Need perfect radius

Decades ago as a teen I helped my Dad build a greenhouse from 20 foot 1/2" rebar bent into similar shapes. We had a straight section, then 180 deg bend with 4 foot radius, then final straight section. Stood 5 of them up in an 8x12 foot concrete slab and welded up a rebar center main beam and stringers to brace it up. Dad did the layout and fine bending, I did the welding with an old stick machine. Cranky neighbor came over and said that the first wind would blow it down so I jumped off the ladder and did a couple of chin-ups for him and he went away looking even more sour (Dad hid his grin but I saw it :-)). It's survived about 6 or 7 hurricanes so far including Frederic and Katrina and the edge of Maria :-). Anyway, we drew the shape with chalk on the concrete patio using a string as a compass to draw the semicircle, and did the bending over the 2 or 3 foot diameter center section of a large cable spool we used as a patio table. Use a piece of rebar a few feet longer than you want so you can cut off the ends where the curve won't be perfect. Bend a bit, check against the chalk template, rinse and repeat. Bend in small well separated steps, make sure you don't get any twisting, and you should be fine.

he base and some 1/2" rebar for the lamp itself. Base will be on one wall and light bulb will be about 7' away. I need to bend an 11' piece of rebar into a perfect arc. It would be 180 degrees of a circle. I am thinking to make a fixture out of plywood. Fixture would be similar to what an electri cian would use to bend conduit. I don't intend on heating rebar. Just ben d on fixture. Other way would be to create a fixture using a complete shee t of plywood. I think that is overkill.

Thank you Carl. My friend has some of the large spools you mention. I thin k that may be best way to go. If this prototype works well I will make 18 of them using a 20' length for my driveway. Did your greenhouse produce fo od for your family?

No, the greenhouse gave my Mom someplace besides the den to put all 50-100 of her potted flowers when a freeze was forecast. Dad and I felt all the construction labor was well worth it so we only had to bring the plants in once a winter instead of each time it got cold, then put them back out so we could use the den :-). One or two 100 watt light bulbs gave plenty of heat to keep the plants happy at night.

Unless you use Carl's suggested method, you'll need one of these:

;)

the base and some 1/2" rebar for the lamp itself. Base will be on one wal l and light bulb will be about 7' away. I need to bend an 11' piece of reb ar into a perfect arc. It would be 180 degrees of a circle. I am thinking t o make a fixture out of plywood. Fixture would be similar to what an elect rician would use to bend conduit. I don't intend on heating rebar. Just b end on fixture. Other way would be to create a fixture using a complete sh eet of plywood. I think that is overkill.

ink that may be best way to go. If this prototype works well I will make 1

8 of them using a 20' length for my driveway. Did your greenhouse produce food for your family?

If you really want to do it yourself, more power to you. If it was me, I'd take the rebar to a fab shop that does pipe and tube bending. They'd put it on a Buffalo or a modern equivalent, and you'd walk out with 18 pieces of nicely bent rebar in less than an hour -- probably much less. The cost prob ably would be about the same as a couple of sheets of thick plywood you'd u se for bending forms, based on shop charges I heard while writing an articl e about Buffalos, four years ago.

Here's the process I'm talking about:

That's a heavy piece of angle, but they change rollers to handle small pipe , tube, and barstock -- including rebar.

or the base and some 1/2" rebar for the lamp itself. Base will be on one w all and light bulb will be about 7' away. I need to bend an 11' piece of r ebar into a perfect arc. It would be 180 degrees of a circle. I am thinking to make a fixture out of plywood. Fixture would be similar to what an ele ctrician would use to bend conduit. I don't intend on heating rebar. Just bend on fixture. Other way would be to create a fixture using a complete sheet of plywood. I think that is overkill.

think that may be best way to go. If this prototype works well I will make 18 of them using a 20' length for my driveway. Did your greenhouse produc e food for your family?

d take the rebar to a fab shop that does pipe and tube bending. They'd put it on a Buffalo or a modern equivalent, and you'd walk out with 18 pieces o f nicely bent rebar in less than an hour -- probably much less. The cost pr obably would be about the same as a couple of sheets of thick plywood you'd use for bending forms, based on shop charges I heard while writing an arti cle about Buffalos, four years ago.

pe, tube, and barstock -- including rebar.

I think that is a very good idea. This project is down the road a ways but I will remember the good advice I got here from everybody. Thank you all.