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Posted by pdrahn@coinet.com on February 19, 2009, 12:31 pm
Please log in for more thread options > I recently purchased some new and used foot speed controls for universal
> type motors, the AC/DC brush and commutator type motors commonly found in
> many Foredom and other flex shaft motors, early Dremel Moto and other bra=
nds
> of rotary tools.
>
> The oldest one I bought was made in the '40s possibly, and uses a carbon
> resistance type element.
>
> A Foredom model SCR-1, made about '84, has a circuit board with about a
> dozen fairly common components on an actual circuit board.
> The clever characteristic of this unit, is a unique twisted section of fl=
at
> steel, making a helix (kinda like the antique toy tops used a twisted
> "screw" to make the top spin as it was pushed down from the extended
> position).
> This helix is attached to the movable pedal (with a swinging mount to all=
ow
> it to travel in an arc), and fits into a slot in a low cost pot (the type=
of
> PCB-mounted pot with a slot that allows the helix to pass thru it) . As t=
he
> pedal is pushed down, the pot wiper moves clockwise as the helix twist
> contact area changes, and then CCW as the pedal is allowed to raise to th=
e
> stop position.
> A hole in the ciruit board under the pot allows the helix to pass thru fa=
r
> enough for the pot to make a full sweep of the resistor track.
> The start switch is activated by a flat section on the rim of the plastic
> pot disk/dial, it's open when the pot is at zero, then as the pot is
> advanced, the switch is closed as the flat moves away from the switch (th=
e
> flat spot functions as a low spot on a cam lobe).
> The switch is just stamped from plated steel to fabricate the stationary,
> and the moving arm part of the switch.
> This model needs a spring to return the pedal to the up/stop position.
>
> A new Foredom model FCT-1 doesn't have a circuit board or a spring, they
> simply utilize a switch from a variable speed 120VAC power tool (such as
> drill, saber saw, sander etc).
> The switch plunger is oriented pointing up at the moveable pedal, so ther=
e
> is no need for clever levers, fulcrums, springs or anything other than th=
e
> switch. In the full upward position the outlet power is off, press the pe=
dal
> down and the tool starts and speeds up as the pedal is pressed further do=
wn.
> The odd thing about this model is, the label states that the current
> capacity is 2.5 A, although the switch itself is clearly marked with a
> rating of 6 A.
>
> Some fairly recent Linemaster motor speed control units, model/catalog
> number 980-SC3 are made with variable speed power tool switches, the same=
as
> the Foredom FCT-1, but they are labeled as a 6 A rating.
>
> I remember opening an old Necchi foot speed control as a pup, and it had
> resistance/heater wire on a big ceramic block and a wiper to make a crude
> rheostat to change the motor speed. Alternate your feet to warm them both=
.
>
> --
> WB
> .........
> metalworking projectswww.kwagmire.com/metal_proj.html
Do you have a use for the old style foot controls? Please let me know
if so! Several years go, at auction, I purchased a pallet full of
steel, bearings, gasket material and who knows what, including half a
case of new resistor type foot controls for universal motors. They
were part of an estate of a retired machinist. He made custom fishing
reel winders. The kind used to put bulk line on spinning reels. The
controls varied the speed of winding.
I tried to get drawings and BOM from the survivors, but they never
responded. I assume that was all destroyed. There was one sample unit
that worked, but no motors.
I never have been able to find a use for the controllers, but have
never had the courage to toss them, thinking that as soon as I did, I
would need them!
Regards, Paul.
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> type motors, the AC/DC brush and commutator type motors commonly found in
> many Foredom and other flex shaft motors, early Dremel Moto and other bra=