Author Topic: Popular Mechanics Boiler  (Read 29786 times)

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #25 on: July 22, 2014, 09:15:34 PM »
Hi Tom, I don't think I'm going to have a problem with misalignment, but probably best to make it first and talk about it afterward.

Today I didn't have much time to work on the boiler, but I did make a smokestack. I used a piece of fence post brazed to a bit of 1/8" plate that I had turned into a washer to fit. That's for a mounting flange.

« Last Edit: January 12, 2018, 10:28:05 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #26 on: July 23, 2014, 03:32:06 PM »
By afternoon I had some paint on it and mounted the chimney. Now thinking about the firebox and door.

« Last Edit: January 12, 2018, 10:28:44 PM by vtsteam »
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Offline awemawson

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Re: Popular Mechanics Boiler
« Reply #27 on: July 23, 2014, 03:36:16 PM »
VERY flashy  :thumbup:

The heat losses on a design like that must be a high proportion of the input power. No real possibility of lagging, and a long response time due to the relatively thick wall of the boiler.

Looks the business though  :bow: :bow:
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #28 on: July 23, 2014, 04:04:48 PM »
There's a copper coil under the boiler, and the inside of the firebox will be insulated. Not shooting for high efficiency, though, just playing.  :beer:
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Offline Pete49

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Re: Popular Mechanics Boiler
« Reply #29 on: July 23, 2014, 10:27:42 PM »
well done Steve....might have to dig the book out and have a play too....if time permits :Doh:
Pete
oops..........oh no.........blast now I need to redo it

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #30 on: July 23, 2014, 11:26:48 PM »
Pete, thanks, that would be cool! I've got a gauge now, looking to hydrostatic test the boiler after I make a pump, still plenty to do.

Tim, sorry, missed your earlier post - thanks so much! :beer:
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #31 on: July 24, 2014, 09:05:03 PM »
Not much time today for fun stuff, but I did make a start on a hand pump. Rummaging around in my scrap barrel, I found this cutoff of what I think is brass. Could be bronze, I'm not sure. I have a small half nail keg of stuff like this -- mixed brass, bronze, and sintered bronze material that I got in an auction (real, not online) at a closed Hayward-Tyler machine shop.

Anyway, I thought this might work as a base:

« Last Edit: January 12, 2018, 10:29:38 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #32 on: July 24, 2014, 09:12:22 PM »
Milling a foot:

« Last Edit: January 12, 2018, 10:30:28 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #33 on: July 24, 2014, 09:23:29 PM »
And ended up with a blank for the base by supper time. Haven't quite decided how I'm going to do this pump yet, guess I'll figure it out tomorrow!   :scratch:  :coffee:

« Last Edit: January 12, 2018, 10:31:18 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #34 on: July 25, 2014, 09:14:14 PM »
Bah, chores all day, and then company for supper. Well, the last was good, but nothing much done on the pump except puzzling out how to do the valves with materials on hand.

I do have some stainless steel ball bearings 3/16" dia. and some 1/4" brass pipe for the pump body. But it's not exactly clear how I'll fit it as two check valves and pipe connections in the pump base.

I've looked in ME's and a few books for hand pump plans for ideas, but it's a subject that hasn't got as much attention as I would have thought. The few designs I've found in print often lack valve details, or are over-complicated or use odd thread sizes and large machined chunks of brass stock.

I want something simple, any threading ought to be managed with stock taps and dies and shouldn't require sculpting $50 of swarf out of a solid block. Ideally brass plumbing fittings might be used or adapted to the job.

I'm thinking that 3/16" balls would probably need a 1/8" bore at the seat.  I have some brass compression to NPT straight adapters that have a slightly larger bore at the pipe taper end -- maybe I can sleeve it with some 1/8" ID brass tubing, soldered in as a seat.
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Offline Ginger Nut

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Re: Popular Mechanics Boiler
« Reply #35 on: July 26, 2014, 01:20:45 AM »
You guys just keep impressing me with all you do. Great job.

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #36 on: July 26, 2014, 08:25:55 AM »
Thanks Ginger Nut  :beer:.

So this is the little design problem I'm thinking about. If you use a sliding ball as a check valve you need clearance around it to allow water to flow past when the valve is open. But if the valve is horizontally oriented, the weight of the ball tends to make it rest on the bottom of the large bore, off center.

To close, the ball moves to the valve seat end of the bore. The valve seat is a small hole, typically concentric with the bore. The ball closes the valve by basically plugging that hole.

But if the ball is off center, that means it must lift when it gets to the seat, since the ball was resting off center with the bore. Will that happen for sure? Seems like how surely it lifts depends on the amount of oversize of the bore, the size and weight of the ball, and how the seat is shaped.

If the seat is concave with a hole in the center, that would help the ball seat. But usually what is recommended for best seating is a convex seat with a hole in the center. I can imagine that if proportions of all these things weren't right, the ball might not lift and seat.

