Re: [TCML] Large Top Loads

[Steve Ward <steve.ward@xxxxxxxxx>]

It was some work, but yes, it can be done:

http://stevehv.4hv.org/ringtoroid/

The harbor freight bender needed some mods right from the get go.  I added
some 1/16" thick HDPE shims to keep the rollers from being able to move
laterally.  Even with this, its best to have a second person guiding the
tubing in real straight.  Its easy to get a slight cork-screw if your guider
isnt really on the ball.  A real tube bender would have up-right rollers to
keep the tube feeding in true.

I used some short pieces of 3/4" PVC as it fit super snug into the 1" OD AL
tube to join the ends.  The AL tube was .065" wall thickness.  Id suggest
buying at least one more tube than you need so you have 1 piece to get the
learning aspects out on.  The last picture shows the toroid how it really
ended up, with 8 supports and huge zip-ties to snugly hold all the rings in
shape.  Because my rings were slightly cork-screwed, they did not want to
sit perfectly, hence the need for more supports and the ties to hold them in
shape.  Certainly the next time through would give less problems.

Also note that the bender produces scrap at each end of the ring, about 6"
worth of material that cannot be bent.  So if you really want to get a 48"
toroid, you will probably have to get a few 20' lengths of tube, and the
rest could be 12' lengths.

The only other tool i used in my friends machine shop was the bandsaw to cut
the ends of the tube square.  This can be done with a hack-saw and some
patience if you dont happen to have access to a giant metal cutting saw :-).

http://www.teslauniverse.com/community/groups/ratcb#num=206&id=album-11

That link should point to some photos from the 2009 teslathon with operating
pictures of that toroid.  I'd say it works.

Steve

On Mon, Feb 15, 2010 at 10:05 AM, David Speck <Dave@xxxxxxxxxxxxxxxx> wrote:

> Jim,
>
> If you look in the back of Smithsonian, Discover, or Air and Space
> Magazine, you will often find a Harbor Freight ad good for 20% off any
> purchase.  A friend bought one of those rollers a few months ago.  Seems
> well built.
>
> I'm going to try using ~1" diameter rigid coax that I bought at a hamfest
> for next to nothing.  If I remove the outer PVC jacket, I'll have a nice
> corrugated copper tube for the toroid segments.  Probably will be a bit
> heavier than aluminum, though.  Just need time to try out the concept.
>  Aluminum tube is crazy expensive around here, unless you can find it
> surplus somewhere.
>
> Steve Ward made his beautiful toroid with a Harbor Freight bender.
>
> Dave
>
>  Harbor Freight has a  manually driven version for about $150. [Not sure if
>> it
>> could actually roll a 48" diameter x 1" aluminum tube.]  My question is:
>> has
>> anyone tried to fabricate a top load made of a cluster of aluminum tubing?
>>
>> Thanks,
>> Jim Zimmerschied
>>
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