Did steam locos need to look like steam locos?

[Dinorius_Redundicus]

Just found myself musing on this question, but I hasten to say I'm no expert on loco design or history.

When I think about steam locos, the image that comes to mind is always one of a big water boiler tank, large, spoked driving wheels and external pistons driving them by rods connected to the wheels. The cab is usually to the rear of the boiler. Apart from different numbers of wheels and superficial attempts at streamlining, that basic design didn't change until steam was replaced by diesel and electric locos (or did it?). Why didn't this 1800's arrangement evolve?

I can understand the need for the water boiler on the loco - you can't have steam without water and the best place for it is on the loco because the weight adds to traction. But were other aspects of the design really fixed by the physics of steam locomotion? Did the driving wheels really need to be so large in diameter and spoked, driven by pistons and heavy rods? Did all that driving gear need to be external and replicated on both sides? Could the efficiency of steam locos have been improved by replacing the heavy reciprocating pistons and rods with lighter rotating components like turbines, drive shafts and gears? Did the cab need to be at the back?

 

[SD45T-2]

Oh great, this is going to be a long post. Here goes...

All apspects of the Design remain the same for some very logical reasons.

1. All steamers have 2+ Cylinders because of a inherent problem with using only one cylinder. If the cylinder stops in a certain place on a one cylinder loco, it "locks up". Two cylinders prevent that because they move in tandem. So when you move one cylinder, it naturally moves the other.

2. Turbines are too complicated and only work well when going fast. They have tried putting them in locomotives. (PRR 6800) But, it was kinda hard to get moving and it cost a lot to maintain. So, it's gone. The other turbine type, (Coal Power Plant on Wheels) had problems with the electricals getting contaminated, and they failed constantly. So, none of that.

3. It's kinda hard to move a solid fuel to the front. The reason for the cab in the back on most locomotives was that the fireman did not have to go far to get coal (Or Wood. Or Mummies:hehe to the firebox. The only cab-Forwards were oil-fueled, or had the coal bunkers near the front.

4. In Britain, there were many small locos that had inside coupling rods. E2's ,for example.

5. Google T&P 610, or any 2-10-X type. The drivers are very small on Drag loco's.

Of course, this is pretty basic in steam terms. To try and make a complete study of steam would take a lifetime. And you would be dead.

 

[sniper297]

Actually them upside-down Aussies did change the design - they turned the steam loco inside out.

Some models had bogies under the cab/firebox/boiler section, but all had two sets of drivers under the front and back tenders. Front tender had the water since that could be pumped by remote control, back tender had the coal so it could be shoveled into the firebox. I used to think the geared Shay was the weirdest steam loco in the world until I saw the Beyer-Garratt.

 

[sniper297]

Missed a couple;

"Did the driving wheels really need to be so large in diameter and spoked"

Some were smaller in diameter for better low speed torque, switching engines in particular. Others had the diameter increased for faster top speed, particularly in the flatlands where they didn't have to climb grades.

As for "replicated on both sides", the geared Shay (meant for climbing REALLY steep grades on logging railroads) had it all on one side, with the boiler offset to the other side so the whole thing looked lopsided.

http://en.wikipedia.org/wiki/Shay_locomotive

 

[Euphod]

Form follows function.

 

[Dinorius_Redundicus]

OK, so there's no way that a steam loco could ever have looked like a diesel or electric loco - small wheels, internal driving mechanisms, cab at the front, big windows for the drivers, sleek modern-looking shell?

 

[RooRocz]

There were several issues with turbine-driven steam locomotives that prevented them from really catching on.

1. Cleanliness. Turbines were very susceptible to contamination by coal dust; it would gum up the works and generally make a mess. It would also gradually erode the blades, which had to be replaced frequently. Coal power plants and engines on large ships avoided this by keeping the turbines away from where combustion happens. This was less practical on a steam locomotives because there simply wasn't that much room.

2. Fuel efficiency. Reciprocating steam locomotives consumed less fuel while idle or at low speed, enough so that many railroads would leave fires on 24/7. (firing up a steam locomotive also generally took several hours, another reason just to keep them fired all the time.) To keep the turbine running required a fairly constant huge supply of fuel, even while idle or running at low speed. (though at high speeds, the efficiency was significantly better than conventional steam locomotives. Unfortunately the money-makers weren't the crack passenger trains, they were the 15mph coal drags and the slow manifests.)
The Bombardier Jet Train avoids this by having a diesel engine for low speed operation.

3. Mechanical complexity. There's a crapload more parts that you need in a turbine locomotive. I mean, look at this monster:

You have to pulverize the coal before you use it, you have to have condensers to recycle the water, you have to have an electric generator, you have to have a bunch of other garbage besides.
Some locomotives were direct-drive turbines, like the PRR S-2...

...which had their own set of problems. Turbines can only run in one direction. This could be fixed with gearing, of course, but the PRR engineering department was run by a bunch of wackos, so they just fitted the locomotive with a second turbine that ran in the other direction. (because more turbine more better, I guess.)

Plus, you have the problem that railroads are by nature a very conservative business. They really only try well-proven designs. This is part of why we see very few unique locomotives these days (apart from some nincompoopery from the UP in the form of the U50, DD40AX, C855, etc.). By the time we had the technology to make well-functioning steam turbine locomotives, the diesel-electric drivetrain was already a proven design racking up millions of miles on the rails yearly.

