Needle Bearings for Drivetrain

[Garret]

I agree with most all of the above comments, but wanted to add that if you are that limited on space, a good plain bearing(also called bushings) will work most of the time. My team used bronze bushings on the drive axles one year and had no issues with them. The increase in friction did not seem to be a major issue either as the loads on these bearings is pretty low.

We used these when we rebuilt our 2009 shooter for our demo bot (after 3 years of heavy use it was beginning to fall apart). The side loads on this are not very high but the speeds are really fast (we have ours in a "loose" mounting with lots of grease); they have held up pretty well through at least 30 hours of operation of the shooter since installed last fall. The only thing that I would worry about is excess wear to the bearing, shaft, or wherever the bearing is mounted.

Again its really up to the designer, all of the bearings (if used properly) can perform well enough for FIRST robotics purposes.

[FenixPheonix]

Originally Posted by Mr. Mike

Needle bearings must be run on hardened and ground shafts. If the shaft is soft or has a keyway there are sleeves that can be used as an inner race.

Hmm, so definitely a no-go on a 7075 aluminum shaft? Too bad. No way around it? I'll look into the liners. Shame it takes the size up a bit, though. Interesting, though, McMaster only mentions the "use on hardened and preground shafts" thing on the high precision ones. (EDIT: Scratch that, I just noticed it.)

Originally Posted by Justin Stiltner

I agree with most all of the above comments, but wanted to add that if you are that limited on space, a good plain bearing(also called bushings) will work most of the time. My team used bronze bushings on the drive axles one year and had no issues with them. The increase in friction did not seem to be a major issue either as the loads on these bearings is pretty low.

I won't deny that space is a concern here. The smaller I can get the OD on this, the closer to the bottom of the box tubing I can pull the bearing blocks, and the smaller the wheels I need. I'm not going to harp on the advantages here, they've been discussed a lot already, but single stage gearboxes are one of my thoughts. However, I'd prefer to use bearings, since they are more efficient. Thanks for the input, though.

[MrForbes]

You should look into the Igus bushings, specifically the flanged ones. They might be just what you need.

[FenixPheonix]

Originally Posted by squirrel

You should look into the Igus bushings, specifically the flanged ones. They might be just what you need.

To replace the bearings, or as liners in needle bearings? I'll look into them. Thanks.

[ratdude747]

I personally am not a fan of needle bearings. From what I have been told in the past, they don't handle abuse and imperfect machining very well. They have their uses.. but not as FRC axle bearings.

I'd stick with the usual ball bearing setup...

If you want to experiment, oil impregnated bronze bushings might be worth a try.

[MrForbes]

Originally Posted by FenixPheonix

To replace the bearings, or as liners in needle bearings? I'll look into them. Thanks.

To replace the bearings.

[FrankJ]

Igus has a lot of application information on their web site. If you notice the kit of parts Igus AL shaft has an hard anodized coating. It helps with friction & wear.

Both bushings & needle bearings will need some kind of thrust bearing to adsorb the axial load. Simplest case is a washer.

Rolling bearings like ball & needle need hardened races because the high contact pressures. Bushing have considerably lower contact pressure & generally have one hard & one relatively softer surface. Oil lubricated plain bearings (bushings) are a completely different animal since the sliding surfaces are not suppose to contact each other.

[FenixPheonix]

Thanks for the input, all. I'll continue doing some looking into these. It sounds like bushings, of both the Igus and bronze variety, might be worth a shot.

Before anyone asks, though, don't expect to see 751 with plastic bushings and custom 2.5" wheels. We're still trying to get WCD up and running, we're not ready to play around too much with the base design yet (and doing custom wheels wouldn't be fun without CNC. Rotary table time! Hmm, this merits thought...) This is purely a personal project for fun, and is currently entirely theoretical. If I've got time this summer, I'll see about putting together some prototypes to submit to the team. I'll try to get a CAD together in the next couple of days.

Could I use a flanged bushing instead of having a thrust washer or bearing?

[MrForbes]

igus makes flanged bushings, that's one reason I suggested them.

Be sure to read all the application data and load specs and speed ratings, to make sure they would work.

[AdamHeard]

Needle bearings would work, as beaten to death already in this thread, but would need a separate thrust provision (ideally a thrust bearing if efficiency is important to you).

We've talked about trying needles to make a smaller west coast drive, but the rework required wasn't worth it to us.

I see no reason whatsoever to deviate from a standard ball bearing setup for a west coast, the suggested options of bushings are less efficient by a good deal. Look at 254's bearing blocks, our bearing blocks and maybe the team 221 bearing blocks for inspiration.