BOXHILL by Martin Evans

[Deleted]

very impressive Julian....very nice indeed..

Pete

[jma1009]

hi roger, steve and pete,
you are all far too kind. it's quite a simple small boiler, and if i can make one (incorporating what i hope are a few improvements along the way to the original design) then ANYONE CAN. this is the smallest boiler ive made to date. i reckon this boiler will cost me £250-300 inc all silver solder, copper and bronze for bushes etc. i think that pete's silver soldering of his steel fabricated components for his DONCASTER far more complicated and taxing than silver soldering copper. in fact with this boiler it should get easier as it gets assembled and put together as im finding the bits heat up and get a bit too hot at the moment - i havent quite got round to adjusting my 'technique' for a smaller boiler.
a taper barreled belpaire firebox boiler (roger and steve) is quite a different proposition, as would be pete's DONCASTER boiler if pete incorporates the as designed semi combustion chamber (which pete and i have discussed privately at some length). i am afraid these days i choose a loco to build based on factors such as no piston valves, and ease of building the boiler. ive enough grey hairs and bald patch as it is! ive done one GWR tapered boiler with belpaire firebox. i dont think i want to do anymore of that type!
cheers,
julian

[Roger]

Well, it's a big unknown for me, and I trust your judgement on how easy it is or not. We'll see when I get to that point. I'm not overly worried about creating the copper shapes, making formers for the flanges and doing those is something I'm looking forward to. I'm much more concerned about getting the Silver Soldering right. You make it seem very straightforward. but I bet I'll struggle to begin with. I may have to get someone to supervise me the first time to get me on the right track.

[jma1009]

hi roger,
i suppose silver soldering is one of those things that just requires adherence to a few simple rules, plus an element of judgement. the first silver soldering i did (for quite a few years till i obtained my sievert equipment) was with paraffin blowlamps up to ex WD 1 gallon size. quite a flame thrower!! i still remember the first silver soldering i ever attempted which was to my SR cap badge where the copper split pin for the locating pin behind the greasetop hat band had broken off. i think the next job was a new pressure cooker top for my mum's pressure cooker which had got mangled down the waste disposal unit. i always remember the first job i did silver soldering on my first loco - i'd made an error and machined too much off one of the axleboxes and silver soldered a plate on top. this would be when i was 16. i silver soldered up the first of the steam chests fabricated out of brass and bronze as couldnt afford the steam chest castings. a friend wanted to have a go at doing the second one himself and though far more experienced than me at my the age of 16 he managed to melt the whole lot! i wasnt a happy bunny! and those were the days of easyflo at 608 degrees celcius!
i remember the first joint on my first boiler (5"g RAILMOTOR). double flanged throatplate to barrel and separate outer wrapper. added quite a few rivets to hold all together. the joints were perfect! took it along to the saturday afternoon club meet for inspection and was told i would have to reheat it all again and re-do as hadnt silver soldered the rivets. that sort of started a long standing hate of rivets in boiler work! plus a strong reminder not to forget things! i should add that no where in Don Young's description of making the boiler did he mention that all rivets had to be silver soldered!
cheers,
julian

[Roger]

Hi Julian,
It will certainly be another useful tool in the box when I become competent at it. I think the overheating bit is my biggest worry, especially when it's a more complex shape and not all of it is in view. I'll just have to be cautious. I see where you get your hatred of rivets from, and I can see why you didn't think they needed attention. At least the job was a success in the end.
I bought that Australian Copper Boiler building code and found it very interesting. I'll revisit that and the UK code when I get back to the boiler re-design later.

[jma1009]

i was hoping to be able report major progress with the boiler this weekend, but alas no! a new part arrived to replace a badly corroded part on the lounge solid fuel stove, so spent the weekend removing corrosion and rust from same and the offending old part, and then climbing up on the roof to fit a cowl to the chimney pot to prevent corrosion happening again.
at least it was coal fuelled related!
cheers,
julian

[jma1009]

ive been a bit waylaid the last few weeks doing repair jobs on the house,

but eventually have re-started work on the boiler for STEPNEY. i touched up the areas i'd missed/werent up to my liking on the girder stays of the inner firebox on saturday. this evening ive drilled all the holes for the throatplate stays and outer wrapper stays and check valve bushes on the sides of the boiler.

