GB2189891A

GB2189891A - Improvements in dynamometers

Info

Publication number: GB2189891A
Application number: GB08610312A
Authority: GB
Inventors: Clive John Burchett
Original assignee: Vickers PLC
Current assignee: Vinters Ltd
Priority date: 1986-04-28
Filing date: 1986-04-28
Publication date: 1987-11-04
Also published as: GB8610312D0

Abstract

In a dynamometer for testing tyres and/or wheels and brakes of aircraft, a tyre 12 in rolling contact with a drum 10 is mounted on a load transducer module 22 connected via mounting plate 24 to thrust plate 30 of a loading head. The camber angle required for the test is set by rotating a lead screw (34, Fig. 3) which has a travelling nut (36, Fig. 3) attached to plate 24 causing plate 24 to move relative to bracket 26. Angled tracks 40, 41 move through linear bearings formed in rotatably mounted bushes 60 so that as the plate 24 translates, its attitude relative to line of action 16 varies. The problem of preventing the centre of load 14 between tyre 12 and drum 10 from moving from its datum position is solved by supporting bushes 60 in arms 56 pivoted to bracket 26 on shafts 54. Control levers (64, Fig. 3) are connected to an adjustment screw 68 that rotates in one direction to converge the arms 56 and in the opposite direction to cause them to diverge. <IMAGE>

Description

SPECIFICATION Improvements in dynamometers The present invention relates to a dynamometer that is of particular advantage for the testing of tyres and brakes of aircraft, though it may also be used to test other vehicle tyres and brakes, and in general for monitoring the acceleration, deceleration or energy tolerance of any moving device intended to be coupled to a vehicle.

The use of a so-called "chassis dynamometer" with inertial weights to measure the acceleration and deceleration performance of an automobile or other vehicle has long been known (see Knudsen R.F., "Inertia Electroni calls", ISA Journal, April 1958, Vol. 5, No. 4, pp 52-54). Further dynamometers are described in Patent Specification Nos GB-A-1297813, 1604320 and 2149520 and in Roberts J.B., "An Advanced High-Speed Dynamometer for Testing Aircraft Tyres, Wheels and Brakes", read before the Applied Mechanics Group of the Institution of Mechanical Engineers on 10th April 1974.

This invention is concerned with a dynamometer of the above general kind in which a test subject is urged towards a rotary drum by means of a loading head and provision is made for maintaining the "footprint" of the test subject on the drum at a datum position irrespective of the size of the test subject over a range of possible camber angles of the test subject.

In one aspect the invention provides a connector assembly for connecting sliding carriage means of an eventual dynamometer loading head with distal portions of the loading head supporting an eventual test subject, comprising a fixed portion for attachment to sliding carriage means of the loading head and a movable portion forming a proximal portion of eventual cantilever arm means whose intended distal portion has support means for the eventual test subject, drive means being operably connected between the fixed and movable portions to move the movable portion transversely of a line of action of the eventual loading head with spaced, mutually-inclined camber tracks on the movable portion being slideable through spaced linear bearing means rotatably supported on the fixed portion to camber the movable portion during said transverse movement, wherein the linear bearing means to opposed sides of the eventual line of action are supported in movable carrier means and second drive means is operably connected to the movable carrier means to set a distance between each movable carrier means and the eventual line of action so that for differently-sized test subjects the point of contact between the test subject and an eventual rotatory dynamometer member can be maintained at a datum position over a range of camber angles.

The present invention also provides a dynamometer comprising a member mounted for rotation and by driving means, loading head means supported for movement towards the member along a line of action and cantilever arm means attached to the loading head means for supporting a test subject in rolling contact with the member, wherein drive means is operably connected between fixed and movable portions of the cantilever arm means to move the movable portion transversely of the line of action with spaced, mutually-inclined camber tracks on the moving portion sliding through spaced linear bearing means rotatably supported on the fixed portion to camber the moving portion during said transverse movement, wherein the linear bearing means to opposed sides of the line of action are supported in movable carrier means and second drive means is operably connected to the movable carrier means to set a distance between each movable carrier means and the line of action so that for differently sized test subjects the point of contact between the test subject and the member can be maintained at a datum position over a range of camber angles.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partially sectioned plan view of a loading arm assembly that forms part of a loading carriage of a tyre wheel and brake test machine; Figure 2 is a plan view of the loading arm assembly; Figure 3 is an enlarged view in vertical section of part of the loading head adjacent a control arm; and Figure 4 is a side view of the loading head with a bearing and transducer assembly forming part thereof removed.

