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Speedy Boiler

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fizzy12/03/2013 22:15:31
1734 forum posts
116 photos

Anyone got formers for this, or even better one for sale? I simply cant afford to buy a commercially made item.

DMB12/03/2013 22:39:50
1016 forum posts


beware, if you make a Speedy boiler. One of the members @ my club was building one and showed us all a small problem. He said there was insufficient clearance between the undersides of the bottom row of flues and the throatplate flange. He had filed small scallops of metal from the flange to accomodate those boiler tubes. Obviously, I do not know if he had followed the drawing exactly, as he said he had or if he made a small error of which he was unaware or if drawing was at fault. All I`m saying is just be aware and check very carefully. Godd luck.


fizzy13/03/2013 00:26:31
1734 forum posts
116 photos

thanks John

DMB13/03/2013 08:05:38
1016 forum posts

Hi Fizzy,

Whoops! Just had a look this morning + notice I failed to proof - read my rotten typing last night. That was meant to be................good luck!

1. Speedy boiler builder now dead so cannot question him further.

2. As far as I know, it was his first attempt @ boiler building + therefore relying on experienced club member boiler makers rather than own experience. What I saw of his work, it was good.

You just need to be very careful in cross-checking dimensions on any drawings. Worthing club members did a joint effort build club loco - "Nigel Gresley"(?) design by late Martin Evans and they had long conversations about how certain parts fitted together.


Stub Mandrel15/03/2013 10:54:47
4311 forum posts
291 photos
1 articles

I have heard that the tube spacing for some of Curly's boilers was 'optimistic'.


Chris15/03/2013 11:22:08
87 forum posts
13 photos

I know what you mean about buying a boiler. I find myself in the same position.

I may be saying the obvious but are you aware that your boiler inspector will need to see your work at several points throughout the build. Best to check with your club inspectors from the start of the project. Also many older drawings are out of date in the size of materials and in some cases even type of material. Again you inspectors will correct and update for you.

Best of luck. Chris.

DMB15/03/2013 11:46:54
1016 forum posts


LBSC/Curly had a favourite expression; "it steams like a Witch." Perhaps its not surprising with the number of tubes he would cram into his boilers. But then look at full size, with something like 240 tubes! Viewing smokebox interiors reveals a certain cramming effect in FS.


Stub Mandrel15/03/2013 21:45:37
4311 forum posts
291 photos
1 articles

Funnily enough I was gazing into the depths of a FS smokebox this morning - more or less. A couple of rather sorry boilers at the Ruddington Workshops at the top end of the Grand Central Railway. Only the cafe open But a good chat about full size steam, watching the engines from Barry Yard top the huill in front of our house when I was a boy and big plate of egg, chips and beans.

They've got a Ruston diesel, full size, about as big as a Luton van!

The Nottingham SMEE have a mighty fine track too anyone from there on here, so to speak?


craig fowler21/03/2013 10:39:01
16 forum posts
Im sorry if this turns into another thread about the policies on boilers!!!!!! But is it true that inspectors wont even consider a boiler unless its a published design?

The problem ive got is that ive designed an engine myself (a freelance generic design) and so ive designed the boiler myself.
jason moore 121/03/2013 16:03:20
21 forum posts


Some will, some won't. If your design is so near to an existing design that it makes little difference you might get around it that way.

Some inspectors will give your design a fair chance,wanting to see drawings and calculations if you've gone for something a bit different, otherwise if fairly run of the mill you may be OK simply by quoting good examples of the sizes and thicknesses of material etc used in existing designs.

Some i am afraid though will only consider published designs.There is only one way to find out for sure and that is to ask.

fizzy21/03/2013 18:32:13
1734 forum posts
116 photos

There should be no reason for a competent boiler inspector to fail a design unless it has not been designed properly, and if he is not competent then he shouldnt be in that position. My way has been to read the blue/green book thoroughly and talk through the deisgn with the inspector first. I then draw it in a CAD program - this is especialy useful as you will be stunned at how many alterations and revisions you go through from first plan to completion. i then print it full size from every projection and section. By now, as part of the design process you will have done your sums - again, go through these with the inspector before finishing the design. I include the calculations as a footer on the drawing. If you follow every step by the book there should be no reasonable grounds to refuse your plans. Ive recently completed a steel/copper 5" to my own designin. Not welded by a coded welder (although I used to be so at least all the prep work and welds were correct), I have material certs for all the steel and have had the boiler welds proffesionally tested and certified. Absolutely no issue with getting a ticket for it. Communication with the inspector is essential at all stages. PM me if you need any help.

