Lubricated metal-to-metal vs. metal-to-teflon

VEX Robotics Competition Discussion VRC
#1

tl;dr: grease good?

Ever since I really got around doing VEX, I always tried to put Teflon washer everywhere something would move:
I’d put a Teflon washer between aluminum c-channels,
a screwhead and a free-spinning gear,
a screwhead and an aluminum c-channel,
a screwhead and a bearing block,
and a bearing block and a spacer.

The problem is that I only really got around doing VEX last year, and even then, I only got around becoming a mediocre VEX person last month or so.
The sheer price of Teflon washer only dawned on me about two months ago.
I wouldn’t care about the cost of the parts that go in my robots if, for one, our robotics program was funded well, or for another, my team wasn’t trying to buy our own parts:
sadly, both aren’t the case, and I really do have to care about the cost of stuff that we buy.

One perk of being a mediocre VEX person is that I am aware of greases’ existence.
Greases aren’t as expensive as putting Teflon washers in every pivot, and given that grease layers tend to be thinner than a Teflon washer, using them would also save space.
I’ve been thinking about buying grease, and one of the three things that are stopping me from buying them is the lack of knowledge as to which one has less friction:
greased metal-on-metal, or dry metal-on-Teflon-on-metal.

I’d love to experiment with this myself and find out.
Unfortunately, the other two things that stop me from buying a bottle of grease are their cost and my team being almost broke.
I’ll have to really know if they are as effective, or possibly more effective, compared to sticking in a Teflon washer, before I risk becoming that guy who wasted precious money on stuff that doesn’t even work.

This is where you come in.
Would you say that the effectiveness of grease lubrication and the relatively cheap per-joint cost of greases outweigh the cost of initial investment for a bottle of grease? Does the friction-reduction performance of lubricated metal-to-metal support, or undermine, the argument for grease?

Thanks for your time.

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#2

teflon is overpowered
0.04 CoF really can’t be beat

i personally use teflon washers and Blaster’s “industrial strength” silicone-teflon lubricant together, because the surface roughness of vex teflon washers often leaves something to be desired, but is still always going to be better than metal on metal

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#3

if price is a problem, just grab some nylon washers from mcmaster. spacers less than 2” long are legal under R12, so you should be fine using those. nylon doesn’t have as good of a CoF as teflon, but is still a great self lubricating material and is definitely a bit cheaper

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#4

We use White Lithium Grease on our gears and bearings - works like a charm!

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#5

Thanks for the tip. I was thinking about something similar to this topic a while ago. Would you say the metal washers are an improvement over having nothing there?? I mostly use them as spacers anyway and already use the teflon ones but I was just curious.

Also would you consider them “good” still or are they that much worse than the teflon ones?

#6

nah. steel on aluminum is a no no

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#7

Let me rephrase my question.
In terms of having less friction, which will work better: metal-lubricated-with-PTFE-containing-lube on other metal, metal-on-nylon-on-metal, or metal-on-Teflon-washer-on-metal?

This is supposed to have PTFE in it, and using it on a pivot should, in theory, make the parts’ frictional coefficients emulate that of PTFE.
If this actually is the case, then it would render Teflon washers unnecessary.
Or the nylon washers, for that matter.

#8

For this any metal to plastic will have less friction as it is hard to get metal to metal surfaces to have low friction. The only exception I can think of, is if you have 2 polished steel surfaces with light oil between them. It also depends on the loads that you will see on this so ask yourself this.
(a washer puts a physical barrier where only grease eventually squeezes out and isn’t effective on its own)

*Does it have to hold a lot of weight ie; intakes for TT (then use metal to metal as although it has higher friction it is a lot stronger to torsion)
*Could you use a screw joint with a bearing
*Do you care if your parts have grease on them forever (it will get into the holes and essentially live there forever)

Otherwise teflon washers will usually be your best bet but if it has to move more than a few times (in a match) I usually use a modified bearing joint as it takes out the slop that screws have in c channel

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#9

One person in our program (that I just joined, goodbye old teammate :persevere:)

Made a simple tester that compared different lubricants on high speed, freespinning objects and found that simply WD40 just can’t be beat. It’s technically not a lubricant, and how long it stays on is debatable, but it’s very consistency seems to outdo graphite, white lithium, ECT.

We mostly just use nylon spacers.
If you can get your robot to work reliably without lubricant, and THEN put some on, awesome.

I for one would not trust a robot that only works with good lubrication. One more thing to go wrong.

#10

depends on a couple of factors, but in general, metal on teflon on metal will be lower friction than metal on nylon on metal, but metal on metal with lubricant SHOULD be as low friction as metal on teflon on metal. the difference is, plastic is self lubricating. you won’t have to reapply the lubricant. if the lubricant on the metal comes off, you’re screwed. as someone who’s worked with ball bearings before (steel on steel), when you don’t have lubricant between the rotating thingy and non rotating thingy, your bearings explode. this is why bearings are often sealed or have some kind of lubricant retention system (or just extremely thick grease that gets all over everything and doesn’t go anywhere). in general, i’d go with some cheap nylon washers to play it safe, and add some silicone-teflon lubricant for good measure (surface roughness is not always ideal)

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