The best demonstration of Walschaerts gear I've seen on RU-vid, explaining the basics an the nuances clearly and concisely with well presented graphics. Well Done.
Took me a long time to be in the mood to watch this, but that gave me the opportunity to watch this _and actually learn something._ This is a very well put together presentation with clear explanations of everything, very easy to follow visuals, and a great narrator. Looks like I'll be giving the steam engines in train simulator another try.
This has been the best demo/explanation of the function of the combination lever that I've ever seen. Reading about it has never clicked for me. Thanks
Fantastic video! I have always been fascinated by steam engines since I was a little kid, and they were still in operation on a limited basis. I would make drawings of them from the illustrations in the Encyclopedia Britanica (many decades before the internet!). I'm 76 now and yes, I went on the be a mechanical engineer. You could have guessed that when I was seven or eight years old!
Excellent explanation. Looking forward to the Baker gear. I've been fascinated by these machines since watching them growing up. They seem to be alive, unlike the diesels or electrics. Really enjoying learning the details of how they work.
I've always been interested in trains and steam locomotives. I assumed the workings of valve gear was beyond my comprehension. This video proves that good teaching can bridge the gap between what we currently understand and the next level. So many of my teachers were not up to scratch. As commented elsewhere, an excellent video.
When I saw this video was over 45 mins. I wasn't sure I could sit through it. After viewing, I'm prepared to watch it over and over now. Fantasic naration, 3D and animation and above all insight into valve gear motion. Thanks a lot.
This is a magnificent explanation that is easily the most comprehensive and clear description of an otherwise mind boggling mechanism. I have been in awe of the Walschaerts Valve Gear (like many) with its almost hypnotic motion on a running loco; it speaks volumes of the brilliance of its inventor. I've often wondered how long it took to work out the entire design from inception, and the progression of development must have been an enlightening experience. Many thanks for the hours of work in developing this fantastic tutorial.
Your presentation is almost textbook that was used in my Dad's day when he was working as a design engineer in the late 30's & early 40's. He tried to explain all this but didn't possess the communication skill that you have. 'Course the graphics help a lot, but your delivery is clear as can be. Thanks. liked&subbed immediately. P.S. 2-8-4 is my favorite wheel arrangement.
I was recently gifted a collection of International Correspondence School books (distributed in the 1930 - 1946 timeframe). Five of the textbooklets addressed valve motions and all were structured exceeding well - as there should be for an instructional book. This video is the moving version of those books; structured almost identically. Really well done - with all of the corner cases covered!
Ever since my first toy train set I have been fascinated by the mention of Walschaerts Valve gear but it has never been clearly explained Thanks for enlightening me.
I've been looking forward to this tutorial for some time now. Both this and the previous video have given me a better understanding of steam locomotives. Thank you so much!
An excellent description. I could imagine the invention, testing, development and refinement stages evolving as the design progressed and the improvement of performance as the whole thing came together. Taking us through the stages as you did was a brilliant idea and beautifully done. Congratulations.
Excellant explanation. Doing into the tiny details of how the angles and circular motion are considered. Certainly an ingenious device. And your graphics are great at helping me to understand.
Thank you so much for this. I was brought up with steam as we had a steam traction engine and 2ft guage railway at home (UK). I had a pretty free hand in operating them as I grew older but always with some oversight. My uncle told me about the function of the reverse lever and how to 'notch it back' as speed grew because less steam was needed at higher revs. I got it in terms of how and when but never understood the mechanism of valve timings etc. Now thanks to you, 55 years later I do!
That was a verry impressive presentation. It provides so much clarification of the different elements of this system. When I first studied mechanical engineering as a student, it was a topic in a textbook, the teacher had a wooden model to help provide clarity. Again, brilliant presentation.
This was a brilliant example of the mechanics. You hear things,and(start) to pick up on the main idea over the years. But nothing was left out here. I knew what volumetric pressure was,but here’s the precise application of it for a steam locomotive. Thanks for posting this-many thanks!!!
Very nicely done! Just stumbled across this 8 days after you released it. Earned ya a subscription! Now I know what to look for when I set up my Pacific!
Thanks Dan... a magnificent piece of work. I thought I understood the main ideas of Walschaerts valve gear, but clearly I had missed some key points. Great job! Amazing what those mechanical engineers did without calculators, CAD systems, 3D modeling, etc.
Wow. There's enough information here to make your head spin as much as the wheels! Might take me a few re-watches of this to grasp everything to the fullest extent, but at least it's all here!
Just watched the part 1 and part 2 videos, and I loved them! I learned a lot. I can't wait to see part 3 and hope it doesn't take two years! Another video that would be interesting to add to the understanding of steam engine performance would be "indicator diagrams" showing how pressure in the cylinder is affected by differing valve cutoff positions. I am an engineer of internal combustion engines and it is different to think about steam engines, where the cylinder pressure is about equal to boiler pressure, unless the valve event is set to cut off steam admission at different points in the stroke.
