jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Dec 16, 2018 22:38:37 GMT
Alan, I hope your model turns out to be more successful than the prototype. From what I read it was a complete lemon. Too long, too heavy, poor steamer, but Hey it looks spectacular! Hi Andy, I thought so too, till some years ago I bought the Chapman series of books produced by the GWR publicity department pre and post the 1923 Wembley Exhibition (when a GWR Castle was posed alongside LNER's Flying Scotsman). The 'penny dropped' so to speak, and everything then fell into place nicely... Let's not forget that in Churchward's pursuit of his standard loco classes and his policy of standardisation, he did a lot of experimentation, and built lots of one off locos, plus classes of locomotives that are often forgotten these days. No.98, and 'William Dean' No.100, 'The Krugars', the 'Aberdare' class, the French compound locos bought and tried out extensively at some considerable expense, to name but a few. 'William Dean' No.100 was a sort of forerunner of the 'Saints' and the same year as the GNR Ivatt large boilered Atlantics. The famous GWR 'Stars' ultimately were the results of lots of experiments, and Churchward's 'standard' designs all incorporated excellent valve gear design thanks to W H Pearce, the GWR valve gear expert, with long travel piston valves, and high pressure boilers. The Great Bear was a one off - and a very special one off at that. An exercise in boiler development allied to the very successful 'Star' chassis, cylinders and valve gear. It coincided with a marked increase in the GWR publicity machine that eclipsed what had then been LBSCR as the primary interest of 'enthusiasts' and the general public. It now had a massive locomotive, that for some 15 years took pride of place as part of the GWR's publicity department. A high pressure boilered Pacific loco with long travel piston valves, and a tremendous pulling power and tractive effort! So, back to publicity, and the GWR Castles in 1923, and the Wembley Exhibition. In order for Collett to claim the Castles as the most powerful locos, he had first to withdraw 'The Great Bear'. For myself, I don't think The Great Bear was a failure - it was in any event necessary to build as part of Churchward's open mind about boiler development. It had long periods under overhaul same as Marsh's famous 'Abergavenny' and 'Bessborough' on the LBSC, as in all 3 cases no spare boiler/pool understandably. However, I think subsequently the Collett influence on the GWR publicity machine over egged the loco's problems, in part justification for his 're-build' (scrapping) of such an iconic and famous loco (which Churchward was known to be upset about at the time). I think a lot of the steaming problems were the result the GWR's 'common user policy' for footplate crews, and fireman being unfamiliar with how to fire a wide grate. Had the GWR had the sort of policy the LBSCR had with dedicated crews for dedicated locos, this problem might not have occurred. The trailing axleboxes under the wide firebox were stated (subsequently) to be a problem, but the actual mileage figures when not under overhaul are quite respectable. The route availability was a bit of red herring - the GWR had lots of Old Oak/Paddington to Bath/ Bristol 'diagrams' that suited 'The Great Bear' perfectly. Cheers, Julian
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Post by delaplume on Dec 26, 2018 12:35:32 GMT
Hello everyone, One of the "joys" of living in a 3-Bed Semi as a single occupant is that you get to "Proof-read" your own Engineering Drawings.. in this case for The Bear.......... Now, to my mind this can be likened to an Organisation ( For example }-- A National newspaper ).. investigating themselves after some sort of Scandal... it's hardly likely to be totally unbiased or to have an objective viewpoint... I last worked on the Tender wheel and axle drawings some 3 years ago and since then I have acquired a job-lot of 5/8" diam. BMS bar of varying lengths......I like to use this for axles as in general it tends to be approx.....0.001!" or so under nominal size, which fits in nicely with my preference for working to a Hole Basis on fitting........ie}--- the hole is to size and the shaft is varied to obtain the degree of fit, tolerance etc.... So this morning I gathered all the relevant Bitz'n Bobz for a trip to the bottom of the garden and the dedicated Machine Shop...only to find that some of the dimentions re}--- axle and axlebox did not match up....having sorted that wrinkle out I then had to go back to the house, into the spare bedroom and trawl through all the Main Drawings library and adjust dimentions that had received a "knock-on" effect change as well...... Two hours later and it's back to square one and the Long Trek down to the Machine Shop for a re-start on those axles !!!--grr !!