In a dynamometer for testing tyres and/or wheels and brakes of aircraft a runway is simulated by the surface of a large rotatable drum 10 with which a tyre wheel and brake assembly 12 is maintained in rolling contact.

The tyre makes a "footprint" on the drum 10, and the effective centre of load 14 applied to the drum 10 by the tyre should lie on a line of action 16 of a loading head generally designated by the reference numeral 18. The tyre wheel and brake assembly 12 includes an axle 20 that is rotatably supported in a load transducer and bearing module 22 described in more detail in our copending patent application No 8709938 in which a bearing for the axle 20 is supported in a linkage equipped with load cells in the load path from the assembly 12 to a body part of the module 22 attached to the remainder of the loading head 18.A cantilever arm assembly has one limb constituted by the module 22 which is directed par allel to but spaced from the line of action 16 and a second limb constituted by a mounting plate 24 directed normal to and extending across the line of action 16. The mounting plate 24 is in turn supported by a mounting bracket 26 provided with bearing members 27 against which the back surface of plate 24 lies and that serve to transmit load from the bracket 26 to the plate 24. The bracket 26 is supported by a bearing 28 from a thrust plate 30 of the loading head, the plate 30 being operably connected to hydraulic rams (not shown) that supply an intended load along the line 16.The bearing 28 allows the bracket 26 to rotate relative to thrust plate 30 to set an intended yaw angle of tyre wheel and brake assembly 12 relative to drum 10, there being locking means (not shown) for maintaining the intended yaw angle. Camber angle of the tyre wheel and brake assembly 12 is set by moving the plate 24 transversely of the bracket 26 as indicated by the arrow 32. In aircraft use, yaw simulates the effect of the aircraft being steered on the ground, cornering or landing in a cross-wind. To adjust the camber angle an electrical motor (not shown) rotates a lead screw 34 supported on bearings in bracket 26. A travelling nut 36 on lead screw 34 is pivoted in a bracket structure 38 so attached to the back face of bracket 24 as to move therealong.The plate 24 carries, on its upper and lower faces, first and second tracks 40,41 to opposed sides of the line of action 16 and directed at an angle to one another.

The tracks 40,41 slide through pivoted linear bearing members (described below) on the bracket 26 so that as the plate 24 translates, the attitude of the plate relative to the line of action 16 varies.

A problem with arrangements in which the camber tracks 40,41 pass through fixed locations on the bracket 26 is that the centre of contact or load 14 between the tyre wheel and brake assembly 12 and the drum 10 moves away from its datum position on the line 16 as the assembly 12 is cambered to an extent dependent upon tyre size. The present invention enables an accurate contact position to be maintained as the assembly 12 is cambered.

Referring now to Fig. 3, the bracket 26 has on its visible face to each side of the line of action 16 upper and lower pairs of plates 50 in which are set bearings 52 that support hinge shaft 54 for rotation about an axis that is normal to the line of action 16 and to the lead screw 34. An arm 56 fits between each pair of plates 50 at each end of the shaft 54 to which it is pinned at 55, there being four such arms each engaged with a respective one of the camber tracks 40,41 of the two pairs of such tracks on a pair of opposed face of the bracket 24. The rotational position of the shaft 54 therefore sets the angular position of its respective arms 56 traversing the opposed faces of the bracket 24. Each arm 56 has on its lower face in the region of the shaft 54 a control lever 57 that is connected for rotation with the arm 56 by means of screws 58 and dowels 59.To each side of the bracket 26 upper and lower control arms 42 are pivoted about axes 43 normal to the centre line 16 and normal to the lead screw 34. The extremities of the arms 57 carry swing bolts 44 pivoted about axes 43 and with their threaded stems passing through the arms 42 and carrying locknuts 46. Slackening the locknuts 46 permits rotation of the shafts 54; retightening thereof immobilises the shafts 54.

Bushes 60 towards the free ends of the arms 56 are recessed to accept camber tracks 40 or 41 on the upper or lower face of the plate 24. As previously stated the tracks 40,41 are in angled pairs and it will be noted that they are straight. The angle between the tracks 40,41 is determined in accordance with geometrical requirements to enable the plate 24 to be cambered relative to the thrust plate 30 and bracket 26, and during this operation (which is brought about by rotation of the lead screw 34) the tracks 40,41 slide through the bushes 60 which rotate in the arms 56 under the control of pinch bolts 62. To maintain the point of contact 14 in its datum position during cambering of the tyre wheel and brake assembly 12 the arms 56 are rotated by means of the shafts 54 whose upper ends carry control levers 64.The free ends of levers 64 carry captive pivoted nuts 66 with threaded through-holes normal to the pivot axis. A common adjustment screw 68 is threadedly engaged with each nut 66 and is formed with oppositely-handed threads to either side of the line of action 16 so that rotation of the shaft 68 in one direction causes the arms 56 to converge and rotation in the other direction causes them to diverge, thereby increasing or decreasing the spacing between each bush 60 and the line of action 16. Each bush 60 provides the linear bearing through which the respective camber track 40,41 slides and is rotatably supported in its respective arm 56.