i also turned up the firehole door ring. chucking same in the 3-jaw has always produced disastrous results, so for the last few boilers ive made a mandrel in the lathe out of 1.250" dia brass to press the firehole ring material over to turn down the shoulders. this takes all the worry out of what is otherwise a rather difficult turning operation. in due course the firehole ring will get annealed and formed into an 'oblong' as per fullsize and brazed to the inner firebox doorplate with high melting point stuff with the stays added at the same time. first time ive used the lathe in ages!

the tubes are ready for fitting to the inner firebox but awaiting some silverflo 55 wire for same from Macc Models that i ordered today. ive plenty of easyflo 2 wire but seems a bit pointless to use it on the tubes as precludes doing other bits with silverflo 55 rod, plus as no longer obtainable i want to save the easyflo 2 for boiler fittings etc.

cheers,
julian

[Roger]

I look forward to seeing pictures of your progress. I'm a big fan of mandrels and fixtures, in fact anything that takes little effort but makes life easier. Copper is a nightmare to machine at the best of times so I can see why you're doing that.
I'm just planning how to make the buffer bodies and heads for SPEEDY and concluded that a couple of simple mandrels will make life so much easier. I rather enjoy the planning stage these days, it means when I go to do the job it's all down in drawings and notes and I can just crack on with it.

[jma1009]

hi roger,

digi camera battery flat so have to wait till same re-charged!

i also hate turning copper.

most of the descriptions of boiler making in copper say fit wooden bungs in the ends of the barrel tube and turn the ends. these days with accurately cut tube from our ME suppliers this rather pointless and difficult job is no longer required.

ive got to machine up some hard drawn phos bronze bushes for the fittings very shortly. this is always a pain like copper. what i usually do is turn down with a parting tool leaving a shoulder on the end facing the tailstock, the parting tool being used to turn down to dia for the holes in the boiler. then drill through and tap the regulation 3 tapered threads as a start, then part off. chucking the parted off bush then trying to tap same is frought with disaster. i only ever use hard drawn phos bronze for boiler fitting bushes.

i dont make many mandrels and fixtures but having had one copper firehole ring whizz out of the chuck once it is one case where i think a mandrel is very advisable!

cheers,
julian

[sncf141r]

Hi Julian;

Read a message on a previous page about rod stays. What's your take on them? I did not really get a positive or negative feeling reading the comment.

My take - rod stays, easy as cake - at least from the boilers I've done - much prefer them over flanged plates on the crown sheet, etc.

Last boiler I did was for a 3-1/2" gauge 2MT locomotive (2-6-0, martin evans design) and, after putting it together had 1 weep, fire hole door. After re-soldering that, it held pressure and has been passed by our club.

That's boiler #4; #3 (A Kozo Shay) was also fairly easy; boiler #2, a Tich boiler, was 11 hours in the making, boiler #1, a Tich boiler, a couple of months, finally got it to hold, but decided to scrap it, which is where #2 came from!

I've got another one to do this summer - a 7-1/4" "Rocket" style locomotive, so should not be too bad. Rod stays in this one, too.

Over here, I solder outside, but outside is still covered in snow, although it's no longer neck deep! Give it a week or two, and I'll be able to see the back yard.

I, actually, really like building boilers; lots of fun.

(edit - put a picture of the latest boiler, on my blog: cnc-for-model-engineers.blogspot.com )

John.

[jma1009]

hi john,
until STEPNEY's boiler which has a curved top to the inner wrapper ive only done bigger boilers with flat tops and no problem making the girder stays which ive previously made as per alec farmer's advice to fabricate them. with STEPNEY's boiler i decided to flange up the girder stays and i must admit they are a pain flanged up and im still faffing about with them to get a decent fit so that inordinate amounts of silver solder arent required to fix same to the outer wrapper.
as i dont have any experience of rod stays i cant really comment, though i know that generally a stiffner plate is required to be silver soldered to the inner wrapper.
so long as the fit is ok to the outer wrapper, ive never had a problem silver soldering the girder stays to same of LBSC type. ive never needed rivets for same to the outer wrapper doing everything upside down with a few heavy insulating blocks inside the firebox to hold everything together, and heat from outside (underneath). i do the front foundation ring to tubeplate , and throatplate stays at the same time.
what of course is vital is that the outer wrapper to girder stays should be adequately and properly silver soldered. this is i think where many fail, due to wrong set up, inadequate heat and inadequate amount of silver solder, and poor fit of the parts. i am always 'over generous' with the silver solder so dont expect my boilers to look like commercially made ones with precise neat joints with no excess or runs!
however i can see where rod stays avoid many of these problems and might be easier.
cheers,
julian

