams. This allows to diagonally brace structural member sections of a length N to sections of a length 2N, or multiples thereof, thus with bracing angles of 26.565 and 63.435 degrees, but these diagonals can also be used in other orientations. The shape of their ends will also be discussed later. Similarly, diagonals for bracing under different angles, based on different right triangles are possible. Thanks to the fact that the diagonals of the first type have a hole spacing which is the-square-root-of-two times as large as that of the posts and beams, it is extremely easy to diagonally brace a structure with them. A two-hole diagonal will brace a two-hole beam section to a two-hole post section, a three-hole diagonal will brace a three-hole beam section to a three-hole post section, etc. This is illustrated in fig. 2, which shows how a simple workbench frame can be constructed with this system. It consists of four 5-hole posts 24, tied together horizontally by four 4-hole beams 33, two 8-hole beams 35, and a special 8-hole beam 35a, and diagonally braced with three 4-hole diagonals 43. The special beam 35a, which will be discussed later, can be replaced by a standard beam 35. Note that the two diagonals on the sides brace the structure by creating triangles, while the one in the back creates trapezoids. The latter is somewhat less stiff than the former, because it relies on the ability of the beams connected by the brace to resist bending, but it is adequate for most do-it-yourself situations. Fig. 3-A shows a section through the workbench of fig. 2. Arrows 3 in fig. 2 indicate where the section is taken. Note that the intermediate holes of the diagonals line up horizontally and vertically with the holes in the posts and beams and thus allow mounting additional members in horizontal or vertical position, by fastening to posts and diagonals or beams and diagonals. Because the two members connected this way are not always in the same plane, it may require the use of spacers, for instance in the form of bushings around the fasteners. Fig. 3-A also illustrates why a 90 degree pointed end configuration for the diagonals is preferred. As can be seen in the top right corner, it eliminates interference with beam 35 and the top panel, which is not shown, but would rest on top of beam 33. (See fig. 17 for an illustration of an example top panel mounting.) If the end of the diagonal would be cut square short enough to not cause these interferences, there would not be enough material left around the hole. Note also that the distance from the last hole in a post or beam to the end, and from the last hole in a diagonal to the two surfaces of a pointed end, are slightly less than the distance from the hole to the side of the member attached to, so that inaccuracies in manufacturing will not cause interferences. Fig. 3-B shows a section similar to fig. 3-A through a narrower version of the workbench of figure 2, which uses a diagonal 41a of the second type. Note that the pointed ends of this diagonal are asymmetric, such that the point-forming end cuts are parallel to, or perpendicular to, the sides of the members the diagonal is attached to. A feature of this system which can be of benefit in certain situations is that it is possible to use the diagonals in two perpendicular directions, for instance horizontal and vertical, and use beams and/or posts to brace them diagonally. For certain situations it would also be desirable to provide some structural members with extra holes intermediate of the basic holes, e.g. hole-center to hole-center spacings of 1/2N, 1/3N, 1/4N, etc. in posts and beams. Fig. 3-B shows as an example posts 24a, which have additional holes such that the hole-center to hole-center spacing is 1/2N. This could for instance be of value if the intent is to use the holes in the posts also to mount shelves or drawers. For other situations it might be desirable to increase the hole-center to hole-center spacing to a multiple of the basic hole-center to hole-center spacing. The beams could have hole spacings of X times N, the diagonals of Y times S and the posts of Z times N, wherein X, Y and Z are whole numbers equal to or larger than one. These larger hole spacings could for instance be of value to reduce the cost of structural members intended for use on larger structures. All rows of holes in the structural members can extend over their full length or only part of their length. In addition it is possible to provide one or more other holes, not related to this system, for other purposes, for instance to attach other components, or to be part of another construction system. The holes in the structural members do not necessarily have to be round, but they can for instance also be square, hexagonal, octagonal, serrated, splined or of another multi-sided shape. Such shapes can also be alternated with each other and with the round holes, as long as their size is the same. "Size" is defined for this purpose as the diameter of round holes or the diameter of the largest circle which fits inside a multi-sided hole shape. Providing multi-sided holes can have merit where combination with another construction or fastening system using such holes is desired. Some or all of the holes can also be elongated or slotted, in which case the "size" of the hole for the purposes of this system will be again the diameter of the largest circle which fits inside the elongated or slotted hole. Generally speaking however such elongated or slotted holes will not be desirable for this system, as they reduce the ability to install structural members perpendicular to each other in a "geometrically determined" way, as discussed in the "Background of the Invention" section on page 3 of this specification. However, for special situations they may have merit, for instance when combining with other construction or fastening systems, particularly if such other systems would provide means to secure the fasteners in a centered or pre-determined off- center position, thus retaining the feature of geometric determination. Though most applications of this system are expected to be three-dimensional structures, like the workbench frame of fig. 2, there will also be situations where using it for a two- dimensional structure has merit. This could for instance be situations where a structure is attached to an already existing structure. An example would be a special wall structure for mounting ventilation or other equipment, attached to an existing wall. Cross Section of Structural Components The cross section of the posts can have any shape which allows the two rows of perpendicularly intersecting holes. Thus it can for instance be square, rectangular, octagonal, other multi-sided with the number of sides a multiple of four, angle, channel and even round and elliptical shapes. These cross sections, except angles and channels, can be solid or tubular. Similarly the beams and diagonals can have any cross-sectional shape which allows a single row of holes. However, for many applications, square and rectangular cross sections, solid or tubular, are preferred for the following reasons: 1. They create large contact surfaces between clamped together structural members compared to multi-sided with eight or more sides, round and elliptical cross sections. These large contact surfaces cause large frictional resistance against rotation of one structural member relative to the adjacent one around a connecting fastener, and thus increase the strength and stiffness of a structure. 2. The symmetry of square and rectangular cross sections makes assembly easier compared with non-symmetric cross sections like angles and channels. Square and rectangular cross sections present a solid and flat mounting surface on all four sides and there are no flanges in the way of another piece to be mounted as can be the case with angles and channels. The latter require substantial thinking with regard to their orientation and give a lesser number of options for attachment. 