[modeleng] Re: steel boilers & Cu flues

Hi Harry and Patrick,

For the steam roller I am building, the designer Bill Harris specified steel 
boiler and Cu tubes. He outlines a method of expanding the tubes into the 
tubesheets by compressing a stack of semi hard rubber faucet washers inside 
the tubes with a screw thread and nut device. The idea is to have rubber 
inside the tube overlapping the tubesheet by a bit on each side. When it is 
expanded by tightening the screw up the centre of the washers, the copper is 
bulged out on both sides of the tubesheets. after tube expansion the screw 
is released and the washers relax to their original OD and can be withdrawn. 
He also describes a test jig to verify your tube rolling skills with a steel 
pipe nipple having two steel endcaps with drilled holes to simulate 
tubesheets. A pressure gauge and water hookup to the centre part of the 
nipple test chamber is filled with water and hydrostatically tested to 
verify the strength and tightness of the expanded tubes.

He recommends annealing the tubes thoroughly before expansion and having 
smooth chamfers on the holes both sides of the tubesheets.

Lots of people built Bill's Mich Cal shay, donkey engine, roller, and his 
Falk no 1 loco that were serialized in Live Steam in the 80's with no 
apparent trouble. All had this tube expanding technique specified.

I plan to do mine just as he described, and I have some confidence it will 
work fine based on Bill's success.

Good luck, Jeff Dayman

>From: Harry Wade <hww@xxxxxxxx>
>Reply-To: modeleng@xxxxxxxxxxxxx
>To: modeleng@xxxxxxxxxxxxx
>Subject: [modeleng] Re: steel boilers & Cu flues
>Date: Mon, 17 Sep 2007 16:43:42 -0500
>
>At 11:18 PM 9/17/07 +0200, you wrote:
> >I know that since all the Cu parts will be immersed in H2O, the delta 
>T=B0=
>=20
> >will not be so much, but I still wonder, if this wouldn't have an 
>effect=20
> >on loosening the tubes in the flanges.
>
>Patrick,
>        This combination doesn't seem to present a problem, or one that
>produces complaints which need to be aired out with any regularity, in the
>US else I'd have heard it.  However as with so may other things, the
>quality of the first installation job has a lot to do with how well the
>joint seal holds up.  I know that occasionally leaky Cu flues need to be
>re-rolled (or re-swaged), and that produces some conversation, mostly over
>where one might find a set of rolls that small.  Hopefully a steel boiler
>builder will offer their experience.
>
>Regards,
>Harry
>
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