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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Post by runner42 on May 8, 2014 23:29:41 GMT
Hi Julian,
Great work. Help me to understand the drilling of backhead for the stays a little better. Did you mark out the backhead as close as possible to were the stays should be and then drill through with a small drill say 1/16" and then positioned the backhead in the boiler resting on the stays and then drill a little through the already drilled holes to see where the holes appear on the stays. If they were central OK if off a little open the drill hole with a small file and then put a slightly larger drill through the backhead and again see where the new hole appeared on the stays. Hopefully this time central and then drill all the holes the size of the stays?
If so what a great method of getting it right.
Brian
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Geoff
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Post by Geoff on May 8, 2014 23:32:25 GMT
Thanks for your succinct explanation of the gas flow percentage, Julian. I think I'll shift any further discussion on this to the boiler discussion page ... which is probably where I should have made my query in the first place!
Your backhead looks very tidy. I must say, your boiler fabrication sequence seems a lot more practical than to complete the whole inner firebox first, and I will certainly consider using this method - and will consider raising the firebox crown as well.
Cheers
Geoff
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jma1009
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Post by jma1009 on May 8, 2014 23:39:48 GMT
hi brian,
almost!
yes very carefully marked out and measured, then drilled the backhead 3mm first. it is also important to check the fit of both together when fitted to the boiler. any discrepancy is easily seen due to the centred ends in the stays (which are only shallow, and apart from the top 3 stays which will have 8BA studs fixed to them for the firebox tray, will get filed nearly flush after silver soldering).
for the marking out my dental probe was used to scribe round the stays where they abutted against the backhead when all fitted to the boiler. the scribing isnt 100% accurate and then carefully measured and adjusted before centre popping and drilling.
cheers,
julian
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jma1009
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Post by jma1009 on May 8, 2014 23:49:20 GMT
hi geoff,
i am pleased the stuff on free gas flow percentage etc was interesting. sometimes it just isnt possible to fit the size of tube one would like. for example my first boiler was a No.1 Railmotor boiler which had 7/16" dia tubes and quite a bit shorter than BOXHILL, and considerably shorter than Maid of Kent, and as i knew this boiler was very free steaming i originally schemed out (or tried to) a BOXHILL firebox with 7/16" dia ordinary tubes but it simply wouldnt work so fitted 3/8" dia tubes as per the original design, though by a few tricks managed to fit in 2 extra ordinary tubes and also avoid any being in line with the blast pipe that would have made cleaning of the central tubes very difficult on a short smokebox with a high blast pipe. the marine grid pattern on mine is supposed to promote better water circulation anyway.
the previous boiler i built has a barrel length similar to Maid of Kent but is fitted with 1/2" dia ordinary tubes and 3 x 1" superheater flues. i knew this boiler was also very free steaming as the loco fitted with the same arrangement came 3rd in IMLEC!
the Railmotor No.1 boiler has a free gas flow percentage of 35% and the above boiler referred to has a free gas flow percentage of 25%. i try to aim for as near as 25% as is possible and practical. not always possible particularly on a tapered boiler barrel. don young's 5"g BLACK FIVE boiler is a good example (rare for don) where the free gas flow percentage is quite a bit lower.
