# rolled caps

```
----------
From:  D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent:  Monday, April 20, 1998 9:04 AM
To:  Tesla List
Subject:  Re: rolled caps

to: Kevin

The two equations are equivalent -- the units conversion factor of 10^7
just makes them look different.

Regarding your rolled up caps -- when you roll the caps very tightly you
compress the dielectric thus reducing it to 1/2 its normal thickness.  A
1/2 appears in the demoninator which goes  "upstairs" to appear as a 2 x
the final value.  If you use 1/2 the unstressed thickness as the "d" in
your equation you will get the right values on the first calculation
without multiplication being necessary.

DR.RESONANCE-at-next-wave-dot-net

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: rolled caps
> Date: Sunday, April 19, 1998 4:25 PM
>
>
> ----------
> From:  Kevin Wahila [SMTP:kevinw-at-stny.lrun-dot-com]
> Sent:  Sunday, April 19, 1998 11:43 AM
> To:  tesla-at-pupman-dot-com
> Subject:  rolled caps
>
> a while ago i began planning and construction of my first rolled caps.
> since then my coiling was put on hold for some time.  now, as i go back
and
> look through my mail and information to refresh my memory, i have found a
> slight problem dealing with the equation to calculate capacitance for a
> rolled cap.  i have two different mails from the list with two different
>
> #1......
>
>             0.224 x K x A
>        C  = ------------- x (N - 1)
>                   D
>
> C = Capacitance (in microfarads)
> K = Dielectric constant
> D = Distance between plates in inches
> A = Area of plate in inches
> N = Number of plates
>
> and....
>
> #2.....
>
>                           2.248965 * 10^-7 * K * A
> C (microfarads) = ------------------------------------ * (N-1)
> K=dielectric
> const.
>                                          d
>
> !!!Again, you need to multiply this result by 2 for a rolled up cap.
> This is the formula I generally use when making homemade caps.
>
> ok, so which one is the right one?
>
> thanks,
> Kevin
>
>

```