keyway and key design
keyway and key design
(OP)
Hey, I'm new to this foruma and I have a question about key design. I have a rotating shaft and hub transmitting 2000ft-lb of torque. How do I calculate what size key I need in order to have the key not shear?
It's been a while since I have done any of this kind of design, any help is appreciated.
Thanks in advance,
-James
It's been a while since I have done any of this kind of design, any help is appreciated.
Thanks in advance,
-James





RE: keyway and key design
RE: keyway and key design
RE: keyway and key design
thanks again,
James
RE: keyway and key design
Torque on shaft divided by radius of shaft gives tangential (shear) force divided by the area of your key. Change the length of the key as appropriate to get your F.S. The width remains per the standard as defined in the Machinery's Handbook.
--Scott
For some pleasure reading, try FAQ731-376
RE: keyway and key design
-James
RE: keyway and key design
You need to keep in mind that the key will be loaded transversly, and its strength will be lower than the usual long. test properties. It can be MUCH weaker if the steel isn't "clean".
RE: keyway and key design
Thanks again for any advice.
learning lots today
-James
RE: keyway and key design
Will there be a lot of starts and stops?
You mentioned "shearing keys" did you want this key to shear as a safety feature?
There are quite a few materials available off the shelf but would meed a little more information for a firm recommendation.
RE: keyway and key design
I don't want the key to shear as a safety factory at the moment because I am just doing this for testing. There will be a lot of starts and stops though. I am restricted to about 2 - 2 1/4 in dia on the hub size, length is not an issue.
also does anyone have a good web site for material information? Such as modulus of elasticity, modulus in shear, etc.. I looked in the Machinery's handbook but I'm not sure what number I should be using.
Thanks again
RE: keyway and key design
http://www.matweb.com
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: keyway and key design
3000 Nm, r=.015, F= 200 000N, so you must have at least 150 mm of keyway at the yield strength of mild steel, that is quite ridiculous.
Cheers
Greg Locock
RE: keyway and key design
For reference, the standard SAE F spline 8/16 DP 15Tooth and 1 inch length, it has a major diameter of 2 inch and a torque capacity of 24,245 lb-in at 25,000 psi shaft stress. (see SAE J744). Using higher strength materials and longer lengths can lead to smaller diameter splines, such as SAE C-C spline 17 tooth 12/24 DP, 1-1/2 MAJOR DIAMETER and 0.7 inch length rated at 10,777 lb-in at 25,000 psi shaft stress. Using a 1.56 inch long spline will give you the required 2000 lb-ft. This will still leave .38 inch material wall section per side in the hub.
For more information on keyed shafts see Standard Handbook of Machine Design, (Shigley, Mischke), McGraw-Hill, (Chapter on Couplings).
Howard Schwerdlin