Quote:
Originally Posted by Tristan Lall
I know you're probably trying to avoid machining it, but if you filled the bearing portion of the threads with a metal-filled epoxy and lathed it down to the correct diameter, you'd do away with the majority of the stress concentration problems, and ensure yourself a precise fit in the bearing. And if you were using mild steel (not hardened) threaded rod, you could even fill it with weld filler, and lathe that down (you'd probably want to clamp it when depositing the weld filler, to avoid distorting the rod, though).
However, I'd tend to agree with the use of a shoulder bolt and a locked nut (threadlocker or a good-quality locknut). McMaster sells several Ø3/8" shoulder bolts in appropriately long sizes, and Flexloc locknuts (which tend to be very secure).
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The previous revision used shoulder bolts as axles and used the bolt head as a sort of hex shaft. It required a number of custom cut parts that I tried to eliminate with this version.
It seems like it'd be simpler for us to thread rod on our own than to mess with filler, even. It's probably not very much work, all things considered, and it'd save a lot of headaches.
Quote:
Originally Posted by Dick Linn
What will transmit the torque and keep everything from slipping?
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I'm not sure if I understand what you mean by slipping. If, as I mention above, we thread our own rod, we can stop the coupling nut from tightening itself down against the bearing blocks by ending the threads before they get inside the bearing. The coupling nut will turn as far as it can on the thread before driving the shaft -- and likewise, on the other side, that coupling will turn the wheel after it can no longer move on the thread.
That's the idea, anyway.