Spindle speeds/rpm of the Atlas 12" lathe

[chevydyl]

So the PO of my lathe purchased a new motor and installed it and wire it for 120v. Looking through the book it says the lathe is supposed to run on a 1725rpm motor but when my motor is wired to 120 it will only turn 1480rpm when i get back from work i will be rewiring the motor to run on 240 so I can obtain the proper speeds. Can anyone tell me what speeds i have been using while th motor was spinning at 1480. I just wonder how much it was off. I had always set it up to run faster than what the book recommended because it just seemed slow and now I know why lol thanks to anyone who can answer that

 

[Kroll]

Changing voltage won't change the rpm's,but if you should change the motor pulley to a smaller diameter that will increase the rpm's.But since your only alittle off I would only drop down maybe one size----kroll

 

[chevydyl]

Haha kroll your wrong lol. As stated on the motor 120v 1480rpm 240v 1725rpm

 

[cdhknives]

The RPM change will be exactly proportional through the drive train (assuming no increase in belt slip from increased RPM.)

1480/1725==0.858

So take the published spindle speeds for 1725 RPM motor and multiply them by 0.858

 

[chevydyl]

thanks cdh that's exactly what I wanted to know

 

[Kroll]

I stand corrected,guess that applys to specific motors none which I own.But I plan to put this information in my memory banks just in case I need a motor like yours.If you get a chance and feel like it please post some pics of your motor.----kroll

 

[chevydyl]

will do man, yeah it seemed odd to me but that's what it says on the sticker

 

[shovel80]

Changing voltage won't change the rpm's,but if you should change the motor pulley to a smaller diameter that will increase the rpm's.But since your only alittle off I would only drop down maybe one size----kroll

Actually, if you decrease the Motor pulley size, it will decrease the final rpm's Not increase.

Terry)

 

[chevydyl]

and lol, if you decrease the jackshaft pulley smaller that will increase spindle speed but make the motor work much harder to produce that same RPM, as well as shorten the service life of the motor if worked hard.....just think of a 21 speed bike.... top gear is a small sprocket on the wheel with a large gear on the pedals but you cant pedal up hill with those gears lol you'll be worn out haha

 

[wa5cab]

There is a speed chart for the 10" and 12" machines in the Downloads. It is, of course, based on a nominal 1725 RPM motor.

However, I can't think offhand how one could build a single phase AC motor to run at 1480 RPM on a 60 cps supply. If you go to a 6-pole motor, it will run at around 1150 RPM. 1480 is in the ballpark (although a little on the high side) of what a 1725 RPM/60 cps motor would run at on 50 CPS.

Robert D.