Hints for detecting lightened wheels?

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LightninBoy
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Hints for detecting lightened wheels?

Post by LightninBoy »

So I got roped into being a checkin judge for districts. Our rules do not allow lightened wheels - specifically the rules state that no material may be removed from inside the wheel surfaces.

I'm pretty sure I can tell the wheels that are significantly lightened. Does anyone have any suggestions for catching those that have maybe just a bit taken off? Can I look for machining marks? I don't plan to be uber strict about this and reject anything with .1 gram of material removed. But I do want warn those that may be pushing the boundary and provide a level field for everybody.

Thanks!
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Re: Hints for detecting lightened wheels?

Post by Speedster »

1.8 gram wheels will normally have the step removed and there will be a slight ridge on the inside of the wheel. You can feel the ridge with your fingernail. 1.4 gram wheels look thin and will feel spongy if you squeeze them. If the wheel is simply made round they will probably measure 1.170 although they can also measure 1.180. Not much you can do with these unless you have a 1.180 rule. That would stop the 1.170. I've heard some rules require the wheel measure 1.184. That would be a very strict rule.
I've never had anyone try to get a 1.4 gram wheel past me. I had one car with 1.8 gram wheels last year. There were several wheels measured 1.170 but as long as the outer step was not removed I let them go. Set a stock wheel in front of you so you can compare it to a suspect wheel.
Fortunately, most folks are honest.
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Re: Hints for detecting lightened wheels?

Post by Noskills »

Anyone lightening a wheel in a non-professional capacity will be obvious. I had a scout groove his wheels-looked like hamburger meat. As Speederster said there are 1.8 gm wheels where the outside rim looks full thickness but by putting a finger inside the wheel you can feel that material has been removed from the inside (leaving the outside rim full thickness).

So look for the obvious hack marks on the tread, super thin 1-1.4 gramers and use your finger on the inside lip to feel for the 1.8 grammers. IMO trying to comment on the second step with an axle in place is going to be tough to argue with a parent.

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Re: Hints for detecting lightened wheels?

Post by Stan Pope »

Regarding outer hub step removal ... unless it is forbidden by your rules, I would not worry about detecting step removal. Its effect on angular inertia in negligible (as is most near-axis material removal).

In fact, since the mass in the wheel does NOT participate in bore-axle friction, the increase in bore-axle friction that results from moving weight from the wheel to the body (in order to maintain total weight at 5.00 ounces) increases losses which offset the miniscule reduction in wheel angular inertia.
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Re: Hints for detecting lightened wheels?

Post by LightninBoy »

Thanks for the ideas!

Check in was actually kinda fun. Most cars could be passed with a glance. I had to pull out the calipers for a couple (our rules have diameter and tread width minimums). Mostly I just joked with the kids ... "Ok, now, be honest, is there a rocket engine in here?" ;-)

Our rules make it pretty easy. Step removal and coning hubs is all fine. Since we have minimum wheel diameter and tread width specified, that removes the subjectivity of language like "light sanding is allowed". Lightened wheels is really the only thing we clamp down on.
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Re: Hints for detecting lightened wheels?

Post by Speedster »

If Greg Dawes comes on here and tells me he runs 2.6 gram wheels on his Midamerica cars, I'm going to have a fit.
OK, kidding aside. I have always felt illegal wheels didn't get on a car by accident. I want to stop the adult cheater. If I can catch him once hopefully he won't try it again.
LightninBoy, what are your rules for diameter and tread width?
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Re: Hints for detecting lightened wheels?

Post by LightninBoy »

Speedster wrote:LightninBoy, what are your rules for diameter and tread width?
1.16 inch diameter. 7.5mm tread width. Both allow quite a bit of material removal.
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Re: Hints for detecting lightened wheels?

Post by Speedster »

Yes, those are generous rules. Thanks for replying.
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Re: Hints for detecting lightened wheels?

Post by TXDerbyDad »

Noskills wrote:Anyone lightening a wheel in a non-professional capacity will be obvious. I had a scout groove his wheels-looked like hamburger meat. As Speederster said there are 1.8 gm wheels where the outside rim looks full thickness but by putting a finger inside the wheel you can feel that material has been removed from the inside (leaving the outside rim full thickness).

So look for the obvious hack marks on the tread, super thin 1-1.4 gramers and use your finger on the inside lip to feel for the 1.8 grammers. IMO trying to comment on the second step with an axle in place is going to be tough to argue with a parent.

Noskills
As an academic exercise I've attempted internal material removal with my own lathe and tooling, and even with the "right" tools it's a non-trivial activity. To do it in a non-obvious way would require a purpose-ground tool, which is possible, but would be some effort to get it right.
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Re: Hints for detecting lightened wheels?

Post by TXDerbyDad »

Stan Pope wrote:Regarding outer hub step removal ... unless it is forbidden by your rules, I would not worry about detecting step removal. Its effect on angular inertia in negligible (as is most near-axis material removal).

