If you were to visit a railway almost anywhere in the world, you would find that unless it was in some way running heritage trains, the locomotives would bear a similarity to each other. Electric traction is the norm, whether it comes from a trackside supply or from a diesel generator. In the middle of the last century, as the industry moved away from steam traction though, this was far from a certainty. Without much in the way of power electronics, it was a challenge to reliably and efficiently control a large traction motor, so there were competing traction schemes using mechanical gearboxes or hydraulic drives. One of these is the subject of an archive film released by the oil company Shell, and it’s a fascinating journey into a technology that might have been.
All diesel locomotive designs struggle with the problem of transmitting the huge torque required to start a fully loaded train at low speeds, and because of the huge force required, it’s impossible to design a locomotive-sized conventional gearbox to do the job in the way it might be managed on a truck. Electric and hydraulic drives exploit the beneficial torque characteristics of electric and hydraulic motors, but the mechanical gearbox isn’t quite done for. The subject of the video is British Rail number 10100, otherwise commonly known as the Fell locomotive, and it was a one-off prototype that took to the rails at the start of the 1950s designed to test a very novel gearbox design. Mechanical Unpacking Machine
At the heart of the Fell gearbox is a set of differential gears the same as you’d find in the axle of a car, and in the locomotive they are used to combine the output of more than one engine. The loco had four smaller-than-normal diesel traction motors that could be combined, but even then, it wasn’t done. To achieve variable torque, they employed superchargers driven by a set of even-smaller diesel engines, resulting in an ungainly multi-engined beast but with the desired characteristics for both starting heavy trains and for moving them at high speed.
By 1950 the general form of a diesel locomotive with a frame containing the power plant supported by bogies carrying traction equipment was well established, but the Fell eschewed this layout in favour of something more reminiscent of the steam age. As a 2-8-4 with the four driving axles in its centre sporting connecting rods, it resembled a steam locomotive from the chassis downwards but with a very diesel-age cab and superstructure. It’s often referred to as a footnote or even a failure in railway histories, but despite suffering some mechanical failures, it was, in fact, a successful demonstration of the design. Sadly, this didn’t convince the railway to continue with the idea, though, and after a heating boiler fire, it was withdrawn and scrapped in the early 1960s.
The film below the break is a fascinating window into the early part of the UK’s transitional period away from steam traction, with the locomotive we know now to have been a dead-end being portrayed as the bright future for the railway alongside steam locomotives that were then very much still in production. We see it through its design and construction before being tested mostly as far as we can see on the now-closed Pennine routed London to Manchester run, a future that never came to pass against a backdrop of a railway that didn’t make it into the modern era. For fifteen minutes of heavy engineering from the days when diesel locomotives were new and exciting, it’s well worth a watch.
“All diesel locomotive designs struggle with the problem of transmitting the huge torque required to start a fully loaded train at low speeds…”
Huge energy is available in a chemical explosion. The trick is to capture it and release it over a longer period of time. A good example is how a single blank shotgun shell is used to start a large aircraft engine that when running normally produces thousands of horsepower.
So that makes me wonder why they didn’t just us the fuel to make the gas that would drive the starter? There must be a good reason since I never heard of anyone doing it.
“Cartridge Start” or a clockspring mechanism were popular in WWII fighter planes because they didn’t rely on a battery to start the engine. A battery large enough to do so would decrease the payload/range.
If you liked this then you will love the English Electric GT3. A gas turbine loco that was built into a steam locomotive chassis on British Rail metals at around the same time.
The transmission was reminiscent of a differential drive tank tread. they use two input shafts turning at different speeds so as to be able to spin in a stationary position as well as travel, without relying on brakes to drag one tread. On the top of train powerplants, I drive a pivot steer loader daily and I have wondered why there are none with diesel electric propulsion as it would seem to provide numerous reliability advantages.
Most skid steer loaders are actually hydraulic driven. Electric motors wouldn’t necessarily be better since a large hydraulic pump is already required for the lift cylinders.
Skid steers are hydraulic yes, but pivot steers tend to use a separate torque converter that is much heavier duty than the hydraulic cylinder pump. They do require rebuilds and maintenance, and the extra propshafts and four wheel drive drop box can be troublesome. One would think that using an electric motor on each wheel and one on the power take off, if fitted to a tractor would be dependable. It likely comes down to cost though.
Also all that copper isn’t exactly light. The Nazis wanted to build the Tiger gas-electric at first but it was too heavy and expensive. Instead it got a normal gearbox that had reliability issues pushing a 57t tank offroad
I’d imagine they could and would do various hydromechanical things before going fully electric like you said for cost reasons. Though if you want to keep fully variable forward speed, you need a fair amount of hydraulics even with a lot of the power bypassing some of the hydraulic system in a hydromechanical CVT. But if you wanted something cheaper with drawbacks, you could use hydraulics for the steering input of a double differential like setup, and you could have more drive power than hydraulic power. Maybe not appropriate for the pivot steer, but just speaking in general.
