Timing Walschaert Valve Gear on a live steam locomotive
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- Опубликовано: 6 сен 2024
- Tutorial on setting Walchaert Valve gear on a live steam locomotive. Details how to locate dead center, set the eccentric crank and rod, and set the valve on the valve stem.
In all of the instructions I have read and been told, when setting valves to always move the engine in the same direction. If the engine must be brought back it should go more and then come back so all slack is out of the motion. This is not criticism just an added observation. I helped set the valves on a 17 ton loco and that is the way we did it.
I bought a 3 cylinder loco a year ago, which didn’t run. I’ve spent that year overhauling the entire thing, with only a small improvement. Your video prompted me to investigate as I assumed the return crank would be fixed and set in stone! It turned out it wasn’t and clearly had a life of being messed about with by ignorants. Fingers crossed and thanks for your easily watchable instruction.
Still learning, and bracing myself for centre cylinder complication, as it relies on a conjugated linkage from the outside two?
Jay, Finally Someone who can explain this very importante process! Thanks so much for making this very informative video, I drove full size Steam Locomotives here in Queensland Australia for work, and always wondered why one engine would perform better than another. Timing is everything. All our Engines in Queensland Rail are Left leading Inside admission piston valve Walsharts with Essentric set 90° behind the crank, except for a Baldwin 2-8-2 McCarthur which is set 90° ahead due to the forward motion being derived with the die block being in the top portion of the quadrant Link. Thanks once again. Cheers Adrian
I have a 5" engine in re build and I was wondering how the valve timing was set. This video is excellent for simple explanation of how to set the valve gear. Thank you for posting and happy steaming.
Thanks for the tutorial Jay. I'm off to the shop to adjust the running gear on the Mogul.
Thankyou that was an excellent overview of setting up the valve gear. I hope I am able to do this soon.
Yaay! Im glad I found your video =) Im nowhere near this level of my journey about learning bout steam locomotives ... and one of the more interesting / mysterious things as of late is how the valve gear and cutoff works ... so I thank you for your very well explained and visual video, Im also very glad you visualized cutoff =) ... it was hard for me to picture based on just reading about it =P
Excellent description of how to set the valve gear. I'm glad I found your video.
Quite interesting, maybe you can do video how this valve gear works and how to design it. I had a few questions, but when i was thinking about them for a longer time, i think i answered them. Just to check:
- Eccentric pin is approximately 90deg from driving pin, but not necessarily exactly the same. Difference is caused by eccentric rod usually going little upwards.
- Combination lever is there to create phase offset other than 90 degrees between valve opening and piston position, so valve may be already closed when piston is in the middle position.
Anyways ... it's mostly mental exercise, steam engines are fascinating and to understand principle, i needed to read 30 pages and it was simplified by assuming that all movements are sinusoids. Your video clarifies at least some details.
Sir you gave excellent information than another videos
Thanks Jay , very informative ! I have a 3.5" gauge Atlantic and it runs like a top now I cured a few issues .
Want to check in the timing and adjust it . 👌
Finally a video I can understand, thx a lot
I assume for a piston valve, this is backwards? Or more specifically, the eccentric crank is set 90 degrees opposite?
Not being able to see into the valve chest will probably make this an entertaining event... I acquired a pacific with true piston valves on it and I need to reassemble it to see what how everything is going or if I need to remake a bunch of stuff...
Great clear descriptions of what's going on and why. Thank you!
Excellent tutorial Jay. This will be very useful for me on my loco build. Thank you.
On a 3½ or 5 inch loco, The downside of cutting back the steam is you now have less exhaust to draw gases through the boiler from the fire in the firebox meaning less air being pulled through the fire which we need to excite the combustion process.
My question is, should there to a downward tension on the valve block or does it just float ?
Its true that running the engine cut-off send less exhaust up the stack, hence less draft for the same power setting. You can adjust/reduce the exhaust nozzle size to compensate for some of that if desired. It will increase the backpressure, but still reduce overall steam consumption. The slide valve block is held down by steam pressure in the chest.
Jay, this is an excellent video, thankyou for making it and sharing.
very well explained, answered a lot of questions i have allways wanted answered. glenn heaslip australia.
Wow! Very impressive and educational! Thanks for the video and best of luck!
I would like to get the plans for one of these.
In a full size steam loco, do you have the same setup each side, and if so how are they co-ordinated. This is something i have thought about for quite a time, I look forward to your reply some time thank you.
nottyash100 I think they do
Yes both sets of pistons have this running gear.
The shaft that the reversing lever is mounted to turns the other one on the other side.
Since the position of the piston doesnt affect the radius movement,
It is a full size locomotive , just a small one ☝️
Thank you very much sir!
Forgive me but is "the pointer" aligned with the center of the axels? The video didn't say specifically but the location seems right.
It actually doesn't matter where the pointer is. Its simply a reference marker. Any convenient location will do. All that matters is that you mark the points using the method described so that you can come back to them as you work through timing the valves.
Many thanks sir! Yes, thinking about it a bit more the marks should be 180 degrees apart of whatever location "the pointer" was picked.
I've got spool valves and I got another good tip yesterday. Attach pieces of hose from the cylinder drain cocks to a bucket of water and lightly pressurize the boiler with compressed air. Then slowly move the spool valve forward or aft until bubbles of air indicate that the valve is opening. Not wanting to loosen the nut holding the spool valve against its collar, I cut a slit in the end of the valve rod so I could make fine adjustments with a screw driver.
