Wheel Sanding Techniques

[terryep]

Re: Measuring runnout.

With a mandrel how do you get it centered when the hole diameter varies? What if the hole is out of round?

Terry

[SPEEDBUGGY]

I WOULD FIND A NEW WHEEL.

[MaxV]

With a mandrel how do you get it centered when the hole diameter varies? What if the hole is out of round?

For the standard mandrel sold at hobby shops, etc., replace the existing screw with a #3-48 x3/4" Flat-head machine screw. This screw has a beveled head which will help ensure that the wheel is centered on the screw. (See drawing). It is also important to make sure the inside wheel hub is square to the wheel bore (the Pro-Hub tool can do this).

Another option is to get the Pro-Wheel Mandrel from Maximum Velocity, which has a beveled head.



By the way, when asked, Maximum Velocity includes one of the #3-48 screws in an order at no charge.

[Stan Pope]

The various mandrel solutions have fundamental assumptions which are not assured. Even the beveled head screw mandrel depends on the assumptions that the outer edge of the bore is symmetrical and that the inner face of the hub is square.

The paper solution that Terry posited goes right to the heart of the runout definition. As such, it avoids a lot of assumptions. In the course, it adds some assumptions which I think are more easily testable than those of the mandrel solution.

There are better mandrel solutions, but they are probably too specialized for this applicaiton.

[terryep]

Re: runout measurements.

Using a dial indicator I measured the vertical body movement of a well raced 2003 car near it's three landing wheels. The car was held down by hand onto a cast iron table and against a side stop (table saw fence) and a wooden block clamped to the fence for a front/back stop. Measurements were taken one wheel at a time as a piece of thin paper was pulled beneath to spin the wheel. Results:
Front Left +/-0.002",
Left rear +/-0.001",
Right rear +/-0.003"

It was necessary to keep the wheel up against the side stop and against the car body to prevent the wheel from moving sideways on the axle. (A problem predicted by Stan) I couldn't measure the inside of my bushing in the drill press with my dial gage but did measure on the outside of a drill bit to be +/-0.002" Paper thickness was <+/-0.0005".

This seems like a fool proof method for checking for a smooth ride!

Terry

[Stan Pope]

Front Left +/-0.002",
Left rear +/-0.001",
Right rear +/-0.003"

Cool! In fact, very cool! Good work!

Please clarify the measurement notation.

Do you mean by +/-0.002 that the dial varies from -0.002 to +0.002? This would be a runout of 0.004.

Or are you saying that the dial varies over a total range 0.002 for a runout value of 0.002?

[terryep]

Thanks Stan. That's a min and max measurement. So 0.006" from highest spot to lowest spot. This was not a smooth distribution on this wheel.... perhaps there was some debris in the plastic. I didn't want to mount a new set of wheels. I'll try it again in February.

Terry

[Stan Pope]

Thanks Stan. That's a min and max measurement. So 0.006" from highest spot to lowest spot. This was not a smooth distribution on this wheel.... perhaps there was some debris in the plastic. I didn't want to mount a new set of wheels. I'll try it again in February.

and

Front Left +/-0.002",
Left rear +/-0.001",
Right rear +/-0.003"

So the runouts would be
Front Left: 0.004"
Left rear: 0.002"
Right rear: 0.006"

Excellent work!

Consideration for next season: Borrow that gage again and try to get the bushing chucked for lowest possible runout. Might have to run some shim stock in around part of the shaft. It should bring the wheel runout down to "silky smooth".

[RACER X]

Even the beveled head screw mandrel depends on the assumptions that the outer edge of the bore is symmetrical and that the inner face of the hub is square.

These areas should always be adderessed first when prepairing wheels.

By creating a straight hub bores, all of the same size and squaring the hub face you have created or squared your starting dimensions for a proper wheel mounting and treatment.

There are now specialized tools for this.

[terryep]

RE: Specialized tools, yes this is true, there are... it would be cheaper just to buy prepared wheels and be done with it. I think there is merrit in finding methods that are assessable to most people. A drill press is a lot easier to get your hands on than a lathe and safer too. Cubs can learn a lot helping to make jigs (home made tools).

I'm tempted to bring up the fairness issue but then I'd be moving too close to the "dark side"

Terry