Re: Toroid Design

Tesla List wrote:
> Original Poster: FutureT-at-aol-dot-com
> Ed,
> The aluminum dryer ducting is very good.  And interestingly, I've
> seen two different wall thicknesses for this material.  It is possible that
> the thicker-walled stuff is for industrial applications.  The thicker-walled
> material I have is duller in appearance than the more shiny looking
> thin walled material.  I would be interested to hear if anyone knows
> for sure about the different applications and where to obtain each wall
> thickness type.

> John Freau

John and all,

Looks like you are indeed correct! McMaster Carr shows a couple of
appropriate types of aluminum duct hose. One type, which looks to be the
type commonly sold in home improvement and hardware stores, is called
super-flex extendable aluminum duct hose. This material has 0.005" wall
thickness, can bend with a radius of 0.6D (where D is the diameter),
comes in 30" lengths, and can be stretched to a maximum length of 15
feet or 30 feet (apparently the latter is more tightly compressed

The other type is called semi-rigid duct hose. This comes in either
aluminum (or stainless steel - but supposedly it's a real pain to work
with), uses 0.008" material, and while flexible it doesn't look like it
extends in length. The aluminum material will bend with a radius of D,
and comes in 5 and 10 foot lengths. However, I've also seen commercial
heating and ventillation outfits use longer (20 foot) lengths of this
(or similar) material. While McMaster Carr stocks these in diameters up
to 12", they are available in larger (18-22") sizes as well from heating
and ventillaton suppliers. 

-- Bert --