cheers,
julian
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Geoff
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Post by Geoff on May 10, 2014 0:36:20 GMT
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. Hmmm. you may be right ... but the problem is with the belpaire wrap not the barrel. i probably need to lift the belpaire wrap anway to allow a flange on the outside of the barrel. The restriction really happens on the firebox tube plate when changing the firebox wrapper to 3mm and trying not to decrease the size of the water jacket. I may take a look at Julian's suggestion of raising the firebox crown a tad, and trying 1/2" tubes. Back to the drawing board. |
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Geoff
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Post by Geoff on May 13, 2014 2:22:49 GMT
I'm thinking of putting the firebox tube-plate to the wrapper on Lion with high temp stuff, and then drilling the tube holes after...not made my mind up yet. Did you in fact do this? How did it work out? I'm thinking of doing the same thing after seeing Julian's comments. Geoff |
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Geoff
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Post by Geoff on May 13, 2014 5:22:45 GMT
hi roger, both really. ive sort of done a variation of the original martin evans design that i dont particularly approve of. this is the first boiler ive done with 'webbed feet' crown girder stays as per martin evans. they are bit of a pain as the inner firebox is slightly curved whereas all the ones ive done till now have had flat topped inner fireboxes. i should have been a bit more generous with the silver solder this eve. the original advantage of the 'webbed feet' design claimed by martin evans was to give better water circulation. i added some additional circulation holes further up as you can see which isnt on the design but doesnt compromise the strength of the stays. i added heat underneath from inside the firebox and this is quite sufficient. when the tops of the stays get silver soldered to the outer firebox wrapper the heat will be whacked up and directed from the outside. you wont have any problems with SPEEDY's boiler as it has a flat topped inner wrapper and flat topped outer wrapper so a piece of cake! unless you decide to fit rod stays. cheers, julian Hi Julian, You didn't say in your description, whether you used Silverflo 24 or 55 for the Crownstays to Firebox join. I'm really interested to know how much care has to be taken not to mess up earlier joints made with lower temp solder on subsequent work. Cheers Geoff |
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Post by ejparrott on May 13, 2014 8:33:24 GMT
I'm thinking of putting the firebox tube-plate to the wrapper on Lion with high temp stuff, and then drilling the tube holes after...not made my mind up yet. Did you in fact do this? How did it work out? I'm thinking of doing the same thing after seeing Julian's comments. Geoff I haven't done it yet, I've a few jobs that need doing in the workshop before I can start the refit. At the moment I'm refurbishing my Boxford lathe and there's bits of that all over the workshop! Once I get sorted out I'll take the Lion down there and start work. I still think it's probably what I'll do. If I don't do that, then I'll assemble the tubeplate and tubes with hi temp stuff. |
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jma1009
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Post by jma1009 on May 13, 2014 10:39:52 GMT
hi geoff,
the crownstays to inner firebox wrapper were done with silverflo 55.
as there is usually quite a few years between making boilers i make notes as i go along and then write up a summary for future reference and 'aide memoire'. i have a note on the previous boiler construction summary 'dont worry about previous joints melting -it didnt happen!' however just as a precaution i flux everything up anyway and make sure everything is clean beforehand.
you have the advantage in still being able to get easyflo 2 'down under'.
cheers,
julian
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Post by Deleted on May 13, 2014 11:06:11 GMT
Hi JULIAN-------- Just out of interest sake, I hope you don't mind me adding this in ?? Here are some extracts from my R & D work on The Bear's Boiler calculations.......In order to get an initial idea I looked at BR Standard Boilers with similar overall dimensions..Thus the 9F and Britannia then slightly smaller with the 4-6-0's and finally the 2-6-0's just for comparison.............Having done all the number crunching etc. I came up with the Main Flues, the Small Flues and then the % grate area for No111........As you can see it came out at 17.74% which I think is satisfactory.........The blast pipe, regulator, main steam pipe were then calculated in a similar manner  --------------  ----------------  |
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Geoff
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Post by Geoff on May 13, 2014 22:35:33 GMT
hi geoff, the crownstays to inner firebox wrapper were done with silverflo 55. as there is usually quite a few years between making boilers i make notes as i go along and then write up a summary for future reference and 'aide memoire'. i have a note on the previous boiler construction summary 'dont worry about previous joints melting -it didnt happen!' however just as a precaution i flux everything up anyway and make sure everything is clean beforehand. you have the advantage in still being able to get easyflo 2 'down under'. cheers, julian Thanks Julian. I'll have to look for some Easyflo 2 .... I get my solder from UK! What part of Wales are you in? I lived in Pembroke after leaving South Africa ... loved it! |
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Geoff
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Post by Geoff on May 13, 2014 22:41:29 GMT
Hi JULIAN-------- Just out of interest sake, I hope you don't mind me adding this in ?? Here are some extracts from my R & D work on The Bear's Boiler calculations.......In order to get an initial idea I looked at BR Standard Boilers with similar overall dimensions..Thus the 9F and Britannia then slightly smaller with the 4-6-0's and finally the 2-6-0's just for comparison.............Having done all the number crunching etc. I came up with the Main Flues, the Small Flues and then the % grate area for No111........As you can see it came out at 17.74% which I think is satisfactory.........The blast pipe, regulator, main steam pipe were then calculated in a similar manner -------------- ---------------- Nice idea Hagley ... but its too pixellated to be able to read. |
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Post by Deleted on May 13, 2014 23:16:05 GMT
----------- must have lost some quality during the long journey to Perth, maybe ?? LoL !! --------- I think it's the plastic sleeves that are giving that effect ??
