EP0144780B1

EP0144780B1 - Frameless radial truck

Info

Publication number: EP0144780B1
Application number: EP84113436A
Authority: EP
Inventors: Robert L. Bullock
Original assignee: Standard Research and Design Corp
Current assignee: Standard Research and Design Corp
Priority date: 1983-12-02
Filing date: 1984-11-07
Publication date: 1988-04-20
Also published as: BR8406103A; AU3537784A; EP0144780A1; CA1234722A; DE3470501D1; IN161368B; AU558884B2; ZA848234B

Description

The invention refers to radial wheeled support vehicles for a railroad car body. Such a vehicle is shown in DE-A-32 32 289. The known vehicle is of the conventional three-piece concept of two sideframes and a bolster to form the frame for the truck and to form a means whereby the car body is supported on the truck. The known vehicle is also self-steering and includes a pair of wheelsets. The sideframes are supported on the wheelset, connecting adjacent ends of each wheelset. The connection between the sideframe and the wheelset contains resilient means which allow yaw and lateral movement of the wheelsets. A cross-beam is supported on each sideframe by means of friction wedges connecting the sideframes to each other. Since the sideframes are not able to sufficiently prevent the. wheelsets from a longitudinal movement, adjacent ends of the wheelsets are connected additionally by a linkage. The linkage is said not to influence negatively lateral movement and yaw of the wheelsets, however it is not able to constrain the wheelsets to yaw in opposite sense. Due to the necessarily rigid design of the sideframes, vehicles of such type are very heavy.
DE-B-11 84372 discloses a wheel suspension which may be mounted individually to the car body, or which may be used in a bogey. At each end of the wheel, a support is mounted by resilient means. For an individual mounting of the wheel to the car body, each support is directly and fixedly connected to the car body. It does not, however, disclose how and where the support is mounted when in use in a bogey having two wheelsets. Furthermore, nothing is disclosed concerning how to connect the wheelsets to each other for yaw and lateral movement and for preventing longitudinal movement.
It is therefore an object of the present invention to provide a self-steering radial wheeled support vehicle for a railroad car body, including a pair of wheelsets, which is lightweight and thus increase the load capability and provide substantial fuel economy.
The term "radial truck" has been used in the railroad industry to designate a railway support vehicle or truck or bogey which is essentially self-steering or which can follow the radius of curvature of most curves found in conventional railway usage.
The present invention is defined in claim 1 and is concerned with a radial truck in which the bolster and sideframes have been eliminated, with very substantial savings in weight for each railroad car. Specifically, by eliminating the bolster and sideframes conventionally found in most railroad bogies, there is a reduction in weight of approximately 2270 kg (5000 lbs) per car. By eliminating the bolster and sideframes, changes in the support structure of the car body can be made which will eliminate an additional 1362 kg (3000 lbs) of weight per car. Accordingly, the frameless radial truck of the present invention can provide a railroad car weighing in the area of 3632 kg (8000 lbs) less than previous cars suitable for the same traffic. This reduction in weight not only permits the car to carry a greater load, but also provides substantial fuel economies in running unloaded cars.
Elimination of the sideframes and bolster, however, presents many design problems since these elements provide the means whereby the car body is supported on the truck and they provide the basic frame whereby the truck is self-steering and through which constraints are placed on the lateral and yaw movements of the wheelsets during self-steering. Specifically, the present invention provides a frameless radial self-steering support vehicle for a railroad car environment in which the bolster and sideframes have been eliminated; in which the car body is independently supported on each end of each wheelset; in which there are resilient shear pads constraining both lateral and yaw movements of the wheelsets relative to the car body; and in which there is a connecting linkage between adjacent ends of each wheelsets, which linkage constrains the wheelsets to yaw in opposite sense while permitting lateral movement of one wheelset relative to the other and which further contains the wheelsets from net longitudinal movement with respect to each other.
The invention is illustrated diagrammatically in the following drawings wherein:

Figure 1 is a partial top plan view of a railway vehicle of the type described,
Figure 2 is a side view of the railway vehicle disclosed herein,
Figure 3 is a partial section taken along place 3-3 of Figure 2, and
Figure 4 is a diagram illustrating lateral deflection vs. lateral shear force per wheelset for the railway vehicle disclosed herein.

