Reducing wheel weight

[dad&3boys]

What is the best way to remove material from the inner part of the wheel?

I have a drill press, Dremel with stand, and all the Derby Worx tools. No lathe nor can I get one (already spent the pinewood derby budget for the next three years ;D).

Thanks.

[speedie4u]

Well you might try this. keeping in mind that the best way is with a lathe.

The pro wheel mandrell in a drill press. then using a dentist dental set, those small and angled picks can get in there. gonna take some patience and hard work, so keep that in mind.

Another way to try is a small exacto knife blade. A straight one. A angled one will not work very well. This issue usually the size of the blade and trying to get into the inner side wall.

you could also try taking a feeler gauge that is strong and thick enough to not bend. Then gring and reduce the thickness so it will fit into the area with easy. and then also grind a cutting edge on it.

Perhaps someone who has done them before, lathe or by drill press can post a few pics of the tools they use.

The biggest issue I had was not letting the turning of the wheel, kick up the blade or gauge the surface. Steady and even pressure is the key.

Perhaps a homemade jig of some sorts would also help.

Speedie4u

[JustaDad]

Jan 7, 2009 10:30:24 GMT -6 dad&3boys said:

What is the best way to remove material from the inner part of the wheel?

I have a drill press, Dremel with stand, and all the Derby Worx tools. No lathe nor can I get one (already spent the pinewood derby budget for the next three years ;D).

Thanks.

I've been debating using a cross-sliding vise with a drill motor mounted on its side. Chuck up the wheel in the wheel mandrel and go slow. The theory being that you can hold the tool tight and steady and move the cutting head with a greater degree of precession. A poor mans lathe. ;D Just not sure it will work.

You can get the vise at Harbor Freight cheap enough but it will need to be mounted to a board or the bench to be effective.

Let me know if you try it, I spent my PWD budget on tungsten

Good Luck!

[shadetreeracing]

Jan 7, 2009 18:06:38 GMT -6 JustaDad said:

Jan 7, 2009 10:30:24 GMT -6 dad&3boys said:

What is the best way to remove material from the inner part of the wheel?

I have a drill press, Dremel with stand, and all the Derby Worx tools. No lathe nor can I get one (already spent the pinewood derby budget for the next three years ;D).

Thanks.

I've been debating using a cross-sliding vise with a drill motor mounted on its side. Chuck up the wheel in the wheel mandrel and go slow. The theory being that you can hold the tool tight and steady and move the cutting head with a greater degree of precession. A poor mans lathe. ;D Just not sure it will work.

You can get the vise at Harbor Freight cheap enough but it will need to be mounted to a board or the bench to be effective.

Let me know if you try it, I spent my PWD budget on tungsten

Good Luck!

I've done that; before one could buy lightened wheels, but I sharpened a flat blade screwdriver shaved the inside of the wheel with drill going very slow got them to about 2 grams ;D

[JustaDad]

Thanks for the feedback STR. It is good to know the concept works. In our Dads class we can only use what came in the kit except the weights, so we get pretty crazy on the wheels.

[dad&3boys]

OK. Found a pretty decent method. Chuck the wheel using the pro mandrel in the drill press. Chuck a modified dremel cutting bit (see details below) in a hand drill (reverse the direction so wheel and bit are moving in opposite directions). Lightly move the cutting bit into the inside of the wheel (against the underneath side of the tread, not the side wall). Shaves the plastic out very easily and cleanly. Once you make your initial cut, it becomes somewhat tedious in taking the mandrel out of the drill press and weighing it along with the wheel (don't need to remove the wheel from the mandrel, just weigh the two together to determine the weight reduction).

Modified dremel cutting tool - Don't have it in front of me, but I believe it was a Dremel #196 High Speed Cutter bit which I shortened using a grinder so the cutting portion would fit inside the wheel cavity and still leave a lip on the inside part of the wheel for strength. Note - the 196 cutter originally cuts on both the sides and the tip as well; grinding it down to shorten the cutter removes the ability to cut with the tip.

Also, next time I plan to try chucking the wheel in my Dremal (mounted horizontally in my Dremal drill press) at the slowest speed and see if I can mount the cutter in something that is in a vise to have a little better control of the cut. Don't know that this will be any better but doesn't hurt to experiment.

One question - what would be an acceptable weight variation between wheels to maintain good performance?

Thanks.

[khouse]

What I do is lay my bench top drill press on it's side. Make it level with whatever you have. Now you have just made a modified lathe! Next take a small strait blade screwdriver and sharpen both sides and end with only about 5 degrees of rake. Chuck up your Pro Wheel mandrel on the big part of the shaft. Using the smaller part doesn't work well and you will get more chatter. Use the screw driver to basically "scrape" the material off the wheel. You will find the sweet spot that will really remove the plastic fast. Then use my K-groove to adjust your axles. Good luck!

[the woodbutcher]

Khouse, you're right on it. A small regular screwdriver is a common thing to most tool boxes and they can be modified into specialty tools. What you have described is basically a small scraper that can reach inside the wheel. If you wanted to make a more specialized tool for the job, any woodworking store carries cabinet scrapers. Tool grade steel that can be shaped with a file, flat and they usually are about 3" x5" in size. The secret to a good scraper, however, is the 'hook' on it's edge. Basically, the edge is square to it's sides and you use a burnishing tool (a hard rod, I think the side of a screwdriver could possibly work) at a 5 deg angle and form a very small lip from rubbing it across the edge. The steel kind of hooks over and that is the sharp edge that cuts.
You could make any shape, size, etc. and because it's flat it would clamp into the sliding vise for better control.

[hotrod]

I have clamped my cordless variable speed drill upside down in my vise with a wheel mounted with the inside of wheel facing out. To control the speed, I used black electrical tape wrapped the trigger. It worked best with a slow speed. Once you find the best speed, you just unplug when you are ready to check work. Cutting tools included file point grounded with cutting edge for inside tread area, tool grade cutters like used on mini lathes. I purchased a left hand and right hand cutter from Harbor Freight (the cheap ones). One worked better next to the hub while the other worked better next to the tread surface. Can't remember which is which... my memory is not what it used to be but, it wasn't great to begin with.

It did not take long to figure out the best angle and drill speed for cutting plastic. I was able to get pretty decent wheels in the 1.8 - 2.0 gram range. The KEY is not to get in a hurry and have a lot of patience. Good Luck.

Ed