Say I have a 50W motor which develops max power at say 8000rpm and through reduction gearing of 8000:1 (to make the maths simple) drives a shaft, does that shaft have the same amount of torque or "grunt" (the technical term) as a plain, ungeared 400kW motor? And if not, why not? ;->
Gearing and Torque
Apr 07, 2016
13 Replies
Oh please don't start this again.
power = torque x speed
NT
Unless the gear shafts are running on frictionless bearings, may it be assumed the simple maths overlooks any heat lost during the reduction. Which must have come from somewhere.
michael adams
...
Completely different question altogether.
If you assume that your reduction gearing is 100% efficient - which it isn't in practice - and that your 400kW motor also runs at 8000rpm - which you haven't specified - the torques generated will be equal.
But X Nm at 1rpm is rather less useful than X Nm at 8000rpm!
For example, if you used your 50w motor to power a car, it would move rather slowly, even though it might go up a steep hill - at about one mile a fortnight!
But if you're 5 and sat on a kid's roundabout, 1rpm is a lot more useful than 8000 :)
NT
Speed x torque = power.
So if you half the speed with a gearbox, you will get twice the torque.
No it isn't, really. And as before, you have deliberately left out the key piece of information which would make it trivial to answer.
You try to entertain a kid on a roundabout at 1RPM.
One per second maybe...
Andy
I'd guess 8000:1 gearing is going to be horribly inefficient?
it beats trying to entertain one doing 8000 rpm.
NT
it's the sort of thing you might get in a 24hr mechanical timer. About three worm gear sets in series.
Depends on what sort of motor it is. Many small motors are electronically controlled these days so its not as simple a question as it might otherwise be. Brian
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