A pair of spaced conventional wheelsets are indicated at 10 and 12, there being a wheel 14 attached on the illustrated end of each wheelset. It is understood that the top plan view of Figure 1 only shows a portion of the truck and that the wheelsets will continue with identical struction, not shown, on the opposite side of each truck or vehicle. Wheels 14 may be of conventional conicity or may have a special profile. It is preferred to use a profile similar to that of a worn wheel which has a high effective conicity with approximately a 1.27 cm (0.5 inch) flange clearance with the rail and a high flange contact angle. Such a conicity has a profile quite similar to that of a naturally worn wheel.
Each of the wheelsets 10 and 12 will have a roller bearing 16 at each end of the wheelset and each roller bearing 16 will support a roller bearing adapter 18. Mounted upon each roller bearing adapter 18 is a plurality of resilient shear pads indicated generally at 20. There may be a single shear pad, although it is preferred that there be multiple or a plurality of shear pads, as illustrated. The pads will be of similar size and shape and will be separated by metal plates, as is conventional. Shear pads 20 should be formed of a material which will provide a predetermined amount of damping within the material of the pads of not less than ten percent of critical damping in order to provide adequate car body stability under loaded car conditions.
The shear pads support a pedestal indicated generally at 24. Pedestal 24 has a bottom portion 26, upstanding side walls 28 and a top portion 30 which is seated upon shear pad 20. In effect, walls 28 and 30 form a small housing which not only is supported upon the shear pad, but restricts the amount of lateral and yaw movement between the wheelset and the pedestal. As particularly illustrated in Figure 2, there are gaps between adapter 18 and housing walls 28. These gaps permit yaw movement of the wheel set in an amount equal to the longitudinal clearance which, in the preferred embodiment, may be on the order of 3.2 cm (one and one-quarter inch). Adapter 18 has upstanding inboard and outboard ears 27 and 29 respectively which cooperate with top wall portion 30 to permit a similar amount of lateral movement of the wheelset relative to the pedestal. This amount of movement may be on the order of 2.54 cm (an inch) in each lateral direction. Thus, when considering the relationship between the wheelset, its roller bearing adapters, the supporting resilient shear pads 20 and the pedestals 24 which are mounted upon the wheelset by the shear pads, the wheelsets have a permitted yaw and lateral displacement relative to the pedestals or the support structure.
Each pedestal includes, as a part of bottom member 26, an outside platform 32 at one side of the bottom member and an inside platform 34 at the opposite side. Each of the platforms 32 and 34 mount springs 36 which are similar to conventional load bearing or load carrying springs normally found between the side frame and bolster of a car truck. Springs 36 support the weight of the car body on the pedestal and thus the wheelsets. In addition to springs 36, there are smaller damping springs 38 supported on the platforms, which damping springs 38 each support a friction wedge or damping member 40. Wedges 40 bear against wear plates 42 mounted on the outside of walls 28, much in the manner of a conventional three-piece truck. The wedges or friction members fit within pockets 44 formed in a wheelset frame member 46 which extends over the top of the roller bearing adapter, shear pads and pedestal top member 30 and had downwardly facing seat areas 48 at opposite sides thereof which form the upper seat for springs 36. Thus, wheelset frame members 46 are supported on springs 36 and in turn will support the car body, as described. There is only a small, about 0.32 cm (one-eighth inch), lateral clearance between frame member 46 and side walls 28 and the side flanges of the frame member are in contact with plate 42.
Formed at opposite sides of each wheelset frame member 46 is an upper platform 50 which has a generally horizontal portion and an upwardly slanted portion. Positioned on each platform 50 is a resilient shear pad construction 52, which again may be a single shear pad of a plurality of shear pads, although the latter is preferred. Shear pad constructions 52 each include shear pads with a horizontal portion 54 and an upwardly directed or slanted portion 56. The shear pads fit within the contour defined by platforms 50 and support on the upper ends thereof a friction member or wedge 58, specifically illustrated in Figures 2 and 3.
Wedge members 58, which may be formed of the same metallurgical composition as friction wedges 40, seat upon the shear pads as described and have an upper wedge-shaped nose 60 which extends within a similar wedge-shaped pocket 62 of a wedge cover 63 which is attached to car body 64. Wedges 58, there being two such wedges at each end of each wheelset, independently support the car body upon the wheelsets. The car body wedge covers 63 maintain the wedges in position within the pockets and resting upon the shear pad construction. Each of the wedge members 58 has a slope on the opposite surface from that in contact with the upward slanted portion 56 of the shear pad. The sloping surface, indicated at 57, has approximately the same direction or is generally parallel to the slanted surface of shear pad portion 56. Sloping or slanted surfaces 57 further have a crown or slight radius in the slanted direction as will be explained in detail hereinafter.
