BOXHILL by Martin Evans

[jma1009]

thanks bhk!

like most domes the terrier dome seems to look quite different in photos compared to when measured up and examined!

BTW the top part of the dome is an old brass door knob retrieved from a skip many years ago that has been in my junk box for ages. parted it in half with a clock makers gravel in the lathe then reformed to a slightly smaller radius with the aid of the snooker ball after annealing carefully. the £20 plus VAT and postage and packing saved on buying a casting will go towards some more silver solder for the boiler!

cheers,
julian

[ejparrott]

How you getting on with the new silver solder? I used some of the E2 equivilant the other day on some brake bits for my friends 9F, couldn't get it to flow quite as well as I'm used to...

[jma1009]

a bit more progress,

double flanged throatplate silver soldered to the barrel etc and you can also see the strap on the right hand side for the outer firebox extension piece. all done in silverflo 24 which having got the hang of it now is very good but does require a lot of heat ie glowing pink copper but its not a big boiler so no problems with propane. silverflo 24 doesnt produce the neatest of joints especially with an unsteady hand, but im not bothered about that. im more interested in good sound joints than a bit of silver solder in the wrong place. managed quite a nice fillet on the throatplate joint which also penetrated fully inside. the stronger more aggresive and longer lasting thessco F flux i always use for boilers is a must for this kind of work, and after pickling after brazing up, i use sodium hydroxide dissolved in hot water (available from wilkos at £2.50 a bottle). this loosens the otherwise rock hard deposits of flux. took 15 mins start to finish to do the above throatplate joint whilst listening to The Goon Show on Radio 4 ex yesterday evening!

i added the front part of the foundation ring with sifbronze to the throatplate before doing the above as is my usual practce.

silverflo 24 is 740-800 degrees Celsius
sifbronze 875-895 degrees Celsius

cheers,
julian

[jma1009]

btw the front part of the foundation ring is cut from 1/4" copper plate (did the rear part of the foundation ring at the same time), then milled to size with a section milled out to fit the inner firebox flanged plates. this avoids a lot of otherwise tricky work on the foundation ring later on. the sides of the foundation ring can be made as straight sections fitted into steps in the flanges of the throatplate and backhead, the steps being flush with the front and back foundation ring pieces and so avoiding the use of additional rivets (which i abhor and try and avoid in boiler work) and stop the sides of the foundation ring slipping down. i also find that fitting the front part of the foundation ring at this early stage aids considerably assembly of the inner firebox.
cheers,
julian

[Jim]

Hi Julian,

I've been following your boiler build with keen interest and I must add it's been spurring me on to get back to mine now the nice weather is back.
Your comments on the sequence of fitting and fixing the foundation ring was reassuring as it was something I had contemplated doing.

A quick question, from what you've said you use only propane for heating along with a big torch similar to the Sievert 2944?

Boiler making is a 'black art' for those of us venturing down that path for the first time, especially if there's no one near by to call on for a demo of how it's done hence the value of your comments and photos.

Cheers

Jim

[jma1009]

hi jim,

many thanks for your kind comments.

ive only ever used propane. i dont have the skill or equipment to do oxy acetylene, and ive heard and seen too many horrors of localised heating, cracked joints, and burnt copper.

my largest burner is sievert 2938.

i dont think boiler work should be too daunting. all the rules are very well known. i spend far more time thinking about how im going to do something than actually doing it! i think about how im going to get at the joint and where the heat will go and will spend ages arranging and re-arrranging my thermalite blocks till im happy with a particular set up.

anyway STEPNEY's boiler is quite a simple small boiler.

as commented previously a bit of thought in my case resulted in the double flanged throatplate and only one extension piece to the right hand side of the outer firebox wrapper with the strap on the outside so less joints to do and less things to go wrong plus a stronger construction where also in the case of the strap to the extension piece it is outside so inspection of the completed joint is easy and it doesnt block up the water space or cause problems fitting the throatplate or backhead or foundation ring sides as per the original design.

cheers,
julian

[Deleted]

very neat work Julian, that joint around the throat plate looks superb and the parts fit perfectly... very nice.

Pete

[Jim]

Thanks Julian. From what you say I'm on the right track, just need to keep going and keep my vivid imagination re all the things that can go wrong, under strict control.

