Keiller Proportions.

[ejparrott]

I've had a day off work today, using up my holiday allocation, with the sole purpose of completing the boiler design for my Manning Wardle.

Some time back the Keiller Proportions were disucssed in another threadhere

Kt = L/d²

Where L is the length of the tube, d is the bore of the tube, and CMK recommended KT to be 65-70 and Jim Ewins 80 (Thanks Julian!)

I've just run the Milner Hunslet boiler through it, which is the basis of my boiler being slightly shorter and narrower, and get an answer of 53.19 - below what CMK suggests, and well below what JE says, and yet I understand these are excellent steamers. There's another modified hunslet boiler running at Rugby now, and that seems to steam well.

I'm just redoing my tube layout for the third time, having got a figure well over a hundred! Current figure is 72, with Ø3/4" x 18swg tubes 30 7/8" long, just above CMK, so hopefully ok, doesn't warrant another redesign I don't think!

[jma1009]

hi ed,

my own view is that boiler tubes should be relatively large in diameter verses length so stick with a proven boiler design that is an excellent steamer. for example have a look at Don Young's No.1 RAILMOTOR boiler (ME 1968) which has 7/16" dia tubes and 1" dia superheater flues on a very short barrel. i can vouch that this boiler is an excellent steamer! the free gas flow area as a precentage of grate area is 35%! generally the narrow gauge locos with a wide firebox are also excellent because more tubes can be fitted into the boiler (eg the HUNSLET quarry tanks in various gauges, and my own 3.5"g ffestiniog railway LINDA). this aids the free gas flow percentage.

i thought when i replied in the thread you quoted that jim ewins advocated a larger diameter tube to length ratio to C.M. Keiler but a bit of maths on my part subsequntly proved this wrong - this may be an error on jim's part on the paper i have (jim's 80 indicates a smaller diameter tube to length ratio) as he certainly did advocate larger diameter tubes from other papers i have unpublished after his death, and he also advocated a much higher firebox crown than martin evans etc. some of jim's formulae must be treated with a degree of caution - many of the boilers he described as being 'poor steamers' such as the RAILMOTOR boiler proved to be quite the opposite.

i think we both have enough experience between us to know what makes a good boiler - just beware of the people who say 'so and so' boiler is ok when in fact experience driving same shows it to be far from the case!

i would endorse your thoughts re building a copper boiler for your Manning Wardle. the initail higher cost is far outweighed by the superior performance and longevity and increase in the value of the completed loco.

cheers,
julian

[ejparrott]

I haven't yet worked out my grate area, its about 8" square IIRC....... Just checked, its 7.5" long and 8.75 wide.

I've stuck with the same tubes as the Milner Hunslet boiler, .75 diameter and 18swg, but that boiler isn't superheated, and I've chosen 1.5" for those. I've gone for 28 fire tubes and four superheater flues. There are 20 tubes in the Hunslet boiler.

I initially drew up the copper boiler but then dismissed it on grounds of cost, that was 8 or 10 years ago when I first started design work, so I did start working up a steel boiler. That sort of stalled when my adopted Uncle's Romulus boiler needed replacing after 25 years, despite having a 'gentle' life, always being treated and always blown down, even with a heater in the firebox over winter to keep it all dry. It got me thinking then that I'd be looking at a new boiler at least once in my life time, especially as I intend to work this engine harder than that
Romulus has ever.

So copper won again. Did all the design work yesterday (basically stretching the Hunslet boiler and closing up the stays for the uprated pressure), woke up this morning and realised I'd forgotten a feed for the steam brake, and all it needs now is dimensioning and handing over to another boiler inspector for checking before I go and see a man about making it. I've decided this one is beyond me, I've not got access to big rolls or oxy any more, and the barrel alone is 8.5" x 32".....

[jma1009]

hi ed,
im sure you could borrow the equipment required. incidentally ive watched a mate of mine form the curved steel sides to the bunker (or whatever you call it) for a Marshall tractor in fullsize using a very large propane torch - sort of thing the SVR use for heating up copper sheet for flanging. just an enlarged version of our sievert stuff.
cheers,
julian