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WORKSHOP EQUIPMENT
Page 85
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Page 87
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WHEEL ALIGNMENT GAUGES
A/ICING the correct steering geometry is ally an all-important and relatively complex .cise of the vehicle designer. Vehicle Lrol is likely to be impaired, particularly ligher speeds, if the geometry is incorrect, the rate of tyre wear will be accelerated in eme cases up to five to 1 0 times the normal . The rate of component wear may also be eased.
teering gear components are highly vulible to damage by obstructions or flying les and damage may go unnoticed even in the parts are checked by an experienced :hanic. Cases are common of vehicles ;ring long distances over an extended od with a dangerous steering fault that is extremely costly in terms of tyre wear.
is particularly important that steering metry be checked (and any errors ected) when the front-end components a been overhauled or repaired, whether or the vehicle has been involved in an accit. In the event of an accident involving a ity impact to any part of a vehicle and assitating major repairs, the operator is advised to have the alignment of the rear :els checked—in fact all the wheels in the ; of a multi-wheeler—before the vehicle is en on the road. A check revealing misnment of an axle may well enable a fault to rectified fairly cheaply which otherwise iId have resulted in serious mechanical lage if the vehicle had been driven on the he most common steering-geometry fault incorrect toe-in/toe-out of the wheels. mally the wheels are set with a slight toe-in that the clearances in the steering gear "taken-up" by the drag of the tyres when vehicle is travelling and the wheels run on Mel lines. If, however, the vehicle has t-wheel-drive the wheels are normally with a small amount of toe-out to cam;ate for traction when power is transmitted le tyre. Checking the toe-in and toe-out appears to be a simple exercise in that it comprises measurement of the distances between the wheel rims (or tyrewalls) at the front and rear and the comparison of these distances. It is, however, an exercise that requires meticulous care and the use of an accurate instrument. An error of Oin. in the case of a light vehicle may increase tyre wear very considerably, and excessive toe-in may cause serious wheel wobble at critical speeds. While excessive toeout causes very rapid tyre wear it normally stabilizes the steering.
While toe-in/toe-out can be adjusted by varying the effective length of the track rod, the remaining steering-geometry "settings" are a function of axle alignments which cannot be adjusted manually. These comprise camber, caster, kingpin inclination and toe-out-onturns, If there is no undue wear in the parts, if the axle assembly has not been overhauled and if the vehicle has not been involved in an accident, it can generally be assumed that these settings are correct. But assembly faults at a factory are not unknown and checking all the settings is often a worthwhile exercise in the case of a new vehicle. It can also be recommended as a routine maintenance exercise, say, every six months or so.
Camber and kingpin-inclination angles are inter-related in that they are combined to give a point of tyre/road contact the position of which does not change by more than a small predetermined amount when the wheels are steered. For the lightest possible steering the angles would be arranged to give a point of contact that would not vary with movement of the steering, but this would eliminate the small amount of drag in the system that promotes stability.
The kingpin is angled in the longitudinal plane so that its centre line would pass through a point on the road ahead of the point of tyre contact to provide a self-centring action. While this gives easier vehicle control and promotes stability excessive caster is a common cause of wheel wobble as well as rapid tyre wear. The caster angle can be varied by relocating the axle relative to the springs and may be affected by the condition of the springs.
When the vehicle is negotiating a curve the inner wheel travels on a smaller radius than the outer wheel. It is therefore necessary to design the steering gear to provide for this difference in order to avoid tyre scrub (and squeal) on a curve. If one or both of the steering arms to which the track rod is connected is An indication of misalignment can readily be obtained with the aid of an instrument placed on the floor which registers side thrust of the tyre when one of the front wheels passes over a tread plate. If the steering is correctly aligned there is little or no side thrust, whereas excessive misalignment produces a substantial thrust. A vehicle can very quickly be checked for misalignment with such a gauge but it does not indicate the cause or causes of misalignment. wheel-mounted bar is located under the vehicle and the scale and pointer mechanism is located on the bar. The end pads of the bar bear on the inside of the tyres; adjustments to the track rod can be made with the bar in position.
DENTLINE MANUFACTURING CO. LTD.
27 Broomgrove Road, Sheffield 10,
THE TOE-IN/TOE-OUT alignment gauge produced by this company comprises two lightweight telescopic stands that are positioned on opposite sides of the vehicle. A lower bar is placed in each case in a horizontal position with the aid of a spirit level, the upright is located in a vertical position and fingers on the bar are moved outwards until the notched ends grip the rim. Notched T bars attached to the top of the uprights are parallel to the lower horizontal bars and alignment is checked by bent or is of the incorrect length toe-out on-turns will probably be excessive.
It is possible to make accurate measurement of caster and kingpin inclination with the vehicle standing on a flat floor because the tilt (or camber) of the wheel changes in two different planes when the wheel assembly is rotated round the kingpin with movement of the steering wheel. The wheel tilts to an increasing negative extent (inwards at the top) because of the caster angle as the assembly is turned inwards, whereas it tilts positively about a central neutral axis when the assembly is moved in either direction from the straightahead position due to the inclination of the kingpin. Camber is checked by measuring the tilt of the wheel in the neutral position and may be positive, negative or zero.
In the following short review of some of the better known types of alignment gauge, the names of the companies are given in alphabetical order to avoid the difficulty of classification in order of importance. It is pertinent that the simple toe-in/toe-out gauge is an extremely useful tool if it enables measurements to be made reasonably quickly and accurately, a number of re-checks being normally necessary when the tracking of the wheels is being reset. Whereas gauges of this type can be bought for a few pounds, the more complex "comprehensivegauge may cost many hundreds of pounds'.
