Thread: Shafting size, keyways, and Dr. Joe's Drill Shaft
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Unread 03-12-2001, 21:44
Alan Ing Alan Ing is offline
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Hi all, thanks for you replies.

Ken,

Thanks for your suggestion as it shows some good thought. A 12mm to 1/2" bushing is pretty tough to make. That means I would need to have a wall thickness of only .0138" (about 3-1/2 sheets of bond paper) which would be difficult to make on a mill. I think your shim idea would probably work, but might present us problem if I want to be able to pull the shaft while trying to size our final drive ratio.

Andre,

Great suggestion, Just last night it occured to me that it might be possible to replace the transmission bearing with a 1/2" bushing. If you don't mind, what sort of bushing did you use. Did you use a 1/2" sintered bronze bearing? I think I'll dissassemble our spare transmission tonight and take a look.

Joe,

Thank you for your insight about keyways and trantorques. Sounds like the trantorque is a great device. The one thing I notice though, is that a 12mm trantorque has an O.D. of .886" which is fairly large. What is the minimum wall thickness that can be used with a trantorque? As an example, lets say I purchased a 12 tooth No.35 sprocket from SPI. This has a hub diameter of 1-7/32". with a 1/2" bore. If I bored it out to .886" to fit the trantorque, that would leave a wall thickness of .166" is that enough? How about a wall thickness of .12" which is what I would get with a 18 tooth No. 25 sprocket?

Our team has always used double set screws on a 1/2" shaft with milled flats. This has worked for us, and with a lot of loctite has held up, but I get the feeling we were pushing our luck last year, as without the loctite, they would get loose. Our robot had a ton of traction last year which abused those set screws. I was thinking that a key way would be the way to go, but I like the idea of the trantorque as it would allow us to dissassemble things more easily. Our team has no experience with them, but maybe this will be the year.

Thanks all!

Alan