In today's video, we take an in-depth look at the numerous ball and slip joints in a mallet type locomotive's plumbing that allows its front drivers to pivot, and still be supplied with steam when taking a curve.
Can honestly say I’ve never seen a video on this subject. You are definitely not afraid to discuss some of not so well known topics for your Viewers. Thx! 👍🙏
Big Boy and Challenger were “simple” articulated engines, and did not reuse the steam from back to front. They, and the 844 Northern, also had their throttle at the head of the superheater way up at the smoke box rather than in the back of the boiler at the classic “steam dome”, meaning throttle changes caused instant response at the cylinders rather than there being a delay of several seconds between the throttle movement and then cylinder action like in most older locomotives in general. “Compound” articulated locomotives uses the steam twice, once at high pressure in the back then again at lower pressure in the front, hence why the front unit cylinders on those kinds of locomotives were much larger, even if re-heated first the front cylinders would still be a bit larger as re-heating could not return it to the original pressure in the limited time it had. Lastly, Big Boy and the 3900 series Challenger used roller bearings in their construction which let them run faster for longer with less damage to the track as usually caused by the older extra-heavy front engine units of the compound types when above 25 mph. They really are amazing machines.
@@Southern_Plains_Railfan I believe it was found the oversized low pressure cylinder created too large of a hammering effect as locos in general grew in size.
Great explanation, I have several old Baldwin and ALCO catalogs that go into great detail about the flexible steam joints. You nailed it. One of the things driving the use of low pressure steam exhausted from the rear high pressure set of drivers on a Mallet to the low pressure front cylinders was that is was easier to keep the low pressure steam joints tight. Eventually they figured out how to make these connections work for high pressure superheated steam in the 20s opening the door to high speed superpower simple articulateds like Big Boy and the Alleghenys. You mention that most railroads are relatively straight and the curves are gentle. Some great examples of super flexible simple articulateds can be found in #50 and #51 from the Uintah Railroad in Colorado and Utah. They were successfully traversing some of the tightest and steepest rails in the country actually displacing Shay geared locomotives. 92 foot radius curves and 7.5% grades! Baldwin described these engines as designed for the most severe operating conditions imaginable in their literature.
Really great video, excellent you included and did some quite fancy pants artwork with the diagrams, and went very in depth regarding what the joints actually consist of. That was a big almost backward step with UP's Challenger and Big Boy series: they stuck with the rather chaotic mess of joints, whereas Lima had eliminated over half those joints, producing a spectacular increase of efficiency compared to the other two. Both Challenger and Big Boy types had lazy exhausts as a result of fairly poor exhaust efficiency. I'm pleased you stuck to just one form of articulation too, and didn't extrapolate further into the articulation minefield or even into what defines a mallet. Great viewing :)
Thank you, I'm glad you enjoyed the video! I never knew that the Big Boys and Challengers had those kinds of problems. I wonder why ALCo didn't take a page out of Lima's book when designing their engines.
@@Southern_Plains_Railfan thank you! A lot of it was the fact that it was an Alco/UP design collaboration, most of it was the timing: Lima's Allegheny came out in '41, same as the Big boy, so there wasn't really any time for any crossover. The Allegheny had a single steam joint at the front engine pivot, routing the plumbing through the main frame directly to the cylinders, hence only one joint to the big boys 4 pivots and 2 slides. If you have a look at videos of the UP locos you'll note the very lazy exhaust almost floating down the boiler barrel. Hard throttle not so noticeable, but just different designs, one being more of an advancement. It's more telling that UP wanted F units rather than buying more #4000's. I could add that theres an awful lot of factors in any loco design. The drivers of those Chapelon masterpieces needed a veritable engineering degree to get the most from their locos, and that early 8 cylinder vauclain simple compound mallet tank was fraught with design issues
Great job explaining this, for some reason I never even thought about it 😂I actually live really close to where that picture was taken at 2:20 and saw the big boy that same day, cool!
