Need help in design for anti-backlash spur gears

[joel2005]

Hello,
I wish to design an "anti-backlash" spur gears pair with torque of 100Nm and very slow speed.
I could not find any material about it.

Thanks in advance,
Joel

 

[israelkk]

Anti-backlash gears are mainly for servo positioning use and therefore are applying small torques to avoid errors on measurements. What you are trying to do is to use anti-backlash gears for high load torques. This is in principal a bad idea. For gears to correctly operate for long and/or reasonable life a backlash must be allowed for the oil/grease to penetrate between the mating teeth. If you will use such high load anti-backlash gears the gear life will be very short.

For ideas and sample of anti-backlash arrangements see Gear Design and Aplication, Nicholas P. Chironis, McGRAW-Hill 1967 pages 235-242

 

[joel2005]

Dear Israelkk,
Thank you.I am from Israel, and this is my first time to use this forum.
The application is for 0.1 RPM output speed,and life required is very small.Possibly 2000-5000 hours.
It is a stand by application.
I have a strong feeling that it will work, just do not know
how to design-calculate the springs, and even the teeth.
My "finger rule" is to use set of gears with module 2-2.5
17-22 teeth in pinion, and ratio of 4-5.
Width will be 10-15mm for each half of gear part, and double for pinion.

Thanks, and have a nice weekend,
Joel

 

[sreid]

Possibly for what you need to do you might consider a Cyclo Reducer.

http://www.smcyclo.com/products/precision/fine_cyclo.shtml

 

[drawoh]

Postjoel2005,

An alternative to anti-backlash gears is to spring load the gears together. Gear fabricators can cut the gears oversize so that the involute form is optimized for constant contact.

JHG

 

[joel2005]

Dear drawoh,
Can you send me a sketch of this idea ?
Thanks.
Joel

 

[drawoh]

joel2005,

I designed one of these a long time ago. I do not have a sketch handy. One gear was on a pivot arm that was loaded against the other gear by a spring. There are all sorts of ways to implement the concept.

Also, you can look into Harmonic Drive.

JHG

 

[GregLocock]

In the automotive world two gears sprung loaded against each other to eliminate free play are called scissor gears, they are used on the camshaft drive of some Hondas.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.