Lathe power

[GraemeVW]

What is the lathe?

The gears or feedscrew will be the weakest link.

You won't break pulleys, belts or spindles, but you will damage gears and feed screws if you start taking cuts that the motor can handle but the components in between cannot.

I'd say you'd be safe with 1.5hp.

Three phase for sure, bin the single phase. That is a revelation in itself going from single to three.

It's one of these.

Apart from the benefits the vfd brings, own it just the smoothness that's the main advantage of 3ph?

 

[GraemeVW]

No it won't.
Amps drawn (provided the correct voltage is applied) is proportionate to the load applied.

That's what I'd read elswhere

 

[Brad93]

It's one of these.
View attachment 403267

Apart from the benefits the vfd brings, own it just the smoothness that's the main advantage of 3ph?

Smooth, spins up quickly, forwards and reverse

 

[Jelly_Sheffield]

it will cosume whatever amperage the rating of the motor is as long as its turned on. used or not

The ammeter on my workshop power supply says different (and would be useless to me otherwise).

The consumption of a modern, high efficiency, three phase motor at idle is generally around 8-10% of the consumption at rated load (which is what's on the plate as the "Full Load Amps").

Older motors can be as high as 50% of the rated power consumption (with smaller motors being closer to the top end of that range).

Thus the energy consumption at standby of a 2hp modern motor built to the most recent efficiency standards (around 0.15-0.19kW) can end up being lower than that of an older ½hp motor (as high as 0.23kW).



Ultimately all motors consume less power at idle than when under load, and will only consume as much power as the load demands, because electrical power demand is a function of the slip between the magnetic fields in the rotor and stator, which in turn is a function of how much the mechanical load is acting to slow the rotor.

The efficiency at idle is highly variable however, and can only really be assessed for a specific motor and power transmission combination.

 

[Jelly_Sheffield]

What TOS is that? If you're talking about an SN32 it doesn't weigh anywhere near 1.9ton. Unless it's a very old model?

S32 from TOS Zebrak, 1970's production, 1000mm bed.
It's a very different machine to the SN32 despite the extremely similar name.

That weight is based on me taking the van over a public weighbridge before and after loading the lathe, and the ticket said it was to ±25kg.

(I really didn't have a lot of additional load capacity to play with on the dropside I was using, hence the weighbridge visit before driving 350miles on the motorway)

My downloaded English version of the manual says it should be 1.7t, but the original Czech manual I got with it gives 1825kg, so it appears to have got a bit lighter between the 70's when the original manual was written and the late 80's when the English one was.

The additional 75kg I got on the weighbridge over and above the listed weight could easily be the chuck, accessories and coolant tank.

 

[skotl]

...Three phase for sure, bin the single phase. That is a revelation in itself going from single to three.

Concur. Controllability, infintely variable speed (within obvious limits), soft start and stop, ability to operate in reverse (which some but not all single phase motors can do - very handy for thread cutting)

 

[GraemeVW]

Concur. Controllability, infintely variable speed (within obvious limits), soft start and stop, ability to operate in reverse (which some but not all single phase motors can do - very handy for thread cutting)

I know all those benefits, but I really need to run the lathe a while first before investing in what is still an unknown machine.

 

[Jelly_Sheffield]

I know all those benefits, but I really need to run the lathe a while first before investing in what is still an unknown machine.

That's a sensible approach, although if the existing motor works, are you as well using that until you've done enough testing to get a feel for whether to invest more in it?

You'll be able to pinpoint issues which are down to the motor being dodgy fairly easily (stalling out even in light cuts and weird patterns in the surface finish without obvious vibration during the cut being the two most likely ones).

 

[skotl]

I know all those benefits, but I really need to run the lathe a while first before investing in what is still an unknown machine.

Fair point

 

[God mode restorations]

Stick something like this on it. That sort it

 

[GraemeVW]

Stick something like this on it. That sort it

View attachment 403291

I could.
Hole in the wall, build a motor shed extension in next doors garden.
Might be easiest to run the belt horizontal to a layshaft where the old motor was.

