A gyratory compacting apparatus for compacting a specimen of material subjected to pressure while gyrating the material includes a frame for supporting a mold, a mold gyrating carriage, a ram, and a ram driving assembly. The mold gyrating carriage receives a cylindrical mold having a cavity for holding material and an external peripheral flange about which the mold carriage is guided and driven to rotate to gyrate the mold while the ram is drivingly inserted through the open top of the mold. The ram driving assembly is supported by a flexible portion of the frame which flexes in reaction to force transferred by the ram. Strain gauges on the flexible portion of the frame provide feedback control data on ram force to an integrated computer control system which selectively controls the ram driving assembly to control the force transferred by the ram at least partially according to data generated by the strain gauges. The energy required to rotate the mold gyrating carriage around the mold is measured.

FIELD OF THE INVENTION 
The present invention relates generally to a method and apparatus for 
testing materials and, in particular, to a method and apparatus for 
testing paving materials by compaction and gyration. 
BACKGROUND OF THE INVENTION 
Materials testing machines for simulating actual forces upon materials, 
such as the forces of vehicular traffic upon an asphalt surface of a road 
bed, have been devised to produce a sample of material which evidences the 
physical effects of repeated loading by for example compression, 
compaction, shear strain, plane-strain, and thermal reactivity. Such 
machines typically include a material holding mold which is inserted into 
a chamber or carriage which positions the mold for insertion of a ram into 
the mold cavity to compress the material in the mold. The mold may be 
gyrated about a small angle relative to the vertical axis of the ram, by 
motion of the mold carriage, as the material is compressed by the ram to 
simulate actual forces on the material in the application environment. 
U.S. Pat. No. 2,972,249 discloses a kneader compactor which uses opposed 
plungers to compress materials within a mold chuck mounted for gyratory 
oscillation to produce kneading stresses in the material in the mold. 
Gyration of the mold as the material is compressed produces relative 
motion of particles of the material which simulates the physical response 
of asphalt material to vehicle load forces. 
U.S. Pat. Nos. 4,942,768 and 5,036,709 disclose a paving material testing 
machine in which paving material to be tested is placed in a mold held by 
a chuck which is gyrated about a vertical axis while the material is 
compressed in the mold from the bottom by a hydraulically driven ram. As 
the mold chuck is rotated, a portion of the mold chuck in contact with the 
mold dynamically influences the axially adjustable chuck so that 
deformation of the material within the mold induced by the gyration 
changes the angle of gyration. This subjects the material in the mold to a 
gyratory kneading action analogous to the forces exerted by vehicles 
moving over asphalt surfaces. The machine also performs cyclic vertical 
loading by timed control of predetermined applied forces of the hydraulic 
ram upon the sample to simulate the flexing forces of vehicle tires 
rolling upon the asphalt surface. 
Accurate calibration, control and monitoring of the compressive load of the 
ram upon a sample within the mold as the mold is gyrated is critical to 
obtaining accurate test results, i.e., compacted specimens which have 
specified densities, substantially uniform alignment of aggregate 
materials mixed with the specimen, and elastic properties which closely 
approximate real world applications. Precise control of the linear travel 
and compressive force of hydraulically driven rams in compaction devices 
requires the use of comparatively expensive control components. Also, 
hydraulic systems are heat sensitive and require frequent maintenance of 
seals and fluid. 
The angle of gyration of the mold during compaction is also a critical 
factor which determines the amount of kneading action with resultant shear 
stress and strain of the material within the mold. Although the prior art 
devices induce kneading action of the material within the mold, the angle 
of gyration as determined by the density and flow of the material adds a 
variable which complicates accurate interpretation of the test results. 
Prior gyratory compaction testing machines do not provide for a precisely 
fixable and adjustable angle of gyration. 
Automated control and safety of operation of gyratory compactors, each 
vital to obtaining accurate tests results without extensive operator 
training, are features not adequately addressed in the design of prior 
machines. 
