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Post by Shawki Shlemon on Mar 31, 2013 9:19:27 GMT
Pete , is that to part 1 or part 3 code , you may get in trouble with some clubs deviating from the code . It is your choice , the flange is not hard to do . Good luck .
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philh1
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Post by philh1 on Mar 31, 2013 10:57:57 GMT
Pete,
Just noticed your kind offer to supply the formers by mail. Thanks very much but my boiler will be slightly different. I am using Northumbrian as a boiler design exercise in addition to building the rest of the engine. I have purposely bought a 1' length of 2 3/4" tube to help push me though the process i.e., now the design has got to be different.
I have now located virtually all the model boiler design rules and I will be writing a paper on its design. A guy from another forum has offered to check my sums before testing it on the boiler inspectors from my club. I will then buy the rest of the materials.
By the way, nice to see the progress on your boiler. I have now made the frames for the engine and Ill post the pictures showing my progress on the other thread.
PhilH
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Post by doubletop on Mar 31, 2013 21:18:14 GMT
Phil
2.75"? doesn't this boiler require 3" tube? The smaller tube will reduce your boiler volume by about 16% and it not that big to start with (see my earlier photo). I'd suggest you want to get this boiler as big as you can.
I don't know but intuativley there must be a point where the mass of copper required to meet code, the volume of the boiler and size of grate come to a point where the heat is only just overcoming the heat loss from the copper. Although if you take that to the extreme you could have a flash steam boiler.
One of the guys in our club is doing a Canterbury Lamb and has used some slightly smaller tube and it just looks wrong. I'm guessing when he gets around to it he's going to have problems steaming.
I sense a debate starting now...
Pete
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peteh
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Post by peteh on Apr 1, 2013 0:49:23 GMT
Shawki Shlemon - AMBSC Part 1 phil1 - original design is 3" and I agree with Pete (DT) that you may have problems steaming. @all - whilst I have no problems with the boiler discussion to be here, as I regard this thread as an 'all things Northumbrian' thread, I think it may be benificial to have it in the boilers section as then more knowledgable MEs will find it and be able to contribute. just my 2c worth
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Post by Jim on Apr 1, 2013 7:20:35 GMT
I'd agree with you Pete.  Jim |
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philh1
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Post by philh1 on Apr 1, 2013 10:15:47 GMT
Guys,
It will be interesting to find out won't it? I don't believe there is any code issue because of the variability or existing boiler designs. For example, the size of an atlantic/ wide firebox type verus the 'between frames' type of firebox. It will be interesting to find the constraints and see what happens.
By the way, the small Tich boiler is 2 1/2" diameter and I appreciate that LBSC made a larger version (probably to improve performance) but I did see about 4 small boilered versions at an exhibition last year.
You guys might be right but lets find out.
PhilH
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peteh
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Post by peteh on Apr 1, 2013 13:00:12 GMT
Here's the state of play at the end of the Easter break - all plates shaped except the throat plate which I am still trying to decide which is the best way to tackle - external flange, internal flange or no flange to the boiler barrel. Not sure why the backhead appears to have a bulge around 3 O'clock, not noticable on the actual piece All plates other than the firbox plates need milling/filing to correct height, and then all the holes need drilling. My boiler inspectors comment was to drill under size and then file out to size, allowing to correct position if drilled slightly out. Having no DRO's this may be the route I take. Attachments:
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peteh
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Post by peteh on Apr 1, 2013 13:03:25 GMT
Having now flanged plates using three diffenent types of former - wood, solid metal and 1/8 (3mm) plate and wood backing I have decided I like the plate and wood option. I used this for the backhead and throat plate. Reasonable quick to make. I used three M4 bolts threaded into the plate from the back to hold it together, with the bolts filed flush to the face of the metal.
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philh1
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Post by philh1 on Apr 1, 2013 16:07:27 GMT
Looks good Pete. Regarding the throatplate, have you seen examples of an internal or external flange for a round top boiler like this?
PhilH
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Post by Jim on Apr 1, 2013 21:10:57 GMT
Making good progress Pete, you'll soon be in steam and enjoying every minute of it. Jim |
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peteh
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Post by peteh on Apr 2, 2013 23:56:45 GMT
Regarding the throatplate, have you seen examples of an internal or external flange for a round top boiler like this? PhilH In a word - No  |
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peteh
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Post by peteh on Apr 2, 2013 23:59:56 GMT
Having done more research into 'Tobin Bronze' I am confused. It is more acurately a 'brass' not bronze Cu, Zn and 1% tin. Yet we are told brass is unacceptable for boiler bushes due to de zincification - go figure!