In fact, since the mass in the wheel does NOT participate in bore-axle friction, the increase in bore-axle friction that results from moving weight from the wheel to the body (in order to maintain total weight at 5.00 ounces) increases losses which offset the miniscule reduction in wheel angular inertia.
Lately I've been considering the benefits of removing the outer hub step. Wouldn't it increase contact area with the hub? Wouldn't it be best to have it smoothed flat, since there is often a line in the step, but still there? I know at least one wheel vendor swears by reducing but not eliminating that step.
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Re: Hints for detecting lightened wheels?

Post by Stan Pope »

TXDerbyDad wrote: Lately I've been considering the benefits of removing the outer hub step. Wouldn't it increase contact area with the hub? Wouldn't it be best to have it smoothed flat, since there is often a line in the step, but still there? I know at least one wheel vendor swears by reducing but not eliminating that step.
I have not verified the following experimentally, but logic and physics strongly suggest that ...
combining gentle tapering of the underside of the axle head with removing enough of the step as to move wheel/axle contact to the innermost portion of the hub, i.e. as close as possible to the center of rotation, the braking leverage of hub/axle friction is minimized.

However, since wheels are subject to tipping on the axle at times, the remaining step, adjusted to barely clear the axle head, may serve to prevent excessive tipping, thus keeping the wheel in good orientation.
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Re: Hints for detecting lightened wheels?

Post by birddog »

I was an inspector for our District Derby this year for the first time and we have similar rules about not allowing wheel modifications. Our rules also added minimum dimensions this year to make the rule more inspect-able. We have 1.180 diameter limit and 0.360 width limit. These limits are inspected with a "go / no-go" gauge sold by Maximum Velocity. This was the first year with this rule in place to help us "catch" folks who may not have been following the rules.

Out of about 50 entrants, we had 2 cars come through with lightened wheels. One was the 2 time reigning district champ. The "go / no-go" gauge caught the wheels and it was obvious. All I did was show the parent that the gauge fit over all 4 of his wheels and then showed him the rule and told him he would have to replace his wheels.

He replaced the wheels on 2 cars (he had 2 sons in the race) and still ended up getting 2nd and 4th place, so this person knew what he was doing.

Funny thing was, he said "these are the same wheels we used last year". They were illegal last year too, we just didn't catch them.

Interesting experience. I'm interested in shoring up our rules to ensure that we can also catch folks who are able to shave the inside diameter of the wheel and still keep the outside diameter at 1.180.

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Re: Hints for detecting lightened wheels?

Post by Stan Pope »

birddog wrote:birddog
While I really like the concept of a measureable standard for inspection, I am concerned that such precise standards introduce some requirements:
(1) Anyone who "works" the tread must arrange to test that their work has not exceeded the limit.
(2) The gages used for testing must themselves be certified periodically to assure that they conform to the rule and that normal wear and/or abuse has not altered them.

Few organizations are up to recertification, and only the most serious participants are equipped to test their work. Accordingly, we have limited wheel diameter by referencing it to wheel features which must be present, and allowing no tread width reduction by inspecting comparing to an unworked wheel.
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Re: Hints for detecting lightened wheels?

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Few organizations are up to recertification, and only the most serious participants are equipped to test their work. Accordingly, we have limited wheel diameter by referencing it to wheel features which must be present, and allowing no tread width reduction by inspecting comparing to an unworked wheel.
Given the Maximum Velocity test gauge is made of aluminum and the wheels are made of plastic, I suspect it would be a very long time before any "re-certification" would be necessary, if ever.

Stan, can you share the text of your rule which limits wheel diameter by referencing it to wheel features which must be present? I'm not following that one.

Also, inspecting the "no tread width reduction by inspecting comparing to an unworked wheel" seems much more error prone than just using an aluminum test gauge to check it. Not even sure how you would do the comparison (eye ball it, feel it with your hands some how)?

thanks,

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Re: Hints for detecting lightened wheels?

Post by Stan Pope »

birddog wrote:
Few organizations are up to recertification, and only the most serious participants are equipped to test their work. Accordingly, we have limited wheel diameter by referencing it to wheel features which must be present, and allowing no tread width reduction by inspecting comparing to an unworked wheel.
Given the Maximum Velocity test gauge is made of aluminum and the wheels are made of plastic, I suspect it would be a very long time before any "re-certification" would be necessary, if ever.

Stan, can you share the text of your rule which limits wheel diameter by referencing it to wheel features which must be present? I'm not following that one.

Also, inspecting the "no tread width reduction by inspecting comparing to an unworked wheel" seems much more error prone than just using an aluminum test gauge to check it. Not even sure how you would do the comparison (eye ball it, feel it with your hands some how)?

thanks,

birddog
From 2013 Wotamalo Rules:
"T-6. Wheel Treatment: Wheel treatment (material removal, smoothing, and polishing) may only affect the wheel bore, hub faces, outside tread surface and inside tread edges that might rub the guide rails. Wheel tread surface must be cylindrical and no narrower than the original wheel tread surface. Some of each of the original “tread marks” on the wheel face must be intact."

Sadly, plastic wheels are not the only objects (or materials) to which a (soft) aluminum gage may come into contact over the years. Recertification protects organizers and participants against all sources of gage variation.

For wheel tread width, eyeball comparison is adequate. If it is enough to matter, your eyes will detect it when the treads are held against each other.
Stan
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