Gear Reduction Calculation

Guys

how do i take motor rpm from a drive and get roll rpm when there is a gear box between the motor and the roll. How can i calculate the gear box ratio? What is the formula?

Also i need to determine meters per minute and feet per minute of material from the roll? I assume the roll diameter factors in but what is the best way to calculate this in the plc?

Sorry if this one sounds lame but this is my first crack at this.

Measure motor rpm, measure roll rpm

Gear box ratio = motor rpm/roll rpm (or it may be stamped on the rearox)

Roll surface speed = roll rpm * roll circumference

Roll circumference = roll diameter * pi

On a similar roll they have motor rpm divided by 727.0594 to get meters per minute but they give no reference to what that number is or where it is derived from? Any ideas?

Most Gearboxes will state the gear ratio on the tag. For instance, if the ratio is 20:1 then it takes 20 turns at the input to give you one turn at the output. If you can't find a tag then you will have to measure it.

The ratio you mention in the other application is derrived from the equations L D[AR2,P#0.0] gave you. The gear ratio itself will not have any units but make sure the radius units jive with the units for your linear speed.