London Road, Deventry, Northants
TWO MODELS of an optical alignment gauge, specially designed for trucks and buses, are marketed by this company and are of Danish origin. The gauge is known as the Optoflex and is complementary to the company's VLC Portaflex portable optical wheel gauge, a mechanical type of instrument called the 121 LB and a track gauge. Churchill points out that the Optoflex can be used for checking distortion, toe-in/toe-out, camber and bearing play of the rear wheels as well as the front wheels, in addition to caster and so on of the front wheels. One model, the 122SH, caters for vehicles with an overhang of 1,440mm., and the other. the 122SL. for vehicles with an overhang of 2,750mm.
While the Optoflex incorporates adjustable background screens on to which the beams from the projection heads are projected, the screens and scales of the Portaflex are integral with the instrument. The Portaflex can be supplied with accessories that enable it to be employed for alignment checking of lorries and buses. Each of the three gauges features a turntable.
It is notable that the Portaflex can be used in conjunction with a pit or lift in addition to the normal flat-floor application, the turntables being recessed. While it is preferable to employ recessed turntables for the 121 LB steering gauge, they may be mounted on special wood ramps. a second set of ramps being employed for the rear wheels to raise them to the level of the front wheels.
The VLC track gauge measures the change of track width to give a toe-in/toe-out reading when the vehicle is rolled forward equivalent to half a turn of the wheels. The
measuring the distance between opposite notches at the front and between a rear notch on one of the bars and a scale on the opposite bar. This is performed with a telescopic gauge bar which can also be used to check the alignment of each wheel separately.
THE DUNLOP CO. LTD.
Fort Dunlop, Birmingham 24
A TOE-IN/TOE-OUT optical alignment gauge from this company is applicable to all types of vehicle. The recommended trade price of the equipment is £34.
The gauge comprises two separate horizontal bars which are placed on each side of the vehicle so that pointers connect with the wheel rims or tyre walls. On the end of one bar is a view box incorporating a thin vertical line and a large reflector plate. At the end of the other bar is a mirror and when a test is made, the end of the view box with its line plate is reflected back by the mirror. The view box is then pivoted to bring the line central with the vertical lines on the reflector plate. A pointer connected to the view box at right angles indicates the amount of toe-in or toe-out on a calibrated scale. A special T-piece adapter provides for alignment checks of vehicles with two steering axles.
A Dunlop camber/caster/kingpin gauge in fact comprises two gauges in addition to two turntables, the latter being equipped with run-on ramps. The first of the two gauges is held by hand against the tyre to measure camber: the second gauge is attached to the stub-axle or wheel for measurements of caster and kingpin inclination. In addition to facilitating measurement of caster and kingpin inclination, the turntable can be used for checking toe-out-on-turns.
ERATION of the toe-in/toe-out gauge Juced by Elms Garage depends on 'bon of the front wheels as the vehicle is red forwards. The ends of the external arms of the gauge are attached to the
s by means of adjustable clamps; one of arms is equipped with a pointer-and-scale ge and this registers the amount of toepr toe-out when the vehicle is moved to I the wheels through 180deg. The internecting bar is fitted with rollers and it :laimed that alignment can be checked two minutes. Cost of the instrument is i 2s. 6d,
VCOCK ENGINEERING LTD.
ler Road, houses, ffield Optiline optical alignment gauge proed by Laycock's Garage Equipment sion gives an 8x magnification when it is 1 for checking toe-in/toe-out. A mirror ind the background screen reflects the t image back onto a scale mounted on projector head in each case and this bles the readings to be observed by the laanic while he is adjusting the steering ;hanism. When rear wheels are being cked. the image from the wheel-mounted actor is projected onto a scale held level 1 the centre of the front wheel by an rative. If the reading is the same on both :s, alignment is correct.
Vhen measurements are being made of lber, caster and so on of the front wheels, light image is projected onto scales on the kground screen. Floating turntables are med to give extreme sensitivity while -point mounting of the projectors on the :els offsets wheel discrepancies to a useful mt. Three large thumb wheels on the A plate of the projector enables it to be irately set on the axis of the road wheel.
he turntables may be located on each s of an existing pit, at the ends of the :ks of a vehicle lift or on extensions into unken pit. Normally they are recessed into garage floor.
k wheel-alignment indicator is also included the Laycock range of garage equipment. Front wheel is driven over a tread plate I if the wheels are misaligned a side .151 is imparted to the plate. Sidewards placement is registered on a gauge unted on a wall panel which gives a ding of side slip in feet per mile. If the :els are correctly aligned the result is tailed by a green light: a red light and a zer give a signal of misalignment.
EUMATIC COMPONENTS LTD.
s Street, ffield S company produces a toe-in/toe-out ge that is based on a wheel-mounted bar. lters are attached to steel tubes located he outer ends of the bar and are held into tact with the wheel rims on the outside an internal spring. A scale on the three-tube scopic bar gives readings of Oin. to 12in. icrements of .kin.
ESTI NG HOUSE GARAGE UIPMENT LTD.
lam Road, pwood, Bristol light-beam equipment produced by Ainghouse was specially designed for cking the steering and axle geometry of vy commercial vehicles, including twin-steer type and semi-trailer outfits. basic kit of the system costs £388, ch is increased to £504 if it is supplied four panels.