GB1576024A - Method and jig for ascertaining the deformation in a damaged vehicle - Google Patents

Description

(54) METHOD AND JIG FOR ASCERTAINING THE DEFORMATION IN A DAMAGED VEHICLE (71) I, ERIK LENNART OLSSON, a Swedish Subject, of Claesborgsvagen 2, S-541 00 Skodve, Sweden, do hereby declare the invention, for which I- pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method and a jig for measuring vehicle frames or chassis usually in connection with realignment of deformed vehicles.

The procedure for repairing a bent vehicle frame or chassis usually consists of two phases, namely measurement of the magnitude of the deformations and the application of suitable alignment forces to the vehicle frame or chassis in order to force it back into its original form. According to previously known methods, one generally had to alternate between the measuring and aligning phases a number of times until the frame has recovered its original shape.

With conventional techniques, the measurement and realignment procedure is performed on rigid and expensive alignment benches, which are designed for both phases of operation. For the measuring phase, jig sets of different design are often used for different car makes. The jig set is mounted on the alignment bench, but must be removed during- the alignment phase in order to- avoid damage to it. The jig sets are, as a rule, tedious to mount, which makes repeated measurements a major work effort. Rigid alignment benches on which a vehicle is retained during the alignment phase are in addition very expensive.

With conventional techniques, one is often measuring vertical distances between certain points on the bench and certain reference points on the vehicle, which necessitates a very accurate retention of said vehicle to ensure that no movement of the vehicle takes place, since movement of the vehicle with respect to the bench directly affects the measured result. It is possible that an unnoticed and perhaps invisible movement between one reference point and a nearby retention point occurs, such that a measuring error arises without one being aware of it.

Conventional techniques thus necessitate checking the vehicle retention on the bench every time a switch from an aligmnent to a measurement phase is made, in order to check that the vehicle has not moved during the alignment phase. This is due to the fact that inaccuracy in measurement is immediately introduced when the vehicle moves if the measurement apparatus is secured to the measurement bench, and measurements are taken of the distances between the vehicle and the bench. Inaccuracy may in fact easily arise in any device in which the measurement apparatus is not secured to the vehicle itself.

The alignment devices that are available on the market have, as a rule, a rigid alignment bench for the performance of the alignment phase during which the vehicle is to be secured to said bench. In addition said devices have measuring apparatus of various kinds. Certain alignment brenches may be equipped with special measuring equipment of, e.g. laser- - or ruletype. Thus, anyone who only wishes to undertake measurements of deformations, e.g. to ascertain what correction has to be applied to a vehicle chassis, has to procure an expensive alignment bench around which the measuring equipment is moun- ted.

The object of the present invention is to perform the measurements with an actual size "copy" of the car manufacture's production jig with respect to those reference points which, during vehicle alignment, are essential to check. It has therefore been necessary to design a measuring instrument that is adjustable in precise intervals of, > for example, one millimetre in any one of the three dimensions such that the production jig for every conceivable vehicle model may be "copied". In doing so, one has to ensure compliance between given reference points and those dimensions which the designer originally specified for the vehicle in question.

According to the present invention there is provided a method of ascertaining the deformation in a damaged vehicle using a jig that comprises means for varying the position and orientation of the jig and for maintaining the jig in one position and orientation, three or more contact means located at known positions on the jig and at least one test member movably mounted on the jig, which method comprises identifying three points on the vehicle that have been unaffected by the damage, adjusting t'he 'positionlorientation varying means so as to bring a different contact means into contact with each of the three said points, moving the test member to a position in which a damaged point should be located, ascertaining the deformation of the vehicle, and realigning the vehicle while the contact means are in contact with the vehicle.

The present invention also provides a jig for use in ascertaining the extent of deformation in a vehicle which jig comprises a frame, means for varying the height and orientation of the frame, three or more contact means mounted on the frame and locatable in a known position relative to the frame for contacting parts of the vehicle that are in their proper location, and a test member that is mounted on the frame and is locatable in a position in which a damaged part of the vehicle should be located.