3. Closed tubular members are much stiffer in. torsion than open channels and angles. This stiffness in torsion is also a feature of "solid" wood, which has a tubular fiber structure. Though both rectangular and square cross sections can be used for the posts, square is the preferred shape because it means that no thinking has to be done with regard to orientation of narrow and wide faces. Also, the loading of posts usually is in compression and buckling strength is optimum for the square cross section. For the beams and diagonals the rectangular cross section with the row of holes through the wide sides is optimum. They will often be fastened sandwich style to posts and being thinner in the direction of fastening will create a less bulky structure and allow shorter fasteners. Since they have only one row of holes, making them rectangular will not add any orientation problems. Beams will be loaded in bending when supporting loads, for instance through table, shelving or floor panels. They will be able to take more loading for a certain weight per foot if the cross section is rectangular with the long side in the direction of the load. This is not the case with the diagonals which are normally loaded in tension or compression. Thus, when beams are subject to significant bending loads, their height over width ratio will tend to be larger than for diagonals. Preferred Embodiment The workbench frame of fig. 2 is an example of the use of the preferred embodiment for typical do-it-yourself projects using square posts and rectangular beams and diagonals as just discussed. The rows of holes are centered in the sides of the posts, beams and diagonals, except for the special beam 35a, which will be discussed later. It uses wood, to be specific 4 x 4 lumber (standardized at 3-1/2 x 3-1/2 inch cross section) for posts and 2 x 4 lumber (standardized at 1-1/2 x 3-1/2 inch cross section) for beams (except beam 35a) and diagonals. These lumber sizes are available in just about all lumber yards. The hole diameter D is 1-5/64 inch for fasteners 1.050 inch diameter. The fasteners will be discussed in more detail later in this description. The spacing N between hole centers in the posts and beams is 8 inch. The spacing between hole centers in the first type of diagonals is thus 8 times the- square-root-of-two = 11.314 inch and between hole centers in the second type of diagonals 8 times the-square-root-of-five = 17.889 inch. The stiffness of this workbench frame is surprisingly large and allows omission of a lower beam (identical to beams 35) and a diagonal brace (identical to diagonals 43) in the front. Thus this workbench frame can be open in the front which is a very desirable feature for a workbench, at which people may want to sit on a high chair. The beam 35a, which supports the top panel in the front can be attached to the back side of the front posts as shown, or to the front side of those posts, or two beams can be installed, one in each position. These options can be very helpful when desiring to mount vises or other equipment to the bench. The front beam 35a can also be omitted altogether if the top panel is thick enough. The posts, beams and diagonals can be provided in long lengths, for instance 8 feet or 12 feet, and can be cut to length by the users, or they can be precut. Precutting the structural members is a real convenience for the users, as it reduces greatly the work they have to do to put a structure together. In an industrial environment, allowing the use of advanced machinery, special tools and fixtures, it can also be done more accurately and at lower cost than is possible with hand tools at home, at an outside jobsite or in a small shop set up for another type of activity. Precutting is practical for this construction system because the number of holes is minimized and thus the number of possible length options is not very large. The minimized number of holes has also another significant advantage for the users. It reduces the group of components the user can choose from - for the size range of structure contemplated - to a small enough number to not get confused and to be able to make a quick decision which components to use. In the relatively few cases where a very specific dimension is needed, not provided for by the system, the next larger size standard precut members can be taken and cut to size for this special situation. When precutting, it is, as mentioned before, preferable to cut the posts such that the distance from the center of the last hole to the end is slightly less than half the beam width, so that the post ends don't interfere with a table top panel, shelving panel, floor panel or the like, supported by the beams. Similarly, as mentioned before, the ends of the beams are preferably cut so that the distance from the center of the last hole to the end is slightly less than half the post width, so that the beam ends do not interfere with other beams or diagonals mounted perpendicular to them to the same post at the same level. The ends of the 45 degree diagonals are preferably cut in a 90 degree pointed shape, as discussed before, with the distance from the center of the last hole to one of the point-forming surfaces being slightly less than half the beam width and to the other point-forming surface slightly less than half the post width. (See fig. 3-A, top right corner.) In this preferred embodiment, where standard beam width and post width are the same, this results in symmetrical ends for the diagonal. This is a preferred shape as it eliminates thinking about what the correct orientation is. Thus, if beam and post widths are not the same, it is preferable to make the diagonal ends symmetrical anyway, with the distances from the center of the last hole to both point-forming surfaces being equal, and slightly less than half the lesser of the beam width and the post width. A look at fig. 3-B makes it obvious that it is not very well possible to make the ends of the second type of diagonal symmetrical. For maximum strength around the end hole, the end cuts have to be parallel with or perpendicular to the sides of the members attached to, as shown. However, since it is also obvious when they are mounted the wrong way around, this asymmetry is not a problem. Note that figs. 2, 3-A and 3-B show posts, beams and diagonals which are all cut to length in the manner discussed in the previous paragraphs. Note also that the pointed ends of the diagonals, together of course with their larger hole spacing, distinguish them very well from the beams, even if made from the same lumber size. This makes assembly easier and faster, as a quick look already reveals what a structural member's intended use is. The sizes given for the preferred embodiment of this invention are for general do-it-yourself application. Larger scale applications, for instance for use in construction or bridge building, as well as smaller scale applications, for instance for instrumentation setups, model building and toys, are possible. Location of Holes for Maximum Accuracy The just discussed preferred embodiment, which uses 4 x 4 lumber for posts and 2 x 4 lumber for standard beams and diagonals, has the rows of holes centered in the faces of those components. As those faces are nominally 3-1/2 inch wide, the rows of holes are nominally 1-3/4 inch from the edges. Unfortunately, lumber manufacturing methods are quite inaccurate and deviations from the nominal dimensions up to about 1/8-inch are common. Therefore, a preferred way of manufacturing the holes is to locate them exactly 1-3/4-inch from one of the edges instead of centering them in the faces. This will allow to support table top panels, shelving panels, floor panels, etc. evenly, by positioning the "accurate" sides of the supporting members towards those panels. Lumber manufacturing methods also fail to produce consistently straight lumber and bows up to about 1/4-inch in 12-foot lengths are common. Placing the holes exactly 1-3/4-inch from one of the edges implies that the rows of holes follow the curvature of the lumber. This may not appear right on first sight, because it can create