BOXHILL by Martin Evans

[Deleted]

Blimey !!------------ that image appeared on my screen like an old dial-up ones from years back...............

[jma1009]

i wasnt planning to do anything in the workshop this weekend but woke up early this am so fitted the silver solder rings to the R-H side stays and silver soldered up.

i'd made the R-H side foundation ring.

very important when fitting stays without the inner firebox doorplate fitted required when using propane that the final side to be silver soldered with the stays will fit both flanged plates still to be fitted. 10 thou too generous can be closed up but not the other way round.

anyway rather than a load of boring pics of what i did same as the L-H side last weekend here's the boiler fitted in the frames with both sides done.

cheers,
julian

[Deleted]

that looks very smart Julian.... I can picture the fittings on the backhead now:).... top stuff as per usual...

Pete

[jma1009]

that is very kind of you pete,

the backhead fittings are exercising the grey cells, as the fullsize backhead is quite spartan and plain. no manifold/turret. the martin evans manifold/turret is quite hedious and wont be copied! plus i have the additional problem of finding steam feeds for extras such as the steam brake and hydrostatic lubricator etc.. plus im fitting 2 water gauges. quite a lot to fit in in quite a small space and get all looking reasonably ok.

cheers,
julian

[Roger]

That looks like huge progress now I can see it in place. You must be really pleased with the way it's progressing. I can always send you a wake up call very early each morning if that will help...

[Jim]

Thanks Julian for going to the trouble of answering my query and posting a photo of your Sievert Torch.

The reason for asking in the first place was that I think it gives newcomers a better grasp of what is being done with what sort of equipment as well as how it's being done.
Your series of photos gives a very clear idea of how to build up a hearth to keep the heat concentrated on the task for the heat being supplied.
I think your post has done a lot to demystify boiler making for many on this site along with a clear picture of what joints and stays should look like when properly silvered and all in living colour.

Thanks again Julian.

Jim

[runner42]

Hi Julian,

continued to be impressed. I am amazed that you are able to achieve such silver soldering results with a propane only gas source and a relatively modest burner size which is rated at 43.5kW. I would have expected a 80kW burner would be required at least at the latter stages of assembly. Surely you must use an additional heat source as background heat? 

Not much more to do, soon be getting the boiler inspector to look at it and pressure testing? Good luck at that stage, though I am sure it will be a routine event.

Brian

[jma1009]

thanks jim and roger,

i should have added that as per shawki the foundation ring sections are cross hatched with the edge of a file. the file creates a raised section of a few thou (so preventing a tight fit), plus the filed 'grooves' allow the silver solder to flow through. also grooves around the hole for the single rivet hole. the rivet is closed up with a 'G' cramp as bashing it would disturb all the silver solder rings. the front end of the foundation ring sides fit into a small rebate cut into the flanges of the throatplate. this is a pet method of mine that i havent seen published before but which i can recommend.

im not really bothered about the odd run of silver solder. it all gets covered up with the boiler cleading. far better to be too generous with the silver solder plus quite difficult to get everything absolutely perfect with the torch blazing away and the rod or strip of silver solder rapidly diminishing and getting very hot on the hands even when held with pliers! i would rather apply too much than have to re-heat to re-do the odd bit - though this has been required on occasions (such as that L-H front foundation ring corner!).

anyway hopefully that's all the fiddly bits now done. the inner firebox doorplate is next and with a piece of thermalite cut to thickness inside the firebox it will be kept to the correct distance. i am always a bit nervous of the smokebox tubeplate slipping down when done as the boiler is 'up ended' for this, but never had one slip yet. ive an old wood saw i use for cutting thermalite blocks to size.

i must admit that so far this boiler has been a bit fiddly as ive tried to maximise the firebox grate area as much as possible which with the deep firebox has required some very careful fitting to get everything to fit between the frame stay behind the crank axle, and rear axleboxes. normally one has quite a bit of leeway - in this case im working to tolerances of 1/32" or 1/64".

cheers,
julian

[jma1009]

hi brian,

the club boiler inspector has inspected all bits so far! in the UK all stages now require inspection so that otherwise hidden joints can be inspected.

STEPNEY's boiler is quite small. i wouldnt think the DORIS boiler would require anymore heat. the trick is to contain heat on the bits that arent being silver soldered. the last boiler i did was quite a bit bigger and required quite a bit more heat containment which created sometimes uncomfortable heat throwback which made applying silver solder sometimes difficult. one can have too much heat, though in my case and personal experience i think it's more a case of judging how much time it takes to get the job up to heat before the flux ceases to be effective because it has got exhausted. 10 mins is ideal with thessco F or tenacity 4A. 15 mins perhaps max. if the job hasnt got hot enough by 15 mins then best to have a re-think!

cheers,
julian

[runner42]

Hi Julian,

thanks for the tip. Specifying a 15 min max time limit is a criterion well worth remembering, since as you say the flux becomes exhausted and beyond that your pushing the proverbial up hill. I shall keep that in the grey matter when starting the boiler.

Brian

[shooter]

Hi Julian,
Once again you have excelled in your boiler build. I have made a mental note of flux working times,I had not thought of this before.
I guess it's a case of "Read the instructions on the pot" before you start.
Very impressed with the standard of all your work, gives me something to aim for.

Cheers for now Steve.

[Deleted]

Looking great Julian!

I have sad news though, Stepney (the 4' 8 1/2" version) is now shed bound for the foreseeable.
In a recent steam test the old girls main steam pipe failed before reaching anywhere near full working pressure.
This wasn't surprising in as much as she has been living on borrowed time for far longer than we all thought she would for ages now, what with the patch on patch on patch cylinder block. The only surprise was that it wasn't said block which killed her.

