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Re: Pancake coils

Hi Peter,
              I've tried to build some of these old plans so I can probably
find the modern equivalent materials for you.  My comments:

> Original Poster: peterB <zardoz-at-albany-dot-net>
>
> Hello,
> This is my first post to this list.

Good - keep it up

> I am planning to build a 'kicking coil' outfit based on plans in Stanley
> Curtis's book
> 'Experimental High Frequency Apparatus..'.

> I have read through many of the archived posts looking for answers to a
> few questions
> and have only found a partial answer for one question, (for a different
> application,
> however)
>
> My first question concerns the winding of the secondary, which is 150
> layers of 30 awg dcc
> wire, each layer separated by 'oiled paper' .003" thick.
> I am looking for a suitable substitute for 'oiled paper'. I am not sure
> of heat buildup
> inside the primary, so this may be an issue.
> I have considered parafining regular paper for this, but this job may be
> a bit much,
> especially if there is an 'off the shelf' item available.
> I was also considering 'empire cloth' (not available anymore) but I
> believe it is simply
> varnished cloth. If this is what it is, this may be a feasible option.

 A modern version of empire cloth and something similar to oiled paper are
used by transformer manufacturers.  You will probably do ok by just
impregnating normal paper with mineral oil or parafin wax.

> Question 2: I have about 10lbs of 26awg dcc wire (old) and for that
> reason many of the coils
> (including the above mentioned pancake that calls for 30awg) will be
> using this.
> I have seen some formulas for wire use, # of turns etc, but none that
> would allow me
> to plug in 26awg and spit out coil length, # of turns etc. Is there a
> method of determining
> secondary construction when I am limited to a certain awg?

Its not too hard, just divide the winding length (the length from one end of
the bobin to the other) by the wire diameter (in your case 0.018 inches)
to give you the number of turns per layer then wind as many layers as you
need to give the number of turns you need.

>
> Also, relating to the above two questions, certain dimensions for the
> pancake are based on the
> 30awg wire. ex.-spacing of the turns, number of turns per inch etc.
> I am wondering if I can use simple algebra to scale up all the
> dimensions using 26 instead
> of 30awg. for ex: using 30awg, the width of the layers shows as 1" turns
> spaced 1/8"
> apart(First 50 layers). so- 30/1=26/x, solve for x to get the new width.
> Will this be ok to scale all
> dimensions?

Unfortunately not as wire guages are not linear.

> Q4: The plan calls for a 'hard rubber' cylinder drilled lengthwise
> through the center to accept
> a brass rod, the top of which suports the discharge ball. Any sources
> for 'hard rubber' rods
> (about 1 1/4" diameter) or substitutes?

Any acrylic bar stock will do - 'hard rubber' is just an early plastic.

> Last question: The capacitor is 20 units of 10 plates each equiling
> .1mfd. (I do not know what
> the voltage should be, this coil uses ac that powers a kicking coil)
> What would be a modern
> equivelant?

Thankfully for you the modern equivalent is a lot smaller :-)  For a kick
style induction coil you are probably running off 12V DC so, as the
inductive kick can be pretty big, I'd go for a 1µF non-polarised
polypropelene or polyester capacitor with a fairly high current rating.

> Thanks for all your help.

Thats what we're here for :-)

Regards
Nick Field

> -Peter B.
>
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