Obtaining matching wheel diameters after sanding/polishing?

[Derby Wizard]

If one is unable to achieve a process to do four at a time, I would suggest using a micrometer and just performing the steps such that a minimal amount is removed each time until they measure the same. This would probably require a few extra wheels if I tried it.

I would think doing four at a time is difficult unless a lathed tool/spindle that is true (and the hubs snugly fit to) is in your possession. I don't believe I have anything in the required length/diameter to mount four which is straight enough that I wouldn't get a very slight 'wobble' at the tip. Maybe I need a good drill press/chuck setup...

[Stan Pope]

Don't feel bad about burning a few extra wheels. The last youngster who cut wheels here took 7 tries, but he made it! He learned a bit. I didn't think that the cost of a few wheels was worth denying him that learning experience!

[DR Pine]

Stan

What would you reccomend as the finish/final sanding grit for wheels?
And do feel that this should be the last step possiably eliminating the polishing?

[Stan Pope]

Since I don't sand them, I'm hard pressed to recommend a specific grit sandpaper.

I don't recommend polishing.

The tread surface goal should be:
The tread feels smooth as you rub your fingernail around the circumference.
The tread feels rough as you rub your fingernail across the tread.

Why?

You want the wheel to roll smoothly (low rolling friction)
You want the wheel to resist sliding sideways (high sliding friction) to resist "coming loose" on the flat.

If you try to polish the wheel beyond spinning it against sandpaper, you will reduce the sideways sliding friction.

[DR Pine]

Stan

Very well explained!

Thanks

Of course I must ask the obvious what method do you use to achieve the desired result?

[Stan Pope]

Wheels turned against medium sandpaper should leave that kind of surface.

Turn with tool radius synchronized to feed rate is another way. You will have to work out the geometry for that.

[dmadman43]

Since I don't sand them, I'm hard pressed to recommend a specific grit sandpaper.

I don't recommend polishing.

The tread surface goal should be:
The tread feels smooth as you rub your fingernail around the circumference.
The tread feels rough as you rub your fingernail across the tread.

Why?

You want the wheel to roll smoothly (low rolling friction)
You want the wheel to resist sliding sideways (high sliding friction) to resist "coming loose" on the flat.

If you try to polish the wheel beyond spinning it against sandpaper, you will reduce the sideways sliding friction.

I feel sort of like those radio talk show callers... "long time listener, first time caller" This is my first post on the board, although I've been a lurker for quite some time and do appreciate all that I've learned from all of you.

Stan, while I have little reason to doubt you, based on your well exhibited and obvious experience and knowledge; do you have, or does there exist any quantifiable (sp?) tests or data showing the advantages/disadvantages of the polishing theory you posit? My son is convinced that polshing in addition to sanding will give him a concerted advantage. Moreover, there are a plethora of "speed tips" sites stating that polishing is a good idea, unless their definition of polishing is sanding with wet 600 grit sandpaper.

[Stan Pope]

Stan, while I have little reason to doubt you, based on your well exhibited and obvious experience and knowledge; do you have, or does there exist any quantifiable (sp?) tests or data showing the advantages/disadvantages of the polishing theory you posit? My son is convinced that polshing in addition to sanding will give him a concerted advantage.

I have not found a way to definitively test the "posit." When I quit polishing, the cars were less prone to the "death rattle" down near the finish line and won by a larger margin. There are just too many variables to claim proof.

Moreover, there are a plethora of "speed tips" sites stating that polishing is a good idea, unless their definition of polishing is sanding with wet 600 grit sandpaper.

That would be pretty coarse polishing!

I polished the tread up through early 90's and included that technique on my website. I subsequently removed it (at least I think that I have found all the places!)

I find my writings at various places around the internet and being handed out at various events. Sometimes my name is left on, but usually my authorship is omitted. It is possible that some of what you have read are old, unauthorized copies of my writing? Naw, probably not.

Rather than accept anyones claims of authority, ask you son to think through the process: What are the tread factors that affect a PWD car's speed? "Sliding friction in the direction of travel" is probably pretty low on the list. "Rolling friction" needs to be looked at, though. So ask him to think about what affects rolling friction. Variations in distance from hub bore to tread (called runout), causing the axle (and car) to bob up and down, is another factor. Consider the goal description I gave and how these interact to produce low rolling friction.

Then ask about the desirability of sliding. When is it okay for the wheels to slide? When not?

BTW, one of the last suggestions I give folks in my talks is to check out the hints that they gather. If they don't make sense, then either they are wrong or you have misunderstood!

Hey! it's 2 am here in Illinois! I gotta run for the sack!