SUMMARY OF THE INVENTION 
The present invention provides an improved apparatus and method for 
preparing a specimen of compressed material by gyratory compaction wherein 
the angle of gyration is precisely fixed, and the compressive force of the 
compaction ram upon the material is precisely determinable and controlled 
throughout the compaction process. The operations of the gyratory 
compactor of the present invention are controlled by a fully integrated 
computer control system which controls compaction pressure, gyration 
cycles and rate, and ram travel to produce compacted material specimens by 
a predetermined number of gyration cycles or a predetermined compacted 
specimen height. A stepping motor/load beams feedback drive system 
integral with a lead screw driven compaction ram provides precision linear 
control of ram travel and pressure relative to the specimen to be 
compacted. A completely enclosed compacting chamber and simplified control 
panel allow the compactor to be safely operated and without extensive 
operator training. 
In accordance with one aspect of the invention, a materials testing 
apparatus for subjecting a material to forces is provided which includes a 
mold for containing a quantity of material, a mold supporting frame in 
contact with a rotatable mold carriage also supported by the frame and 
connected to a mold carriage tilt assembly operative to lift a portion of 
the mold carriage to incline the vertical axis of the mold, means for 
rotating the mold carriage about the mold, and a material compaction ram 
connected to a ram driving assembly and drivingly insertable into the mold 
for exerting a compressive force upon material within the mold while the 
mold carriage is rotated about the mold. 
In accordance with another aspect of the invention a gyratory compaction 
apparatus for subjecting a material to forces is provided which includes a 
mold having a mold cavity for receiving a quantity of material, the mold 
having an open top and a closed bottom, a ram axially inserted and driven 
into the mold cavity through the open top of the mold to compact the 
material in the mold cavity, and means for gyrating the mold while the ram 
is inserted and driven into the mold cavity. 
In accordance with another aspect of the invention a material testing 
machine for applying a linear force to a material to be tested is 
provided. The machine includes a frame for supporting a guide for a ram, a 
ram driven for linear movement in the guide by an electrically powered 
motor, load beams as an integral part of the frame and supporting the ram 
driving lead screw, the load beams being flexible in reaction to forces 
transferred by the ram, means for measuring an amount of flexing of the 
load beams, and means for controlling a speed of the ram drive motor in 
response to measured values of flexion of the load beams. 
To the accomplishment of the foregoing and related ends, the invention 
comprises the features hereinafter fully described and particularly 
pointed out in the following detailed description made with references to 
the annexed drawings which set forth in detail certain illustrative 
embodiments of the invention, these being indicative, however, of but a 
few of the various ways in which the invention may be employed.

DESCRIPTION OF PREFERRED EMBODIMENTS 
With reference to FIG. 1, a gyratory compactor is indicated generally at 
10. A frame 11 supports the compactor and peripheral components, housed in 
protective a cabinet 12 attached to the frame. The frame 11 includes a 
lower portion 13 having storage area access doors 14, and an upper portion 
15 having an access door 16 to a specimen mold receiving portion of the 
compactor. A control panel 17 for controlling the operations of the 
compactor, and an emergency stop button 18, are mounted upon the exterior 
of upper portion 15. An extruder, indicated generally at 19, for extruding 
a compacted specimen from a mold as described below, is mounted in the 
base portion of the frame. 
Referring additionally to FIG. 2, there is illustrated in cross-section the 
specimen compacting portion of gyratory compactor which is housed in upper 
portion 15 shown in FIG. 1. In general, the major components of the 
compacting portion of the apparatus include a generally cylindrical mold 
20 (into which a material specimen S is placed) surrounded by a mold 
carriage assembly 21 connected at a bottom end to a circular rotation base 
22 and in roller guided contact at a top end with a mold carriage tilt 
link assembly 23 for aligning upper rollers of the mold carriage assembly 
for rotation about a fixed ring 24. A ram 25 is positioned vertically 
through a guide frame 26 for insertion into mold 20 to compress material 
specimen S. 
A base frame 27 (connected to frame 11 of lower portion 13 of FIG. 1) 
supports a mold base 28 which provides a horizontal surface 29 upon which 
the mold 20 is placed during gyratory compaction of material in the mold. 
The mold base 28 supports and is encircled by a rotation base bearing 30 
connected to circular rotation base 22. The rotation base bearing 30 may 
be for example a crossed roller bearing of sufficient load rating to 
withstand the reaction force through the mold carriage at maximum gyration 
rpm of a fully loaded mold as described below. 