assembly problems. However, it is the best solution, because lumber is fairly flexible and can therefore be bent quite easily into shape. Thus, for instance, when installing diagonals, if the holes for the fasteners do not exactly line up, the curved members, particularly the beams, can be bent into shape. The diagonals will then actually force them into a straighter position. To facilitate assembly of structural members with the "accurate" surfaces (accurately located relative to the holes) facing a certain direction, it is beneficial to have those surfaces identified by markings or "indicia". For situations where a member may be cut into smaller sections, it is desirable to do the marking such that this information is not lost for one or more of the cut pieces. This can be done by placing discrete indicia on or near the accurate surface at each hole location. See fig. 4-A, where dots 46 are placed in front of the holes 47. Such dots can have a variety of shapes, for instance round, elliptical, square, rectangular, polygon, star, line segment and others. Such indicia can be stamped on, applied with stickers, they can be indentations or they can be created using other marking techniques. Another way of marking would be to place a line lengthwise on or near the accurate surface, substantially extending at least over the length of the associated row of holes. Such a line can be continuous, dotted, dashed or be of another type. Fig. 4-B shows a line 48 scribed along the accurate surface. For certain applications, the holes are also placed an accurate distance from one of the ends. Ends are often more difficult to mark than sides, but it is possible to indicate which is the accurate end by placing the markings or indicia which indicate the accurate side off-center. See fig. 5-A, which like fig. 4-A, shows discrete indicia 49 on the accurate surface at each hole location, but off-center. Fig. 5-B shows a line 50 scribed similarly off-center along the accurate surface. If this approach is taken it will be necessary to adhere to a convention (or rule). For instance: "When the member is laid down horizontally with the indicia closest to the bottom (as shown in figs. 5-A and 5-B) , when facing those indicia, the accurate end is at the right hand side". Wide Structural Members In the preferred embodiment previously discussed 2 x 4 lumber was used for the standard beams. Where long beams which can carry significant loading are desired, 2 x 4 lumber may not have enough strength and wider beams should be used. With regard to the preferred location of the row of holes in these wide beams, on first sight, centered in the sides as in the 2 x 4 beams, appears best. This would reduce the weakening of the beams to a minimum as the central part of a beam in bending contributes least to its strength. However, it was found that for certain applications it is more practical to locate the row off-center, exactly 1-3/4 inch from one of the edges as in the 2 x 4 beams. This way these wider beams can be combined with the narrower 2 x 4 beams to support a table, shelving, floor or other panel. For instance in the workbench frame of figure 2, the top long beam 35a in front is shown as a wide beam made from 2 x 6 lumber, with an off-center row of holes as just discussed. The edge which is an accurate 1-3/4 inch from the hole centers is located upward. The top panel would thus still be supported by beams along all four edges. The upper beams 33, 35 and 35a in fig. 2, which will support the top panel, are shown there with discrete markings, as discussed in the previous section, facing upward, and thus indicating to the user that a flat support for the top panel is present, provided that the beams do not have too much curvature. The latter problem can be handled by selecting straight beams. Though not obvious on first sight, this turned out to be a very doable approach for the following reasons. First of all it is easy to determine straightness by looking lengthwise along a structural member. Second, as a considerable number of beams will normally be used in places where some curvature is not objectionable (for instance the lower beams in the workbench frame of fig. 2), and straightness of lumber is statistically a rather random property, such selection does not create an excessive number of unusable pieces. These beams with rows of holes located off-center turned out to be also very convenient for railings, when mounted with the edge closest to the holes downward. They stick this way out above the posts and thus hands can slide over them without hitting the posts. See fig. 15 which shows a 2 x 6 beam 91, with an off-center row of holes, attached to a 4 x 4 post 92. Fasteners The preferred fastening method for construction systems, using pre-manufactured rows of holes, has been bolts and nuts, primarily because they are strong and reliable fasteners, which can be easily assembled and disassembled with common handtools. Bolting is also the preferred method for this system, but there are other fastening methods which may be preferred for certain situations. Rivetting can be a good method, particularly when joining metals, for instance when vibrations are present, which can cause bolts and nuts to come loose. Dowels can be a good method, particularly in wood, for instance when a flush appearance is desired. Wood screws, nails and staples can be a good method when the loads are small or insignificant, for instance for attaching panels. Snap-in devices can be useful, for instance for non-load-carrying cover plates which have to be easily removable for access purposes. As discussed in the section on the background of the invention, using regular bolts and nuts creates a problem in the posts. If one bolt is inserted, it becomes impossible to insert a second bolt in the crossing hole. This construction system resolves this problem by increasing the diameter of the first bolt a substantial amount, so that the second bolt can be screwed into a threaded cross-hole in the first bolt, creating a "tee" fastener assembly. To maintain versatility, prevent orientation problems, and minimize manufacturing costs, all the holes in the structural members are increased to this larger size, a little larger than the outside diameter of the first bolt, which in the following will also be called the "straight-through" fastener. To assure that the piece attached by the second smaller diameter bolt is in the right place, an indexing sleeve fitting snugly in the holes is placed around the second bolt, which in the following will also be called the "crossing" fastener. See fig. 6, which shows a horizontal section through the top of the left front post in fig. 2, as indicated in that figure with arrows 6. The section shows the intersecting holes of equal diameter, 51 and 52, the straight-through bolt 53, assembled with nut 54, and optional washers 55, the smaller diameter cross-bolt 56 with washer 58, and the indexing sleeve 57, which has the same outside diameter as bolt 53. As cross-bolt 56 has a considerably smaller diameter than the hole 51 it passes through, the washer 58 is needed or, alternatively, the cross- bolt has to be provided with an oversize head or an integral washer of sufficient size. Note that there is a gap between the outside diameter of bolt 56 and the inside diameter of sleeve 57. This gap is essential, because it allows a certain amount of shift of bolt 53, and thus the cross-hole in it, relative to hole 51 in post 24, in a direction parallel to the centerline of bolt 53. Such a shift is inevitable due to manufacturing inaccuracies in the thickness of beam 33, in the distance from the centerline of hole 51 to the side of the post 24 touching beam 33, the location of the cross-hole in bolt 53 relative to the shoulder of its head, and the thickness of washer 55 under the head. Fig. 7 shows a tee fastener configuration which is identical to the one of fig. 6, except that it uses a bolt 53a which has internal threads at its end, and a screw 59, instead of the nut 54, to fasten the components together. As this