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Post by Deleted on Oct 5, 2014 22:31:37 GMT
Oh yes-------High pressure glands !!.......I'm not up to speed with Don's and Julians type of knowledge but why any designer would actually CHOOSE not to have the lower pressure, exhaust gland packing on the outside is beyond me !!-------I suppose the shorter, smoother run for the exhaust from the centre of the cyl. block to the blast nozzle might be attractive ??
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Post by donashton on Oct 6, 2014 7:01:50 GMT
Hi Alan,
I think that the answer here will be historical rather than mechanical. You can have a piston valve inside or outside admission but a slide valve will always be outside admission. If an older variant had a slide valve you can 'modernise' it to PV outside and use the same gear. GW Bulldog, etc is a case.
We might wince at HP glands, but if a gland is going to leak it will do so whatever the pressure. Most models have leaking PVs, but you only hear it as pressure rises and maybe don't see it at all!
One thing ought to be clear - a rocker in the valve driveline is reversing the direction of travel. It is NOT a means of changing the level of the drive, as LBSC and others thought. It may prove handy but its essential element in valve gear terms is the reversal of drive. The only other reversal opportunity is to put the pole (or screw) into reverse. That's ok for running round the stock, but all that linkage thrashing about in the air on express duty.....?
Don.
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Post by Deleted on Oct 6, 2014 8:07:39 GMT
"-------but all that linkage thrashing about in the air on express duty...." Yes, quite so !!..........LBSC's GWR 0-6-0PT PANSY has that reversing leverage and caught out our good friend, the late Ray Tranter....I had just finished building a new crankshaft for a club member's model ( Some "Heroic" person had ARC-WELDED the whole assy......with little or no penetration.........and it had broken in three places !!!)...and had taken it over to the bar at Bridgnorth one Friday evening ( to show it off if I'm honest !)....I'd put the eccentrics in an approximate position pending replacing the wheel assy. and setting the valves......."Ah" says Trant. you're 180 degrees out!"............ I then explained about that rocking shaft..........After a moment's reflection he says----"Ah, you're spot-on then !"................The phrase}-----"Wot-ur-drinkinthen" came MUCH further down the line !!....PS}--After the re-build we took it along to the Derby MES open day where it pulled 3 trucks with adults comfortably, with the fire-bed shaking-down as we progressed...............The owner later sold it out from under me without so much as a "Thank-you"......Some people, eh
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Oct 6, 2014 11:35:55 GMT
hi ben, many thanks for the above very interesting pics of the Maunsell Q. comparing them with the pics of the valve gear in don ashton's article of the Bulleid Q1 valve gear, it does seem to me that the Q1 valve gear is an exact copy of the Maunsell Q valve gear in every detail! this is very important as suggests that rather than Bulleid producing a 'revolutionary' new 0-6-0 design in 1938, he used the existing Q class chassis design together with the Q class cylinders and valve gear, and his often quoted criticism that in 1937 the Maunsell Q class design was 'archaic' was very unfair. cheers, julian
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Post by charley on Oct 26, 2014 19:31:32 GMT
www.bulleidlocos.org.uk/_q1/q1fullsize.... Large scale modelling Southern Railway Bulleid Q1 0-6-0 locomotive, model engineer Try this address, apologies if my cut and paste isn't great but you'll find this on Google. On the tabs are a number of models some based on the Don Young 4F others totally scratch built prior to the recent design in ME. Very impressive. Charley
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Post by donashton on Oct 26, 2014 21:27:10 GMT
Hi Ben,
Just to thank you for posting those pictures. My original untitled drawing was found in bundles at the Clapham Museum and Jim Russell asked if, as he expected, it was the Q1. Your photos match my drawing in detail.
However, Julian kindly relayed his E1, D1 drawing and the major difference is the move from end suspension and underslung weighshaft to a properly central lifting link to the trunnions, well offset in an endeavour to overcome the wrong choice of expansion link. So although not the same, the parentage is confirmed.