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jma1009
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Post by jma1009 on Apr 3, 2013 0:18:15 GMT
hi pete,
ignore tobin bronze for boiler work please!
phil,
there is nothing wrong with small dimensional changes, so long as the overall design of the boiler isnt altered. however, the change in diameter you have suggested will impact on all sorts of things such as clearance between tubes and their layout and possibly their diameter to fit everything in. i am not familiar with the NORTHUMBRIAN design, but in the smaller scales getting everything to fit ok with adequate clearances to ensure proper steaming is something i wouldnt advise a tyro to do. those with a bit more experience can play about with such things based on experience of what produces a successful boiler. i had a friend who had acquired a very long length of 4" copper tube and most of his boilers were made out of this stuff regardless of the drawings he was working to. in quite a few cases the boilers turned out to be 'duds' and wouldnt steam for toffee! when one considers the work involved in making a boiler and the cost of silver solder, it isnt worth the risk of messing about with a PROVEN published design unless you have the 'know how' to improve upon a published design. i dont know whether the NORTHUMBRIAN boiler has been 'proven'. some of the published boiler designs (LBSC's TITFIELD THUNDERBOLT, don young's No.1 RAILMOTOR boiler, and don's HUNSLET boiler are extremely efficient boilers, though all quite different in their proportions and design).
i re-built an LBSC MAISEE without the combustion chamber. i can assure you it steamed as well if not better than any MAISEE built with the combustion chamber as per the book. this is rather an extreme example and probably had a bit to do with my setting of the valves and draughting arrangement too to maximise efficiency. ive built a few boilers to no published design, and when following a design have 'improved' upon things i consider to be not ok in my opinion. but then ive a few years of experience of driving and building these things under my belt!
the odd 1/4" on barrel diameter can cause the most awful problems with tube layout and clearances and water circulation.
cheers,
julian
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philh1
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Post by philh1 on Apr 3, 2013 20:30:11 GMT
Julian,
I very much appreciate your words of caution. Calculations will be prepared and checked before presenting the design to my club inspectors (all before cutting metal - as in the real world). If the design flops for some reason then it is only paper and a few hours of 'learning' rather than copper and silver solder. I might even post the design on here to see what people think.
PhilH
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peteh
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Post by peteh on Apr 7, 2013 9:46:10 GMT
Well it was a very bitty day today - had to take my daughter to a party around midday which broke the session in the workshop up. Just got the backhead and tubeplate both milled down to correct height and started on the throat plate flange - then realized that I had used 2.5mm and not 1.6mm copper.
I will probably make a new throat plate using the correct size material as otherwise I lose a mm from the firebox, and I imagine these small boilers need as much firebox as possible for best steaming, although 1mm isn't much at the end of the day. The other issue with the thicker plate is that the radius on the flanges is larger which looks a bit worse in my opinion.
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Post by doubletop on Apr 7, 2013 10:10:51 GMT
.............. then realized that I had used 2.5mm and not 1.6mm copper. In a purely selfish way I'm glad to hear that. When you said you were using 2.5mm I thought I'd stuffed up in some way and checked the drawings, then thought it must be one of the interpretations of the Oz rules vs the UK design. It won't take you long to wack up another plate in 1.6mm Pete |
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Post by Shawki Shlemon on Apr 7, 2013 10:34:42 GMT
Pete , it is easy to make the throat plate for round top boiler like this , 1- a piece of custom wood or something similar cut inside as in the simple picture , cut the plate oversize and form the the flange for the barrel . 2- on the front side of the back plate former bolt a disc same size as barrel , secure the new flange to the disc by a clamp . 3- using support or backing plat ( a piece of timber close to the back head shape of the bottom part and form the flanges for the back side of the throat plate . It is easier to make than to explain . Attachments:
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peteh
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Post by peteh on Apr 7, 2013 11:06:01 GMT
Thanks Shawki, that clarifies well how to do the job. Just have to wait until next weekend - I only really get Sundays to work iin the shed, and that's only when we are not at the club run days. Pete - Sorry to scare you |
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Post by Shawki Shlemon on Apr 8, 2013 8:21:50 GMT
Just in case the above attachment does not open . Attachments:
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peteh
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Post by peteh on Apr 14, 2013 12:09:15 GMT
Thanks to Shawki's excellent instructions - one double flanged throat plate ;D. Much easier to make than describe. Had to finish earlier than hoped today as Sister-in-law was over from Victoria, however her husband is a Ships Chief Engineer so we managed to talk of lathes and boilers while the girls (6 of them!) talked about 'other stuff' Attachments:
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