Axle shims

Squeezing out those last few tenths

Axle shims

Postby wixwacing » Sat 19 Jul, 2008 12:04 am

AXLE SHIMMING


Angle winders have been round for a long while now and are ever more popular in the design of modern RTR slot cars. In the case of traction magnet racing it allows the magnet to be put in the definitive spot. Not too close to the rear axle and not too far up front. But as a result of the angle winder setup, there is a couple of side effects which aren’t the most desirable to have. One is having the extended armature shaft rubbing on the tyres and the other is a distinctive rattle caused by axle endfloat. The sound is prevalent in a lot of Scalextric cars and is not unheard of in some other leading makes.


The noise is caused by the axle slopping from side to side during cornering. On a normal in line set up, the axle is held centrally by the extended armature running in the centre groove of the contrate gear. Any side play is absorbed by the contrate running against the armature. On an anglewinder the side play is usually controlled by the wheel and spur gear touching the axle bearings. In the case of there being excess side play, the axle will slap quite noisily against one bush then the other during hard cornering.


‘Til now, like many others, I have been inserting small steel washers between spur gears, wheels and bushes to reduce the play to a minimum. The degree of success is hoping the washers are thin enough to get a snug but not tight fit. Well now I’ve decided to come at this phenomenon from a different angle. The reason being that in an effort to reduce the racers worst nightmare, loose wheels, manufacturers are resorting to ever tighter fitting wheels and some of the market leaders are even putting coarse knurling on the ends of the axles. This is fine for keeping the wheels on, providing you don’t remove them for shimming.

Once these wheels are removed they usually leave a considerable amount of wheel plastic behind on the axle. No need to tell you what this means. Wheels will need to be glued back on and there will always remain the possibility they will choose to roam at some crucial moment in a race. I have decided that this is not for me and after a little bit of thought I have come up with a different approach which takes seconds, doesn’t harm wheels and can fine tune the shimming to the N’th degree.



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At some of the better hardware stores it’s possible to by a multi hole punch. This device is like a pair of pliers but it has six hole punches of varying diameters on one jaw and a brass anvil on the other. The technique is to firstly choose your selected plastic card thickness. I use .018” (0.45mm) as this will give me a minimum drag free gap of zero or .018” which is quite small.


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I draw a line along one edge in pencil, then cross it at intervals slightly larger than the overall spacer diameter. Using the punch closest to 3/32” I punch all the crosses as centrally as possible. I then go to the largest size and using the drawn crosses to centre the punch I then punch over all the holes already done.



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The washers created will actually pass up into the punch so then I can push them through with the shank of a snug fitting drill. As in the illustration, I have then created a set of plastic washers in .018” plastic card! The annulus is then cut through in one spot, creating a split washer. This washer can then be twisted and fitted over a complete axle assembly avoiding the need to pull wheels off!!



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As mentioned before, if you have a selection of plastic card you can make a whole bunch of ready to go washers and have something ready for your new angle winder. And you’ll be able to effect a cure in under a minute! Now isn’t slot life just getting better!! No more tentatively yanking hubs and consequential wobbly wheels.



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AND NO MORE RATTLY MODELS!
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When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
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