Hopefully I make things better rather than worse for my 0-4-0T.
1. Very nice presentation - It's unique in that you average the front n rear dead center
positions with the marking pointer. That would accommodate any slack in the valve gear
connections. Focus was excellent. Wished your voice volume was a bit louder at the
beginning of the video. Setting the vol control at the screen bottom to max and another
at the bottom bar of my desk top to max didn't help much. But after the initial portion,
the vol was OK but still had to keep both controls high.
2. Walschaerts Valve Gear Design Process -
a. How did you design your valve gear? Geometrically or Algebraically (w equations)?
b. What source did you use?
I started out with reading:
i) Walschaerts'Valve Gear, Henry Greenly
ii) Locomotive Valves and Valve Gears, J H Yoder n G B Wharen
iii) Docstaeder's software on-line
iv) D L Ashton's Design Proc. for Walsch n Stephenson's Valve Gears
i) was the easiest to read but not much helpful to design the reverse gears
ii) was more detailed w Geometry
iii) the reverse gear parameter values were poorly explained and without legit values,
the simulation animation began to falter. the entire software became useless
iv) Ashton's tabular parameter entry parameters were not explained well and was
useless, including the book which was too over complicated (hey, i was a math
minor in college) and his text was hard to understand
I've also put out a help request at chaski.org web site regarding my finding on the Docstaeder's problem but no one seems to know how to over come the defect:
www.chaski.org/homemachinist/viewtopic.php?f=8&t=98490&start=48
Your advice would be appreciated,
Dor_Crank
With outside admission (this engine has D valves which is outside admission) the motion through the lead and lap lever is opposite of the motion of the piston so the radius rod (which acts as a pivot in center) is between the valve connection and the union link. With inside admission (most spool valves), the movement of the piston through the lead and lap lever is in the same direction as the piston so the radius rod connection is above the valve connection on the radius rod.
The length of the lead and lap lever is determined by knowing the stroke of the piston and then the valve will move 2x(lap + lead). Lap is how much the valve overhangs the ports when the valve is centered. Lead, as said here, is how much the valve is open on dead center. If the valve overhangs the ports (lap) by 1/8" and has 1/16" lead, the valve will move 2(1/8+1/16) = 3/8". The positions of the holes on the lead and lap lever are determined through geometry to move the valve in proportion to the piston's stroke.
The Union link length needs to be set so that when the piston is centered and the valve gear is in center that the lead and lap lever is vertical (and the valve is also centered) so the lead and lap lever will have even swing about the vertical plane. This will produce even cut off between the front and back side of the piston.
The placement of the link needs to be determined as far as where its frame will fit. The radius of the link will match the length of the radius rod. The foot of the link (on the bottom) is set behind the the center of the curved radius to even up the swing of the link about the vertical plane.
The throw of the eccentric crank is NOT the throw of the valve, but is set greater. The link is a lever and the eccentric rod connects at the bottom of the link and the radius rod/link block may be about 2/3rds the distance away from center as the eccentric rod connection at the foot of the link. To obtain the desired maximum valve motion, the foot of the link needs to travel more which means that the eccentric crank is set to a larger throw than the valve will do. This is also determined by geometry.
great vid! Thanks for sharing👍
Are you by any chance located in the North East U.S.?
Great Video!
Very interesting and informative video. Thanks for sharing.
I note that you talk about the % of the stroke but show the % wheel rotation, I thought % cutoff is the % stroke at cutoff and % wheel rotation is not the same thing, is that right? Great video though and I learned a lot from it, thanks.
That is correct. Due to the angulation of the main rod, % cut off is not the same as % wheel rotation. When the crank pin is at the 6 and 12 o'clock positions, the piston is not centered but is to the rear of being center. When the piston is half way through the stroke, the crank pin is before the 6 o'clock position (like 5-5:30) and and after the 12 o'clock position (like 12:30-1)
To determine % cut off, the length that the piston has moved is divided by the total stroke length.
Maybe I can use an adjustable tie rod from an RC car for this?
Very informative
Thanks for this. This was very informative. I am into smaller gauges (Gauge 1), but the concept is the same. What about the difference between the two sides? Do you know how this process changes for a simplified valve gear. This is yet again "common" on G scale and Gauge one, where there is no reversing lever, but a separate reversing valve.
I'm not very familiar with the G scale simplified valve gears, however setting and working from the correct dead centers would still be applicable, as would the 90 degree offset of the crank from the crankpin. Right and left sides operate completely independent of one another. The only relationship between the two is the 90 degree offset on the axle.
Thanks.
@@jmonty1201 do you still have the locomotive I'd like to see if you are interested in selling it or showing us if it running
Great information thank you sir. I require more details. Can you provide me?
Sir. I want to know the function of combination lever
its function is to keep the top and bottom piston in the correct timing to allow steam into the bottom piston
@@crazynachos4230 Thank you sir.
@@talukdarchinmay you're welcome
@@crazynachos4230 Can Engine works without this Combination Lever
@@talukdarchinmay no it's every part on the engine is absolutely necessary or everything would be out of phase or just not even work
Put the cap
Very Informative. Thanks.
But why the video is categorized as Comedy instead of Educational
where can I buy this engine can you post any links ?
Friends Models in Massachusetts sells the drawings and castings.
Well it appears that he doesn't respond.
Can u gift me a copy of the locomotive plz?
this is so hard to understand ;-;
Trainz Marcel you’ll get it. Just don’t give up!