The measurements of a vehicle are carried out in such a manner that a movable jig is pre-adjusted so that it can contact simultaneously the reference points whose mutual relative positions are known from the specifications of the car manufacture.

The measuring jig is then placed underneath the car and the jig is elevated by integrated elevating means, for example, hydraulic or pneumatic cylinders that may be fitted with wheels and attached to the jig. The car may during the process rest on trestles, its own wheels or other means of support. When elevating the jig a number of contact means (at least three) are brought into contact with reference points of undamaged parts of the vehicle. The elevating means are jointly or individually controlled, for example by means of communicating pneumatic or hydraulic cylinders, in such a manner that the raising of a contact means ceases as soon as contact (with a certain contact pressure) is established between the respective contact means and a reference point on the vehicle. When contact is established at all three or more reference points, the measuring jig has aligned itself to the same plane as that of the vehicle, allowing measurements to be carried out irrespective of the vehicle orientation.

The setting of the jig facilitates the checking of the relative positions of those points which are most important or are essential from a design point of view, so that the vehicle, when matched to the jig, must have been restored to its original condition.

Measurements are taken between the test member and the damaged points of a vehicle.

Another object of the present invention is to enable the measuring jig to be used during the alignment phase proper, thus assuring faster work, since the test member of the measuring jig may be brought into a measuring position and removed from that position rapidly. This may be done throughout the entire alignment work phase without removing the jig. Often it is necessary to dismount the test member but only during alignment. In order to perform swift measurements it may be of advantage to equip the contact means with sensors, e.g. spring loaded electrical push switches, electronic pressure sensors or other electrical sensors so that all desired measuring points may be checked -at the same time.

Another purpose of the present invention is to make the measuring jig that can be - used with different makes of alignment equipment regardless of whether the vehicle rests on its own wheels, on a lift or on trestles. Furthermore, there is no requirement on the levelness of the floor or that the vehicle should be oriented in any particular way. Most conventional measuring devices require the vehicle to be retained in an exactly horizontal position.

Another object of the present invention is to create a fast, inexpensive and reliable instrument of diagnosis. This is of special interest to people, e.g. assurance companies, sales companies, testing institutions, police etc., who are normally not directly engaged in the car repair business, but still have to check vehicles in a simple way. This is particularly important in those cases in which one has to be able to determine in a reliable way firstly whether a vehicle is repairable and secondly whether a certain alignment job has been carried out in a safe and acceptable manner.

The contact means of the measuring jig are arranged in accordance with an assembly chart that is stipulated for every car model. The jig will then constitute an actual size "copy" of the production jig for all essential reference points. The jig is then placed underneath the vehicle and the frame of the jig is elevated and orientated (if necessary) until the contact means engage at least three reference points. The frame may be elevated and orientated by legs that may consist of hydraulic or pneumatic cylinders that are jointly or individually controlled. When the measuring jig is elevated to its proper level it is essential that only such a force is applied that is required to maintain the contacts means of the jig in contact with the vehicle.

This is always so regardless of what system is used to perform the level control of the jig frame. Thus, the contact means are kept in contact with the three reference points at all times. The jig will thus adjust itself to the appropriate position irrespective of type of support or floor on which the car and jig is resting and whether this support or floor-is level or not.

The measuring jig may be such that it can remain in place underneath the car during the entire alignment procedure without being damaged. This is possible because of the ability of the measuring jig to move in all directions. The system of level control of the jig preferably enables the jig to move without considerable resistance in a mainly vertical direction and the wheels of the jig enable it to move in the horizontal direction. Thus, the measuring jig will allow all those positional changes that can normally arise during the course of the alignment work.

During alignment, the test member at a damaged reference point is removed and then the required push or pull forces to correct the vehicle may be applied. With the measuring jig engaged one may check easily whether the correction is sufficient or not. The only thing that need be done before such checking, is to return the test member for a damaged point to its fixed and locked position, whereupon a new check measurement may be done.

