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Laser Toe-in tool initial concept
britishtrident - 21/12/05 at 01:45 PM

Play around with this concept guys --- nothing ground breaking based on old Dunlop tool.

MikeP - 21/12/05 at 02:07 PM

Very slick. What's the easiest way to calibrate it?

britishtrident - 21/12/05 at 03:24 PM

Simple way is just to touch each half directly together and zero set it by adjusting the pads, but as the accuracy increase the futher apart the two halfs are using anything with close to parallel edges like an old door or table top. I have an old Ikea "Lack" table in workshop that has very precise right angled corners and parallel sides.

Calibriating to to give reading in degrees can be done either with simple trig to create a scale using a CAD program or by working using shims spacers between the pad and the wheel.

With a Locost the main interest is in the range parrallel to 1/16" so using shims it would be easy to generate a scale.

[Edited on 21/12/05 by britishtrident]

tks - 21/12/05 at 06:49 PM

i would make something up with cad..

because on each wheel you have also another setting and that will manage your results enormous, sow i'm afraid that
it won't work.

for example..if you steer tot he right your right wheel whil get an angle..
if both wheels hub settings aren't the same (castor i think it is called) then your laser beam will be showing another planet..

also the pressure etc. should be same..for the high..

wy not invent some system wich you can screw to the plane side of the rubber?

wich you then nivellate then you have onse side 90degrees...

Tks

britishtrident - 21/12/05 at 07:58 PM

quote:
Originally posted by tks
i would make something up with cad..

because on each wheel you have also another setting and that will manage your results enormous, sow i'm afraid that
it won't work.

for example..if you steer tot he right your right wheel whil get an angle..
if both wheels hub settings aren't the same (castor i think it is called) then your laser beam will be showing another planet..

also the pressure etc. should be same..for the high..

wy not invent some system wich you can screw to the plane side of the rubber?

wich you then nivellate then you have onse side 90degrees...

Tks


This type of optical lever is how optical tracking tools work, the Dunlop tool has been in use since at least the 1950s, and still used by many garages and small racing teams. Laser was a refinment added in the 80s, pervious to that it used a prisim and columating telescope/periscope arangement.

Its also the exactly way the dunlop gauge is put in contact with the wheel -- each side is just pushed against it -- either the rubber or the rim it dosen't matter much as long as it is symmetrical.

Putting real car dimensions into to the trig equations --- fairly typical FWD road car toe-out of 3mm deflects the image reflected laser beam about 12mm. With a typical Locost set up it would be set to 0 to 2 mm toe in it would deflect the beam 0mm to 8 mm.


If the car toe setting before adjustment is way off scale it dosen't matter as long as it is known what direction to adjust in to bring it on to scale --- with a laser this is pretty obvious just by looking at the general direction of the reflected beam.



[Edited on 21/12/05 by britishtrident]

britishtrident - 21/12/05 at 08:11 PM

Here is a link to the Sealey copy of the Dunlop tool

http://www.justoffbase.co.uk/s.nl/sc.9/category.200/it.A/id.5156/.f

Here is the non-laser version

http://www.justoffbase.co.uk/s.nl/sc.9/category.200/it.A/id.6144/.f

tobymack - 22/12/05 at 08:49 AM

having used a dunlop gauge and bits of string I much prefer the string box method.

With the dunlop it is difficult to ensure both wheels are straight ahead, any turn on them and the measurement goes to pot. This is particularly true if your bodywork or rear wheels are offset compared to the chassis as you have nothing accurate to visually align the front wheels against.

What is wrong with string?