Just Another Shaft Fit Question
Just Another Shaft Fit Question
(OP)
Hi,
I'm interested in properly specifying the bore for a keyed sprocket hub. The 2" sprocket will sit over a 3/4" drive shaft that rotates ~3rpm and ~1000 lb load. Everything has been sized except for the fit class.
I have just about exhausted my internet resources looking to find which class fit I should pick from the Machinery's Handbook.
"RC1 Close sliding fits are intended for the accurate location of parts that must assemble without perceptible play." -Machinery's Handbook 27th
RC 1 looks the most tempting as it's description is somewhat similar to the fit I experienced when disassembling the keyed crank shaft on my old ChevyBlazer, but then again that crank spins much faster and I'm sure delivered higher loads.
Any thoughts... Thanks in advance
I'm interested in properly specifying the bore for a keyed sprocket hub. The 2" sprocket will sit over a 3/4" drive shaft that rotates ~3rpm and ~1000 lb load. Everything has been sized except for the fit class.
I have just about exhausted my internet resources looking to find which class fit I should pick from the Machinery's Handbook.
"RC1 Close sliding fits are intended for the accurate location of parts that must assemble without perceptible play." -Machinery's Handbook 27th
RC 1 looks the most tempting as it's description is somewhat similar to the fit I experienced when disassembling the keyed crank shaft on my old ChevyBlazer, but then again that crank spins much faster and I'm sure delivered higher loads.
Any thoughts... Thanks in advance
Failure is a prerequisite of successful design





RE: Just Another Shaft Fit Question
Ted
RE: Just Another Shaft Fit Question
Subjecting slip fitted keyed components to loads that vary in direction or force will result in micro-motion or larger motion, and fretting, wear, loosening and heart-ache.
That 3/4 inch shaft sounds kind of dainty.
RE: Just Another Shaft Fit Question
I wrote several Excel spreadsheet using the University of Tennessee at Martin, mechancial engineering course. Google to that website and look for the lecture notes in the subject. It is a good presentation. Shigley does a fair presentation in his design textbooks, an alternate source suggestion.
Shrink fits are interference fits and follow the classical text on Thick Wall Pressure Vessel theory. Therefore the Von Mises-Hencky model would apply and be of value in your computations.
Good luck with it.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Just Another Shaft Fit Question
The original Mazda Miata had some issues with dampers eating crank snouts. Probably not coincidentally it Usually happened after repairs that could result in less than specified bolt torque. The factory upgraded to a larger full length damper snout with a larger bolt for harder clamping.