Needle Bearings for Drivetrain
 

Has anyone investigated whether they'd work well or not? I'm looking into them because they can have considerably smaller OD for the same ID in comparison to ball bearings, and this would allow smaller, lighter axle blocks (it's for a west coast drive train.)

Generally, I've heard they can't support axial loads, but I haven't managed to find any numbers on this. Would they be able to stand up to the rigor of FRC matches? Side impacts could impose a significant amount of force to them, and even turning would put some force on. Anyone have thoughts?

Re: Needle Bearings for Drivetrain
 

While I haven't run any tests on them, we used them on our conveyor this year and broke two from general wear. We were running 5/16 urethane belt at 7.5% stretch. A drivetrain should experience more. I personally would not suggest using them for the purposes of a WCD.

However, I really hope someone chimes in with actual data, because I am curious to know the relationship between what they're rated for and actual recorded results.

Re: Needle Bearings for Drivetrain
 

Generally speaking, needle bearings will handle radial loads far better than ball bearings. However the disadvantage is that they require the shaft to be completely round for the length that it is contact with the bearing, this is because their is no liner (can be purchased separately) inside to prevent the rollers from coming out. The thing about needle bearing not supporting axial load is due to the fact that axial loads will just push whatever is retaining the shaft into the bearing housing, this means that you will need some sort of additional bearing/bushing for axial loads.

My experience has also been that despite better load capacity they don't like to go as fast as ball bearings (though I don't really have any quantitative data to confirm this). I am pretty sure we have used them in some of our really old drivetrains and our swerve (for steering). Needle bearings require different design considerations to work well, I don't see any reason that they wouldn't work on a WCD if everything is taken into consideration.

Re: Needle Bearings for Drivetrain
 

Hmm. How and why did they break? Radial load, axial, misalignment? Any chance you remember? Thanks for the input.

I've also heard the lower speed thing (I believe it's because of the larger contact area that promotes more friction.) McMaster says that the ones I was looking at (5905K133) are rated up to 15000 RPM. Shouldn't be a problem, unless we decide on a max speed of 260 ft/s with 4in wheels (and if we want to go faster, then we can just use bigger wheels. 16in wheels would allow us to break the sound barrier!)

Ah, that's the reason for the low axial loads. Thanks for explaining, I hadn't picked up on that. So some sort of thrust washer, maybe McMaster #7421K7, against the bearing housing (or even the bearing block), would solve that? What other sorts of design concerns might I have to take into account? Thanks for your help!

Re: Needle Bearings for Drivetrain
 

Needle bearing are great for the right application. They are used throughout the drivetrain of you car, particularly in the transmission. They can be used at high speeds such as in turbine applications, albeit with an oil bath. As with many other things in design its a question of is it the right application.

I would say that I have not yet seen a good application for their use in FRC that makes the extra effort worth it. As always use your own good engineering judgement to determine if they are worth the effort and are appropriate for the application.

Re: Needle Bearings for Drivetrain
 

We used AndyMArk Traction wheels for two years. They used needle bearings and we never had a single failure or problem (and that is back when nothing we did could have been considered precision machining:)

Re: Needle Bearings for Drivetrain
 

As said above, needle bearings are definitely usable in the proper FRC applications. 1519 used open needle bearings (MSC #7571169) in 2008 for the rear axle bearings on our "Speed Racer" robot, because they were the only bearings we could get that would fit in the small amount of space we had available. They worked great, although since the ones we used were open within, they did require a fully round shaft (not keyed) where the shaft passes through the bearing.

They can definitely handle high loads and high RPM. My Triumph TR6 car uses needle bearings in all six of the driveshaft / axleshaft U-joints and they handle both high torque and high speed pretty well.

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

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.)

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.

Re: Needle Bearings for Drivetrain
 

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

Re: Needle Bearings for Drivetrain
 

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

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

To replace the bearings.

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

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?

Re: Needle Bearings for Drivetrain
 

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.

Re: Needle Bearings for Drivetrain
 

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.