GB2489428A

GB2489428A - Single Track Vehicle Wheel Alignment

Info

Publication number: GB2489428A
Application number: GB201105071A
Authority: GB
Inventors: Richard Arthur Lindsay
Original assignee: MOTOMETRIX Ltd
Current assignee: MOTOMETRIX Ltd
Priority date: 2011-03-25
Filing date: 2011-03-25
Publication date: 2012-10-03
Anticipated expiration: 2031-03-25
Also published as: GB201105071D0; GB2489428B

Abstract

A pair of laser light sources (1,2) is mounted to one wheel of a two-wheeled single track vehicle projecting beams (5,6) in planes parallel to and equispaced either side of its central plane and set to intersect targets (9,10) mounted to the other wheel. One beam is a small diameter parallel beam, the other is divergent about an axis parallel to said one beam and the corresponding targets comprise linear scales normal to said other wheel, having conventional and elongate markings respectively. Alignment is indicated by comparison of respective intersections when said one beam intersects its target scale and said elongate makings are parallel to the plane of the divergent beam. Light source and target mountings each comprise paired opposing supports (3,4 and 7,8) spanning a chord of the wheel, and means acting between supports to maintain them parallel and provide optimum clamping regardless of wheel width and operator input.

Description

I

Single Track Vehicle Wheel Alignment This invention relates to a method and apparatus for checking wheel alignment of two-wheeled vehicles such as bicycles and motorcycles. Two-wheeled single track vehicles, having a steered wheel rotatable about a first polar axis and about an orthogonal steering axis and a non-steered wheel rotatable about a second polar axis in a reference plane that bisects the tyre, require the non-steered wheel to be accurately aligned with respect to the steering axis such that the steering axis lies in the reference plane of the wheel.

Several methods for checking wheel alignment are known, in which means are employed to project a reference line parallel to the reference plane from a side of the non-steered wheel to the vicinity of the steered wheel. The steered wheel is rotated about its steering axis until its polar axis is normal to the reference line and the distance between the reference line and the wheel rim or tyre is measured. The process is repeated for a reference line projected equidistant from the opposite side of the non-steered wheel and the resulting measurements compared. If the measurements are different, a correction is applied to the orientation of the non-steered wheel and a further set of measurements obtained. The process is repeated until measurements obtained from each side of the wheel are equal, and correct alignment has been achieved. Such methods typically use straight edges or cords to project a reference line but the process is unwieldy, subject to inaccuracy and does not readily compensate for steered and non-steered wheels of different widths. Light beams are also employed to project a reference line but require additional means to set the orientation of the steered wheel polar axis, normal to the reference line, when measurements are taken. UK patent GB2343006 discloses one such method which utilises targets mounted each side of the steered wheel that intersect parallel light beams projected from respective sides of the non-steered wheel. Each target provides a calibrated array of parallel linear markings symmetrically disposed either side of the steered wheel and set normal to its polar axis. In operation, the light beams are caused to scan the targets by oscillation of the non-steered wheel, the steered wheel is rotated about its steering axis until the target markings are in alignment with the path of the scanning light beams and the intersection of each beam with its respective target is then measured and compared. The necessity to oscillate the non-steered wheel while monitoring the scanning of the targets is a limitation of the method, being both unwieldy to perform by a single operator and, in the absence of an integral centre stand, requiring specialist apparatus to elevate the wheel clear of the ground.

It is also known to employ laser line generators that project divergent planar beams, obviating the need to oscillate the wheel. However, this method is very sensitive to the planar alignment of the beams, and hence the mounting accuracy of the apparatus, any deviation resulting in errors dependant on the sector of the divergent beam employed during measurement.

For ease of application by unskilled individuals in the course of routine maintenance, it is desirable that apparatus for wheel alignment can be rapidly and accurately mounted and de-mounted, achieving optimum mounting conditions with minimal user input and irrespective of the width of the wheel.

Inappropriate mounting forces can result in deflection of the apparatus and degradation of its critical alignment. Simple elastic straps and threaded clamps are known to be employed but are clumsy to manipulate, inconsistent and dependent on the judgement of the operator.

