J
JorgensenSteam
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Here is some valve gear stuff I have been preaching for a while.
Pat J
Pat J
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Dan Rowe
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Pat,
Your plot is what is usually called a sine diagram. I like the oval diagram a bit better as it is a shape.
Does the plot take in account the error of the connecting rod and eccentric rod?
A very good program that will generate a cool sine diagram for a nonreversing engine or link motion reverse with marine links is the one by Rainer Radow. The program allows for superheatrd steam and atmospheric or a vacuum exhaust. See:
http://www.steamboating.de/valve/valve-maine.html
I wrote an article that got the same engine running in both Dockstader's and Radows's program and I will post in in the valve gear thread I started soon.
Dan
Your plot is what is usually called a sine diagram. I like the oval diagram a bit better as it is a shape.
Does the plot take in account the error of the connecting rod and eccentric rod?
A very good program that will generate a cool sine diagram for a nonreversing engine or link motion reverse with marine links is the one by Rainer Radow. The program allows for superheatrd steam and atmospheric or a vacuum exhaust. See:
http://www.steamboating.de/valve/valve-maine.html
I wrote an article that got the same engine running in both Dockstader's and Radows's program and I will post in in the valve gear thread I started soon.
Dan
J
JorgensenSteam
Guest
Dan-
Yes, the error in the connecting rod and the eccentric rod are both taken into account in the spreasheet plot, since it is a direct algebraic calculation, not an approximation.
I tried to get Charles Docsteader to document his formulas, but unfortunately they are buried in a mountain of Pascal code.
I can't blame Charlie for not being interested in documenting his program, he has done more than enough for the hobby just by creating his spectacular programs.
I don't want to be limited to someone elses program though, and therefore I have been creating my own spreadsheets and discovering the formulas needed.
Luckily there are very few formulas needed to be able to do effective valve gear design, so that is a good thing.
Alibre pro will actually create the same data that Docsteader's does, and put it in a spreadsheet format. I find a spreadsheet easier to use than anything, and I use the KISS formula (keep is simple).
I have discovered two programs other than Docsteaders that will do valve gear design, but again, they are undocumented, and I prefer to just program my own spreadsheet so that I understand what formulas are used and also to preserve, document and publish those formulas so that others besides those three guys can fully understand valve gear design.
I would like to see your program comparison.
Pat J
Yes, the error in the connecting rod and the eccentric rod are both taken into account in the spreasheet plot, since it is a direct algebraic calculation, not an approximation.
I tried to get Charles Docsteader to document his formulas, but unfortunately they are buried in a mountain of Pascal code.
I can't blame Charlie for not being interested in documenting his program, he has done more than enough for the hobby just by creating his spectacular programs.
I don't want to be limited to someone elses program though, and therefore I have been creating my own spreadsheets and discovering the formulas needed.
Luckily there are very few formulas needed to be able to do effective valve gear design, so that is a good thing.
Alibre pro will actually create the same data that Docsteader's does, and put it in a spreadsheet format. I find a spreadsheet easier to use than anything, and I use the KISS formula (keep is simple).
I have discovered two programs other than Docsteaders that will do valve gear design, but again, they are undocumented, and I prefer to just program my own spreadsheet so that I understand what formulas are used and also to preserve, document and publish those formulas so that others besides those three guys can fully understand valve gear design.
I would like to see your program comparison.
Pat J
Dan Rowe
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Pat,
Thanks for the formula however with out the defination of the variables it is not possible to use it corectly.
If you could give us the name of the book it would be helpful so we could read the source material and be able tp properly apply the formula.
Dan
Thanks for the formula however with out the defination of the variables it is not possible to use it corectly.
If you could give us the name of the book it would be helpful so we could read the source material and be able tp properly apply the formula.
Dan
J
JorgensenSteam
Guest
Here is my spreadsheet.
I have created several different versions of this, and I am not sure if this is the latest and correct one or not.
I have to go out of town again, but I will check the version when I get back.
You should be able to see where I am going with this sheet, even if it is not the latest one.
Pat J
Edit: The spreadsheet is too big to load onto HMEM. I will have to put it on CSEE.
http://www.classicsteamengineering.com/index.php?topic=423.msg1853
I have created several different versions of this, and I am not sure if this is the latest and correct one or not.
I have to go out of town again, but I will check the version when I get back.
You should be able to see where I am going with this sheet, even if it is not the latest one.
