"brian" wrote in
message ...
replying to Larry Jaques, brian wrote:
Hi Larry,
Tubing bender is just two expensive for fabrication just a few (as
little as
2) hoops. Just yesterday I found a contractor friend who says he has
a hand
conduit bender i can borrow. I figure I can just make small
incremental bends
and get my circular hoops. Now I just have to figure out how to
calculate
those incremental bends to get my 5 foot hoop.

If you google "model railroad helix" you will see imagines of what I
am
looking to build,...but an alternative method/materials.
Here is a forum subject thread I started on the project...
_http://model-railroad-hobbyist.com/node/30323?page=4_
In these photos you will see a 4 foot dia metal ring I found at a
junk yard
(likely a rim of of outdoor table). This would work for a 4 foot dia
helix,
but I was looking for 5 foot dia,...hence my search for bending
conduit into 5
foot dia circles. One hoop at the bottom, and one hoop at the
top,...then 8
vertical pieces joining the 2 hoops. Inside this 'open style barrel'
I would
coil up a spiral hoop(s) of PVC pipe onto which to lay the rr track.

https://www.polytechforum.com/img/5r

--
for full context, visit
http://www.polytechforum.com/metalwo...pe-639050-.htm


In that case you could bent the conduit into the two halves of an
octagon.

See "Offset Bends:"
https://www.gridalternatives.org/sit...enderGuide.pdf

The nominal OD of 3/4" conduit is 0.922", the ID is 0.824". If an EMT
compression coupling isn't rigid enough I don't know of another common
material to join the two halves unless you can turn down 1/2" pipe
from 0.840" to a snug press fit on a metal lathe (the R.C.M.
solution).
https://www.garvinindustries.com/fit...Fc6XfgodwMIG_A

-jsw