fang
Seasoned Member
Posts: 100
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Post by fang on Nov 24, 2014 20:06:25 GMT
Can anyone recommend a website or book that goes into how to calculate how much steam an engine needs, and how to work out the overall size, heating area, tubes etc of a boiler.
I have the Martin Evans book on boilers but it is more constructional rather than designing a boiler.
If there is a suitable book on building boilers that also goes through the design process then that would be ok.
Thanks
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Post by Deleted on Nov 24, 2014 20:29:56 GMT
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steam4ian
Elder Statesman
One good turn deserves another
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Post by steam4ian on Nov 24, 2014 21:09:09 GMT
Fang
I suggest you get in touch with Baggo on this forum.
he has some spreadsheets based on what he gleaned for various authoritative texts; these will allow you to determine grate area relative to cylinder and wheel size and the tube length/diameter and number of tubes plus other parameters.
He also has a spreadsheet about predicted water use which relates to operating pressure and other parameters; handy for sizing pumps and injectors.
Ian
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Post by Deleted on Nov 24, 2014 23:24:32 GMT
Interesting bit of obtuse information came out of that research >>ie K N Harris is KARL NOBLE HARRIS !..Now there's one for your club quiz nights !!
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Post by ettingtonliam on Nov 25, 2014 0:05:12 GMT
Indeed, and I've got a copy on my bookshelf, but never knew what the 'K.N.' (or Cayenne as LBSC was prone to call him) stood for. The only slight doubt I have about the book is that the information in it is now almost 50 years old, and, like some of LBSCs boiler stuff, may not be in accordance with modern thinking. Its interesting, but not surprising, that in his acknowledgements at the beginning of the book, he makes no reference to LBSC, who must have been the most prolific model boiler designer up to that time.
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Post by Deleted on Nov 25, 2014 16:37:19 GMT
He hated LBSC and all that he stood for !!..........I believe that "My little Cayenne" ( ie a hot, peppered reaction every time when he was in print) was of the opinion that there was only one type of model and that was as accurately produced as possible, with all t's crossed and all i's dotted !!...........Whereas Curly produced designs for the average "Blue-Collar" working man of the day ie}----- Affordable and basic locomotives with little or no frills at all, that could actually haul a person ( or two )....
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jma1009
Elder Statesman
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Post by jma1009 on Nov 25, 2014 17:28:32 GMT
john (baggo) knows my views on the boiler calcs formula he has on his excellent website, the formula coming from the late jim ewins. you can drive a coach and horses through the formula im afraid. i have always incorporated lots of jim's advice in my own locos and boilers, but the formula itself doesnt hold water.
i would say that generally if you copy a fullsize boiler in its proportions which is a proven good steamer it will also be a good steamer in miniature notwithstanding different tube sizes and layout and water spaces etc. if fang has a particular type of boiler in mind for a particular type of loco there is likely to already be a commercial design out there in miniature who's steaming qualities are well known.
K.N. Harris never built a miniature loco - and i would treat with a great deal of caution anything he wrote about miniature steam locomotives. the only good thing in his boiler book is the stuff about stress calculations, and an extremely good design of compact 'scale' water gauge that one of my locos is fitted with. i could re-tell lots of funny stories about K.N. Harris, but this is probably neither the time nor place!
cheers, julian
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Post by houstonceng on Nov 25, 2014 18:16:14 GMT
Oh go on Julian, tell us please. I like good bed-time stories, especially if they are funny (ha, ha rather than wierd).
I think Jim Ewin tried to create some of his formulae from reverse engineering good vs bad steaming models to arrive at grate area vs cylinder volumeand then added real formulea about tube length vs diameter based on known fluid flow parameters.
Problem I found with him during the very few discussion we had was that, sometimes, he was very helpful in explaining how to understand things and at other times, he might say, "work it out for yourself", without any hint of how to start doing so.
Members of my MES who knew him better said he was someone who, like K. N. H., had very set ideas and there were only two types.of people. Those who agreed with his thinking and those who were wrong.
Jim, according too e who knew him, went in for a medical operation that he really didn't need, because he knew better than the advice he was given- and it killed him. Don't shoot me for passing this on if you know better. I'm only quoting hearsay.
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Post by goldstar31 on Nov 25, 2014 19:49:25 GMT
I think that there is reference to the Battle of The Boilers here.
Should amuse those with hysterical perspirations.