Adjacent ends of wheelsets 10 and 12 are pivotally connected together. Pedestals 24, specifically the inboard platforms thereof, indicated at 34, each pivotally support a bearing housing 70 which includes a bearing member 72 having an internal pillow block 74. The pivotal connection, which may be a pin and slot configuration 71, preferably allows for lateral deflection of the pedestal of one wheel set with respect to the other by permitting rotational and longitudinal movement. Pillow blocks 74, at opposite sides of the bogey, support a torque rod or tube 76 extending from one side of the vehicle to the other. Positioned on the outboard ends of torque rod 76 and at each end thereof is a clevis 78, particularly illustrated in Figure 2. One side of clevis 78 is pivotally attached to a rod 80, with the opposite end of the rod being pivotally attached to a roller bearing adapter 18. In like manner, a rod 82 is pivotally attached to the other side of clevis 78 and is pivotally attached to the roller bearing adapter of the other wheelset. Opposite ends of rods 80 and 82 include resilient bushings 80a and 82a as a part of each pivotal connection to provide a degree of yaw freedom with respect to the roller bearing adapter and clevis for lateral deflection of the wheel sets.
It is important to note that rods 80 and 82 are each pivotally attached to the upper portion or top of the roller bearing adapters, but are attached to the bottom and top of clevis 78. At the opposite end of the torque tube the connections to the clevis will be in the reverse sense. That is, the connection from wheelset 12 will be to the top of the clevis and the connection from wheelset 10 will be to the bottom of the clevis.
Although not shown, damping members, conventionally a small piston and cylinder with attached rods, may be connected between the pivotal connections of the clevis and the pivotal connections with the roller bearing adapters to damp any oscillatory movement brought about during yaw of the wheelsets. The damping members would be useful in preventing truck hunting.
The truck described herein permits constrained relative yaw movement between the wheelsets as would be brought about when the car enters curved track. In like manner, during the period when a car is negotiating a curve, there may be a required lateral deflection of each wheelset relative to the car body to permit the wheels to stay in position upon the rails. When the railroad vehicle enters a curved track, wheelsets 10 and 12 will yaw to assume a radial configuration relative to the radius of curvature of the track. Shear pads 20, which are positioned between the roller bearing adapters and the support pedestals, will permit the degree of yaw necessary to negotiate approximately an eight-degree railroad track curve. As indicated above, there is 3.2 cm (an inch-and-a-quarter) of space on each side of adapter 18 to accordingly permit yaw movement of that degree between the roller bearing adapter and the supporting pedestal. The wheelsets are connected together and rods 80 and 82 will not interfere with the natural yaw movement of wheelsets having a high effective conicity. When wheelsets of lower conicity are used, the rods will constrain yaw movement of the wheelsets. As wheelsets 10 and 12 move together at the end shown in Figure 1, rods 80 and 82 will cause torque tube 76 to rotate in a clockwise direction. The opposite ends of the wheelsets would move apart. And since the connections of the corresponding rods are opposite to those illustrated in Figure 2, this would impart the same clockwise turning movement to torque tube 76. Thus, the torque tube has no torsional movement or stress applied to it during conventional yaw movement. Shear pads 20 will permit a degree of yaw movement consistent with negotiating an approximately eight-degree curve. Once the roller bearing adapter has contacted sides 28 of the pedestal, brought about by yaw movement as described, resistance to further yaw movement will be taken up by the diagonal or upwardly slanted portions of shear pads 52 and wedges 58 which support the car body on the ends of the wheelsets.
In addition to yaw, there are lateral forces applied to the wheelsets during curving which require lateral deflection of the wheelsets relative to the car body. Shear pads 20 again will provide an amount of lateral movement consistent with that required-to negotiate an approximate eight-degree curve. If the curve is more severe, the roller bearing adapter ears will contact top member 30 after a predetermined lateral movement. Further efforts at lateral movement by the wheelsets will be accommodated by shear pads 52.
Referring to Figure 4, a curve relating lateral shear deflection and the lateral shear force applied per journal or at one end of a wheelset, the American Association of Railroads (AAR) requires that a car negotiate a 45.72 m (150 ft.) curve before it can have AAR certification. The AAR also requires traversing a ten-degree curve with 90800 kg (200,000 Ibs.) of squeeze applied to the car. This is a substantially more severe test than the eight-degree curvature for which the truck is designed and which will accommodate most railroad use. To successfully run through a 45.72 m (150 ft.) curve and maintain the wheels on the rails, it is necessary that the wheelsets, with the described permitted yaw, have a lateral shear deflection of 12.065 cm (4-3/4 in.) with respect to the car body. In a loaded car, the first 2.54 cm (one inch) of such deflection will be accommodated by shear pads 20, as described. The remaining 9.525 cm (3-3/4 in.) will be accepted by shear pads 52. The two shear pads function in series in that the resistance of a pair of pads 52 does not become effective until the wheelset has moved the permitted deflection of pad 20. The two shear pad constructions, in combination, will permit a lateral wheel set shear deflection of 12.065 (4-3/4 in.) which is required to negotiate the prescribed AAR curve. This is represented by curve 92 of Figure 4.
A light or unloaded car presents different problems. The first 2.54 cm (one inch) of deflection will again be accommodated by shear pads 20. The next 0.635 cm (one-fourth inch) deflection will be accommodated by shear pads 52. However, further lateral deflection between the wheelset and the car body will be accommodated by movement of the car body wedge pocket relative to the wedge specifically illustrated in Figure 3. The lateral forces applied by the rails to the wheelsets will cause the wedges 58 to move within pockets 62. As illustrated in Figure 4, at a predetermined lateral shear force on the unloaded car wheelset the wheelset will deflect the required remaining distance by the described wedge movement. This is illustrated by curve 90.