Relevant to your initial thing, some Canadians are doing diesel-electric trucks – look for “Edison Motors”.
So, a key part of the solution is the “hydraulic coupling” instead of a clutch (or 4 of them).
Wikipedia is much clearer of how the thing works:
https://en.wikipedia.org/wiki/British_Rail_10100
Those “hydraulic couplings” are the same as the torque converters used in any “automatic” transmission.
The complicated thing with the four differentials does not explain how this thing can get started from a standstill. With only one of the motors working at low speed, the available torque will also just be 1/4 of the total.
Another essential part according to Wikipedia are the roots blowers driven by separate motors. They can give the diesel motors a high boost at a low RPM of the diesel motors, so the diesel motors can have a relatively high torque at low RPM.
And apparently it did not work very well. It was only used for a few years and Diesel-Electric is apparently still the most used combination.
The thing with the differentials can certainly produce a gear reduction, just not in excess of the loss in power from turning engines off. For example, you could do this, though I don’t know if they did exactly the same:
Arrange the differentials so that the parts which correspond to the left and right wheel outputs in a car are attached to an engine, and the part which would be the center goes further into the drivetrain. Make it so that the diff which connects to engines 1 and 2 is connected to the one which handles 3 and 4 by a third diff, producing one output at that point. Use clutches, one-way bearings, and/or brakes, so that when only one side of a diff is in use, that side is prevented from moving while the other side and the output can continue to rotate, but you can still go forward and back, can push it, can hook up whichever combinations at once, etc.
A differential, apart from the inherent axle ratio, makes the speed of what would be the center on a car be the average of the two sides. So if you make one side’s speed 0, then the most speed an engine on the other side can cause the middle to rotate is 1/2 of the engine’s speed (again apart from any fixed gear ratios involved). So starting the second engine increases the speed, rather than the torque, because the speeds add but the torque doesn’t. If the torque is enough, you want a low speed to start smoothly. For torque needs, the blowers and potentially the couplings (IF they are not simple slipping couplings, but actual torque-multiplying ones like we are used to) take care of things.
Misses the point, when more power is needed, starting off, approaching gradient, engines are taken out of system to get a lower ratio, so it’s inefficient and not cost effective.
Not sure about gearing like a truck but there were geared locomotives that powered the wheels from a common shaft. Heisler and Shay’s are two stream locomotive families I’m familiar with. Mutual Plywood Corporation #54 Is a diesel mechanical I’ve driven. The company back back then took a Heisler, removed the steam bits, added a diesel engine and boxed it in with a cab.
The torque multiplication is 4 from each engine, whether the other engines are connected or not. The loco could pull from stationary with all 4 engines but the acceleration would be too great for comfort. I guess the engines would stall if a low throttle was used instead to pull away smoothly.. I think you could have made a 4:1 / 2:1 / 1:1 planetary gearbox of the same or less weight and have one large engine, perhaps with the ability to disable cylinders (as has been down with petrol engines for economy).
Combining multiple motors in a differential to drive the output is exactly how the Prius does it. Replace the wibbly-wobbly term “planetary power split device” with the understandable term “differential” and suddenly it sounds very familiar.
I’d be curious to know the opinion of those who operated this locomotive.
I have an original copy drivers manual for this (Fell) locomotive. It had multiple throttle levers (“scoops”, the manual calls them), 1 for each engine, and the mode of operation is so unbelievably complicated, it’s no wonder the experiment wasn’t carried on. All I can remember off hand is “If the throttle sticks, don’t Force it, investigate”.
I once saw a steam locomotive pull into a large station (amongst the modern trains) and it was quite a thing, those steam engines are something to behold, all that smoke especially. It’s weird to see smoke coming from a train for us present day people; but you don’t really realise it seeing it in movies. I know diesel engines have smoke too, but nothing like a steam engine with its smoke and steam.
The smoke is actually unburnt fuel. If the firebox is over fired (too much coal put on) the smoke will be thicker. Sometimes it will be done “for photographic effect”, as it can look quite impressive, but it wastes fuel, and soots up the boiler tubes faster, which hinders the heat transfer from the hot gasses to the water, and also restricts the flow of the flue gasses. Not good. The Ideal way is to keep a bright Cherry red fire, not a coal smothered one. The smoke should only be light at the chimney, for the most part. You need to think ahead when firing up on a steam loco. More coal than usual (a little heavier firing) is needed just before heavier work is engaged, such as climbing a bank, and so slightly more smoke will be seen, for brief periods. Now the occurrence of smoke (which is brown, black, or grey) is quite different to the occurrence of the steam, which increases as the loco works harder, and decreases as the regulator is closed, but there is another factor affecting the visibility of the steam; in hot weather, the exhaust steam does not condense readily and often remains invisible, whereas in cold weather the steam will condense into visible water vapour as soon as it exits the chimney, so giving a huge white cloudy exhaust trail.
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