David Jupp21/03/2013 19:05:28
751 forum posts
17 photos

May be worth noting that in industrial pressure equipment practice, the Design Verification Engineer and the Inspector are likely to different individuals with quite different qualifications/experience.

A Design Verification Engineer can check that the Designer has used a sensible approach or complied with a recognised code. The Inspector will check that the finished item matches the (verified) design. I would not necessarily expect either to be competent to do the job of the other.

craig fowler21/03/2013 19:42:40
16 forum posts
Cheers dudes.... I'l ask my local inspector.

I cant see any problems with my design though.

Looking at the original post, seems like there are errors with published designs anyway
David Jupp22/03/2013 07:57:11
751 forum posts
17 photos
Posted by craig fowler on 21/03/2013 19:42:40:

I cant see any problems with my design though.

Typically it is all to easy to overlook something in your own work (not that I'm suggesting you have) - that is the main reason for independent verification of designs.

fizzy22/03/2013 21:08:13
1734 forum posts
116 photos

I have to admit that I made very many small but critical design changes before I got it right. In the end I was asked to put in firebox stays which were not needed "to keep others happy". I bit my bottom lp and conformed!

Niloch22/03/2013 23:31:03
371 forum posts
Posted by craig fowler on 21/03/2013 10:39:01:

The problem ive got is that ive designed an engine myself (a freelance generic design) and so ive designed the boiler myself.

The best article I've ever read about boiler design is entitled Safety of Copper Boilers by Kozo Hiraoka, I suspect it has appeared in several publications including his book Building the New Shay:


In the above book it extends to nine pages with graphs for:

(1) Minimum staybolt diameters;

(2) Maximum allowable pitch of symmetrically arranged staybolts;

(3) Minimum thickness for a cylindrical shell under internal pressure; etc. etc.

In terms of authorship per se, never mind the subject of the book, I suspect those familiar with Hiraoka's books might concur that they are amongst the best ever produced for the model engineer. The quantity, clarity and the draughtsmanship of his drawings/illustrations are a revelation.

It has to be said that his paper has been produced to meet American Society of Mechanical Engineers codes/regulations but I would find it very difficult to understand why a British boiler tester would fail a boiler produced to the exacting ASME standards.

The book is expensive so I would suggest a visit to your local public library.

julian atkins23/03/2013 11:29:55
1235 forum posts
353 photos

hi craig,

there are indeed lots of well known designs for miniature loco boilers which have errors. both PANSY and SPEEDY have quite a large unstayed/unsupported area on the backhead/inner firebox doorplate above the firehole door which is unsupported, and i dont think many club boiler inspectors would be happy these days with a new boiler built to old drawings with fittings screwed in to boiler plates instead of proper bronze bushes silver soldered in place. martin evans had a thing about curving the inner firebox wrapper and dispensing with crown stays that connected with the outer firebox wrapper, and using quite thin copper sheet for the inner wrapper. most builders of LBSC's BRITANNIA boiler have a problem with the throatplate which is very badly designed. martin evans also uses quite a large pitch for boiler stays using larger diameter stays which i have always thought suspect. the well known commercial builders rectify these errors as a matter of course.

a completely new design will need the 'theory' provided with calculations etc. the standard ME formulae is in martin evans' book 'model locomotive boilers' and K.N. Harris' book. a variation of a 'standard' design probably wont require this data if the only differences are to barrel length and firebox length and tube diameter and long as you can provide the drawings and references for the 'standard' boiler. however a lot will depend on how well the club boiler inspector knows you and how high he regards your workmanship and experience.



robert mort15/06/2013 21:54:07
18 forum posts
4 photos

Posted by julian atkins on 23/03/2013 11:29:55:

a completely new design will need the 'theory' provided with calculations etc. the standard ME formulae is in martin evans' book 'model locomotive boilers'

Martin Evans book does not contain any formula on unsupported boiler areas that I can see. It only has one formula that refers to pitch of stays limited by the strength of the stays only, and independent of sheet thickness.

I'd be interested to see a calculation of max unsupported area.

Edited By robert mort on 15/06/2013 21:54:31

Speedy Builder516/06/2013 07:18:50
2111 forum posts
146 photos

You may be interested in the attached photos, I am sure the owner of them would not mind me publishing them here. The new stays were placed here by a boiler manufacturer.



A really nice job !


DMB16/06/2013 12:26:43
1016 forum posts

Thats a nice touch - bush stamped with thread used - no guessing etc

Edited By DMB on 16/06/2013 12:27:05

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