Thread: Calling All Electrical Gurus

The answer is probably yes but I would need to have a look at the foot pedal. The action of depressing the pedal can probably be substituted with a potentiometer to give you variable speed.
I actually have a use for one of these motors so I will buy one and have a look. Might take a while till I get back to you though

Hi,
You could make a cam arrangement ( out of wood ) to hold the peddle in the required position with out having to do any electrical alterations.
Regards

A cam is a bit complex compared to a simple wedge and a couple of bits of wood.

My personal opinion is you will struggle with that motor for pen turning, I do not believe it will have enough power, sell the Lorch and purchase a mini woodturning lathe

Thanks for that Gents. Might end up being the wedge system. Firstly wouldnt a potentiometer still give you a variable speed though. I was looking for a fixed locked in speed. After I settled on what speed I might want/need. Maybe at the end of the day this wont be powerful enough. A few months ago I bought a cheap chinese $89 12 inch long lathe, mainly supposed to be just used for turning beads. I set it up with a pen mandrel and it works a treat, only has some small motor attached to it.

Its just that I come across this very old precision made Lorch German watchmakers lathe and googling about tells me they are worth big dollars. I have purchased a few bits and pieces to see if I can convert it for pen turning. At the end of the day if this sewing machine motor doesnt work, only costing 32 bucks, might have to rethink of a different motor.

Thanks again, Paul

Hi Paul, old sewing machines used to use a Rheostat in the foot switches. The downside of the Rheostat control is that as you reduce the speed, the power drops off too. Having said that, who knows what that motor is, and what type of speed control it is using.

Were I in your shoes I would simply set the motor up to run a full speed, and adjust with several pulley ratios.

It's a beautiful machine, and would be wonderful to be able to make use of it.

Hi all and Lance,

Thats an interesting reply. Just for interest sake this is the old Lorch German watchmakers lathe I per chance scored.

Paul

I think they're PWM electronic now. Cheaper than rheostat. A potentiometer means you could set the speed to whatever you want over it's range.
Wow, that's a wonderful little lathe. I've been keeping an eye out for one of those for a very long time.

Thanks NCArcher, I'm not really into electronics but I have used potentiometers for guitar building. But I doubt your talking about something similar. This lathe yes, very interesting indeeed. From my limited research (I only got this on Sunday), they were originally sold in a wooden suitcase type box, with all the accessories in their own little compartments in the box. There is one on ebay at present without a motor, for about $2,200. Others seem to just sell the parts for them and they are big dollars also

Looking at my pic the shaft going through the head end and the tail end is 8mm inside diameter. I dont think it was a type of morse taper at the head end. I've ordered a couple of parts so far which hopefully will give me a live centre for the tail end and a drill type chuck (opening to 10mm) at the head end. With some metal work to be done to make these fit. Fortunately the chap I got it from is a retired fitter and turner and has a huge metal work lathe.

Havent given much thought to a tool rest as yet.

Paul

Lorch lathes are a precision instrument, much more than you will ever need to turn pens, it is really wasted in such a application

Totally agree China, but I am way to old to do a course in watchmaking. And it was just sitting around doing nothing.

Paul

I would replace the pedal with a similar rated Resistance pot and mark around the outside with a dial and set the speed by hand.
You might be able to take the pot put of the pedal and use that.

If you wanted reproducible speeds you could set up a rotary switch with a resistor chain output with each position/resiatance corresponding to set speed.

A 10 position rotary could give you 10 speeds.

I did a similar thing on my DC with a 3 position rotary to output 40-50-60Hz, OR a pot full variable speed control.

For a lathe I thinks it's better to have full variable speed because sometimes you will get small resonant vibes at certain speeds and being able to change the speed by even a few RPM can move the speed out of these renounce points.

The earlier generation of electric sewing machines with external motors used carbon pile speed control, rather than rheostats or pots. The carbon pile is a series of carbon buttons arranged in a row, and being compressed when the pedal is depressed, varying the resistance of the series and hence the voltage applied to the motor and its speed. No way that a rheo or wirewound pot capable of directly handling 200W would fit in a foot pedal.

Later models with inbuilt motors used the same system for some time but have transitioned to SCR/TRIAC systems and ultimately to brushlesss motors under computer control. What would be involved in modifying the particular system would be determined by the style of control system employed.

That's definitely a brushed motor as it comes with a spare set of brushes