Sieg lathe motor conversion

[Nikhil Bhale]

Hello,

I have a Sieg C4B lathe. It is similar in size to Sieg SC4 lathe but it has a AC reversible motor and belt and pulley system for speed control.
For slow speeds/ back gear the lathe uses a toothed belt of 1.5mm pitch. This belt is "delicate" and gets damaged easily and is very difficult to source locally.
I am thinking of changing the drive to a DC motor drive.
I have seen people on YouTube and elsewhere using a treadmill motor for this conversion.

After searching on the internet I have two motor options.
1. Treadmill motor DC 180V, 1-1.5kW

2. Ebike motor DC 48V, 1kW

I want to ask which motor will be more suitable?
Both motors cost nearly the same and the controllers for the motor are also in the same price range.
Do we need a separate cooling arrangement for the motors as they may run at less than optimal speed for a long time?
The low voltage ebike motor will draw more current than the treadmill motor. Will this affect anything?

I will add that my "workshop" is not air conditioned and the temperature at my place goes to 47-48C during summer. I generally avoid working in this high temperature but I try to work if temperature is 40-42C.

Regards
Nikhil

 

[ddmckee54]

Most of the industrial electronics that I have seen is rated at 40°C. Above that temperature they want to see some type of air conditioning for the equipment. It doesn't mean it won't work above that temperature, but it does mean that you are shortening the useful life of the equipment. Where I work in Iowa, we've got an "845"Hp motor on a large air compressor. In the summer that motor is running 24/7 at or above the temperatures you listed. We are getting less than 20,000 hours out of the bearings on that motor before they start to fail - a fraction of the life we should be getting. Those failures are due to the way the manufacturer treated that poor motor during the design - just to get the desired performance at a lower rated Hp. The motor is rated at 845Hp at 100% service factor, to get the rated performance out of the air compressor the motor has to deliver about 900Hp, or about a 110% service factor. You do that to a motor and sooner or later something is going to give.

Forced air cooling for the motor, you betcha! The original Sieg motor was probably rated at 600-700W if you're lucky. Even at 1KW the new motor will see a greatly reduced load than it was designed for, but extra cooling won't hurt it - especially if you plan on running the motor at a greatly reduced speed. We've got a number of 600Hp extruder motors that are designed to run 24/7 from 0-1750 RPM at 100% torque throughout the range, they've also got 5Hp cooling fans on them. Those extruder motors have been in place for about 20 years and haven't failed yet. A cooling fan on the electronics wouldn't be a bad idea either. I'd use a computer "muffin" style blower on the electronics, and a squirrel cage blower with a shroud for the lathe motor.

Given my 'druthers, I'd go with the Ebike motor, it's smaller and they're designed to live in a nastier environment than the treadmill motor is designed for. But obviously, the choice is yours.

Don

 

[ninefinger]

The motor is only half the battle. You mention the controllers are roughly the same price, but I think you may find out that they can be the differentiator between the motors. I'm not familiar with either the treadmill controller or the the e-bike but speed/load regulation is a concern - if you set the lathe for a speed and then apply a cutting load, how does it handle that? Do some research on that front before deciding. There have been some really bad motor controllers that couldn't handle that situation (hopefully all in the past).
Lastly - does the "controller" make the DC voltage (more likely for treadmill) or just regulate it (likely in the e-bike case - think battery supply) - it may be that's another item to get (DC power supply) changing the cost equation.

 

[Nikhil Bhale]

Thanks Don and ninefinger for your replies.

I am watching a lot of youtube videos and browsing the internet to get information about the conversion.
I came upon this site DazeCars, Upgrading shop tools for variable speed which uses a cheaper option for motor control.
But this needs some electronics knowledge which I lack. There is a guy in my neighborhood who is good in electronics, I will get his advice if this is doable.

Nikhil

 

[blanik]

Hello,

I have a Sieg C4B lathe. It is similar in size to Sieg SC4 lathe but it has a AC reversible motor and belt and pulley system for speed control.
For slow speeds/ back gear the lathe uses a toothed belt of 1.5mm pitch. This belt is "delicate" and gets damaged easily and is very difficult to source locally.
I am thinking of changing the drive to a DC motor drive.
I have seen people on YouTube and elsewhere using a treadmill motor for this conversion.