Don.
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Post by Deleted on Oct 27, 2014 13:23:04 GMT
One thing ought to be clear - a rocker in the valve driveline is reversing the direction of travel. It is NOT a means of changing the level of the drive, as LBSC and others thought. It may prove handy but its essential element in valve gear terms is the reversal of drive. The only other reversal opportunity is to put the pole (or screw) into reverse. I'm puzzled by this statement. Surely rotating the eccentrics by 180° around the axle would reverse the direction of the valve?
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Post by donashton on Oct 27, 2014 14:45:14 GMT
Hi Superseven,
Quite right, but apart from the physical difficulty of re-cutting the keyways it would also cross the eccentric rods. Any corrections carried out to equalise the events would also be wrong and the lead would decrease towards mid gear instead of increase. The problem of conversion from linear to rotary motion ensures that there are no simple mirror reversals in valve gears.
Don.
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Post by Deleted on Oct 27, 2014 17:52:21 GMT
OK, understood, many thanks for the explanation!
I'm familiar with the GWR 56XX class which had inside admission piston valves, driven by Stephenson's gear with 'open' eccentric rods and launch links, via a rocker shaft. The rocker shaft carried out the reversal exactly as you have described.
Engines with slide valves, rocker shafts and 'crossed' rods did exist though - on page 174 of 'Locomotive Management' there is a diagram of just such an arrangement, though I don't know what type of engine it refers to.
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Post by donashton on Oct 27, 2014 21:28:03 GMT
Superseven, The primary use for crossed rods is in four shaft traction engines, otherwise the engine would go forwards in back gear. The lead characteristics are unsuitable for locomotives. The 56xx gear is unique to the Class and Willie Pearce must have been off sick, much to the embarrassment of Collett when the first one disgraced itself. As you say, 'Getting it wrong takes just as long (or longer) as getting it right! Don.
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Post by Deleted on Oct 28, 2014 22:01:11 GMT
I've just been reading Haresnape's 'Maunsell Locomotives' and he says this of the Q class:
"Stephenson's link motion, with long-travel piston valves of 10in diameter were fitted. The valves had outside admission, giving a short and direct passage for the exhaust steam to the blast pipe".
So presumably Maunsell was prepared to use high-pressure glands, to get the benefit of a freer exhaust. Now, given that the D1s and E1s were conversions from slide valves, presumably with the same crank axle but with the addition of a rocker shaft and inside admission piston valves, what about the L1s? They were built new with piston valves, but were they inside or outside admission?
High pressure valve glands are not unusual - all slide valves have them - but then how many times have you seen an inside-cylindered engine with leaking valve glands, and the driver unable to see where he's going?
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Oct 28, 2014 22:33:12 GMT
hi superseven,
the L1 valve gear was based on the E1 and D1 valve gear, as were the cylinders with large inside admission piston valves.
at the current moment in time i can find no reference as to why Maunsell adopted outside admission piston valves for the Q class some 11/12 years later. expenditure on steam locomotives on the SR was very restricted in Maunsell's time. wherever possible standard parts were utilised on every new design. the design of a new type of cylinder block for a humble frieght 0-6-0 instead of using standard parts is very odd - and was arguably quite unnecessary for such a loco. plus in any event the Qs didnt benefit from free exhaust from the outside admission piston valves due to the very poor original smokebox arrangement. perhaps we shall never know - though the fact that both Maunsell and Clayton were ill by this time, and Holcroft was on outside duties away from the drawing office might provide a clue. the fact that Holcroft never commented on the change of design in the Qs suggests he wasnt aware of it at the time - as every other design development in Maunsell/SR days was very well detailed by him.
cheers, julian
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Post by Deleted on Oct 29, 2014 8:57:30 GMT
Quote}--"it's terrible this modernisation thing"......Yes, and from this "thing" came those evil Deezal-Weezal and Sparky Lectrics, Kerosene Castles, the HST, APT, BBC, MoD, GEC, NEC, EEC, rant--rant---rant--eh?..wot?....OH ***(Expletive deleted) *****, I've taken the red pills again instead of the Blue ones....................Sor-reeee !!