The alignment procedure is based on the principle that at least three of the vehicle reference points are undamaged, so that one has a given, fixed triangle with three fixed sides in known positions from which the position of any other reference point of the vehicle can be calculated. However, it may happen that the three reference points that were believed to be undam aged, mav in fact be damaged, due to material springing back to its original position or that, e.g. a joint or weld has been broken or damaged. In such a case there is a certain risk that this may not be discovered during the first measurements.

Also there is a certain risk that the "fixed" triangle may be displaced from its known position if unsllitable or too large alignment forces are applied. In all above mentioned cases there is a chance that the contact means of the measuring jig may be damaged as a result of the contact means of the jig being in continuous contact with the undamaged reference points during the course of the alignment work. In view of the above mentioned it may be advantageous to protect the jig proper against excessive forces, which may cause deformation to the jig. This may be. done by providing all contact means with a line of weakness that will rupture before any deformation of the main part of the jig has occurred. Another method that may be used to protect the jig is to employ magnets in the support mounting of the contact means. The magnetic attraction between the support for the contact means and the frame of the jig is sufficient, in normal usage, to ensure that the contact means is retained in the desired position. 'How- ever, if too large a force is applied to-th contact means, the force will overcome the magnetic attraction between frame and contact means, thereby allowing the contact means to be displaced without it coming to any harm.

A measuring jig that is constructed in accordance with the present invention and various alternative' parts that may be used in conjunction therewith will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1, is a view in perspective of the measuring jig according to the invention, Figure 2, is a perspective view of part of the jig shown in Fig. 1, Figure 3, is a perspective view of an alternative part of the jig of Fig. 1, Figure 4, is a sectional view of alternative parts of the jig of Fig. 1, Figure 5, is a perspective view of the parts shown in Figure 4.

Initially, with reference to figure 1, a measuring jig frame consists of two longitudinal beams 1 and a number of transverse beams 2, which constitute a rigid frame. The longitudinal beams 1 are on their top sides provided with a large number of holes 3 located symmetrically and spaced (e.g. every ]00 mm) for mounting three or more bridges 4, which thus may assume any one of a number of different possible positions along the beam 1. The bridges are parallel to the transverse beams 2. Every bridge 4 is secured using any pair of opposed holes 3.

Between adiacent transverse beams 2 at both ends of the jig there are a pair of lee support beams 5 mounted parallel to, and at a suitable distance from the longitudinal beams 1. At the centre of each leg support beam 5, a leg 6 is mounted, which may be provided with a rolling means 7, e.g. a wheel or a castor, which may be mounted to be capable of turning about a vertical axis. The beams 1, 2 and 5 must be rigid enough to withstand any deformation of the frame under contact pressures that, in operation, arise. The legs 6 may each consist of a cylinder with a hydraulic or pneumatic piston, so that the frame may be level controlled by adjusting each leg separately. Additionally, every leg 6 may be provided with a mechanical spring which is acting between the leg and beam 5. Each spring is prestressed, that is to say, it is put under a stress, which is greater than that resulting from the weight of the jig, prior to the engagement between the contact means and the reference points. It is thus possible to obtain a desired initial pressure between the contact means and the reference points, the operator being able to tell when that pressure is acting since the springs then start to deform.

The frame may also be provided with a control beam 8 mounted between the centremost transverse beams 2 and in parallel with beams 1. The control beam is intended to support required operational equipment, e.g. a hydraulic or pneumatic pressure equalizing vessel (not shown), a reducing valve 10A and a pressure gauge 1 0B for setting and providing the desired pressure of pneumatic or hydraulic fluid to each leg via hose connections.

The bridges 4 support the contact means 11, which are to engage the reference points of the vehicle and also the test member. The test member may be any one of the contact means 11. The only difference between a contact means and a test member is in the way it is used in the measuring operation. Said bridges 4 are provided with holes 12, e.g. every 100 mm, which are intended partly for use in securing the bridges 4 onto the beams 1, and partly for use in mounting vernier plates 13.