1:34 Traditionally Mallet-Type Locomotives were Compound Locomotives, where the Steam gets used up Twice, as depicted here. However, there are some instances of Simple, Single-Expansion Mallet Locomotives, where the Steam gets used only Once, with all Four Cylinders having the exact same Size, and all Four feeding into the Blastpipe inside the Smokebox. A famous example of this would be the Union Pacific Big Boy Locomotive.
1:20 its basically an open diff, if one set starts spinning then all the steam pressure will go to that set because its the path of least resistance. One leaky valve is all it takes.
There mist be some lateral movement permitted somewhere? A single pivot would not allow the loco to go through compound curves like points. Does anyone know anything about this?
@@Southern_Plains_Railfan I get that but I'm talking about the bogie itself. The pin must have lateral movement (or the axles) in order to accommodate compound curves?
Too Bad There Were No Actual Old Photographs Available Of The Connection And Pivot Points Of The Frameworks. As Well As CLOSE UP Piping And How It Must Have Been Located Under The Long Boiler Tank. There Were Old Photographs Taken Of A Steam Locomotive Entire Upper Boiler Section Being Lifted High Off Of The Wheels And Framework At The Salamanca New York Shop Of The BR&P, That Also Used Malley Locomotives During The Early Years Of The 20th Century, And Are Very Impressive To See Indeed. However Your Explanation Answered Most Of My Curiosity About How These Massive Machines Operated. Thank You...
Yeah, I searched around for a photo of the pivot points, but as you can see I didn’t have any luck. That’s would like a really cool photograph, makes me want to see it, lol. You’re welcome, I’m glad you found this video informative.
@@Southern_Plains_Railfan The Photograph Of The Steam Locomotive That Was Lifted Off Of It's Wheels Was In A Hard Cover Book Written About The BR&P, (Buffalo Rochester & Pittsburgh Railway), By A Fellow Back In The 1980's. However The Book No Longer In Print And Contains LOTS Of Pictures Of The Locomotives, Shops, Stations And Road Gradings That The Line Had. It First Started In Rochester N.Y. After The Civil War, And Progressively Expanded Southward To The Coal Fields Of North Western Pennsylvania In The Late 1800's. As It Grew Larger, It Went Even Further Down To Pittsburgh And Branched Off Near Salamander N.Y. To Buffalo. It Even Used The Famous Kinzua Bridge That Was Over 2K Feet Long, (And Was Called The 8th Wonder Of The World When It First Opened In 1882), That Was Reconstructed In 1900 To Handle The Heavier Trains. But UNFORTUNATLY The Bridge Mostly Blew Over By An F-1 Tornado That Past Nearby It In 2003, While Additional Work Was Being Done To Preserve The Bridge. It Was A WELL MAINTAINED Line, More Like A "Big Little Railroad" Needing Their (2-8-8-2 I Believe They Were), Heavy Mallet Locomotives As PUSHERS And PULLERS To Assist The Heavy Coal Drags To Get Over The Steeper Pennsylvania Mountain Plateau Grades, Moving Coal That Was Mined Around The DuBois And Punsxutawney PA. Areas. YES, The Same Town Famous For It's Groundhog Weather Forecasting Earlier This Month. My Grandfather Worked As A "Boilermaker" At The DuBois "Lokey" Shop As One Of Their First Welders, But They Also Had A Steel Hopper CAR Shop And a Wooden Box Car Shop On The Other Side Of Town As Well. Primarily Because It Was More Centrally Located Between The The Two Ends Of The Line, And Had A Steam Powered Wrecker Stationed There That Could Clean Up Any Wrecks Or Provide Replacement Engines If Any Developed Problems Along That Approximately 250 Miles Of Track. However It Was The Salamanca Shop That Had The Lift That Could Raise The Locomotive Higher Into The Air For Wheel Replacement Or Framework Repairs. I'll See If I Can Find That Book And Make A Good Copy Of That Photograph, To Send To You By E-Mail SOMEHOW. OR, Have It Enlarged And Send It To You By Snail Mail If I Have Your Address. Dave...
