[Ken_Shea]

Any one familliar with how this Electronic variable speed works ?

Not looking for repair information, just electronic/mechanical function information.


Thanks
Ken

[snaggletto]

Hey,
I've got a Hardinge HLV toolroom lathe, I believe it's a similar setup.

Basically you have a countershaft with 2 spring loaded (variable) pulleys which is attatched to a leadscrew driven my a gearmotor. One spring pulley is coupled via a belt to the spindle(with fixed pulley), the other spring pulley is coupled to the motor(fixed pulley) via a belt.

When you turn the speed switch, the gearmotor raises or lowers the countershaft relative to the motor or spindle. As the countershaft moves the belts slacken or tighten up. These spring pulleys are forced open(as belt is of fixed length) or spring closed to take up the slack. This effectively changes the gear ratio from the motor to the spindle, while maintaining belt tension. The variable speed Bridgeport mill heads work similarly, but without the countershaft. The motor pulley and spindle pulley are both spring loaded, but the principle is the same as in the Hardinge. The front pulley is opened/closed by the speed dial, this tigthens or relaxes the belt and the motor pulley takes up the slack.


|| spindle pulley fixed
|
| belt
|
><----->< counter shaft,spring loaded pulleys, raises up/down
|
| belt
|
|| motor pulley fixed

My picture didn't turn out so well. The motor pulley/belt should be lined up with the right most spring pulley on the counter shaft to look proper. You get the idea though.

[Ken_Shea]

Thank you, that helped a lot, it does appear to be the same set up or at least very similar. Actually your picture showed up formatted fine in the email notification.

I was kinda shocked at the amount of electrical components for such a simple lathe and no PCB's

.
Ken

[ViperTX]

...like adjustable sheaves??

[snaggletto]

Yes, I guess sheaves is the more appropriate term. They are conical in shape and spring loaded to force them together. The belt is wide and flat, and when tightened, presses the sheaves apart thus riding on a smaller diameter. When the belt is loosened, the sheaves spring back together, forcing the belt out to ride on a larger diameter, changing the gear ratio. The loosening and tightening comes from the movable countershaft.