Thread: Help with math

I know there's a thread discussing this, however i'm lousy at math.
I have a small .5 amp 1600 rpm motot with 1/4" shaft. I would like to use it for slow grinding if this is possible. If it is then what size pulleys would i use to bring a 3" gringing stone to approx. 90 to 160 rpm or what ever surface speed I would need.
Hope this explaines what I'm trying to do.
Thanks for any input.

There should be a direct linear relationship between the difference in rotational speed and the difference in pulley diameters. So for you to step down a 1600 rpm motor to a 160 rpm grinding wheel you will need to go from a 1" pulley on the motor to a 10" pulley on the grinding wheel shaft. This is probably better done with an intermediate "jack" shaft between the driving and driven members so you have 2 steps to reduce the size differential in pulleys.

good luck

Originally Posted by Bruce

There should be a direct linear relationship between the difference in rotational speed and the difference in pulley diameters. So for you to step down a 1600 rpm motor to a 160 rpm grinding wheel you will need to go from a 1" pulley on the motor to a 10" pulley on the grinding wheel shaft. This is probably better done with an intermediate "jack" shaft between the driving and driven members so you have 2 steps to reduce the size differential in pulleys.

good luck

Thanks, but what would the jack pully and new grind wheel pully be ?
As I said i'm a math idiot

How to Calculate Sheave Ratio | eHow.com

The issue here is physics, not math.

the linear grinding speed is not going to change with a simple two-pulleys system. the only thing you will accomplish is that the smaller wheel will make much more revolutions per minute than the larger wheel, and the relationship is linear, i.e. the wheel with twice smaller radius/diameter will spin twice as fast, the wheel with three times larger radius/diameter will spin three times slower.

however the speed that the belt is moving relative to the steel is going to be exactly the same on both wheels.

If you want to decrease the linear speed you'll have to use more complicated system where you have two pulleys stacked fixed on each other so that they always make the same number of revolutions per minute, and then the linear speed is directly proportional to the radius, i.e. twice smaller radius means twice smaller speed.

Originally Posted by gugi

the linear grinding speed is not going to change with a simple two-pulleys system. the only thing you will accomplish is that the smaller wheel will make much more revolutions per minute than the larger wheel, and the relationship is linear, i.e. the wheel with twice smaller radius/diameter will spin twice as fast, the wheel with three times larger radius/diameter will spin three times slower.

however the speed that the belt is moving relative to the steel is going to be exactly the same on both wheels.

If you want to decrease the linear speed you'll have to use more complicated system where you have two pulleys stacked fixed on each other so that they always make the same number of revolutions per minute, and then the linear speed is directly proportional to the radius, i.e. twice smaller radius means twice smaller speed.

Thanks but that really jumbled my head!