Pat J
Edit: The spreadsheet is too big to load onto HMEM. I will have to put it on CSEE.
http://www.classicsteamengineering.com/index.php?topic=423.msg1853
hi,
very nice spreadsheet, thanks to share. The valve travel is indeed the correct way to set the steam distribution, and particularly its symetry (or lack of for short rods). the Zeuner or Reuleaux diagrams are approximate, and does not take into account rod angularities. I did a similar spreadsheet a few years ago, you can have it here yet in french (I can translate if you are intersted in.)
http://ti1ca.com/flk9ra7o-distrib-vapeur-distrib_vapeur.xls.html
Zephyrin
very nice spreadsheet, thanks to share. The valve travel is indeed the correct way to set the steam distribution, and particularly its symetry (or lack of for short rods). the Zeuner or Reuleaux diagrams are approximate, and does not take into account rod angularities. I did a similar spreadsheet a few years ago, you can have it here yet in french (I can translate if you are intersted in.)
http://ti1ca.com/flk9ra7o-distrib-vapeur-distrib_vapeur.xls.html
Zephyrin
J
JorgensenSteam
Guest
Zephyrin-
I was able to open your spreadsheet.
That is a great piece of work you have there.
I like the oval diagram, and the indicator diagrams are very nice for forward and reverse stroke.
I like my displacement diagram better.
I never thought about generating indicator (forward and reverse stroke pressure) diagrams with a spreadsheet, but I did have thermo in school, and am familiar with the pressure/volume relationships.
A diagram from an indicator attached to an actual steam engine may vary from the theoretical diagrams due to worn parts, broken piston rings, wire drawing, etc., but the theoretical diagram would be very helpful in balancing the power between the forward and reverse strokes.
My spreadsheet is a first attempt, and is still in very crude form.
I think I can make is much better, but have not had time to revise it.
I would like add a plot for both the velocity and accelertion of the piston, to get a better feel for forces, and when the piston speed and accelertion is max and min.
The acceleration would just be the slope of the velocity plot at any given point.
The velocity drops to zero at TDC and BDC, as would acceleration.
Acceleration would be maximum then the velocity line has its maximum slope.
Thanks for posting your sheet, very interesting.
Luckily French is very similar to English, and I can pretty easily read the text.
Pat J
I was able to open your spreadsheet.
That is a great piece of work you have there.
I like the oval diagram, and the indicator diagrams are very nice for forward and reverse stroke.
I like my displacement diagram better.
I never thought about generating indicator (forward and reverse stroke pressure) diagrams with a spreadsheet, but I did have thermo in school, and am familiar with the pressure/volume relationships.
A diagram from an indicator attached to an actual steam engine may vary from the theoretical diagrams due to worn parts, broken piston rings, wire drawing, etc., but the theoretical diagram would be very helpful in balancing the power between the forward and reverse strokes.
My spreadsheet is a first attempt, and is still in very crude form.
I think I can make is much better, but have not had time to revise it.
I would like add a plot for both the velocity and accelertion of the piston, to get a better feel for forces, and when the piston speed and accelertion is max and min.
The acceleration would just be the slope of the velocity plot at any given point.
The velocity drops to zero at TDC and BDC, as would acceleration.
Acceleration would be maximum then the velocity line has its maximum slope.
Thanks for posting your sheet, very interesting.
Luckily French is very similar to English, and I can pretty easily read the text.
Pat J
Dan Rowe
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Pat,
Nice spreadsheet and I had considered doing a cad based solution to draw the oval or ellipse version of the plot so I could compare it to the plots made by Dockstader's Stephenson program.
No doubt about it plotting the movement of the valve and the piston is more accurate then a Zeuner diagram as normally shown. All of the well known diagrams had a way to apply the angularity of the connecting rod using a more complex form. This is what I think is shown on the page of Klein"s book in reply 29.
I have added page 31 of the book to this post.
The points made by Klein were the the ratio of the eccentric throw to the length of the eccentric rod is small enough to neglect it. The other point is if the ratio of the crank throw to the length of the connecting rod was 1:8 or smaller ".....the valve setting obtained from Zeuner's simple valve diagram will give very satisfactory results practically."
One other point I want to make is we can use Dockstader's slip eccentric program to generate the curves for single eccentric engine. Slip eccentric is only a clever way to reverse a single eccentric engine with a slidding cam. The geometry is exactly the same as a nonreversing engine.
