# Re: Small toroids

```Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 4/14/03 9:17:26 PM Eastern Daylight Time,
tesla-at-pupman-dot-com writes:

>Hi Everyone,
>
>Has anyone out there made toroids as small as 8"OD from 3" drier duct?  I
>have spent half of the afternoon trying to fashion a decent joint, and
>after failing to join the two decently, decided to make the joint with
>masking tape, figuring I could cover the whole thing with aluminum tape
>anyhow.  I have already wasted a roll of tape trying to make a smooth
>surface, and I am very close to jumping on the whole darn thing.  Any ideas
>on how to make a decent splice without covering the toroid with tape, or
>how can I get a decent finish if I do tape it?
>
>Thanks,
>John Richardson

HI John,
If you cut the tape into modified lunes, you will get a smoother surface. A
lune is like the surface of a segment of an orange, wide at the middle and
narrow at each end. Normal lunes are pointed at each end and cover the
surface of a sphere. If the ends are broadened slightly, they will cover
the surface of a toroid. Working out the exact shape is not necessary, and
its real B-Buster math. But let's say you are using 30 strips. Then make
each piece 1/25 of the outer circumference at its middle and 1/25 of the
inner circumference at each end. Draw the sides with a fairly smooth curve
and cut them out. these will allow enough overlap and be fairly close to
right size. For your 8" toroid made of 3" duct, (2" ID), you would need 30
strips ~9.5" long, each an inch wide in the middle and 0.25" wide at each end.

Hope this helps,
Matt D.

```