BOXHILL by Martin Evans

[jma1009]

another pic from today.

cheers,
julian

[Jim]

Great progress there Julian and as others have said you'll great pleasure once in steam and on the track.

Jim

[Deleted]

Looks like you have achieved a perfect fit there Julian... very nice..

Pete

[bhk]

Beautiful work there Julian, sheet metal work is something that eludes me!

[jma1009]

hi jim pete and bhk,

thanks for your kind comments.

i still havent remembered to take a pic when things are being heated up or bashed, but here's a pic of the nearly completed inner firebox flanged plates. the former was made out of thick plywood. i reckon ive got one more heat up annealing and bashing to finish. the radii of the top corners is quite small, and so to those who havent attempted making their own flanged plates before my own method is to add another piece of wood the outline of the finished plate to one side with the former on the otherside when belting in the vice. dont tap the copper - otherwise it work hardens quickly - belt it! for small radii i use the copper face (suitably filed nice and smooth) of a THOR raw hide and copper hammer, taking care to hit the root of the curve and not the edges, and a slight 'slide of the hammer' on the surface of the flanged plate with the hammer head seems to help too. the sharp curves produce a much longer length of copper even though the plates were hacksawed and filed to 3/8" beyond the edge of the former - this excess on the curves has to hacksawed off after say the 3rd annealing and bashing, and filled down again on further after further annealings and bashings as it aids production of the curved flange.

anyway nearly there! i always think the inner firebox flanged plates are the most difficult.

couldnt finish them this evening otherwise the neighbours might have complained as was getting late so tomorrow evening hopefully and they will be done.

by the way the 'cave' formed by the thermalite blocks underneath the top block in the pic is where the plates get put for annealing. a large bucket of water and tongs are nearby same!

cheers,
julian

[jma1009]

although i said the weighshaft just clears the boiler actually i meant to say its the top of the lifting links crossbar that just clears same.

incidentally the top of the double flanged throatplate is joggled to fit between the boiler barrel and outer wrapper. i also joggled the outer firebox wrapper a bit - which has had the added advantage of making the outer wrapper 3 7/8" wide whereas the barrel is 3 3/4" dia. this improves on the width of the 'legs' of the water space between outer and inner wrapper, and is not noticeable visually from the outside, and also helps the tube layout as by raising the firebox crown a small amount i can add an extra tube in the bottom row - which helps towards the free gas flow percentage i aim at on my locos. the extra tube actually improves the spacing of the other tubes quite a bit so i might have a little something extra in my boiler that might one day make STEPNEY another suitable loco of mine for IMLEC! time will tell! i have often found that by playing around with washers of the tube size on the former a better layout can be arrived at when compared to drawings - not that many of my locos have been built to published designs. ive also made allowance for increasing the inner firebox wrapper from 1/16" to 2mm/5/64" as i think 1/16" is too thin these days. when designed in 1963 martin evans was going through one of his 'experimental' how to simplify boiler design and construction phases. my own ME drawings show girder stays not attached to the outer wrapper- needless to say mine will be of traditional design attached to the outer wrapper.

i also add a small step in the throatplate flange to locate the sides of the foundation ring. ive done this lots of times and considerably aids fitting and locating of the sometimes troublesome foundation ring sides. all the flanges on mine are greater than the martin evans design.

the moral of some of this blurb and the blurb about the outer wrapper extension piece and strap is dont be a slave to the drawings - some very simple alterations will result in a boiler that is much easier to construct (if not to draw on paper) that has easier and less joints and is better and stronger in many ways.

cheers,
julian

[uuu]

I'm sure Julian meant to say it, so I'll add on his behalf - he can tell me off if he disagrees!

Of course, any "improvement" you make to a boiler design has to pass the scrutiny of your boiler inspector. So if you're not a slave to your drawings, best to check that you modifications are OK.

Wilf

[jma1009]

a bit of progress - here's the 2 inner firebox flanged plates after drilling the tube and superheater flue holes the other evening. flanges are quite a bit deeper than the BOXHILL design plus i managed to get an extra 2 tubes in to help with the free gas flow percentage as a proportion of grate area that i try to aim for. normally i hate drilling and making the holes in the plates but as STEPNEY's boiler is the smallest ive made with only 3/8" dia and 3/4" dia holes it didnt take long. by re-arranging the tubes ive managed to avoid any tubes in line with the blast pipe which will help tube cleaning, plus the 2 middle columns of tubes are 'marine type' square grid pattern which apparently aids water circulation.


the superheater flue holes were done by drilling a pilot 1/4" dia hole for a special 3/4" dia counterbore/pin drill type cutter i had. on previous boilers they have all had 1" dia superheater flues and have required laborious chain drilling and filing to a gauge.

im quite pleased with the tube layout. it is very difficult for a designer to draw these things out on paper, and often very easy improvements can be made to the tube layout simply by using washers of the correct diameter and then marking the centers in pencil on the finished copper plate and centre popping same for drilling - which needless to say is what i did on this occasion.

cheers,
julian

[jma1009]

by way of comparison, here's the martin evans tube layout, so a bit of jiggling produced what i think is a much better tube layout. plus 2 more tubes. the free gas flow percentage of grate area is only 15% on the original design, whereas mine is 19%. this is still a bit below what i usually aim for.



cheers,
julian

[jma1009]

i made the gordon smith 'squat' safety valve yesterday evening and tested and modified same this evening - see seperate thread

modeleng.proboards.com/thread/8634/stepney-terrier-gordon-smith-safety

cheers,
julian

[Deleted]

nice work Julian...

Pete

[jma1009]

ive started making the outer dome, having already made the inner dome bush and flange out of PB1. as i want to make the inner dome as high as possible (hence the gordon smith 'squat' safety valve) i had a rummage in my shed for some odds and ends, and this is the result so far



can anyone guess what the top part is made of?

cheers,
julian

[RGR 60130]

Oct 23, 2013 11:00:53 GMT jma1009 said:

can anyone guess what the top part is made of?

cheers,
julian

Something pre-war Ann Summers?

[JDEng]

Bell out of a clock?

John.

[shooter]

Bicycle bell?

[jma1009]

none of you (particularly RGR 60130) anywhere near!

[JDEng]

Signal box block bell?

J.

[jma1009]

a bit of a clue - the snooker ball turned out to be exactly the right diameter to form the top half to the right size.

[jma1009]

a pic of the nearly completed fabricated outer dome. all made out of odds and ends in the scrap and junk box and saved quite a bit on buying a casting. as the top part is only some 1/32" thick also helps get a bit more steam space in the inner dome, and less likely hood of the safety valve lifting water as its inside the outer dome. i will finish off the outer dome when cleading is fitted - at the moment it allows me to size up the inner dome plus bush (already turned up with inner dome flange) which will be the next job on the boiler after doing the throatplate. normally i wouldnt bother with the outer dome till much later on, but STEPNEY is a bit unusual in this respect as you need to know what the outer dome fit is like to make the inner dome as generous as possible!



cheers.
julian

[bhk]

Looks excellent Julian!