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Post by bambuko on Sept 7, 2017 19:29:50 GMT
I am using version 2.8 of the above mentioned simulator. I want to run simulation for slide valve inside cylinders (with valves in-between), something like this:  Question for those knowledgeable in Docsteder simulator, which one should I use:  I had a look at all of them and don't seem to be able to get it right - no doubt another senior moment... |
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Post by Oily Rag on Sept 7, 2017 20:23:20 GMT
I am of no help, I have only used the Walchaert version.
Over to the more knowledgeable.
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Post by John Baguley on Sept 7, 2017 23:46:09 GMT
Assuming that the slide valves are outside admission. you want the ' British Outside Admission' option. This is for direct drive outside admission valves.
Personally, I avoid the Dockstader programs if I can. They ask for a lot of dimensions that are totally unneccesary for determining the valve events. The Hall and Wallace simulators are much easier to use. There is also a spreadsheet available for these programs to design the valve gear from scratch.
John
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Post by bambuko on Sept 8, 2017 2:21:17 GMT
Assuming that the slide valves are outside admission. you want the ' British Outside Admission' option. This is for direct drive outside admission valves... Thank you John, I thought that this was the one, but I am having difficulty modifying "frame dimensions" to make it look like the gear I want. ...Personally, I avoid the Dockstader programs if I can. They ask for a lot of dimensions that are totally unneccesary for determining the valve events.... Yes, I know of your preferences (from your own web page), however I find Dockstader much easier to use. This is nothing to do with determining the valve events and all to do with (I guess) familiarity? Lot of dimensions is not an issue - easy to get them from CAD. ... The Hall and Wallace simulators are much easier to use... Hall doesn't work on my 64bit machines. I suppose will have to try Wallace... ... There is also a spreadsheet available for these programs to design the valve gear from scratch... You mean Don Ashton's design spreadsheet? I would love to be able to use it, but despite reading both the book and the webpage I am finding it very difficult to grasp it, or to follow the instructions. Must be something to do with the way my brain is wired... |
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jma1009
Elder Statesman
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Post by jma1009 on Sept 8, 2017 20:52:01 GMT
The Hall simulator is very easy with centrally suspended links with Stephensons valve gear. I don't know why your computer doesn't like it - Docstader is far more complicated as John says. I would have another try with Hall.
You can always post all the relevant dimensions on here and I am sure quite a few of us will be able to run it on Hall for you.
Cheers,
Julian
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Post by donashton on Sept 9, 2017 8:48:38 GMT
So where is Don Ashton? For medical reasons I shall be brief. There will be those who expect a valve gear simulator to design a valve gear, whereas in truth YOU have to design the gear and the simulator does the calculation and provides the knowledgeable user with some idea of performance.
Prof. Bill Hall wrote a fairly straightforward simulator which will deal with most cases. Dockstader is a killer at 20 paces until you are well versed with the gear, the program, and the interpretation of a mass of detail. It is able to do this because each case is dealt with specifically.
This thread has at least attracted two of the most knowledgeable and helpful guys in the business - Baggo and Julian. Listen to what they have to say.
Don.
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Post by bambuko on Sept 9, 2017 10:02:50 GMT
Thank you gentlemen! Hall - simulator doesn't work on 64 bit machines - would have to run it in DOS emulator and not keen on that. Dockstader - it seems the "British Outside Admission" has lifting arm attached to the bottom of the link and I don't know how to change it to reflect what I am trying to model. 
Wallace - spend a whole day yesterday playing with it and it is a lot clearer now. I can see why you like it John. The easiest thing for me will be to use Wallace Julian - thank you for the kind offer to run Hall for me. I am more interested in learning it myself rather than getting the job done by somebody else, so I will persevere, but will come back with questions if I have any. Don - I will try not to cause you apoplexy - rest assured I am well aware that it is me who is the problem  I do not expect the simulator to do the job for me I was trying to use your spreadsheet without instructions, not realising that "Stephenson's offset trunnion rationale" is actually "Stephenson's Valve Gear Program Supplement". |
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Post by donashton on Sept 9, 2017 11:20:28 GMT
No sir, you are certainly not the problem. The learning curve is rather steep. Most model engineers want to make and run a steam engine, not spend hours pondering the mechanism.