Every bridge can accommodate up to four vernier plates 13, which may be mounted in a desired position on the selected bridge 4.

Each vernier plate 13 is screwed onto the bridge 4 and then acts as a foundation for another vernier plate 15, which may be moved along the underlying fixed vernier plate 13 and positioned with an accuracy which is determined by the design of the two vernier plate scale's.

As shown in figure 2, setting of the vernier plates is made by means of a series of holes 14, which are transverse with respect to the beams 1, spaced at, e.g. 10 mm intervals on the vernier plate 13 and by means of a parallel transverse row of holes 16 spaced at, e.g. 9 mm intervals on the vernier plate 15. The plate 15 is also provided with a longitudinal row of 'holes 17, e.g. spaced at 10 mm intervals. Figure 2 also shows in detail the mutual positions of the plates. On top of vernier plate 15 there is another vernier plate 18 which has a longitudinal series of holes 19 spaced at, e.g. 9 mm intervals. This allows the setting of the vernier plate 18 with an accuracy according to the example described of 1 mm in both the transverse and the longitudinal direction as will be described below. On the vernier plate 18 a support cylinder 21 is mounted, which is provided with two columns of vernier holes 22, e.g. spaced at 10 mm intervals (a socalled double or folded vernier, in which holes of one column are slightly displaced with respect to the holes of the other column by, e.g. 5 mm so as to provide a complete set of vernier holes, i.e. ten or more holes without having an inconveniently high cylinder 21).

Inside the support cylinder 21, a rod or sensor support 23 may slide in a vertical direction. In said rod 23 there is a corresponding vernier hole series 24 arranged spaced at, e.g. 9 mm intervals. The rod 23 may therefore be adjusted with an accuracy according to the example of 1 mm.

The rod 23 is provided at its top with a centre hole, which accommodates a contact means 11, sliding vertically in said centre hole. Said contact means 11 may be fixed in the hole by a locking pin 25.

The support cylinder 21 and the rod 23 are provided with through holes for cooperation with the locking pin 25.

All vernier hole series are provided with locking pins 26, which are inserted into the appropriate holes in the two vernier plates to lock the two plates together. Because the spacing between the holes in one plate differs from the spacing between the holes in the other plate, the two plates can be locked together by the insertion of the locking pin in the appropriate holes with an accuracy of the difference between the spacings of the two rows. In order to avoid excessive load on the vernier members and their locking pins 26 said members are provided with locking arrangements. As shown in figure 2, the fixed vernier plate 13 is provided with two transverse slots 27 for the cooperation with two locking bolts (not shown) mounted in hole 29 on the vernier plate 15.

In a similar manner the vernier plate 15 is provided with two transverse slots 31 for cooperation with four bolts 32, which are mounted each in its own hole on the support flange 33 at the lower end of the support cylinder - 21. The bolts 32 also serve as means for securing the support cylinder 21 on the vernier plate 18. ' The support cylinder 21 may possibly be rota-' table inside the support'flange 33,pin which case it may be locked by means of a pin in hole 30.

As shown in figure 3 the contact means 11 may have a different design depending on the shape of the reference point that the contact means 11 is to contact.

The contact means 11 may (see figure 3) be provided with connection means 35 for an electrical pressure switch, which is not shown. The contact means 11 may also be provided with a line of weakness, for example, in the form of a deeply cut circular groove 34, so that the remaining material is relatively thin. The contact point will thus break off if excessive load is applied to it which prevents the jig from being damaged.

The above described device operates in such a manner that a desired number of contact means (this number may be high and is at least three) may be set (using the jig described) to the nearest millimetre in all three dimensions within the entire range of the measuring jig. Said accuracy may, however, easily be increased, e.g. ten times by changing the hole intervals of the vernier hole series (such a change would probably necessitate a reduction in the hole diameters).