Jim

[cplmickey]

Nov 1, 2013 11:54:34 GMT jma1009 said:

hi jim,

i dont think boiler work should be too daunting. all the rules are very well known. i spend far more time thinking about how im going to do something than actually doing it! i think about how im going to get at the joint and where the heat will go and will spend ages arranging and re-arrranging my thermalite blocks till im happy with a particular set up.

I agree - preparation is the key. Holding the parts is one of the important things to consider in my opinion as clamps can move or open up when heated, or indeed a clamp can exert pressure on a joint and not allow the solder to flow through. This is where I usually need advice or sometimes reassurance I'm doing it right, before putting the torch to the work. I didn't have any problems with my smaller boilers but the bigger ones are obviously heavier and the solutions need to be well thought out.

[jma1009]

hi ed,

i didnt understand your reference to E2! never heard of it! silverflo 24 is the sort of equivalent to B6. there doesnt seem to be anything equivalent to C4 these days.

i carefully chain drilled and filed to size the hole for the dome bush today. im going to make the regulator body first before fitting the dome bush as i want the dome bush to accurately locate and hold the regulator body.

cheers,
julian

[ejparrott]

Easyflo 2..... Silverflo 55 is the equivalent is it not?

[jma1009]

hi ed,

ive never had a problem with silverflo 55. ive used the RN equivalent for many years. i prefer it on boiler work. i would suggest using a stronger flux than the easyflo flux such as my thessco F or tenacity 4A. i dont know why you should have had a problem with it. ive used non - cadmium stuff for many years for boiler work.

i dont think the easyflo flux is suitable for steel and is suitable for small jobs in brass or jewelry. although ive a large tub of it ive never used it in model engineering work. alec farmer of Reeves fame told me to use thessco F when i started this lark many moons ago and that's what ive used ever since, including small fiddly boiler fittings.

cheer,
julian

[ejparrott]

Interesting, I tried Thesco F years ago, couldn't get that to work either! I think I might still have some, whether its any good after three house moves is anoither thing...I'll perhaps try that with Silverflo55

[jma1009]

hi ed,

easyflo 2 is 608 degrees melting point. easyflo is about 620 off the top of my head. easyflo flux will just cope with both but probably more suitable for easyflo 2 and non - ferrous stuff where a less active flux is required. others far more knowledgeable than me will be able to comment, but my understanding of easyflo flux was it was designed for very short heat operations using easyflo 2/easyflo and is easily removable. boiler work doesnt satisfy this criteria, and in any event silverflo 55 is 630 degrees celsius melting point which i think especially for ferrous work makes easyflo flux quite iffy as a flux. something more active is required such as thessco F or tenacity 4A.

incidentally after pickling the above throatplate joint etc in sulphuric acid i then left the boiler in a solution of sodium hydroxide (wilkinson's sell it as caustic soda drain cleaner at £2.50 a bottle) to soften the thesco F flux as it goes glass hard after the sort of temp required for silverflo 24 though remains very active for the higher temperature range.

cheers,
julian

[jma1009]

anyway, when ive finished making the regulator body (nearly finished this weekend) the next job is the inner dome bush. a pic is attached - the pic of the regulator fabrication came out blurred. another alec farmer of Reeves fame tip was just to machine a small rebate off the dome bush just sufficient to locate it. the dome flange holes are blind. i also remove part of the bush on the inside between the holes so the steam space isnt reduced by the depth of the flange - just a few slots within a 1/16" of the inside of the boiler shell is sufficient if this makes sense. there is usually a bit of distortion of the dome flange after silver soldering so it will need truing up flat on top when the boiler is finished - dont assume it will stay flat and as turned in the lathe! PB1 used for the dome bush. never use free cutting PB which has lead added. the stuff i bought is cored PB1 which saves a lot of work and also works out considerably less than buying castings for such bits.