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Post by Deleted on May 14, 2014 8:24:49 GMT
There is a glimmer of hope, apparently there is another set of raw castings for terrier cylinders at Sheffield park, the wait goes on with 55...........  |
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jma1009
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Post by jma1009 on May 17, 2014 21:39:30 GMT
ive done hardly anything in the workshop the last 2 weeks apart from repair the broken spring on the rotary lawnmower starter. i did however manage to get the inner firebox doorplate nearly ready for silver soldering into position this afternoon. all that was required was a couple of 6BA phos bronze screws to hold the top in position and stop it moving, and holes for 2 3/32" dia copper rivets to the inner wrapper below the foundation ring, and a bit of 'dressing'. not everything goes quite according to plan... i had forgotten when ordering the copper sheet that i'd added a bit extra to the inner firebox wrapper width just in case there was an error in cutting same, and also forgot about this when doing the inner wrapper to inner firebox tubeplate joint. i should have made the inner wrapper dead to width before bending it! so that there is ample space for the water to circulate (plus not impede circulation for the water gauges) i now need to remove about 1/8" from the inner wrapper edge sticking up in the pic below, before silver soldering the inner firebox doorplate to same. anyway everything fits ok and i can get a 2 thou feeler gauge round but not a 4 thou feeler gauge. probably wont get this done or the silver soldering till one evening this coming week. again not everything goes according to plan... i chain drilled and filed the opening for the regulator rod flange in the backhead one evening this week. despite what i though was careful measuring the centre of where the regulator rod goes is spot on the top of the extra middle crownstay i'd added! so i will have to fit a cranked regulator rod to clear same. (not the first time ive had to do this). the regulator flange on the BOXHILL design is much higher than on fullsize though putting it in the correct position wouldnt have been a problem had i not decided to significantly strengthen the firebox crown by fitting the extra middle crownstay! i was very fortunate in 1990 on a visit to Reeves at Marston Green to buy 100 6BA phos bronze screws in phos bronze. i think ive about 12 left now. they were a one off purchase by Reeves so never listed in the catalogue. cheers, julian  |
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Post by Deleted on May 17, 2014 22:09:26 GMT
Great work Julian....I'm thinking a lot more of my own build and making notes of your great build which then brings questions, one such is regarding your comments on the 6BA phos bronze screws. Assuming the threads are tapped into the copper and then the parts are silver soldered embedding the screws into the job are the threads tapped 6BA or would they be something like 5BA to allow more room for the solder to flow through the joint, or am I missing something? also is there a limit to how many screws or rivets can be used to help assembly before it's seen as a possible structural compromise or is it not important as long as the joints are sound?
Cheers
Pete
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jma1009
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Post by jma1009 on May 17, 2014 23:09:44 GMT
hi pete,
so long as all rivets and screws are silver soldered over both sides there is no limit on the number. personally i find them a pain as easy to miss when the torch is roaring away and you are concentrating on the joints. hence why i try to have as few as possible. on a normal firebox which is 'waisted' the firebox plates are kept in position by the waisting. on the BOXHILL boiler and for that matter DONCASTER's boiler this doesnt apply and a few screws or rivets are required.
i taped the 6BA generous tapping size, and the clearance holes needed drawing over slightly so amply clearance, so should be ok for silver solder to run through. this is the advantage of boiler work compared with other stuff as you dont have to be too particular and indeed if everything is absolutely tight you wont get the silver solder to flow where it should (within reason). i prefer rivets to screws. however on the inner firebox doorplate a couple of screws at the top are what ive found to be ideal.
you can just see one of the rivets securing the bottom of the inner wrapper to the inner firebox doorplate. as it is below the pressurised area ie below the foundation ring if i miss it it wont matter!
cheers,
julian
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Post by Deleted on May 18, 2014 13:23:28 GMT
Thanks for explaining that for me Julian... things are beginning to make more sense in my head and also looking a little easier or should I say less problematic than first thought.
Cheers
Pete
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jma1009
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Posts: 5,919
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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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