The hole pairs 3, which are to be used for mounting respective bridges 4, are set for each car model, as also are the settings of all vernier holes. In doing so it will be of advantage to identify all vernier and mounting holes by means of suitable digit and/or letter combinations. One may thus conveniently tabulate the information on how to set the jig. When this setting is done the required type of contact means 11 for the particular car model must be chosen. These contact means 11 are inserted into the rods 23 and locked in proper position with the locking pins 25. For use with very common car models one may design a fixed attachment for each contact means, which attachment is then mounted directly on the bridge 4 to save time with the setting of the vernier plates. The measuring jig is then inserted underneath the vehicle and elevated by means of the pneumatic or hydraulic arrangement in each leg 6 until the contact means 11 engage the desired reference points with a pre-determined contact pressure. Measurements may now be performed visually or electrically. Depending on the alignment required, the alignment phase may immediately start with the measuring jig still in the engaged position since the jig will simply retract should the contact pressure during alignment exceed the value that the pressure equalizing system is adjusted to. The contact means situated at a damaged reference point, which acts as the test member, may, if so desired, be lowered down by removing the locking pin 25 during the alignment phase. In order to carry out a further measurement, the test member 11 is simply returned to its original.

position and further measurements may immediately be called out.

According to an alternative embodiment of the present invention the contact means 11 may be mounted horizontally as shown in figure 5 (by way of hole 62) or vertically as shown in figure 4. The vernier plates may also have a different design and also be provided with mounting magnets in order to avoid deformation of the contact means in the event that the alignment procedure should give substantial horizontal displacements of the reference points as is described below.

As mentioned above the vertical displacements may easily be absorbed by the resilient action of legs 6, which advantageously may consist of compressed air cushions in the form of rubber cylinders.

The latter may work independently of or in conjunction with each other, for example by way of communicating vessels.

With reference to figures 4 and 5 there is now shown a cylinder assembly 40 mounted on a lower vernier plate 41 and an upper vernier plate 42. The lower vernier plate 41 is provided with cylindrical pegs 43, which are intended to cooperate with an array of holes 44 in a perforated plate 45, which is fixed on top of the bridges 4.

Furthermore the vernier plates 41 and 42 are provided with a large centre hole into which a cylinder seat 47 may be fitted.

The seat 47 is provided with a bottom hole for a penetrating locking bolt 48, which cooperates with a retainer plate 49 having a tapped centre hole. Upon tightening the bolt 48, the seat 47, the retainer plate 49 and the bolt itself constitute a unit.

Directly below the retainer plate 49 and not in contact with same there is a fixed magnet plate 61, which underneath its centre has been provided with a stud 50. The stud 50 has in its turn on its lower side another peg 43.

The cylinder seat 47 has an external thread for cooperation with a locking nut 46, which, when tightened (downwards as seen in picture 4) locks the two vernier plates 41 and 42 in a desired, fixed mutual position with an accuracy of, e.g. 0 1 mm.

The relative positioning of the vernier plates is accomplished by suitable scales on the outer edges of the plates 41 and 42, as shown in figure 5. A mounting magnet 51 is then placed on the magnet plate 61, such that the magnetic flux is able to form a complete loop through the magnet plate 61, the stud 50 and the perforated plate 45.

The function of the pegs 43 is to' enable the operator to locate the correct position of the contact means support on the plate 45. However pegs alone are not sufficient to stop the entire contact means support assembly from simply falling sideways when the vehicle frame starts to move or vibrate mainly in a horizontal direction during the alignment procedure.

The purpose of the annular magnet 51 and the resulting magnetic attraction of plates 45, 61 and stud 50 is to obtain an adherence of the entire contact means support to the vernier plate 45 and to the bridge and jig proper. However, when an excessive sideways force is applied to the contact means, the contact means support assembly can move sideways since it is not rigidly attached to the plate 45, thereby saying the jig and the support assembly from being damaged.

For height adjustments the seat 47 is arranged with a helically grooved cylinder 52 sliding vertically inside the seat 47 and provided with a circumferential, helical groove 53. The seat 47 is also provided with a locking screw 54 for threaded cooperation with the side wall of the seat 47.

