Ideas towards Cub-centric wheel improvement...

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Vitamin K
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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Thu Oct 15, 2015 6:13 am

bracketracer wrote:VK, I'm not sure that a slide holder is going to be up to the task of cutting plastic?
If there's any deflection your accuracy will go out the window.

Too late now since I see you've started ordering parts, but what about perusing craigslist for a small used wood lathe for your starting point?
Interesting point. I guess the issue in question would be how strong the threads of the adjustment screws hold the stage in place? I wonder if it would be enough, given that the plastic of a wheel is relatively soft, and the depth of the cut would be very small.

I had actually thought on the feasibility of a wood-lathe conversion. In my mind, it seems like there are too many factors you'd have to overcome. You'd have to install some way to hold the piece. You'd also still have to solve the tool holder problem, since wood lathes don't typically have an XY platform for holding a cutting tool.



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Re: Ideas towards Cub-centric wheel improvement...

Post by bracketracer » Thu Oct 15, 2015 7:30 am

Which are the same problems you need to overcome at the present?

Except that a wood lathe would already have a mounted spindle with a speed control and a sturdy frame to mount a tool holder.
My wood lathe has a threaded spindle but also has a Morse taper. You can buy a MT shank ER collet chuck to bolt in for about $20 if that's the route you want go.



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Vitamin K
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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Thu Oct 15, 2015 7:54 am

bracketracer wrote:Which are the same problems you need to overcome at the present?

Except that a wood lathe would already have a mounted spindle with a speed control and a sturdy frame to mount a tool holder.
My wood lathe has a threaded spindle but also has a Morse taper. You can buy a MT shank ER collet chuck to bolt in for about $20 if that's the route you want go.
Hmm, it's definitely something worth looking into if this current path fails. The upfronts of the wood lathe could swell the budget a bit, but might also pay off in the long run.



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Re: Ideas towards Cub-centric wheel improvement...

Post by whodathunkit » Thu Oct 15, 2015 7:17 pm

Okay Vitamin K,
Since you tossed out your idea for making a homemade lathe .

I'll pass out this idea:
That has worked very well for me using a drill press with a sanding drum..
For truing up homemade wooden wheels for car models.

However I'll just say this sanding jig idea I'm passing out towards wheel improvement.
Needs work on several things to make it better for truing up pinewood derby wheels.

Like different grits of sanding paper for the drums for one..
Anyhow it's just an idea to keep thing's low for cost.

Image
Image
Image
Image


What type of automobile can be spelled the same forwards & backwards?

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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Fri Oct 16, 2015 8:21 am

Very interesting design there, Whoda! So I guess the wheel spins on the pin and contacts the drum?

Have you measured the runout of the final product?



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Re: Ideas towards Cub-centric wheel improvement...

Post by whodathunkit » Fri Oct 16, 2015 5:52 pm

Vitamin K,

I use a jig like this most:
For making my own model car.. wooden wheels true and round to the bore.
Most of the wooden wheels I make are 2" to 3" in diam some are on a larger scale.

Funny: How I forgot about this sanding jig..
And how the idea of using this jig for pinewood derby wheels hit me last night.

It was the first time I tried out this sanding jig idea with a plastic derby wheel.
The sanding grit on the drum was way to aggressive for the wheel.
And I knew it would be so that's why I said it has it's faults.

If one could find or make sanding drums..
With the different wet / dry sanding paper grits they might just do better with it.
Then I did with the 150 grit sanding drum on the plastic wheel & jig for the first time.

Plus to make this sanding jig better the slider bar on the jig
could use some supports over the top of it to help keep the slider bar flat and true to the base.
And maybe a better way to lock it down at a set point to keep it from moving in to the sanding drum.

Anyhow it's just a wheel sanding jig idea for the drill press with a drum sander.

For a sanding jig idea for the disk sander:
https://s-media-cache-ak0.pinimg.com/23 ... d88efc.jpg


What type of automobile can be spelled the same forwards & backwards?

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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Sat Oct 17, 2015 9:32 pm

Well, I'm waiting for my parts to arrive from China...in the meantime, thinking over the whole toolholder thing.