Dan
View attachment Design_of_a_high_speed_steam_engine[1] 40.pdf
Nice spreadsheet and I had considered doing a cad based solution to draw the oval or ellipse version of the plot so I could compare it to the plots made by Dockstader's Stephenson program.
No doubt about it plotting the movement of the valve and the piston is more accurate then a Zeuner diagram as normally shown. All of the well known diagrams had a way to apply the angularity of the connecting rod using a more complex form. This is what I think is shown on the page of Klein"s book in reply 29.
I have added page 31 of the book to this post.
The points made by Klein were the the ratio of the eccentric throw to the length of the eccentric rod is small enough to neglect it. The other point is if the ratio of the crank throw to the length of the connecting rod was 1:8 or smaller ".....the valve setting obtained from Zeuner's simple valve diagram will give very satisfactory results practically."
One other point I want to make is we can use Dockstader's slip eccentric program to generate the curves for single eccentric engine. Slip eccentric is only a clever way to reverse a single eccentric engine with a slidding cam. The geometry is exactly the same as a nonreversing engine.
Dan
View attachment Design_of_a_high_speed_steam_engine[1] 40.pdf
J
JorgensenSteam
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Dan-
I agree with most of your points, but as Don Ashton and others have pointed out (if I recall correctly) ignoring the angularity of the eccentric rod does produce a significant and measureable error, and a surprisingly large error.
I think Don said that the designers from the 1800's ignored eccentric rod angularity because they did not have computers, not because it did not introduce error.
The spreadsheet by Zephrin is quite good in that it shows how to do the oval plots and the pressure diagram, and also shows that you can use a spreadsheet to replicate most of Docsteaders program. It should be noted that the actual pressure diagrams from an indicator would never be flat across the top like Zephrin's plots, since you have pressure drop in the ports and passages, as well as some wire drawing (pressure drop) from a partially opened valve.
Worn piston rings, and other things can also dramatically change the shape of a theoretical pressure diagram.
Using the motion part of Alibre or perhaps some other 3D programs, you can replicate the dynamic motion part of Docsteaders programs, and also generate the same data.
I do like spreadsheets because I think they will ultimately allow publishing and documenting the forumlas that Docksteader has used and allow others to finally continue and expand his work.
Pat J
I agree with most of your points, but as Don Ashton and others have pointed out (if I recall correctly) ignoring the angularity of the eccentric rod does produce a significant and measureable error, and a surprisingly large error.
I think Don said that the designers from the 1800's ignored eccentric rod angularity because they did not have computers, not because it did not introduce error.
The spreadsheet by Zephrin is quite good in that it shows how to do the oval plots and the pressure diagram, and also shows that you can use a spreadsheet to replicate most of Docsteaders program. It should be noted that the actual pressure diagrams from an indicator would never be flat across the top like Zephrin's plots, since you have pressure drop in the ports and passages, as well as some wire drawing (pressure drop) from a partially opened valve.
Worn piston rings, and other things can also dramatically change the shape of a theoretical pressure diagram.
Using the motion part of Alibre or perhaps some other 3D programs, you can replicate the dynamic motion part of Docsteaders programs, and also generate the same data.
I do like spreadsheets because I think they will ultimately allow publishing and documenting the forumlas that Docksteader has used and allow others to finally continue and expand his work.
Pat J
Hi
Pat J :
I'm very happy that you have found something useful in my xlsheet, however I must underline that the pressure diagram rests only on an adiabatic reversible expansion of steam, easy to calculate on a sheet, but far from reality, and going further would be too harsh for my gray cells. It was a difficult (for me) exercise on Excel, a tool that I do not like (no way to do orthonormal graphs!) even if I like the results, namely the immediate changes in the diagrams upon changing data (data in red in my sheet). BTW we can do that with the Charlie's programs!
I found the Dockstader package quite useful, the kinematics is amazing. I don't knows how he did the pressure diagram, he kindly answered to all my mails, just saying that there is no thermodynamics in them... what else?.
Maryak:
after a check in a textbook on steam, the eccentric rod angularity is neglected in the Zeuner diagrams presented in my book, but a way to take it into account is shown. the piston position however is generally shown with this correction. I hope I have not lost my AAA rating,
Cheers
Zephyrin
Pat J :
I'm very happy that you have found something useful in my xlsheet, however I must underline that the pressure diagram rests only on an adiabatic reversible expansion of steam, easy to calculate on a sheet, but far from reality, and going further would be too harsh for my gray cells. It was a difficult (for me) exercise on Excel, a tool that I do not like (no way to do orthonormal graphs!) even if I like the results, namely the immediate changes in the diagrams upon changing data (data in red in my sheet). BTW we can do that with the Charlie's programs!