The screw 54 may thus slide along the groove 53 and turning the spiral cylinder 52 will then change its vertical position.

As shown in figure 5, the helically grooved cylinder 52 may be provided with a scale to indicate, e.g. 0 1 mm in height. Inside the cylinder 52 there is another cylinder 55 arranged, which has horizontal circumferential grooves 56 arranged with, e.g. 10 mm intervals. In the side wall of cylinder 52 there is also arranged a locking screw 60 in the same way as in the side wall of seat 47. Said locking screw 60 will then cooperate with said horizontal grooves 56.

As shown in figures 4 and 5 the contact means 11 are provided with a cylindrical lower part or stem 58, which has one transverse groove 59. In mounting the contact means 11 said groove 59 cooperates with a locking screw 63, which is located by means of threads in the side wall of the cylinder 55. The contact means 11 can now be locked into either a vertical position as shown in figure 4 or into a horizontal position by way of hole 62 (shown in figure 5). In the latter case the stem 58 of the contact means 11 is inserted into the hole 62, which is arranged in the vertical wall of cylinder 55.

The contact means 11 is also provided with a threaded hole for the mounting of a contact point 57, which is to engage the vehicle reference point.

The embodiment of figure 4 and 5 operates in the following manner: In order to set an individual contact point 11 to a specified position within the three dimensional range of the measuring jig, the specified bridge 4 is first screwed onto its required position on beams 1.

The bridge 4 has on its upper side an array of holes 44 so that the lower pegs 43 of the cylinder assembly 40 will engage in specified rows of holes 44. In this way the cylinder assembly 40 may be oriented in the entire plane of the measuring jig with an accuracy of 10 mm.

By means of vernier scales on the lower vernier plate 41 and on the upper vernier plate 42 a fine adjustment may be made with an accuracy of, e.g. 0 1 mm. The bolt 46 is then tightened, the vernier plates 41 and 42 thereby being fixed in their respective positions.

The vertical level adjustment is then carried out. A groove 56 is brought into contact with the locking screw 60 whereby the level is set with an accuracy of 10 mm.

Fine level adjustment with, e.g. the accuracy of 0 1 mm is then achieved by turning the helically grooved cylinder 52 in contact with the locking screw 54 to the desired position, whereupon the locking screw 54 is tightened.

In the event that one wishes to give the contact point 57 an arbitrary angle with the horizontal and/or vertical plane -one may, e.g. arrange the contact means 11 with a bent stem 58 (for example at 90 degrees to the cylinder 55. The area or edge around hole 62 may also be provided with scales (not shown) to facilitate the setting of any desired angle.

Instead of the legs being provided with pneumatic or hydraulic cylinders in order to raise, lower and orientate the frame, the jig may b

Claims (25)