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Post by Deleted on Nov 18, 2014 7:31:34 GMT
------and not a Superheater in sight !!..............
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Post by fostergp6nhp on Nov 18, 2014 7:36:26 GMT
But the flues are there!
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Post by Deleted on Nov 18, 2014 8:09:52 GMT
well, it'd leak summat awful if they weren't--LoL !!
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Post by ettingtonliam on Nov 18, 2014 11:50:30 GMT
hi superseven, the L1 valve gear was based on the E1 and D1 valve gear, as were the cylinders with large inside admission piston valves. at the current moment in time i can find no reference as to why Maunsell adopted outside admission piston valves for the Q class some 11/12 years later. expenditure on steam locomotives on the SR was very restricted in Maunsell's time. wherever possible standard parts were utilised on every new design. the design of a new type of cylinder block for a humble frieght 0-6-0 instead of using standard parts is very odd - and was arguably quite unnecessary for such a loco. plus in any event the Qs didnt benefit from free exhaust from the outside admission piston valves due to the very poor original smokebox arrangement. perhaps we shall never know - though the fact that both Maunsell and Clayton were ill by this time, and Holcroft was on outside duties away from the drawing office might provide a clue. the fact that Holcroft never commented on the change of design in the Qs suggests he wasnt aware of it at the time - as every other design development in Maunsell/SR days was very well detailed by him. cheers, julian Sorry for the belated response to this. According to J E Chacksfield, the author of 'Richard Munsell - An Engineering biography', Eric Forge, a member of Muansell's staff at Eastleigh, gave him a lecture on outside admission valves, then persuaded Maunsell to get up on a trestle in the works, and look down the blastpipe of a Drummond D15 which was under repair, which apparently gave a good view into the cylinders and convinced Maunsell of the virtues of the free exhaust arising from the use of outside admission piston valves. Richard
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Nov 18, 2014 18:07:23 GMT
hi richard,
thank you very much for that quote from Chacksfield's book. i read it when it first came out but didnt think much of it so never bought it.
i seem to remember that Chacksfield very annoying doesnt quote references and sources.
i am not in a position to judge whether what Eric Landis Forge stated is correct, as quoted by Chacksfield.
i do know that a couple of other statements by Eric Forge were questioned. for example he claimed in one article that he assembled a collection of old relics (old locos) at Eastleigh as part of a proposed Southern Railway museum... although there were a number of very old locos stored in the paint shop at Eastleigh extensive research by members of the Isle of Wight Steam Railway in recent years found no evidence to support an intention to set up a museum such as that which already existed at York. (one of the locos was the famous Ryde of the ex-IWR of 1863 vintage).
another concerns his assertion that the original cylinders on the SR Lord Nelsons had tortuous passages and all had new cylinders fitted of improved design - yet one of the Lord Nelsons never had it's cylinders replaced and showed no difference in performance when compared to the re-cylindered members of the class.
when Eric Forge wrote a few articles in the mid 1980s he must have been about 95 years old.
by all accounts Maunsell didnt visit Eastleigh very often, and his office was located at Waterloo in SR days rather than at Ashford. his assistant James Clayton dealt with Eastleigh. i do find it a bit odd that Maunsell would have been called over by Forge and asked to climb inside a loco smokebox to peer down the blastpipe.
Forge was not a senior member of staff.
nevertheless an interesting story!
thank you again, richard.
cheers, julian
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Post by joanlluch on Jan 29, 2015 20:01:45 GMT
This is great. I wish some day the few surviving engines in my country were restored to running condition.
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dscott
Elder Statesman
Posts: 2,438
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Post by dscott on Jan 30, 2015 23:52:05 GMT
She looks so much better from the time we saw her during the summer without the boiler!!
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