Geo Stevens Variac speed control

[Johnnie5]

Hello, I'm new to this forum and I appreciate all the great discussions! I have a question that I hope someone can help with. I am setting up a Geo Stevens 314 AM and the lowest speed I can dial in is 2600rpm at the spindle. I want to get it down to about 900 for nice even coils. Question is, can I use a router speed controller in front of the Variac to get the speed I want without damaging the motor? I can't find any info on this particular setup.
Thanks

[Jazz P Bass]

Contact the manufacturer.

Contact Us
George Stevens Mfg, Inc.
1886 E. Fabyan Parkway
Batavia, IL 60510 U.S.A.
Phone: 630-406-9550
Fax:630-406-9552
info@geostevens.com

[J M Fahey]

A "chopper" type "router speed controller" is a poor choice for a regulator and doubly so ahead of a Variac.

Don't understand how your Variac can't get down to *zero* speed if needed, considering they can be set down to zero volts.

That said, many electric motors do not like very low voltages; they stutter, work irregularly, etc. , all because they lose torque big way.

Maybe, if you often or always need such low speeds, you should consider some change of gears, for mechanical speed (range) reduction.

That way you get the low speed but keep or increase torque.

Please describe your setup and problems in greater detail.

[Jazz P Bass]

The 314-AM product literature states: 'custom built 1/4 HP variable speed motor with speed control'.
So that may indicate a DC motor.
If so, forget the 'router speed control'.

IF it is an electronic speed control, it may be possible to modify the control to run slower.
Possibly as simple as a resistor change.

Stevens 314-AM.pdf

[Joe Gwinn]

It sounds like the motor is universal wound, like a sewing machine motor only larger. The test is if the motor has a pair of carbon brushes.

One can control such motors with a variac, but low-speed behavior is better if there is a full-wave rectifier bridge between variac (AC side) and motor (plus-minus side of the bridge). It won't matter which way the plus and minus leads are connected to the motor - it will always turn the same direction (unless one rewires the motor).

The test of universal versus reversible DC is the number of wires. If two, it's universal. If four, it's series-wound or parallel-wound DC. Universal is a kind of series-wound DC motor. The manual for the winder should contain enough information to tell the story. The motor nameplate may also say, or at least imply. A photo of the nameplate would be helpful.

In 1970, thyristor-based solid state dimmers were available, and I bet that the electronic control was just that. The soft start will have been built into the thyristor control circuitry. A full-wave rectifier may also have been included, mainly to allow use of a single SCR switch (they were expensive then) to achieve full-wave control.

[Johnnie5]

Thanks for the info, guys. The motor has two brushes and I he Variac is labelled with numbers from 0 to 100 , so I assumed that I could dial in 0 volts as well. I am aware that motors function incorrectly (stutter, inconsistent speed, etc) at too low a voltage and the manual says the motor should be running at the highest possible speed for the job for cooling.

I could play with the electronics inside, but I'm scared to burn up the motor, a rewind is expensive. Swapping the motor wouldn't be too much of a hassle I guess.

I'm not familiar with Variac circuits, I wonder if this one is faulty. The machine is about 40 years old. I have a spare machine with another Variac I could swap if this one is indeed faulty, but the other machine is just as old.

I have tried gear changes and I have the biggest/smallest pulleys in the correct places. The machine has no extra room for an even larger pulley on the spindle.

I'm really inclined to believe the Variac isn't varying as much as it should.

Anyone have intimate knowledge of how a Variac works? I've read the wiki on it and some random other info from the webs.

[David King]

Welcome Johnnie5,

Say hi to Carey for me.

I had one of these for a few months and I don't think I ever even plugged it in. I wouldn't worry about burning the motor out, these machines were way over built and you won't be winding 24h a day with it. It sounds like you could clean up the brushes and commutator as well as the bearings and smooth out the low speed operation. If it's still too fast then I'd get or make some different pulleys to get the ratio closer to what you need. You could upgrade the belt to a toothed belt while you are at it and find a ton of small, inexpensive toothed pulleys on ebay etc.

[Johnnie5]

Thanks David, will do. This machine has so much character. It's a great blend of automation and human touch. BTW, I have some documentation such as tpl charts and parts numbers if any other Geo Stevens users need them.

[CheopisIV]

I've tried to contact the folks at Geo Stevens a couple times but no response to either email. Hope you have better luck. These really are cool little machines!

[Johnnie5]

I contacted them via email asking about the tail stock for my winder. Someone wrote me back but said they never made a tail stock for my model. There is a picture and part number for the tail stock on the first page of my manual. Maybe it's just too old of a model for them to care much about it.

[David King]

It would be easy enough to fabricate something along those lines if you felt it was necessary.

[Jazz P Bass]

What is this 'Variac' you keep speaking of?

Is it a part of the winder or is it an external device?

[Joe Gwinn]

Thanks for the info, guys. The motor has two brushes and the Variac is labelled with numbers from 0 to 100 , so I assumed that I could dial in 0 volts as well. I am aware that motors function incorrectly (stutter, inconsistent speed, etc) at too low a voltage and the manual says the motor should be running at the highest possible speed for the job for cooling.

I'm not familiar with Variac circuits, I wonder if this one is faulty. The machine is about 40 years old. I have a spare machine with another Variac I could swap if this one is indeed faulty, but the other machine is just as old.

I'm really inclined to believe the Variac isn't varying as much as it should.

The 0 to 100 is notional - variacs are not precision instruments, but they are not fragile either I'd put a voltmeter across the output and see how the voltage varies as you turn the handle. Zero on the scale may not be zero volts.

I have tried gear changes and I have the biggest/smallest pulleys in the correct places. The machine has no extra room for an even larger pulley on the spindle.

Anyone have intimate knowledge of how a Variac works? I've read the wiki on it and some random other info from the webs.

Variacs are very simple. They are a variable-ratio transformer. When you let go of the knob, they behave exactly as an autotransformer (primary and secondary are combined) of whatever ratio the knob position indicates.

I could play with the electronics inside, but I'm scared to burn up the motor, a rewind is expensive. Swapping the motor wouldn't be too much of a hassle I guess.

More likely is damage to the electronics. Does the control module have a nameplate? What does the nameplate say? Does it mention a patent? Who made it?


Proceed step by step. I'd start with the variac. Does it control the brightness of a 100-watt lamp in a reasonable manner? Does the voltmeter bear this out? If not, repair the variac.

How many wires come out of the motor? What does the motor nameplate say? A photo would be nice - I may be able to decipher it.


By the way, the Geo Stevens company still exists, so a manual may be available (perhaps for purchase - buy it anyway). But it's best to phone them - they don't seem to do email.

[Johnnie5]

Thanks man, I'll see if I can find any indenifying marks on the components. The control module itself has no ID, but the parts inside are easy enough to decipher. I'll open it up and take some pics in the next few days, I need to check the brushes and commutator anyways.