screw 59 has again a considerably smaller diameter than the hole 52 it passes through, a washer 58 will be required or, alternatively, screw 59 will have to be provided with an oversize head or an integral washer of sufficient size. Except for length, screw 59 can have the same dimensions as screw 56, as shown. The advantage of this configuration is that the end of bolt 53a does not protrude out of post 24. Thus it would be possible to slide parts at assembly along post 24, past an already installed bolt 53a, and install the screw 59 later, or omit it, if not needed for load-carrying purposes. In the latter case it would of course also be possible to use, instead of bolt 53a, a bolt which does not have the internal threads at its end, but is simply cut off after the cross-hole. In both the configuration of fig. 6 and fig. 7 it will be desirable to align the centerline of the cross-hole parallel with two opposing wrench flats on the bolthead. At assembly this will help positioning the cross-hole in the right direction for installing cross-bolt 56. The bolthead will of course not necessarily have to be hexagonal in shape as shown, but can also be square or be of any other wrenchable shape. Bolts 53 in fig. 6 and 53a in fig. 7, due to their large diameter, will be much stronger than needed for many applications, particularly when made from steel, and joining members made from a soft material like wood. These bolts will also be quite expensive. An alternate lower strength and lower cost tee fastener configuration is shown in fig. 8. The bolt is here replaced by a simple piece of pipe 60, which is externally threaded at both ends. Two nuts 61 are screwed on the ends for fastening. These nuts are shown as "acorn" or "cap" nuts, giving a more finished look and more protection of the threads, for instance in a corrosive environment, but they can of course also be hex nuts as shown in fig. 6 or have any other suitable shape. An additional advantage of the tee fastener configuration of fig. 8 is that it can accommodate a much larger amount of the previously discussed shift of the cross-hole location due to manufacturing inaccuracies, than the configurations of figs. 6 and 7. This is so, because, in the absence of a fixed bolt head shoulder, the pipe fastener 60 can be shifted axially until the cross-hole is approximately back in the center of hole 51. In essence, one of the nuts functions as a bolthead whose distance to the cross-hole is variable. Even though wrenching surfaces on pipe fastener 60 are not really needed for assembly, they can help speeding up assembly, particularly if such wrenching surfaces are aligned with the cross-hole and thus can help position the cross-hole in the right direction. There are many ways to provide such wrenching surfaces. One way would be to increase the length of pipe fastener 60 at one or both ends and provide wrench flats on the added section or sections, such that the nuts can pass over them. Another way would be to provide internal wrenching flats in the hole through the fastener. This could for instance be done by making the hole through pipe fastener 60 not round, but square, hexagonal or of another multi-sided shape. Fig. 10 shows a side view and an end view of a fastener 60a which has a square hole 60b through the fastener and a cross- hole 60c aligned parallel to two opposing flats of the square hole. A fastener of this shape can be made quite easily from plastic or from a special aluminum extrusion with a square hole. Another solution, more suitable to steel, is shown in fig. 11. The fastener 60d is here made from standard "schedule 80" pipe, with one of the ends being deformed to create the square hole 60e, which has flats that are aligned with the cross-hole 60f. Naturally, the other end of the fastener can also be provided with such a square hole. Still another tee fastener configuration is shown in fig. 9. The large diameter fastener 62 consists here of a piece of pipe threaded at the ends internally instead of externally. Two externally threaded screws 63 engage with these ends to hold the joined members together. Again, since these screws are considerably smaller in diameter than the holes 52 they are passing through, washers 64 are needed, or the screws have to be provided with oversize heads or integral washers of sufficient size. Like the configuration of fig. 7, this option has as advantage that fastener 62 does not protrude beyond the fastened structural members and thus it can be installed before other components are slid into place along those members. Fig. 9 also shows another option for the cross-bolting. Instead of the separate cross-bolts 56 and indexing sleeves 57 of figs. 6,7 and 8, a cross-bolt 66 is used, which combines both parts. It has the same threaded portion as bolt 56, but its shank section is increased in size to the same diameter as the indexing sleeve. Of course combining these two parts eliminates the possibility of accommodating manufacturing inaccuracies by positioning cross-bolts and indexing sleeves eccentric to each other. As discussed, the configurations of figs. 8 and 9 can accommodate manufacturing inaccuracies also by shifting the pipe fasteners 60 and 62 respectively, thus do not need this capability. However, the configurations of figs. 6 and 7 do need it, and can therefore not use this one-piece indexing cross-bolt concept. The advantages of the one-piece indexing cross-bolt are the lesser number of parts, and thus faster assembly, while it also eliminates the possibility of accidentally forgetting to install the sleeves. The elimination of a part by creating a double-function part also creates savings by eliminating the administrative and inventory costs associated with carrying a part in inventory. For special situations it will also be possible to use a hybrid tee fastener configuration which uses a piece of pipe which has external thread at one end, and internal thread at the other end. For other special situations it would be possible to provide the piece of pipe with both external and internal threads at one or preferably then both ends. This would give the user more freedom to decide while building a structure how to put it together. If the external threads are used for making an initial structure, the internal threads will be available later to add additional structure or other components, without having to partially or completely disassemble the initial structure. Note that fig. 9 also shows how a third structural member 65 can be attached to a post by using a longer fastener 62, as compared with the length of the corresponding fasteners in figs. 6, 7 and 8. Fig. 12 shows how this fastening concept can be further expanded to mount four structural members to the four sides of a post, creating a "crossing" fastener assembly. The cross- bolt 66a is identical to the cross-bolt 66 in fig. 9, except that it has an extended threaded section, protruding a significant distance out of the straight-through fastener 67. An internally threaded bolt 68, with an outside diameter equal to that of the shank of fastener 66a, thus also able to act as an indexing device, is then screwed onto this extension to fasten a fourth structural member 69. The cross-hole in part 67 can be threaded as shown in fig. 12, but it can also be an unthreaded through hole, allowing cross-bolt 66a to pass through it freely. This is possible because the two cross- bolts 66a and 68 can fasten against each other, without needing support in part 67. Again, as the cross-bolts are also indexing, this concept cannot be used if the straight-through fastener is a bolt as used in figs. 6 and 7. Fig. 13 shows a different crossing fastener configuration, which does allow to use also bolts as straight-through fasteners. It uses a single cross-bolt 56a, of conventional shape, thus having a shank of approximately the same diameter as the outside diameter of the thread, with a nut 56b and two washers 58, and two separate indexing sleeves 57, with significant clearance between the outside of the bolt and the inside of the