Flying a (steaming) kite

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Mike Rometer
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Re: Flying a (steaming) kite

Post by Mike Rometer » Sun Jun 28, 2020 9:02 am

Mike, a lot will depend on the type of bender employed, some cheaper one are definitely not up to muster, it needs one with a supporting die on the outside of the bend, such as, https://rothenberger.com/ae-en/pipe-ben ... ender.html. It isn't a good idea to bend too close to the open end of a pipe anyway, so leave it over-length and re-cut after. As insurance you could also add a plumbers type bending spring to support the shape, though they can come with their own problems, like getting stuck if the bend is too tight. Also as long as the expander will go in it should take care of any minor imperfection to the 'round'.

I like the idea that if you need more output, just add more tubes and make it longer.
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Re: Flying a (steaming) kite

Post by RNoe » Sun Jun 28, 2020 3:09 pm

I'm with Mike.
I'm also in favor of the simplicity of a VFT for "hobby" steaming, despite the improved efficiency offered by that more complex design.
I see the need for at least 8 different bending jigs to make that boiler design.
Not so much a Home Shop operation.
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Re: Flying a (steaming) kite

Post by Mike Rometer » Sun Jun 28, 2020 5:14 pm

RNoe wrote:
Sun Jun 28, 2020 3:09 pm
I'm with Mike.
I'm also in favor of the simplicity of a VFT for "hobby" steaming, despite the improved efficiency offered by that more complex design.
I see the need for at least 8 different bending jigs to make that boiler design.
Not so much a Home Shop operation.
RussN
Or one, multi-purpose, adjustable one?

I was thinking a board with moveable pegs. Still quite a job to construct. :(
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Re: Flying a (steaming) kite

Post by PeteThePen1 » Mon Jun 29, 2020 10:09 am

Yes, I think that the six different pipe shapes are a bit of an issue.

However, Mike R has a point about a basic board to which one could add a lever with several mounting points for the bend wheel (if that is its correct name). Bearing in mind that steamboating is a very co-operative hobby, I would have thought that a design for such a jig could be developed by discussion and then built and passed on when the individual has finished his/her bending. Of course the other possibility is a team working together where one person bends all the pipes for everybody (ouch!) while another drills all the drums for everybody and so on. That is what a team in Australia have done to make some John King 3 drum boilers.

I think the bending boards would be relatively easy to make by somebody with good woodworking skills. The boards could be made up of multiple strips of (say) oak for long life, would be easily cut to the design curves and could be easily channeled with a palm router and a half round cutter.

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Re: Flying a (steaming) kite

Post by fredrosse » Mon Jun 29, 2020 2:57 pm

".......Also as long as the expander will go in it should take care of any minor imperfection to the 'round'."

The rules for tube expansion require a tube insertion hole that is only a couple of thousanths (human hair diameter) larger than ther tube outside diameter. Getting an "out of round" tube into a close diameter hole is the issue, not rolling the tube after it is inserted.
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Re: Flying a (steaming) kite

Post by Lopez Mike » Mon Jun 29, 2020 5:02 pm

Hasn't this been done with screw in flare fittings or some such solution? That would take care of the slightly out of round tube issue. Or is the wall thickness of these recommended tubes too much for flaring? Or is a flare fitting not allowed inside for a boiler.

I've certainly had a flare fitting fail by cracking due to vibration on my steam pipe. It was right out of the scene inThe African Queen only I didn't try to wrap a rag around it! I just throttled the engine with the isolation valve at the boiler and left my throttle valve at the engine wide open. That way the failure point had much reduced pressure and I could limp home with only my foolish pride scalded. Got on the web that night and ordered a flexible steam hose forthwith!
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Re: Flying a (steaming) kite

Post by fredrosse » Sat Jul 18, 2020 2:02 pm

"Or is a flare fitting not allowed inside for a boiler?"

Flared fittings, as well as compression fittings of any sort, are not allowed in the hot gas/furnace space of a steam boiler according to the ASME Boiler Code. One exception is the Bryant Watertube boiler design, they got approval for their special attachment of water tubes to the drums of their boilers, and this mechanical connection is in the hot gas areas of the boiler. They use a tapped thread, made in the boiler drum, and use 3/8 bolts to hold tubes against the drum. A dubious design in my view, but it is approved for that specific manufacturer.

In my view, go with Swagelok Fittings, very reliable fittings.
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Re: Flying a (steaming) kite

Post by fredrosse » Sat Jul 18, 2020 2:24 pm

Yesterday I picked up new tubesheets for a 16 inch diameter vertical firetube boiler. 85 firetubes, one inch nominal diameter.

I supplied the boiler plate, 3/8" thick A516GR70 steel, which I have material certifications for, which complies with the ASME Boiler Code as far as allowable material here. The steel cost about $30US.

The tubesheets were cut using a CNC plasma cutter, and the commercial shop where the sheets were made had to convert my PDF drawing of the tubesheet into proper CNC cutting code, a task that took them far longer than machine setup and cutting. Then they made the two tubesheets, all for the total price of $58US.
Tubesheet2020b.jpg
Tubesheet2020b.jpg (48.8 KiB) Viewed 5447 times
I had them make the holes about 0.040" (1mm) smaller than the tubes, so I will ream out the holes for a close fit to the tube diameter. That operation can be done very fast as there is very little material to remove. Then I must grind a bevel on the outside for a full penetration weld on the 16 inch boiler shell, and countersink a chamfer on the tube holes to allow seal welding after the tubes are rolled in place.
Last edited by fredrosse on Sun Jul 19, 2020 7:04 pm, edited 1 time in total.
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Re: Flying a (steaming) kite

Post by RNoe » Sat Jul 18, 2020 3:46 pm

Looks good!
I really like the modern CNC cutting capabilities: Water jet, laser, plasma.

And I hope you will perform the tube hole reaming after the sheet is welded to the main boiler tube?
Otherwise hole deformations might occur?
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Re: Flying a (steaming) kite

Post by RGSP » Sat Jul 18, 2020 4:02 pm

fredrosse wrote:
Sat Jul 18, 2020 2:02 pm
In my view, go with Swagelok Fittings, very reliable fittings.
Agreed. Anyone who has done one of the approved swagelok courses on their fittings ought to agree as well. They are a form of compression fitting though, so is there some let-out clause for using them in boilers? There probably ought to be.

The allowable degree of expansion for expanded tubes must vary with the tube diameter, I would have said go for a good sliding fit, but I have seen traction engine boiler tubes replaced where the tubes were distinctly sloppy in the holes, and I know that boiler lasted more than another ten years with no leaks.

What about cunifer tubes? I guess the allowable expansion must depend on the hardness state of the tubes as supplied, which opens another bag of worms...
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