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Re: Secondary coil forms and winding jigs

Tesla List wrote:
> 
> Original Poster: RWB355-at-aol-dot-com
> 
> Hi Bart, all:
> 
> Bart wrote:
>  Also, I've partially built a winding jig using a variable dc motor. A dc
>  motor should work excellent for tension. Applying 5v to say a 24v motor
will
>  begin it rotating, but slight tension will load it by slowing or
stopping as
>  the torque is very low at this voltage. Once the coil form is mounted and
>  the winding spool is set, the tension and speed can be set via the voltage
>  to the motor. Additionally, the winding spool itself will need a variable
>  drag built it to final set the tension and speed. I still haven't used
it as
>  I'm in "think mode" for the coil form attachments, but the rest is finished
>  and the idea should work well and allow proper tensioning.
> 
> If I read you correctly, your are pondering on how to attach your coil
form to
> the winding jig? Well, how about (I did it this way) using a threaded rod
> (about 20" longer than your coil form length). Now you take two pieces of
wood
> and make a cross (which fits rather tightly inside your form) out of them.
> Make two sets of these (front and rear of coil). For very big coil forms I
> would go for a total of three sets (one in the middle).  Place the crosses
> inside your coil form and prevent them from slipping around with two nuts on
> each side (allowing you to interlock the nuts and the crosses to the
threaded
> rod). This centers your coil form around the rod. Now take two more
pieces of
> wood and place them on the threaded rod (secure with two nuts, too). This
will
> provide more than enough clamping force to rotate your coil form via a
motor.
> If you plan on building lots of coils I would go for a set of ball bearings
> (to let the rod spin easily) on the end bearings. Otherwise (as in my
case) a
> piece of wood (1" by 2") provides more than enough bearing surface. After
> about 6000 revolutions (just a guess, could be plus / minus 500 revs) my
> "wooden bearings" didnīt show much wear, even though the threaded rod was
> running directly on the wood surface. (you could slightly see the thread
> pattern in the wood, but it was not as deep as the full thread heigth.
> 
> Winding jig greets from Germany,
> Reinhard
Terry, Reinhard, ALL

I've been using a winding jig consisting of a 12VDC windshield wiper
motor powered at 18V through a 60V -at- 75A Power FET PWM'd by a 555.
I've wound coils up to 24"OD and 3 feet long with no overloading.
The windshield wiper motor drives a 3/8" all-thread shaft supported
at both ends by 3/8" bulkhead bearing assemblies.  The "tailstock"
bearing end is moveable on a wooden track and locked down with bolt and
wingnut.

The coils have a fiberglass top and bottom assembled with a 3/8"
tapped hole concentric with coilform.  Thread shaft up coil with
VSD portable drill, and lock at both ends with 3/8 nuts.  I place
a spring loaded wire carrier 15'+ behind winder, and manually control
wire feed using leather gloves (protect those fingers!!!).  A slight
negative rake (5-10 degrees) will allow perfect close winding.  The
motor comes with two speeds (low / fast), I wired a DPDT switch to allow
for motor reversal, and PWM allows speed from 0.5% (motor squeals, but
does not rotate), to 100% (about 2 turns/sec) in "high gear".  I
included a turn counter triggered by a through beam photoeye to a 12VDC
mechanical counter with reset.

I can easily wind a 800 turn coil in less than 10 minutes, not including
coil setup time which is required anyway. The FET's are fused at 10A
against motor lockup, and have successfully blown without destroying the
FET's.  Total cost out of pocket <$50 and about 3 weeks to wire and
assemble; and worth every dime.  I have run circuit 3 days non stop
while curing polyurtheane on coil form, and the motor was the only
component showing evidence of heating.  Windshield wiper motors are
cheap (less than <$20) in most locations, and are very powerful for
their size.  I have schematic around here somewhere, may draw up in
Excel and have available if interested.

Regards

DAVE SHARPE, TCBOR