As further illustrated in FIG. 3, a drive chain 31 engaging a sprocket 32 
attached to rotation base 22 (parallel to the plane of rotation) 
rotationally drives rotation base 22 upon rotation base bearing 30 about 
mold base 28. An electric drive motor 33 is powered to rotate shaft 34 to 
rotate drive sprocket 35 in engagement with drive chain 31. By attachment 
of a bottom end of mold carriage assembly 21 to rotation base 22 (by 
fasteners 36 and pins 37), the chain driven rotation of mold base 28 
rotates the entire mold carriage assembly 21 around mold 20, without 
rotating mold 20. 
A chuck 38 may be provided to protrude upward from horizontal surface 29 of 
mold base 28 to contact a key 39 extending from the side of mold 20 (as 
shown in FIG. 4) to insure against any frictionally induced rotation of 
mold 20 during gyration which would interfere with testing requiring an 
exact number of gyrations. 
The primary function of mold carriage assembly 21 is to gyrate the vertical 
axis of the mold 20 about the vertical axis of the ram 25 during 
compaction of material in the mold by the ram. As best shown in FIG. 2, 
mold carriage assembly 21 includes at least two vertical members 41 and 
42, suspended by through pin attachment from a mold carriage ring 44 at 
opposing points on the ring. A third vertical member 43 (shown in phantom 
in FIG. 3) may also be provided equidistant from members 41 and 42 to 
maintain intersection of the vertical axis of the mold with the apex of 
gyration and precisely maintain the angle of gyration during rotation of 
rotation base 22. Vertical members 41 and 42 and 43 each support, by 
horizontal journalled bearings, parallel vertically spaced apart mold 
roller sets 45a and 45b, 46a and 46b and 47a and 47b, respectively, which 
receive and support a radial flange 48 attached to and extending 
horizontally from the outer periphery of mold 20. Each vertical member may 
also have a vertically mounted roller 49 placed between each of the spaced 
apart roller sets for rolling contact with the outer peripheral face of 
radial flange 48 of mold 20 to reduce wear and friction of the mold during 
gyration. 
To offset the vertical axis of the mold 20 within the mold carriage 
assembly to a selected gyration angle, vertical member 41 serves as mold 
carriage lift link, having an upper set of parallel spaced apart rollers 
50a and 50b straddling a ring section 51 of a lift link 52 of the mold 
carriage tilt link assembly 23. Because ring section 51 constitutes a 
radial section of fixed ring 24, upper rollers 50 can travel about fixed 
ring 24 only when lift 52 is raised to align ring section 51 in the same 
plane as fixed ring 24. Lift link 52 is actuated to perform this alignment 
function by, for example, a hydraulic cylinder 53, which can be optionally 
equipped with a self-locking check valve. With fixed ring 24 positioned in 
a plane parallel to horizontal surface 29 of mold base 28, lifting of 
vertical member 41 by mold carriage tilt link assembly 23 to align ring 
section 51 with fixed ring 24, the vertical axis of the mold 20 in the 
mold carriage is tilted to a gyration angle as determined by the length of 
vertical member 41. Driven rotation of rotation base 22 rotates the mold 
carriage 21 and roller sets 45, 46, 47 about radial flange 48 of the mold, 
and upper roller set 50 about fixed ring 24. Roller sets 45 and 47, being 
partially lifted by the tilt link assembly, position radial flange 48 of 
mold 20 in a plane not parallel to horizontal surface 29, i.e., with the 
vertical axis of the mold positioned at an angle out of co-axial alignment 
with the vertical axis of the ram (as indicated in FIGS. 2 and 3) thereby 
positioning the mold for gyration about the foot of the ram. 
To enable fine adjustment of the gyration angle of the mold within the mold 
carriage assembly after alignment of ring section 51 with fixed ring 24, 
vertical member 41 can be adapted to include axis adjustable mounting of 
upper roller set 50 to selectively adjust the distance between the axes of 
upper roller set 50 and lower roller set 45. As shown in FIGS. 5A and 5B, 
shafts 150a and 150b of upper rollers 50a and 50b are each eccentrically 
mounted within respective cams 151a and 151b, each having worm-screw 
threads about their periphery and mounted within lift link 52 to be in 
threaded engagement with corresponding cam adjustment worms 152a, 152b 
also mounted within lift link 52 transverse to the axes of cams 151. 
In operation, for example to change the distance between the axis of upper 
roller 50a and lower roller 45a, cam adjustment worm 152a is turned to 
rotate by worm screw engagement cam 151a which carries the axis of upper 
roller shaft 150a about a circular path offset for example one eighth of 
one inch from the axial center of cam 151a. Cam adjustment worm 152b is 
then turned to rotate cam 151b to bring roller 50b into contact with the 
underside of fixed ring 24. 
