Speedy Boiler

[Roger FroudParticipant @rogerfroud48738]

Thanks, I'd only glanced down the list without realising that there are many sheets! I've got it now, It's interesting that it's got one of the highest ratios of tube cross section to firebox grate area of all the locomotives. It backs up what Julian is saying that there's far more tube area than is really necessary and losing tubes of changing the layout entirely might be a good option.

I'd like to take 1/4" off the outside diameter for choice so there's room for some lagging without making an oversize smokebox. Changing the tube layout would make that a lot easier to achieve.

[Roger FroudParticipant @rogerfroud48738]

I'm not sure why the superheater tubes are treated as if they have the same cross sectional area as a single small flue though, The figure I get for the free gas flow using the actual area of the 5 superheater tubes is 29%, a long way from the 19% if you work it out the other way. I'm not sure what any of this reveals to be honest, but then I don't know anything about the subject. There are such huge variations in the figures and of course I don't know which ones steamed well and which ones had issues. It looks like you can get away with murder and it will still work, that's the only conclusion I can come to as a total outsider.

[John BaguleyParticipant @johnbaguley78655]

Hi Roger,

Don't forget that the superheater flues are partially obstructed by the superheater elements so the free gas area will be the area of the tube less the area of the superheater elements. Jim Ewins made the assumption that the resulting area would be similar to that of the firetubes so I've done the same. This isn't 100% accurate but could be worked out easily with an addition to the spreadsheet. I had been thinking of doing that actually and probably will at some point.

I think it was C M Keiller who said something like ' The problem with steam locos is that no matter how badly designed they are or how badly made they will still work' I would add' after a fashion'!

John

[Roger FroudParticipant @rogerfroud48738]

That's fair comment, and I think the ten percent difference between our two figures is indicative of the scale of the problem. Anyone who's studied the science of flow in pipes will know that the diameter and the length of the pipe has a huge bearing on the flow rate through it, never mind what happens when you partially obstruct it.

If you gave any of these designs to an F1 test team, I bet they could model the gas flow for a variety of pressure drops across the flues and do the same for the water turning into steam in the boiler. They have the Finite Element Analysis tools to model what happens over aerodynamic surfaces cooling passages in the water jackets in the engines. There's no mystery as to how to solve these problems but sadly I don't have access to these tools, and wouldn't know how to apply them even if I did.

Julian has sent me some pictures of a boiler that has very few tubes indeed, only 12 in a boiler for the same size locomotive as Speedy. Instinct tells me that it's not enough, knowing what everyone else seems to think is necessary, yet is works very well indeed. I think any attempt to use arbitrary rules of thumb is futile because the governing factors in the design are just not represented by those figures. It's a fascinating spreadsheet though, and I think its main value is in debunking these rules of thumb rather than reinforcing them.

[julian atkinsParticipant @julianatkins58923]

to avoid anyone jumping to the conclusion i make boilers with far too few tubes i should add that the boiler roger refers to is a 5"g round top boiler of 5" dia so less than the area available for a scale SPEEDY boiler at the firebox tubeplate end, the loco with the same design of boiler came 3rd in IMLEC in 1995 so im quite happy with the internal arrangement, being very well proven, and had a free gas flow percentage of grate area of 25%. that being said there is considerable scope for improvement on the original SPEEDY boiler both in terms of scale (the LBSC design being considerably over scale and too big in diameter and firebox dimensions, and the backhead arrangement for the fittings is atrocious and nothing like scale) and IMHO in terms of internal layout. the fullsize boiler was a GWR No.10 boiler being a shortened version of the standard GWR No. 2 boiler using the same flanging blocks.

cheers,

julian

[Scott MatthewParticipant @scottmatthew23893]

Providing efficient steam heating is very easy and will give you hassle-free operation. Steam heat can easily be one of the most efficient and comfortable ways for you to heat your home. The efficiency and comfort of the system are totally dependent upon the quality of your installation or repair.

((link removed. Didn’t work anyway))

Edited By Diane Carney on 25/11/2013 13:05:14

[Roger Gray 2Participant @rogergray2]

Hi fizzy. I may well have a speedy boiler for sale. I have just had new stays fitted to the firebox crown which was very satisfactory done. However now discovered that superheater tubes leaking as a result of heat from tig welding stays. I have to make decipher, do I keep spending money with a company to continue repairs or call it quits and go for new boiler. I do not have gas and air brazing equipment so rely on company to do it so costing me good money. It is a cracking boiler in every spence apart from superheater tubes. Which need replacing. If you have gear or know someone who has then straightforward but tricky job. You have to silver solder the tubes without upsetting neighbouring tubes. Depends on how skilled you are.

roger g

[Roger Gray 2Participant @rogergray2]

To add to my last post. The superheater element design is crazy. the block on the end of the element tubes virtually block the main superheater tubes. My main tubes were totally blocked with soot over the years which had set like concrete. These superheaters have not worked for years. Added to this the elements cannot be removed without knocking them out. Hence the damage to the SH flues. I will replace element that have spear tipped end therefore will not block flues and can get a flue brush throu easliy.

