Gear speed

[R1100S]

Hello, I am looking for a reference as to how fast I can spin helical gears based on their size. The only info I have found is a statement in my Mechanic Design Handbook that says if the Pitch Line Velocity goes above 2000 ft./min., cooling should be considered. Any good sources of on this, or at least rules of thumb?

 

[zincibro]

Hi R1100S:
I guess it is good to look for some AGMA Standards. There are so many consideration issues; so, what type of application will you be doing and what speed are you seeking I think finding aswers to these questions might help you more.

Regards

 

[Tmoose]

I think that is, at least partly, a heat generation (due to oil shear/churning) limit, not a structural limit. In the past few years I witnessed/endured some painful situations resulting from real low estimates of heat generation by pretty big name gearbox suppliers houses. Some kind of minimal lubrication system (like air-oil as used in high speed ball and roller bearings) seems to be the answer. I think I read The Nascar guys have moved to controlled lube for trans and rear axles partly for heat (thus power) reasons.

Whatcha making?

 

[SKinzel]

A couple of AGMA standards that might be useful:
917-B97 Design Manual for Parallel Shaft Fine-Pitch Gearing

2001-C95 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth

 

[geardup]

2000-2500 ft./min has always been a good rule of thumb for splash systems. Actual testing above 2500 is highly recommended. The major problem with speeds above 2500 ft./min is the speed of the gears will cut a channel in the oil bath generating excess heat caused by lack of lubrication and cooling.

gary@gearmfg.com

 

[R1100S]

Thanks for the replies. It looks like I am going to go with smaller gears, running below 2000 ft/min. They are to run the balance shafts on a large single cylinder engine. I've got plenty of engine oil flowing, so lubrication and cooling should not be a problem.

 

[Carburize]

Engine oils do not typically make very good gear lubricants, be careful!

 

[R1100S]

Thanks for the advice Carburize, but since I already have engine oil circulating, I don't want the added complexity of another lube circut.