Chester 10vs lathe 3 phase upgrade ….should i do it

This topic has 8 replies, 5 voices, and was last updated 30 December 2018 at 14:52 by Mark Webster.

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30 December 2018 at 13:17 #388267
Mark Webster
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@markwebster13123
ok I’m not the best at understanding all the electric stuff but I find at low RPM and when parting my lathe seems to lack torque ☹️. It’s fitted with a 1200 watt dc motor that is variable speed driven and not through gearing.

I would like a bigger lathe due to the frustration mentioned above but I just don’t have the space. So after reading in MEW about upgrading a similar Warco lathe got me thinking is this the answer to my problem of getting more torque at lower speed . So my questions are

1. Is this going to give a lot more torque if I change to a 1.5 hp 3 phase motor compared to the current 1200watt dc motor

2. I know this may seem strange but because space is limited for the upgrade and the 3 phase motors are so big. Would I be stupid to use a 1 hp 3 phase motor ( it would need a lot less alterations) to replace the 1200 watt dc motor.

3. I was looking at Tesla newton complete set up and control pendent but would anyone else have any recommendations

Remember my main aim here is for me to have greater/better torque at slower speeds eg 100 – 200 rpm. If you don’t think I’ll benefit much then please say

Many thanks folks
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30 December 2018 at 13:17 #26364
Mark Webster
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@markwebster13123
30 December 2018 at 13:34 #388271
JasonB
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@jasonb
Unless there is something wrong with the existing I would not bother, better to adjust your machining methods and let the lathe run at a speed which puts the motor in it's power band and take a slightly lighter cut.

The old school will tell you to put the lathe in slowest backgaer to turn a flywheel but with a carbide tool I happily spin 9-10" flywheels at 300rpm, same with parting 1.5" stock can be parted at 500-750rpm if steel, more if Ali.
30 December 2018 at 13:52 #388274
Bazyle
Participant
@bazyle
I thought DC motors were supposed to have more torque at low speeds, though you have to look out for high current and overheating I suppose.
It might be more interesting to look into ways of speed reduction. Various methods were devised for other lathes, eg Hobbymat and look at the Exe lathe. When the reason for low speed is for control during screwcutting look at making a mandrel handle.

edit I just googled 10vs images and got zero hits. Chester site has a DB10 is that it?

Edited By Bazyle on 30/12/2018 13:59:54
30 December 2018 at 13:58 #388277
John Haine
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@johnhaine32865
Does the lathe really not have any stepped pulleys?

A 1.5 hp motor (if from a reputable supplier) should be able to deliver 1.5 horsepower = ~1500 watts of mechanical power, whereas it is possible, even likely, that the 1200 W DC motor is rated at that electrical power, which means that the mechanical power will be perhaps 20% less. Indeed a 1 hp induction motor may give more mechanical power than your DC one. How this will translate to torque at the spindle depends on the drive ratio.

If you did decide to go the 3 phase/VFD route then with the right kind of VFD (flux vector control) (and suitable motor) you can maintain torque down to low speeds, but the motor current will increase and it will get hotter since the cooling fan will be less effective.
30 December 2018 at 14:10 #388282
Bazyle
Participant
@bazyle
I found this thread on a popular forum showing the works of a DB10. If your's is anything like this use the white space above the motor to mount a 2 step pulley and you can easily get a 3:1 reduction way cheaper than a new motor,
30 December 2018 at 14:14 #388283
John Haine
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@johnhaine32865
That's the way to do it!
30 December 2018 at 14:40 #388287
Les Jones 1
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@lesjones1
1200 watts is about the same as 1.5 HP so you are not gaining any extra power. Changing the drive ratio as suggested by Bazyle will give you more torque. An alternative way would be to use a two step reduction as on the Chester DB-10G lathe. This is a picture of my lathe before I fitted a three phase motor.

I had to make a new toothed belt pulley and three step pulley as the shaft on the three phase motor was a slightly larger diameter. Remember if you reduce the speed of a motor (DC or three phase.) you have also reduced the power. So if you run your 1200 watt motor a a quarter of it's rated speed it will only be capable of producing 300 watts of mechanical power. (About 0.4 HP.)

Les.
30 December 2018 at 14:52 #388289
Mark Webster
Participant
@markwebster13123
That’s interesting Les…..the additional pulley . Mine goes straight from the motor to the drive shaft. Speed range 50-1000 or 100-200 rpm. Might see if I can add another stepped pulley
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