Fine pitch threads in the worm screw engagement of worms 152 with cams 151 
provides for minute positional adjustment of the axes of upper rollers 50 
relative to the axes of lower rollers 45 within the range of the offset 
between axes of the cams and upper rollers. The cam adjustment mechanism 
therefore provides for fine gyration angle adjustment within, for example, 
a one and one half degree range provided by the cam/roller axes offset, to 
adjust and fix the gyration angle of the mold within the mold carriage. An 
exact gyration angle within the cam adjustment range is determinable by 
use of a mold jig and clinometer positioned within the mold carriage. When 
a desired gyration angle is set by worms 152, a hydraulic stop 54 is 
adjusted and set to define a linear travel distance of lift link 52 (as 
actuated by hydraulic cylinder 53) which corresponds to the length of 
vertical member 41 for return of the mold carriage and mold to a zero 
degree gyration angle position. 
As shown in FIG. 2, fixed ring 24 is attached to guide frame 26 positioned 
and supported above the mold carriage assembly 21 by tie rods 55 connected 
to base frame 27. Guide frame 26 includes a vertical passage 123 for 
linearly guiding lift link 52 along its vertical axis as actuated by 
vertical hydraulic cylinder 53 fixedly mounted to the top of guide frame 
26. Guide frame 26 further includes a central vertical passage 56 lined 
with a ram sleeve bearing 57 for receiving and guiding a ram 25 linearly 
along a vertical axis into the open top of mold 20. A ram foot 59, of a 
diameter less than the internal diameter of mold 20, is attached to the 
axial end of ram 25 inserted into the mold for compressive contact with a 
mold top plate 61 which is placed directly on top of the material specimen 
S in the mold. The diameter of ram foot 59 may be less than the diameter 
of mold top plate 61 which, in addition to insulating a heated material 
specimen from heat loss, acts to evenly distribute the compressive 
consolidation force of the ram foot across the width of the specimen in 
the mold. The diameter of the mold top plate 61 is preferably made to 
close tolerance with the internal diameter of the mold, to cover the 
entire specimen with only minor contact of the edges of the mold top plate 
with the interior walls of the mold during gyratory compaction. By this 
arrangement, the smaller diameter of the ram foot avoids contact of the 
peripheral edges of the ram foot with the walls of the mold during 
gyration. The ram foot 59 is detachable from the end of the ram for 
exchange with a smaller diameter ram foot used in connection with a 
smaller diameter mold. Molds of different cavity dimensions (diameters) 
can be used with the compactor provided the radial flange 48 is a constant 
diameter to fit within the roller sets of the mold carriage. 
As shown in FIG. 4, the material in the mold is compacted by the ram foot 
59 and the mold top plate 61 against a removable mold bottom plate 62 
which is retained in the bottom of the mold 20 by contact of a radial 
flange 63 of mold bottom plate 62 with an annular lip 64 projecting 
radially inward at the bottom of mold. This structure, in combination with 
the position of radial flange 48 relative to the mold, optimizes the 
geometry near the bottom of the mold where the majority of compaction 
takes place, allowing the mold to gyrate about the mold bottom plate 62 
which remains flush upon horizontal surface 29 as shown in FIG. 3, thus 
minimizing relative motion and wear between the mold bottom plate 62 and 
horizontal surface 29 of mold base 28. Hard self-lubricating surfaces are 
used on the interfacing areas of the mold assembly to reduce wear. 
