[TheForge] bar twisters

[lama]

> Ed- Dave's twister applies pressure thru the large spring which pushes the
> pipe clamp carriage away from the motor.
> However, I am not at all sure that it is necessary at all to apply such
> pressure.

......pushes or pulls, same result. I have found that if I am twisting a
long piece,
it will seriously sag unless some tension is applied to the piece. Also when
I
reverse the twist, a kink tends to form at the point of reversal unless I
apply tension.

> I have the ferrari of storebought twisters- A Hebo, and it does
superlative
> twisting with no pulling action whatsoever.

...... I had no idea that there were "store-bought" twisters available. I
built mine
as a scaled down version of one of Albert Paley's home made twisters that
uses giant 3-phase elevator motors as a power source. There is no 3-phase
available within 5 miles of where I live. My machine is more of a home-made
Volkswagen dune buggy than a Ferrari.

> In fact, when you think about
> it, the piece should actually get shorter as it is twisted. My hebo has
dies
> that are just loose enough to allow the piece to contract as it is
twisted.
> Most material will not contract a noticeable amount unless you are really
> twisting it a lot.

......A single bar does not get shorter as it is twisted, in fact with a
little
tension to keep it from sagging, it will get longer than when it started. A
bundle
of pieces, on the other hand, will get shorter when twisted.

> The hebo has about a 5hp 3ph motor, with fiendish german gear reduction,
so
> the torque is extreme. It will twist 1 1/2" square cold as tight as you
> want, and a big problem with hot twisting is overtwisting to the point
where
> the metal just comes apart, like playdoh.

......Mine uses a 3/4 hp, 220 volt motor with an assortment of found parts &
pieces, a transmission from an old riding lawn mower, a gear reducer from a
local boat lift, chain & sprocket from a very old mini-bike, a pipe vice, a
spring
from a Murphy Bed, etc. The torque is also extreme but I know that it would
not
twist 1-1/2" square, cold. Matter of fact I probably wouldn't use 1-1/2"
square,
twisted. I would hammer it to octagon to achieve more facets and twist it
hot.
The picture on that page http://magichammer.freeservers.com/page11.html is
of
a 1-1/2" octagon twisted bed post. I find it harder to spot heat the 1-1/2"
stock
than to twist it.

> I was working on a piece of 1" square recently, with lots and lots of
> reverse twists, and I would twist a section, then put it in the forge and
> get the next bit hot, cooling with water the parts I didnt want to twist.
I
> over twisted it, at about the point when the twists were about 1/16"
apart,
> and the 1" square parted like tearing a hot chocolate chip cookie. If the
> twister was exerting a pulling force on the bar, this sort of hot parting
> would take place sooner.

...... I am pretty involved in being one with the metal when I am twisting
it
(especially when it is that big) and have not encountered the shearing
problem
that Ries describes here. I have on occasion put a piece of 1/2" square in
the machine and let it run until it finally shears off at one end. It makes
a nice
twisted piece with the ridge repeating about every 3/8" or so.
dave m

> ries
>