Patent Publication Number: US-11642998-B2

Title: Dump trailer and system for a semi-trailer truck

Description:
CROSS-REFERENCE 
     This application claims the benefit of U.S. patent application Ser. No. 17/080,511, filed on Oct. 26, 2020, which is hereby incorporated by reference in its entirety for all purposes. 
     TECHNICAL FIELD 
     This disclosure pertains generally, but not by way of limitation, to a dump trailer and system for a semi-trailer truck. In particular, the dump trailer and system for a semi-trailer truck described herein provide basic operational benefits to the field of moving cargo from one location to another location with a semi-trailer truck. 
     BACKGROUND 
     A semi-trailer truck is the combination of a tractor unit and a semi-trailer to carry freight. The tractor unit is coupled to the trailer with a hitch called a fifth-wheel; and the semi-trailer is configured for the freight being carried. A semi-trailer may, for example, be configured as a dump trailer having a closed end capable of being raised to allow cargo (e.g. road materials or agricultural produce) to slide out an open end that is opposite of the raised closed end. Other configurations include: a box with access doors on the back and/or sides; a car carrier for transporting vehicles; a flatbed trailer for carrying large pieces of equipment; a drop-deck trailer; a double decker configured to carry pallets of cargo; a dry bulk trailer for carrying dry powder materials such as cement, sand, and flour; a livestock trailer for hauling livestock; and, a tanker trailer are used for hauling liquids such as gasoline. 
     In the case of a semi-trailer truck configured with a dump trailer, typically the dump trailer is loaded with cargo at one location and then transported to a different location. At this different location, the closed end is raised to allow the cargo to be ejected from the dump trailer. 
     SUMMARY 
     In one example, a dump trailer for a semi-trailer truck may include: a tub, defining an exterior portion that may include: a web; a left wall adjoining the web; a right wall adjoining the web and symmetrical to the left wall; a closed end adjoining the web, the left wall, and the right wall; an open end oppositely disposed from the closed end and adjoining the web, the left wall, and the right wall; a hinge axis parallel to and offset from the web; a left hinge formed on the exterior portion of the left wall and coaxial with the hinge axis; a right hinge formed on the exterior portion of the right wall and coaxial with the hinge axis; a distal draft arm axis parallel and adjacent to the web, the distal draft arm axis formed on the exterior portion of the web; and a center hinge formed on the web and coaxial with the distal draft arm axis, the center hinge symmetrically disposed between the left wall and the right wall; a coupling plate to engage the dump trailer to the semi-trailer truck, may include: a hydraulic cylinder axis formed on the coupling plate; a left hydraulic cylinder hinge formed on the coupling plate and coaxial with the hydraulic cylinder axis; a right hydraulic cylinder hinge formed on the coupling plate and coaxial with the hydraulic cylinder axis; a proximal draft arm axis formed on the coupling plate; and a draft arm hinge formed on the coupling plate and coaxial with the draft arm axis, the draft arm hinge symmetrically disposed between the left hydraulic cylinder hinge and the left hydraulic cylinder hinge; a draft arm symmetrically disposed between the left wall and the right wall of the tub, the draft arm may include: a proximal end attached to the draft arm hinge of the coupling plate and rotationally attached to the coupling plate about the proximal draft arm axis; and a distal end oppositely disposed from the proximal end, attached to the center hinge of the tub, and rotationally attached to the tub about the distal draft arm axis; a left hydraulic cylinder defining a left cylinder length, the left hydraulic cylinder may include: a proximal end attached to the left hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the left hinge on the tub; and wherein addition of a first amount of fluid changes the left cylinder length; a right hydraulic cylinder defining a right cylinder length, the right hydraulic cylinder may include: a proximal end attached to the right hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the right hinge on the tub; and wherein addition of a second amount of fluid changes the right cylinder length; a rear assembly pivotally attached to the tub at the web adjacent to the open end, the rear assembly may include: a first pair of wheels; and a rear pivot around which the tub rotates; whereby increase in both left cylinder length and right cylinder length cause: the distal end of the draft arm to move away from earth; and the tub to rotate about the rear pivot. 
     In another example, a method of controlling unloading of a dump trailer may include: providing a tub, defining an exterior portion that may include: a web; a left wall adjoining the web; a right wall adjoining the web and symmetrical to the left wall; a closed end adjoining the web, the left wall, and the right wall; an open end: oppositely disposed from the closed end; and, adjoining the web, left wall, and right wall; a hinge axis formed through the left wall and the right wall; a left hinge formed on the exterior portion of the left wall and coaxial with the hinge axis; a right hinge formed on the exterior portion of the right wall and coaxial with the hinge axis; a distal draft arm axis adjacent to the web and on the exterior portion of the web; a center hinge formed on the web and coaxial with the distal draft arm axis; and a center plane symmetrically disposed between the left wall and the right wall; providing a coupling plate, configured to engage the dump trailer to semi-trailer truck, may include: a hydraulic cylinder axis formed on the coupling plate; a left hydraulic cylinder hinge: formed on the coupling plate; and coaxial with the hydraulic cylinder axis; a right hydraulic cylinder hinge: formed on the coupling plate; and coaxial with the hydraulic cylinder axis; a proximal draft arm axis formed on the coupling plate; and a draft arm hinge: formed on the coupling plate; and coaxial with the draft arm axis; providing a draft arm, symmetrically disposed between the left wall and the right wall of the tub, may include: a proximal end rotationally attached to the coupling plate about the proximal draft arm axis; and a distal end: oppositely disposed from the proximal end; attached to the center hinge; and whereby the draft arm is rotationally attached to the tub about the distal draft arm axis; providing a left hydraulic cylinder, defining a left cylinder length, may include: a proximal end attached to the left hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the left hinge on the tub; and wherein addition of a first amount of fluid changes the left cylinder length; providing a right hydraulic cylinder, defining a right cylinder length, may include: a proximal end attached to the right hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the right hinge on the tub; and wherein addition of a second amount of fluid changes the right cylinder length; providing a rear assembly attached to the tub adjoining the web and adjacent to the open end, the rear assembly may include: a first pair of wheels; and a rear pivot about which the tub rotates; a second pair of wheels parallel to the first pair of wheels; a spring assembly may include: at least one leaf spring may include first end and a second end; a first axle attachment on the first end; a second axle attachment on the second end; and a hinge symmetrically attached between the first end and the second end of the leaf spring; wherein the first pair of wheels are attached to the first axle attachment with a first axle; wherein the second pair of wheel are attached to the second axle attachment with a second axle; and wherein the rear pivot about which the tub rotates is coaxial with the hinge of the rear assembly; increasing in both the left cylinder length and the right cylinder length: moves the distal end of the draft arm to away from earth; and rotates the tub about the rear pivot; monitoring perpendicularity of the center plane; increasing either the left cylinder length or the right cylinder length to compress the leaf spring in the spring assembly; and thereby controlling the unloading of the dump trailer. 
