Key/Keyway for Torque Transmission
Key/Keyway for Torque Transmission
(OP)
I have the following set-up:
A gear is mounted to a ferrofluidic feedthrough (vacuum to atmosphere seal that allows rotational motion to be transmitted via a ferrofluidic vacuum seal). A shaft (1.5"-2.0" diameter) travels through the axis of the gear and also moves 0.875" up and down.
I need to transfer the torque from the gear to the shaft. I'm thinking I can put a key on the gear and a keyway in the shaft. Does anyone have any literature on a situation like this? I'm looking for information on recommended materials, design, tolerances, etc. I want backlash to be minimal, but, at the same time, I don't want to cause too much drag on the linear portion of the motion.
Thanks in advance for any help.
Dan
A gear is mounted to a ferrofluidic feedthrough (vacuum to atmosphere seal that allows rotational motion to be transmitted via a ferrofluidic vacuum seal). A shaft (1.5"-2.0" diameter) travels through the axis of the gear and also moves 0.875" up and down.
I need to transfer the torque from the gear to the shaft. I'm thinking I can put a key on the gear and a keyway in the shaft. Does anyone have any literature on a situation like this? I'm looking for information on recommended materials, design, tolerances, etc. I want backlash to be minimal, but, at the same time, I don't want to cause too much drag on the linear portion of the motion.
Thanks in advance for any help.
Dan





RE: Key/Keyway for Torque Transmission
Why not use a long (axially) gear on one shaft and a short one on the other shaft?
If you insist on using a gear (say if you are using a chain drive) then investigate ballsplines.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Key/Keyway for Torque Transmission
Perhaps a very small linear rail (like those made by THK) mounted on the shaft would work. But, I'd have to 'sink' this design into the shaft and I also need to run four gun-drilled bores (for cooling gas and water) up the shaft, so I'm not sure if there will be room.
RE: Key/Keyway for Torque Transmission
If you analyse the forces throughout the system you may find a feasibel solution.
Also, how is the gear located axially?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Key/Keyway for Torque Transmission
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RE: Key/Keyway for Torque Transmission
Mike Halloran
Pembroke Pines, FL, USA
RE: Key/Keyway for Torque Transmission
What is the level of vacuum?
How much torque?
Does the linear motion have to occur simultaneously with rotation?
RE: Key/Keyway for Torque Transmission
RE: Key/Keyway for Torque Transmission
Ex: Bolt the gear to the seal hub, but not with regular bolts; use shafting with threaded ends, or shoulder bolts, so you get an array of cylindrical features extending out into the air from the gear face. Fit a large flange to the end of the shaft and equip it with bearings to slide on the shoulder screws. You will probably need to matchmark the gear and the flange; it's an awkward assembly, and if it fits together at all, it will fit in only one orientation.
It's not the sort of thing I would put in production, but a good machinist can make _one_ that works.
Mike Halloran
Pembroke Pines, FL, USA
RE: Key/Keyway for Torque Transmission
Thanks for the response. Unfortunately, that idea won't work for two reasons: A) this needs to be a production design and B)I can't make the overall diameter of the shaft bigger than 2" due to some other design constraints.
All of these ideas are great though. It gives me different paths to go down. It's amazing what another set of 'eyes' can do within design.
RE: Key/Keyway for Torque Transmission
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Key/Keyway for Torque Transmission
RE: Key/Keyway for Torque Transmission
RE: Key/Keyway for Torque Transmission
RE: Key/Keyway for Torque Transmission
RE: Key/Keyway for Torque Transmission
The side of the surface of the key that is sliding should be large enough that the pressure does not exceed 6,000 psi or it will not slide. The force required to slide it is affected by the normal force and the coefficient of friction.
RE: Key/Keyway for Torque Transmission