Referring again to FIGS. 2 and 3, ram 25 is driven linearly along its 
vertical axis by a lead screw 65 threaded through a lead screw nut 66 
fixed to a top end of ram 25. The top end of lead screw 65 is supported 
and journalled to rotate within lead screw thrust bearings 67 mounted 
within a block 84 supported by an upper frame portion indicated in FIG. 3 
generally at 80. A lead screw drive assembly, indicated generally at 68, 
includes an electric stepping motor 69, such as Model #UPD 5913 
manufactured by Oriental Motor Corporation U.S.A., coupled to a gear 
reducer unit 70 which is supported by a bracket 74 attached to block 84. A 
drive gear 71 is attached to a shaft output of gear reducer unit 70 and 
engaged by a toothed drive belt 72 also engaged with a lead screw drive 
gear 73 attached to the top end of the lead screw above lead screw thrust 
bearings 67. A linear position sensor 75, such as for example a linear 
potentiometer, is mounted to block 84 for positioning proximate and 
parallel to the lead screw. A ram position indicator arm 76 extending 
laterally from the top end of the ram 25 moves the mechanical slide 78 of 
the potentiometer which provides an electrical signal to the control 
circuitry indicating a home position of the ram. A rotary encoder 77 
connected to stepping motor 69 provides (through a control system 
described below) a digital indication of linear travel of the ram 
according to the known pitch of the lead screw. By feedback loop control 
of power to stepping motor 69 as described below, the linear position of 
the ram foot relative to horizontal surface 29 of mold base 28 can be 
precisely determined, controlled and monitored. This allows the compactor 
to be programmed to, for example, compact a specimen to a predetermined 
height which corresponds to a calculated desired air void (i.e., density). 
The upper frame portion 80, which supports the lead screw drive assembly 
68, block 84 and thrust bearings 67, is constructed as an integral part of 
the entire frame structure of the compactor. As shown in FIG. 3, upper 
frame portion 80 includes vertical members 81 secured at a bottom end 181 
to the top of guide frame 26 and supporting at a top end 182 outboard ends 
of horizontal load beams 82 attached at inboard ends to block 84 by 
fasteners 85. Load beams 82 are designed to flex in response to the 
stresses which result when force is applied by the ram to a specimen in 
the mold. Redundant strain gauges 83 are applied to surfaces of load beams 
82 to detect the strain which results from deflection of the load beams in 
response to the force being applied by the ram. The relative positions of 
the block 84, as supported by load beams 82, and the lead screw drive 
assembly 68, as supported by bracket 74 attached to block 84, in 
combination with the placement of strain gauges 83 upon surfaces of load 
beams 82, is designed to minimize the effect of the reactive forces from 
the lead screw drive assembly upon accurate measurement by the strain 
gauges of the linear force of the ram. Strain gauges 83 provide an analog 
signal indicative of the magnitude of deflection of the beams and, 
correspondingly, the axial force of the ram foot upon the specimen. By 
operation of the feedback loop control system described below, data 
received from strain gauge measurements is used to determine pulse 
application to stepping motor 69 to, for example, maintain a constant 
consolidation pressure of the ram upon the specimen, or otherwise control 
ram pressure or position in any mode desired. 
The amount of energy required to gyrate and compact aggregate asphalt mixes 
varies dependent in part upon the viscosity of the asphalt oil and the 
type and shape of mixed aggregate. Therefore, a measurement of an amount 
of energy required to gyrate an aggregate asphalt mix sample undergoing 
compaction can yield useful data on physical properties of the asphalt 
mix. To enable measurement of an amount of energy required to gyrate the 
mold about the compacting ram, sensors may be provided in the mold base 
drive train assembly. For example, a power measurement device 133 such as 
a watt meter, capable of measuring voltage and current, may be provided at 
the power input to electric drive motor 33 to provide a measurement of an 
amount of power input to the motor. The analog value of this measurement 
can then be calibrated by an absorption dynamometer (such as a prony brake 
which applies a known frictional load) to factor out mechanical losses in 
the system to yield an accurate value of an amount of effort required to 
gyrate the mold in the gyratory compaction process. 
A fully integrated interactive computer control system is provided to 
control the parameters of the various operations of the gyratory 
compactor. FIG. 6 illustrates the face of control panel 17 as mounted on 
the exterior of the compactor, which includes a screen display 91, such as 
an illuminated liquid crystal display, multiple touch pad entry keys 92 
including START and STOP functions, and indicator lights such as "MACHINE 
READY" and "DOOR OPEN". As set forth in Table I, representative testing 
parameters and functions which can be input through the control panel 
include rotation of the mold carriage (by powered rotation of the mold 
base for example to a home position where the mold carriage opening 
between vertical members 41 and 42 is aligned with access door 16), manual 
control of ram position, actuation of the mold carriage tilt link assembly 
to adjust the mold to the desired gyration angle, consolidation pressure, 
specimen size, and number and rate (rpm) of gyratory revolutions. 
TABLE I 
______________________________________ 
Key Action 
______________________________________ 
Page + .uparw. Moves to other options menu 
Page - .dwnarw. 
