Hi Vance,
Reference tube bending without kinks.
1. For cold bending small bore copper brass or
stainless tube, I pass the tube through
a length of tightly wound coil spring. Then bend tube over a
mandrel or by hand.
The coils prevent the tube diameter distorting. To remove bent
tube, simply "unscrew"
the coil spring from the tube.
My local hardware store carries coil springs down too .090" i/d.
2 For larger tubes I have used coil springs through the tube
bore, with same results.
180 degree bends are easily achieved with this method.
Need to ensure at least one end of coil spring is protruding in
order to grip and
unscrew. 9Or spring becomes a permanant fixture!.
Alternatively you could leave spring in place, dependant on final
usage.
3 I use same method for ensuring water feed pipes from tender to
boiler do not get
kinked in use, and looks prototypical if springs are visible on
outside.
4 Dependant on individual design needs, cold bending is still risky,
and copper or
stainless tubes can easily crack. Therefore even a low heating
temperature localised
in prime bending area helps the bending process considerably.
Tony D.
At 03:49 PM 3/14/01 -0700, VR Bass wrote:
> > Do you cut the steam line on the outflow side of the lubricator, then bend
> > it around towards the backhead and down the flue? I take it that this does
> > not interfere with removing the burner for cleaning?
>
>That's one way of doing it. I would not cut the line, but rather make an
>insert,
>with appropriate unions on each end, and put it between the steam line and
>the short pipe that comes out of the steam chest, right under the smokebox.
>Since the burner is removed from the backhead, it wouldn't be in the way.
>
>But it doesn't have to go into the flue, IMO. You will pick up lots of
>heat if it
>just sticks up into the smokebox. When I get around to doing this, I'll just
>make a coil a little less than the inside diameter of the smokebox and shove
>it inside there, up against the front tube sheet of the boiler.
>
>Another way of doing it is to reroute the steam line down the flue, which is
>how Roundhouse do it and how Charlie Mynhier did it on Jim Crabb's Ruby.
>This requires cutting a clearance notch in the burner's stop plate. Charlie
>used copper, which will flake and eventually fail, but he says it's so
>cheap and
>easy to work with that it's irrelevant. I got some stainless tubing at
>the K&S
>display that I plan to use, but Charlie's probably right about that being
>overkill.
>
> > How does one bend Stainless (or any other type) tubing without
> crimping it?
>
>The easiest way is probably to find a really big bolt, one with a pitch
>diameter
>the same as your intended coil. Use the threads to guide the bend and to
>support the sides without putting pressure on the inside of the bend. If you
>can't find a bolt that big, and don't have a thread-cutting lathe to make a
>similar fixture, then just go very slowly around a former, pulling on the
>tubing
>as you bend, and hope for the best. A little crimping is not fatal, though,
>because as long as the open cross-section inside is larger than the valve
>openings, you've still got enough steam coming through it to run the engine.
>
>regards,
> -vance-
>
>Vance Bass
>Albuquerque, New Mexico, USA
>Small-scale live steam resources: http://www.nmia.com/~vrbass