It is the purpose of this invention to provide a method and apparatus for checking the wheel alignment of a two-wheeled single track vehicle that overcomes the limitations of the prior art, the method comprising projecting parallel first and second laser beams normal to the axis of rotation, and symmetrically disposed about the central plane of rotation, of one wheel to intersect respective first and second linear graduated scales axially aligned on a normal to, and symmetrically disposed about the central plane of rotation of, the other wheel wherein said first laser beam is a parallel beam, said second laser beam is divergent in the plane of rotation of said one wheel about an axis parallel to said first laser beam and the graduations of said second scale extend normal to the axis of the scale, further comprising the steps of: centralising the divergent beam with respect to its scale by positioning the first laser beam to intersect the axis of the first scale; rotating the steerable wheel about its steering axis until the extended graduations of the second scale are in parallel alignment with the divergent laser beam and recording any difference between measurements indicated by the intersections of the laser beams with their respective scales, representing wheel misalignment requiring correction.

The apparatus for checking wheel alignment in accordance with said method comprising first and second laser light sources configured to produce parallel and planar divergent beams respectively, means to mount the light sources to opposing sides of a wheel wherein the divergent beam is aligned with the plane of rotation of the wheel, the parallel beam is maintained parallel to the mid axis of the divergent beam and the beams are equispaced about the centre of the wheel, first and second calibrated targets comprising a linear scale and an array of parallel elongate markings respectively, means to mount the targets to opposing sides of the other wheel wherein said second target is set to intersect the plane of the divergent beam, the elongate markings are oriented normal to the axis of rotation of said other wheel, the linear scale is maintained on an axis normal to and bisecting said markings and the calibrations are equispaced about the centre of the wheel.

In one embodiment, said linear scale and elongate markings may comprise photoelectric transducers producing signals in response to illumination by the laser beams and the signals are received and analysed by a microprocessor configured to detect when the elongate markings are in parallel alignment with the divergent beam and record the calibrated intersections of the beams and respective targets.

The means to mount each pair of light sources and targets may comprise a pair of supports, chordally located either side of a wheel, to which the light sources or targets are attached, a clamp acting between the supports to secure the supports in contact with the wheel and alignment means to maintain the supports in parallel alignment.

Each support may comprise an elongate member spanning a sector of the wheel.

In a preferred embodiment the support may further comprise a plurality of fixing posts extending normal to the member and configured to engage with the rim of the wheel.

Fixing posts may be detachably mounted to the member and of alternative lengths to suit different wheel widths.

Each fixings posts may further incorporate a cylindrical buffer to interface with the rim of the wheel. The buffer may be rotatable about the axis of the post and the face of the buffer may incorporate a groove configured to engage the lip of the rim.

The position of the fixing posts may be adjustable lengthwise of the member.

Each fixing post may attach to the member by means of a collar slidably mounted to the member and a threaded locking screw acting between the collar and the member. In one embodiment the fixing post may be attached to the collar by means of a threaded connection which further acts to secure the collar to the member.

The clamp may comprise one or more ties detachably fixed between the supports and means to apply tension to the ties. In one arrangement, the ties may be elastic straps. In another arrangement the ties may comprise threaded rods and clamp nuts.

Alignment means may comprise one or more shafts linking opposing supports, slidably connected to at least one of the supports to permit variable separation and resist relative rotation of the supports.

In a preferred arrangement the clamp may act on the alignment means to limit the separation of the supports and apply a force acting to reduce said separation.

In one arrangement the alignment means comprises a plurality of parallel shafts fixed and projecting normal to one support and slidably engaged in close fitting holes in the opposing support and the clamp comprises a clamp body, locking means to afix the clamp body at variable positions to said parallel shafts, a clamp spring acting between the clamp body and the opposing support to reduce the separation of the supports to secure them in contact with the wheel, and an input configured to release the locking means and displace the clamp body to compress the clamp spring.

In a preferred embodiment the locking means is unidirectional, acting to resist expansion of the clamp spring.

Locking means may comprise a pair of locking arms, each having a bore slidably engaged with respective shafts, an unlocked state when the axis of the bore is maintained substantially in alignment with the shaft and a locked state when a torque is applied to rotate the bore normal to its axis, and each locking arm projects normal to its respective shaft and comprises a load application point offset of the shaft axis and abutting the clamp body and said torque is generated by the force applied to the load application point by the action of the clamp spring on the clamp body.

