How to connect two shafts
How to connect two shafts
(OP)
I want to connect two shafts directly to each other. They are small diameter and have large axial loads, they push and pull, but no torque. I can thread them together, but the required torque preload to prevent separation is very large. I am trying to eliminate a ball joint, which has wear. I do not have room for a flange with bolts. Are there any other choices?





RE: How to connect two shafts
What is the magnitude of the forces?
RE: How to connect two shafts
To someone who designs watches, a "small" shaft may be less than a millimeter, and a "large" load a few grams.
RE: How to connect two shafts
If connection needs to allow for mis alignment, then a "H" clevis with the ends at right angles, again drilled and pinned (the pin could be a through bolt)
RE: How to connect two shafts
Does it have to be disassemblable? If not, you could thread both rods, screw them into a coupling, then weld it.
Don
Kansas City
RE: How to connect two shafts
otherwise i like byrdj's idea of a sleeve
RE: How to connect two shafts
RE: How to connect two shafts
If you thread them, why do they need high (any) preload? The idea with high preload in fastened joints is to prevent high stress amplitude in the fastener, but if your shafts already see the high amplitude, then just thread them and use low preload (enough to remove allowances/tolerances).
Regards,
Cory
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RE: How to connect two shafts
I guess I agree Cory, sounds logical. Sleeve with pins sounds good also.
RE: How to connect two shafts
"Art without engineering is dreaming; Engineering without art is calculating."
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RE: How to connect two shafts
Oilfield workstring tubing undergoes exactly the same situation that you're talking about. It gets both pushed and pulled repeatedly during a well servicing operation and a well-designed and properly-torqued joint doesn't ever come undone.
2 inch OD with 15000 lbs seems like you have plenty of room to play with. Using standard ASTM SA53 SCH 40 1-1/2" nominal OD black steel pipe with 35,000 psi yield has an OD of 1.900 and an ID of 1.610 and results in a stress of only 18ksi and a SF of 1.86 against yield. SCH 80 gives you 14ksi and 2.5 SF. A tapered thread joint can come very close to 100% efficiency. Of course, buckling calcs may show lower SF.
To use 1-1/2" nominal pipe, though, you would machine a tapered-thread plug to connect the two on the ID as opposed to how it's normally done, which is on the OD.
Use the removable Loctite.
-T
Engineering is not the science behind building. It is the science behind not building.
RE: How to connect two shafts
for pins, if you can't fit standard bolts (and nuts), you could get a two piece pin, with one 1/2 having an internal thread.
RE: How to connect two shafts
Cory
RE: How to connect two shafts
RE: How to connect two shafts
RE: How to connect two shafts
RE: How to connect two shafts
Failure is a prerequisite of successful design
RE: How to connect two shafts
one thing to think of is the connection between the sleeve and the tube (shaft) will need to transmit moment as effectively as the shaft; ie, if there is moment flexibility between the two shafts then they won't act as a single shaft (in compression), and two shafts (joined by a hinge) would have a reduced euler load (no?)