     In another example, a dump trailer for a semi-trailer truck may include: a chassis plane formed on the semi-trailer truck, wherein the chassis plane is defined by at least two axles of the semi-trailer truck that are coplanar to the chassis plane; a tub, may include: a web; a left side adjoining the web; a right side adjoining the web; and a center plane formed on the tub, wherein the center plane is symmetrically located between the left wall and the right wall; a draft arm symmetrically disposed between the left side and the right side of the tub, the draft arm may include: a proximal end; and a distal end oppositely disposed from the proximal end, rotationally attached to the web of the tub; a coupling plate to engage the dump trailer to the semi-trailer truck, wherein: the proximal end of the draft arm is rotationally attached to the coupling plate; a left hydraulic cylinder defining a left cylinder length, the left hydraulic cylinder may include: a proximal end rotationally attached to the coupling plate; and a distal end oppositely disposed from the proximal end and rotationally attached to the tub; a right hydraulic cylinder defining a right cylinder length, the right hydraulic cylinder may include: a proximal end rotationally attached to the coupling plate; and a distal end oppositely disposed from the proximal end and rotationally attached to the tub; a rear assembly pivotally attached to the tub at the web, the rear assembly may include: a first pair of wheels; and a rear pivot around which the tub rotates; a perpendicular condition wherein: the center plane of the tub is perpendicular to the chassis plane; and the left cylinder length and the right cylinder length are equal; a canted condition wherein: the center plane is non-perpendicular to the chassis plane; and the right cylinder length and the right cylinder length are different. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The accompanying figures of the drawing, which are included to provide a further understanding of general aspects of the dump trailer and system for a semi-trailer truck, are incorporated in and constitute a part of this specification. These illustrative aspects of the dump trailer and system for a semi-trailer truck, and together with the detailed description, explain the principles of the system, components, and associated methods. No attempt is made to show structural details of the invention in more detail than may be necessary for a fundamental understanding of the system and various ways in which it may be practiced. The following figures of the dump trailer and system for a semi-trailer truck include: 
         FIG.  1    is a semi-trailer truck having a tractor unit provided with a dump trailer; 
         FIG.  2    is a side elevation view of a semi-trailer truck in a transporting condition; 
         FIG.  3    is a side elevation view of a semi-trailer truck a dumping condition; 
         FIG.  4    is a perspective view of a top-front side of a tub of a dump trailer; 
         FIG.  5    is a side elevation view of the left side of the tub of a dump trailer; 
         FIG.  6    is a front elevation view of the closed end a tub of a dump trailer; 
         FIG.  7    is a bottom plan view of a tub of a dump trailer; 
         FIG.  8    is a top perspective view of a rear assembly of a dump trailer; 
         FIG.  9    is a bottom perspective view of a rear assembly of a dump trailer; 
         FIG.  10    is a perspective view of a left spring assembly of a dump trailer; 
         FIG.  11    is a side view of a left spring assembly of a dump trailer; 
         FIG.  12    is a perspective view of a right spring assembly of a dump trailer; 
         FIG.  13    is a side view of a right spring assembly of a dump trailer; 
         FIG.  14    is a of a side elevation view of a rear assembly dump trailer; 
         FIG.  15    is a perspective view of a bottom of a pyramid of a dump trailer; 
         FIG.  16    is a rear elevation view of the rear assembly of a dump trailer; 
         FIG.  17    is a perspective view of a coupling plate of a dump trailer; 
         FIG.  18    is a rear elevation view of the coupling plate of a dump trailer; 
         FIG.  19    is a front top perspective view of a draft arm assembly of a dump trailer; 
         FIG.  20    is a top plan view of the draft arm assembly of a dump trailer; 
         FIG.  21    is a perspective view of a left hydraulic cylinder of a dump trailer; 
         FIG.  22    is an assembled condition of the left hydraulic cylinder of a dump trailer; 
         FIG.  23    is a perspective view of a right hydraulic cylinder (in an exploded condition) of a dump trailer; 
         FIG.  24    is an assembled condition of the right hydraulic cylinder of a dump trailer; 
         FIG.  25    is a bottom front perspective view of a semi-trailer truck; 
         FIG.  26    is a side perspective view of a semi-trailer truck; 
         FIG.  27    is a front left side perspective view of the semi-trailer truck; and 
         FIG.  28    is a side elevation view of the semi-trailer truck. 
     
    
    
     In the appended figures, similar components and/or features may have the same numerical reference label. Further, various components of the same type may be distinguished by following the reference label with a letter. If only the first numerical reference label is used in the specification, the description is applicable to any one of the similar components and/or features having the same first numerical reference label irrespective of the suffix. 
     DETAILED DESCRIPTION 
     The ensuing description provides general aspects of a dump trailer and system for a semi-trailer truck only. The description is not intended to limit the scope, applicability, or configuration of the disclosure. Rather the ensuing description of the general aspects of the apparatus and system will provide those skilled in the art with an enabling description for implementing the apparatus and/or the system. It is understood that various changes may be made in the function and arrangement of the elements without departing from the spirit and scope set forth in the appended claims. It is noted that while the following description is configured on the dump trailer and/or system for a semi-trailer truck, the system and/or components described herein may be claimed or utilized in other applications as well. For example, the trailer and/or system can be used in other trailers or specialty vehicles. Regarding other applications for the components, during the development of the overall system, various aspects were created that may be used in other trailer applications. For example, the draft arm could be an assembly, or it could be a single forged part. Another example is that the hydraulics system (sometimes referred to as a wet kit) could be retrofitted onto existing dump trailers. As such, the following description directed to a dump trailer application is meant to illustrate general aspects of the dump trailer and system for a semi-trailer truck. 
     With reference to  FIG.  1   , a semi-trailer truck  10  generally includes a tractor unit  12  provided with a trailer such as the illustrated dump trailer  100 . While the semi-trailer truck  10  is most-often in a transportation condition (as illustrated in  FIG.  2   ), occasionally the dump trailer  100  is positioned in a dump condition as illustrated in  FIG.  1   . During this dump condition, the weight of the dump trailer  100 , and a load  102  contained therein, are high above ground  20 . At this elevated position, the dump trailer  100  and load  102  are vulnerable to a rollover event. The ground  20  at most level-ground sites is compacted and capable of providing a stable base for the dump condition. However, certain locations are unstable. One such example location is agriculture fields during quick-turn planning events. When using the dump trailer  100  at an unstable location, the load  102  (e.g. tons of seed) may be quickly, safely, and efficiently dumped. As illustrated in  FIG.  1   , if rear wheels of the dump trailer  100  are positioned partially on compacted soil  22  and partially on loose-fill  24 , the dump condition can escalate to a rollover condition (or worse, a rollover event). The mechanics of this rollover event are that a tub of the dump trailer  100  is raised to cause the load  102  to slide down the tub and eject from an open end of the dump trailer  100 . In this condition, most of the weight of the dump trailer  100  and load  102  is supported by the rear wheels (where a pivot point is located). The sudden weight application onto the wheels may cause the loose-fill  24  to unexpectedly compact under the wheels. This unexpected change may result in movement of the wheels and/or shifting which leads to the rollover condition. Traditionally, the operator of the dump process attempts to avoid the rollover event by lowering the tub as fast as possible to try to stabilize the load  102  and change the moment of inertia. Often this is successful, but occasionally the rollover condition escalates to a rollover event. When the unfortunate rollover event occurs, it is expensive and decommissions the semi-trailer truck  10  which is valuable to its operator. 
     With reference to  FIG.  2    showing a side elevation view of the semi-trailer truck  10 , the semi-trailer truck  10  most-commonly exists in the illustrated transporting condition. The dump trailer  100  is docked at its most stable location and the semi-trailer truck  10  is capable of making (short or long) trips between locations. The semi-trailer truck  10  is provided with a cable assembly  110  for power and/or information transfer between the dump trailer  100  and the tractor unit  12 . In one configuration, the cable assembly  110  is provided with a ground wire, a positive wire, a 7-wire cable, a backup air hose, and a hydraulic line. In other configurations, the cable assembly  110  is minimal and only requires a small amount of power and information to be transferred to/from the trailer  100  (e.g. a control system  800  may be provided with an on-trailer hydraulic pump, accumulator, and valves). Occasionally, the operator of the semi-trailer truck  10  desires to separate the dump trailer  100  from the tractor unit  12 , so the cable assembly  110  may be provided with a connector  112  (or multiple connectors if multiple cables exist). The connector  112  enables separation of the cable assembly  110  so a kingpin ( FIG.  18 ,  540   , described later herein), that is the only component connecting the trailer  100  to the tractor unit  12 , can be detached from the tractor unit  12 . 
     With reference to  FIG.  3    showing a side elevation view of a semi-trailer truck  10  the dumping condition, the dump trailer  100  may be provided with a chassis plane  30 , a tub  200 , a rear assembly  300 , a coupling plate  500 , a draft arm assembly  600 , a pair of hydraulic cylinders  700 , 750 , and a control system  800 . The chassis plane  30  is defined by at least two axles of the semi-trailer truck  10  that are coplanar to the chassis plane  30  as best illustrated in  FIG.  3   . When configured as illustrated, the dump trailer  100  has economic benefits of at least one (or more) of the following: requiring less hydraulic oil, reducing/eliminating the need for a hydraulic system on the tractor unit  12  (which is sometimes referred to as a wet kit—an expensive and not ubiquitous subsystem, reduced manufacturing cost of a draft arm (described later herein), reduced hydraulic cylinder costs, and beneficial control of the dumping process through independent control of hydraulic cylinders that cause movement of the tub. Having provided this brief and non-limiting overview, a more detailed description will be provided. 