Each locking arm may further comprise an actuation point located between the load application point and the bore, and the input is slidably engaged with the clamp body for movement substantially parallel to the shaft axes to contact the actuation point and a force applied via the input to the application point in opposition to and exceeding the force at the load application point reduces the torque biasing the locking arm into the locked state and displaces the clamp body to further compress the clamp spring.

In the preferred embodiment, displacement of the locking means in response to displacement of the input is limited by contact with an abutment of the support and the locking means is oriented to the unlocked state by said contact.

In a further embodiment, movement of the clamp body with respect to the support is limited by a stop, displacement of the locking means is limited by contact with an abutment of the clamp body, and the locking means is oriented to the unlocked state by said contact.

The following is a description of a specific embodiment of the invention applied in accordance with the method to a motorcycle, reference being made to the accompanying drawings in which: Figures 1 to 5 are views of the apparatus mounted to a motorcycle.

Figures 6 and 7 are views of a pair of the supports mounted to a wheel.

Figure 8 depicts a support containing a clamp.

Figures 9 and 10 are views showing the components of the clamp prior to deployment.

Figure 11 is a view of the components of the clamp in the released condition with the input fully applied.

Figure 12 is a view of the components of the clamp in the deployed condition, acting to secure the supports to a wheel.

Referring to figures 1 to 5, laser light sources I and 2 are attached to elongate supports 3 and 4 respectively which are mounted to opposite sides of the rear wheel of a motorcycle. Light source I projects a small diameter parallel beam in the longitudinal axis of support 3 and light source 2 incorporates an optical lens to project a planar beam divergent about the longitudinal axis of support 4.

Calibrated targets 9 and 10 are mounted by means of supports 7 and 8 to appropriate sides of the front wheel to intersect beams projected by light sources I and 2 respectively. The targets comprise graduated scales extending outward of the wheel, normal to and similarly calibrated with respect to their supports. Target 9 comprises a linear scale and in target 10 the graduations are elongated normal the scale to form an array of parallel markings.

Referring in addition to figures 6 and 7, each support is mounted normal to the rotational axis and equispaced about the central plane of the wheel via a pair of fixing posts 13 projecting onto the rim of the wheel. The span between fixing posts is variable by means of collars 14 slidably engaged with the support to which the fixing posts are attached by means of threaded connections which further serve to clamp the collar to the support. Opposing supports are constrained to a common plane by alignment means comprising spaced parallel shafts 11 projecting normal from one support and slidably engaged with the other. Light source 2 is oriented with respect to its support such that the plane of its divergent beam is normal to said common plane. A clamp 12, whose function will be described in detail with reference to figures 8 to 12, is located within the slidably engaged support and acts between the alignment means and the support to apply a clamping force between the fixing posts and the wheel.

The clamp is rotationally symmetrical about a principal axis E-E and comprises a clamp body 15, locking arms 16, an input comprising a push-button 21 and attached slide block 22, and compression springs 20 acting between the clamp body and the support. The input is guided by pins 23 for axial movement with respect to the support and in turn constrains the clamp body to independent axial movement by means of a linear sliding connection 24 between the slide block and the clamp body. The locking arms are restricted to move in the plane D-D by the walls of the support. Each locking arm is in the form of a beam having an orthogonal bore 17 at its outer end which is a sliding fit on a shaft of the alignment means and a raised load application point 18 at the other end arranged to receive a force of the compression springs via an abutment 25 of the clamp body. The locking arm is configured to generate a clamping torque in response to said force wherein the reaction at the bore/shaft interface is sufficient to create a frictional resistance in excess of said force, thereby clamping the locking arm to the shaft.

Each locking arm further comprises a raised actuation point 19 located between the load application point and the bore to receive, via an abutment of the slide block, a force applied at the input. Forces applied to the actuation point act to oppose the clamping torque, reducing it to a magnitude insufficient to effect clamping and, if greater than the force exerted by the compression springs, moving the locking arms and clamp body to further compress the springs. The relative location of the load application and actuation points ensures that a residual clamping torque is maintained, priming the locking arms to resume clamping immediately an input force is released.