My spreadsheet is not now easily done since the almighty Windows altered Solver.
Don.
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Post by bambuko on Sept 9, 2017 12:01:36 GMT
...The learning curve is rather steep... You can say that again... not made any easier by the fact that: - English is not my mother tongue. I can swear in it fluently and profusely, but trunnions and the like sometimes cause me a bit of work with a dictionary. - Imperial system is not in my blood. I use decimal and fractional inches easily, but still think in metric, so most of the time I end up converting things for reading. - Experts in something are not necessarily expert teachers of it. Simple sentence in your book (blindingly obvious to you, I am sure) sends me sometimes into days of reading other books to try to make sure that I "got it". Not made any easier by the fact that so many of these authors are confused themselves  - Symbols used are different in every book as well (sometimes they are different in the same book as well  ) Still... it took you half of your lifetime, so I will get it eventually with your help as well (hopefully before my time expires  ) My spreadsheet is not now easily done since the almighty Windows altered Solver... Is it only MS office spreadsheet that is affected? I can use others so maybe it will be OK? Chris |
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Post by donashton on Sept 9, 2017 16:32:56 GMT
Well, the imperial system is not in my blood either, as mathematics was always my worst subject at school. It hasn't improved in all these years!
The spreadsheet is not essential. I used it to verify that an algebraic statement was true, but don't ask me which - too much water has flowed under the bridge.
Outside Admission you want (- for British read GWR!)
Take solace from the fact that many drawing offices had inferior knowledge of valve gears.
Hey, I just noticed your Avatar has the perfect Stephenson's gear down each side, with adjustable linkage!
Best wishes,
Don.
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Post by bambuko on Sept 9, 2017 19:35:31 GMT
... I just noticed your Avatar has the perfect Stephenson's gear down each side, with adjustable linkage!... How very amusing  This avatar celebrates sci-fi writer Stanislaw Lem and it depicts "eight-storey calculating machine that doesn’t know mathematics all that well"... It was a Google doodle in 2011 ...The spreadsheet is not essential... I suppose it's similar to simulators - in that it doesn't design for you. So, if you understand what you are doing you don't need it? ...Outside Admission you want (- for British read GWR!)... That is indeed much better and closer than the "British" one. ...Take solace from the fact that many drawing offices had inferior knowledge of valve gears... No consolation I am afraid now that I've been told it can be done better... |
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jma1009
Elder Statesman
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Post by jma1009 on Sept 9, 2017 20:32:08 GMT
Hi Chris,
There are criticisms implied in your last few posts - or that is how those of us in the UK with English as our first language might perceive.
Would you want an LBSC or Martin Evans 'simple' or 'dumming down' explanation, where neither of these gentleman understood the intricacies of Stephensons gear, that would leave you none the wiser?
Any proper detailed treatise on valve gears is going to be heavy going and difficult! Some aspects of miniature loco building are not easy, neither the design of same from scratch.
We are pleased to help, so long as you don't offend (which I am also guilty of many times on here!)
Cheers,
Julian
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Post by Oily Rag on Sept 9, 2017 20:42:55 GMT
Assuming that the slide valves are outside admission. you want the ' British Outside Admission' option. This is for direct drive outside admission valves. Personally, I avoid the Dockstader programs if I can. They ask for a lot of dimensions that are totally unneccesary for determining the valve events. The Hall and Wallace simulators are much easier to use. There is also a spreadsheet available for these programs to design the valve gear from scratch. John I used the Dockstader and the dimensions to load are all the required ones that a builder will use when making the relative parts and their locations in relation to the driver centre. All the dimensions should be able to be pulled off the drawings. What dimensions are not required? Cheers |
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Post by bambuko on Sept 9, 2017 21:50:23 GMT
...There are criticisms implied in your last few posts - or that is how those of us in the UK with English as our first language might perceive... It is easy to be mis-understood (especially on interweb forums), regardless of one's (first) language. No criticism either implied or intended. ...Would you want an LBSC or Martin Evans 'simple' or 'dumming down' explanation... No, never asked for this. ...We are pleased to help, so long as you don't offend (which I am also guilty of many times on here!)... It was never my intention to offend you Julian. |
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