Her future is now uncertain as new cylinders and a new boiler are needed amongst other things.

A sad day

[pault]

Very nice work Julian, looks like you better crack on so there is at least one Stepney running. I do have a slight soft spot for the Terriers although they are Southern. Probably due to being taken to the Bluebell in the late 60's early 70's and recognising Stepney from the Rev Awdry book “Stepney the Bluebell Engine”

Regards
Paul

[Jim]

May 4, 2014 23:46:25 GMT jma1009 said:

it's more a case of judging how much time it takes to get the job up to heat before the flux ceases to be effective because it has got exhausted. 10 mins is ideal with thessco F or tenacity 4A. 15 mins perhaps max. if the job hasnt got hot enough by 15 mins then best to have a re-think!

Hi Julian,

I think you've made an interesting point with regard the effective life of the flux when heating. In effect you are breaking the task up into how much can be done within a 10 to 15 minute time frame. Depending on the task, taking on too much means the the flux will have become ineffective by the time you have worked your way to the end point.

Jim

[Geoff]

Very neat job Julian! You must be well pleased with your progress.

[jma1009]

thanks for all the comments on the flux exhaustion time.

the 15 mins up to heat is what i would consider max, allowing a further 5-10mins(max) silver soldering time.

i tend to whack the heat up after the first 5 mins so get to heat within say 10 mins, then i tend to work extremely quickly and methodically doing the silver soldering in a few minutes.

another factor that helps is if the set up of the work contains the flux so that it doesnt run off and disappear. i tend to apply the flux the consistency of melted ice cream, but then allow to dry out a bit before heating up.

with the higher melting point stuff such as silverflo 24 completely different set ups and reduced timescales apply. the same would apply to silver soldering steel fabrications with lower melting point stuff such as easyflo or silverflo 55.

all of the above of course applies to propane, plus of course if the work is overheated locally (as might happen with oxy acetylene) again the flux is exhausted quicker.

i have never found applying 'fresh' flux to the job part way through satisfactory if what has already been applied looks like exhausted. occasionally ive got away with this with complicated steel fabrications, but not worth the risk of dirty joints with boiler work, bearing in mind that the copper is continuously oxidising.

thanks Ben re the news re the fullsize STEPNEY's withdrawal. as the boiler cert expires in april next year im not that surprised. i havent seen STEPNEY in steam since age of 4 when had my first ride on a preserved railway behind STEPNEY (1971). at least there is a new cylinder block waiting to be machined, and the IOWSR have shown how to get 2 new terrier boilers made! i have always considered STEPNEY on the Bluebell Railway to very special, so i hope a fund is started to get him/her back to tip top condition very soon!

cheers,
julian

[Deleted]

Unfortunately the new cylinder block halves were flogged to the Spa Valley for Sutton

Time will tell

Ben

[Geoff]

Oct 16, 2013 23:34:17 GMT jma1009 said:

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

Hi Julian,

I decided to go right back to the start of your thread and whilst it is very interesting, it is giving me a great deal of heartache because I see so many things that I should have done to improve on my build of the Maid of Kent, which is my first build! However, I don't intend getting too fussy so that I end up taking 20 or more years to finish the thing. I'm firmly of the mind that if it will serve its purpose, get it finished. If I decide later on to rebuild any part then I can do so then.

Back to the reason for this post.... I am at the stage of ordering my boiler materials, and you have reflected in this post and the one immediately before it, one of my concerns. I have to build to the Australian code of course and I will end up with thicker boiler material than that proposed by LBSC, and I will also make use of a double flange on the throatplate. Using thicker material isn't all pain because I will get away with fewer stays, of course, but it will tend to squeeze up the tubes too much. LBSC specified 15 x 7/16" tubes, and I may have to reduce this number somewhat, or reduce the tube size in order to maintain adequate clearance between the tubes. Are you able to explain the calculation for the free gas flow percentage please, or point me to some publication that will explain these calculations? Is it better to have fewer larger tubes? I will feel a lot happier knowing how the sums work rather than just accepting LBSCs tube layout, but I'm sure that the calculations can become very complex.

Thanks for your shared experience ... it makes a good read!
Cheers
Geoff

[ejparrott]

Not familiar with the design, but could you not increase the thickness of the barrel on the outside rather than the inside, then you wouldn't squash the tubes. May need to be rolled from plate of course.

[jma1009]

hi geoff,

the free gas flow percentage is very simple.

you work out the grate area, and then the area if the inside dia of the tubes, then divide the later by the former. for the purposes of the calculation i ignore the restriction imposed by the superheater elements. others treat the superheater flues as the same size as ordinary flues.

don young was very keen on the above percentage calculation and shortly before his death explained his reasoning in his magazine LLAS though i have sat with him whilst he did these calculations at breakneck speed on a calculator making it appear like a piece of wizardry! there is an allied effect on the size of the blast pipe nozzle.

so far as tube diameter is concerned there is another formula called the 'keiller proportion' which has been discussed on here many times previously.

after WW2 LBSC went a bit overboard on the number of superheater flues on his 5"g designs. however very many successful Maid of Kents have been built. the late percy wood's example won IMLEC at least once!

due to the keiller proportion calculation i would not reduce the diameter of the tubes on Maid of Kent below 7/16" dia. if 1/2" dia permits a better layout, with say 3 x 1" dia superheater flues then that would be worth considering.

some of martin evans' and LBSC's boiler designs have relatively low firebox crowns. this is another area of debate - the late jim ewins being very critical of low firebox crowns.

cheers,
julian