Exits other option menu 
Select Selects parameter to be 
changed (value flashes) 
.uparw. or .dwnarw. 
Used to change value of 
flashing parameter 
Enter Stores changed parameters 
Rotate Display rotational status 
Rotate & .uparw. or .dwnarw. 
Rotates mold carriage 
Ram Display ram status 
Ram & .uparw. or .dwnarw. 
Move ram up or down 
Angle Display mold carriage angle 
status 
Angle & .uparw. or .dwnarw. 
Toggles between 0 and gyration 
angle 
Start Starts test sequence 
Stop Pauses test 
Enter and start 
Automatic machine parking 
______________________________________ 
In an automated mode, control system software automatically calculates the 
force required to produce the desired consolidation pressure on the 
specimen being compacted. Data on compaction progress is then displayed on 
screen 91. Once an automated test routine is started parameters may be 
viewed but not changed. Data from the previous five (5) compaction tests 
is stored in volatile memory for purposes of, for example, producing a 
printout such as represented by FIG. 7, showing specimen height vs. 
gyration number for one compaction run and, in columnar form at the bottom 
additional data such as specimen size, ram pressure, etc. Of course all 
such data could be arranged in any chosen format. 
FIG. 8 sets forth a simplified control diagram of the power and control 
system of the gyratory compactor which includes a central computer control 
system (CCS) 95 (including a CPU 104) for receiving and processing signals 
and data to control the operations of the compactor. For example, 
amplified signals from strain gauges 83 are sent through signal 
conditioner 88 for conversion to digital form by an A/D converter 96 for 
input into the CCS 95. The CCS uses this data, for example, to generate a 
signal to a ram drive motor control 105 to ram drive motor 69 to maintain 
a constant consolidation pressure exerted by the ram foot on the specimen 
within a preselected range by use of a modified 
proportional-integral-derivative algorithm which calculates the required 
output for the ram drive motor. The CCS also receives signals from rotary 
encoder 77 on the ram drive motor to generate a signal representing the 
corresponding ram movement and rate of movement for output to display 91. 
By counting the signals of the rotary encoder relative to a ram position 
detected by ram position sensor 75, the CCS can also determine the 
position of the ram foot from the horizontal surface of the mold base. 
Other inputs to the CCS include signals from a gyrating speed sensor 97, 
such as an optical sensor mounted proximate to the mold carriage, signals 
from a gyration angle sensor 98, and data signals input through control 
panel keypad 92. An over-pressure monitor 99 detects signals measured at 
the flexible portion of the frame which are beyond pre-specified 
parameters, such as would be detected with a firm object under the ram 
foot, to instruct the CCS to suspend further linear advancement of the ram 
by a signal to master pass relay 102. A gyration angle control circuit 106 
and gyrating drive power controller 107 also receive a signal from 
over-pressure monitor 99 in the event of excessive ram force to prevent 
change of gyration angle and gyration of the mold during this condition to 
avoid damage to the machine. The magnitude of power supplied to the 
gyrating drive is measured by watt meter 133 which sends readings to the 
CCS. A door safety switch 108 disables power to the machine through the 
CCS to suspend all mechanical movement whenever the door 16 is open. AC 
power is supplied to the machine through a breaker 111 and switch 112. 
Data acquired by the CCS is output through appropriate ports to printer 
113 and/or other peripheral device such as a monitor (not shown) through, 
for example, an RS-232 interface 114. 
Accurate ram force data can be acquired and processed by the CCS by 
calibration of the compactor with a separate calibration kit. A 
preprogrammed calibration routine is reached through a special key 
sequence to prevent inadvertent use. This user friendly routine will allow 
a skilled technician to calibrate the machine with a minimum amount of 
training. Parameters calibrated include consolidation pressure as 
determined by ram force, specimen height, gyration angle, and the speed of 
gyration. Manual control of the system allows simple verification of 
calibrations without actual calibration of the compactor. Calibration data 
and date are stored in non-volatile computer memory. A precision 
non-contact tachometer can be used to verify the speed of gyration. 
The linear force of the ram foot is calibrated with a ring dynamometer. The 
calibration routine prompts the operator to load the ring to a specific 
force, e.g., 2000N. The operator manually controls the ram to apply that 
forced as indicated by the ring dynamometer, and then presses "Enter". The 
CCS stores the required information and prompts the operator for the next 
predetermined load, and the process is repeated until the full range of 
the compactor has been calibrated. The operator may verify any of the 
calibrations before continuing by, for example, reapplying the force to 
the ring dynamometer. The calibration sequence will follow ASTM E4-89 
procedures. 
