motor torque question

have a question. Hope i can ask it so it makes sense.
Have a gear motor that is rated at 650 lb_in that turns 47 RPM at max speed.

Need to use this existing motor in a machine and turn a roller approx 115 rpm at max speed.

Gear motor has a 5 inch sprocket on it. If i put a 2 inch sprocket on the roller then the ratio would be 5 to 2.5 Would the the roller with the 2 inch sprocket turn at 47*2.5 = 117.5 rpm for the roller if motor running max speed.

Also, since the motor is rated at 650lb_in and the ratio between the sprocket that is currently on the motor and what will placed on the roller is 2.5, would that cause a difference in the amount of torque that would be availiable at the roller with the 2 inch sprocket.

Thanks for any advice or reply.

Would the roller with the 2 inch sprocket turn at 47*2.5 = 117.5 rpm for the roller if motor running max speed.

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Yes

would that cause a difference in the amount of torque that would be available at the roller with the 2 inch sprocket.

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Yes, the torque would be reduced by a factor of 2.5

Thanks Steve
That was what i was trying to explain to a mechanical so called expert. He kept telling me that it would cause more torque to be availiable at the roller with the 2 inch sprocket, but from what i remember and its been over 35 years since i was in school, just did not believe it.

irondesk40 said:

Thanks Steve
That was what i was trying to explain to a mechanical so called expert. He kept telling me that it would cause more torque to be availiable at the roller with the 2 inch sprocket, but from what i remember and its been over 35 years since i was in school, just did not believe it.

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Show him the link..

https://www.google.com/search?rlz=1......0i131i67k1j0i67k1j0i20i264k1.0.vlnt7MoczYA

Think of the two sprockets with a chain between them. In your case, the shaft with the 5" sprocket has 650 in-lbs of torque. That means the tension in the chain is 260 pounds (650/2.5).
That same tension is at the 2" sprocket, but now it can only develop 260 inch-pounds of torque.

Thanks.. Google link very helpful. Bookmarked it.

This kind of question seems to come up often.

This is really a First Law of Thermodynamics question. The energy and power has to be the same all the way through a system. (Less friction losses, of course. This energy isn't lost, it just turns to heat.)

Torque is always inversely proportional to speed. If you slow your shafts, you increase your torque.

T = hp x 5252 / rpm

In the above T = Torque as ft-lb