Deflection of the input to the limit of its travel applies maximum compression to the springs and orients the locking arms through contact with the internal wall of the support to align the bores with their associated shafts. Thus in this condition, depicted in figure 11, the locking arms are held in a fully unlocked state freeing the supports for application or removal. Progressive release of force from the input allows the locking arms to rotate in response to the said residual torque into the locked state, depicted in figure 12, wherein the clamp body is fixed with respect to the alignment means and the compressed springs apply a clamping force between the supports and the wheel.

The procedure for applying the specific embodiment in accordance with the method to align the wheels of a motorcycle comprises the following steps: For each pair of supports, collars 14 and associated fixing posts 13 are symmetrically positioned on a support at a span equivalent to the chordal distance of a sector of the wheel of typically 90-120 degrees and each is fixed in position by screwing the fixing post through its threaded connection with the collar to clamp against the face of the support. The positioning of the collars is replicated for the opposing support.

The supports incorporating light sources are mounted to the rear wheel as follows: the support bearing the shafts of the alignment means is positioned and held over a substantially horizontal span of the lower section of the wheel with the light beam projecting forwards, the fixing posts in contact with the wheel rim and the shafts passing between spokes of the wheel. The opposing support is positioned to receive the shafts of the alignment means and advanced toward the wheel until its fixing posts are also in contact with the wheel rim. The push-button of the input is depressed to the limit of its travel, compressing the springs of the clamp and applying contact pressure between support and wheel. When the push button is then released, the locking arms of the clamp assume their locked state in the manner previously described, the separation of the supports is fixed and the force exerted by the clamp springs is applied and reacted through opposing fixing posts to clamp the supports to the wheel.

The process of mounting the supports is repeated for the front wheel with the exception that the supports are inclined approximately 15 degrees to the horizontal to present a shallow projected view of the target surfaces in the general direction of the light sources.

By rotating the rear wheel or sliding the supports for the light sources around the wheel rim, the inclination of the parallel beam of light source I is manipulated until the beam intersects a point on the axis of the linear scale of target 9. The simultaneous intersection of the divergent beam of light source 2 with target 10 defines a line in the plane of the beam. The steering angle of the front wheel is adjusted to align said line with the elongate markings of the target and the intersection points of the beams with their associated calibrated scales are noted and compared. Any difference in the offset of the intersection points from the rotational plane of the wheel, as determined by the scale readings, represents a misalignment of the rear wheel to be corrected. Typically motorcycles include provision, such as jacking screws, for adjustment of rear wheel alignment. The process is completed by incremental adjustment and checking until alignment is achieved.

The apparatus is finally removed from each wheel by fully depressing the push-button of the input, driving the locking arms of the clamp into the unlocked state, and moving the supports apart until they are separated from each other and from the wheel.

It will be apparent to those skilled in the art that the invention would function equally effectively if mounted in reverse to the arrangement described, the light sources to the steered wheel and the targets to the non-steered wheel.

