Coupling two threaded shafts (engine and alternator)?
Coupling two threaded shafts (engine and alternator)?
(OP)
I'm having some trouble finding an acceptable solution to direct coupling of an M8x1.25 Honda mini 4-stroke engine shaft to an M14x1.5 alternator shaft. I'd like to couple them end to end since the RPMs will be well-matched to obtain the output I'm expecting.
There are many spider couplings, but they all have a bore size for keyed shafts. Is there any such coupling for threaded shafts?
Ideally, there’d be a spider coupling which didn’t just have a bore, but a metric thread. And, I’d need two of them with different threads (M8x1.25 and M14x1.5) with the same OD so they can mate, using a spider between them to handle any offset. Threaded hubs simply are not available they’re all bored with/without an ANSI keyway.
One idea I have is to turn some material and make two sleeves with the same OD, but each would be tapped to the threads on the engine and alternator. I’d machine a flat spot for the set screw, too, and put a spider coupling over each machined shaft after I threaded them onto the alternator and engine. It's not a high-torque situation, but RPMs could reach 6000.
Does anybody have a better idea? What is the minimalist approach to this problem? I can turn, mill and tap without a problem.
Thanks,
robobuilder
There are many spider couplings, but they all have a bore size for keyed shafts. Is there any such coupling for threaded shafts?
Ideally, there’d be a spider coupling which didn’t just have a bore, but a metric thread. And, I’d need two of them with different threads (M8x1.25 and M14x1.5) with the same OD so they can mate, using a spider between them to handle any offset. Threaded hubs simply are not available they’re all bored with/without an ANSI keyway.
One idea I have is to turn some material and make two sleeves with the same OD, but each would be tapped to the threads on the engine and alternator. I’d machine a flat spot for the set screw, too, and put a spider coupling over each machined shaft after I threaded them onto the alternator and engine. It's not a high-torque situation, but RPMs could reach 6000.
Does anybody have a better idea? What is the minimalist approach to this problem? I can turn, mill and tap without a problem.
Thanks,
robobuilder





RE: Coupling two threaded shafts (engine and alternator)?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Coupling two threaded shafts (engine and alternator)?
RE: Coupling two threaded shafts (engine and alternator)?
Personally, I avoid using threads to transfer power. But in this case is may be the most affordable method.
I have also seen some couplings that use "taperlock style" attachment methods like a ring-feder. The diameter will probably grow, but if you can stay in something standard you would be better off.
http://www.ringfeder.com/indexB.htm
RE: Coupling two threaded shafts (engine and alternator)?
M8 and then c'drill and tap to the M14
size in a one piece coupling or collar?
RE: Coupling two threaded shafts (engine and alternator)?
Arn't the shafts tapered, with the threads there only to draw-up a mating tapered hub or pulley?
RE: Coupling two threaded shafts (engine and alternator)?
RE: Coupling two threaded shafts (engine and alternator)?
RE: Coupling two threaded shafts (engine and alternator)?
You are correct regarding the rotation. I must remember "engage brain, then type."
RE: Coupling two threaded shafts (engine and alternator)?
Having considered everything, I'll buy two undersized couplings and tap them as appropriate. As JJPellin suggested, I'll grind a flat spot on each shaft for a set screw so the threads are not continually tightening since both are R-hand. This will let me take it apart.
Thanks much for the input.
- Ken