sleeves, to accommodate manufacturing inaccuracies. The cross-bolt 56a could have a long threaded section, to be screwed first through a threaded cross-hole in the straight-through fastener. However, such a cross-bolt would have to be specially made, as standard bolts are not made with that much thread, while it would also be time consuming at assembly to screw such a long section through. Therefore a straight-through fastener 67a is shown, which is different from fastener 67 in fig. 11 only in that it has a somewhat larger diameter unthreaded cross-hole 70. Bolt 56a can then freely pass through, and needs to have threads only at its end. Alternatively, the same could be achieved with an unaltered part 67, by using as part 56a a bolt with a smaller diameter, so that it can pas freely through the cross-hole. The thread in the cross-hole would have then no function, but could still be useful by allowing alternate use of part 67 for a tee fastener assembly. Thus part 67 would be another two-function part, which, as mentioned before, has the advantage of eliminating a part and all the administrative and inventory costs associated with carrying a part in inventory. Another advantage of this solution would be that it would create more clearance between the bolt and the sleeve and thus allow more manufacturing inaccuracies. For special situations it will be possible to use the crossing fastener configurations of figs. 12 and 13 to mount only two or three structural members to a post, thus use them as tee fasteners. All that has to be done to accomplish this is to shorten the fasteners where a structural member is omitted. Of course it will also be possible, with all fastener configurations, straight-through, tee, as well as crossing, to mount more than one structural member to a side of a post, by using longer fasteners. Another feature is that it is not necessary to make fasteners 60 in fig. 8, 62 in fig. 9, 67 in fig. 12 and 67a in fig. 13 tubular. They can be solid bars, and if fasteners are made from plastic or another low-strength material this can be a very good solution, as it provides more thread in the cross- hole. For the preferred embodiment using 4x4 and 2x4 lumber discussed earlier, the tee fastener configuration of fig. 8 has been used. The large diameter fasteners have been made from 3/4 inch nominal size pipe (standardized at 1.050 inch outside diameter) , externally threaded with 3/4 inch nominal size pipe thread. Pieces of varying length of this pipe, threaded at both ends (called "nipples"), as well as cap nuts, are available in steel and plastic in the plumbing section of most hardware stores. Hex nuts for 3/4 inch pipe thread in steel or iron are also available from those stores. These hex nuts are available in plastic (nylon) from industrial fastener suppliers. The cross-bolt size used is 5/8 inch. Bolts of this size are available in steel and plastic (nylon) from some hardware stores (usually only in steel) and industrial fastener suppliers. For other embodiments for different market segments, which may require smaller or larger components than used for this preferred embodiment, nipples, cap nuts and hex nuts are also available in other sizes, for instance 1/4, 3/8, 1/2, 1, 1-1/4, 1-1/2, 2, 2-1/2, 3, and 4 inch nominal pipe sizes, for all of which there are also standardized pipe threads. The size of the cross-bolts can of course be adjusted easily to different pipe sizes, as a large variety of bolt sizes is available. Construction with Spacers Besides making the just discussed cross-bolting arrangements possible, the large diameter fasteners of this construction system also allow, in combination with spacer tubes which fit over them, to space structural members (posts, beams and diagonals), a significant distance apart and still provide a stiff and strong structure. As the fasteners are large in diameter, the spacer tubes, which should fit reasonably snug over the fasteners to prevent asymmetry, are also large in diameter, which helps the strength and stiffness of the joint. In addition, the large diameter of the fasteners allows tensioning them considerably, which increases the strength of a spacer tube arrangement. As a result, even with plastic fasteners and spacer tubes, this construction system permits surprisingly long spacers without sacrificing much strength and stiffness. A simple four-legged table frame construction using spacer tubes is shown in fig. 14. It uses four 5-hole beams 71, four 7-hole beams 72 and two 3-hole diagonals 73 to create two braced rectangular sides, 74 and 75. These are then tied together by four fasteners 76 with four spacer tubes 77 and eight nuts 78. (One of the spacer tubes 77 is partially broken away in fig. 14 to show the fastener 76 inside it.) Note that this use of the construction system allows constructing three-dimensional structures without posts having two rows of perpendicularly intersecting holes. Instead beams can be used as posts. This design also has more flexibility in changing the depth of the structure than the construction with two-row posts shown in fig. 2, because the fasteners and spacers can easily be made in different lengths, whereas the structure of fig. 2 can be changed in depth only in 8 inch increments. Of course this spacer design is not as strong and stiff as the structure of fig. 2, but for quite a few applications, particularly smaller structures, it is completely adequate. Mounting Angles In many cases it will be necessary to mount to a structure panels (table tops, shelves, floor surfaces, wall surfaces, etc.) or other items which will not transfer much loading to the fasteners attaching them. Those situations do not warrant the large diameter and somewhat more expensive fasteners used for the basic structure of this construction system. At the same time it will often be desirable to fasten those items with "blind" fasteners, instead of "through" fasteners, so that the side away from the structure is smooth, without protruding fasteners. For the do-it-yourself applications the most common panels will be wood (plywood, particleboard, waferwood, etc.). Wood screws will in many cases be the most appropriate fastening method for those, if blind fastening is desired and one wants to maintain the easy disassembly and reusability features of the basic structure. Wood screws also allow fast assembly if the panels or other items can be predrilled in an industrial environment, such that there are no fit problems at assembly. Fastening of panels and other lightly loaded components using wood screws and other low-strength and low-cost fasteners can be accomplished with this construction system by using special mounting angles, made for instance from steel or aluminum. See fig. 16, which shows an isometric picture of such an angle 80, consisting of two perpendicular flanges 81 and.82. Flange 81 has a row of two or more equally spaced slotted holes 83 with a width approximately equal to the diameter (or "size" if the holes ar not round - see page 18) of the holes in the structural members (posts, beams and diagonals). These holes are slotted in a direction perpendicular to the length direction of the angle. The spacing between the centers of the slots is equal to the spacing between the holes in the posts, beams, or diagonals. The distance from the centers of the slots 83 to the outside surface 84 of flange 82 can be any distance desired, but for the common situation of mounting panels it preferably is the distance from the centers of the holes in the beams, posts and diagonals to the edge of the surface to which the panel is to be mounted. In the preferred embodiment using 2 x 4 and 4 x 4 lumber previously discussed, this would be 1-3/4 inch. It is also desirable that the length of slotting towards edge 85 is somewhat more than the thickness of flange 84, so that the mounting angles can also be used to support beams in the manner shown in fig. 18. Mounting angle 80 is here attached to beam 87 with two or more straight-through fasteners 89, each with two cap nuts 61 and two washers 55, at a