Quote:
Originally Posted by msimon785
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.
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Hmm. How and why did they break? Radial load, axial, misalignment? Any chance you remember? Thanks for the input.
Quote:
Originally Posted by Garret
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.
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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!