Ooops
Norm
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fang
Seasoned Member
Posts: 100
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Post by fang on Nov 25, 2014 19:58:29 GMT
I have full size drawings for what I have in mind, and I want to scale that down for my model, but would like to do a few calculations to make sure the grate area is suitable for the heating area, and that the heating area is large enough compared to the grate area compared to the capacity of the boiler, etc. Also I need to work out how many and what size of tubes I need.
Sounds like the Harris book probably has this information it though
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jma1009
Elder Statesman
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Post by jma1009 on Nov 25, 2014 20:03:27 GMT
hi norman, im afraid the battle of the Boilers was between Bassett Lowke and LBSC (though later LBSC vented his spleen against Greenly who had designed Bassett Lowke's loco). K.N. Harris wasnt involved and really only came to prominence after WW2 when a stationary engine he'd rebuilt (not made!) gained a high award at one of the ME exhibitions. cheers, julian
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steam4ian
Elder Statesman
One good turn deserves another
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Post by steam4ian on Nov 25, 2014 20:39:44 GMT
I have full size drawings for what I have in mind, and I want to scale that down for my model, but would like to do a few calculations to make sure the grate area is suitable for the heating area, and that the heating area is large enough compared to the grate area compared to the capacity of the boiler, etc. Also I need to work out how many and what size of tubes I need. Sounds like the Harris book probably has this information it though The respected Julian doesn't like the formulae Baggo has used but unfortunately does not give an alternative except scale down the prototype except for this and except for that etc. Remember the cube and square powers muck up scaling of areas and volumes. In this vein Fang could look up old published Master Mechanics loco design data and other publications from the USA. What Baggo uses is at least a place to start. The tube data is based on established formulae. What ever you do make sure there is plenty of water and steam space over the firebox, remember the water surface area reduces with higher water levels in a round topped boiler. Consider the grades on the track you will be operating as a change from climbing to descending could move the water from the top nut to out of sight on the gauge if the freeboard is too tight. Ian
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Post by Deleted on Nov 25, 2014 21:20:38 GMT
To be fair, all I've done on the website is put down my thoughts etc. on Jim's calculations and developed a couple of spreadsheets to make the calculations easy to do. Jim's theories interest me so I did a bit of work on them. I've never said that this is THE way to design a boiler. Until someone comes up with something better though I'll stick with them. The whole point of designing Simply Longer is to design a boiler to Jim's 'specifications' and see how it compares to the standard Simplex boiler. Personally I think it will be a much better steamer but time will tell. I certainly don't think it will be a complete failure (fingers crossed!).
I must admit that there are certain aspects of boiler theory that I now don't think are important. For instance, I don't think the Keiller ratio for tubes (length versus diameter) really matters. The Keiller ratio was supposed to give the most efficient heat transfer for a given tube size but it's now pretty widely accepted that only the first few inches of the tube contribute anything to heat transfer and the rest just carries the waste gasses to the smokebox without doing a great deal else. Therefore the length probably doesn't really matter within reason.
My thoughts are now that there are only two important factors in a boiler - the boiler must have sufficient grate area to match the steam consumption of the cylinders and the tube area should be at least 12 - 15% of the grate area. The first (getting the grate area) is fairly easy to do but getting the tube area can be difficult, especially with a wide firebox boiler. It can be impossible to get the tube area anything like 12 - 15% of the grate area in that case unless you have a very large diameter barrel or fit a lot of very small diameter tubes. I've struggled with Simply Longer's boiler, which is a narrow firebox, and have had to resort to a taper barrel to get enough tubes in.
John
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jma1009
Elder Statesman
Posts: 5,896
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Post by jma1009 on Nov 25, 2014 21:50:11 GMT
hi john, my comments werent in anyway a criticism of your excellent website, merely that jim ewin's boiler formula doesnt come up to scratch. what jim was at the time particularly concerned with was to criticize the Greenly type boilers with 'lazy grates'. in this respect his formula works, but it doesnt take into account narrow gauge type boilers and also states that some extremely good boilers would be bad steamers, which is where his formula falls apart.
the keiller tube formula is very well established and i see no reason not to take account of it. it also has nothing to do with jim ewins. it stands to reason that the longer the tube the greater it'd diameter should be on a free steaming boiler.
what makes a good free steaming boiler is something im afraid you have to put down to experience. i dont like sloping grates, i adopt the high firebox crowns that jim ewins advocated, and if i ended up with a boiler of only 12-15% free gas flow through the tubes as a percentage of grate area i'd build something else!
cheers, julian
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Post by jordanleeds on Nov 25, 2014 22:30:10 GMT
The Book that Hagley has advocated whilst good really doesnt give best practice.. I suggest speaking to a proper boilersmith and any material you have Must be to the correct grade otherwise its no use and should not be used in the construction of a boiler or any form of pressure vessel
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jma1009
Elder Statesman
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Post by jma1009 on Nov 25, 2014 22:41:16 GMT
ok andy,
here's a few re K.N. Harris.
when i was quite small K.N. lived in the same village (Rustington, W. Sussex).
