Great idea!
I think there are basically 2x2 solutions the community needs for a hub.
1.1 Regular width 4" hub with 28mm OD bearing seat ( like Super Stars)
1.2 Wide 4" hub with 28mm OD bearing seat (wider than Five Stars)
2.1 same as 1.1 but with 22mm OD
2.2 same as 1.2 but also with 22mm OD
If you can include Kegel bolt pattern that would be great.
Pullies should work from 44T-80T.
Offset for the wide hub version would be a must have and I would suggest a total width of 70-76mm.
Do you guys see any problem with this not having a fillet (rounded edge)? All of the current hubs have this edge rounded out, but due to my design, the pulley side cannot have the filleted edge. I just want to see if anyone knew anything about this.
The frc wheels do not need the filleted edge, so I think it should be fine, but maybe someone has some insight.
Sharp edges cause pressure.points which can cut into the tire.
Also, I’m super duper down for a set of 4" hubs
Right, that was my concern as well. Just from seeing how much those wheels are used in FRC with out any issues, I thought maybe it would be okay.
I think a fillet on those edges might relieve some of the expansive pressure of the tubes. Someone correct me if I’m wrong.
Frc?
First Robotics Competition
Lol I don’t think anyone used pnuemies in that finals match, but just shows you what the bots go through.
I don’t think the speed that the pnummie tires in FRC spin at compares to our application, I wouldn’t feel comfortable without a fillet there
The wheels go through a lot, we had 6 inch pnummies on our Stronghold bot and those went through a lot but it really just still doesn’t compare to what we do to them
Also @surfnacho leave it to cheesypoofs to have the most insane robot, per usual
guess that’s what happens when your nasa engineers build your robot /noshade
While yeah it was insane, but definitely not my favorite 2019 bot. It was too complicated unlike their 2018 boss mode elevator.
Madtown swerve + elevator was just too good. Their auto was beautiful, their cycles were beautiful, it was just great. I also really liked 971s bot last year, it was unique lol
I agree that our boards go through a lot. That is why I thought I would reach out and ask. I was pretty confident that we would need a fillet there, but after doing some research, we found that the 3ds hubs do not have a fillet.
I haven’t kept up with FRC since Stronghold when I graduated in 2016, I’m sure other competitors have come with some impressive stuff as well
They actually pulled off a swerve drive??
hm interesting
Swerve was the bees knees in 2019. Defense was a bitch, so all the drifty bois could whip around defense.
https://www.swervedrivespecialties.com/collections/kits/products/mk3-swerve-module these new drives are kinda sick.
^^we made these last year and they are actually pretty sweet.
But so far we have only used west coast drive
In the video that I linked above, the blue team 1323 is using their custom swerve drives, and you can see how smooth it is.
That’s crazy, I don’t think there were any prebuilt solutions in our weight requirement in the past, that one is pretty impressive.
FRC is probably so different now with all of the 3D printing and ease of CNC machining and stuff. My team had barely just gotten a CNC router and 3D printing was still not really an option yet
I saw them whipping around there, was wondering what it was
@surfnacho I’d also like to mention that that cyclic stress is the real killer in many applications and is surprisingly devastating compared to the more visceral thrashing those bots get.
Not to underqualify what robotics competition requires in terms of skill and engineering quality. BUT
Making something work well against crazy abuse for 30 minutes if often (not always) a lot easier than making something work for 10 thousand miles of very slight abuse. “Death by a thousand cuts”
Yeah there have definitely been a few improvements. 3d printing has been great for our team. Our bot had a lot of printed parts. Our telescoping hood was made on our Markforge printer, printed pulleys, spacers, etc.
We are also lucky that we get to work out of a manufacturing facility. Access to Haas machines and a big laser definitely helps lol
Yeah I totally get that. Makes sense.
Do you know anything about those 3DS hubs? Those have flat edges and seem fine.
Just want to say… I appreciate someone who tries to document for clairty, when numerous ideas / options are being thrown about. 
Design point of note: The hellcat wides from kaly, the inner hub is too big. it makes fitting some tires too hard as the bead won’t move across the hub.
the XCELL rims from Land Surf have an ever so slight taper to the hub. fiting tires on them is a breeze. but possibly the diameter of the hub near the rim is also just appropriately sized.
If you just "sand the edges then you’re probably fine. So whatever process is used to polish those hubs probably removes the sharpness. Or a separate dulling process is used.
But I’m totally guessing here
Hey guys! I get to work with @surfnacho on lots of cool things (like robots) and am stoked to help out with these rims.
Doing some quick napkin math I was able to come up with a max moment that the wheels could exert axially on the rims. Plugging that into some FEA it looks like 3.5mm 6061-T6 is plenty rigid enough, but we are looking into adding more bolts switching to 7075-T6.
That being said, I’m assuming the radius has more to do with releasing stresses on the tubes, I’m curious how deep into the corners the tubes actually go, would be cool to get some acrylic wheels made to see.
The only wrong assumption with the FEA is I assumed the force is distributed equally across the half-moon lip, which for a tire, would have some gradient depending on the PSI.
Assumptions made in napkin math: 80%-20% weight distribution to outside tires when turning (similar to F1 cars). 1.1 coeff of friction, might be the case on smooth dry pavement but im sure this is way lower in reality. 90kg rider. Simulation tested with both 6 and 8in tire moment arm.
