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Post by bambuko on Feb 10, 2016 18:16:42 GMT
Small gauge loco with two inside cylinders and valves on top. Not wanting to get involved with watchmaking, I would like to try Joy valve gear, rather than Stephenson's. Mainly because Joy gear would allow me to avoid trying to squeeze four eccentric between cranks There are some designs that could be used as an inspiration (e.g. Don Young's 4F), but I would like to at least try and understand, rather than "copy and hope"  Can anybody recommend good source, which would help me to understand and hopefully design Joy valve gear for small loco? |
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Midland
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Post by Midland on Feb 10, 2016 21:09:18 GMT
Hi Bam
I have the Aspinal drawings for the Aspinal (funnily enough) if you would like a copy but I think you should try Stephenson's as it is a very rewarding challenge to understand it. Don Ashton's website is a gold mine and well worth a good go at it. I am happy to have had his tutilage as one of the things one must do before going to the Barry Scrapyard in the Sky!!
Cheers David
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Post by bambuko on Feb 10, 2016 21:38:41 GMT
Thanks David,
It's not a question of understanding (or the lack of it...) of Stephenson's gear.
I am familiar with Don's webpage and have his book.
However, in very small gauges it is much easier to use Joy gear (see for example Q1 designed by Nick Feast) for inside cylinder locos.
OK, not true to prototype, but it works (apparently) fine.
Hence my question.
I suppose I could just draw it and run it in simulator until I get somewhere...
ps thanks for the offer of Aspinall drawings - very kind of you!
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jma1009
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Post by jma1009 on Feb 10, 2016 22:21:21 GMT
hi chris,
what loco is it and what gauge? the 1948 Joy valve gear designs for LBSC's Maid of Kent and Minx in 5"g are generally well thought of, though i know Don Ashton isnt a fan of Joy valve gear. the Nick Feast Q1 design used the LBSC Minx Joy valve gear of 1948 vintage.
the user friendly Wallace simulator doesnt do Joy valve gear.
cheers,
julian
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steam4ian
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One good turn deserves another
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Post by steam4ian on Feb 10, 2016 22:56:01 GMT
G'day all
Much as I respect Don and have high regard for Allan I am left wondering if it is all worth the effort to get perfect events through the full range of cut off possibilities. I say this as one who does run in the "company notch" as much as possible.
The reality of models is:-
They seldom if ever run in reverse, certainly not pulling loaded trains any distance.
They are seldom notched up, certainly not from videos I have seen from this forum
The fiddly screw reverser slavishly copied by modellers does not favour notching up on the run particularly on a busy track.
I would suggest that something that gives good events at say 55% cut off would be more than adequate for most models and probably still have a good performance at IMLEC.
Happy to be proved wrong.
Ian
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Post by bambuko on Feb 10, 2016 22:57:12 GMT
Thanks Julian, I thought that Nick's Q1 used Don Young's 4F as a starting point (at least that's what he says here) Don's comments and dislike of Joy's gear appears to be based on "full size" reasons. In smaller gauges, other considerations come into play. I thought that Charlie Dockstader's simulator covers Joy, but I haven't tried it yet, and anyway simulators don't design things for you (it's a bit like, being a CAD driver doesn't make you a designer  ) |
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jma1009
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Post by jma1009 on Feb 11, 2016 0:08:29 GMT
hi chris,
my apologies you are quite correct re Don Young's 4F, though Gordon and Don build an LBSC 5"G MINX in the 1950s as a first build, and knowing Don i suspect the 4F was a scaled down version of LBSC's MINX joy valve gear.
i agree designing a gear from first principles isnt easy unless it follows Don Ashton's excellent precepts!
cheers,
julian
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jma1009
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Post by jma1009 on Feb 11, 2016 0:14:59 GMT
i hope Ian, for whom i have the highest regard, isnt suggesting we should all go back to the days of slip eccentrics with 60% cut off as per many 2.5"g designs!!
Holcroft thought in fullsize the boiler efficiency was more important than cylinder efficiency ie the boiler was more important than the cylinders. we are handicapped in miniature with certain aspects of boiler design and firing and coal. therefore arguably the only areas where we can maximise efficiency easily is in having a decent cylinder and valve gear design and decent superheaters and decent draughting.
cheers,
julian
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Post by bambuko on Feb 11, 2016 0:54:00 GMT
...i agree designing a gear from first principles isnt easy unless it follows Don Ashton's excellent precepts!... and that's exactly my problem - Don doesn't say much about Joy gear... i hope ... isnt suggesting we should all go back to the days of slip eccentrics with 60% cut off .... that is precisely what I am trying to avoid, but it is not easy in G3 or G1 (although not impossible - see for example inside cylinders, with valves in between, and full Stephenson's gear in gauge O, by Clarry Edwards, as described in Dec 1991 article in "Model Railways") |
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steam4ian
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One good turn deserves another
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Post by steam4ian on Feb 11, 2016 9:24:57 GMT
G'day all
My comments were tongue in cheek but it does concern me the number of locos I see driven in full gear or close to it. My other beef is screw reversers which are very fiddly to adjust, you can make an extension but then you can't see the setting scale.
As for Bam's question, I recall seeing a simplified Joy gear in a book either by Evans or Greenly 9more likely Greenly). The connecting rod was T shaped one end of the cross arm went to the big end the other end of the cross arm went to the little end. At the bottom of the stem on the T the "eccentric" rod was connected. I think having the connection below the connecting rod somewhat compensated for the straight slide and gave better events. This was used commercially for a small gauge loco.
