What's new
What's new

Lathe speed change while running (no clutch)

My new to me victor lathe does not have a clutch (I don't think any of them do).

But here's the thing, because I do not have 3 phase I have a rotary phase converter to make the needed 3 phase. However on higher speeds the lathe do not start reliably, meaning it stalls out then trips the breaker.

I know victor lathe manual and the face plate on the headstock itself says to not change speed while the lathe is running, but I wonder if anyone has a sure fire way of quickly switching gears while it runs in order to get me the higher speed without having to stop the machine and then restart it (mainly the problem is the motor having to overcome all the inertia of having to spin the lathe up to speed).

Has anyone tried this? Start the lathe up at a low speed then increment the speed up little by little until I get to the desired speed, kinda like shifting gears in a manual transmission car?

I have only successfully switched speed while running on the lower speeds... any attempt to do so at a higher speed and I can't do it fast enough and so I hear the horrible grinding noise.
Cars have syncros your lathe does not, you could try it if you want to spend more than the machine is worth on gears. Get the right size phase converter.
 
My victor is a 16” and has a 7.5 hp motor
When I first had it I used a 5hp rpc till my 10hp rpc was finished
It did what you described I could only start it in the first gear in high
I could start the next gear by spinning the chuck by hand as I turned it on
Going to a 50 amp 10hp rpc I’ve never stalled or tripped it
 
Pffft, you just have to rev match

Haha, I was thinking that exact same thing. Just pop the shifter into neutral, cut the motor and wait for the RPM to fall in, then pop 'er back into gear and hit the spindle start button! :D

Except he's already having trouble accelerating the spindle, so it probably wouldn't work even if he could manage it. (And yes, I'm joking...)
 
Haha, I was thinking that exact same thing. Just pop the shifter into neutral, cut the motor and wait for the RPM to fall in, then pop 'er back into gear and hit the spindle start button! :D

Except he's already having trouble accelerating the spindle, so it probably wouldn't work even if he could manage it. (And yes, I'm joking...)
I was thinking you'd have to wrap a rope around the spindle and yank and shift
 
Pffft, you just have to rev match
Sure Like my neighbors dumb ass kid on Dads Pristine FarmAll Super MTA. Tried speed shifting, about half the teeth were on the bottom of the gearbox when he was finished with that endeavor. Comprehensively destroyed, a huge job to fix, I know, I fixed it. Dad spent several thousand on used gears as no new ones were available.
 
Two problems here,
One, if it won't start in the higher ranges then it sure as hell will not pull any kind of load turning without tripping out in the higher ranges.
Two, On the Victor the gear train won't be for this world long changing the gear train from low to high in rotation.
 
Two problems here,
One, if it won't start in the higher ranges then it sure as hell will not pull any kind of load turning without tripping out in the higher ranges.
Two, On the Victor the gear train won't be for this world long changing the gear train from low to high in rotation.

On point one, I don't necessarily agree. The startup of an instant-on electric motor is the highest load it will ever see. The inrush current on startup is WAY higher than rated current. He may well have enough power to run the motor, but not enough to get it up to speed. I also think he should really find out what motor he is packing - all we have so far is "I think it's 5 HP" and a few other guys saying theirs were 7.5 HP - that's a significant difference in required power if he's mistaken.

I'm with you on point two though.
 
I have a Victor lathe made in 1976 with 5HP. Every electrical part other than the motor and on/off - forward/reverse switch has been removed. No more relays, contactors or anything else. All was replaced by a 10HP VFD. I just measured the start up current with a 172 lb three jaw chuck. With the lathe set to 1200 rpm it briefly pulls 36 amps and settles down to 7 amps with no load. The VFD never trips.

Never touch the speed levers with the lathe running. You will cause very expensive damage!
 
My Nardini is a notoriously tough starter. It also has a 2-speed motor. In the higher gears I used to start the motor on slow speed, let it come up to speed, then switch the motor to high. Later, I reconfigured my RPC and now no problem.
 
On point one, I don't necessarily agree. The startup of an instant-on electric motor is the highest load it will ever see. The inrush current on startup is WAY higher than rated current. He may well have enough power to run the motor, but not enough to get it up to speed. I also think he should really find out what motor he is packing - all we have so far is "I think it's 5 HP" and a few other guys saying theirs were 7.5 HP - that's a significant difference in required power if he's mistaken.

I'm with you on point two though.
In rush only occurs during the very first cycles of the motor ramping up to speed, If this is a single speed motor then inrush during motor ramping would be somewhat the same Irregardless of gear box settings, so if it will start and run the lathe in a low range there's absolutely no reason it won't do the same in a high gear range. If inrush was the problem it would be the problem ALL the time No only in the high gear range .Motor will pull near or Full load amp (FLA) after that. Yes we need far more information to correct his problem.
 
My victor is used in Taiwan, and it seems they are different than ones you guys use. In Taiwan we don't use a camlock nose for example, but A1-6.

I don't know what the motor is rated at because I'd need Superman to lift the lathe up, to look at the motor name plate. The motor is mounted in such a way that the name plate is not visible.

Do they make 10HP VFD that takes in single phase power? The most powerful VFD I have ever seen in Taiwan is for 5HP, everything above that is 3 phase input.
 
I am not an electrician at all but, I was under the impression you could use a standard VFD to convert single phase to 3 phase. Not sure how the electrical works in Taiwan but in the US I recall being told that you needed to oversize general use VFD by 50% to prevent burning it up with the increased amps coming in on 2 legs instead of 3.
So in your case you would need a 15 horse VFD to run a 10 horse motor.

To restate, I am not an electrician, use what I think I recall from my Motors, Controls, and Drives class I took at my local community college at your own risk.
 








 
Back
Top