cheers,
julian

[jma1009]

ive done the inner dome bush this evening. im afraid some of the pics didnt come out too well and are a bit blurred. anyway pics 1 (outside) and 2 (inside) show the silverflo 24 joint of same to the boiler barrel and inside showing a nice fillet and penetration all round. inner dome bushes are a bit of a problem - they are one of the most structurally important joints being usually only butt joints with the boiler shell and in a position where strength to the barrel is vitally important. also getting same level before silver soldering can be a problem - my own well tried method is to chain drill and file the hole to suit the bush, then centre pop the boiler shell about 1/32" away from the joint at an angle to close up the joint and hold the dome inner bush tight once set level but still allowing the silver solder to penetrate all round. this has worked for me but others may have better methods. i always think that a decent fillet is required on the inner dome bush. on the second pic you can see the cut out i made for the regulator body to locate into, and the cut outs to aid the steam space - which in STEPNEY's case might get used for 2 internal steam pipes for the injector steam valves as on fullsize these are located just rear of the dome on top of the barrel. incidentally i wont allow the sulphuric acid pickle in my pickling tank to get at the inner dome flange during further braze ups and pickling.

i worked out what ended up as quite a complicated set of steps on the inner dome flange and fabricated regulator body so that the screws securing the regulator body to the boiler shell dont take the force of the screwing up hard of the internal regulator steam pipe. one advantage of making the regulator body and trial fitting same at quite an early stage. i dont really like the Stroudley type regulator, but as it's a Stroudley loco i couldnt really dispense with same! anyway trial fitting of the fabricated regulator body is shown in pic 4.

by way of contrast i have added a 3rd pic showing the inner dome silver soldered together. the top part was done with silverflo 24 and has a nice generous fillet inside (not shown). i then did the flange to inner dome with silverflo 55 and you can see how nicely this flows forming the sort of joint you would expect of easyflo, but in my case using thessco F flux. after doing silverflo 24 the silverflo 55 was a joy!

cheers,
julian

[jma1009]

a rear view of the trial fitting of the fabricated regulator body with the inner dome showing how it all fits together in steps. i think fabricated regulator bodies are much easier to make and get dead on to size and square and machine etc. castings are a pain for such parts!



cheers,
julian

[uuu]

That all looks very splendid.

Wilf

[jma1009]

i finished the inner dome this evening. made a hole in the top for the safety valve bush then turned up a bush turned out of a small slice of the right thickness of hard drawn phosphor bronze tapped 1/2" x 26 tpi for the safety valve i'd already made. had forgotten quite how hard it is to make stuff out of hard drawn phos bronze! would have been easier had i turned it out of a bigger longer bar. easy to bore and turn but a devil to drill and tap! took ages! however i do like using up odds and ends of stuff in my bronze 'oddy' box, and hard drawn phos bronze is difficult to get these days. if accurately made the threads are very resiliant and tough. i make all my threaded boiler bushes out of hard drawn phos bronze. i never use gunmetal or cast phos bronze. then silver soldered it with easyflo to the already made inner dome. added some flux to the silverflo 55 joint on the flange just in case it got a bit too hot lower down but no problems. then turned the bottom of the inner dome flange flush to remove any excess silver solder and copper from the inner dome tube beneath the bottom of the PB1 flange.

then did a trial assembly of the inner dome with the outer dome with safety valve fitted and also added the cab to the boiler for the first time. slowly looking like a terrier instead of just a chassis! the inner dome fits very nicely on the inner dome bush so no distortion occured when silver soldering same to the barrel, though it will get checked with engineers blue in due course.

the sorting out of the dome at this stage is crucial as it should be in line with the driving wheel centres on the A1X terrier design. seem to have got it 'spot on'. normally i wouldnt bother so much with the dome at quite an early stage in the boiler making. also i wanted to know that the safety valve i'd made to gordon smith's design would fit the outer dome!

will add a few pics tomorrow to show.

cheers,
julian

[jma1009]

just a couple of extra pics...

the inner steam dome has 1/4" more steam space than the BOXHILL design. now that the boiler shell is done and the cab fitted around it im cracking on with the reach rod to finish the valve gear. as my reverser is fitted to the left hand front cab box as per fullsize the reason for making the cab at an early stage will be apparent. there will probably be a lull in boiler work whilst i finish the reach rod and do all sorts of unfinished jobs on the chassis such as the working leaf springs. not the ideal time in the UK to do boiler work anyway as i leave the workshop door open whilst brazing stuff up - and to put it mildly it's been rather cold here in south wales the last few weeks!
cheers,
julian