     With reference to  FIG.  4    showing a perspective view of a top-front side of a tub  200 , the tub  200  may be configured in any of a large number of sizes and layouts such as the illustrated U-shaped channel. The tub  200  defines an interior  202  and an exterior  204 . The tub  200  may have partitions on the interior (baffles) or be configured for a single material as illustrated. The as-illustrated tub  200  generally includes a web  210 , a left wall  220  (left side), and a right wall  230  (right side). The web  210  serves as a base for the entire tub  200  with the left wall  220  attached directly or as illustrated by a chamfered corner. Alternatively, the left wall  220  and the right wall  230  may be portions of planar or non-planar components of the dump trailer  100  (e.g. portions of a curved section of the web  210 , or physical structure extending from the tub  200 ). The right wall  230  is attached to the web  210  directly or as illustrated by a chamfered corner. This U-shaped channel of the tub  200  is elongated to any reasonable length, but one example is 40 feet long (but small configurations, e.g. 21 feet, and long configurations, e.g. 60 feet, may be provided/required/configured). Additionally, the tub  200  may be constructed out of metal such as steel or aluminum and of any thickness suitable for loads and lifespan requirements (e.g. 3/16 thick steel). At one end of the tub  200  a closed end  206  may be formed by a wall of material (either one-piece or multiple-parts fastened together) and an oppositely disposed open end  208  may be capped by a movable door  209  ( FIG.  3   ) that can be opened automatically during a dumping event (or in a more controlled manner by mechanics). 
     With reference to  FIG.  5    showing a side elevation view of the left side of the tub  200 , the tub  200  may be provided with various structural features such as a front stiffening assembly  240 , a rear stiffening assembly  242 , a left structural beam  244 , and a right structural beam  246  ( FIG.  7   ). The front stiffening assembly  240  and rear stiffening assembly  242  are most commonly manufactured out of steel members (as shown) that are attached (e.g. welded) to the exterior  204  of the tub  200 . However, it should be noted that the front stiffening assembly  240  and the rear stiffening assembly  242  may be made of any of a variety of fabrication techniques or deleted as required for a particular configuration. In one of the configurations, the front stiffening assembly  240  is located approximately at a mid-way point between the open end  208  and the closed end  206  of the tub  200 ; and the rear stiffening assembly  242  may be located near the open end  208  of the tub  200  due to the increasing loads applied to this general area during a dumping event. For similar reasons, the left structural beam  244  and the right structural beam  246  ( FIG.  7   ) may be attached to the exterior  204  of the tub  200  and span the distance from the front stiffening assembly  240  and the rear stiffening assembly  242  adjacent to (or adjoining) the web  210 . 
     With continued reference to  FIG.  5   , the tub  200  may also include a left hinge  250 , a right hinge  252 , a hinge axis  260 , and a center axis  270 , and a center hinge  271 . The left hinge  250  may take the form of any of a large variety of mechanisms or features capable of receiving the end of a hydraulic cylinder. One example of the left hinge  250  is a plate with a hole for receiving a yoke; another example of the left hinge  250  is a simple bolt for receiving a ball joint (on the end of a hydraulic cylinder as described later). While the manufacturing tolerances of required to properly assemble the dump trailer  100  likely provide enough movement, in one configuration, the use of a ball joint provides rotation and angular displacement for reasons related to adjusting the dump trailer  100  during dumping (described later herein). As shown in  FIG.  5   , the left hinge  250  may be attached or formed anywhere along the left wall  220  such as the illustrated location between the front stiffening assembly  240  and the closed end  206 . Furthermore, the left hinge  250  may be configured as a plate with a hole that it is welded to the exterior  204  of the tub  200 , adjacent to the left wall  220  adjoining the front stiffening assembly  240  and near a topside  209 . 
     With reference to  FIG.  6    showing a side elevation view of the closed end  206 , the right hinge  252  may be formed on the right wall  230 . In most applications (but not necessarily all), the left hinge  250  and right hinge  252  are coaxial and generally form the hinge axis  260 . The right hinge  252  may take the form of any of a large variety of mechanisms or features capable of receiving the end of a hydraulic cylinder. One example of the right hinge  252  is a plate with a hole for receiving a yoke; another example of the right hinge  252  is a simple bolt for receiving a ball joint (on the end of a hydraulic cylinder as described later). While the manufacturing tolerances of required to properly assemble the dump trailer  100  likely provide enough movement, in one configuration, the use of a ball joint provides rotation and angular displacement for reasons related to adjusting the dump trailer  100  during dumping (described later herein). As also shown in  FIG.  6   , the right hinge  252  may be attached or formed anywhere along the right wall  230  such as the illustrated location between the front stiffening assembly  240  and the closed end  206  ( FIG.  5   ). Furthermore, the right hinge  252  may be configured as a plate with a hole that it is welded to the exterior  204  of the tub  200 , adjacent to the right wall  230  and adjoining the front stiffening assembly  240 . 
     With continued reference to  FIG.  6   , the tub  200  may further include a center axis  270  concentric to a center hinge  271  configured as one single hinge member. The center hinge  271  may be a simple pivot point or, as illustrated, as pair of hinges such a center-left hinge  272  and a center-right hinge  274 .  FIG.  6    also shows that the tub  200  may include a center plane  280 . The center plane  280  is generally located between the left wall  220  and the right wall  230  in a symmetrical configuration (sometime referred to herein as symmetrically formed). 
     With reference to  FIG.  7    showing a bottom plan view of the tub  200 , the center-left hinge  272  may be attached to the left structural beam  244  and the right center hinge  274  may be attached to the right structural beam  246 . The center hinge  271  (either as a single feature or the pair including the center-left hinges  272  and the center-right hinge  274 ) form the center axis  270 . The center axis  270  is generally formed parallel to the hinge axis  260  for purposes of controlling movement of the tub  200  as described herein. With continued reference to  FIG.  7   , the center plane  280  is symmetrical to the left wall  220  and the right wall  230  whereby the hinge axis  260  and center axis  270  pierce through the center plane  280 . 
     With reference to  FIG.  8    showing a top perspective view of a rear assembly  300 , the rear assembly  300  may be provided with a front axle assembly  310 , a rear axle assembly  330 , a left spring assembly  350 , a right spring assembly  390 , a pyramid  430 , and a rear pivot  450 . 
     With continued reference to  FIG.  8   , the front axle assembly  310  includes an axle  312 , a left wheel  314 , a right wheel  316 , a left damper  318 , and a right damper  320 . The left wheel  314  and right wheel  316  are attached to the axle  312  in a manner well known in the art, specifically with hubs that may (or may not include) brakes. If configured with air springs as illustrated in  FIG.  8   , the left damper  318  and the right damper  320  are attached to the leading side of the axle  312  and are provided with a detailed 4-bar mechanism that is known in the art. The axle  312  may also include a left spring contact  322  and a right spring contact  324 , both formed on the axle  312  for receiving spring assemblies (e.g. Left spring assembly  350  and right spring assembly  390 ). 
     With reference to  FIG.  9    showing a bottom perspective view of the rear assembly  300 , the rear axle assembly  330  includes an axle  332 , a left wheel  334 , a right wheel  336 , a left damper  338  and a right damper  340 . The left wheel  334  and right wheel  336  are attached to the axle  332  in a manner as described with the front axle assembly  310 . If configured with air springs, the left damper  338  and the right damper  340  are attached to the leading side of the axle  332 . The axle  332  may also include a left spring contact  342  and a right spring contact  344 , both formed on the axle  332  for receiving spring assemblies. 
     With reference to  FIG.  10    showing a perspective view of the left spring assembly  350 , the left spring assembly  350  may take any of a variety of configurations such as the illustrated configuration including a first axle attachment  352 , a pair of u-bolts  354 , a main leaf spring  356 , a second leaf spring  358 , and a third leaf spring  360 . The main leaf spring  356  has a first end  362  and an oppositely disposed second end  364  with a midpoint  366 . At the first end  362  of the main leaf spring  356 , the plurality of individual springs  356 ,  358 ,  360  are held together by the first axle attachment  352  and the u-bolts  354 . At the second end  364  of the main leaf spring  356 , the left spring assembly  350  may also include a second axle attachment  368  and a pair of u-bolts  370  capture the springs  356 ,  358 ,  360  as illustrated. At the midpoint  366  of the main leaf spring  356 , the left spring assembly  350  may be provided with hinge assembly  372  and a pair of u-bolts  374 . The hinge assembly  372  adjoins the main leaf spring  356  and the u-bolts  374  capture the second leaf spring  358  and third leaf spring  360 . 
