How we Overcame the Shortage of Mecanum Rollers.

A few days ago we as a team came up with a design for an intake system and looked online for some machanum rollers online. Turns out that they are out due to the number of people that also have the same idea. The reason that mecanum wheels work so well is that they don’t require any inwards force to produce a change in direction the wheels themselves solve that problem funneling them to the center of the indexer.
Anyways we have been brainstorming for a few days and after a but we looked at 3 d printing using this cad design (https://www.thingiverse.com/thing:2167). After finishing the print which took roughly 8 hours to make a set of two we found that to have a full set for our design it would take many more days.

This is what started our journey to using epoxy casts. After that day, my fellow peers had a 3 d printer at home that can print resin. Resin is great for making blanks due to its ability to be smooth. After that, we looked at different mold types. There are two main types, tin-Silicone, and Platinum-Silicone. We opted for the tin as it takes less time to cure but isn’t as strong (it isn’t necessary because we would only use each a few times more info here https://www.smooth-on.com/category/tin-silicone/). Turns out a mentor had some at home*

Our next big leap was finding a compatible epoxy/resin to use. We wanted something that’s faster than 3 d printing and more cost-effective per square inch. We set our parameters as the following, Must work with tin- silicone mold must be less than 8 hours of cure time, must have a pot life of 5 minutes or more, and must have a tensile strength greater than 3,000 psi. We can to the conclusion that Task 21 would work best for though premature (https://www.smooth-on.com/products/task-21/).

In our findings, this may not be the best way of doing it but it is a start and from the cast that we have done it has been within .003 of an inch in accuracy after shrinkage.

Cheers,
StinkPrinting
Team 1983 Skunkworks Robotics
Donate to our Team Here: https://skunkworks1983.com/Donate

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Any pictures? Sounds awesome!

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Not to rain on your parade but have you actually tested a prototype with your mecanum wheels? It is not clear from your post if you have a prototype you are happy with the performance of or are designing off the expected behaviour of a ball.

This year’s game piece is rather odd in both being incredibly "sticky’ and very compressible. The end result is that it is very fussy geometry wise to being willing to be walked sideways to the desired singulation spot in your intake, rather than just grabbing and getting squished between the intake roller and whatever. Too little contact between the intake and the ball and not engage the ball and walk it sideways, ever so slightly too much and it will grab and try and squish through the intake that that spot. It certainly works well if you can control the sweet spot.

We played with mecanum intakes for a while before discarding them as inconsistent and moved on to the more general roller intake (which means you have to solve singulation after the intake).

Sorry for the lack of clarification. We have tested for a total of ~Four hours. Our intake system was still in prototyping when we first found them. We overcame the compression issue by Increasing our clearance between ball and wheel. And of course something will always go wrong so that’s why we give time to make the mistakes and fix them.
Feel free to ask if you still have questions.

That will be held for our promo video sorry.
If you have questions feel free to ask.
Thanks.

*And forgot to add for the indexing part of our intake we have an offset edge to allow for funneling more efficiently.

Excellent. Was just concerned you had gone down the mecanum path without a prototype, due to shortage of wheels, and had not yet discovered the special joys this years game piece brings.

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