Re: polyethylene sheet used by builders.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

rolled plastic caps were all the TC hobby rage a few years back before the
advent of the MMC.  If you want to make a rolled cap, bear in mind the
following:

1) use 3 layers of plastic.  Many thin layers is better than 1 thick layer,
because a) it's easier to roll, and b) a pinhole defect in the plastic (and
they are very common) doesn't kill the capacitor.

2) Attaching to the aluminum foil plates is a royal pain.

3) You have to soak it in oil or it will die very quickly from corona on the
edges of the plates and/or small voids in the roll

4) You really need a vacuum pump to get all the air bubbles out of the roll.

5) It takes a remarkable amount of plastic and foil to make a decent sized
cap.

All in all, you're better off saving the pennies to buy parts for a MMC...
take advantage of all that engineering knowhow that goes into the
polypropylene high current, low ESR caps...  If you're really short of cash,
run the MMCs over their limits, and pray for good luck.. (I believe this was
called the EMMC)..


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, September 12, 2002 10:14 PM
Subject: polyethylene sheet used by builders.


> Original poster: "Justin Wright by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ellis_p-at-picknowl-dot-com.au>
>
> Hi All,
>
> I was at the hardware store last night looking for buckets for a
> capacitor (yeah tom!) and I noticed some big roles of builders plastic.
> The label said it was polyethylene.
>
> The plastic comes in a variety of styles, black, orange and clear.
>
> Would there be any reason not to use this for making a capacitor?  It
> was about $5 per metre and was about 2 metres wide.
>
> I am not sure how thick it is, but it feels thick and durable.  What is
> the best thickness to use?
>
>
>
> regards
>
>
> Justin Wright
>
>
>
>