Old Singer Sewing Machine - No Variable Speed

[[email protected]]

Anyone know how these old singer foot pedals work? There's not much
to this thing, but I can't for the life of me figure out how it's
supposed to work!

The one I have contains a long ceramic tube filled with a stack or
maybe 100 graphite disks. One end connects to the sewing machine
motor (I assume), and at the other end there's a contact that's
brought closer to and eventually touching the contact on the end of
the tube as the foot pedal is depressed.

The foot pedal was dropped and I'm trying to repair it, but so far I
can't get any variable speed out of it - I get either off (when the
contact isn't touching the end of the graphite-disc-tube) or ON-HIGH
when the contact touches the end of the graphite-disc-tube.

Sorry for the miserable description - it's been about a month since I
had the thing apart - just figured I'd post here to see if anyone had
any suggestions.

thanks!

-Pete

 

[David Nebenzahl]

Anyone know how these old singer foot pedals work? There's not much
to this thing, but I can't for the life of me figure out how it's
supposed to work!

The one I have contains a long ceramic tube filled with a stack or
maybe 100 graphite disks. One end connects to the sewing machine
motor (I assume), and at the other end there's a contact that's
brought closer to and eventually touching the contact on the end of
the tube as the foot pedal is depressed.

The foot pedal was dropped and I'm trying to repair it, but so far I
can't get any variable speed out of it - I get either off (when the
contact isn't touching the end of the graphite-disc-tube) or ON-HIGH
when the contact touches the end of the graphite-disc-tube.

Sorry for the miserable description - it's been about a month since I
had the thing apart - just figured I'd post here to see if anyone had
any suggestions.

That sounds like a real old-timey one.

They're just rheostats. If you're intent on fixing the one you have,
rotsa ruck: that's a restoration job that may require materials (e.g.,
graphite discs) not easily available anymore. It sounds like there
should be some intermediate contact points between the ends of the
ceramic tube that make for variable resistance; see anything like that?
Obviously, the ceramic, which is an insulator, isn't going to allow any
such contact.

If you just wanted to get it working you could use a more modern foot
control, which is also just a rheostat but usually using resistance wire
instead of carbon objects.

Have you tried poking around the graphite pieces with an ohmmeter? You
could see if maybe there's a break in continuity (electrical) somewhere
that's making it go all-or-none.

 

[Adrian Tuddenham]

Anyone know how these old singer foot pedals work? There's not much
to this thing, but I can't for the life of me figure out how it's
supposed to work!

The one I have contains a long ceramic tube filled with a stack or
maybe 100 graphite disks. One end connects to the sewing machine
motor (I assume), and at the other end there's a contact that's
brought closer to and eventually touching the contact on the end of
the tube as the foot pedal is depressed.

The foot pedal was dropped and I'm trying to repair it, but so far I
can't get any variable speed out of it - I get either off (when the
contact isn't touching the end of the graphite-disc-tube) or ON-HIGH
when the contact touches the end of the graphite-disc-tube.

The contact resistance between the carbon discs is varied by the
pressure on the stack (in a similar way to the action of a carbon
microphone). There will be some sort of compression spring between the
operating lever and the top of the stack (it might be a leaf spring).
When the spring is almost fully compressed, a contact by-passes the
resistance stack and gives full power.

It sounds as though the compression system isn't functioning or the
by-pass contacts are closing too quickly. You need to identify an
adjustment screw somewhere in the linkage to the compression spring and
set up the pressure on the stack so that the compression is minimal when
contact is first made with the stack and increases until the motor is
nearly at full power before the by-pass contacts close.

I can supply a photograph of the inside of the controller for a 1950s
Model 201K (for 150 to 250 volt operation) if that would help you.

 

[Samuel M. Goldwasser]

The contact resistance between the carbon discs is varied by the
pressure on the stack (in a similar way to the action of a carbon
microphone). There will be some sort of compression spring between the
operating lever and the top of the stack (it might be a leaf spring).
When the spring is almost fully compressed, a contact by-passes the
resistance stack and gives full power.

It sounds as though the compression system isn't functioning or the
by-pass contacts are closing too quickly. You need to identify an
adjustment screw somewhere in the linkage to the compression spring and
set up the pressure on the stack so that the compression is minimal when
contact is first made with the stack and increases until the motor is
nearly at full power before the by-pass contacts close.

I can supply a photograph of the inside of the controller for a 1950s
Model 201K (for 150 to 250 volt operation) if that would help you.

It may also be possible to simply buy a replacement foot-pedal rheostat
but it would have to be matched up in terms of resistance range.

Of course, if you want authenticity, you'll have to repair it!

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[William Sommerwerck]

No one has said anything about replacing the pot with an SCR or triac
controller.

 

[[email protected]]

Wow - nice to see there's still activity on this list, and thanks for
all the replies!