Ian
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Post by ejparrott on Feb 11, 2016 9:58:00 GMT
My Lilla will run in first and second notch, but not third or fourth. Ross Harrison ballsed that up for sure! Unfortunately it was one of the things that had been done before we discovered just how bad Ross' drawings were and switched to works drawing and measure the prototype. Dad never got chance to re do it all, which was planned after the completion of the TR No. 4. Maybe one day I'll get round to it
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Post by bambuko on Feb 11, 2016 19:56:23 GMT
...I recall seeing a simplified Joy gear in a book either by Evans or Greenly (more likely Greenly)... thanks Ian, and yes (I have both books). Both Greenly and Evans have a chapter about Joy valve gear, but I am not sure about their value? I used to be blisfully ignorant and happy when reading "the model engineering masters", but now (I am still ignorant) and full of doubt  (when I read Don Ashton's views about them): |
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jma1009
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Post by jma1009 on Feb 11, 2016 23:06:26 GMT
i think Don Ashton would dislike Joy valve gear even more with straight slides as per Greenly!
chris (bambuko) raises a very interesting point re small gauge locos and their valve gear. i dont have any experience in such small gauges, though the Gauge 1 live steam layout is always the highlight for me of any exhibition in the UK.
cheers,
julian
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Post by ejparrott on Feb 12, 2016 10:52:39 GMT
Don't come up to the Midlands Exhibition then Julian, the G1 layout's been missing for 2 years now  |
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Post by donashton on Feb 12, 2016 11:10:34 GMT
Not sure why I should be labelled 'anti-Joy's gear' for a) not including Joy in my book on Walschaerts' and Stephenson's gears (!), and b) failing to dive in and post when I have nothing to add.
I haven't counted, but I think that my name appears in this post more often than that of David Joy - that can't be right!
Don.
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Post by bambuko on Feb 12, 2016 13:04:18 GMT
Not sure why I should be labelled 'anti-Joy's gear' for a) not including Joy in my book on Walschaerts' and Stephenson's gears (!)... I don't think you are "being labelled" anti-Joy's gear? (although I guess some of the replies might be suggesting it... I can't control contributors to this thread). Best to quote the source: I simply asked: I didn't comment on Joy not being included in your excellent book, and I didn't use your name in my original question. Not sure why I should be labelled 'anti-Joy's gear' for .... and b) failing to dive in and post when I have nothing to add... Again, I don't think anybody criticise you for "failing to dive in"? You are free to dispense your knowledge and advice as you see fit, and if you think you have nothing to add that's OK as well  ...I haven't counted, but I think that my name appears in this post more often than that of David Joy - that can't be right!... It is indeed not right and I guess particularly annoying when people put words in your mouth and attribute to you opinions you have not expressed. |
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Post by donashton on Feb 12, 2016 14:45:42 GMT
Hi Bambuko,
Those who know me well know that I don't take offence, even regarding your last comment. If my name keeps cropping up it's because I am anxious to help where I can. Simon Bowditch has done pioneering work in fine tuning many of the Hackworth variants. This sort of work may well interest those modelling in small gauges.
Cheers,
Don.
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Post by bambuko on Feb 12, 2016 15:17:15 GMT
Hi Bambuko, Those who know me well know that I don't take offence, even regarding your last comment... Good! because for a minute I thought you sounded like a very angry man  ...If my name keeps cropping up it's because I am anxious to help where I can. Simon Bowditch has done pioneering work in fine tuning many of the Hackworth variants... That is the kind of lead I was hoping for - thank you. I will have to see if I can find out more about this chap and his work! p.s. (later edit):
just found Simon's webpage...This sort of work may well interest those modelling in small gauges... Trying to fit full valve gear for inside cylinders (with valves inside, irrespective of whether on top, below or between) is very challenging. It has been done (as I have mentioned) succesfully, but I am looking for something simpler and Joy gear seems to offer it. Chris |
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jma1009
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Post by jma1009 on Feb 12, 2016 22:24:16 GMT
hi chris,
you havent stated what loco it is? i am sure your choice of loco will be of great interest plus add a gloss on the valve gear design.
cheers,
julian
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Post by bambuko on Feb 12, 2016 23:00:08 GMT
...you havent stated what loco it is? ... I haven't mentioned it, because (although I am drawing a specific loco) I don't think it matters - the question is a general one for all Gauge 3,1,0 inside cylinder (typically British design) locos. By the time you add (out of scale) axleboxes, crankwebs, etc, the space available for the four eccentrics is rather small. Don't get me wrong - it is all doable, but the Joy gear offers practical, relatively simpler solution. OK, it would be yet another compromise and departure from prototype, but the smaller the scale, the bigger the compromises (in my humble opinion). ...i am sure your choice of loco will be of great interest plus add a gloss on the valve gear design... I have been reading up old issues of ME today with both LBSC's Minx and Don Young's 4F. I have also downloaded Charlie Docksteder's sim package. I think I have enough for now to get me going with the draughting on CAD. When I (eventually) have something to show I will come back and share and ask for comments/advice. It will take me some time, but luckily it is retirement hobby not a job |
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(when I read Don Ashton's views about them):
