GB2177223A

GB2177223A - Wheel alignment gauge

Info

Publication number: GB2177223A
Application number: GB08615838A
Authority: GB
Inventors: William Keith Hayward
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-06-29
Filing date: 1986-06-30
Publication date: 1987-01-14
Also published as: GB8615838D0; GB2177223B

Abstract

A wheel alignment gauge for measuring the toe-in or toe-out alignment of a pair of wheels includes a pair of symmetrical rigid channel members, one supported on each wheel by rubber straps hooked in holes 8 and passing around each wheel. Each member is located such that projections (11, 12) contact the wheel rim to align a reference point pair 14, one of each member, both forward and rearward of the wheel. A measurement of the difference in separation between the forward pair and rearward pair of reference points may be made in selected units. The reference points (14) of a member are arranged to be substantially 57.3 measurement units apart, so that the difference measurement provides a direct reading of toe-in or toe-out in degrees, without recourse to geometrical calculation or angle measurement. <IMAGE>

Description

SPECIFICATION Wheel alignment gauge THIS INVENTION relates to a wheel alignment gauge for measuring the so-called toe-in or toe-out alignment of a pair of wheels of a vehicle, such as a car, van, truck, lorry and the like, that is to say the angle of inclination between the wheels in a horizontal plane.

According to the present invention there is provided a wheel alignment gauge comprising a pair of substantially rigid members each having a pair of equally spaced reference points and being adapted to be supported substantially perpendicularly to the axis of a vehicle wheel and having location means co-operating with the wheel such that corresponding reference points of the members are aligned respectively in front of and behind wheels whose alignment is to be gauged and substantially parallel to the line joining the centre of the wheels; the spacing of the reference points on each member being substantially 57.3 measurement units such that difference in distance between respective pairs of reference points in front of and behind the wheels expressed in measurement units is equal to toe-in or toe-out wheel alignment expressed in degrees.

Assuming that the wheels have a toe-in or toe-out angle a and utilising the property that for sufficiently small angles, such as the typical values of the toe-in or toe-out angle of vehicle wheels, sin a is approximately equal to a measured in radians, it can be shown by simple geometry that the difference between the measured distances is proportional to the angle a to a close approximation.

The conversion from the value obtained of the difference between the measured distances to the angle is simplified by spacing apart the reference points on each member by a distance of 57.3 units (57.3 approximately equals 360 2n and is thus the conversion factor for converting radians to degrees). It can easily be shown that if the distances are measured in the same units, the value of the difference between the measured distances is equal to the angle measured in degrees, to a close approximation.

Advantageously, the spacing between the reference points on a member is arranged to be 57.3 centimetres, which not only provides a gauge of convenient dimensions for use with motor car road wheels, but allows a direct reading of toe-in or toe-out alignment to be achieved with a conventional centimetre tape measure.

Centimetre tape measures made of steel or other non-stretch material are entirely suitable for this application, being commonly available, the non-stretch property enabling the difference between the measured distances to be accurately determined even though this difference is small in comparison with the distance apart of the two wheels.

The members can be made in any suitable rigid material such as folded metal sheet, metal die castings, plastics mouldings, and metal or plastics extrusions subsequently machined.

In a preferred arrangement, each member comprises a metal sheet bent to form an elongate channel having an elongate rectangular central portion and perpendicular upper and lower elongate rectangular arm portions. The upper arm portion conveniently includes a centrally located coplanar extension surface the major free edge of which is adapted to abut at two places the edge of the lower portion of a wheel rim and includes a pair of alignment points each adjacent to a respective end of the major free edge thereof to facilitate accurate location of the member on a wheel rim. The major free edge of such an extension surface may, if desired, be recessed to leave the ends of the edge as projections to facilitate further correct positioning of the member on a wheel rim.

The lower arm portion may, if desired, include a centrally disposed projection that preferably has a curved outer edge to ensure single point contact of the lower arm portion with a tyre side wall.

Each member is conveniently secured to a wheel by means of an elastic strap or rope that is stretched around the wheel, hooks at each end of the strap or rope being secured in holes provided adjacent to each end of the member.