Wedges 58 and associated pockets 62, the car body shear pads 52 and the wheelsets shear pads 20, individually and in combination, effectively provide for the required 12.065 cm (4-3/4 in.) deflection necessary to negotiate the required AAR curve, under all car loading conditions. The specific wedge configuration is also advantageous in that it assists in restoring the car body and wheelset to the original non-deflected position.
The combination of the slope of shear pad portion 56 and the shape of rear wall wedge surface 57 and the slanted configuration of the wedge pocket prevents the wedge from sliding in the car body wedge pocket under loaded car conditions. For example, such might occur if surface 62 of the wedge pocket becomes contaminated with oil or water, a not uncommon condition in a railroad environment. At loaded car conditions, shear pad 52 will have a preload deflection approximately 1.27 cm (one-half inch), which will cause a predetermined normal force between the slope shear pad and the facing wedge surface. This force will prevent vertical movement between the wedge and the pocket, which in turn will prevent lateral movement between the wedge and pocket at loaded car conditions. At light or unloaded car conditions the sloped or slanted surfaces 62 of the two wedge pockets are spaced in the longitudinal direction such that there is no preload between the wedge and the pocket.
In order to successfully negotiate the required AAR curve, if cross anchors or cross rods were used to connect opposite ends of the wheelsets, as is conventional in radial trucks, it would be necessary to have in the area of 15.24 cm (six inches) of yaw movement at each wheelset. It is impossible to accommodate yaw movement of that degree. Accordingly, the required movement of the wheelset to negotiate the curve is largely taken up by the lateral movement described above. There is still yaw movement; however, it is on the order of the 3.2 cm (one-and-one-quarter inch) of permitted movement described. Because the wheelsets are moving in a lateral direction, the torque tube must be mounted in a pillow block which will permit the torque tube to pivot relative to its mounting. In like manner, housing 70 for opposite ends of the torque tube must be able to pivotally move relative to the wheelset supports to permit the required lateral and yaw movements necessary to move the truck around curves.
Both lateral and yaw movements are required in negotiating curves and the support system for the vehicle permits such movement. The wheelsets are constrained against relatively longitudinal movement, either toward or away from each other, both by the housings 70 and by the torque tube. If the wheelsets are urged longitudinally apart, this movement will be resisted by the torque tube because of the manner in which the rods 80 and 82 are connected to opposite ends of the torque tube. Similarly, loads applied to the support pedestals 24 which might tend to move one of the shear pads out of engagement with the car body support will be resisted by the torque tube supports 70.
When railroad vehicles of the type described are used on unit trains which function with automatic dumpers, a squeezing movement is applied to the truck wheelsets during the dumping operation. Rods 80 and 82 connected, as described, to torque rod 76, not only will accommodate yaw and lateral movements, as described, but are sufficient to resist this substantial squeezing movement. When the truck wheelsets are being held in an automatic dumper locking device, large longitudinal forces are applied to the car body by the forces applied to the train. These forces are transmitted to the locking device through the truck system. In this design, such forces would tend to rotate the pedestal assemblies about roller bearing 16. Such loads applied to the support pedestals which might otherwise tend to move a shear pad out of engagement with the car body support will be resisted by torque tube supports 70.
In a conventional rigid three-piece car truck, hunting is manifested by a pivoting of the entire rigid truck about the center pivot point of connection to the freight car body. In a self-steering truck, without connections between wheelsets, hunting is brought about by oscillation of the individual wheelsets. In a radial frameless car truck system where there is a low yaw constraint between the wheelsets and the frame for curving, hunting stability is acquired by the interconnection of the wheelsets such that they are forced to yaw in an opposite sense with respect to each other. This interconnection between wheelsets must have a predetermined minimum stiffness and, as shown herein, the predetermined minimum stiffness required is the connection between the roller bearing adapter and clevis 78. The stiffness may be provided by the rod, such as rod 80 or 82, which forms the connection, or as is preferred, by the bushing mounted upon the clevis which is a part of the connection. The stiffness of the connection or the spring rate of the material of the bushing must be a predetermined minimum and when the stiffness is below such predetermined minimum, the speed at which hunting occurs drops off dramatically. Similarly, the stiffness cannot be too great or again the speed at which hunting occurs will drop off dramatically. It is preferred that the stiffness of the connection or the resiliency of the connection be provided by the bushing forming a part of the connection rather than the rod, so that the stiffness of the rod alone, after the resiliency permitted by the bushing has bottomed out, can be used in car braking. For example, the combined effective stiffness provided by the resilient bushings at each end of the rod should be not less than 7149.6 kg per cm (40,000 Ibs per inch) to provide good truck hunting stability at unloaded car conditions.
The terms used in Figure 4 are defined as follows:

8° R.R. curve - railroad curves in which the angle between two radii which terminate at points
(10° R.R. curve) 30.48 m (100 ft) apart is 8 (10; 16) degrees; i.e. it is the included angle between
(16° R.R. curve) a segment of a circle having a 30.48 m (100 ft) cord.
Nadal's lateral force - lateral force for a particular car load at which the flange of the wheel will climb the rail, calculated according to equation developed by Nadal.

Claims

1. A frameless self-steering radial wheeled support vehicle for a railroad car body (64) including:

(a) a pair of wheelsets (10, 12),

(b) a support at both ends of each wheelset (10,12) for independently mounting a car body (64) on each end of the wheelsets (10, 12),

(c) resilient means (20, 52) for mounting each support upon a respective end of a wheelset (10, 12), which resilient means (20, 52) permits both lateral and yaw movement of a wheelset (10, 12) relative to its supports, and

(d) a linkage (76, 78, 80, 82) connecting adjacent ends of said pair of wheelsets (10, 12) and constraining the wheelsets (10, 12) to yaw in opposite sense relative to each other, permitting both wheelsets (10, 12) to yaw in the same direction with respect to the car body (64), permitting lateral movement of one wheelset (10, 12) relative to the other, and preventing relative longitudinal movement of the wheelsets (10, 12).

2. The vehicle of claim 1, characterised in that said linkage (76, 78, 80, 82) includes a yaw connection (78, 80, 82) between adjacent ends of each wheelset (10, 12) and a cross vehicle connection (76) between yaw connections (78, 80, 82).

3. The vehicle of claim 1 or 2 further characterised in that each support includes resilient means (52) permitting lateral movement of a wheelset (10, 12) relative to the car body (64).

4. The vehicle of claim 3 further characterised in that said support resilient means includes elastomeric pads (52) positioned on opposite sides of a wheelset axle at each end of a wheelset (10, 12), said pads (52) each having a generally horizontal portion (54) and an upwardly extending portion (56).

