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Compounds ex time machine thread

Discussion in 'Steam Traction' started by Copper-capped, Jan 1, 2018.

  1. sir gilbert claughton

    sir gilbert claughton Active Member

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    does anyone have any info on the compound Castle that Collett didn't like
     
  2. sir gilbert claughton

    sir gilbert claughton Active Member

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    I don't believe Churchward had any intention of "proving" a compound to be better than his simples . Stanier's proposal for a compound Castle would suggest he did not convince everybody .
    I still think that if the Royal Scot chassis had not existed , Staniers Scot would have been a compound
     
  3. huochemi

    huochemi Well-Known Member Friend

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    As with pretty well everything else on NP these days, this has been discussed before. Visually, with plate frames and independent leaf springs to each axlebox , the bogie under La France etc has no resemblance to the Castle / Hall / Duchess bogie. The bar frame design of the Castle bogie is in fact an American design and the suspension is by an inverted leaf spring acting through an equalising beam on each side. The attribution to De Glehn can only relate to the weight transfer by means of "spittoons" each side sliding on flat surfaces fixed to the frame, and/or the side control spring arrangement, American practice favouring swing links. Assuming that a County bogie is the same as a Modified Hall, then in fact the County bogie did not abandon such attributes and more nearly resembles the La France bogie as it also has plate frames and independent leaf springs.
     
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  4. Jimc

    Jimc Part of the furniture

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    The extension frames? I wasn't aware the frenchmen had them. The point of the extension frames was surely to permit the back to back bolted outside cylinders with shallower but thicker almost bar frames. Holcroft notably didn't like them, and designed the "splice frames" which go over the cylinder so the main frames could be shallow. But my understanding was that the deGlehns, like the GWR 4 cylinder locomotives, had plate frames right through.

    That's my understanding. Holcroft and I think others reproduce a plan drawing showing the revised de Glehn based side control on one side and the original layout on the other, but without the design expertise I find it difficult to fully interpret. I don't have the book here to comment on the weight transfer.
     
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  5. Eightpot

    Eightpot Part of the furniture

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    Perfectly true, but you have overlooked one vital point. On the Midland compounds, being a 4-4-0 and driving on the the leading coupled axle, the connecting rods drove the crankpin adjacent to the wheel boss with the coupling rods outboard of the connecting rods. This in turn meant that the outside piston rod centres were closer together which thus permitted larger outside cylinders and still being within the load gauge.

    If driving anything other than the leading driving wheels the connecting rods would have to be outboard of the coupling rods thus pushing the piston rods centres further apart resulting in smaller outside cylinders to stay within the load gauge. This is why I suggested a maximum of (say) 20" bore cylinders for a UK version of 242A1, and much the same for any other loco too.
     
  6. Hermod

    Hermod Member

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    9F cylinders were 6feet 8 apart and Midland Compound 6 feet 3.
    9F cylinders were 20 inch diameter and Compound outher 21 inch.
    On straigth track Compounds could have had 22.5 but not on sharp curves due to sitting further forward of fixed wheelbase.
    The proposed Cox 4-6-o compound https://imgur.com/fnyPnUw had 22.5 inch low pressure cylinders
     
    Last edited: Jan 2, 2018
  7. Jimc

    Jimc Part of the furniture

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    Ah well, the solution is obvious. Don't have round cylinders. Make the cylinders a rounded off rectangle cross section (also called stadium or obround). Then you can have much bigger cylinders without loading gauge problems. OK the machining and maintenance will be a tad tricky, but it has been done in motorsport.

    http://www.highpowermedia.com/blog/3714/oval-pistons

    460-4073Castleovalcylindercrop.jpg
     
    Last edited: Jan 2, 2018
  8. Hermod

    Hermod Member

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    or even smarter:
    make synthetic diesel from coal like Germany/South Africa did,and save the world for some CO2
     
  9. LMS2968

    LMS2968 Well-Known Member

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    Motorsport, particularly F1, engines are often designed to last one race and then be rebuilt. Cost isn't an issue.
     
  10. Jimc

    Jimc Part of the furniture

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    It may not have been an altogether serious suggestion...
     
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  11. threelinkdave

    threelinkdave Well-Known Member Friend

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    There was an earlier post, I looked away for a day, re the hush hush and materials, steel iron ductile iron etc. There seemed to be an implicit assumption that water tube boiler used in power stations and ships were perfeect. No where near true.

    I once had the pleasure of giving the opening paper at the MIEE on boiler ligament cracking. The question was how much does the operating regime affect thermal stressing. My paper was as a system operator why we needed to request large output changes - mainly the period 06.00 (minimum demand) and 09.00 to 10.00 (morning peak). The problems and issues which came out in later discussion highlighted the problems.

