Pinewood Derby Car Mini-Lathe

[gpraceman]

I stumbled upon this on YouTube. It's an interesting concept that looks easy enough for a kid to use, under supervision. However, I have to wonder just how well it would work in practice.

It might have been better to have the tool focus on just working the wheels. Also doing the axles seems to have made the tool rather more complex.

http://pinewoodderbycarmini-lathe.com


https://youtu.be/

[ngyoung]

Properly turned wheels are cut to be true to the bore. Not sure how this tool locks all 4 wheels together. When finished they may all be the same diameter but the runout relative to the bore could end up worse then before. Maybe using the jig with 1 wheel at a time and a gauge pin properly sized for that specific wheel. It could have potential to be better then trying to use a mandrel chucked in a drill. As it is in the video I don't think it will help much beyond giving all 4 wheels a light sanding at the same time.

[Vitamin K]

I don't really see any mechanism for centering the wheel(s) on the pin? If that's the case, I don't see how you're going to improve runout much.

[Speedster]

What if someone took a set of Maximum Velocity's 4091 wheels and axles and got a time on them on a 3 wheel rail rider. Then took wheels from the same mold and did no machining to the wheels. Would the difference in time be significant if the cars were traveling around 35' ? Since the wheels are all rolling on an edge I wonder if it makes any difference. I like to spin wheels in the balancer to see if any stop without rocking back and forth. Once in awhile a machined wheel will simply stop but it is rare.

[knotthed]

Speedster,

The 4091's would be lighter than stocks, so it would seem to reason that they would indeed be faster.

Is the root of your question around the quality of the wheel versus speed or to the weight of the wheel versus speed?

[Speedster]

My original thought was the quality of the wheel versus speed. However, you've brought up a point I totally forgot about. I have a stock wheel that weighs 2.55 grams and a 4090 wheel that weighs 2.40 grams. That would be a total of .45 grams for 3 wheels. That would still make a good test. I used the number 4091 originally because I'd like to see the test run with the 4094 axles. Since we are dealing with 2 things that should give the 4090 wheel the advantage, how much of an advantage is it? Or, is it any advantage?

[gpraceman]

Speedster,

Is your question relating to the mini-lathe tool? I don't mind when people get off topic, but I thought that you might be posting to the wrong thread, as it didn't seem to relate.

[Speedster]

My thoughts are on the Mini-Lathe tool. From what I can tell, a raw USA wheel is concave. The inside edge tends to measure larger than the center. When I lay a straight edge over the wheel and shine a bright light toward me, I can see light at the center of the wheel. We're going to run the wheel on the inside edge with Negative Cant. If someone with a very accurate tool could measure the run out of the inside edge of the wheels before anything was done to them and then again after they were sanded, we'd know if the Mini-Lathe made them better, worse, or no change. When I turned a wheel in my calipers it measures 1.182 all the way around. It's difficult for me to believe an inexpensive tool can improve on the edge of a raw wheel. The middle of the wheel will not touch the track so we need not be concerned about the middle area. I mentioned running the wheel against a vendors wheel that was made only round. If there is no difference in performance between the two wheels at that level I doubt we can improve on the wheel with a simple tool. It's a cute tool. As long as it doesn't make a wheel worse I'm sure scouts would have Lots of Fun with it.

[Vitamin K]

My thoughts are on the Mini-Lathe tool. From what I can tell, a raw USA wheel is concave. The inside edge tends to measure larger than the center. When I lay a straight edge over the wheel and shine a bright light toward me, I can see light at the center of the wheel. We're going to run the wheel on the inside edge with Negative Cant. If someone with a very accurate tool could measure the run out of the inside edge of the wheels before anything was done to them and then again after they were sanded, we'd know if the Mini-Lathe made them better, worse, or no change. When I turned a wheel in my calipers it measures 1.182 all the way around. It's difficult for me to believe an inexpensive tool can improve on the edge of a raw wheel. The middle of the wheel will not touch the track so we need not be concerned about the middle area. I mentioned running the wheel against a vendors wheel that was made only round. If there is no difference in performance between the two wheels at that level I doubt we can improve on the wheel with a simple tool. It's a cute tool. As long as it doesn't make a wheel worse I'm sure scouts would have Lots of Fun with it.

I think a tool like Fat Sebastian Industries Concentricity Gauge or Knotty Racing's Wheel Runout Gage would serve as a good test for such a tool.

I, too, am skeptical that you could improve the runout of a wheel in this manner, but I'd be very happy to be proven wrong!

[knotthed]

I find it a little funny internally, given what I was envisioning a couple of weeks ago.

