Mechanical Drive Efficiency

[FredRosse]

I would like to determine the mechanical drive efficiency for common roller chain, V-belt drives, and timing belt drives. All of the vendor information I can find gives rather vague information, that drives are "high efficiency" or something similar. Quantification is also vague "90%-98%" or similar quotes.

Is there any place where real mechanical drive efficiency numbers can be examined, calculated, compared?

 

[GregLocock]

I haven't seen much real data. I think calculating it might be a bit tricky, probably better off measuring it.

Numbers I have seen from real life tests, by people I trust, at low speed:

Roller chain 98% Timing belt 90%

Cheers

Greg Locock

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

 

[Philrock]

I agree that manufacturer claims for efficiency tend to be vague. In my experience, they are also overly optimistic - especially for belt drives. In their defense, there are many variables not under their control that contribute to losses, such as misalignment, contamination, lubrication, wear, etc.

Efficiency gets especially low when operating at a small percentage of capacity.

Common practice is to simply be very conservative. If you really need accurate numbers, you have to experiment, and take care to duplicate worst case service conditions.

 

[Barry1961]

Just to add some more variables to what Philrock mentioned…..

Temperature can have a big effect on lubrication and stiffness of belts.

Sprocket or pulley radius on how much force is required to bend belting.

Speed of drive in relation to lubrication type.

Barry1961

 

[HCBFlash]

You'll have to get there by doing all the calc's for sizing and optimal loading. Best efficiencies always fall in a narrow range of operating parameters. This is especially true of belts.

Please let us all know how this works out for you!

 

[gto1965]

V-belts are up to 97% efficient if sized and tensioned properly. Synchronous (timing) belts are approximately 98% or more efficient. Most sources indicate approximations because each drive will be different. Larger sprockets and smaller ratios improve efficiency. Also, as previously stated, the bending modulus of the belt and tooth form contribute to the efficiency of sync belts. I've seen chain drives quoted as 85 to 90% efficient. New high strength sync belts like PolyChain GT2 and PowerGrip GT2 have many advantages over chain including: weight; noise; efficiency; maintenance free; no lubrication requirement.

Bruce Jackson
Project Engineer
Gates Advanced Technical Center
Rochester Hills, MI