The most absurd tank engines ever built - 2-8-8-8-2 'Triplexes'

In this video, we take a look at the triplex locomotives, engines that had more driving wheels than they knew what to do with.

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[CarlosDeLosMuertes]

A bit thing you are missing here is while they ended up being pusher (banking) engines, that's not what they were intended for.
(I manly learned about the Virginian 700, but I believe the Erie 3 where of the same reasoning)
These were designed for Coal Drags, which don't need much in terms of speed, but did tend to need more than single digit top speeds.
The want was for one big engine (and thus one crew) for these and to pull ever larger drags.
But when they couldn't provide enough steam for the journey they were dropped down to pusher service.
However in the US pusher service wasn't really anything special, a standard engine or two was typically enough for this and the benefits of a special engine for this was greatly outweighed by the costs.

[WatchVidsMakeLists]

Imagine being stuck at a railroad crossing and having to wait for a 6.7-mile-long train that's only going 4 mph...

[ThomasFarquhar]

I saw the thumbnail and thought "tank engine? That has a tender!" But nope it's just massive

[cr]

0:17 "Each bogie was powered with three cylinders giving the Big Boys a significant amount of power" - No, and no! The Big Boys had one fixed engine unit (set of driving wheels) at the rear, and one swivelling engine unit at the front, which you could call a 'bogie' at a stretch. That was the '-8-8-' bit. The actual bogies (aka trucks) would have been the carrying wheels at each end, hence 4-8-8-4. And the engine units were twin cylinders, hence 4 in total.
0:40 "These boasted three cylinders per bogie" - again, no. So far as I'm aware, the Triplexes only had two cylinders per engine unit, also.
This is why the UP 9000 4-12-2's - which did indeed have three cylinders - were such a notable exception in large US steam locomotive practice.

[slimetank]

Everyone knows and love the fictional mad scientist trope, but we've been glossing over how terrifying mad engineers are

[thekric]

I just love how ridiculous trains could get back in the day

[lazyrrr]

Oh, for those good old days when they just went ahead and Built one to see if it would work or not .

[CardScientist]

One other issue the Triplex had was that, as it used its coal and water, the driving wheels under the "bunker" would lose traction and slip often because the weight of the coal and water pushing down on those particular driving wheels would drastically reduced the long the locomotive ran

[WEM]

The Big Boy only had four cylinders—two on each engine set. Also, only the front set articulated; the rear set was rigid with the boiler and cab.

Though, the Union Pacific did build a series of 4-12-2 locomotives that had three cylinders. One of them, #9000, survives today.

[Huttser]

Another problem with the triplexes I'm surprised you didn't mention: As the fuel reserves were depleted the driving wheels under the "tender" became much more prone to slipping, so power would have to be reduced to all the drivers as the tender set did not have their own throttle valve.

[edwardvincentbriones]

There is a (claimed) story that when a Triplex pulls a heavy train, possibly heavy freight, the locomotive pulled so strong, the couplings of the cars and trucks of the time could not withstand the power and, possibly, broke under pressure. That’s why they were used afterwards to push not to pull. Interesting story.

[Dat-Mudkip]

A couple of things that you missed:
*Too Much Power* - The Erie was the first to have Triplexes built. Named "Matt H. Shay" in honor of a beloved employee of the railroad, it was originally intended to pull trains up the steep grades on its own. During testing, it was pulling a train of 250 cars up an incline. The journey went well, until they hit the 17 mile mark; here, a coupling snapped, and the train was ground to a halt. Investigation found that the engine was so powerful that the shock of just normal operations was enough to literally tear apart rolling stock. Undeterred, they decided to instead have it serve as a banker.

*Virginian Woes* - While the success of the Erie's triplexes is generally considered uneconomical at the best of times, the Virginia Railroad's sole example was far less successful. The XA (numbered 700) was designed to drag up to 10 miles an hour, but it was found that anything beyond ~5 mph would empty the boiler of steam faster than it could be produced. Despite actual personnel from Baldwin stationed where the engine was kept to try and assist in hammering out the problems, it just simply didn't work. Worse still, the VRR found them even less reliable than the ones that the Erie were using. In fact, 700 in general was disliked by the crews.

*Too Much Puff, Not Enough Steam* - _Matt H. Shay_ was given a 90 sq ft. grate area for the firebox; this proved insufficient, and so both the second and third received a 122 sq ft. grate area. Despite this large increase in size, it still wasn't enough to satisfy the demand the driving wheels provided.

[Vextrix]

I always say this when I see a triplex...

"UNLIMITED TRACTIVE EFFORT"

[andrewhall]

The Triplex locomotives were compound engines. High pressure steam entered the center set of cylinders and the exhaust from these cylinders was split between the front and rear cylinders. Exhaust from the front cylinders went up through the stack. The exhaust from the rear cylinders went though a feedwater heater and then to atmosphere via a large pipe at the back of the "tender".

[mgr_video_productions]

Amazing video as always. I've never thought of these unusual locomotives as tank engines until this video. MTH made these in HO scale as well.

[bobsbasementhotrains]

The Virginian Railroad had massive 2-10-10-2s that had the biggest diameter boiler used in the US. I have read that they could maintain there steam pressure will pushing heavy trains.

[ingor.]

I read from these Triplex Engines in a german book of railway engineering of the year of 1918, when a few german (prussian) railway engineers reported about of those locos.
All three Triplexes had been owned by Baldwin but never had been bought from the ERIE RR where it had been tested and had showed that the too small firebox could not produce enough steam pressure to operate those engines effeciency enough.
The exhaust of the front and rear Zylinders went into thr larger middle zylinders and used the steam expansion to drive all zylinders.
The exhaust of the middle zylinders had been tiled also from one side to the front smokestack and from the otherside to the back smoke stack after heating the water inside the tender.

One Engine had been sold to the Virginian Railways at Norfolk, Virginia where it had been built a little bit longer because of a much bigger firebox for burning virginian anthrazite coal, what brought more better results than burning the pennsylvania coal of what the ERIE RR wanted to haul to Buffalo or other Harbours at the great Lakes.
At the ERIE RR those three Engines did shunting the coaltrains, theit max speed was around 25 mph as empty engine and more less than that with additional cars behind it.

The Virginian #700 was much more efficient running by much higher speeds of up to 40 mph, the plan use it as pusher engine had been giving up very early, the loco could run ahead middle long standard trains but was too expensive in operation, so it was giving back to Baldwin in thr 1920's like I read from other railway engineering books of the 1920's.
The problem were the tracks and the loco weight of metric tons per axle.
The higher the loco weights the more bigger the tons per axle.
Thr more expensive are the rails, what could carry those heavy engines.

[nicholmansgarage]

"Just don't expect to see anyone building one anytime soon"

To be fair, nobody expected a new build PRR T1 either. Although, one of these would just be insanity.

[jordanwhitecar]

somewhere is the ghost of a locomotive designer thinking his 2-8-8-8-8-8-8-8-8-8-2 design would've worked

[themightyalpaca]

Somebody: *Builds an 0-8-8-8-0*
Somebody else: *Consumes far too much alcohol, and proceeds to design a 2-10-10-10-10-10-2*