KISS is my driver. I'd like to keep it simple, and cheap. Fixing the
existing part (if possible) is nearly always my first choice. Besides,
I no longer have access to my bench and most of my equipment - all I
have here is an old Weller soldering iron, some solder, my favorite
Tek scope, and a box full of parts I needed to fix something recently.
All the rest is in storage

Anyway, here's a shot of the pedal's guts, with some labels to help
clarify.

http://i151.photobucket.com/albums/s135/pxbacher/Miscellany/P4231021.jpg

1. Spring and Linkage. This is pressed downward when the pedal is
depressed.
2. Brass Linkage/Contact. This moves to the right via linkage 1 when
the pedal is depressed.
3. Copper Contact. This moves to the right and toward the graphite
contact on the left end of the Carbon Pile when the pedal is
depressed.
4. Carbon Pile. This is a long ceramic tube filled with ~100 graphite
discs and a graphite contact on either end.
5. Bypass Contact. When the pedal is fully depressed, the Brass
Linkage touches this contact and bypasses the Carbon Pile.

Now - here's what I didn't mention previously... I got this thing in
pieces at a garage sale, along with the sewing machine. The previous
owner had dropped the pedal, cracking the bakelite and spilling its
innards all over. He assured me nothing was missing, and when I
fiddled with it, it all seemed to fit into place (as shown). BUT, I'm
not 100% sure I'm not missing something, and I'm also not 100% sure I
have it assembled correctly. The Copper Contact was as shown (nearly
straight) when I got it - it doesn't make contact with the Carbon Pile
until the Brass Linkage is nearly touching the Bypass Contact. Also,
the slot where the Copper Contact and Brass Linkage tie together is
held together very tenuously - I'm afraid it's going to fall apart
every time I fully-depress the pedal.

So what I could use here is an evaluation of the parts and placements
- do I have everything? Is it all in the right place? I can't figure
any other way to set it up. Any other thoughts?

Thanks all!

-Pete

 

[David Nebenzahl]

Anyway, here's a shot of the pedal's guts, with some labels to help
clarify.

http://i151.photobucket.com/albums/s135/pxbacher/Miscellany/P4231021.jpg

1. Spring and Linkage. This is pressed downward when the pedal is
depressed.
2. Brass Linkage/Contact. This moves to the right via linkage 1 when
the pedal is depressed.
3. Copper Contact. This moves to the right and toward the graphite
contact on the left end of the Carbon Pile when the pedal is
depressed.
4. Carbon Pile. This is a long ceramic tube filled with ~100 graphite
discs and a graphite contact on either end.
5. Bypass Contact. When the pedal is fully depressed, the Brass
Linkage touches this contact and bypasses the Carbon Pile.

Now - here's what I didn't mention previously... I got this thing in
pieces at a garage sale, along with the sewing machine. The previous
owner had dropped the pedal, cracking the bakelite and spilling its
innards all over. He assured me nothing was missing, and when I
fiddled with it, it all seemed to fit into place (as shown). BUT, I'm
not 100% sure I'm not missing something, and I'm also not 100% sure I
have it assembled correctly. The Copper Contact was as shown (nearly
straight) when I got it - it doesn't make contact with the Carbon Pile
until the Brass Linkage is nearly touching the Bypass Contact. Also,
the slot where the Copper Contact and Brass Linkage tie together is
held together very tenuously - I'm afraid it's going to fall apart
every time I fully-depress the pedal.

So what I could use here is an evaluation of the parts and placements
- do I have everything? Is it all in the right place? I can't figure
any other way to set it up. Any other thoughts?

Pretty clear how it works now; as someone described up-thread, the pile
of carbon discs gets compressed, reducing their resistance. So obviously
this happens when the spring on the left (3) pushes on the metal stud at
the left end of the ceramic tube.

So apparently the problem is either that the carbon discs aren't making
enough contact with each other inside the tube, or are contaminated, or
that there's not enough pressure being exerted on the left end of the
tube by that spring. Which could mean that either it's not put together
correctly, that there's a part missing (though I can't see where), or
that something needs bending or some other adjustment to work correctly.

 

[Adrian Tuddenham]

[...]

It looks as though you hve got everything in the right place

[...]

The Copper Contact was as shown (nearly
straight) when I got it - it doesn't make contact with the Carbon Pile
until the Brass Linkage is nearly touching the Bypass Contact.

That's why you aren't getting a gradual start-up, the resistance isn't
coming into play until too late in the operating sequence.

Also,
the slot where the Copper Contact and Brass Linkage tie together is
held together very tenuously - I'm afraid it's going to fall apart
every time I fully-depress the pedal.

Gently curving the 'copper' (more likely phosphor bronze) strip towards
the pile would cause it to make contact earlier and would also change
the angle of the fork so that it held the brass linkage more positively.
Perhaps the fork should be angled more sharply to make sure it is well
hooked into the strip (be careful not to crease the metal and snap it).

Have you checked the carbon discs to make sure that some of them aren't
shattered - or some might be missing?. That would make the pile too
short to touch the 'copper' strip properly.

 

[Geo]

3. Copper Contact. This moves to the right and toward the graphite
contact on the left end of the Carbon Pile when the pedal is
depressed.

I would try adding some (conducting) padding at the centre of the bronze spring
(around the "3" area) to make contact with the carbon. Is it possible a
copper/brass disc is missing around there?