My team is planning to make a screw jointed drivetrain but we haven’t done it before. If we use standoffs on the joints do we have to add a washer before the wheels so the standoff doesn’t contact the circle insert, or does it not matter?
Also would appreciate tips on screwjoints, thanks
In general, it’s good practice to have a washer or spacer between a rotating part and metal. Having no washer would increase both friction and wear between the insert and standoff, neither of which are good in a drivetrain.
How does using screw joints for a drive train give an advantage and also how do you do it
Screw joint benefits:
These are just from my experience though, please correct me if I’m wrong.
How to make:
Try searching on BLRS wiki or here on vexforum, there are plenty of topics discussing this
Thank you so much @pmkv this will help me improve in robotics vastly this has me rethinking my whole drivetrain for high stakes
I’d have to see hard data, and the testing methodology, on item #4 before signing off on that one.
And, even if true, the effects of that are largely negligible compared to the power needed to do actual work.
Ok, you’re right, a reduction in friction is probably negligible. My screw-jointed drivetrain did free-spin longer than my all-axles drivetrain, but that’s probably a product of a difference in build quality.
Thanks for correcting me on that one!
this is how i make screw joints
But how dos the motor move the round insert? because won’t the screw just not more because the insert is round.
u use the motor to power a different shaft thats geared to the wheel and gear → you must connect the wheel and gear together with screws
what? can you show me like a model
In this diagram, I think you could replace the nut with a spacer or something, the screw is already screwed into the stand-off so nothing on it will move
The problem isn’t that the screw needs to be tight, it’s that the wheel needs to be free-spinning. If you tighten the screw too much without the nut, the spacers, wheel, and standoff will all be rubbing against each other, causing a lot of friction
Yeah, but if it isn’t screwed in, everything on it will just wiggle around and maybe the screw will even fall out. But, what I meant was that the nuts there are unnecessary since there is already the standoff. If you replaced the nuts with spacers or washers, it might decrease some friction since metal isn’t rubbing against metal.
well the wheel and gear spin on the wheel and the screw doesnt move so i don’t see where metal would be rubbing on metal
Question, why do you have gears on both sides of your wheels? I think its fine if you only have gears on one side.
Backup redundancy. Since we don’t like cutting parts (except aluminum, we have a lot of that), and we wanted to screwjoint our wheels, we opted to not drill out expensive VEX gears and instead utilized 3d printed PETG ones (modified to have a screwjoint hole).
Needless to say, we were kind of wary about it snapping (especially since the filament was kinda old), so we put two gears for redundancy in case one side failed.
Just curious, did the backup gears have any effect on performance?
Is that legal? In VRC high school, to my knowledge, 3d printed parts aren’t legal except for non functional decorations.
