Let’s say that I have an aluminum-bearing block-plastic spacer-shaft collar-gear-steel washer-aluminum arrangement in a joint.
Where should I put Teflon washers in this arrangement, if I wanted to minimize friction?
Putting it between the steel washer and the aluminum might make sense because it is metal-to-metal contact, which isn’t exactly known for being low-friction.
Around the spacer, though, is where I get stumped:
should I put a Teflon washer between the bearing block and the spacer,
spacer and the shaft collar,
or should I put one at both of those places?
Should I just not put one in, at all?
And then, there’s this argument against putting Teflon washer between the steel washer and the aluminum:
if I were to put it between the gear and the steel washer instead of between the washer and the aluminum, even when the shaft is turning, the steel washer might stay stationary due to the static friction between it and the aluminum being greater than that between it and the Teflon washer, while the dynamic friction between the stationary steel washer and the rotating gear will be minimized thanks to the Teflon washer.
In other words, we get to have less mass on the rotating body by excluding the steel washer from it, while retaining the friction-reducing property of Teflon washer.
This should result in less load being put on the motors, meaning more better, and more better, as we all know, means more good.
This argument is undermined, however, by my experience of seeing swing gears work(on YouTube).
As far as I can tell, spinning axles seemed to miraculously turn the supposedly-free-spinning gears on them, which makes me believe that spinny things impart spinniness to neighboring bodies.
If I were to force the steel washer to stay stationary with the axle spinning, I might just be causing dynamic friction to happen between the steel washer and the axle, wasting kinetic energy.
So, where would you put Teflon washer(s) in this context?
I would replace the steel washer with the teflon one. as long as you don’t over-tighten the spacing on the shaft, you really don’t need to put washers between plastic on plastic contact.
if your spacing is so sensitive that replacing a steel washing with a nylon one isn’t possible, your spacing is probably too tight. The trick for friction reduction is to let there be a little bit of slop in your spacing. Not much, only like a washer’s worth, but it’s much better than having the spacing tight.
Actually, it was bad wording on my part. Please excuse me, English isn’t my primary language. Let me rephrase the original question:
Which would be better,
alu-bearing-teflon-plastic spacer-shaft collar-gear-steel washer-teflon-bearing
or
alu-bearing-plastic spacer-teflon-shaft collar-gear-teflon-steel washer-bearing
?
I would just do
aluminum - bearing - plastic spacer - shaft collar - gear - teflon washer - bearing.
as long as you give a little bit of slop in the spacing, you probably don’t even need the teflon washer. you might need a spacer to stop the gear from rubbing against the bearing though.
30597A this is a great tip. This year in all my CAD I would put my clearances as close to 0 as possible, and often I was actually able to get them within a few thousandths of an inch. I did this on an intake, and test built one the other day. The problem was when the spacing was so tight the axles actually had quite a bit of friction. Going one steel washer less completely fixed this. That does introduce more slop than you’d want on many real life machines, but for the robot it doesn’t seem to affect things.
Assume that the spacing I laid out already has a washer’s thickness worth of sloppiness. Would that change your answer?
edit: as in, the ‘original’ spacing already had jankiness worth of two Teflon-washer-thicknes and a steel-washer-thickness.
edit 2: to clarify, the spacing that I provided in this thread are hypothetical: as in, I’m not actually going to use those spacings. In practice, it’ll look more like:
, with a Teflon around any of the 0.5" spacers. For the record, I’m not using this one either.
I’m just trying to theorycraft the optimal placement of Teflon washers when multiple bodies rotating around a single axle aren’t constrained to the axle, nor to the other bodies.
what exactly is this axle for? an intake? can’t think of any mechanism this year where some slop along the spacing of the axle is really a concern. So really I would have anywhere from 1-2 washers worth of slop in your spacing. At the end of the day the friction from a Teflon washer vs any other plastic on plastic rubbing is negligible. only time I think its important to use a teflon washer is between any 2 pieces of metal. Between a shaft collar and aluminum for example, is a place you should put one.