     With reference to  FIG.  11    showing a side view of the left spring assembly  350 , the left spring assembly  350  includes an axle plane  376 . The axle plane  376  is defined by the axes (plural of axis) of rotation of the axle  312  of the front axle assembly  310  and the axle  332  of the rear axle assembly  330 , both of the center of rotations of the axles  312 ,  332  reside in the axle plane  376  as illustrated in  FIG.  11   . The hinge assembly  372  includes a pivot axis  378  about which the tub  200  rotates. There may be a left deflection distance  380  defined as the distance between the pivot axis  378  and the axle plane  376 . 
     With reference to  FIG.  12    showing a perspective view of a right spring assembly  390 , the right spring assembly  390  may take any of a variety of configurations such as the illustrated configuration including a first axle attachment  392 , a pair of u-bolts  394 , a main leaf spring  396 , a second leaf spring  398 , and a third leaf spring  400 . The main leaf spring  396  has a first end  402  and an oppositely disposed second end  404  with a midpoint  406 . At the first end  402  of the main leaf spring  396 , the plurality of individual springs  396 ,  398 ,  400  are held together by the first axle attachment  392  and the u-bolts  394 . At the second end  404  of the main leaf spring  396 , the right spring assembly  390  may further include a second axle attachment  408  and a pair of u-bolts  410  capture the springs  396 ,  398 ,  400  as illustrated. At the midpoint  406  of the main leaf spring  396 , the right spring assembly  410  may be provided with hinge assembly  412  and a pair of u-bolts  414 . The hinge assembly  412  adjoins the main leaf spring  396  and the u-bolts  414  capture the second leaf spring  398  and the third leaf spring  400 . 
     With reference to  FIG.  13    showing a side view of the right spring assembly  390 , the right spring assembly  390  includes an axle plane  416 . The axle plane  416  is defined by the axes (plural of axis) of the axle  312  of the front axle assembly  310  and the axle  332  of the rear axle assembly  330 , both of the center of rotations of the axles  312 ,  332  reside in the this axle plane  416  as illustrated in  FIG.  13   . The hinge assembly  412  includes a pivot axis  418  about which the tub  200  rotates. There is a left deflection distance  420  defined as the distance between the pivot axis  418  and the axle plane  416 . 
     With reference to  FIG.  14    showing a side elevation view of the rear assembly  300 , the pyramid  430  may be configured as illustrated with a top  432 , a bottom  434 , a front  436 , a back  438 , a left  440 , and a right  442  ( FIG.  8   ) to generally form an inverted pyramid shape. The top  432 , the bottom  434 , the front  436 , the back  438 , the left  440 , and the right  442  may be constructed out of a variety of materials and/or manufacturing processes, such as out of cold-rolled sheet steel that is welded into a shape defining an interior portion  444  and an exterior portion  446 . The interior portion  444  is often configured with various mechanical items such as components of a braking system or other sub-systems that need a protected location. The top  432  of the pyramid  430  may be attached to the tub  200  in any of a variety of manners, such as by welding. If, for example, the pyramid  430  is welded to the tub  200 , the left  440  is welded to the left structural beam  244  ( FIG.  7   ) near the rear stiffening assembly  242 . This illustrated configuration would also result in the right  442  being welded to the right structural beam  246  ( FIG.  7   ). 
     With continued reference to  FIG.  14   , the rear assembly  300  is further provided with a rear pivot  450 . The rear pivot  450  may be a solid or hollow circular profile, such as the illustrated solid bar of steel. The rear pivot  450  is installed as illustrated so that the rear pivot  450  is attached to the hinge assembly  372  and the hinge assembly  412  ( FIG.  12   ) to provide an axis of rotation about which the tub  200  (and intermediary pyramid  430 ) pivots. 
     With reference to  FIG.  15    showing a perspective view of the bottom  434  of the pyramid  430  with the left wheel  334  of the rear axle assembly  330  removed, the rear assembly  300  is further provided with provisions for attaching the pyramid  430  to the rear pivot  450 , such as left pyramid mount  460  and right pyramid mount  470 . The left pyramid mount  460  is attached to the bottom  434  near the left  440  of the pyramid  430 . The right pyramid mount  470  is attached to the bottom  434  near the left  440  of the pyramid  430 . The left pyramid mount  460  is provided with a hinge such as a hole  462 ; and the right pyramid mount  470  is provided with a hinge such as a hole  472 . When assembled as best illustrated in  FIG.  15   , the hole  462  of the left pyramid mount  460  is coaxial to the rear pivot  450  and capable of forming an axis of rotation about which the tub  200  may rotate relative to the rear assembly  300 . Furthermore, the hole  472  of the right pyramid mount  470  is coaxial to the hole  462  of the left pyramid mount  460  and the rear pivot  450 . 
     With reference to  FIG.  16    showing a rear elevation view of the rear assembly  300  wherein the ground  20  is not level, the components of the rear assembly  300  cooperate to provide independent movement of the tub  200  relative to the rear assembly  300 . This independent movement is best illustrated by the left deflection distance  380  of the left spring assembly  350  and the left deflection distance  420  of the right spring assembly  390  in a levelling process best illustrated by keeping rear pivot  450  ‘level’ to the ground  20 . This leveling process is described herein, but as described one of the purposes is to keep the tub  200  and its load perpendicular to the ground  20  as illustrated by the center plane  280  of the tub  200  as shown. As shown in  FIG.  16   , the center plane  280  is not perpendicular to the ground  20 , therefore the tub  200  is in a canted condition wherein the load held in the tub  200  is unstable when in the dumping condition. 
     With reference to  FIG.  17    showing a perspective view of a coupling plate  500 , the coupling plate  500  may take a number of forms, but one particular form is illustrated as a cuboid shape with a top-surface removed. In this illustrative example, the coupling plate  500  generally defines an interior  502  and an exterior  504  including by a base  510 , a left side  512 , a right side  514 , front side  516  and a back side  518 . The left side  512 , right side  514 , front side  516 , and back side  518  may be integrally formed with the base  510  (e.g. bent out of a flat material) or welded into the illustrated configuration. The coupling plate  500  may have additional features such as: partitions, features, bearing surfaces, brackets, and cable routing features. Additional features illustrated in  FIG.  17    include: a left hole  520 , a right hole  522 , a left hydraulic cylinder clearance  524 , a right hydraulic cylinder clearance  526 , and a draft arm clearance  528 . The left hole  520  is formed in the left side  512  and the right hole  522  is formed in the right side  514  to form a coupling axis  530 . The left hole  520  and the right hole  522  are coaxial to the coupling axis  530 . 
     With reference to  FIG.  18    showing a rear elevation view of the coupling plate  500 , the coupling plate  500  is provided with a feature for attaching the dump trailer  100  to the semi-trailer truck  10  such as a kingpin  540 . The kingpin  540  is formed on the exterior  504  of the base  510 . The kingpin  540  is common in industry and serves to make the dump trailer  100  readily and removably attached to the semi-trailer truck  10  to enable different configurations of the semi-trailer truck  10 . 
     With reference to  FIG.  19    showing a front top perspective view of a draft arm assembly  600 , the draft arm assembly  600  may take a variety of configurations including a tube  610  with a rectangular profile (e.g. a steel tube). The tube  610  includes a top side  612 , a bottom side  614 , a left side  616 , a right side  618 , a proximal end  620 , and a distal end  622 . The sides  612 ,  614 ,  616 ,  618  may create an elongated tube capable of defining a protected interior portion  624  for receiving cables or other components (e.g. cable assembly  110 ). The draft arm assembly  600  is provided with a proximal hinge  630  and a distal hinge  640  located at the proximal end  620  and the distal end  622 , respectively. The proximal hinge  630  and distal hinge  640  may take any of a number of forms, but in the illustrated configuration are configured as a proximal tube  632  and a distal tube  642  capable of receiving individual pins/rods as described later herein. The proximal tube  632  passes through the left side  616  and the right side  618  of the steel tube  610 . The distal tube  642  passes through the left side  616  and the right side  618  near the distal end  622 . 
