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? rolling strap for double helix

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.

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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

Reply to
stevethompson
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Reply to
RoyJ

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.

Reply to
Ted Frater

Before you build another rolling machine, try rolling the strap so it makes a spiral that is close wrapped. ie the coils touch each other. Then stretch to make the spacing of the coils what you desire.

=20 Dan

Reply to
dcaster

Reply to
RoyJ

" snipped-for-privacy@krl.org" fired this volley in news:a96b9f3d- snipped-for-privacy@e21g2000yqb.googlegroups.com:

Dan, how would you do that with a roller that had bearing bosses at both ends? The spacing would _have_ to be at least as wide as the thickness of the boss.

The only way I see achieving that end is with cantelevered rollers.

LLoyd

Reply to
Lloyd E. Sponenburgh

See

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Reply to
Don Foreman

Steel outfits that manufacture tanks have long open ended rollers for rolling the metal to make the tanks. Some culvert manufacturers roll a spiral formed culvert. they would have the rollers to do the job.

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Reply to
Paul G. Shultz

O.P. here.

Don, I think your link confirms my ideas. I'm going ahead with my plans to build a roller.

Like other posters who have replied, I couldn't visualize how strap would behave differently than round rod in this situation. When I wrapped the strap around the PVC pipe, 1 and 1/2 revolutions in six feet, the strap would not lay flat against the pipe. One edge of the strap would be touching the pipe; the other edge was 3/4 inch off the pipe. It looked awful.

I think what needs to be done is form the strap in two directions at once.. Through the thickness like rolling a ring, and across the flat like creating a flat ring. I hope that makes sense. Anyhow, I'm going to make a roller-nothing ventured, nothing learned.

Thanks, Steve

Reply to
stevethompson

The original post said he was using a HF ring roller. The HF ring roller has cantalevered rolls.

Dan

Reply to
dcaster

Hmmmm. As I recall that is how Ernie says he makes banisters for spiral staircases. Will have to see if I can find more information.

Dan

Reply to
dcaster

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