K.N. delighted in wearing the loudest suits and ties imaginable. the sort of thing a circus clown would wear! (i have quite a few photographic slides of K.N.)
he also delighted in his G & T - perhaps more than he ought to have inbibed!
for many years K.N. was President of the S.M.L.S. at Beech Hurst Haywards Heath (in the late 1960s and 1970s perhaps the leading club in the UK with the best track). part of this time Jim Ewins was Chairman. at one particularly awkward committee meeting when things werent going Jim's way, he threatened to resign as Chairman. K.N. immediately replied 'Jim, i accept your resignation!'. exit Jim Ewins from BeechHurst and the S.M.L.S. for evermore!
contrary to K.N.'s writings in ME he was extremely 'clubbable' and gregarious, and very popular amongst the S.M.L.S. membership.
cheers, julian
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Post by Deleted on Nov 25, 2014 23:03:20 GMT
Hello JORDAN LEEDS,...I didn't actually advocate either of those two books that I've shown links to----only suggested that he try them.......Agreed that KN Harris' book is probably showing it's age now, but that second book ( of which I have a copy) actually has various calculations given in it that FANG might find of use............JULIAN, in my copy of "The Standard Steam Locomotives of British Railways" ( Rodger P. Bradley..........Published by}--David & Charles) the following free area's to grate areas' are given as }------------ BRITS = 16.2%,..........9F = 13.6%, ......CLAN = 15.9%, ........The 4-6-0's....4MT = 14.2, ... 5MT = 15.9%, .............The 2-6-0's....2MT = 15.9%........3MT = 15.2%...... 4MT = 16.5% ................... "Cayenne" actually appeared on the front of The Model Engineer at one time ( Maybe the early '60's ??) wearing a loud sports jacket and darkened sunglasses.... and a scowl..Looking for all the world like the Headmaster we all knew and feared at some time or the other..
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jma1009
Elder Statesman
Posts: 5,896
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Post by jma1009 on Nov 25, 2014 23:20:10 GMT
hi alan, fullsize locos have higher gas velocities and proportionately higher blast velocities and vacuum in the smokebox. our miniatures need a higher free gas flow to be truly free steaming boilers without forcing the grate and having too high a back pressure! cheers, julian
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Post by Deleted on Nov 26, 2014 0:00:49 GMT
Now there's an interesting project that we on this forum could do as a "collective"...........From the model drawings we individually own just enter on here the model, tube diams. (and total No.) plus the grate size.........Popular designs such as Springbok and Speedy and Simplex might provide interesting data ??............I'll start a new thread headed}--- Flue-tube area / Grate Area
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Post by ettingtonliam on Nov 26, 2014 9:53:13 GMT
ok andy, here's a few re K.N. Harris. when i was quite small K.N. lived in the same village (Rustington, W. Sussex). K.N. delighted in wearing the loudest suits and ties imaginable. the sort of thing a circus clown would wear! (i have quite a few photographic slides of K.N.) he also delighted in his G & T - perhaps more than he ought to have inbibed! for many years K.N. was President of the S.M.L.S. at Beech Hurst Haywards Heath (in the late 1960s and 1970s perhaps the leading club in the UK with the best track). part of this time Jim Ewins was Chairman. at one particularly awkward committee meeting when things werent going Jim's way, he threatened to resign as Chairman. K.N. immediately replied 'Jim, i accept your resignation!'. exit Jim Ewins from BeechHurst and the S.M.L.S. for evermore! contrary to K.N.'s writings in ME he was extremely 'clubbable' and gregarious, and very popular amongst the S.M.L.S. membership. cheers, julian Without derailing this thread, can you tell us something of KN's background and interests, as I understand he wasn't a 'locomotive man' Did he actually build things himself, or just pontificate to others?
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