Why Weren't Duplex Steam Engines Successful?

What's the background music that plays from 2:56 to 5:36?

if you spoke to PRR engineers who piloted the T1's the majority of them would say that the wheel slip problem was a myth. The final analysis of this piece of railroad lore was that the engineers were not used to so much instantly available power, and that was the true cause of the perceived wheel slip issue. But as noted, most of the engineers were of the opinion that once used to the available power, and how to manage it, the wheel slip issue was non existent. But rumors, myths and folklore are hard to dispel, especially among non railroad individuals and rail fans.

What's surprising is how little the steam locomotive changed between 1870 and 1940. Mostly they grew in size and power, the most notable changes in the design were the addition of superheaters and feedwater heaters in the World War I era. No thought was given to a fundamental change such as use of a rotary positive-displacement expander, such as the scroll device patented in 1912. This would have eliminated the dynamic augment issue and greatly increased efficiency, but there was no incentive for change. The railroads had long been a complacent industry, having no competition except other railroads using the same equipment and methods, so they were caught flat-footed when the 18-wheelers and Interstate highways began to appear.

The S-1 still looks absolutely amazing. I wish it had been designed a bit better with its weight. And been preserved...

Discovered this channel only a while ago, definitely one of the best channels for American loco history. 😊

As a PRR guy the video is mostly positive. They were definitely ahead of their time in many ways especially in terms of electrification and steam technology (hence why the GG1s built in the 30s would refuse to retire until 1983 when they physically got too old) the problem is while they embraced new technologies, they had a habit of keeping the old ones a little too much. That doesn't deny the fact they we're truly "The Standard Railroad of the World" and one of the best fallen flags out there. As for 5550 the organization is actually not far from home (being started in Pottstown PA) and with the lessons learned from her predecessors 5550 will definitely be the ultimate steam locomotive. Certainly looking forward to the completion, besides if the British can build new steam from the rails up like Tornado, we can do it too!

Regardless of how practical or impractical they were, they definitely looked fantastic

I love how the T1s look. They have a very modern appearance.

For every great aspect of the duplex, there’s always a drawback and that kinda why I like them. Especially the T1’s. I always figured the T1’s were a tad too powerful for what Pennsy crews were used to, and this basically confirmed that. Something else to note about the T1’s trials on the C&O was their experience with some of the T1’s qualities. Staff were already rather familiar with multi-cylinder engines, even if they had a hinge in the frame, and they would’ve had some experience with poppet valves thanks to the recently rebuilt L-1 Hudson’s and possibly the L-2-a’s. The PRR wasn’t familiar with either of these so of course they would slip with a yanked front-end throttle. Splitting the drivers was probably a detriment in that regard, since each driving set had less wheels to recover from a slip than a Pacific or Northern type. In that regard, it was probably for the best that the Pennsy chose a 2-10-4 for its War Baby rather than a 2-6-6-4…

I like your theory about the PRR's engineers pulling the T1 throttles too fast. The great mystery is the entire Q Class. The PRR was always a 50 MPH freight railroad, with much of its cargoes being open top coal hoppers. That fact is why the PRR rejected the N&W Class A 2-6-6-4 locomotives, which they tested when they were considering the C&O T-1 2-10-4. That's probably also why PRR did not try the Challenger types (4-6-6-4). So why build such complicated locomotives with 69 inch drivers as the Q's? Thanks for promoting the T1 5550 project!

I worked at the Eddystone plant in the 1980's where I was doing prototype work on the V22 osprey. The locomotive works was at the time was the main assembly building for the CH47 Chinook Helicopter. the large facility worked well for 2 reasons the large gantries were good places for assembly of large components, and their location on Delaware bay was a good relatively safe place to conduct initial check out flights in the crowded Philadelphia area.

The power required to propel the locomotive itself was considerable. Such an interesting video.

I’m not a train nut like most of you on here, but damn these things are beautiful. Something about more wheels, just looks amazing

I've never heard of "duplex steam engines" before, what an interesting concept. I was lucky enough to see and ride behind the N&W J 611 in the 2015 debut after restoration in 2014-2015 and what an amazing experience having seen it so often in the museum wondering what it would be like with such a machine to actually move under its own power.

Great video on some of the Pennsy’s greatest engines. It just so happens that my channel gained 5k subscribers today, and I changed my PFP to reflect more of the Pennsy’s heritage, so seeing this video today is a bit of a good omen.

I’m from Darlington, England. The world’s first passenger locomotive was built about 100 meters from where I grew up! The new steam locomotives, Tornado and Prince of Wales were also built at the same location and now run on the main line between London and Edinburgh (and stopping at Darlington of course).

here's to the newest T1 to be built, and hope it can break the steam speed record in the process!

Simply excellent in all facets - script, narration, visuals, audio. There's a story in a book I have somewhere (which belonged to my father) of a crew on a T1 testing its speed on a straight flat stretch in Indiana. IIRC no record of the speed was made but the dispatcher (?) chastised the engineer, winked at him and quietly said "never do that again". Given the T1's specifications I thought that it should have been able to break the LNER Mallard's world speed record for steam. Maybe the valve gear would have given out. FYI I have an owned an HO undetailed T1 for about 35 years.

Reminds me of some of the absolutely gorgeous machines from the flying boat era, such as the Saunders-Roe Princess and the Boeing 314 Clipper. The jet age came along and jet engines became the standard for truly large aircraft, plus the boom in passenger travel saw ground-based airfields transform into massive airports as we know them today. Flying boats just weren't needed anymore and that unique era of aviation passed into history.

One thing I have always wondered was why trains have an open steam system. Ships operated with Triple Expansion engines for over a century. These systems had a closed loop system that sent the spent steam through a condenser and back into the boiler, so they didn't keep having to refill their boiler tank. Trains just dumped the spent steam out the piston. It seems to me that a system where the steam is pumped through internal pistons and a condenser, back to the boiler, and those pistons then transfer motion to the wheels through a cam system would be much more efficient and have much fewer moving parts, especially exposed on the outside. This would also eliminate the need for frequent stops to re-water. I'm a fan of Railroad Tycoon, and have had a few occasions where I had to spend the money to add a little junction station somewhere useless to install a Water and Sanding tower for trains passing through (particularly in rough areas) or along long high-value stretches.