Sawtooth500So what's a high back vs low back exhaust system?
You left out a word - PRESSURE.
A high backpressure exhaust system employs the usual blast pipe, along with constricted exhaust piping, sharp angles in said piping and, in general, higher pressure at the exhaust outlet of the cylinders. Typically, a high back pressure system will blast steam and cinders into the sky, even when running 40mph with reasonable cutoff.
OTOH, a low back pressure system will include some or all of the following:
The end result is a much lower pressure at the cylinder exhaust - greater steam usage efficiency at the expense of losing the ability to blow the exhaust away from the stack.
Since all of this is on the steam side of the exhaust, the fuel used is not a factor. UP844, which burns oil, has smoke lifters - and, from reports I have heard, needs them.
Chuck
Just a guess, but I think smoke deflectors ("Elepahnt Ears") were more prevalent on coal-burning locomotives. Could I be right? Many railroads used different methods. AT&SF had those pneumatically-operated 'smoke lifters' on some locos. It extended the smoke stack, but: beware tunnels, etc. The CPR, on the Kettle Valley route, had hopper-shaped deflectors (90-degrees rearward). Word is that they were loved by the helper engines, going thru the snowsheds and tunnels. Dunno about the guys in the final pusher engine, Not recorded. We installed "Toilet Bowls", of the same principle, on our UH-1 helicopters during the 'First Gulf War', back in the '80s/'90s. They gave less of a 'heat signature' to incoming heat-seeking SAMs. They directed the turbine exhaust upward. Anyhoo, the 'Elephant Ears' did look 'cool' on the NYC Niagaras, etc.
Hays -- Yar, a UH-1'er (67N3FC8PL). "When the last 'Blackhawk' is retired to Davis-Monthan AFB, a 'Huey' will take the crew home!". Same with the EMDs, GE's in charge! Har!!!
Sawtooth500How were you expected to see out the front with elephant ears? The just about completely blocked your front view... you'd almost have to stick your head out the window to see forwards... I bet it got mighty cold in winter and miserable when it was raining!
The smoke lifters or elephant ears did not block the vision of the engineer on most of the locomotives since it was only the thickness of the metal and iron to hold them in place. The engineer and fireman could see on both sides of the each smoke lifter. On the Union Pacific Challengers, they were attached at an angle since the running boards angled in past the smokebox. Those made it hard for the crew to see for sure.
The picture cuts off the outside view of the locomotive, but you can see how they can view down the track almost like a typical steam locomotive even with the lifters.
CZ
Elephant ear style smoke lifters were most useful with low back pressure exhaust systems, which had problems with smoke tending to cling to the boiler and cab. Their usefulness on locos with high back pressure exhaust systems (most North American locomotives) was somewhat questionable.
As seen from the cab, the elephant ear is a vertical line a few centimeters thick. It doesn't really interfere with visibility, any more than the posts between individual windshield panels (old autos and most diesels) interfere with visibility.
On the Japan National Railway, elephant ears were fitted to EVERYTHING - including ugly old 2-8-0s that couldn't have reached 70mph without falling off a cliff or high bridge! An idea of how important they were to safe operation is given by the wartime 2-8-2s that were built with wooden elephant ears.
Sawtooth500What exactly was the point of elephant ears on a steam loco? Like I've seen some challengers that had them, and some that didn't.
Hi,
they were certainly useful for speeds beyond 70mph and especially while drifting or on plains with harsh winds.
Speeds of Greyhound-Challengers pulling "The Portland Rose" may have been faster than 70mph on occasion. Quite a lot ( http://www.utahrails.net/up/ttg-challengers.php ) had them at certain times. They are called by their inventor "Witte" usually, but do not know the American definition. Big Boy 4019 had them also for short time but was used just a short time without any notice they were a success or useful on this type.
The bigger ones ( I think they are the ones usually called "Elephant Ears" ) are "Wagner"-Style, another RR-Engineer. They could substitute a full streamlined body by 80%, another important factor, saving power and fuel.
Cheers
lars
The ears are in line with the outside edge of the cab, so if you're leaning out you're looking down the outside edge of the ear and if you're sitting and looking straight out the front window you're looking between the boiler and the ear.
As to the cold, steam loco cabs are drafty at the best of times. In winter you're always toasty on one side and freezing on the other.
The elephant ears were used for a fairly short period up here in Canada too. At certain speeds they could lift the smoke, but I think the conclusion was that the improvement was not significant enough to continue.using them. Even without the deflectors, the smoke problem would only occur at certain speeds and throttle settings. Various other experimental deflectors were also tried, mostly up around the stack itself where they themselves wouldn't be in the line of vision, but those must have been even less effective.
John
SSW9389The idea for the elephant ears was to create an updraft to lift smoke away from the crew in the cab.
Our community is FREE to join. To participate you must either login or register for an account.