level which allows it to support beam 88 such that its top surface is flush with that of beam 87 and those two beams can for instance support together a panel. Flange 82 (see fig. 16 again) has also slotted holes with the direction of slotting perpendicular to the length direction of the angle. Their width and spacing however will normally be different than for the slots in flange 81, to be compatible with other types of fasteners, for instance woodscrews or smaller diameter bolts and nuts. Figure 17 shows how these mounting angles 80 can be used to mount a top panel 90 to the beams 33 of a workbench frame (similar to the frame of figure 2), from the bottom, with wood screws which do not protrude through the panel ("blind" fastening) . The slotting of the large holes in flange 81 will assure that the panel 90 can always rest on the beams 33, in spite of manufacturing inaccuracies. The slotting of the small holes in flange 82 will assure that the wood screws can enter predrilled holes in the top panel, in spite of the substantial manufacturing inaccuracies typical for lumber. As these manufacturing inaccuracies are often accumulative they can cause a substantial mismatch. In the case of the top panel mounting on the workbench frame of fig. 2 it could be the thickness errors in two beams 33 plus the thickness errors in two posts 24. As with the other components of this construction system, this mounting angle is designed to allow accurate predrilling of all fastener holes at a modest cost in an industrial environment, such that quick assembly without any additional "in-the-field" rework can be accomplished. Unexpected Advantages Bolts can take loading "in shear" and can also provide a clamping force which allows the joint to take loading "in friction". The latter method of taking the load is preferred, because it means that the connected members do not shift relative to each other when the load reverses. This movement, besides often being objectionable to the user of the structure, can cause the bolts and nuts to work loose. An unexpected advantage of this construction system is that the large diameter fasteners can generate large clamping forces, which allow very substantial load transfer between the structural members in the joints through friction. This feature is largely responsible for the surprising strength and stiffness of the structures created with the fasteners of the preferred embodiment, both in steel (or iron) and in plastic, in combination with the other elements of this construction system. Structures built with this system turned out to be considerably stiffer and stronger than similar ones built with steel angles. Contributing to this unexpected strength and stiffness are the large contact surfaces between the clamped-together square and rectangular structural members. They increase the frictional resistance against rotation of those members relative to each other around a fastener. Such rotation not only makes the structure less strong and stiff, it also can cause the bolts and nuts to work loose. The features of the fasteners of this construction system also allow use of the full potential of wood, if chosen as the material for the structural members. Conventional wood fastening means, like nails, staples, wood screws and small diameter bolts and nuts, cannot do this. Because wood is a soft material it starts to yield around those fasteners long before the strength limit of the wood members as a whole, and often also the strength limit of the fasteners, is reached. In contrast, the large diameter fasteners of this invention create a large contact area with the wood, and thus a much larger load can be carried before the wood around the fasteners starts to yield. The large diameter of the fasteners will at the same time provide them with the larger strength needed to handle this larger load, to a substantial extent even if the fasteners are made from a relatively low-strength material like plastic. In fact, the fasteners of this construction system made from plastic, in combination with wooden structural members, using the dimensions of the preferred embodiment previously discussed, turned out to be a very good match, with surprisingly large strength and stiffness, sufficient for many do-it-yourself situations. As mentioned before, the fasteners can also be made inexpensively from standard metal pipe. These metal fasteners can give higher strength than plastic fasteners when needed. They also work well with structural members made from relatively thin-wall metal square and rectangular tubing, with the large diameter of the fasteners compensating for the thin walls of the structural members. For the do-it-yourself application, wood has however a definite advantage over metal as a material for structural members, in that it is so easy to attach other things to it. Panels, hooks, hinges, etc. can be easily attached to wood with wood screws and other fasteners, which do not require special tools or skills the average do-it- yourselfer is not familiar with. However, for certain applications, particularly in the industrial field, this may be outweighed by the larger strength and stiffness possible with metal tubing and by environmental considerations e.g. fire hazard, presence of chemicals or organisms attacking wood, etc. Another unexpected advantage of the large diameter fasteners is that the large diameter "acorn" or "cap" nuts 61 shown in figures 8, 12, 13 and 18 can be tightened with considerable torque by hand without any tools. Due to their relatively large size they fit well in the more or less circular "grip- opening" between thumb and index finger. This is one of the strongest grip capabilities of a human hand. In combination with the large contact surfaces between the wooden members, resulting in large frictional resistance between the structural members, and the very effective diagonal bracing, hand tightening with this system often creates already enough strength and stiffness for typical do-it-yourself projects. It provides more strength and stiffness than some other systems can achieve with maximum wrench tightening. The heads of the bolts used in these fastening assemblies can also be given a shape similar to that of the cap nuts to facilitate their tightening by hand. Giving bolt heads and nuts a shape allowing tightening by hand does of course not preclude providing also an octagonal, hex, square or other wrenching surface, to allow additional tightening with wrenches if needed. It must be noted that if such wrench flats are not provided, the cap nuts can still be tightened with pipe wrenches. Conclusion This invention provides, through a unique combination of elements, a versatile construction system of the type having structural members with pre-manufactured rows of holes, which: 1. Allows easy diagonal bracing for creating square relationships and providing strong and stiff structures. 2. Allows mounting two or more beams in the same plane perpendicular to each other to the same post. 3. Achieves both simplicity of assembly and modest cost by minimizing the number of holes and making them all the same size without steps. 4. Provides high quality joints with unexpectedly high strength and stiffness, through load transfer by friction, even when using relatively soft materials, like wood for structural members and plastic for fasteners. 5. Allows tightening of fasteners by hand, creating joint strength sufficient for many do-it-yourself applications. 6. Allows do-it-yourselfers and shops not set up for making structures, to create accurate structures fast, by giving them pre-manufactured structural members with rows of holes accurately located relative to each other and to one edge, precut accurately to length, at a reasonable cost. 7. Allows easy modification and disassembly, with removed parts being re-usable for new structures. General Remark While the invention has been mostly described and illustrated herein with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein, without departing from the spirit and scope of the invention.

