Harbor Freight (Northern Tool too, I think) sells hydraulic pipe benders
that come with interchangeable "jaws? mandrels?" of different sizes.
These aren't all that expensive and do a great job. They have a built
in rollers and a hydraulic jack that you manually pump to get the
bending. Easy to pump. Goes slow enough that there is no worry about
going too far too fast, Easy to get the desired radius of curvature.
You can single handed bend a circle with a 20 ft length of rebar or make
a much tighter bend if desired. I have had mine for over 20 years.
Patrick NJ5G
On 10/20/2015 11:05 PM, Roger (K8RI) on TT wrote:
My opinion:
Typically the rebar only adds strength to the concrete base. IOW, You
don't need as large a base, or as strong a mix when rebar is used. If
you were "positive" the base could maintain structural integrity under
any conditions you wouldn't need rebar.
Regardless of whether welded or tied, The rebar normally doesn't need
a rigid connections. The ties only keep the rebar in place during the
pour.
If you don't need precision and are not making sharp bends in big
stuff you might be able to do the bending with a manual conduit
bender. Welding just makes building a rugged cage that can stand
rough handling easier. Just be sure to use rebar made for welding.
Welds on the normal stuff are quite fragile.
Bending rod, rerod, pipe, etc...into a circle is usually done with
three rollers. The rollers (Which usually have a radius cut into
them to keep the rod centered) are mounted in a triangular shape with
the bottom of the center one slightly below the tops of the outside
rollers (The height of this roller is adjustable). To bend much of
anything, these things can be pretty hefty. The distance between the
rollers is surprisingly short. Having them close reduces, or
eliminates waste.
There is a bit of a learning curve, but it's neither steep nor long. A
rough explanation: The center roller is raised so the rod can be
inserted over the outside rollers and under the center roller. Then
the center roller is lowered and tension applied. The first pass
produces a shallow arc. The center roller is lowered for each
successive pass which tightens the arc eventually into a circle
I've seen the rollers mounted into the top of a steel bench with a
movable center wheel. The rollers are powered and a center screw, or
hydraulic ram powers the movement of the center roller. With those
you have to be aware of the thd of tht piece coming back, or you could
skewer yourself.
73
Roger (K8RI
On 10/20/2015 11:29 AM, StellarCAT wrote:
Rohn says to use 8 #7 rebar (SERIOUSLY! 7/8”!!) ... and then it shows
‘#4 circular ties 2 1/2” OC with 2” cover with 24” laps’
huh?
I’ve always just dug a hole – usually around 3 x 3 x 3 ... put the
tower section in (with temp guys) ... put in a few pieces of 1/2” re
bar and been done with it .... but now I have to follow the Rohn
specifications which seem onerous at best (I know, I know – guys that
say “follow it to the letter”) ... and I’ve no clue what #4 circular
tie is. SURELY its not #4 rebar BENT in a circle!?
Googling so far hasn’t shown me anything that helps.
Gary
K9RX
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