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Post by delaplume on Dec 28, 2018 1:14:14 GMT
Hello everyone, Just a few photos to round off this, the first month of The Bear's thread........ A big "THANK YOU" to all who have contributed and maybe you could encourage some of the others to join in as well Just a thought}---- are there any "Bear" related items, photos, documents etc that are outside of the UK ??....Australia, New Zealand, you guys know of anything ?? This is a 3.5" gauge Boiler made for a customer by Castle Instruments, Cornwall.. This is my 5" gauge one. Designed by myself with consultation input by John Ellis....Built by John Ellis.
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Post by nick952 on Dec 29, 2018 14:26:17 GMT
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Post by delaplume on Dec 29, 2018 20:38:43 GMT
Hi Nick, YES, I do already have them but NO, not as close or with such clarity so they are a most welcome addition to the archives..... On the photo at No.1 platform, Paddington you can see a small, box-like item near the join between the rear of the smokebox and the front of the boiler barrel....and below the handrail.. Anyone know what that might be ?? Alan
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Post by Deleted on Dec 29, 2018 20:47:14 GMT
e addition to the archives..... On the photo at No.1 platform, Paddington you can see a small, box-like item near the join between the rear of the smokebox and the front of the boiler barrel....and below the handrail.. Anyone know what that might be ?? Alan Hi alan If I'm looking at the right part, could that be the oil atomiser, it's the same position for 4472? Pete
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Post by delaplume on Jan 1, 2019 5:00:53 GMT
JANUARY 2019}----
Hello Pete,
No, not oil atomiser ( They are incorporated within the Jockey valve's outlet pipes )...
Apparently it's an anti-vacuum valve for either the regulator or the superheater.............I've only ever seen it mentioned the one time during my research readings and --- of course --- I can't find it again !!
Alan
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Post by delaplume on Jan 1, 2019 5:12:35 GMT
Hello everyone, I've deliberately chosen this thread title so that we can get some sort of "Feeling" of the World that G.J.Churchward and his peers would be reading about in their Breakfast newspaper at the time that The Bear was conceived, built and run in..... Here's the Wiki for 1906 .... en.wikipedia.org/wiki/1906 ..... and 1907......https://en.wikipedia.org/wiki/1907.... the 2 years covering its' design and build period..
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Post by delaplume on Jan 2, 2019 14:27:24 GMT
Wish I'd seen this Pub in time for our for our New Year drinks !!-------------> ----------->
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Post by delaplume on Jan 2, 2019 14:34:05 GMT
I quite often see these guys when out and about}-------------
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Jan 2, 2019 23:53:45 GMT
JANUARY 2019}---- Hello Pete, No, not oil atomiser ( They are incorporated within the Jockey valve's outlet pipes )... Apparently it's an anti-vacuum valve for either the regulator or the superheater.............I've only ever seen it mentioned the one time during my research readings and --- of course --- I can't find it again !! Alan ...or possibly a superheater damper? In a reply to Sir Henry Fowler at the Inst of Civil Engineers in 1913, Churchward claimed the ability to divert flue gases into or away from the superheater flues. I don't remember seeing a picture of the mechanism ever, but I guess it would have to be in about that position. I would imagine the Bear would have been a prime candidate for such a device, but the GWR seems to have abandoned the idea quite quickly. -Gary
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Post by delaplume on Jan 3, 2019 16:07:31 GMT
JANUARY 2019}---- Hello Pete, No, not oil atomiser ( They are incorporated within the Jockey valve's outlet pipes )... Apparently it's an anti-vacuum valve for either the regulator or the superheater.............I've only ever seen it mentioned the one time during my research readings and --- of course --- I can't find it again !! Alan ...or possibly a superheater damper? In a reply to Sir Henry Fowler at the Inst of Civil Engineers in 1913, Churchward claimed the ability to divert flue gases into or away from the superheater flues. I don't remember seeing a picture of the mechanism ever, but I guess it would have to be in about that position. I would imagine the Bear would have been a prime candidate for such a device, but the GWR seems to have abandoned the idea quite quickly. -Gary Hi Gary, Yes, I think that's the sort of thing I had in mind .... I just have a vague memory reading about it some time ago and then Nick's photo bought it back again....
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Post by delaplume on Jan 3, 2019 17:22:08 GMT
Hello everyone, I forgot to add this photo of the "Scunthorpe" models' first boiler.......
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Post by delaplume on Jan 13, 2019 6:06:59 GMT
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mbrown
Elder Statesman
Posts: 1,719
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Post by mbrown on Jan 13, 2019 12:06:07 GMT
Sure, but the big difference to my eye is the firebox-tube ratio. The firebox tube plate on the A4, Duchess and Merchant Navy extends well into the barrel making the tubes much shorter in proportion. I don't know what diameter tubes the Bear had, but it can't have been easy to get a decent length to diameter ratio as well as keeping them small enough to promote good heat transfer and get enough area through the tubes for gas flow in relation to the size of the grate.
