Is it possible to use a screw joint for my middle wheel? The longest I have is 1.5 inches, the longest on the vex website are 2 inches and my chasis is 6 wholes wide including the two c channels. Am I stuck using an axel here?
Yes. There are no screws long enough to span 6 holes
If you really wanted to, you could put the wheel on a screw that’s 1.5” and use a stand-off and another screw to span the extra length.
actually, you might just be able to use a 2" screw for that. you have to span only 4 holes of distance with the screw, and each hole is .5". you’d still need to use a standoff to connect the other end of the screw though.
if you have an unpowered middle wheel, I’d suggest locking the omni rollers, otherwise it really doesn’t have a purpose.
In general, I don’t really see a need to be wanting a screw-jointed wheel. Having that wheel on a shaft should be fine in terms of friction and load.
How exactly does one do this?
You put screws in all the rollers so they can’t spin
Use twenty-four .5" screws https://www.youtube.com/watch?v=cKM5kPYdWVU
Huh. Thanks! Makes much more sense now! (Sorry. I’m out of likes)
So the reason a screw joint isn’t necessary here is because the force is distributed across 4 (or in this case 6) different points on a chassis. That load is not enough to warrant a screw joint. Axles in almost all other cases are higher on friction than a screw joint, but that is not to say you can’t get an axle to be low on friction. It’s just not as good as a screw joint, and not as strong.
Also, sometimes you’re forced to use an axle in some places. It’d be a bit impractical for a chassis, but I’ve seen screw joints on gears on a chassis so it has been done before.
As people have said, you could use a 2" screw and standoff the last part (you would probably want to use a 1.75" screw in this case so you can actually screw in the other side of the standoff), or just put a bearing on the inside of the 2 c channels, maybe spaced out a little until the screw can reach it. If your wheel is unpowered and just free spinning, This could be a good solution. However, if the wheel is just free spinning then there isn’t much of a point in having it. If there is a sprocket or something on that ans I’m just blind, you would need to find some way of forcing the wheel and sprocket to spin together if you used a screw joint, which would mean using zip ties or screws. You could also technically square out part of the screw like this, but at that point you should just use a shaft and save yourself the trouble.