Lathe speed change while running (no clutch)

[taiwanluthiers]

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.

 

[Philabuster]

The problem is your phase converter is too small for the lathe. Get a bigger phase converter. Changing gears when the spindle is turning will only harm your lathe.

 

[Tyrone Shoelaces]

One or two kids used to manage it all the time when I worked at the high school !

Regards Tyrone.

 

[eKretz]

The problem is your phase converter is too small for the lathe. Get a bigger phase converter. Changing gears when the spindle is turning will only harm your lathe.

Could also get a soft start module. Or just switch to a VFD.

One or two kids used to manage it all the time when I worked at the high school !

Regards Tyrone.

I bet that sounded nice...

 

[DrHook]

The new Victor I have at work has a switch which automatically triggers a "step up" on the motor when you start it in a higher gear. (it gets the spindle turning, then "shifts" up) Maybe your switch isn't working correctly.

 

[Joe Henderson]

I wouldn't do it. It sounds like your RPC is underpowered for your lathe's main motor.

 

[Bill D]

VFD. with slow start programed in. How may horsepower? Which breaker is tripping on the wall or inside the machine?
Bill D

 

[taiwanluthiers]

Problem is Victor lathes have a bunch of relays and contactors that controls every aspect of the machine, and using a VFD is too complicated. So I wouldn't have a clue how to wire it so that a VFD can use it safely. The breaker is tripping in the wall. I think the motor is 5HP but I don't know...

 

[Nmbmxer]

Buy another 3phase motor then start your phase converter, start the extra motor, use the lathe. The extra pony motor's HP can be added to the phase converters HP and will increase the total HP of your 3ph system. If you have another 3ph machine you can start it and then try the lathe, for example run your Bridgeport in neutral and you'd get an extra 2hp of 3ph for your lathe.

 

[sfriedberg]

If you try to speed shift a lathe in the price class of a Victor, you are just going to cause nasty grinding noises (at best) and serious mechanical damage if you persist. Get a more powerful phase convertor.

 

[taiwanluthiers]

I ran 2 5HP motors in the RPC, tried a third, but the problem is even with the 2 extra motors, the highest speed would not start at all...

 

[DDoug]

I ran 2 5HP motors in the RPC, tried a third, but the problem is even with the 2 extra motors, the highest speed would not start at all...

If your incoming power and your RPC "System" won't even start it, soft starting won't help.
It's clear you don't have enough electrical service to keep it turning no matter how you get it up to speed.

 

[eKretz]

If your incoming power and your RPC "System" won't even start it, soft starting won't help.
It's clear you don't have enough electrical service to keep it turning no matter how you get it up to speed.

Not necessarily so. Instant-on startup draws way more than rated running current. A soft start can drop that down massively and spread the current draw to a lower level over a longer period of time. Might help, might not; will depend on exactly what he's got on the supply side and what exactly he's trying to start.

 

[taiwanluthiers]

Not necessarily so. Instant-on startup draws way more than rated running current. A soft start can drop that down massively and spread the current draw to a lower level over a longer period of time. Might help, might not; will depend on exactly what he's got on the supply side and what exactly he's trying to start.

So how do you soft start on a RPC?

 

[eKretz]

So how do you soft start on a RPC?

You buy... a soft start module. But look for secondhand, not cheap new. Not sure if certain ones play better with RPC either.

I'd still VFD it. There's really not much to it on a lathe. Mine was similar to yours, lots of switches and electronics. I ditched all that and added a VFD. Run the VFD straight to the motor. Run the important switches to the VFD. Et voila.

 

[DDoug]

Not necessarily so. Instant-on startup draws way more than rated running current. A soft start can drop that down massively and spread the current draw to a lower level over a longer period of time. Might help, might not; will depend on exactly what he's got on the supply side and what exactly he's trying to start.

Based on the OP's text "... ran 2 5HP motors in the RPC, tried a third, but the problem is even with the 2 extra motors, the highest speed would not start at all."

"At All" I take it as "not even get partially spun up before tripping out".

 

[taiwanluthiers]

Based on the OP's text "... ran 2 5HP motors in the RPC, tried a third, but the problem is even with the 2 extra motors, the highest speed would not start at all."

"At All" I take it as "not even get partially spun up before tripping out".

It would spin up but it seems the amp draw is too high and it cuts out before it's able to fully spin up. At all other speed it's fine but 1800 rpm would only spin up halfway before the breaker trips.

 

[Philabuster]

It would spin up but it seems the amp draw is too high and it cuts out before it's able to fully spin up. At all other speed it's fine but 1800 rpm would only spin up halfway before the breaker trips.

Buy a soft starter and wire it between the incoming power and the lathe's motor. The soft starter is not wired to the RPC. A soft starter will definitely reduce the inrush current when you fire up the lathe.

I put a soft starter on my 15hp turret lathe and also on my 3 phase 7.5hp air compressor. The soft starter allows me to fire up the turret lathe and not brown out my CNC lathe.

I bought the soft starters used on ebay for cheap. Not sure what you have available in Taiwan.

 

[beckerkumm]

Do we know the lathe motor size, RPC size, and input amperage to the rpc? We need all three to make a recommendation. Even if the rpc is properly sized, too little input amperage to it will cause the issues. Rule that out before spending for a soft start or vfd. Dave

 

[taiwanluthiers]

Input amp is 40 amps...