So the question is, how much oversize can the bore be to get good flow through the check valve for a 3/16" ball, when open, yet have the ball lift to the seat properly. And what shape and position should the seat be?

There are other design possibilities than the above:

1.) The sides of the bore could be grooved -- this would allow clearance around the ball for water flow, yet maintain a relatively tight guide clearance for the ball.

Question -- how to groove easily in this size valve (3/16" ball), and how to make a stop for the end opposite to the seat so that the flow can continue around the stop. Ball travel should only be about 1/32" to 1/16" by most accounts.

Possibilities -- maybe groove with a home made single toothed broach -- shaped like a chisel. Maybe use a pin as a stop in a cross drilled hole.

2.) The ball could be supported by a cage in a much larger overall bore to give clearance, but the ID of the cage could be close to the ball size to serve as a guide. Making and attaching a cage this small could be tricky/finicky.

Possibilities -- maybe a cage consisting of two hairpin shaped wires at right angles to each other. Maybe inserted in small holes in the seat and soldered there.

3.) Maybe the seat could have a double taper -- an internal convex cone with hole (volcano shape) and a larger concave cone lead in that lifts/guides the ball to center on the seat. This would require making a special cutter for this shape.

Writing this all out like this, it looks like #3 above would be the simplest. A home made cutter could even form the bore and the special seat in one operation if designed right

Still not sure what the optimum clearance would be for the bore vs ball size, though. I imagine even with such a cutter, it's possible to design a bore too large or too small to work well.


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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #37 on: July 26, 2014, 08:36:16 AM »
I'm thinking maybe 1/32" oversize dia for the bore, so 7/32" for the 3/16" ball. Hope that's not too tight for good flow in this size valve. But I guess I could enlarge it if it didn't work well.

Well I guess for hydrostatic pressure testing of a small boiler, the flow rate isn't important anyway.

It would be nice to know what works well, though if I need a hand feed pump at some point...
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #38 on: July 26, 2014, 08:49:11 AM »
And now working through this aloud (or in print) I realize that such a small oversize might not require a special seat, since the ball only has to lift 1/64" to center.

I guess the only thing to do now is just try things and see what happens.

I'll try a straight seat first.
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Steve
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Offline awemawson

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Re: Popular Mechanics Boiler
« Reply #39 on: July 26, 2014, 10:22:16 AM »
Don't blow your self up Steve  :zap:
Andrew Mawson
East Sussex

Offline Meldonmech

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Re: Popular Mechanics Boiler
« Reply #40 on: July 26, 2014, 11:07:06 AM »
 
   Nice job on the boiler Steve, it looks swell.

   Andrew, like your tip on the tippex, have made a mental note.

                                                       Cheers David

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #41 on: July 26, 2014, 01:11:59 PM »
Don't blow your self up Steve  :zap:

Okay.

This is just a hand pump for doing a static hydraulic test.
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Steve
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #42 on: July 26, 2014, 01:35:11 PM »
Thanks David!  :beer:

The pump check valve experiment has gone rather well today. Pictures later this evening....
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Steve
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Offline tom osselton

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Re: Popular Mechanics Boiler
« Reply #43 on: July 26, 2014, 02:22:57 PM »
Couldn't you make it like carb float valve a spring loaded rod tapered to make the seal grooved or flat sides to pass the water?

Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #44 on: July 26, 2014, 05:03:53 PM »
I guess you could Tom, but I made a free ball check valve today.

Here's how:

I started with about a one inch length of 3/4" round -- another scrap piece from my nail-keg 'o brass. Center drilled,



« Last Edit: January 12, 2018, 10:33:36 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #45 on: July 26, 2014, 05:05:22 PM »
Then drilled 1/8" through:

« Last Edit: January 12, 2018, 10:34:13 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #46 on: July 26, 2014, 05:07:53 PM »
Widened out one end to 7/32" for a depth of 0.75":

« Last Edit: January 12, 2018, 10:34:47 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #47 on: July 26, 2014, 05:12:12 PM »
Then I put a 3/16" ball in the wide end, and checked the depth. I wanted the ball to have 1/32" free movement to a cross pin  which was to be made of .092" dia. stock -- a bit of brazing rod. I worked out the center location for the pin and cross drilled it in the mill:

« Last Edit: January 12, 2018, 10:35:27 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #48 on: July 26, 2014, 05:15:39 PM »
Then back in the lathe, turned down one end to .375":

« Last Edit: January 12, 2018, 10:36:05 PM by vtsteam »
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Offline vtsteam

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Re: Popular Mechanics Boiler
« Reply #49 on: July 26, 2014, 05:17:29 PM »
And the other end also to .375":

« Last Edit: January 12, 2018, 10:36:52 PM by vtsteam »
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