I found the Dockstader package quite useful, the kinematics is amazing. I don't knows how he did the pressure diagram, he kindly answered to all my mails, just saying that there is no thermodynamics in them... what else?.
Maryak:
after a check in a textbook on steam, the eccentric rod angularity is neglected in the Zeuner diagrams presented in my book, but a way to take it into account is shown. the piston position however is generally shown with this correction. I hope I have not lost my AAA rating,
Cheers
Zephyrin
Dan Rowe
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Gedeon Spilett said:
Zephyrin,
I totally agree that the kinematics in Dockstader's programs is amazing and so many types of gear are included.
Thanks for the information about thermodynamics in both your spreadsheet and Dockstader's programs. That is the one section that I have never found a use for. Radow's program uses the steam tables so it will be a bit closer to the real world.
As to how it was done in Dockstader's programs I can not say, but in Steam-Engine Theory and Practice by William Ripper a method is shown how to draw a hyperbolic curve on an indicator diagram. Two curves were drawn one starting the curve just before the exhaust port opens and one starting the curve just after cut off. This is one posibility of "what else".
Dan
J
JorgensenSteam
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I have been reviewing the valve gear program information I collected last year, and will post a summary here.
The major players in the valve gear program game are:
1. Charles Dockstader
Comments Pro:
Charlie has worked out his valve gear simulation program for probably more valve gear types than anyone else, and the width of his work is pretty much unparalleled.
Comments Con:
The downside to Charlie's programs is the lack of documentation concerning formulas and valve gear design in general, and so one is limited to just using the programs to verify an existing design, but not necessarily to produce a design good design from scratch.
2. Bill Hall
Comments Con:
Bill has created some EXE programs (executable programs, not spreadsheets) for valve gear design, and I find these difficult to use.
Comments Pro:
Bill does have additional material that documents valve gear design which seems to be very good.
3. Dr. Alan K. Wallace
Comments Pro:
Dr. Wallace has a program that is very similar to the one that Charlie Dockstader created.
Dr. Wallace also has an excellent written summary about valve gear design which is very helpful with getting the "big picture" of what you are trying to achieve with valve gear design, and which valve gear design lends itself to which type of steam engine application. I will post the text hear since it is "freeware", and is allowed to be shared.
Comments Con:
I don't see a spreadsheet version of Dr. Wallace's program, so like the other EXE programs, you can use the program, but you cannot change it, and you cannot see which formulas have been used for the different vavle gear types.
4. Don Ashton:
Comments Pro:
Don Ashton has published some great articles on valve gear design, some of which I am still studying.
Don has published two spreadsheets that I am aware of for valve gear design, and the beauty of the spreadsheet is that they are somewhat self documenting, in that you can generally see all the formulas that have been input into the sheet. This ability to see the formulas used is invaluable if you are ever going to fully understand valve gear and the geometry associated with valve gear design.
Comments Con:
I don't see where Don's spreadsheets will produce animation of the valve gear such as is found in Charles Dockstader's and Dr. Wallace's simulation and animation programs. Animations are nice as far as being able to visualize what is happening with the valve gear at any given time, but the animations do have limits.
If you read the comments by Dr. Wallace, programs that create animations show the animation in steps, and the animation is only as accurate as the data for that particular step. If the steps are large, then the animation will be highly inaccurate as far as what may be happening between steps.
My thoughts are that if you can produce accurate data for the valve gear, then you can feed it into a program to produce the simulation.
If you cannot independently produce the valve gear data, then you will always be limited to using someone else's programs.
5. Other valve gear programmers:
There are other individuals who have created valve gear programs, and these are similar to some of those mentioned above, but these programs may require registration and a user key, which I find to be a nuisance and unneccessary since the other valve gear programmers have put their work in the public domain as "freeware".
Summary:
So in summary, I will be studying Don Ashton's spreadsheets for valve gear design, since they are the ones that I can learn the actual formulas from.
The other programs seem to be limited to just verifying known valve gear designs, not necessarily designing vavle gear from scratch, and I am not interested in verifying a known valve gear setup, but rather a good approach to designing valve gear for any engine from scratch.
Pat J
The major players in the valve gear program game are:
1. Charles Dockstader
Comments Pro:
Charlie has worked out his valve gear simulation program for probably more valve gear types than anyone else, and the width of his work is pretty much unparalleled.