5. The vehicle of any of claims 1 to 4 further characterised in that said resilient means (20, 52) for mounting each support include an elastomeric material providing an amount of damping not less than ten percent of critical dampings.

6. The vehicle of any of claims 1 to 5 further characterised in that each support includes a pedestal (24), spring means (36) mounted upon each pedestal (24), with said support resilient means (52) being mounted upon said spring means (36).

7. The vehicle of claim 6 further characterised in that said pedestal (24) is mounted upon said first- named resilient means (20), said spring means (36) being positioned upon opposite sides of a wheelset axle.

8. The vehicle of claim 6 or 7 further characterised by and including damping means (38, 40) mounted upon each pedestal (24) to restrain relative vertical movement between each pedestal (24) and the car body (64).

9. The vehicle of any of claims 1 to 8, characterised in that each support includes frictional resistance means (58, 62) providing for restrained lateral movement of the wheelset (10, 12) relative to the car body (64).

10. The vehicle of claim 9 further characterised in that each of said frictional resistance means includes a wedge-shaped pocket (62) on the underside of the car body (64) and wedge-shaped member (58) extending into the pocket (62) and forming a portion of each support.

11. The vehicle of claim 9 or 10 further characterised in that said frictional resistance means (58, 62) is mounted upon said support resilient means (52).

12. The vehicle of any of claims 10 to 11 further characterised in that each of said wedge-shaped members (58) have a slanted surface away from said slanted elastomeric pad portion (56) and generally parallel thereto which is in engagement with said wedge-shaped pocket (62).

13. The vehicle of any of claims 6 to 12 further characterised by said spring means (36) forming a part of each support and in turn mounting each of said support resilient means (52).

14. The vehicle of any of claims 6 to 13 further characterised in that each of said pedestals (24) extends on opposited sides of each wheelset axle, there being a pedestal (24) at each end of each wheelset (10, 12), each wheelset (10, 12) including a roller bearing (16) positioned at each end thereof and a roller bearing adapter (18) mounted on each roller bearing (16), said resilient means (20) positioning each pedestal (24) upon its associated roller bearing adapter (18).

15. The vehicle of any of claims 6 to 14 further characterised in that said linkage (78, 80, 82) pivotally connects adjacent portions of pedestals (24) at adjacent ends of the wheelsets (10, 12).

16. The vehicle of any of claims 6 to 15 further characterised in that the resilient means (20) positioning each pedestal (24) upon a roller bearing adapter (18) permits relative movement therebetween in both lateral and yaw directions of a predetermined amount.

17. The vehicle of any of claims 2 to 16 further characterised in that said cross vehicle connection includes a torsion member (76) connected between said yaw connections (78, 80, 82) to rotate during yaw movement of the wheelsets (10, 12) and to torsionally resist longitudinal relative movement of the wheelsets (10, 12).

18. The vehicle of claim 17 further characterised in that said roller bearing adapter means (18) are mounted on the end of each wheelset (10, 12) said yaw connections each including a rod (80, 82) pivotally connected to each roller bearing adapter means (18) and pivotally connected together at opposite ends of said torsion member (76).

19. The vehicle of claim 18 further characterised in that the pivotal connections at opposite ends of each rod (80, 82) include means (80a, 82a) permitting yaw movement between each roller bearing adapter means (18) and said torsion member (76).

20. The vehicle of any of claims 17 to 19 further characterised in that opposite ends of said torsion member (76) are pivotally mounted on platform members (70), each platform member (70) being pivotally connected, at opposite ends thereof, to a wheelset support.

21. The vehicle of claim 20 further characterised in that each pivotal connection (71) permits relative rotational and longitudinal movement between each platform member (70) and its associated wheelset supports.

22. The vehicle of any of claims 10 to 21 further characterised in that said frictional resistance means (58, 62), said support resilient means (52) and said wedge-shaped pocket (62) on the underside of the car body (64) receiving the frictional resistance means (58) act together to greatly restrict longitudinal movement of said support while permitting lateral movement of the said support relative to the car body (64).

23. The vehicle of any of claims 8 to 22 further characterised in that said damping means (38, 40) includes a friction wedge (40) mounted upon each pedestal (24), a frame (46) positioned upon said spring means (38) and in contact with said friction wedge (40), said friction wedge (40) greatly restricting longitudinal movement of said pedestal (24) with respect to said frame (46) and the car body (64).