[julian atkinsParticipant @julianatkins58923]

hi roger gray2

leaking superheater flues on an old boiler? not a 'cracking boiler' in my book! not for re-sale either other than to the scrapman. you should get £40 for it scrap.

if your club boiler inspector reads your posts he wont be very happy.

there is nothing wrong with LBSC's return bend design on SPEEDY unless you made the blocks oversize. you should have bought a smaller flue brush and regularly kept them clean. in 1" flues there is ample space around well made return bends to sweep the flues and keep them clean.

no sympathy whatsoever im afraid.

cheers,

julian

[Roger Gray 2Participant @rogergray2]

Yeah you are quite right Julian. The history is that I brought the engine from a friend knowing that it had dodgy boiler. He let someone else drive who ran low on water and damaged the crown stays. I had the successfully replaced by a well known boiler manufacturing company. Unfortunately, on test it was found that all the SH tubes leaked. It is not sure why this happened however in order to remove the SH element I had to tap it out. This may have caused the damage however for the engine to operate well and efficiently the had to come out regardless. One point you make is that you imply that the SH tubes are 1 inch dia. Mine are 3/4 inch hence the SH element turn round block was rock solid in the tube and had to be tapped out. However there we go, I have ordered a new boiler. One point , as an engineer I believe everything is repairable, although no necessarily economically so. If I had the right equip, I would have done it. I have a bit of experience, built a LNER A1, long case clock ( completely from scratch) , traction engine from scratch and 3 full size aircraft that I flew for many years, the last being an all Ali 150 mph cracker. However thanks for reply

regards. Roger gray

[julian atkinsParticipant @julianatkins58923]

hi roger gray,

i was very sorry to have been the omen of bad news, but it is extremely difficult to repair old boilers, let along new ones with defects. no point beating about the bush with these things im afraid. your SPEEDY loco boiler obviously wasnt built to the drawings hence the variation in the superheater flue tube diameter.

TIG welding of boilers as a repair is very dodgy unless you know exactly what type of copper the boiler was made from – it should be de-oxidised copper. i am not surprised that other leaks developed, and in fact may have developed anyway and not be related to the TIG welding.

glad to hear you have ordered a new boiler. they arent too difficult to make IMHO, though not cheap, but considerable less costly than a commercially made boiler. hope you get the loco running again soon.

cheers,

julian

[nigel jones 5Participant @nigeljones5]

Hi Julian. I dont find it any more difficult to repair an old boiler than I do a new one, provided that the correct materials were used in the first place. I completely second your points on TIG repairs. Whilst the tubes will most likely be deoxy the tube plate almost certainly wont be. Much of the comments and advice on here seem to be from second hand sources, but I can say from first hand experience that TIG welding deoxy copper causes lots of tiny stress fractures – some are big enough to be clearly heard going snap as the weld cools.

[Roger Gray 2Participant @rogergray2]

Hi Julian. Saw speedy drawing yesterday when ordered new boiler. Interestingly the SH tubes are 3/4 inch, 5 off. If yours has 1 inch tubes it is not made to drawing. Further you would not get 5 SH 1 inch tubes in unless you have left out the top row of fire tubes. Even then it would be a squeeze. So with 20 gauge tubes a 3/4 X 3/8 superheater return block would just fit in hightwise with about .020 thou clearance and width wise about 1/8 clearance. Still think crazy design. My SH haven't worked for years totally blocked . I shall put in stainless dart ended tubes reaching right across the firebox. Should get new boiler in about 6 months time. Meanwhile doing rest up and repainting. Looking good.

regards. Roger gray

[Roger Gray 2Participant @rogergray2]

Sorry to hog the board but can I ask opinions on firebox fuse able plugs. Ie copper rivet soft soldered into bush in roof. If my boiler had had a plug it would still be going now. Seems to be difference of opinions in my club but I thought were standard safety practice.

[duncan webster 1Participant @duncanwebster1]

I can thoroughly recommend the Australian Model Boiler Code as a design guide. It is very well written, and complies with BS5500 (Unfired fusion welded Pressure Vessels), which is as near as British Standards gets to what we make.

Ignore all the rubbish quoted by 'those who know' about loco fireboxes being banned. Unfortunately I can't remember the e-mail of the chap I got my copy from, and it's no doubt out of date by now.

[nigel jones 5Participant @nigeljones5]

my above post should read that non deoxy copper cracks! With regard to fused plugs, cant remember why but im sure there is some additional complication to getting a club cert if it has one. I wouldnt build a copper boiler without one as I am far too absent minded to trust myself with good water levels!

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