After searching on the internet I have two motor options.
1. Treadmill motor DC 180V, 1-1.5kW

View attachment 145300

2. Ebike motor DC 48V, 1kW
View attachment 145301

I want to ask which motor will be more suitable?
Both motors cost nearly the same and the controllers for the motor are also in the same price range.
Do we need a separate cooling arrangement for the motors as they may run at less than optimal speed for a long time?
The low voltage ebike motor will draw more current than the treadmill motor. Will this affect anything?

I will add that my "workshop" is not air conditioned and the temperature at my place goes to 47-48C during summer. I generally avoid working in this high temperature but I try to work if temperature is 40-42C.

Regards
Nikhil

Nikhil,

Have you considered obtaining the necessary parts from Sieg (or one of their dealers) in order to convert your C4 Lathe to an SC4. I have owned an SC4 for about six years, and have found the brushless DC motor and controller to be very good.

Positive notes regarding the SC4 include; 1) The motor controller is designed to handle changing loads, and easily maintains a constant speed when starting cuts, and during interrupted cuts. 2) The motor controller has a very good overload cutout circuit that cuts the motor very quickly, preventing motor damage. 3) The motor controller has motor brake circuitry, which stops the spindle near instantly when you hit the stop button.

There was only one problem with the factory standard SC4, and that is that at the minimum spindle speed (ex Factory) for the SC4 is approx 100 RPM. I found that at 100 RPM the lathe lacked torque as the motor RPM was too slow. At spindle RPMs greater than approximately 150 RPM, there was no lack of torque. The problem was first observed when single point threading at 100 to 120 RPM. It was too easy to stall the motor. Threading at 150 RPM, where the lathe does not stall, was a bit too fast for my liking's. The lack of torque at low speeds was also very noticeable when turning diameters at the lathes maximum limit. For turning large diameters, I changed from HSS cutters, to Carbide cutters, and turned the spindle speed up a bit.

I cured the lack of low spindle speed torque by modifying my lathe to add a 'back gear'. That was simply achieved by adding an extra toothed belt pulley on the motor shaft, and larger second toothed belt on the driven shaft. Changing from high gear to low gear is a simple and quick process of sliding the toothed belt from one set of toothed belts to the other.

I hope that information is useful.

Regards,

RoyG

 

[Nikhil Bhale]

RoyG thanks for the suggestion.
I will check with the firm from whom I bought the machine.
One of the reason I wanted to do this conversion is that I want to try out single point threading.
My lathe lowest speed is also in the same 150-200 range and I am afraid to do threading at this speed.

Nikhil

 

[RM-MN]

RoyG thanks for the suggestion.
I will check with the firm from whom I bought the machine.
One of the reason I wanted to do this conversion is that I want to try out single point threading.
My lathe lowest speed is also in the same 150-200 range and I am afraid to do threading at this speed.

Nikhil

A work around for threading at that speed is to uses an internal threading bar on the backside of the material and run the lathe in reverse. This will allow you to start near the headstock and thread away from it for right hand threads.

Another workaround is to make a crank that wedges in the spindle bore (to the rear) and turn the lathe by hand as you do the threading. You control the speed and can turn the lathe quite slowly.

 

[Steamchick]

I have a similar low speed problem. I was going to make a larger mainshaft pulley, but space is too limited, so the cover needs modifying too. But I use a spanner on the jaw of the chuck to crank the shaft 1/3rd rotation at a time... I like the idea of fitting a handle in the back-end of the mainshaft! May even see if I can arrange a different motor drive there as well...? - with a simple disconnect for when I don't need it?
K2

 

[Justin.P]

While not the cheapest option but probably not priced terrible by the time you chase everything down, www.servomotorkit.com has complete motor kits or just parts to do the conversion with the ubiquitous sewing machine motors that are available online.
I bought my motor and controller off eBay, but I needed timing belt pulleys, my lathe was tore apart so I couldn't make any. I discovered the website and ordered pullies from him. I'm still in the middle of my project so I can't comment on the motor. I decided to beef up the bed under the headstock on mine, instead of having the motor right there. Which has added a fair amount of complication over just a motor and controller swap.

 

[Harglo]

Consider a 3 phase motor an a variable frequency drive.
Harvey

 

[packrat]

Steamchick.. Steve Jordan put one {crank} on his Myford lathe