     With reference to  FIG.  20    showing a top plan view of the draft arm assembly  600 , the proximal hinge  630  defines a draft arm proximal axis  634  and the distal hinge  640  defines a draft arm distal axis  644 . 
     With reference to  FIG.  21    showing a perspective view of a left hydraulic cylinder  700  in an exploded condition, the left hydraulic cylinder  700  may be any of a large variety of hydraulic cylinders, such as the illustrated single-stage cylinder. With the single-stage cylinder, a compressed length is roughly one-half a fully-extended length. In the illustrated configuration, the compressed length is about 13 feet and the extended length is about 20 feet. The left hydraulic cylinder  700  is provided with a body  710  that includes a cap end head  712  and a rod end head  714 . The cap end head  712  is provided with an attachment feature such as the a hole  716  (as illustrated). The rod end head  714  is provided with a sealing feature configured to receive a piston rod  720 . The piston rod  720  is provided with a piston end  722  for sealing against the body  710  and creating a coupling-side cavity  730  disposed between the cap end head  712  and the piston end  722  of the piston rod  720 . The left hydraulic cylinder  700  may also be provided with a rod-side cavity  732  disposed between the rod end head  714  of the body  710  and the piston end  722  of the piston rod  720 . The coupling-side cavity  730  and the rod-side cavity  732  change volumes depending on the position of the piston rod  720  as it extends from and retracts into the body  710 . In order to move fluid, almost exclusively a liquid (e.g. hydraulic oil), into and out of the cavities  730 ,  732 , the left hydraulic cylinder  700  is provided with fittings such as a coupling-side fitting  734  and a rod-side fitting  736 . The locations and existing of these fittings can be as illustrated in  FIG.  21    or moved to different locations on the left hydraulic cylinder  700  (e.g. the coupling-side fitting  734  may be located at the end of the piston rod  720  whereby the length of the piston rod  720  acts as a supply line for the fluid. 
     With continued reference to  FIG.  21   , the left hydraulic cylinder  700  is provided with an attachment hinge  724  formed on the piston rod  720  at a location oppositely disposed from the piston end  722 . The Attachment hinge  724  may take the form of any of a variety of connection mechanisms used in industry, such as a hole  726  as illustrated. The attachment hinge  724  may be a rigid attachment wherein the left hydraulic cylinder  700  remains perpendicular to the attachment point, or it may have a floating configuration wherein the left hydraulic cylinder  700  may move a few degrees from a perpendicular orientation relative to the object it is attached to (e.g. the tub  200  as described herein). 
     With reference to  FIG.  22    showing an assembled condition of the left hydraulic cylinder  700 , the left hydraulic cylinder  700  includes a proximal hinge axis  702  and a distal hinge axis  704 . The proximal hinge axis  702  is coaxial to the hole  716  formed in the cap end head  712 . The distal hinge axis  704  is coaxial to the hole  726  formed in the attachment hinge  724 . In most situations, the proximal hinge axis  702  is parallel to the distal hinge axis  704  and separated by a left hydraulic cylinder length  706  that is variable. In a load leveling event, the distal hinge axis  704  and the proximal hinge axis  702  may be slightly non-parallel in order to adjust to variable ground as will be described later herein. 
     With reference to  FIG.  23    showing a perspective view of a right hydraulic cylinder  750  in an exploded condition, the right hydraulic cylinder  750  may be similar to the right hydraulic cylinder  700 . The right hydraulic cylinder  750  is provided with a body  760  that includes a cap end head  762  and a rod end head  764 . The cap end head  762  is provided with an attachment feature such as the hole  766 . The rod end head  764  is provided with a sealing feature configured to receive a piston rod  770 . The piston rod  770  is provided with a piston end  772  for sealing against the body  760  and creating a coupling-side cavity  780  disposed between the cap end head  762  and the piston end  772  of the piston rod  770 . The right hydraulic cylinder  750  may also be provided with a rod-side cavity  782  disposed between the rod end head  764  of the body  760  and the piston end  772  of the piston rod  770 . The coupling-side cavity  780  and the rod-side cavity  782  change volumes depending on the position of the piston rod  770  as it extends from and retracts into the body  760 . In order to move fluid, almost exclusively a liquid (e.g. hydraulic oil), into and out of the cavities  780 ,  782 , the right hydraulic cylinder  750  is provided with fittings such as a coupling-side fitting  784  and a rod-side fitting  786 . The locations and existing of these fittings can be as illustrated in  FIG.  23    or moved to different locations on the right hydraulic cylinder  750  (e.g. the coupling-side fitting  784  may be located at the end of the piston rod  770  whereby the length of the piston rod  770  acts as a supply line for the fluid. 
     With continued reference to  FIG.  23   , the right hydraulic cylinder  750  is provided with an attachment hinge  774  formed on the piston rod  770  at a location oppositely disposed from the piston end  772 . The Attachment hinge  774  may take the form of any of a variety of connection mechanisms used in industry, such as a hole  776  as illustrated. The attachment hinge  774  may be a rigid attachment wherein the right hydraulic cylinder  750  remains perpendicular to the attachment point, or it may have a floating configuration wherein the right hydraulic cylinder  750  may move a few degrees from a perpendicular orientation relative to the object it is attached to (e.g. the tub  200  as described herein). 
     With reference to  FIG.  24    showing an assembled condition of the right hydraulic cylinder  750 , the right hydraulic cylinder  750  includes a proximal hinge axis  752  and a distal hinge axis  754 . The proximal hinge axis  752  is coaxial to the hole  766  formed in the cap end head  762 . The distal hinge axis  754  is coaxial to the hole  776  formed in the attachment hinge  774 . In most situations, the proximal hinge axis  752  is parallel to the distal hinge axis  754  and separated by a right hydraulic cylinder length  756  that is variable. In a load leveling event, the distal hinge axis  754  and the proximal hinge axis  752  may be slightly non-parallel in order to adjust to variable ground as will be described later herein. 
     With reference to  FIG.  25    showing a bottom front perspective view of the semi-trailer truck  10  and one illustrative configuration of a control system  800 , the control system  800  may include a hydraulic pump  810 , an accumulator  820 , a controller  830 , and a plurality of hydraulic lines  840  (e.g. a pump-to-accumulator line  842 , an accumulator-to-left-valve line  844 , an accumulator-to-right-valve line  846 ), a left control valve  850 , and a right control valve  860 . While these components are listed, it is specifically understood that some or all of these may be eliminated or relocated (e.g. to the tractor unit  12 ) and the scope of the present illustrated system. The control system  800  is shown on the exterior  204  of the tub  200 , specifically on the exterior of the web  210  for illustrative purpose only. These components may be enclosed in a housing or somewhere protected on the dump trailer  100  (e.g. inside the pyramid  430 ). The hydraulic pump  810  may be any of a variety of pumps configured to pressurized fluid (specifically liquid and most likely a hydraulic oil). The hydraulic pump  810  only has so much capacity therein, so the pump-to-accumulator line  842  is provided for conveying the pressurized fluid from the hydraulic pump  810  to the accumulator  820  where a variable amount of fluid can be stored. Ideally, this accumulator  820  will be configured so components powered by pressurized fluid therein can be quickly transferred without waiting for the hydraulic pump  810  to do all of the pressurization on-demand (e.g. with about 10 to 50 gallons of hydraulic oil). Rather, the pressurization is completed during a period of time leading up to the call for pressurized fluid. The pressurized fluid may be transfer from the accumulator  820  to the left hydraulic cylinder  700  and the right hydraulic cylinder  750  via lines. In one configuration, a pair of hydraulic lines referred to herein as the accumulator-to-left-valve line  844  and the accumulator-to-right-valve line  846  transfer the fluid to the left control valve  850  and the right control valve  860 , respectively. The control system  800  further includes a left supply line  852  in fluid communication between the left control valve  850  and the left hydraulic cylinder  700 . The control system  800  further includes a right supply line  862  in fluid communication between the right control valve  860  and the right hydraulic cylinder  750 . While one line of fluid communication is described to each of the hydraulic cylinders, it is understood that some types of hydraulic cylinders are configured with bi-directional operation characteristics that require two separate supply lines for providing fluid to act on opposite sides of pistons in the hydraulic cylinders. If require, a bi-directional configuration could be implemented in a similar manner as previously described. 