For test of a tyre wheel and brake assembly 12 in the camber mode, the knurled locknuts 46 are released, freeing the shafts 54, after which the shaft 68 is rotated by a drive motor (not shown) to set the spacing between bushes 60 appropriately for the tyre diameter of the assembly 12 under test. A scale may be provided to enable the appropriate setting to be made, and this may donveniently be done by providing an indexing mark on one of the bushes 60 that moves over a scale on the arm 56. The appropriate camber angle is then selected by means of a motor and gearbox (not shown) driving the lead screw 34, moving the plate 24 transversely of the line 16 with the camber tracks 40,41 moving through the bushes 60 and with the lead screw 68 stationary so that the spacing between the bushes 60 remains constant. At zero camber angles a locking pin (not shown) can lock the device through the bushes 60 into the tracks 40,41; at other camber angles the position of the device is held by a lead screw 34.

Various modifications may, of course, be made to the embodiment described above without departing from the invention, the scope of which is defined in the appended claims. For example, the tyre wheel and brake assembly need not be simply cantilevered from the unit 22, and instead it can be tested in full fork support with a prop affixed to the other side of the plate 24.

Claims

1. A connector assembly for connecting sliding carriage means of an eventual dynamometer loading head with distal portions of the loading head supporting an eventual test subject, comprising a fixed portion for attachment to sliding carriage means of the loading head and a movable portion forming a proximal portion of eventual cantilever arm means whose intended distal portion has support means for the eventual test subject, drive means being operably connected between the fixed and movable portions to move the movable portion transversely of a line of action of the eventual loading head with spaced, mutuallyinclined camber tracks on the movable portion being slideable through spaced linear bearing means rotatably supported on the fixed portion to camber the movable portion during said transverse movement, wherein the linear bearing means to opposed sides of the eventual line of action are supported in movable carrier means and second drive means is operably connected to the movable carrier means to set a distance between each movable carrier means and the eventual line of action so that for differently-sized test subjects the point of contact between the test subject and an eventual rotatory dynamometer member can be maintained at a datum position over a range of camber angles.

2. A connector assembly according to claim 1, wherein each movable carrier means comprises an arm pivoted to the fixed portion for rotation about an axis normal to the line of action and to the direction of movement of the cantilever arm means, the linear bearing means being rotatably supported towards the free end of each arm under the control of pinch bolt means.

3. A connector assembly according to claim 2, wherein each arm further comprises nut means pivoted therein towards the free end thereof and threadedly engaged with lead screw means having oppositely handed threads to opposed sides of the line of action so that rotation of the lead screw in one direction moves the arms in synchronism towards the line of action and rotation in the other direction moves the arms in synchronism away from the line of action.

4. A connector assembly according to claim 2 or 3 wherein each arm has an attached lever connected to releasable clamping means operable to immobilise the arm during movement of the cantilever arm means.

5. A dynamometer comprising a member mounted for rotation and driveable by driving means, loading head means supported for movement towards the member along a line of action and cantilever arm means attached to the loading head means for supporting a test subject in rolling contact with the member, wherein drive means is operably connected between fixed and movable portions of the cantilever arm means to move the movable portion transversely of the line of action with spaced, mutually-inclined camber tracks on the moving portion sliding through spaced linear bearing means rotatably supported on the fixed portion to camber the moving portion during said transverse movement, wherein the linear bearing means to opposed sides of the line of action are supported in movable carrier means and second drive means is operably connected to the movable carrier means to set a distance between each movable carrier means and the line of action so that for differently sized test subjects the point of contact between the test subject and the member can be maintained at a datum position over a range of camber angles.

6. A dynamometer according to claim 5, wherein the member is a drum, and the test subject is a wheel mounted for rotation in contact with the surface of the drum and frictionally engaged therewith so that both rotate at the same surface speed.

7. A dynamometer having a loading head provided with cantilever arm means supporting the test subject and adjustable in camber substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

14. A connector for connecting sliding carriage means of an eventual loading head of a dynamometer to distal portions of cantilever arm means for supporting an eventual test subject, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

15. A modification of the loading head or dynamometer of any preceding claim wherein second arm means is provided on the loading head to provide full fork support for the eventual test subject.