Measuring RPMs on old Delta lathe

[wardnc]

I have an old Delta/Rockwell lathe driven by a four step spindle pulley and an old motor suspended by a V-belt. Can anyone suggest how I can measure or estimate the four speeds on this lathe?

Thanks,
wardnc

 

[jhreed]

start out with the motor rpm (1750 rpm?). the pulleys give you a ratio. let's say the pulley on the motor, the left hand groove has a diameter of 2" and the left hand groove on the spindle has a 4" diameter. that is a 2 to 1 ratio. so, for every 2 revolutions of the motor you wil have 1 revolution of the spindle. 1750/2=875 rpm

 

[wardnc]

Thanks for the help. Sounds simple once you understand .

 

[Guy in Paradise]

Get one of these

http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXPT31&P=8

Probably the easiest way.

If the motor has rpm labeled on it, then you can measure the pulley diameters and take ratios. Not always precise.

Rpm of spindle = rpm of motor x ((diameter of motor pulley)/(diameter of spindle pulley))