wrote:
I want to build a trellis, the design of which was inspired by DNA's
double helix. Here's a picture from a gardening catalogue.

http://www.gardeners.com/estate-trel...efault,pd.html

I'll relate my failed efforts to build it; then my proposed solution.
Feedback appreciated.

I was feeling pretty smug; I happen to have a six foot PVC pipe,
eighteen inches in diameter, with 1/2 inch thick walls. Perfect for a
form for this project. I'm using 1/8 by one inch strap because it's
been gathering dust on my shelves for years. No amount of clamping to
the form got me anywhere close.

Then it was time to bring out the HF roller. I can roll eighteen inch
circles with it, but the coils won't stretch out properly.

Then I tried putting the strap through the roller at an angle-maybe 10
degrees from parallel with the roller ends. That angle put a lateral
force on the first roller that kept forcing the retainer to pop off.
The retainer clip is just that-a retainer clip-and not designed to
resist much pressure. I managed to get about 15 inches of strap
through the roller by replacing the roller and clip several times.
Wrong setup, but the 15 inches I got through the roller looks like I'm
thinking on the right track.

Looking at the picture, the strap appears to be at approx. a 45 degree
angle to the center post. So now I'm thinking I need to feed the
strap through the rollers at a 45 degree angle. In order to do that,
I'll need a roller that's four to six inches wide. I contacted
several local machine shops and all I got was a good luck pat on the
back. I've looked around the net and haven't seen one that would do
the job. I figure if they're that hard to find, if I did find one, it
would be out of my price range.

Now I'm considering building a roller. I'm thinking of modifying the
roller that Keith Marshall posted in the past week; I think it's a
very nice piece of work. I've already scrounged a lot of the iron,
but I'll have to pay for lathe work.

So, my question, before I invest the time and money, is my idea of
rolling the strap at an angle going to work?

Thanks,
Steve

Try the following.
Coil the strapping around your poly pipe the no of turns you want in
your helix.
Cut off to length.
Remove from pipe. lay on flat board or smooth ground/ concrete/tarmac.
Get someone to hold one end firmly. you take the other end and
stretch. You will find it will become the helix you desire for the
length you want.
Tyr it with some wire first.
Forfet rolling. It will go by itself. Report back your results.
Ted
Dorset
UK.