**WARNING** start of CLMS field may overlap end of DESC **. of the contact means support on the plate 45. However pegs alone are not sufficient to stop the entire contact means support assembly from simply falling sideways when the vehicle frame starts to move or vibrate mainly in a horizontal direction during the alignment procedure. The purpose of the annular magnet 51 and the resulting magnetic attraction of plates 45, 61 and stud 50 is to obtain an adherence of the entire contact means support to the vernier plate 45 and to the bridge and jig proper. However, when an excessive sideways force is applied to the contact means, the contact means support assembly can move sideways since it is not rigidly attached to the plate 45, thereby saying the jig and the support assembly from being damaged. For height adjustments the seat 47 is arranged with a helically grooved cylinder 52 sliding vertically inside the seat 47 and provided with a circumferential, helical groove 53. The seat 47 is also provided with a locking screw 54 for threaded cooperation with the side wall of the seat 47. The screw 54 may thus slide along the groove 53 and turning the spiral cylinder 52 will then change its vertical position. As shown in figure 5, the helically grooved cylinder 52 may be provided with a scale to indicate, e.g. 0 1 mm in height. Inside the cylinder 52 there is another cylinder 55 arranged, which has horizontal circumferential grooves 56 arranged with, e.g. 10 mm intervals. In the side wall of cylinder 52 there is also arranged a locking screw 60 in the same way as in the side wall of seat 47. Said locking screw 60 will then cooperate with said horizontal grooves 56. As shown in figures 4 and 5 the contact means 11 are provided with a cylindrical lower part or stem 58, which has one transverse groove 59. In mounting the contact means 11 said groove 59 cooperates with a locking screw 63, which is located by means of threads in the side wall of the cylinder 55. The contact means 11 can now be locked into either a vertical position as shown in figure 4 or into a horizontal position by way of hole 62 (shown in figure 5). In the latter case the stem 58 of the contact means 11 is inserted into the hole 62, which is arranged in the vertical wall of cylinder 55. The contact means 11 is also provided with a threaded hole for the mounting of a contact point 57, which is to engage the vehicle reference point. The embodiment of figure 4 and 5 operates in the following manner: In order to set an individual contact point 11 to a specified position within the three dimensional range of the measuring jig, the specified bridge 4 is first screwed onto its required position on beams 1. The bridge 4 has on its upper side an array of holes 44 so that the lower pegs 43 of the cylinder assembly 40 will engage in specified rows of holes 44. In this way the cylinder assembly 40 may be oriented in the entire plane of the measuring jig with an accuracy of 10 mm. By means of vernier scales on the lower vernier plate 41 and on the upper vernier plate 42 a fine adjustment may be made with an accuracy of, e.g. 0 1 mm. The bolt 46 is then tightened, the vernier plates 41 and 42 thereby being fixed in their respective positions. The vertical level adjustment is then carried out. A groove 56 is brought into contact with the locking screw 60 whereby the level is set with an accuracy of 10 mm. Fine level adjustment with, e.g. the accuracy of 0 1 mm is then achieved by turning the helically grooved cylinder 52 in contact with the locking screw 54 to the desired position, whereupon the locking screw 54 is tightened. In the event that one wishes to give the contact point 57 an arbitrary angle with the horizontal and/or vertical plane -one may, e.g. arrange the contact means 11 with a bent stem 58 (for example at 90 degrees to the cylinder 55. The area or edge around hole 62 may also be provided with scales (not shown) to facilitate the setting of any desired angle. Instead of the legs being provided with pneumatic or hydraulic cylinders in order to raise, lower and orientate the frame, the jig may be provided with a bellows, the bottom of which contacts the ground and the top of which contacts the frame. A large circumferential spring may be fitted to the side walls of the bellows to reinforce them. WHAT I CLAIM IS: -

1. A method of ascertaining the deformation in a damaged vehicle using a jig that comprises means for varying the position and orientation of the jig and for maintaining the jig in one position and orientation, three or more contact means located at known positions on the jig and at least one test member movably mounted on the jig, which method comprises identifying three points on the vehicle that have been unaffected by the damage, adjusting the position/orientation varying means so as to bring a different contact means into contact with each of the three said points moving the test member to a position in which a damaged point should be located, ascertaining the deformation of the vehicle, and realigning the vehicle while the contact means are in contact with the vehicle.

2. A jig for use in ascertaining the ex

tent of deformation in a vehicle which jig comprises a frame, means for varying the height and orientation of the frame, three or more contact means mounted on the frame and locatable in a known position relative to the frame for contacting parts of the vehicle that are in their proper location, and a test member that is mounted on the frame and is locatable in a position in which a damaged part of the vehicle should be located.

3. A jig as claimed in claim 2, wherein the contact means and the test member are each mounted on ad"'5laim a support.

4. A jig as claimed in claim 3, which includes a plurality of horizontal plates, wherein the arrangement is such that each support is movably mounted on a plate and wherein there is provided means for indicating the position of each support on its respective plate.

5. A jig as claimed in claim 4, wherein the means for indicating the location of a support is a pair of scales having regularly spaced calibration markings, one scale being on the support and the other being on the plate, and wherein the spacing between adjacent markings on one scale is greater than the spacing on adjacent markings on the other scale.