Desirably a slot is provided adjacent each reference point of one or both of the members for receiving and holding the hooked end of a tape measure and thus facilitating measurement of the distance between corresponding reference points.

The reference points may conveniently be provided on extended or offset end portions of each member to facilitate access thereto.

In an alternative arrangement, either or both the upper and lower elongate rectangular arm members may join with the rectangular central portion at an angle greater than 90 , so that in such arrangements a number of members may 'nest' closely together so as to take up less space when in storage or transit during the manufacturing process.

The reference points for measurement, the alignment points for contact with the wheel rim, and/or the point on the lower arm intended for contact with the tyre, may be clearly identified in some way such as by colouring, by symbols, or by plastics attach ments.

Either or both members may carry alignment related information in the form of a table or list of the correct settings for wheel alignment for a range of vehicles, or conversion chart for referring degree measurements to wheel rim diameter.

Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a rear view of member of a wheel alignment gauge in accordance with the present invention; Figure 2 is a plan view of the member of Fig. 1; Figure 3 is a section taken along line 3-3 of Fig. 1; Figure 4 is a section taken along line 4-4 of Fig. 1; Figure 5 is a perspective view of a portion of the members of a modification of the gauge of Figs. 1 to 4.

Figure 6 represents views of an alternative member of a gauge in accordance with the present invention; and Figure 7 shows a member supported on a wheel.

Referring to the drawings, a preferred embodiment of a wheel alignment gauge in accordance with the present invention comprises a pair of identical members 1, one such member being illustrated in Figs. 1 to 4. The member 1 is formed from a sheet of 20 gauge steel in the form of a rectangle 9 cm by 60 cm, one of the major sides of which includes an integral, centrally disposed, rectangular, planar extension 2 that is 2 cm by 20 cm.

The sheet is bent at 90" along two lines parallel to the major sides of the rectangle to form a channel-like configuration having an elongate rectangular central portion 3 that is 5 cm wide, a lower elongate rectangular arm portion 4 that is 2.5 cm wide and an upper elongate arm portion 5 the outer parts 5a of which are 1.5 cm wide and the central extended part 5b of which is 3.5 cm wide.

The upper arm portion 5 of member 1 includes two pairs of cut out triangular marks; a pair of measurement reference points 6 disposed adjacent the edge of the upper arm portion 5 adjoining the central portion 3, each point 6 being spaced 1.35 cm from a respective end of the member 1 and the points 6 thus being 57.3 cm apart; and a pair of alignment points 7 each adjacent to a respective end of the major free edge of the central extended part 5b of the upper arm portion 5.

The central portion 3 of the member 1 is drilled to form a pair of 0.75 cm diameter circular holes 8, the centre of each hole 8 being 1.5 cm from a respective end of the member 1. The holes are adapted to receive the hooked ends of an elastic strap, such as a 24" rubber luggage hook, for securing the member 1 to a vehicle wheel, the holes 8 being positioned slightly closer to the upper arm portion 5 than the lower arm portion 4 to ensure that when the member 1 is secured to a wheel the edges of the extended part Sb adjacent the alignment points 7 are pressed firmly against the edge of the lower portion of the wheel rim and the major free edge of the lower arm portion 4 merely rests against the tyre side wall.

The central portion 3 of the member 1 further includes a pair of slots 9 located above the holes 8 and each aligned with a respective reference point 6, the slots 9 being adapted to receive and hold the hooked end portion of a steel tape measure.

To use the above described wheel alignment gauge for measuring the alignment of a pair of wheels, for example the front wheels, of a vehicle, it is first necessary to remove from the wheel any potentially hindering wheel trim.

Each member 1 is then secured to the outer part of a respective wheel (as shown in Fig.

7) such that corresponding reference points 6 are aligned respectively in front of and behind the wheels and substantially parallel to the line joining the centres of the wheels, the dimensions of the members 1 being such that the line of alignment of the reference points 6 is not obstructed by the car underbody. The member 1 is fitted to the lower part of the wheel rim with the edges of the extended part 5b of the upper arm portion adjacent the alignment points 7 abutting the wheel rim.

