Re: Aluminum duct material for toroids

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Parpp807-at-aol-dot-com>

In a message dated 9/7/02 8:12:55 PM Central Daylight Time, Par pp 807 writes:

Hi Ed,

I am posting some recent correspondence on the subject of toroid construction.
I think it addresses many of your Qs. I hope you find this helpful. 

Happy day,
Ralph Zekelman

> Hi Scott,
>  
>  Pictures at:
>  http://hot-streamer-dot-com/temp/RalphsCoil/
>  Pics include the good, the bad and the  "this was thrown out."  :-(
>  
>  Enter the 5525K37 into the McMC search and it will take you to the center 
> of the category. Yes, this stuff is seamless. The flex-lok type is made of 
an 
> aluminum strip
>  around three inches wide. It is wound into a spiral and the seam is 
crimped 
> together.
>  My first effort at making a 4 x - toroid used this stuff. As you say, it's 
> no good. The
>  Al is like a thin foil. When I tried to pull it into shape the crimped 
seams 
> just came apart. I made one toroid and threw it out. John Freau uses the 
flex-
> lok as do most coilers. John makes a very nice toroid with the FL, but he 
has 
> skill. Maybe with
>  a little practice I could get improved results but the stuff I use is much 
> superior
>  to the FL. It is of a heavier gauge and it is seamless. It's pricier but 
it'
> s worth it.
>  I work it by stretching out the 2.5 ft length to the length of the 8 foot 
> bench. I then 
>  bend it into a near circle and fasten the ends. Warning: do not cut the 
> piece; keep it
>  full. Use one 2.5 ft section per toroid. The ducting is accordion pleated 
> and wound in a spiral. I would like to know how it's manufactured. On my 
> first toroid, I did cut the 2.5 foot section to make two toroids. The 
picture 
> with the aluminum foil covering the seam says it all. Things get messy if 
you 
> cut that edge. The uncut
>  piece will give you two-flush fitting edges that will produce an invisible 
> seam.
>  You can work the ducting to the desired diameter simply by squeezing the 
> pleats
>  back together until you get the correct size. The heavier gauge Al is 
easier 
> to work
>  without putting a bunch of dents into it. Stainless is too stiff to work 
> with. 
>  
>  I hope this helps. If you try what I am suggesting, please let me know 
what 
> happens.
>  
>  Happy day,
>  Ralph 
>    
>  >  In a recent posting to the Tesla list, you mention that the 
McMaster-Carr 
> #
>  > 5525K37 duct is "seamless", and easier to work with than the Flex-Lock 
> type 
>  > duct. Are you sure that both of these types of ducting are not made from 
a 
> 
>  >  single strip of aluminum, coiled in a helix with some sort of seam? Can 
> you 
>  > describe the differences between the two types of duct material, or 
> provide a 
>  > photo of each? I need to fabricate some small toroids for a magnifier 
> system 
>  > and would like to know what the options are. So far, I have used the 
very 
>  > thin-gage convoluted duct material from Home Depot, which I think is the 
> Flex-
>  > Lock type. It's so delicate that no matter how carefully the toroids are 
>  > handled, they pick up small dents & dings & soon look pretty ratty.I 
have 
>  > also tried the convoluted stainless steel duct material used for 
re-lining 
> 
>  > chimneys, but its so stiff that the bend radius is impossibly large.
>  >  
>  >  Regards,
>  >  Scott Hanson
>  >  
>