I know these things are hotly debated in ME circles, but my own view is that it is really important to get a decent firebox volume in relation to the grate (so especially critical for wide grates), and good gas flow through tubes with a good length to diameter ratio. On LYN, the tubes were long in relation to the firebox, so I increased the diameter a bit, but that meant I couldn't get so much gas flow area. Consequently, if the lower 2 tubes get blocked she goes right off the boil. On the BMR loco, I put in a short combustion chamber to get plenty of small tubes at the right ratio, and I can't stop her making steam.
Do you have a combustion chamber in your boiler? I feel sure the Bear would have benefitted from one in full size.
Malcolm
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Post by delaplume on Jan 13, 2019 16:56:19 GMT
Hi Malcolm, and thanks for the interest......For the moment I can give you the Wiki link which has the tube dimentions etc for you......Regarding the various ratios, calculations etc I'll have to get back to you a little later on as I'll be re-visiting my notes to refresh my memory etc................ en.wikipedia.org/wiki/GWR_111_The_Great_Bear ------------- Yes, there is a combustion chamber but WITHOUT any cross flow water tubes that's normally associated with it....When I first drew-up the 5" gauge boiler I referred to the Swindon drawings from York and based the main, outside sizes on full size dimentions ...This gave me max, size and shape.....From this I then reverted to 5" gauge practices internally....... My first drawing produced was as per full size with the firbox tubeplate being in the same, scale position as it's larger counterpart......... and the Smokebox tubeplate was similarly located at the front end, thus giving tubes of an original, scale length......... My "Consultant" throughout all of this was John Ellis who suggested that a plain combustion chamber could be fitted.......After some lengthy periods at the drawing board I eventually came up with the design that's now actually in the 5" boiler......As a result of this the tubes were shortened to match.....One day just after John had OK'd the final production drawing I was glancing at the final set of papers and it occurred to me that I might measure the length of the new, shorter tubes.......... You'll never guess but they now were of the same length as a Peter Riche 5" gauge Castle !!.....and the pattern I had chosen has more tubes in it than the Castle...... I can give you my model's Tech. Spech ASAP...... Bye for now## Alan
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mbrown
Elder Statesman
Posts: 1,719
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Post by mbrown on Jan 13, 2019 21:41:31 GMT
I avoided cross water tubs in my combustion chamber too - partly because I thought the joints might be weakened by later silver soldering and the repeated expansion/contraction forces, and partly because they would have got in the way of the radiant superheaters I fitted. But, of course, what I lost as a result was the staying effect on the crown of the combustion chamber... The club boiler inspector saw the design and drew in a big X shaped stay (1/8" copper sheet, about 1' high) on top of the combustion chamber. That, in turn, meant I had to fiddle a bit to get my blower tube through the boiler in the prototypical location just under the regulator - but I got there in the end and the combustion chamber didn't deform at all under test.
How have you stayed yours, without having water tubes?
Malcolm
Malcolm
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Post by delaplume on Jan 15, 2019 13:03:30 GMT
Hi Malcolm Just a few photos to start with then}-----
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Post by delaplume on Jan 15, 2019 16:08:13 GMT
Hello Malcolm,
Here's the Tech. Spec's for Boiler No. ST 391}---------
All items Copper unless otherwise stated...
SWP = 100 psi
Stays = 0.250" dia. snap head with plain tail.
Barrel thickness = 4mm
Internal steam supply pipe = 0.500" diam.
Inner Firebox wrapper, front and rear plates = 3mm
Smokebox & Firebox tubeplates = 4mm
Outer wrapper = 4mm
TUBES}---
Small = 0.500" diam x 26 off.
Large = 1.000" diam x 3 off. all thinwall type.
GRATE AREA}--- ( 4" x 6" ) + ( 3" x 6" ) = 42 sq. ins.
FIREGRATE = Stainless Steel ( Taper Bars ) at 50% ( Bar = 3mm, gap = 3mm )
Tube / Grate Area Ratio = 16% This is an average of British Railways Standard Locos extracted from}----- "The Standard Steam Locomotives of British Railways" by Roger P. Bradley......Published by}---- David & Charles..........ISBN}---- 0-7153-8384-1
More later
Alan
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Post by runner42 on Jan 16, 2019 0:47:33 GMT
Alan, does it have a superheater?
Brian
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