Claims: CLAIMS What is claimed is: 1. A construction system of the type having structural members with premanufactured rows of holes for fastening, wherein the improvement comprises the combination of: (a) structural members of a first kind having a row of holes, those holes having substantially the same size and those holes in each structural member being substantially equally spaced at a hole-center to hole-center distance X times N, wherein N is a basic hole spacing chosen for the specific application of the construction system and X is a whole number equal to or larger than one, said structural members of a first kind extendable in directions parallel and perpendicular to each other, and (b) structural members of a second kind for diagonally bracing said structural members of a first kind, those structural members of a second kind having a row of holes, those holes all having substantially the same size as the holes in the structural members of a first kind, and being substantially equally spaced at a hole-center to hole-center distance of Y times S, wherein S is the hypotenuse of a right triangle with the other two sides of the triangle each having a length, which can be the same or different, selected from the group consisting of N, 2N and larger multiples of N, and Y is a whole number equal to or larger than one. 2. The construction system of claim 1 further including structural members of a third kind, having two rows of holes, the holes of one row intersecting the holes of the other row in substantially perpendicular fashion, those holes all having substantially the same size as the holes in the structural members of the first and second kind, and those holes in each structural member of the third kind being substantially equally spaced at a hole-center to hole-center distance of Z times N, wherein Z is a whole number equal to or larger than one. 3. The construction system of claim 2 further including fastening means for joining said first, second and third kinds of structural members into structures, by insertion into a selection of said holes in said structural members, such that: (a) said first and third kind of structural members are extendable in directions parallel and perpendicular to each other, and (b) said second kind of structural members are extendable in directions which diagonally brace said first and third kind of structural members they are attached to. 4. The construction system of claim 3, wherein the fastening means include a fastening assembly insertable in a pair of the substantially perpendicularly intersecting holes in structural members of the third kind, said fastening assembly comprising: (a) a first fastening member which has a cross-hole, and (b) a second fastening member extendable through the cross-hole in the first fastening member, whereby those first and second fastening members can attach structural members of the first, second and third kind to substantially perpendicular sides of a structural member of the third kind. 5. The construction system of claim 4, wherein said cross- hole in said first fastening member is threaded and said second fastening member has a threaded section which is screwable into the threaded cross-hole in said first fastening member. 6. The construction system of claim 5, comprising also an indexing sleeve for aligning the structural members fastened together by the second fastening member, said indexing sleeve disposable around the second fastening member. 7. The construction system of claim 5, wherein the second fastening member has a section with an enlarged cross- section, which acts as an indexing device for aligning the structural members fastened together by the second fastening member. 8. The construction system of claim 4, comprising also an indexing sleeve for aligning the structural members fastened together by the second fastening member, said indexing sleeve disposable around the second fastening member. 9. The construction system of claim 4, wherein the second fastening member has a section with an enlarged cross- section, which acts as an indexing device for aligning the structural members fastened together by the second fastening member. 10. The construction system of claim 4, wherein said first fastening member has a lengthwise arranged hole, which comprises wrenching surfaces, which permit rotation of said first fastening member with a wrenching means inserted into said hole. 11. The construction system of claim 10, wherein the cross- hole in said first fastening member is aligned with one or more of the wrenching surfaces in the lengthwise arranged hole, thereby giving the user the opportunity to determine the direction of the cross-hole from the wrenching means position. 12. The construction system of claim 11, wherein the wrenching surfaces in the lengthwise arranged hole form a substantially square cross-section, and the centerline of the cross-hole is parallel to two opposing sides of said square cross section. 13. The construction system of claim 2, wherein the structural members of a third kind have a substantially square cross section and the two rows of substantially perpendicularly intersecting holes in those structural members are arranged nominally along the lengthwise centerlines of two perpendicular sides of the structural member, with the centerlines of the holes substantially perpendicular to the side of the structural member they are in, and in which: (a) the centerlines of the holes in a side are located accurately one-half of the nominal width of a side from one of the adjacent sides, which serves as a reference side, and (b) indicia are provided on or near that reference side to indicate that it is the side to which said holes are accurately located. 14. The construction system of claim 13, wherein the indicia are placed near the holes, on or near the reference side to which the holes are accurately located. 15. The construction system of claim 14, wherein the indicia are of a shape selected from the group consisting of round, elliptical, square, rectangular, polygon, star, and line segment. 16. The construction system of claim 13, wherein the indicia comprise a line placed lengthwise on or near the reference side, said line extending at least substantially over a length equal to the length of said row of holes. 17. The construction system of claim 16, wherein said line is selected from the group consisting of continuous lines, dotted lines, dashed lines and lines comprising both dots and dashes. 18. The construction system of claim 1, wherein the structural members of a first kind have a substantially rectangular cross section and the row of holes in those structural members is arranged nominally along the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to that wide side, and in which: (a) the centerlines of said holes are located accurately one-half of the nominal width of a wide side from one of the narrow sides, which serves as a reference side, and (b) indicia are provided on or near said reference side to indicate that it is the side to which said holes are accurately located. 19. The construction system of claim 18, wherein the indicia are placed near the holes, on or near the reference side to which the holes are accurately located. 