[ATM] Arc Roller: was bending aluminum

[vorblesnak@peak.org]

>From memory, could not find the magazine but I will continue to look.

The diameter of the wheel is not as important as the offset between the
wheel pairs.  Imagine your tube is a straight line.  One wheel is on the
bottom, one wheel is one the top a little ways furthur on kind of like
      o
o=========o

The the first two, to the left, touch the tube and hold it in line.  The
third wheel at the right end is a little up, (or down depending on which
one you pair it with), and this forces the tube to bend as it is moved
through the group.  The one in Mother Earth was to bend ribs for a
greenhouse out of electrical conduit.  It required multiple passes to get
the curve and they talked about so many 16ths of an inch of deflection per
pass.

It has been a long time since I read the magazine.  I did make one and
bend a number of ribs.  I remember I had to beef up my wheel mounts so
they did not flex. The first one I ran through came out like a cork screw
because I did not control the feed.

David Davis
Toledo, OR  97391

> Ok,
> So, if I want to bend a 28 inch diameter out of 1 inch
> square tubing, what size diameter should I make the
> wheels and how far apart are they on the stationary
> piece?  I'm thinking of make altitude bearings for my
> ultralight 16" dob.
>
> However this is starting to sound a lot harder than
> what Jan posted using the fixed radius disk and
> concave form.
>
> Second question does this method bent up to the edge
> of the stock or do you have to cut part of it off
> after bending.
>
> Dale Eason
>
> --- Bob May <bobmay@nethere.com> wrote:
>
>> You really need to make the rollers from metal
>> rather than wood.  Wood will
>> work but you need to do some good precision work as
>> the three wheel method
>> needs to hold the positions of the three wheels
>> precisely.  Any slop or
>> flexibility will make the end product kinky as the
>> forces aren't consistent.
>> Also, for small diameter bends, you need to do the
>> work in stages til you
>> get where you need it.
>> Bob May
>> bobmay@nethere.com
>> http://nav.to/bobmay
>> http://bobmay.astronomy.net


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