     With further reference to  FIG.  25   , the controller  830  of the control system  800  may be provided with a means for sensing orientation of the tub  200 . While a large variety of mechanism exist for sensing orientation, one mechanism is an accelerometer  832  capable of providing side-to-side angle of the tub  200  (gravitational force of earth, e.g. plumb/true). The accelerometer  832  may be configured with other sensors such as an angle-of-inclination of the tub  200  that reports back the current angle of the tub  200 . While less likely to be utilized, the accelerometer  832  may be configured with a third-axis of reported angle which is referred to herein as a directional reading. The controller  830  is further provided with an electrical supply line  834  to transfer power to the hydraulic pump  810 . The electrical supply line  834  is capable of transferring power sourced from the tractor unit  12  to the hydraulic pump  810  when there is a need for increasing pressure of the fluid. Additionally, the controller  830  is provided with a power lead  836  capable of sourcing the power from an on-trailer power supply (e.g. a battery or a generator) or directly from the tractor unit  12 . Briefly summarized, during normal operation, power is delivered from the tractor unit  12  via the cable assembly  110  through the power lead  836  through the controller  830  and to the hydraulic pump  810  via the electrical supply line  834 . Fluid is pressurized by the hydraulic pump  810  and transferred to the accumulator  820  via the pump-to-accumulator line  842  where it further travels to the left hydraulic cylinder  700  via the left supply line  852 , the left control valve  850 , and the accumulator-to-left-valve line  844 . In a similar manner, the fluid travels to the right hydraulic cylinder  750  via the right supply line  862 , the right control valve  860 , and the accumulator-to-right-valve line  846 . In some situations, the operation of the left hydraulic cylinder  700  and the right hydraulic cylinder  750  are synchronized (wherein the displacement and speed are matched). In other situations, the operation of the left hydraulic cylinder  700  and the right hydraulic cylinder  750  are independent (e.g. when loose-fill ground is located at a site and the accelerometer  832  senses and reports an angle-change to the controller  830 ). 
     With continued reference to  FIG.  25   , the draft arm assembly  600  is attached to the tub  200  as illustrated by a pivot rod  602  capturing the distal tube  642  of the distal hinge  640  (both  FIG.  19   ). This capturing enables the draft arm assembly  600  to be rotatingly attached to the tub  200  about the center axis  270  ( FIG.  6   ) because the draft arm distal axis  644  ( FIGS.  19  and  20   ) is coaxial to the center axis  270 . This positions the draft arm assembly  600  between the center-right hinge  274  and the center-left hinge  272  (both  FIG.  6   ). 
     With reference to  FIG.  26    showing a side perspective view of the semi-trailer truck  10 , the draft arm assembly  600  is attached to the coupling plate  500  by a control pin  506  as illustrated. This attachment results in the proximal end  620  of the draft arm assembly  600  being attached to the coupling plate  500  between the left side  512  and the right side  514  of the coupling plate  500 . The control pin  506  passes through the left hole  520  ( FIG.  17   ) and the right hole  522  ( FIG.  17   ) to create a hinge coaxial to the coupling axis  530  about which the draft arm assembly  600  is rotationally attached via the proximal hinge  630  (of the draft arm assembly  600 ). This places the draft arm proximal axis  634  ( FIG.  20   ) coaxial to thee coupling axis  530 . It is important to note that in the transportation condition best illustrated in  FIG.  2   , the draft arm assembly  600  is positioned to be slightly non-parallel to the ground  20 . With reference to  FIG.  2   , the draft arm assembly  600  intersects a ground plane of the ground  20  at draft arm angle  604  that is configured to always cause the linkage of the draft arm assembly  600  to move the closed end  206  of the tub  200  away from the ground  20 . If the draft arm angle  604  was zero or slightly negative, the tub  200  would rotate towards ground  20  and therefore be inoperable. Therefore, the draft arm distal axis  644  (which is also coaxial to the center axis  270 ) is slightly ‘above’ the draft arm proximal axis  634  (which is also coaxial to the coupling axis  530 ) because any other orientation that places the draft arm distal axis  644  at the same level or slightly below the draft arm proximal axis  634  would bind the mechanism and it wouldn&#39;t function as intended. In other words, the draft arm  604  is non-parallel to the ground (and/or a plane defined by the coupling plate). 
     With reference again to  FIG.  26   , the hole  716  formed in the cap end head  712  of the body  710  on the left hydraulic cylinder  700  is captured by the control pin  506 . This results in the left hydraulic cylinder  700  being rotatingly coupled to the coupling plate  500  about the coupling axis  530  (and the coaxial proximal hinge axis  702 ,  FIG.  22   ). The draft arm assembly  600  may, typically, be oriented at the midpoint of the control pin  506  while the left hydraulic cylinder  700  is oriented by the left side  512  of the coupling plate  500 . As further illustrated in  FIG.  26   , the hole  766  ( FIG.  24   ) formed in the cap end head  762  of the body  760  on the right hydraulic cylinder  750  is captured by the control pin  506 . This results in the right hydraulic cylinder  750  being rotatingly coupled to the coupling plate  500  about the coupling axis  530  (and the coaxial proximal hinge axis  752 ,  FIG.  24   ). The draft arm assembly  600  may, typically, be oriented at the midpoint of the control pin  506  while the right hydraulic cylinder  750  is oriented by the right side  514  of the coupling plate  500 . The hole  776  ( FIG.  24   ) formed on the attachment hinge  774  positioned on the piston rod  770  of the right hydraulic cylinder  750  is adjacent to and coaxial with the right hinge  252  formed on the tub  200 . This place the distal hinge axis  754  ( FIG.  24   ) coaxial with the hinge axis  260  ( FIG.  6   ) whereby the right hydraulic cylinder  750  is rotatingly attached to the tub  200 . 
     With reference to  FIG.  27    showing a front left side perspective view of the semi-trailer truck  10 , the left hydraulic cylinder  700  is rotatingly attached to the tub  200  via the hole  726  formed on the attachment hinge  724  positioned on the piston rod  720  of the left hydraulic cylinder  700 . This orientation results in the left hinge  250  formed on the tub  200  being adjacent to and coaxial with the hole  726 . This place the distal hinge axis  704  ( FIG.  22   ) coaxial with the hinge axis  260  ( FIG.  6   ) whereby the left hydraulic cylinder  700  is rotatingly attached to the tub  200 . 
     With reference to  FIG.  28    showing a side elevation view of the semi-trailer truck  10  with the movement from the transporting condition to the dumping condition, the control system  800  implements a process for controlling expansion of the left hydraulic cylinder  700  and the right hydraulic cylinder  750  to cause the closed end  206  of the tub  200  to move away from ground  20  in a controlled and improved manner. To enable this controlled expansion, the control system  800  senses any subpar conditions that may lead to a rollover condition and/or a probability of a rollover event. In response to sensing, the control system  800  may be pre-programmed to take any of a number of actions such as, for example: moving the semi-trailer truck  10  forward or backwards; slowly lowering either or both of the left hydraulic cylinder  700  and right hydraulic cylinder  750 ; quickly lowering either or both of the left hydraulic cylinder  700  and right hydraulic cylinder  750 ; slowly raising either or both of the left hydraulic cylinder  700  and right hydraulic cylinder  750 ; quickly raising either or both of the left hydraulic cylinder  700  and right hydraulic cylinder  750 ; or other actions implied and feasibly but not specifically described herein. If the left hydraulic cylinder  700  is operated separately from the right hydraulic cylinder  750 , the tub  200  is shifted to cause asymmetrical movement of the left spring assembly  350  and right spring assembly  390  of the rear assembly  300  (all shown in  FIG.  8   ) to cause changes of the left deflection distance  380  and left deflection distance  420  (both shown in  FIG.  16   ). 
     By operating the left hydraulic cylinder  700  and right hydraulic cylinder  750  independently, the control system  800  can greatly improve the safety and therefore speed of the dumping condition. In accomplishing this, the system improves the speed of movement of load(s) from a first location to a second location (where the dumping event occurs). 
