Has anybody here ever tried to make their own compliant wheels by casting them out of silicone? I’m planning on trying to make some for our intake and was wondering if anyone had any experience with them.
I believe 148 waterjet theirs. If you have access to a waterjet, use that, the old 2" compliant wheels from AM were waterjet and worked just as good as the new injection molded ones.
It might be hard to correctly cast a mould, but I’ve never done it before so I can’t say Forsure.
I know 125 custom molded their traction wheels several years ago (couldn’t find the thread off a quick search, someone else may have more luck). Not exactly what you’re looking to do, but it may be a pretty similar process but with a different material used.
708 made custom molded rollers during their prototyping in 2017. They didn’t end up using them in the end, but the mold itself was successful. They used a 2-part compound and poured it into a tube of the proper diameter with a hex axle down the middle.
My plan is to CAD the wheels and then 3D print a mold to pour the silicone into. I’m using the Polytek PlatSil 2 part silicone compound with hardner to try to get a Shore A value of around 40 (in between green and red AndyMark compliant wheels).
We had a sponsor waterjet compliant wheels for us last season, they worked well.
We haven’t done any mold work, Brandon Holley from 125 would be a good one to talk to about it. Here’s his post from 2012 that discusses their shooter wheel: https://www.chiefdelphi.com/forums/showpost.php?p=1179875&postcount=8
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get yourself some space wheels https://johnvneun.com/blog/2018/1/29/2018-day-28
We 3D printed ours with flexible filament. Which printer/filament combo to use and what post-processing steps are necessary is left as an exercise for the reader.
You may want to consider a polyurethane casting compound as an alternative to silicone. I use “VytaFlex”, but only in Shore 20 and Shore 40 hardness for making tires for mini sumo robots and similar small machines.
You may also want to consider embedding a tensile element into the casting… I’ve had some interesting results playing around with fiberglass cloth embedded in Polyurethane for making a tough, high friction, flexible surface.
3D printing the molds has also worked well for me. I use the raft as the bottom of the mold… it pulls away nicely, and a thin wall for the outside of the mold. I cut the wall and pull it away when done.
I’ve had good luck with this technique, except when I get a porous raft or wall… you’ve got to have the model and gcode set just right so that the urethane doesn’t leak into the PLA and bond with it.
Jason
In 2012 and 2013 118 used a couple of different urethane rubbers for the treads on their drive wheels. 192 then tried to copy them but had issues with getting the rubber mix right and they didn’t cure correctly (hard urethanes worked well, even tried some with fiber which made things way better).
We made silicone molds using 3d printed masters. I believe we used Reoflex urethane rubber from smooth-on for the tread. The silicone molds turned out well so might be fine for the end product. Just be careful about mix ratios and bubbles, maybe mix in larger portions so error has less of an impact.
The possible solutions to this situation are interesting and informative, but it seems like molding your own wheels is an extreme solution to a problem with existing COTS solutions?
I don’t know exactly what your criteria are for these wheels, but there’s been an upswing of Fairlane rollers in FRC for many applications and they provide a pretty large range of sizes and durometers. We prototyped them on our intake this year and they would have provided a good amount of compliance had we decided to remove material from them (either via waterjet or drilling). Here’s a link to their roller catalogue: http://www.fairlaneproducts.com/store/pc/Roller-Only-c1702.htm
Can vouch for this. Helps to spray in mold release, too, especially with ABS as the mold material. (Also helps to have a mill and/or lathe around to get through the wall and get you started.)
Before our waterjet went down we were planning on cutting intake wheels for other teams. We now use modified AM wheels by modified I mean we use the blue shore 50 but cut out a few of the spokes of the wheel now a little squishier like the green but still hard
For our intake this year, we bought a 12"x12"x1" chunk of 50a polyurethane, and had 3.9 inch wheels cut on a waterjet. Considering we ordered AndyMark compliant wheels on the day of kickoff and they never came, these wheels have been great for us. I also wanted twisted spokes, as opposed to the andymark wheels, so that the springy nature of the wheels is consistent as the wheel rotates. Plenty of grip for the cubes with minimal wear after lots of practicing. The hex was cut way smaller to be pressed onto a hex shaft, although we still made lexan hubs that are zip tied to the wheels and hex broached to prevent spinning on the shaft. I can post photos of them installed on the robot later.
https://i.imgur.com/4mIhDtTl.jpg](https://i.imgur.com/4mIhDtT.jpg)
compliant wheel version 1.pdf (8.27 KB)
compliant wheel dxf.zip (2.64 KB)
Although some posters seem to be talking about drive wheels, I assumed that the OP was referring to intake wheels (compliant) wheels. We tried using AM wheels and, although they worked well, we didn’t like how “compliant” they were. We researched and settled on BJBenterprises.com and their products.
They have great “how to” videos and we followed them faithfully. We 3D printed our “master” and put two of them in a box (forgetting to spray them with release and paid for it in terms of time of removal). We then poured the silicone over them and made the top part of the mold the next day. We just removed the second batch of wheels today and they are amazing! They are incredibly durable, grippy (30 durometer), and very compliant.
It can be expensive, however, as the entire exercise cost about $320 including shipping ($56). But with that, we have a permanent mold, and enough urethane to make about 25 wheels- so it’s not too bad.
Oh, we make a separate 3D printed hex hub for each wheel prior to pouring.
https://i.imgur.com/i0K2oE0l.jpg](https://i.imgur.com/i0K2oE0.jpg)
Here is an album showing the hubs we made and are using:
https://imgur.com/a/Rh2RH
We hex broached some circles of lexan that also had 1.85 inch bolt circles drilled into them. Then I used panduit cable ties with the strong metal tooth, and stitched them back and forth around the spokes. We used the tiny zip ties the first time around, and after 5 days of heavy practice, some of the ties were broken but the hubs still did not slip. We carried over the same wheels to the competition bot, but replaced the zip ties with the larger ones shown in the album. With the 50a durometer urethane, we have experienced zero visible wear on the surface of the wheels after our first competition.
I don’t have all of the information but 3005 has made their intake wheels for 2 years now. They seem to work great and maybe they can chime in.
It appears WCP has started selling “Hella Space Wheels”. Might be a good pick up for a lot of teams.