So the mini-lathe plans do include a how-to for doing a tool holder. It's somewhat primitive, but I think it is workable. It was intimidating at first, but after reading over the steps a few times, I'm feeling a little more confident.

http://www.instructables.com/id/Mini-Me ... tep7#step7

I still have the issue of not having a way to braze metal. However, I do have some (wait for it) JB Weld on hand. Some of you are laughing already, but given the pressures that are going to be exerted on the various joints, I think metal-reinforced epoxy is going to be more than up for the job.

I'll be sure and post pictures.

Stop laughing. :mrgreen:



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Re: Ideas towards Cub-centric wheel improvement...

Post by whodathunkit » Sun Oct 18, 2015 7:49 pm

The tensile strength of J B weld is 3960 psi and can with stand temps up to 550*F when fully cured.
It's cheap in cost when looking for a ways to bond metals.
When the Bernzomatic welding & brazing torch kits will run you around $78.98 for cost..
plus the brazing or welding rod cost on top of that.

When your looking for ways to keep the cost under $100.00 for your lathe project...
saving the buck'$ is no laughing matter.

Just make sure to remove the mill scale off the metal if brazing is the route take. ;)


What type of automobile can be spelled the same forwards & backwards?

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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Tue Dec 01, 2015 1:51 pm

Plodding along with progress here...

Got the extension rod and the pillow bearing mounts. Ordered the spring collet, but got the wrong size. Ordered again and got a different wrong size. Third time will hopefully be the charm there...

Anyhow, here's the rod mounted in the bearings. I actually got a package of 4 bearings, which is good, because the first one I tried was warped.

Here's a test assembly:

Image

Just measuring the shaft with a dial indicator as it turns gives me a runout reading of close to zero, so that's good, so far.

The next step will be to chuck a pin gage in the nut and measure the runout on the gage. Based on that measurement, I'll know whether or not I have a viable setup.



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Re: Ideas towards Cub-centric wheel improvement...

Post by Speedster » Sat Dec 05, 2015 5:58 am

Vitamin K, I'd like to invite you to do something. If you do not own one of Knotthed's gages, please buy one. I deal with 4 vendors. Buy one set of their basic wheels where nothing has been done except to make them round. Let us know if they are actually round or are some of them .001 or .002 out of round on knotthed's gage. There are actually some wheels that will come out of the mold and be only .002 out of round. It has been said on DT that a person will have to do 100 wheels before they can start to produce a quality wheel and that's with quality equipment. By all means have your fun. If anyone on DT can actually make a round wheel I would like to know exactly what kind of equipment you have to make that wheel. I'd also like to know what your background is. Thank You.



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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Sun Dec 06, 2015 2:20 pm

Speedster wrote:Vitamin K, I'd like to invite you to do something. If you do not own one of Knotthed's gages, please buy one. I deal with 4 vendors. Buy one set of their basic wheels where nothing has been done except to make them round. Let us know if they are actually round or are some of them .001 or .002 out of round on knotthed's gage. There are actually some wheels that will come out of the mold and be only .002 out of round. It has been said on DT that a person will have to do 100 wheels before they can start to produce a quality wheel and that's with quality equipment. By all means have your fun. If anyone on DT can actually make a round wheel I would like to know exactly what kind of equipment you have to make that wheel. I'd also like to know what your background is. Thank You.
I don't have one of Knotthed's gages, though I do have the homemade FatSebastian version that proceeded it. Some posts I've seen seem to indicate that the former is more accurate than the latter, though I couldn't say by how much.

Have you tested any vendor wheels for roundness? I've tried the FS gage on a few wheels that were trued by a very successful league racer, and they all measured less than .001" of runout. I haven't personally purchased wheels from a vendor.

I'm also aware of the possibility of finding a few "unicorn" wheels (I don't remember who coined that term) out of the tubes. That is my current practice for the kids' races.

This little lathe-building exercise is mostly a matter of exploration and seeking to gain knowledge. If I do come up with something that is useful, I will be sure to share it with the Pinewood community.



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Re: Ideas towards Cub-centric wheel improvement...