I will share it here as I don't see the time available to get on it right away and maybe someone wants to pickup with it and see what they can make happen.

Now to my comments;The guy has a basically good idea, but I too think it falls a little short.

Now to my vision; Using a RC Motor Commutator lathe coupled with gage pins as to friction fit the bores and essentially be turning between centers on the gage pin. https://www.google.com/search?q=rc+moto ... B800%3B664

Maybe someone could throw the picture on here?

Vision challenges - driving the gage pin, axial movement of the gage pin.

Vision positives, good part location on the gage pin, turning between centers, the commutator lathe has a nice dovetail slide and it is very small and compact.

[ngyoung]

Whoa. Never knew about the RC lathe units. They even have wheel truing lathes. They seem to lock in the wheels with mandrels that slide on the spindle and secured with a screw.

[sporty]

When I seen the video.
I thought it appeared to be something they were selling. Are they selling this ?

I wondered. I did not see bearings where they were inserting the rod that they were connected to the cordless drill.

I had wondered if the rod was stiff enough not to flex. When having the sand paper and shims under the wheels to give good even pressure.

So depending on the cost of this tool if they are selling it. What the value of it Is.

If it can provide less run out or equal to a stock wheels run out. Then it has merit.
sadly they never showed checking any of the run out.

Sporty

[Speedster]

I received Knotty's Runout Gage yesterday. I'm very pleased with it. I already had the Pro-wheel Shaver. I have 2 sets of vendors wheels. One set is Derby Evolution "Revolution BSX Dia. 1.170" and the other set is "Derby Worx Precision Stock Wheels" I received in the box of goodies from The Mid America race. The Derby Worx wheels have the outer step removed. All 8 of these wheels I feel are perfect.
I started with a stock USA wheel that was .002 out of round. I mounted the Pro-Wheel shaver in a vise, put 150 grit sandpaper over the blade and sanded the wheel. I then used 220 grit paper over the blade and sanded the wheel. I could not improve on the runout. I then held a flat file over the blade and turned the wheel against the file. I was able to get the runout down to .001 defect but could not improve beyond that. A total of 30 minutes was spent with the file. The mold number was 10 for whatever that might be worth.
I suspect the vendors have such a perfect set-up they are able to turn out perfect wheels. I have several wheels that are off .002 and then many are 3 to 4 thousandths. The gage would be lots of fun for a scout to try to find wheels that are the best. If someone wants to try to improve on a wheel by sanding it, or some other technique, the gage will tell you what you have done to the wheel. The gage is also valuable if you buy wheels.
Good Luck.

[Vitamin K]

I received Knotty's Runout Gage yesterday. I'm very pleased with it. I already had the Pro-wheel Shaver. I have 2 sets of vendors wheels. One set is Derby Evolution "Revolution BSX Dia. 1.170" and the other set is "Derby Worx Precision Stock Wheels" I received in the box of goodies from The Mid America race. The Derby Worx wheels have the outer step removed. All 8 of these wheels I feel are perfect.
I started with a stock USA wheel that was 2 degrees out of round. I mounted the Pro-Wheel shaver in a vise, put 150 grit sandpaper over the blade and sanded the wheel. I then used 220 grit paper over the blade and sanded the wheel. I could not improve on the runout. I then held a flat file over the blade and turned the wheel against the file. I was able to get the runout down to a 1 degree defect but could not improve beyond that. A total of 30 minutes was spent with the file. The mold number was 10 for whatever that might be worth.
I suspect the vendors have such a perfect set-up they are able to turn out perfect wheels. I have several wheels that are off 2 degrees and then many are 3 to 4 degrees. The gage would be lots of fun for a scout to try to find wheels that are the best. If someone wants to try to improve on a wheel by sanding it, or some other technique, the gage will tell you what you have done to the wheel. The gage is also valuable if you buy wheels.

Thank for posting these results, Speedster!

So I'm guessing that you put the sandpaper over the blade in order to comply with the "light sanding" limitations in regards to wheel modifications?

Is your dial indicator measuring in thousandths of an inch? If so, then getting .001" runout from a Derbyworx Tool is pretty durn good, if you ask me! I'd be interested in knowing what sort of results you get from using the blade itself, rather than sandpaper or a file.

[Speedster]

My apology for using the word "degree". I have corrected it. Yes, the gage measures in thousandths. Our rules do state sandpaper but I actually liked sandpaper prior to getting the gage because there's no grabbing. However, I was able to get better results with the file and there's also no grabbing. I'll give the blade a try on a new wheel and see what result I get.