Wonderful explanation. It could explain the force of the steam when it enters the piston and how a small piston like that of locomotives can support so much weight.
Thankyou for making this excellent video resource. Us Model Engineer folk have many resources available to us for valve gear, the late Don Ashton’s work being one of the best, but for people like me, mathematically heavy! The only explanation of how to find how long the Union link needs to be in relation to the combination lever vertical and piston mid stroke was very interesting. Something I have previously missed. Thankyou again.
Possibly the best video explaining this. Good work, even though I was bored at times because I am familiar with mechanics and designed something simpler about 25 years ago during my mechanical engineer study. EDIT: We call this valve gear Heusinger. It is practically identical, designed independently by a certain Mr. Heusinger.
Great explanation and animation. I didn't know anything about locomotive valve timing. Next trip to the rail museum, I'll be taking a closer look. Thanks!
I loved this, I hope to see the next part soon. I would love to see this done for poppet valves like the type used on the L1 Hudsons, and a full work up on Stevenson valves.
It's a small thing in railroading, especially in the N. American environment, but the name of the inventor is pronounced 'VAHL-skaretz', sounding like 'scared' but with a 'ts' sound at the end. That aside, I really appreciate this comprehensive description of Walschaerts valve tear. It is most informative, and VERY well done.
"MOIN" as we say here in north germany... or as jock spoken south scandinavia. on the one side so interesting to me, how small our hobby world seams to be, that someone like you have entered my chanal. thank you for that. on the other side a lot of respect to your video of explaining professionally steam locomotion technology, says the german vehicle engineer and welding engineer. TO OUR HOBBY, all the best and more please....
I had an antique toy steam engine as a kid 60years ago on which both the piston/cylinder and the valve assembly pivoted and always pointed directly at their rotating connection points on the flywheel. Thus, there was not the angular "error" in either the push rod or the connecting rod strokes. Midpoints of the strokes acted concurrently with the piston and valve midpoints. (Actually, the pivoting motion of the piston/cylinder was mechanically linked to the valve actuator in such a way as to provide the necessary 90 degree lead of the valve action over the piston action.) It was brilliantly simple. Sadly, the toy vanished in one of several moves since.
This is a brilliant video. Even if you "know" how the valve gear operates, this addresses the sort of things you don't think about but were crucial when Walschaerts, or Heusinger (which is how we know it here) invented the beautifully simple and effective motion. - Just want to say, there was a lot of locomotives with outside Stephenson's and especially Allan's valve gear in Austria - Hungary. I'm from Czechia and when you said it, I was like, no, this is normal and does fit quite well? :D
Because I live in a country that abolished steam locomotives before me born and we as a society do not support such history, it is really my first to see such detailed explanation for the connecting rods between the cylinders and wheels. I would urge and if necessary try to help but I am not any export that you as a community need to make such detailed and yet simple lectures for every aspect of steam locomotives design and maintenance in whatever aspect you think about. Probably at some point we might form a group to design steam locomotives much better and efficient.
These videos have been very helpful. I'd love to see more information on the frame, suspension, pilot and trailing trucks of these more modern steam locomotives (which I know isn't the most interesting or exciting topic 😄). I'm really want to understand more about what the cradle does, and how the rear weight of the cab and firebox is distributed to the trailing truck (it has something to do with "heart rockers" I believe). I recently bought a copy of the 1925 Locomotive Cyclopedia, which has tons of knowledge, but it's still hard making sense from the technical drawings. I'm debating on purchasing UP 844 1.5" scale model drawings to study and understand more about every nut and bolt of these machines. The 7.25" gauge model is so large, the designer even included prototypical frames and suspension. Studying live steam locomotive drawings has been helpful as their designs tend to be simpler.
Me too: excellent explanation! Thank you. :-) Slight suggestion: when you say something that amounts to "Here we see...", then I must scan my big screen with the speed of an old cathode ray to find where "here" is. The explanation might benefit from some lead-in "cursor movement" to the place of action.
This was awesome! A beautiful explanation of Walschaerts valve gear, well demonstrated at that! The only thing I'd say about your presentation is the fact that I don't think C&O Kanawhas had Walschaerts, but instead Baker, as all Lima-built and most 2-8-4s in general did. Still, this presentation does a great job making the Walschaerts look right at home on this iron horse!
When the video first started, I noticed the same thing. Then @ 1:10 he addressed that elephant! You hit the nail on the head with your comment that the Walschaerts looks at home - a credit to whoever did the graphics for this. Take it easy, @Railman!