Comments Con:
The downside to Charlie's programs is the lack of documentation concerning formulas and valve gear design in general, and so one is limited to just using the programs to verify an existing design, but not necessarily to produce a design good design from scratch.
2. Bill Hall
Comments Con:
Bill has created some EXE programs (executable programs, not spreadsheets) for valve gear design, and I find these difficult to use.
Comments Pro:
Bill does have additional material that documents valve gear design which seems to be very good.
3. Dr. Alan K. Wallace
Comments Pro:
Dr. Wallace has a program that is very similar to the one that Charlie Dockstader created.
Dr. Wallace also has an excellent written summary about valve gear design which is very helpful with getting the "big picture" of what you are trying to achieve with valve gear design, and which valve gear design lends itself to which type of steam engine application. I will post the text hear since it is "freeware", and is allowed to be shared.
Comments Con:
I don't see a spreadsheet version of Dr. Wallace's program, so like the other EXE programs, you can use the program, but you cannot change it, and you cannot see which formulas have been used for the different vavle gear types.
4. Don Ashton:
Comments Pro:
Don Ashton has published some great articles on valve gear design, some of which I am still studying.
Don has published two spreadsheets that I am aware of for valve gear design, and the beauty of the spreadsheet is that they are somewhat self documenting, in that you can generally see all the formulas that have been input into the sheet. This ability to see the formulas used is invaluable if you are ever going to fully understand valve gear and the geometry associated with valve gear design.
Comments Con:
I don't see where Don's spreadsheets will produce animation of the valve gear such as is found in Charles Dockstader's and Dr. Wallace's simulation and animation programs. Animations are nice as far as being able to visualize what is happening with the valve gear at any given time, but the animations do have limits.
If you read the comments by Dr. Wallace, programs that create animations show the animation in steps, and the animation is only as accurate as the data for that particular step. If the steps are large, then the animation will be highly inaccurate as far as what may be happening between steps.
My thoughts are that if you can produce accurate data for the valve gear, then you can feed it into a program to produce the simulation.
If you cannot independently produce the valve gear data, then you will always be limited to using someone else's programs.
5. Other valve gear programmers:
There are other individuals who have created valve gear programs, and these are similar to some of those mentioned above, but these programs may require registration and a user key, which I find to be a nuisance and unneccessary since the other valve gear programmers have put their work in the public domain as "freeware".
Summary:
So in summary, I will be studying Don Ashton's spreadsheets for valve gear design, since they are the ones that I can learn the actual formulas from.
The other programs seem to be limited to just verifying known valve gear designs, not necessarily designing vavle gear from scratch, and I am not interested in verifying a known valve gear setup, but rather a good approach to designing valve gear for any engine from scratch.
Pat J
J
JorgensenSteam
Guest
This is a good summary of the goals of good valve gear design, written by Dr. Alan Wallace.
This information is freeware.
Dr. Alan's EXE programs are worth looking at also.
I will try and dig out the link to his freeware programs and post here.
Pat J
View attachment WVALVE.TXT
This information is freeware.
Dr. Alan's EXE programs are worth looking at also.
I will try and dig out the link to his freeware programs and post here.
Pat J
View attachment WVALVE.TXT
J
JorgensenSteam
Guest
And here are a couple of spreadsheets by Don Ashton.
They are freeware.
I don't pretend to understand them yet, but am studying them.
I willl also try and dig out the link to Don's valve gear site, and post here.
Don has some superb publications on valve gear design, such as his paperback book "Design Proceedures for Walschaerts' and Stephenson's Valve Gears".
There is also an article available from H.S. Gowan (1975) that contains some of the same information that Don Ashton published in his paperback.
Pat J
Edit: I am bumping into file size limits again on HMEM, and will have to put these sheets on CSEE.
http://www.classicsteamengineering.com/index.php?topic=423.new
They are freeware.
I don't pretend to understand them yet, but am studying them.
I willl also try and dig out the link to Don's valve gear site, and post here.
Don has some superb publications on valve gear design, such as his paperback book "Design Proceedures for Walschaerts' and Stephenson's Valve Gears".
There is also an article available from H.S. Gowan (1975) that contains some of the same information that Don Ashton published in his paperback.
Pat J
Edit: I am bumping into file size limits again on HMEM, and will have to put these sheets on CSEE.
http://www.classicsteamengineering.com/index.php?topic=423.new
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