After the consolidation force has been calibrated over the entire force 
range of the machine, the operator follows a similar process to calibrate 
specimen height. The control system prompts the operator to insert a 
precision gauge block under the ram foot. The block is then loaded 
throughout the full force range applied by the ram foot, as may be 
automatically controlled by the CCS. Several gauge blocks are used to 
calibrate specimen height for the full range of ram travel. By loading 
through the entire operating range of the compactor while a gauge block is 
under the ram foot, accurate data on the internal frame deflection is 
obtained and recorded. The several gauge blocks representing different ram 
positions are use to create a matrix of data for compactor frame 
deflection at various loads and ram extension positions. This data is 
stored and utilized by the CCS during normal operation to eliminate errors 
in measurement due to compactor frame deflection. 
Multiple safety features, such as an emergency stop switch, are 
incorporated into the design of the gyratory compactor including a 
completely enclosed compacting chamber which conceals all moving parts and 
pinch points. Compacting chamber access door 16 is provided with a lockout 
switch which disables the tilt, rotation and ram movement when the door is 
open. This lockout switch further utilizes a special keyed actuator which 
makes disabling of the switch difficult. The CCS monitors the status of 
the door and a light on the control panel indicates when the door is not 
latched. A window in the door allows the operator to view the compacting 
chamber. 
The compactor further includes operation protection features integral to 
the control system to prevent or minimize damage to the compactor in the 
event of a failure. The over-pressure circuitry described in connection 
with FIG. 8 monitors the force of the ram independent of the software to 
ensure that the compactor is operating within its rated capacity. The 
compactor is structurally designed with inherent flexibility to withstand 
an overload of more than twice the maximum compacting force of the ram 
without damage. Limit switches are provided to indicate ram positions 
beyond normal travel. The control system can shut down the compactor 
through a master pass relay circuit 102 (shown in FIG. 8), as can the 
emergency stop switch 103 in the event of a potentially damaging 
condition. Independent circuitry (CPU watchdog 104) is provided to monitor 
the operation of the CCS to ensure proper function. The CCS can be 
programmed to generate error messages to aid in trouble shooting to 
quickly determine the cause of any problem. All critical systems have a 
built-in redundancy to prevent damage should a single failure occur. 
By use of the above-described apparatus, a compacted specimen of hot mix 
asphalt (HMA) material (e.g., asphalt mixed with an aggregate material 
such as crushed stone) can be produced by loading a mold with a quantity 
of HMA material, placing the mold top plate on top of the material in the 
mold and putting the entire mold assembly into an oven for pre-compacting 
heating to a specified temperature, removing the mold assembly from the 
oven and placing it in the compacting chamber in position within the mold 
carriage. With the computer control system preprogrammed with testing 
parameters for constant compaction (consolidation) ram pressure, angle of 
gyration, number and rate of gyration or final specimen height within the 
mold (according to a predetermined air void percentage), the operator 
simply presses the start button and the CCS initiates the test routine by 
running the ram to contact with the mold top plate, tilting the mold 
carriage to the gyration angle, and commencing gyration and compaction at 
the specified rates. At completion of the test the mold carriage is 
actuated to return the mold to a zero degree gyration angle to square the 
specimen within the mold. The ram is then retracted to a home position to 
allow removal of the mold from the compactor. The mold is then placed in 
the extruder 19 which, by operation of hydraulic hand pump 109, drives a 
piston vertically upward against the mold bottom plate to push the 
specimen out of the mold. 
Although the invention has been shown and described with respect to certain 
preferred embodiments, certain variations and modifications may occur to 
those skilled in the art. For example, many different types of motors and 
drive assemblies could be used to drive the various components of the 
gyratory compactor in connection with the computer control system to 
achieve constant consolidation compaction pressure at an exact gyration 
rate. The apparatus may be used to test materials other than asphalt and 
asphalt aggregates. The apparatus may also be used to perform applied 
force testing other than compaction or gyratory compaction. All such 
variations and modifications of the apparatus and method are within the 
purview of the present invention notwithstanding the defining limitations 
of the accompanying claims and equivalents thereof.