6. A jig as claimed in claim 4, which includes means for locking the support in a desired position on the plate.

7. A jig as claimed in claim 4, wherein the means for indicating the location of a support is a pair of regularly spaced rows of holes and a locking pin, one row of holes being formed in the support and the other row in the plate, the spacing between adjacent holes of one row being greater than the spacing between adjacent holes of the other row, and wherein the support can be locked in a known position on the plate by the insertion of a locking pin through an appropriate hole one row into an appropriate hole in the other row.

8. A jig as claimed in any one of claims 3 to 7, wherein the contact means and the test member are each so mounted on their respective supports that they are movable in a vertical direction relative to the support, and there is provided means for positioning each of the contact means and the test member at a desired known height.

9. A jig as claimed in claim 8, wherein each height positioning means is a pair of rows of holes, one row being in the support and the other in the contact means or in the test member, and a locking pin, the spacing between adjacent holes of one row being greater than the spacing between adjacent holes of the other row, and wherein the contact means can be locked at a known height by the insertion of the locking pin through an, appropriate hole of one row into an appropriate hole of the other row.

10. A jig as claimed in any one of claims 4 to 9, wherein the spacings between adjacent markings in the two scales of the pair of scales or between adjacent holes in the two rows of the pair of rows of holes is 10 mm and 9 mm.

11. A jig as claimed in any one of claims 4 to 9, wherein the spacings between adjacent markings in the two scales of the pair of scales or between adjacent holes in the two rows of the pair of rows of holes is 1 mm and 0 9 mm.

12. A jig as claimed in any one of claims 3 to 11, wherein each support includes a joint for orientating the contact means or the test member at a desired angle to the horizontal, and a scale for measuring the said angle.

13. A jig as claimed in claim 2, wherein each contact means and the test member is mounted on an assembly which has, on its bottom surface, two or more pegs and a magnet, and wherein the frame includes a plurality of horizontal magnetic bridge plates having perforations formed therein for cooperating with the pegs of the assembly, the arrangement being such that each assembly is secured to a bridge by magnetic attraction between the magnet and the bridge and by the pegs of the assembly engaging with the perforations of the bridge.

14. A jig as claimed in claim 13 and in any one of claims 3 to 12, wherein the support forms part of the assembly.

15. A jig as claimed in claim 14 and in any one of claims 4 to 7, wherein the plate forms part of the assembly.

16. A jig as claimed in any one of claims 2 to 15, wherein each contact means includes an electric pressure-actuated switch for sensing when the contact means has contacted the vehicle.

17. A jig as claimed in any one of claims 2 to 16, wherein each contact means has a line of weakness, the arrangement being such that the contact means will fracture along the line of weakness if an excessive force is applied thereto.

18. A jig as claimed in any one of claims 2 to 17, wherein the height and orientation varying means comprises at least three legs, each of which includes a hydraulically- or pneumatically--controlled piston-and-cylinder for adjusting the length of the leg.

19. A jig as claimed in claim 18, which includes means connected by hydraulic or pneumatic hoses with the cylinder of each leg for maintaining the pressure in each leg at a desired level.

20. A jig as claimed in claim 18 or claim 19, which comprises springs located between the frame and each cylinder, the arrangement being such that the springs are so mounted that they are always under stress.

21. A jig as claimed in any one of claims 18 to 20, wherein each leg has a castor.

22. A jig as claimed in any one of claims 2 to 17, wherein the height and orientation varying means comprises a bellows which can be expanded to raise the frame or contracted to lower it.

23. A jig as claimed in claim 22, wherein the side wall of the bellows is reinforced with a large circumferential spring.

24. A jig as claimed in claim 22- or claim 23, which comprises three or more legs each of which has a castor.

25. A jig which is substantially as hereinbefore described with reference to, and as shown in, Figs. 1 to 5 of the accompanying drawings.