Claims

Claims 1. A method for checking the wheel alignment of a two wheeled single track vehicle having a steered wheel and a non-steered wheel whereby parallel first and second laser beams are projected normal to the axis of rotation, and symmetrically disposed about the central plane of rotation, of one wheel to intersect respective first and second linear graduated scales axially aligned on a normal to, and symmetrically disposed about the central plane of rotation of, the other wheel wherein said first laser beam is a parallel beam, said second laser beam is divergent in the plane of rotation of said one wheel and the graduations of said second scale extend normal to the axis of the scale, the method comprising the steps of positioning the first laser beam to intersect the axis of the first scale, rotating the steerable wheel about its steering axis until the extended graduations of the second scale are in parallel alignment with the divergent second laser beam and recording any difference between measurements indicated by the intersections of the laser beams with their respective scales, representing wheel misalignment requiring correction.
2. An apparatus for checking wheel alignment in accordance with the method of claim I comprising first and second laser light sources configured to produce parallel and planar divergent beams respectively, means to mount the light sources to opposing sides of a wheel wherein the divergent beam is aligned with the plane of rotation of the wheel, the parallel beam is maintained parallel to the mid axis of the divergent beam and the beams are equispaced about the centre of the wheel, first and second calibrated targets comprising a linear scale and an array of parallel elongate markings respectively, means to mount the targets to opposing sides of the other wheel wherein said second target is set to intersect the plane of the divergent beam, the elongate markings are oriented normal to the axis of rotation of said other wheel, the linear scale is maintained on an axis normal to and bisecting said markings and the calibrations are equispaced about the centre of the wheel.
3. An apparatus according to claim 2 wherein said linear scale and elongate markings comprise photoelectric transducers producing signals in response to illumination by the laser beams and the signals are received and analysed by a microprocessor configured to detect when the elongate markings are in parallel alignment with the divergent beam and record the calibrated intersections of the beams and respective targets.
4. An apparatus according to claim 2 or 3 wherein the means to mount each pair of light sources and targets comprises a pair of supports, located either side of a wheel, to which the light sources or targets are attached, a clamp acting between the supports to secure the supports in contact with the wheel and alignment means to maintain the supports in parallel alignment.
5. An apparatus according to claim 4 wherein each support comprises an elongate member spanning a sector of the wheel.
6. An apparatus according to claim 5 wherein each support further comprises a plurality of fixing posts extending normal to the member and configured to engage with the rim of the wheel.
7. An apparatus according to claim 6 wherein the fixing posts are detachably mounted to the member and interchangeable with fixing posts of alternative lengths to suit different wheel widths.
8. An apparatus according to claim 6 or 7 wherein each fixings post incorporates a cylindrical buffer to interface with the rim of the wheel.
9. An apparatus according to claim 8 wherein the buffer is rotatable about the axis of the post and the face of the buffer incorporates a groove configured to engage the lip of the rim.
1 0.An apparatus according to any of claims 6 to 9 wherein the position of the fixing posts may be adjustable lengthwise of the member.
11.An apparatus according to claim 10 wherein each fixing post is attached to the member by means of a collar slidably mounted to the member and a threaded locking screw acting between the collar and the member.
12.An apparatus according to claim 11 wherein the fixing post is attached to the collar by means of a threaded connection which further acts to secure the collar to the member.
13.An apparatus according to claim 4 wherein the clamp comprises one or more ties detachably fixed between the supports and means to apply tension to the ties.
14.An apparatus according to claim 13 wherein the ties comprise elastic straps.
15.An apparatus according to claim 13 wherein the ties comprise threaded rods and clamp nuts.
16.An apparatus according to claim 4 wherein alignment means comprise one or more shafts linking opposing supports, slidably connected to at least one of the supports to permit variable separation and resist relative rotation of the supports.
17.An apparatus according to claim 16 wherein the clamp acts on the alignment means to limit the separation of the supports and apply a force acting to reduce said separation.
18.An apparatus according to claim 17 wherein the alignment means comprises a plurality of parallel shafts fixed and projecting normal to one support and slidably engaged in close fitting holes in the opposing support and the clamp comprises a clamp body, locking means to affix the clamp body at variable positions to said parallel shafts, a clamp spring acting between the clamp body and the opposing support to reduce the separation of the supports to secure them in contact with the wheel, and an input configured to release the locking means and displace the clamp body to compress the clamp spring.
19.An apparatus according to claim 18 wherein the locking means is unidirectional, acting to resist expansion of the clamp spring.
20.An apparatus according to claim 19 wherein the locking means comprises a pair of locking arms, each having a bore slidably engaged with respective shafts, an unlocked state when the axis of the bore is maintained substantially in alignment with the shaft and a locked state when a torque is applied to rotate the bore normal to its axis, and each locking arm projects normal to its respective shaft and comprises a load application point offset of the shaft axis and abutting the clamp body and said torque is generated by the force applied to the load application point by the action of the clamp spring on the clamp body.
21.An apparatus according to claim 20 wherein each locking arm further comprises an actuation point located between the load application point and the bore, and the input is slidably engaged with the clamp body for movement substantially parallel to the shaft axes to contact the actuation point and a force applied via the input to the application point in opposition to and exceeding the force at the load application point reduces the torque biasing the locking arm into the locked state and displaces the clamp body to further compress the clamp spring.
22.An apparatus according to claim 21 wherein displacement of the locking means in response to displacement of the input is limited by contact with an abutment of the support and the locking means is oriented to the unlocked state by said contact.
23.An apparatus according to claim 21 wherein movement of the clamp body with respect to the support is limited by a stop, displacement of the locking means is limited by contact with an abutment of the clamp body, and the locking means is oriented to the unlocked state by said contact.