Post by Speedster » Sun Dec 06, 2015 3:52 pm

Yes, l have tested many vendors wheels for roundness and a few days ago I ordered another set from each of 3 vendors for testing. I'm going to see if I get the same results as last year. They are all the basic wheel where nothing has been done to them other than trying to make them round. The wheels are not always round. I consider a wheel round if the needle does not touch the .001 mark. The point I was trying to make is if the vendors with their expensive equipment, their skill, and their livelihood depends on making a round wheel and they can't do it, that should tell us something. I'm on your side. I really am. If you can make a piece of equipment for less than $100.00 and can make a wheel round in a sensible amount of time, my hats off to you.
I look forward to reading more about your project.



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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Mon Dec 07, 2015 7:53 am

Speedster wrote:Yes, l have tested many vendors wheels for roundness and a few days ago I ordered another set from each of 3 vendors for testing. I'm going to see if I get the same results as last year. They are all the basic wheel where nothing has been done to them other than trying to make them round. The wheels are not always round. I consider a wheel round if the needle does not touch the .001 mark. The point I was trying to make is if the vendors with their expensive equipment, their skill, and their livelihood depends on making a round wheel and they can't do it, that should tell us something. I'm on your side. I really am. If you can make a piece of equipment for less than $100.00 and can make a wheel round in a sensible amount of time, my hats off to you.
I look forward to reading more about your project.
I know at least one vendor that guarantees runout to be something like .0005" or less, so if I bought wheels from them and they tested differently, I think I'd want product replacement.

Part of me thinks that posting results of vendor wheel testing would be a service to the PWD community.

Anyhow, here's the thing: I tested wheels cut by a racer who was kind enough to send me some of his worked wheels and they were under .001". I know what machine he uses and it's probably about a $600 lathe. I also know that Stan has cut some very good wheels on his Harbor Freight cheapie. It's interesting to me that you're getting vendor produced wheels that are not so great, but maybe the issue at hand is not so much a question of ability, but a question of quantity. I have no idea how many wheels a vendor has to produce, but usually there's only one guy doing it. If you have to rush production, well, i would imagine that quality can slip. Just a theory, though.

Anyhow, I'm currently stalled out while waiting for my collet to arrive. Thing ships from China, so it might be a few weeks. Have been thinking ahead to the other problems I have to solve, if the pin-in-collet actually manages to spin true. (If it doesn't, well, no sense in proceeding any further).

First problem: Tool holder. I am probably going to plod ahead with the homemade X-Y table, fused together with metal-laced epoxy. The investment for the parts is very low.

Second problem: Propulsion. I think I'm still leaning towards using a Dremel-esque tool with adjustable speed to drive the thing. Harbor Freight's got one for like, 20-25 bucks depending upon whatever specials they are running.

Third Problem: Power transfer. I need a way to make the rotary tool spin the shaft. For this, I'm thinking of getting (from Shapeways.com or similar) some plastic pulley guides printed. One will go on the shaft of the collet rod, and the other will go on the end of a rotary tool shaft. This will allow me to choose a size ratio that will spin the rod at the right speed threshold for working polystyrene wheels.

These are all just musings for now, but any thoughts on my thoughts (so to speak) are welcome.



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Re: Ideas towards Cub-centric wheel improvement...

Post by knotthed » Wed Dec 09, 2015 6:55 pm

Without going into the machining calculations........Feel free to take a look at Machinery Handbook, probably available at the local library.

I think your going to want to turn the wheel between 400/600 RPM for single point turning(Like on a lathe). Of course there are many factors, like cutter shape/design etc...

I suspect the dremel/rotary tool approach will offer too much speed, and if you can slow it down enough with the potentiometer you will likely loose the torque your after.



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Re: Ideas towards Cub-centric wheel improvement...

Post by Vitamin K » Wed Dec 09, 2015 8:21 pm

knotthed wrote:Without going into the machining calculations........Feel free to take a look at Machinery Handbook, probably available at the local library.

I think your going to want to turn the wheel between 400/600 RPM for single point turning(Like on a lathe). Of course there are many factors, like cutter shape/design etc...

I suspect the dremel/rotary tool approach will offer too much speed, and if you can slow it down enough with the potentiometer you will likely loose the torque your after.
I was going to use the size ratio from the pulley wheels to slow down the speed of the rod turning. That is, a smaller wheel on the dremel end and a larger wheel on the rod end. Would I still run into the torque problem there, you think?



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