Variable speed on a Hegner with a dimmer switch?!

[afshin]

Variable speed on a Hegner with a dimmer switch?!

Is there anyone who has tried to make a variable speed switch on a
scrollsaw with an induction motor?
I have a single speed Hegner with an induction motor, and I always wanted to turnt it to a variable speed scrollsaw with a dimmer, but I was told by the seller that the saw would be damaged if I used a dimmer, because of induction etc. So I did not try it.
So please help.

Regards

Afshin

[CanadianScroller]

This topic has come up several times. I wish I could just say wire up a dimmer with an outlet but it won't work properly.
Lights are a resistive load and the dimmer is designed for that purpose.
I have seen them used on motors with brushes, but the circuit needed to be modified or the electricity created by a coil of wire breaking through a magnetic field will flow back into the dimmer and fry it.
There are dimmers or speed controls used on fans, but I do not think they can withstand the current drawn by a saw.

My Delta saw also has a starting capacitor which throws another wrench into the works.

There are some speed controls for routers but then again routers have brushes.

Check out this Wikipedia Link it explains a lot.

I really wish there was a simple solution but I haven't found one yet.
The old time variable speed pully system was a wonderful invention that seems to have fallen by the wayside with the new VS motors now available on new equipment.

[William Young (SE BC)]

Hi Carl;
Interesting that you thought the variable speed pully system may have fallen by the wayside.
Actually , that sytem is still alive and well and is used on a lot of todays wood lathes like the head of mine pictured here. If we are referring to the same thing, they are now called a Reeves Drive.



They come in various speed selections but mostly 5 and 10. Mine has 10 speeds which are changed by just moving the lever back and forth while it is running which auomatically increses the size of one pully while decreasing the size of the other one and vice versa throughout its speed limits. It is much more foolproof than the newer electronic VS controllers and about the only part that needs replacing is the drive belt occasionally if I am working it hard on turning 14" bowls etc ..

Which leads me to my question. Does anyone here know of any scrollsaws that ever used this drive sytem ? ? I am just curious for my own information because I like to stay abreast of these type of things so I can be better informed about some of the older scroll saws of days gone by.
W.Y.

[Daryl185]

just out of curiosity why wouldn't one of those heavy duty model railroad train speed controls work for this, everyone has mentioned brushes, Trains have brushes and I have seen some really big loads pulled so they must pull quite a bit of amperage? HTH

[CanadianScroller]

Daryl the speed control on a train is a DC control and the universal motor in the scroll saw is AC.

W.Y. I was thinking more along the lines of a pully with a variable diameter that is controlled by compressing the two halves together.
The reason I bring this up is because that is how my cars Continually Variable Transmission works.


I do think the system on your lathe would work on this too though.
It would be nice to see a universall transmission that could be retrofitted to the tools

[Neal Moore]

Resistive speed controls are not a very good idea for induction motors. The motors are designed to run at the rated voltage on the nameplate. When you use a resistive speed control you are simply splitting the supply voltage between the speed control and the motor. An induction motor would soon heat up and burn out the windings. I suppose the best way to explain it is.....imagine what would happen to the compressor motor in your refrigerator if the supply voltage to your home was reduced by one half!!!

[William Young (SE BC)]

Carl;
Your picture shows exactly how the Reeves drive works. Both pullys have variable diameter . In the case of the reeves drive the lever opens or closes one pully and the other pulley adjust in size accordingly and thus controls the speed.
Way back when I had a couple snowmobiles they even had a similar drive system except that it was centrifucal force that opened the drive pully. BIG belt and big pulleys but same principal.
Thanks for your picture. It better explains what a Reeves Drive looks like .
If anyone knows what makes or models of scroll saws have ever used a system like this in the past I would like to hear about it to store it away in my knowledge bank.
W.Y.

[CanadianScroller]

I have a friend with an early 1940s model scrollsaw made by Delta Milwaukee
It is a basic design that was coppied by many. It has that drive.
here is a crummy picture from www.OWWM.com My friends machine is in MUCH better shape