Andrew

Sounds like a quick and dirty conversion from three phase to single phase by-passing all the internal factory control gear.

The pump control buttons are independent of the rest of the electrics so wiring direct to the motor power contactor gets it up'n running fast.

As I recall it the apron lever simply operates a motor forward / reverse switch inside the headstock. I have a feeling the 1600 was built with atwo speed motor so lots of wiring on the control side.

Hafta get hold of the manual and start tracing wires to see what you have left. Sounds like that some or all of the complicated gubbins may have been removed. If so probably best to track down the Colchester group on groups.io to find out how other folk have dealt with such defenestration.

I'd swop the single phase motor for a 6 pole 3 three phase driven by a decent VFD and devise a suitable control wiring set to duplicate the factory set up. Which I understand is decent to operate. But I'm confident with such electrics. Selling the 1.5 kW single phase motor should cover a replacement 6 pole three phase as decently husky single phase motors seem to be sought after.

Why 6 pole motor? Lower base speed means more torque in the low speed range as compared to slowing down a conventional 4 pole 1440 rpm motor. Don't need high torque at high speeds so losses when running fast don't matter so much. 8 pole is theoretically even better but spendy. Or you could adjust pulley sizes on the motor to pull the drive input speed down but then the motor pulley will be rather small.

Best to take the trouble to sort it before putting into service or you will make do and curse for fart too long before accepting the inevitable.

Clive

It maybe might be a good idea to look at lathesdotco site for info.

You would have found the following:

“with a two-speed motor and marked Model 1600”

That quite possibly means your lathe does not have an original specification motor/?

Edited By not done it yet on 20/12/2021 10:04:23

Single phase motors can be dual speed. I have no idea whether it may have been single or three phase when new. If it was single phase, it has not been ‘converted’ but just ‘exchanged’ for a cheap alternative or incorrect replacement.

Difficult to say Andrew because the motor is unknown. Two things limit the amount of metal that can be removed:

• The power output of the motor. (Assuming it's suitably geared to put the required RPM/torque on the spindle. The latter is rarely a problem: just select the right gears and drive belts.)
• The rigidity of the machine. Too much power bends the structure causing inaccuracy and poor finish, and greatly increases the chance of serious damage in a head-crash or other accident.

If your single-phase motor is of similar power output to the original 3-phase, the lathe will remove roughly the same amount of metal: rule of thumb, about 1 cubic inch per horsepower per minute.

But amateur work is typically much slower than that. We aren't working in a sweat-shop mass-producing junk as quickly as possible: our goal is usually small numbers of parts that fit together. More skill, less rush.

Although my Chinese WM280 with a 1.5kW motor cheerfully takes a millimetre deep cut in mild steel, I rarely push it that hard, preferring to rough out with 0.6mm off the diameter per pass, and reducing to about 0.1mm or less to hit the target dimension.

Your Colchester is more heavily built than my lathe, but I believe they came with smaller motors – perhaps 1kW? The Colchester's design is after reliable accuracy rather than brute metal hacking. In practice, I'd expect the Colchester to cut at similar rates to my machine. The Colchester can probably cope with it's motor at full power, whereas the Chinese lathe is likely to flex when pushed to the limit. But it's probably unnecessary to run either flat out! I'd say anything between 300W and 2500W is sensible, and 1kW is fine for most purposes.

I suggest the best way to find out what your lathe can do is to try it. Set RPM for the diameter of a test mild-steel rod and take a succession of increasingly deep cuts at high feed-rate. Look and listen for signs of distress, especially the motor getting hot. I'd cut dry with Carbine: flood cool if HSS is used.

If the lathe was mine, I'd seriously consider going back to the original 3-phase configuration and driving it with a VFD. The single-phase motor was probably fitted before affordable VFDs existed, and they're OK rather than ideal.

Dave

The MK1 1600 used a two speed motor to get the two speed ranges and the Mk1 800 just had a single speed motor hence the max of 800

The Mk11 1600 and 2000 used a single speed motor with twin pullies to get the two speed ranges. See third image down this page

What bantam do you have, if a Mk11 then your single speed motor may do.

Cut in aluminium will depend somewhat on the diameter, you should be able to take a 3mm deep cut off 25mm stock eg 6mm off dia in one pass but may not be able to do that on a 200mm dia piece, Feed rate will also come into it as you can go deeper if the depth of cut is less. My similar sized WM280 can cut the full insert width if I wanted but would not want to do that regularly.

That is a two speed motor one so back to square 1