 

[GraemeVW]

That's a sensible approach, although if the existing motor works, are you as well using that until you've done enough testing to get a feel for whether to invest more in it?

You'll be able to pinpoint issues which are down to the motor being dodgy fairly easily (stalling out even in light cuts and weird patterns in the surface finish without obvious vibration during the cut being the two most likely ones).

The only reason I'm already looking out for a motor is the one that's with it is heavy and doesn't quite fit through the opening due to the huge cast iron switch housing that's built I to it.
I'd rather pick up a spare 1ph motor for cheap than wrestle that thing back in!

Once it's all up and running and everything is good, I'll revisit the motor situation, along with dro's

 

[God mode restorations]

The only reason I'm already looking out for a motor is the one that's with it is heavy and doesn't quite fit through the opening due to the huge cast iron switch housing that's built I to it.
I'd rather pick up a spare 1ph motor for cheap than wrestle that thing back in!

Once it's all up and running and everything is good, I'll revisit the motor situation, along with dro's

Yes the original set ups with motors can be a nightmare due the the weight and configuration of where it sits. A modern replacement is good. And a little extra on the hp is a bonus provided you don't go to excessive. With to much hp the first thing to go bang will be gears and screws.

 

[GraemeVW]

Yes the original set ups with motors can be a nightmare due the the weight and configuration of where it sits. A modern replacement is good. And a little extra on the hp is a bonus provided you don't go to excessive. With to much hp the first thing to go bang will be gears and screws.

This is the motor That's in it.
Can't believe how heavy it is for a 1/2hp motor.
It's fire proof, it's not original. The huge cast iron switch housing makes it very awkward to get in or out, there are no covers on the switch or terminal housings, and it grumbles a bit.

It will do to get it up and running if i have to.

 

[God mode restorations]

This is the motor That's in it.
Can't believe how heavy it is for a 1/2hp motor.
It's fire proof, it's not original. The huge cast iron switch housing makes it very awkward to get in or out, there are no covers on the switch or terminal housings, and it grumbles a bit.View attachment 403305
View attachment 403307
View attachment 403306

It will do to get it up and running if i have to.

I be inclined to restore the original but that's just me. They did pack em in back then in the day and monster weight

 

[GraemeVW]

I be inclined to restore the original but that's just me. They did pack em in back then in the day and monster weight

It's not the original. The original motor and switch gear was all ripped out long ago. This is just some random scrap motor someone has fitted.

 

[Brad93]

S32 from TOS Zebrak, 1970's production, 1000mm bed.
It's a very different machine to the SN32 despite the extremely similar name.

That weight is based on me taking the van over a public weighbridge before and after loading the lathe, and the ticket said it was to ±25kg.

(I really didn't have a lot of additional load capacity to play with on the dropside I was using, hence the weighbridge visit before driving 350miles on the motorway)

My downloaded English version of the manual says it should be 1.7t, but the original Czech manual I got with it gives 1825kg, so it appears to have got a bit lighter between the 70's when the original manual was written and the late 80's when the English one was.

The additional 75kg I got on the weighbridge over and above the listed weight could easily be the chuck, accessories and coolant tank.

Ah i see. Say my SN40 is 1700kg (also 1000mm between centres)

 

[Brad93]

I'm half tempted to swap out the 1.5 hp on my lathe for a 3hp if you're interested.

It is three phase though

 

[GraemeVW]

I'm half tempted to swap out the 1.5 hp on my lathe for a 3hp if you're interested.

It is three phase though

I would be, depending on price and shipping.

I believe your in my old area, Essex?
I escaped and moved to Derbyshire

 

[pressbrake1]

No it won't.
Amps drawn (provided the correct voltage is applied) is proportionate to the load applied.

And that’s why some machines have a amp meter , to monitor cutting load and tip condition and on grinders to see spark out load