[Roger]

Apr 7, 2014 22:58:31 GMT jma1009 said:

hi roger,

digi camera battery flat so have to wait till same re-charged!

i also hate turning copper.

most of the descriptions of boiler making in copper say fit wooden bungs in the ends of the barrel tube and turn the ends. these days with accurately cut tube from our ME suppliers this rather pointless and difficult job is no longer required.

ive got to machine up some hard drawn phos bronze bushes for the fittings very shortly. this is always a pain like copper. what i usually do is turn down with a parting tool leaving a shoulder on the end facing the tailstock, the parting tool being used to turn down to dia for the holes in the boiler. then drill through and tap the regulation 3 tapered threads as a start, then part off. chucking the parted off bush then trying to tap same is frought with disaster. i only ever use hard drawn phos bronze for boiler fitting bushes.

i dont make many mandrels and fixtures but having had one copper firehole ring whizz out of the chuck once it is one case where i think a mandrel is very advisable!

cheers,
julian

I've not had the dubious pleasure of turning Phosphor Bronze yet, there's something to look forward to. You mention Tapered Threads..... what are those for?
I'm going to use the CNC mill to turn to profile on the fronts and rears of the buffer heads and it's easier to do that as the last operation since holding  them by the finished buffer head isn't that satisfactory. I'll ream the hole for the spring and take care to make the OD accurate so that I can fit them onto an extension that will go into the ER32 collet. It'll probably take half an hour to make the extension but the job then becomes dead easy.

[ejparrott]

Rod stays are the preferred method now, having spoken to RSA about boiler design approval recently he told me in no uncertain terms not to use them. I've never had to use a thickener plate, but the boilers I've built have had 1/8" wrappers anyways. I thought there was something about crown stays in the green book but a quick glance couldn't find it. Where it's found on published designs of courses its still allowed - well, there;s no rule against it so it is allowed, just RSA didn't want me using them.

[jma1009]

at last some further progress... ive silver soldered the tubes into the inner fiebox. ive seen all sorts of ways of doing this - including one row of tubes at a time. however the LBSC method works for me and is also ideal with propane ie making rings of silver solder wire to slip over the ends of the tubes and slide down to the water space side of the firebox tubeplate, flux up both sides, then heat from inside the firebox. in about 10 minutes the whole lot gets hot enough for the silver solder to flash through and around each joint with no fuss.

what takes the time is getting the smokebox tubeplate on all the tubes to hold everything together, making the rings and making sure they are all in position, and fluxing everything up thoroughly (which can only be done when you know the rings are in position as otherwise the flux obscures where the rings are).

i made up the rings with silverflo 55 wire from Macc Models.



the 3rd pic above is immediately after the heat up showing how little is required in the way of heat containment with thermalite blocks on such a small boiler.

cheers,
julian

[Roger]

Lovely job Julian,you've made that look very easy.

[jma1009]

hi roger,
thanks!
preparation is the key.
here's another pic which shows some unusual tools. the large taper reamers are very useful for getting exactly the right fit for the tubes in the tubeplates for the silver solder, and the dentist's probe is by far the most useful tool in boilermaking in my humble equipment for removing tough bits of flux and cleaning up all sorts of nooks and crannies. also in the same pic is the firehole ring material turned down each end. i only took a 1/64" off the OD. the end that goes through the backhead is much longer than required at this stage to act as a heat sink.

cheers,
julian

[jma1009]

a much better pic (larger) of the inner firebox showing the silver solder round the tubes is here

www.model-engineer.co.uk/sites/7/images/member_albums/84404/511509.jpg

no silver solder was applied from the inside, just heat drawing the silver solder through the tubeplate. also guarantees that the silver solder will only melt when the copper has got to the correct temperature. no 'turning down' of tube ends, just a generous 2 thou fit. martin evans used to specify at the time BOXHILL was described (1963/4) a tight fit of the tubes but this is quite wrong as prevents the silver solder flowing through and round the joint.

cheers,
julian

[Deleted]

Very nice Julian! Looking forward to more!
Ben

[Roger]

I can see how you can be completely confident that it's all sound when you see the Silver Solder wick through like that. I'd best make a few notes.

[ejparrott]

For your notes Roger, you need quite a lot of microns clearance, otherwise the silver solder won't flow through.