The member 1 is firmly secured in position by stretching an elastic strap around the inner part of the wheel and securing the hooked ends through the holes 8 of the member.

The distances between the reference points 6 aligned in front of the wheels, dl, and between those aligned behind the wheels, d2, are then measured, for example using a steel tape measure calibrated in centimetres, hooking the end of the tape measure into an appropriate slot 9. By substracting d1 from d2 a distance d3 is obtained that is proportional to the toe-in alignment a0 of the wheels. It can easily be shown that a equals the distance da measured in centimetres to a close approximation. (If da and a have negative values this indicates toe-out alignment of the wheels). If the measured wheel alignment is required as a distance referred to the wheel rim diameter, conversion can easily be effected by multiplying da (in centimetres) by the rim diameter (in centimetres) and dividing by 57.3. The measured value of the alignment of the wheels can then be compared with the recommended alignment for the vehicle in question.

It is found that a member having the above described dimensions is suitable for use on a wide variety of vehicle wheel configurations.

In a modification of the above described wheel alignment gauge, illustrated in Fig. 5, the ends of the central portion 3 and lower arm portion 4 are cut away with respectively downwardly and inwardly inclined edges, the upper arm portion 5 thus having extended ends on which the reference points 6 are located, facilitating access thereto.

In an alternative embodiment of the present invention (Fig. 6) planar extension 2 of upper arm portion 5 has a central recess 10 giving two centrally disposed reference projections 11, 12 which co-operate with the wheel rim to accurately locate the member. Projections 11 and 12 also serve to support the member securely and recess 10 prevents hindrance due to hub caps, wheel nuts, etc.

Upper arm portion 5 also has extensions on each extremity, such as projection 14. This projection provides a convenient reference point and an easy reading of a tape measure, such as measure 15.

Lower arm portion 4 has a central projection which in use provides substantially single point contact with a road wheel tyre. Tyre profiles and surfaces do thereby not disturb placement of the member. Projections 11, 12 and projection 16, in co-operation respectively with a wheel rim and tyre in use provide straightforward and accurate location, together with secure support for the member.

Claims

1. A wheel alignment gauge comprising a pair of substantially rigid members each having a pair of equally spaced reference points and being adapted to be supported substantially perpendicularly to the axis of a vehicle wheel and having location means co-operating with the wheel such that corresponding reference points of the members are aligned respectively in front of and behind wheels whose alignment is to be gauged and substantially parallel to the line joining the center of the wheels; the spacing of the reference points on each member being substantially 57.3 measurement units such that difference in distance between respective pairs of reference points in front of and behind the wheels expressed in measurement units is equal to toe-in or toeout wheel alignment expressed in degrees.

2. A wheel alignment gauge as claimed in claim 1 and wherein location means is provided by two projections arranged to co-operate with the wheel rim.

3. A wheel alignment gauge as claimed in claim 1 or claim 2 and wherein the reference points are provided on extended end portions of each member.

4. A wheel alignment gauge as claimed in any preceding claim and wherein each member is formed as an elongate channel.

5. A wheel alignment gauge as claimed in claim 4 and including an upper arm portion having a centrally located extension surface, the major free edge of which is adapted to abut a wheel rim.

6. A wheel alignment gauge as claimed in claim 4 or claim 5 and including a lower arm portion having a centrally located projection.

7. A wheel alignment gauge as claimed in claim 4, claim 5 or claim 6 and wherein a channel arm portion extends away from the channel at an angle greater than 90" to facilitate the nesting of members.

8. A wheel alignment gauge as claimed in any preceding claim and adapted to receive elastic strap or rope which in use extends around a wheel to provide support.

9. A wheel alignment gauge as claimed in any preceding claim and including adjacent a reference point a slot adapted to receive and hold the hooked end of a tape measure.

10. A wheel alignment gauge as claimed in any preceding claim and including additional markings to attract the attention of a user to the reference points and location means.

11. A wheel alignment gauge as claimed in any preceding claim and wherein either or both members carry alignment related information.

12. A wheel alignment gauge substantially as hereindescribed with reference to the drawings.