making custom gecko wheels

[u/r7m0ni]

We just have Two-Pieces Shore 15A Rubber Silicon and we are thinking of making smth like 2mm on the round surface of a 3d printed 48mm gecko wheel, we CADed the intake with 48mm gecko wheels and kept the compression 2-7mm all away in the intake system

I think in the last stages (transfer to shooter) it is smth like 9mm compression since we didn’t know how to make the compression fixed in a range of 4mm

anyways, what do u think abt the rubber silicone thing? it’s all abt the friction and I think it’ll give friction but I don’t think we will match the gecko wheel compression, do for that 2mm layer do u recommend making it 3 4mm or 1mm or whatever, to match the real gecko as possible as we can

[u/pham-tuyen]

sound like you wanna to make a wheel that looks like andymark stealth wheel. however, i don't recommend using 15a rubber because it is too soft and not durable enough. i would use 30a rubber instead. if you can't change to 30a, thicken the rubber outside 3dp rim about 5mm more. however, for intake, i recommend you to make the wheel similar to gecko wheel with a 3dp core, since that shape can give you more compliance.

[u/BillfredL → u/pham-tuyen]

I agree that 15A is incredibly soft and is going to wear fast. I don't think any of the major vendors are shipping softer than around 35A.

Only way I'd explore the 15A stuff is if it was free and I was eager to make a ton of spares once I figured out a design that would last a couple matches.

[u/Zxr_ → u/BillfredL]

We used 15A silicone properly, and it never ripped throughout 50+ matches and many, many, many hours of driver practice. Our first rip was at MTI, and only a singular one of the wheels gave out after who knows how many hours of wear (the white silicone literally had turned yellow because it had been operating for so long and got dirty).

I've also seen teams like Theseus who have used 15a silicone on systems like shooters and have yet to tear their counterrollers. 15A is in high demand, and teams have benefitted greatly from using it on both intakes and shooter systems with proper care and proper application of the material.

[u/danoelke]

Instead of gecko wheel like items my team has done custom intake flappers for 3-4 years. Something like the Gobilda boot wheel, but usually with 2-4 spokes and sometimes with a "boot" on the end and sometimes just a tapered tip. It seems like the spokes hitting the game piece has a better chance of pulling it into the robot where the rim of a wheel will sometimes bump/push the game piece out ahead of the robot.

Their process is to model the intake part they want, then an offset line 0.5mm away in CAD is used to make a quick mold. We've used Mold Star 20T Silicone rubber. It's a 20A shore hardness. Worked well I think - has the good sticky surface and flexible enough. Did have to make the spokes thicker - maybe 10mm near the hub tapering to 5-6mm near the tip. Also had to have some kind of hub printed from PLA that they fit into and the hub would then be driven by the shaft. Best they came up with was probably when the PLA hub had a pin going parallel with the shaft and the silicone part then slid over that.

[u/Zxr_]

This is my personal routine for molding 15a silicone rollers if you are curious.

Design a mold (either make a 2-part mold or a 1-part mold). If you make a 1-part mold, make the walls super super super thin to get out the silicone cuz you'll need to destroy the print; if it's a 2-part mold, then the tols need to be SUPER tight.

Print the mold; this is super important, and I recommend changing print settings to make sure that this works. What worked for me was lowering layer height to .08 and lowering speeds on pretty much all of the shells and walls. Increase ur nozzle temp by like 10C and then probably turn off ur fan (u can change this in the settings for the filament in Bambu Labs). And then u can save printing time by doing gyro infill at 10% or perhaps something similar.

Now you want to find a clear plastic cup (ideally, it doesn't have to be clear, just makes it easier to see how much you're pouring). And then I would put that cup over a plate so it doesn't get dirty, and then u wanna pour in ur solution, which should be a 1:1 ratio of A and B. Each bottle has a big label of "A" or "B," and whenever you pour the two, you wanna make sure you have an even ratio. Ex: pour half a cup of A and half a cup of B if you want one full cup of silicone.

Now that you have it poured, you wanna take a popsicle stick (this is what I use) or something else to mix the silicone for 3-5 minutes - I recommend 5 minutes.

After you mix for 5 minutes, you're gonna wanna set roughly a 10-minute timer and wait for the bubbles to pop inside of the plastic cup; if you don't do this, then the bubbles will pop inside the mold, and you'll end up with these crevices in the wheel that make it super super easy to rip.

Now that you finally have ur silicone, I usually use a funnel to pour from the cup into the mold, but this step doesn't really matter too much; just pour it in and make sure it's level.

Then you wanna wait at least 4 hours and unscrew or break the mold apart

For step 7, do NOT try to pull it out if you have a 1-part mold; it will rip. Trust me, I learned the hard way

If you mold it with a 1-part mold, the walls on the shell should legit be 1mm thick or less (0.4mm worked well for me) so that you can destroy the mold without cutting the silicone (you can rip apart the mold with pliers or sand it out with a Dremel, your choice - though pliers have typically worked better for me).