Torque Loss
Torque Loss
(OP)
Good afternoon!
We have a motor that can produce 1500ft-lbs of torque at 500rpm. We need to be able to reach 2500rpms though. If we use a 5:1 gear ratio how much torque will be lost? Also, this would put a lot of stress on the gears, what type of metals would you use to produce them? Thank you everyone!
Doc
We have a motor that can produce 1500ft-lbs of torque at 500rpm. We need to be able to reach 2500rpms though. If we use a 5:1 gear ratio how much torque will be lost? Also, this would put a lot of stress on the gears, what type of metals would you use to produce them? Thank you everyone!
Doc





RE: Torque Loss
RE: Torque Loss
Unless you will give more information on the space and weight limitations you have for the gearbox there is no point recommend materials. The larger the space and weight the lower strength materials you can use.
RE: Torque Loss
So if push comes to shove I reckon an automotive diff would give you an idea of component sizes.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Torque Loss
RE: Torque Loss
Then you may consider using a Variable Frequency Drive which could allow you to run higher speeds out of the motor. After all of that, then you have to make sure that your mechanical elements can handle the torque loading and survive the requirements you state. THEN it may require a second iteration of calculation.
TygerDawg
RE: Torque Loss
if reliability is that critical, how reliable is your motor, or the whole system ?
RE: Torque Loss
Also how did you come up with the 300lbs from the 1500 I stated? Is there a formula?
RE: Torque Loss
RE: Torque Loss
its an easy bit of math to caculate torque reduction from RPM increases. (or I always thought so, linear equations)
Hows an 85% efficiency factor sound?
So 1500ft-lbs @ 500rpm to 2500rpm is:
2500/500 = gear ratio ~1:5 increasing speed gear
Then at 100% efficiency the resulting torque would be 300ft-lbs (right, I mean if I gear up I loose torque at the same ratio as I gain speed) so by multiplying by .85 (frictional, flexure, fluid friction losses)
you get ~255ft-lbs available......
Seems easy to me, if you need an in line speed increase try a planitary type of gear, if you need to change the direction then you might change rotation direction and then you might run through two or three gears.
(I guessed at the efficiency, I really have no clue as to the available efficiencies.... I just think that this is not too hard of a problem and could be built out of standard gearing suppliers catalogs.....)
Oh, gears are generally made from alloy steels that may or may not be case hardened. (at least from what Ive seen. I'm sure that gears are made from everything including glass, but for your application thats what I would use, if weight wasn't a huge issue.
Nick
I love materials science!
RE: Torque Loss
RE: Torque Loss
RE: Torque Loss
Simple speed increasers produce extreme tooth loads and pinion bearing loads, even with modest ratios. Five to one is not a modest ratio in the world of speed increasers. Planetary gearsets nominally distribute the load, but require selective fit gears and probably controlled flexibility of the carrier in order to make that happen, and have the unfortunate habit of fragging themselves upon failure, so development is going to be expensive.
You need to find and hire an engineer who _really_ knows gears. This is not a two-week project, even for an expert. Don't even bother talking to the sales engineers for industrial speed reducers, except to identify the factory engineers you will want to steal from them.
Mike Halloran
Pembroke Pines, FL, USA
RE: Torque Loss
RE: Torque Loss
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Torque Loss