20. The construction system of claim 19, wherein the indicia are of a shape selected from the group consisting of round, elliptical, square, rectangular, polygon, star, and line segment. 21. The construction system of claim 18, wherein the indicia comprise a line placed lengthwise on or near the reference side, said line extending at least substantially over a length equal to the length of said row of holes. 22. The construction system of claim 21, wherein said line is selected from the group consisting of continuous lines, dotted lines, dashed lines and lines comprising both dots and dashes. 23. The construction system of claim 1, wherein the structural members of a first kind have a substantially rectangular cross section and the row of holes in those structural members is arranged nominally along a line parallel to but off-center from the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to that wide side, and in which: (a) the centerlines of said holes are located accurately a specific distance from one of the narrow sides, which serves as a reference side, and (b) indicia are provided on or near that reference side to indicate that it is the side to which said holes are accurately located. 24. The construction system of claim 23, wherein the indicia are placed near the holes, on or near the reference side to which the holes are accurately located. 25. The construction system of claim 24, wherein the indicia are of a shape selected from the group consisting of round, elliptical, square, rectangular, polygon, star, and line segment. 26. The construction system of claim 23, wherein the indicia comprise a line placed lengthwise on or near the reference side, said line extending at least substantially over a length equal to the length of said row of holes. 27. The construction system of claim 26, wherein said line is selected from the group consisting of continuous lines, dotted lines, dashed lines and lines comprising both dots and dashes. 28. The construction system of claim 1, wherein the structural members of a second kind, based upon a value of S equal to the hypotenuse of a right triangle in which the lengths of the other two sides are both N, have: (a) a substantially rectangular cross section, (b) the row of holes arranged approximately along the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to that wide side, and (c) both ends symmetrically pointed by two end cuts substantially perpendicular to the wide sides of the member, said end cuts making angles of approximately 135 degrees with the two narrow sides of the member, and thus making an angle of approximately 90 degrees with each other. 29. The construction system of claim 1, wherein the structural members of a second kind, based upon a value of S equal to the hypotenuse of a right triangle in which the lengths of the other two sides are N and 2N respectively, have: (a) a substantially rectangular cross section, (b) the row of holes arranged approximately along the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to said wide side, and (c) both ends pointed by two end cuts substantially perpendicular to the wide sides of the member, said end cuts making angles of approximately 116.565 and 153.435 degrees respectively with the two narrow sides of the member, and thus making an angle of approximately 90 degrees with each other, wherein said end cuts are arranged such that the end cuts on one end are substantially parallel to the ones on the other end. 30. The construction system of claim 1, wherein the structural members of a second kind, based upon a value of S equal to the hypotenuse of a right triangle in which the lengths of the other two sides are N and 3N respectively, have: (a) a substantially rectangular cross section, (b) the row of holes arranged approximately along the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to said wide side, and (c) both ends pointed by two end cuts substantially perpendicular to the wide sides of the member, said end cuts making angles of approximately 108.435 and 161.565 degrees respectively with the two narrow sides of the member, and thus making an angle of approximately 90 degrees with each other, wherein said end cuts are arranged such that the end cuts on one end are substantially parallel to the ones on the other end. 31. The construction system of claim 1, wherein the structural members of a second kind, based upon a value of S equal to the hypotenuse of a right triangle in which the lengths of the other two sides are N and 4N respectively, have: (a) a substantially rectangular cross section. (b) the row of holes arranged approximately along the lengthwise centerline of a wide side of the structural member, with the centerlines of the holes substantially perpendicular to said wide side, and (c) both ends pointed by two end cuts substantially perpendicular to the wide sides of the member, said end cuts making angles of approximately 104.036 and 165.964 degrees respectively with the two narrow sides of the member, and thus making an angle of approximately 90 degrees with each other, wherein said end cuts are arranged such that the end cuts on one end are substantially parallel to the ones on the other end. 32. The construction system of claim 1 further including spacer members, which have at least one passage with a smallest cross sectional dimension substantially equal to or larger than the size of the holes in said structural members of a first and second kind; 33. The construction system of claim 32 further including fastening means, which join said first and second kind of structural members, as well as said spacer members, into structures, by insertion into a selection of the holes in the structural members and the passages in the spacer members, such that: (a) said first kind of structural members and the passages in said spacer members extend in directions parallel and perpendicular to each other, and (b) said second kind of structural members extend in directions which diagonally brace said first kind of structural members they are attached to. 34. The construction system of claim 1, further including mounting angles comprising: (a) a first flange comprising a row of equally spaced slots, with the direction of slotting perpendicular to the length direction of the mounting angle, the width of the slots being approximately the same as the size of the holes in the structural members of claim 1, and the spacing between the centers of the slots being a distance selected from the group consisting of X times N and Y times S; (b) a second flange perpendicular to the first flange, comprising a row of equally spaced slots, with the direction of slotting perpendicular to the length direction of the mounting angle, the width of the slots being smaller, equal to, or larger than the width of the slots in the first flange and the spacing between the centers of the slots being smaller, equal to, or larger than the spacing between the centers of the slots in the first flange.

Inventors: HAMMERSCHLAG PETER G, HAMMERSCHLAG, PETER, G.
Applicants: HAMMERSCHLAG PETER G, HAMMERSCHLAG, PETER, G.
Application year: 1995
Main classification: A47B96
IPC codes: A47B47, A47B96, E04B1, E04C3, F16B12, F16S3