     In one alternative configuration, the dump trailer  100  may be provided with linear measurement equipment on the on left hydraulic cylinder  700  and/or the right hydraulic cylinder  750 . Examples of linear measurement equipment include, for example: laser, friction wheel, linear encoder, etc. This measurement equipment may provide a feedback loop to the control system  800  for ensuring that the system is properly operating as intended and nothing is malfunctioning (due to normal wear, adverse operation, and/or improper use of the dump trailer  100 ). 
     In one alternative configuration, the accelerometer  832  can be on a main circuit board of the controller  830 . Alternatively, the accelerometer  832  may be mounted at a different location and in communication with the control system  800  either wired or wirelessly. Furthermore, the accelerometer  832  may be similar to Freescale&#39;s MMA8452Q which is low-power, three-axis, capacitive micro-machined accelerometer with 12 bits of resolution. The accelerometer  832  is able to sense orientation or motion and to report it back to a microcontroller (for example) via a standard communication protocol (e.g. I2C, SPI). 
     In one alternative configuration, a mobile device and/or an application running on a device can track the efficacy of the dumping event. This application can measure, track and ranking the safety record of the site, the truck, the operator of the truck individually and statistically. The application can report this safety record to at least one of the following to a regulatory body, a truck owner, and/or an insurance company. The dump trailer  100  may include a control system with an application based interface such as a mobile device (e.g. cellphone, tablet, portable media player, radio deck with interface features, etc). In this alternative configuration, the phone provides metrics about the quality-of-safety for the transportation process (including, for example, the loading and unloading processes). The device that the application is running on may include a spectrum chip operable with the control system for communicating under various protocols (e.g. Bluetooth, WiFi, cellular, 5G, 4G, CDMA, GSM, etc) to 
     In one alternative configuration, the rear assembly  300  may be configured with a single axle having at least a pair of left and right wheels. The springs can be coil-over springs or special tires capable of deflecting may be utilized in replacement of the more complex configuration of  FIG.  8   . 
     In one alternative configuration, the left wall, right wall and web of the tub  200  can be formed from out of single sheet of material (either folded and welded, pieced together, or slip-rolled if a circumferential profile). 
     In one alternative configuration, the control system  800  may be positioned inside the pyramid  430  where it is protected from debris and impact. 
     In one alternative configuration, the rear assembly  300  may be configured with a single axle having at least a pair of wheels and air springs that replace the more complex spring assembly. 
     While the above description includes terms such as top, bottom, left, right, inside, outside, front, back, and other descriptors regarding physical orientation and/or position, it is to be understood that these are provided for illustrative purposes only. However, the present description was provided to convey to one skilled in the art. 
     As used herein, the terms symmetrical, symmetrically, symmetrically disposed and variants similar to these is to be construed as generally a mirror copy about a central plane. 
     While the principles of the disclosure have been described above in connection with the specific apparatuses and methods, it is to be understood that this description is made only by way of example and not as limitation on the scope of the disclosure. 
     VARIOUS NOTES AND EXAMPLES 
     Example 1 is a dump trailer for a semi-trailer truck comprising: a tub, defining an exterior portion, comprising: a web; a left wall adjoining the web; a right wall adjoining the web and symmetrical to the left wall; a closed end adjoining the web, left wall, and right wall; an open end oppositely disposed from the closed end and adjoining the web, left wall, and right wall; a hinge axis parallel to and offset from the web; a left hinge formed on the exterior portion of the left wall and coaxial with the hinge axis; a right hinge formed on the exterior portion of the right wall and coaxial with the hinge axis; a distal draft arm axis parallel and adjacent to the web, the distal draft arm axis formed on the exterior portion of the web; and a center hinge formed on the web and coaxial with the distal draft arm axis, the center hinge symmetrically disposed between the left wall and the right wall; a coupling plate to engage the dump trailer to the semi-trailer truck, comprising: a hydraulic cylinder axis formed on the coupling plate; a left hydraulic cylinder hinge formed on the coupling plate and coaxial with the hydraulic cylinder axis; a right hydraulic cylinder hinge formed on the coupling plate and coaxial with the hydraulic cylinder axis; a proximal draft arm axis formed on the coupling plate; and a draft arm hinge formed on the coupling plate and coaxial with the draft arm axis, the draft arm hinge symmetrically disposed between the left hydraulic cylinder hinge and the left hydraulic cylinder hinge; a draft arm symmetrically disposed between the left wall and the right wall of the tub, the draft arm comprising: a proximal end attached to the draft arm hinge of the coupling plate and rotationally attached to the coupling plate about the proximal draft arm axis; and a distal end oppositely disposed from the proximal end, attached to the center hinge of the tub, and rotationally attached to the tub about the distal draft arm axis; a left hydraulic cylinder defining a left cylinder length, the left hydraulic cylinder comprising: a proximal end attached to the left hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the left hinge on the tub; and wherein addition of a first amount of fluid changes the left cylinder length; a right hydraulic cylinder defining a right cylinder length, the right hydraulic cylinder comprising: a proximal end attached to the right hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the right hinge on the tub; and wherein addition of a second amount of fluid changes the right cylinder length; a rear assembly pivotally attached to the tub at the web adjacent to the open end, the rear assembly comprising: a first pair of wheels; and a rear pivot around which the tub rotates; whereby increase in both left cylinder length and right cylinder length cause: the distal end of the draft arm to move away from earth; and the tub to rotate about the rear pivot. 
     In Example 2, the subject matter of Example 1 optionally includes and further comprising: a coupling plane that is parallel to the coupling plate; a draft arm plane that is coplanar to the draft arm, wherein the proximal draft arm axis and distal draft arm axis reside in the draft arm plane; and wherein the coupling plane and the draft arm plane are non-parallel. 
     In Example 3, the subject matter of any one or more of Examples 1-2 optionally include wherein: the left hydraulic cylinder comprises: a left bore cylinder at the proximal end, the left bore cylinder attached to the left hydraulic cylinder hinge; a left rod slidingly coupled to the left bore cylinder, the left rod attached to the left hinge on the tub; and wherein addition of the first amount of fluid ejects the left rod from the left bore cylinder; the right hydraulic cylinder comprises: a right bore cylinder at the proximal end, the right bore cylinder attached to the right hydraulic cylinder hinge; a right rod slidingly coupled to the right bore cylinder, the right rod attached to the right hinge on the tub; and wherein addition of the second amount of fluid ejects the right rod from the right bore cylinder. 
     In Example 4, the subject matter of any one or more of Examples 1-3 optionally include wherein the hydraulic cylinder axis and the proximal draft arm axis are coaxial. 
     In Example 5, the subject matter of any one or more of Examples 1-4 optionally include wherein the hinge axis is formed through the left wall and the right wall. 
     In Example 6, the subject matter of Example 5 optionally includes and further comprising: a topside formed on the tub; wherein the left hydraulic cylinder hinge is formed on the left wall adjoining the topside of the tub; and wherein the right hydraulic cylinder hinge is formed on the right wall adjoining the topside of the tub. 
     In Example 7, the subject matter of any one or more of Examples 1-6 optionally include and further comprising: a hydraulic pump attached to the dump trailer; an accumulator in fluid communication with the hydraulic pump and attached to the dump trailer; a left hydraulic valve in fluid communication with the left hydraulic cylinder; a right hydraulic valve in fluid communication with the right hydraulic cylinder; a controller in communication with the left hydraulic valve and the right hydraulic valve; an electric power supply line in electrical communication with semi-trailer truck and the hydraulic pump; whereby power from semi-trailer truck is transferred to the hydraulic pump for pressurizing an amount of hydraulic fluid; whereby at least a portion of the hydraulic fluid is transferred to the right hydraulic cylinder via the right hydraulic valve and the accumulator; and whereby at least a portion of the hydraulic fluid is transferred to the left hydraulic cylinder via the left hydraulic valve and the accumulator. 
     In Example 8, the subject matter of any one or more of Examples 1-7 optionally include and further comprising: a center plane formed on the tub, wherein the center plane is symmetrically located between the left wall and the right wall; a chassis plane formed on semi-trailer truck, wherein the chassis plane is defined by at least two axles of the semi-trailer truck that are coplanar to the chassis plane; a perpendicular condition wherein: the center plane of the tub is perpendicular to the chassis plane; and the left cylinder length and the right cylinder length are equal; a canted condition wherein: the center plane is non-perpendicular to the chassis plane; and the right cylinder length and the right cylinder length are different. 