"it would be impossible to have two separate eccentrics on an outside valve gear". It was done at least once, with a single experimental example of an LMS Stanier Black 5 (en.wikipedia.org/wiki/LMS_Stanier_Class_5_4-6-0_4767). It was preserved and can still be seen.
I watched both episodes a lot earlier, but never commented on them untill now. These are superb videos when it comes to explaining locomotive valve gear and valves! I am very invested in this subject as of late and can't wait for more installments! Can we expect more valve gears like of the dual eccentric type (Allan & Gooch) or should we look forward to similar valve gears to Walschaerts-Heusinger and Baker? Will poppet/cam valve gears also be discussed? i.e. Caprotti, Franklin, etc.
One more syllable please: Kanawha, years ago I worked in the Capitol of West Virginia in Kanawha County. Had the pleasure of watching these engines pull the fall foliage train.
Walschaerts Valve gear, a mechanical analog computer. good 'splainin, too. steam locomotives are some of the most impressive machines ever built . . . everything hasapurpose . . . everything moves!
Some more advance related subjects that would be nice to cover. For compound locomotives (e.g. mallets) is there anything to prevent the condition where the high pressure cylinder is in exhaust stage, while the low pressure cylinder has its intake blocked, or is some kind of buffer/surge chamber used to handle this ??? In the case of of locomotives with 3 steam cylinders, how is the center cylinder power and control linkages connected to the locomotive drive chain ??? Some locomotives had provisions for a 'booster', a low speed steam motor that can be located on the locomotive trailing wheels, or on one of the tender wheels to provide an addition 'boost' to start a heavy train moving from a full stop. I have not seen anything on RU-vid on how these 'boosters' operate. Can something be produced to cover this ???
Makes me wonder too, ALCO setup locomotives this way. Found this really cheesey movie titled Boxcar Bertha, was filmed on the Reader RR in Arkansas. They were running their ex millitary 2-8-0 and the I quickly noted its indirect motion.
Great video! I have one question though - is there any advantage in using indirect motion? If it was used in some locomotives, then their designers must have chosen to do so for some real reason and not just wanting to be different.Were those locomotives expected to run backward more or something else?
Think on switching locomotives, operating in ports, depots and railway triage. They move a lot back and forth, at low speeds (so a breaking linkage won't lead to major damage), but they move backward at least as much as forward (if not more). For them, indirect motion may be a viable option.
Ahhh but, you didnt mention what is REALLY going to happen SINCE the hanger on THE OPPOSITE SIDE isnt likely to break also. Major opposite motions!! I think something similar is what happened to the NYC loco years ago - and the side rod looked like a pretzel. There is a UTube but danged if I can find it again or I'd post the link.
If I was a betting man, probably not. The Chesapeake and Ohio never used that to my knowledge, and this is their historical society. I would expect baker, and Franklin type A and type B poppet valves to be covered.
Now you can address side rod accommodation of independent driver axle motion over a lump in the track when roller bearings are used. I maintain roller bearing drivers clearance’s cannot accommodate independent axle motion vertically. Eh?
I asked this question in a different forum; someone did the math for a given wheel spacing (rod length) and driving wheel elevation difference -I think I specced 5' wheel spacing and 1" rise. The person concluded that the additional length could be accommodated with an almost imperceptible length change that could be supplied by the slop in the system - even roller bearings. I.e., not much clearance on the crankpin / bearing surfaces (pin / race / roller / race / rod or pin / floating bushing / busing / rod) *could* be enough. I had to trust his math, but the logic seemed reasonable.
IN THE USA PERHAPS !!! Of course the "Introduction" should clarify the situation explained to "Most widely used in the USA", so NOT including the rest of the planet, where even Germany used a modification of the "Walschaerts" (a Belgian designed valve gear) known as Heusinger !!! Something Americans seem to forget is that the Internet is World Wide !!!! Maybe I should also add, that Walschaerts was well suited to Express passenger locos but Mixed traffic & Freight designs were likely to perform more efficiently if fitted with "Stephenson Link" valve gear, as proven by the CME of the Great Western Railway (UK) George Jackson Churchward by 1910 !!!!
Europe is not the world, either. Stephenson's Link, post 1910 was too heavy for the sorts of piston thrusts developed by North American locomotives - and thereby the more onerous valve movements required. As more part numerous than Walschearts it was also more expensive, regardless of where in the world the locomotive was based.
That explains why the LMS 8F and BR 9F use Stephenson then, and not Walschearts. Oh, oh wait, they don't. They use walschearts. Maybe there was a good reason for that...
@@felixtheswiss To an extent. Labour problems from the 1880s onwards caused many a colony to build local, or shop American. I've never heard North British described as European before!
Well here it is known as Heusinger gear. Got the name Walschaerts during WWI to hide the German origin. Walschaerts was 2 years after Heusinger " inventing" this gear.
