I am trying to develop something similar to Thrifty Bot’s 3d printable thread tool for 3 Inch Aluminum Billet Wheel. However, I’m not sure about the length of the tread for Andymark 6 in. Performance Wheel. As I understand from the Thrifty’s design, tool’s length should be longer than the circumference of the wheel. Did anyone design something similar before? How can I calculate the length and the bolt holes?
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Circumference equals pi * D. Arc length = Circumference * (degrees) / 360.
For instance, if you have a pizza that is 12 inches in diameter, it’s 37.699 inches around the circumference. Now, if that pizza is cut into six equal slices, the edge of the crust of each slice is 6.238 inches long, following the curve.
Note, the diameter of the 6 inch AM performance wheel is actually 5.6 inches where the tread sits.
Calculate your circumference to get your overall length. For the hole positions, figure out how many degrees apart they are radially and go from there.
I did the same calculation but there is a considerable difference in length between the circumference of the wheel and the tread of Thrifty. I believe that they have an extra to ensure that it covers all the surface.
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I’ll tag @samthesnake as he designed that tread tool, but even then we had to fudge it a bit. It depends also on the tread you’re using as the original tread tool was designed for the 2 ply thrifty tread and when we went to 3 ply blue nitrile, it was thicker and didn’t wrap as nicely, so we had to scale the tread tool a bit in one axis until it worked.
It would be awesome to have this though. We’re looking at using the AM performance wheels and having a repeatable cheap 3D printed pattern to use would be sweet for consistent lengths of tread and an easy way to mark some kind of hole pattern on it.
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The biggest reason why I want to make this idea is not to make the wheel unusable by drilling it too many times on different spots. Also, my team will probably use the wheels for at least 2 more seasons since we are located at Turkey. If we can make such a tool, we can use the same holes multiple times.
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Yep-- there’s a neutral axis somewhere within the curved strip of material that experiences no stretch. Since this neutral axis lies somewhere inside the strip, its circumference must be larger than the wheel circumference.
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Following Nate: the neutral axis is going to be in the middle of the fiber group… The treads don’t carry any tension in bending due to their teeth.
I would trim the length on a test part until you are happy with it.
An installation thought: you might be able to zip tie between one or two pairs of holes in order to pull the strip tight around the wheel before you install the screws. Once most of the screws are in, you can cut the zip tie(s) and put the last couple in. Safety wire would be another way to do this trick with even more tension. I think I’ve seen teams using a worm gear clamp around the whole thing to squeeze it into place before screwing. Thinking again, that might be a better idea than mine…
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We made a tread drilling jig for the SDS MK4 wheels based off the measurements posted by @PatrickW
Still waiting on the drill bushings, but we used our laser cutter to cut out the 1/4in acrylic. Haven’t fully tested it yet, but all of the holes line up nicely with a factory drilled tread.
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Andymark has an assembly video which uses hose clamp to squeeze the tread. https://youtu.be/0n00om1MsNE However, as demonstrated on the video they drill random positions on wheel. I want to create a hole pattern to increase the lifespan of the wheel. Is it possible to calculate or estimate the neutral axis?
Yes, but you would be better off wrapping the tread and marking from the inside of the wheel out to the tread, unwrapping, and making your jig match that. If you have un-drilled wheels you could drill your tread however you wanted, then make the wheel match it.
Take a piece of tread that fits very well off a wheel, lay it flat, and measure?
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I don’t have the wheels and treads now but it seems like the best solution.
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I like this a lot too. The easy low tech solution is to probably just create a primary tread, label it as such, create a template from the primary tread from another material and keep the two together.
One tread to rule them all®©™
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One thought is just to use the jig for marking and not drilling. Then line up and punch the holes. You’d just want a fine tipped marker and you can use the sight in the punch. A punch like this Whitney punch make a nice hole through tread without needing to clamp the tread so it doesn’t twist with the drill bit. I say this with the caveat we haven’t done the bulk number of tread that others have so clamping and drilling probably is better for some, but I think the 3d printer jig would be simpler without it and you can get faster after using the punch.
Edit: some reason I didn’t see there clamping solution in the first picture which isn’t too bad either
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BTW, Whitney punches ROCK on sheet metal and plastic!!! I have two frame sizes and love, love, love them!
That said, there’s a lot of tiny parts for kids to loose 
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We had good results chucking up a 3/16 flat endmill in a hand drill. Actually cuts a hole rather than pushing the material around.
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I’ve had better success using leather punches versus drills.
Give it a shot.
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I presume you’re talking about the tread, not the wheel. If so, I totally agree! I’ve used a rotary leather punch for a wide variety of plastic and rubber and fabric materials as well as leather. The holes are way cleaner than a drill could accomplish.
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Are there any STL/STEP files for this? For MK3 and MK4 Swerve modules
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