    Now if we look at locos we expect them to start from cold run 100 miles , stop then re start. Ships boilers are run to pressure and remain at that pressure for days on rend. it is a bit like the HST cooling problems using a marine engine which gave little trouble at constant output in a stop start railway environmennt.

    As to compounding I have read somewhere that whilst a gain in efficiency was possible the higher construction and maintenance costs outweighed the thermal savings. The big 4 were businesses first and foremost so if an idea did not show value for money iy got dropped
     
  12. Copper-capped

    Copper-capped Active Member

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    All fair points, (thanks for expanding them), and I like the sound of your last sentence about "resources, time, support and more". That rings truer to me than being short of sufficiently capable people although I get the point you make about education - doubtless their would be some degree of fumbling in the dark before concepts were fully grasped and problems overcome.

    I feel that had the incentive been strong enough for a remit to have been given, then the design teams at any of the big four or BR would have stretched their intellectual legs and found a way to make compounding a success. So coming back to resources, time, etc, the pros and cons would need to be weighed up before a decision to 'compound or not to compound' was made. It would certainly be interesting to know how this process led to the midland compounds as the only large scale production outcome, and yet, no others - perhaps a more daring CME?!

    Cheap, plentiful coal in the UK has to be the biggest factor. With compounding extolling the virtue of better fuel economy, introducing complexity of design to overcome a problem that was basically not a problem would pretty well draw a line through it. I don't think fuel economy was ever foremost on the design check list in the UK, and moving on to Riddles' BR standard designs no change there at all. Add to that 'cheap to build', 'reliability', 'easy(er!) maintenance', and 'capability',and that's pretty much what was delivered. If you bundle those factors up into a design brief then invariably you will fall back on well understood, proven technology rather than embark on a research and development phase that may only yield marginal benefits.

    Perhaps cheap coal did cause British engineers to be perceived by some as lazy thinkers, but then again, perhaps they could afford to be because the bean counters (as always) probably had the last word. :)
     
    Last edited: Jan 2, 2018
  13. johnofwessex

    johnofwessex Part of the furniture

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    David Wardale made an interesting comment on the implications of low thermal efficiency going beyond the coal bill - things like ash disposal, the amount of coal that had to be hauled to coaling points then handled.

    Given that tried against Leader, a Southern Mogul gave 4% efficiency V's the SAR Class 26's 15% shows that there was significant potential for improvement - imagine if the Mogul could have been upped to 8% efficiency - halving coal consumption and the knock on effects
     
  14. Jamessquared

    Jamessquared Nat Pres stalwart

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    I don’t think it’s fair to describe them as lazy. Engineering is about coming up with effective solutions to problems within available constraints. You can hardly blame the engineers for being lazy if, for example, a tight loading gauge acted as a more severe design constraint than fuel costs.

    Tom
     
  15. Copper-capped

    Copper-capped Active Member

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    I totally agree. I was being a little cheeky there. I might have a little think and a re-edit to clarify.
     
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  16. Jimc

    Jimc Part of the furniture

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    Sure, and no doubt Churchward knew that too. But if you wait for everyone else's journey to be complete you go nowhere yourself. There was an awful lot of unrealised development potential in Churchward's two cylinder simple too. Churchward compared the best compound he could obtain with the best locomotive he had. What was the alternative? It would hardly have been sensible to stop all locomotive building for five years to see what developed. In five years time both the deGlehns and Albion were superheated and performing rather better anyway.


    Keeping the bean counters happy is one of the key functions of the engineer. After all you want there to be enough beans about that you can build your machinery and take your fair share of beans home at the end of the month.
     
  17. LMS2968

    LMS2968 Well-Known Member

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    You can never tell on Nat Pres!
     
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  18. LesterBrown

    LesterBrown Active Member

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    I've moved my reply to the Compounding thread.
     
  19. LesterBrown

    LesterBrown Active Member

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    I was going to say that efficiency in locomotive design was also directed towards getting the maximum power within a given weight, perhaps balancing the extra weight of the machinery against possibly a slightly bigger boiler.

    But then i realised that the DeGlehn compounds were in fact lighter than Churchward's comparable designs! (Their motion was i believed described as more like watchmakers work than engineering, but they did still last.)
     
  20. pete2hogs

    pete2hogs Active Member

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    It's been attempted many many times with stationary steam engines - it doesn't work well in general . See here:

    http://douglas-self.com/MUSEUM/POWER/squarepiston/square.htm
     

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