     In Example 9, the subject matter of any one or more of Examples 1-8 optionally include wherein the rear assembly further comprises: a second pair of wheels parallel to the first pair of wheels; a spring assembly comprising: at least one leaf spring comprising first end and a second end; a first axle attachment on the first end; a second axle attachment on the second end; and a hinge symmetrically attached between the first end and the second end of the leaf spring; wherein the first pair of wheels are attached to the first axle attachment with a first axle; wherein the second pair of wheels are attached to the second axle attachment with a second axle; and wherein the rear pivot about which the tub rotates is coaxial with a hinge assembly. 
     Example 10 is a method of controlling unloading of a dump trailer comprising: providing a tub, defining an exterior portion, comprising: a web; a left wall adjoining the web; a right wall adjoining the web and symmetrical to the left wall; a closed end adjoining the web, left wall, and right wall; an open end: oppositely disposed from the closed end; and, adjoining the web, left wall, and right wall; a hinge axis formed through the left wall and the right wall; a left hinge formed on the exterior portion of the left wall and coaxial with the hinge axis; a right hinge formed on the exterior portion of the right wall and coaxial with the hinge axis; a distal draft arm axis adjacent to the web and on the exterior portion of the web; a center hinge formed on the web and coaxial with the distal draft arm axis; and a center plane symmetrically disposed between the left wall and the right wall; providing a coupling plate, configured to engage the dump trailer to semi-trailer truck, comprising: a hydraulic cylinder axis formed on the coupling plate; a left hydraulic cylinder hinge: formed on the coupling plate; and coaxial with the hydraulic cylinder axis; a right hydraulic cylinder hinge: formed on the coupling plate; and coaxial with the hydraulic cylinder axis; a proximal draft arm axis formed on the coupling plate; and a draft arm hinge: formed on the coupling plate; and coaxial with the draft arm axis; providing a draft arm, symmetrically disposed between the left wall and the right wall of the tub, comprising: a proximal end rotationally attached to the coupling plate about the proximal draft arm axis; and a distal end: oppositely disposed from the proximal end; attached to the center hinge; and whereby the draft arm is rotationally attached to the tub about the distal draft arm axis; providing a left hydraulic cylinder, defining a left cylinder length, comprising: a proximal end attached to the left hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the left hinge on the tub; and wherein addition of a first amount of fluid changes the left cylinder length; providing a right hydraulic cylinder, defining a right cylinder length, comprising: a proximal end attached to the right hydraulic cylinder hinge; a distal end oppositely disposed from the proximal end and attached to the right hinge on the tub; and wherein addition of a second amount of fluid changes the right cylinder length; providing a rear assembly attached to the tub adjoining the web and adjacent to the open end, the rear assembly comprising: a first pair of wheels; and a rear pivot about which the tub rotates; a second pair of wheels parallel to the first pair of wheels; a spring assembly comprising: at least one leaf spring comprising first end and a second end; a first axle attachment on the first end; a second axle attachment on the second end; and a hinge symmetrically attached between the first end and the second end of the leaf spring; wherein the first pair of wheels are attached to the first axle attachment with a first axle; wherein the second pair of wheel are attached to the second axle attachment with a second axle; and wherein the rear pivot about which the tub rotates is coaxial with the hinge of the rear assembly; increasing in both the left cylinder length and the right cylinder length: moves the distal end of the draft arm to away from earth; and rotates the tub about the rear pivot; monitoring perpendicularity of the center plane; increasing either the left cylinder length or the right cylinder length to compress the leaf spring in the spring assembly; and thereby controlling the unloading of the dump trailer. 
     In Example 11, the subject matter of Example 10 optionally includes and further comprising: providing: a hydraulic pump attached to the dump trailer; an accumulator in fluid communication with the hydraulic pump and attached to the dump trailer; a left hydraulic valve in fluid communication with the left hydraulic cylinder; a right hydraulic valve in fluid communication with the right hydraulic cylinder; a controller in communication with the left hydraulic valve and the right hydraulic valve; an electric power supply line in electrical communication with semi-trailer truck and the hydraulic pump; transferring power from semi-trailer truck to the hydraulic pump; pressurizing an amount of hydraulic fluid with the hydraulic pump; whereby during the monitoring perpendicularity, the controller independently controls the left hydraulic valve and the right hydraulic valve; and thereby controlling unloading of the dump trailer. 
     Example 12 is a dump trailer for a semi-trailer truck comprising: a chassis plane formed on semi-trailer truck, wherein the chassis plane is defined by at least two axles of the semi-trailer truck that are coplanar to the chassis plane; a tub, comprising: a web; a left side adjoining the web; a right side adjoining the web; and a center plane formed on the tub, wherein the center plane is symmetrically located between the left wall and the right wall; a draft arm symmetrically disposed between the left side and the right side of the tub, the draft arm comprising: a proximal end; and a distal end oppositely disposed from the proximal end, rotationally attached to the web of the tub; a coupling plate to engage the dump trailer to the semi-trailer truck, wherein: the proximal end of the draft arm is rotationally attached to the coupling plate; a left hydraulic cylinder defining a left cylinder length, the left hydraulic cylinder comprising: a proximal end rotationally attached to the coupling plate; and a distal end oppositely disposed from the proximal end and rotationally attached to the tub; a right hydraulic cylinder defining a right cylinder length, the right hydraulic cylinder comprising: a proximal end rotationally attached to the coupling plate; and a distal end oppositely disposed from the proximal end and rotationally attached to the tub; a rear assembly pivotally attached to the tub at the web, the rear assembly comprising: a first pair of wheels; and a rear pivot around which the tub rotates; a perpendicular condition wherein: the center plane of the tub is perpendicular to the chassis plane; and the left cylinder length and the right cylinder length are equal; a canted condition wherein: the center plane is non-perpendicular to the chassis plane; and the right cylinder length and the right cylinder length are different. 
     In Example 13, the subject matter of Example 12 optionally includes wherein the draft arm and the coupling plane are non-parallel. 
     In Example 14, the subject matter of any one or more of Examples 12-13 optionally include wherein: the left hydraulic cylinder comprises: a left bore cylinder rotationally attached to coupling plate; and a left rod slidingly coupled to the left bore cylinder, the left rod rotationally attached to the left side of the tub; the right hydraulic cylinder comprises: a right bore cylinder rotationally attached to the coupling plate; and a right rod slidingly coupled to the right bore cylinder, the right rod rotationally attached to the right side on the tub. 
     In Example 15, the subject matter of Example 14 optionally includes and further comprising: a topside formed on the tub; wherein the left rod of the left hydraulic cylinder is adjoining the topside of the tub; and wherein the right rod of the right hydraulic cylinder is adjoining the topside of the tub. 
     In Example 16, the subject matter of any one or more of Examples 12-15 optionally include wherein the left hydraulic cylinder, the right hydraulic cylinder; and the proximal end of the draft arm are rotationally attached to the coupling plate along a common axis of rotation. 
     In Example 17, the subject matter of any one or more of Examples 12-16 optionally include and further comprising: a hydraulic pump attached to the dump trailer; an accumulator in fluid communication with the hydraulic pump and attached to the dump trailer; a left hydraulic valve in fluid communication with the left hydraulic cylinder; a right hydraulic valve in fluid communication with the right hydraulic cylinder; a controller in communication with the left hydraulic valve and the right hydraulic valve; an electric power supply line in electrical communication with semi-trailer truck and the hydraulic pump; whereby power from semi-trailer truck is transferred to the hydraulic pump for pressurizing an amount of hydraulic fluid; whereby at least a portion of the hydraulic fluid is transferred to the right hydraulic cylinder via the right hydraulic valve and the accumulator; and whereby at least a portion of the hydraulic fluid is transferred to the left hydraulic cylinder via the left hydraulic valve and the accumulator. 
     In Example 18, the subject matter of Example 17 optionally includes and further comprising: an accelerometer attached to the dump trailer configured to sense orientation of the center plane; wherein the accelerometer is in communication with the controller; and a set of instructions implemented by the controller to change the right cylinder length and the left cylinder length. 
     In Example 19, the subject matter of Example 18 optionally includes wherein the accelerometer is attached to the web of the tub.