jma1009
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Post by jma1009 on Jun 28, 2011 16:40:51 GMT
thank you Albert for your advice re grate area.
my reasoning is that 1. i cant stand sloping grates, and 2. as the boilers on the fullsize locos were excellently proportioned and excellent steamers and are full depth in front of the rear axle, there shouldnt be any need to extend the firebox over the rear axle as per BOXHILL. 3. Don Young didnt extend the firebox when designing his 7 1/4" gauge NEWPORT, despite having proportionately bigger cylinders than BOXHILL.
i have done my free gas flow calculations and they work out ok with the smaller grate. a friend of mine has a 3 1/2"g LSWR Adams '02' using a Rob Roy boiler, and cylinders about the same size as BOXHILL and it steams wonderfully without the fire being too fierce and forming clinker. too big a grate can lead to a lazy fire, and the free gas flow figure for BOXHILL is quite low. by fitting a backhead with a large radius to the flange (as per prototype) i can get a grate area of 8.25 square inches, as opposed to 9.97 square inches on martin evan's boiler design, and thats with me increasing the foundation ring width from 1/4" to 5/16" too. needless to say i dont like martin evan's BOXHILL boiler design at all! even the firehole door is the wrong shape for a TERRIER!
or am i missing something?
cheers, julian
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Oct 3, 2013 21:42:05 GMT
hi pete,
thank you for your kind comments.
i enjoy boiler making! there is something strangely satisfying about making things in copper! my motto is plenty of heat, plenty of the right type of firebricks, plenty of the right type of flux, keep everything scrupulously clean when doing the joints, and dont worry about the cost of silver solder! i need a few more materials - as long as they arrive on time it shouldnt take longer than 6 weeks of spare time including flanging all the plates. that's considerably less than it took to make the cab! ive got all the silver solder and 3/32" plate, and foundation ring material, bronze for all the dome bush and other bushes, and firehole ring material. just the 3mm plate on order for the backhead and smokebox tubeplate, and the fluetubes.
i bought £125 of silver solder from cupalloys a few years ago just before the cadmium stuff became unavailable (equivalent of easyflo 2), plus have a stock of same. i like to do the dome bush, throatplate, and a few other joints with other higher melting point stuff first ie silverflo 24, and get on very well with the silverflo 55 (non-cadmium silver solder a bit higher melting point than ordinary easyflo) which i use for boiler work as the equivalent of easyflo. i use easyflo 2 for the tubes and foundation ring and backhead. ive always used Thessco F flux for boiler work as recommended to me by alec farmer of Reeves fame many years ago. though my first boiler was done throughout in easyflo 2 and the first few joints done with a 1 gallon paraffin blowlamp before i acquired my seivert torch.
anyway as summer is over the neighbours wont complain about me bashing copper over the formers!
ive never driven a miniature terrier, so will be quite fun to see how my own terrier boiler performs in due course.
cheers, julian
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jma1009
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Posts: 5,901
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Post by jma1009 on Apr 7, 2014 22:17:07 GMT
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
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jma1009
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Post by jma1009 on Apr 7, 2014 22:58:31 GMT
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
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Post by Roger on Apr 8, 2014 6:57:29 GMT
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.
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jma1009
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Posts: 5,901
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Post by jma1009 on Apr 9, 2014 18:09:19 GMT
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
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jma1009
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Post by jma1009 on Apr 29, 2014 22:07:11 GMT
a bit out of sequence, but when the side stays to both sides of the firebox are silver soldered with propane the inner firebox doorplate (left off to silver solder the side stays) then needs fitting and silver soldering in position. the inner firebox doorplate to backhead stays and firehole ring can be silver soldered to the inner firebox doorplate at the sametime, but i prefer to fit them beforehand with high melting point stuff... so here's a pic of the inner firebox doorplate with the stays and firehole 'ring' trial fitted. i silver soldered them in position with silverflo 24 a short while ago and it is still soaking in sodium hydroxide solution at the moment after pickling and scrubbing. the stays (i decided to fit 15, far more than the meagre 8 on BOXHILL) are turned from 3/16" dia hard drawn phos bronze, turned down each end to automatically provide a spacer for the backhead when fitted in due course, and taped 5/32" x 40 tpi for the inner firebox doorplate, and centred and turned down 5/32" dia the other end. the top 3 stays are tapped 8BA for fitting the scale tray above the firehole that i propose to fit, and to which the firehole door assembly will also be fixed. cheers, julian
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jma1009
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Posts: 5,901
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Post by jma1009 on Apr 30, 2014 22:46:56 GMT
this might get a bit boring, but here's the inner firebox doorplate silver soldered with the stays to the backhead and firehole ring etc. i ran silverflo 55 over the silverflo 24 joints just to tidy things up a bit . silverflo 24 isnt the easiest thing to use for 'fine' assemblies. incidentally the centred holes in the ends of the stays are very important as a guide when opening up the holes in the backhead so that everything lines up. getting the holes in the backhead for the firehole ring and stay ends is a bit of guess work and careful fitting etc. it is always the way with the firehole ring to backhead, but the stays are an added complication and extra work. cheers, julian
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jma1009
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Post by jma1009 on May 8, 2014 22:35:35 GMT
i drilled the holes for the stays in the backhead yesterday evening (carefully!) as the stays have to be silver soldered already to the inner firebox doorplate for propane (see pics 30th april) hopefully the need for the centres in the end will become apparent. you drill undersize first to see if the centres are central in the drilled hole and draw over if required. i got 10 out of the 15 spot on, with the remaining 5 needing just a little bit of drawing over. then opened out to No.22 for the 5/32" dia stay ends. they will get opened out to No.21 before silver soldering the backhead plus countersinking. exactly the same as fitting the firehole ring to the backhead, just more work involved and careful 'fitting'. might get the inner firebox doorplate silver soldered to the inner firebox this weekend if i have time. i would like to fit a scale Stroudley type firehole door which is quite a fiendish and fiddly device in miniature. it is a flap that opens inwards into the firebox hinged at the top, similar to the Webb firehole door. i might have a slight deviation and have a go at making a trial one out of brass to see if it is workable in miniature, before progressing further with silver soldering on the boiler. the Stroudley firehole door was quite a feature of the fullsize locos. i have never seen a working 5"g version before! cheers, julian
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jma1009
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Post by jma1009 on May 18, 2014 22:07:45 GMT
i silver soldered the inner firebox doorplate in position this afternoon in not ideal strong sunlight. all went ok so another awkward bit done on the boiler.
only 2 major heat ups left assuming all goes to plan ie smokebox to barrel and ends of tubes etc, and backhead to outer wrapper, last bit of the foundation ring and firehole ring to backhead joints. i will fix as many other bits such as bushes and flanges to these sub assemblies beforehand with silverflo 24.
ive got to cut out the rear foundation ring from 1/4" thick copper plate, and make quite a few flanged bushes and smaller bushes first.
ive also got to make 2 top elbows for the water gauges. i havent made and fitted water gauge elbows for over 20 years so will have to try and remember how to do them!
cheers, julian
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