Bending tubing to a specific radius

sr guy · Feb 2, 2016

Go find a some crap trampolines and use the arches for your tops. Just add straits to create your height.

fried1765 · Feb 5, 2016

quicksandfarmer said:
I've been thinking about building a hoop greenhouse. I've been reading on the web about bending 1-3/8" fence top rail into hoops, there are several places that sell simple bending jigs that are not expensive. For example, here: Greenhouse Hoop Benders

The problem with the jigs is that they're set to predetermined sizes, which may not match the size I can get covering material in. So I've been thinking about making my own jigs. (This is the Build-it-yourself forum after all!). The question is, how do I size the jig to end up with a specific radius? It seems to me like the jig has to be smaller than the desired radius because I'll bend the stock to fit the jig and then it will spring back when I release it. Also, it seems like the shape of the jig is not a section of a circle but is instead a section of a parabola. Is that correct?

I've also looked at the Harbor Freight tubing roller (Tubing Roller). I can see how once I got it dialed in I could make exact bends repeatedly. But it's more money and it looks like it would be more work for what I'm doing.

Thoughts?

Thanks.

Perhaps you would like to buy my 17' x 50' hoop greenhouse.
I am about 100 miles from you.
Give me a call if you are interested: nine-41-nine-81-5584

Chopperhed · Feb 10, 2016

quicksandfarmer said:
I've been thinking about building a hoop greenhouse. I've been reading on the web about bending 1-3/8" fence top rail into hoops, there are several places that sell simple bending jigs that are not expensive. For example, here: Greenhouse Hoop Benders

The problem with the jigs is that they're set to predetermined sizes, which may not match the size I can get covering material in. So I've been thinking about making my own jigs. (This is the Build-it-yourself forum after all!). The question is, how do I size the jig to end up with a specific radius? It seems to me like the jig has to be smaller than the desired radius because I'll bend the stock to fit the jig and then it will spring back when I release it. Also, it seems like the shape of the jig is not a section of a circle but is instead a section of a parabola. Is that correct?

I've also looked at the Harbor Freight tubing roller (Tubing Roller). I can see how once I got it dialed in I could make exact bends repeatedly. But it's more money and it looks like it would be more work for what I'm doing.

Thoughts?

Thanks.

My self, I'd go with a tubing roller.

It might be a bit expensive, but it would reduce the labor immensely.

A guy who was handy with the tools could probably build one fairly cheap.

rweaver · Feb 11, 2016

check out johnny seeds out of maine for the high tunnel hoop bender works great and inexpensive

Xfaxman · Feb 12, 2016

rweaver said:
check out johnny seeds out of maine for the high tunnel hoop bender works great and inexpensive

Here is the link: Johnny's Selected Seeds - Superior Seeds & Gardening Tools

tbn7 · Feb 17, 2016

That link you posted to buildmyowngreenhouse has many different sizes and by varying the length of the pipe you can create different sizes with each bender. You could build your own bender, maybe make your own tube, smelt your own steel. Where does it end?

I know because I sometimes go too far. What would you be gaining if you built your own bender? Just for fun is a good answer, one that I use a lot. In that case, trial and error maybe the answer, I bet that is how they did it.

quicksandfarmer · Feb 17, 2016

tbn7 said:
That link you posted to buildmyowngreenhouse has many different sizes and by varying the length of the pipe you can create different sizes with each bender. You could build your own bender, maybe make your own tube, smelt your own steel. Where does it end? I know because I sometimes go too far. What would you be gaining if you built your own bender? Just for fun is a good answer, one that I use a lot. In that case, trial and error maybe the answer, I bet that is how they did it.

I saw the benders, and they look appealing. The issue I have is that they come set for a fixed radius, and only come in a few different sizes. So what if I want to make a hoop that is not in one of the fixed sizes?

I think trial and error is the answer.