 

[Euphod]

OK, so there's no way that a steam loco could ever have looked like a diesel or electric loco - small wheels, internal driving mechanisms, cab at the front, big windows for the drivers, sleek modern-looking shell?

Except for the size of the drivers, the external gear and the fact that they weren't shrouded I would say the cab forwards were as close as you're going to get!

 

[sniper297]

Well, again we're dealing with different propulsion systems, a diesel is moved by electric traction motors geared to the axles, so instead of changing the wheel diameter for speed or starting torque, they only need to change the gear ratio. Some European steam locos had all the kibbles and bits inside the frame, and some European diesels had external connecting rods on the wheels.

Small wheels;

http://www.cnwhs.org/memberphotos/displayimage.php?album=5&pos=164

Streamlined shape;

http://www.cnwhs.org/memberphotos/displayimage.php?album=5&pos=75

Cab at the front, big windows;

http://www.gamersdailynews.com/userfiles/image/2012/June/cab-forward.jpg

Like Euphod says form follows function, so the most common type had the same standard design over the years, but there were variations for special circumstances.

 

[sniper297]

Here's some fun ones;

http://www.dieselpunks.org/profiles/blogs/sunday-streamline-43-german-whales

 

[Dinorius_Redundicus]

Very interesting discourse, I'm glad I posed the question. It's good to see at least some attempts were made to break out of the Stephenson Rocket paradigm.

I probably sent the discussion off on a tangent by mentioning turbines. I was just trying to think of an example of something other than a piston. But if we stay with pistons for the sake of following the idea, could they (in principle) have been placed internally and geared to the axles, thus doing away with the traditional big driving wheels, and massive connecting rods? The advantage if that were possible might have been a lower centre of gravity (more stability), more scope for attractive styling and streamlining, and perhaps greater efficiency (I'm thinking there must be a lot of energy wasted in reversing the direction of those connecting rods twice per wheel revolution).

 

[jjanmarine3]

Not dumb at all, very interesting stuff.
I think there would not be enough space ( too bulky ) to place pistons on the insides and maintenance would be a nightmare. The siderods or connecting rods and their bushes and bearings plus lubrication and such issues are relatively easy to maintain from the outside too.The connectiong rods also serve to have all the wheels pull together and all driving from one central point on sets of wheels. Would have been interesting to see the effect of electronically controlled wheelsip system on steam like on the modern locos with steam driven motors geared to each wheel...but all tose pipes and gadgets ..
Heat dissapation is or was a big issue when it comes to solid and spoked wheels on many types of locos and rolling stock, solid wheels caused many problems due to overheating and cracking, loose axles and loose tyres, from brake block and other operating frictions .
As for wasted energy - I am talking under correction here - steam has enough energy or power on most applications, the biggest problem was efficiency , to apply that power efficiently without wheelslipping , heat losses, bad water and coal , etc. I remember steam cranes used to pick up derailed vehicles etc, would just not stop powering and would pull itself over on its side in a jiffy or break things if staff did not stick to the safety rules.
If you google 'modern steam locomotives' you will be surprised at what was developed and what could have been and possibly what might be again in future - who knows ?

 

[Dermmy]

Many smaller locos - particularly tank locos - had their cylinders on the inside between the frames. The coupling rods however (the ones which transmit the drive from the cranks driven by the cylinders to the cranks on the other wheels) were on the outside - think about it, they have to be! They run on a crank which describes a circle around the axle - no way can they be inside the wheels!

As mentioned above a steam engine can't run on one cylinder - OK, it CAN run on one, but it can't start on one cylinder. That's why a kid's steam donkey engine needs it's flywheel spun by hand to start. Once it's turning it's fine, but one cylinder can't start the motion, it jams at bottom dead centre (or top, depending!) Of course I'm thinking ship engines here, a steam loco has it's cylinders rotated more-or-less 90 degrees so jams front or back dead centre, but it's the same principal! Incidentally this is why steam locos have the cranks on opposite sides 90 degrees offset - 180 degrees would seem more intuitive, but that jams at exactly the same place as a single cylinder. It's the drive from the cylinder 90 degrees behind that carries the first cylinder past the jamming point.

Many steam locos however have three or four cylinders - the two on the outside that you can see, plus one or two on the inside which you can't see. Three cylinders are usually simple expansion, fours are generally compound expansion. Now there was a nineteenth century engineering fantasy! The idea got about that the exhaust steam (which is in effect driven out of the cylinders under pressure) could be re-used in a second set of low-pressure cylinders and have that 'wasted' power captured. It took a while for them to work out that the energy required to pump the steam into the second pair of cylinders was actually greater than the energy that could be delivered by the second set - they were in effect chasing perpetual motion - but the idea hung around for a long long time.

I’m starting to ramble…..

 

[amigacooke]

Actually them upside-down Aussies did change the design - they turned the steam loco inside out.

Some models had bogies under the cab/firebox/boiler section, but all had two sets of drivers under the front and back tenders. Front tender had the water since that could be pumped by remote control, back tender had the coal so it could be shoveled into the firebox. I used to think the geared Shay was the weirdest steam loco in the world until I saw the Beyer-Garratt.

I think that locomotive design was first conceived in Manchester in the UK.

 

[Enkidoh]

Yes and no. Herbert Garratt (the original designer of the articulated loco design that bears his name) was actually Australian originally, hence sniper was correct from a certain point of view. Additionally, even though the British firm Beyer Peacock were the original sole builder licensed by Garratt to build locos to his patent, the very first railway to purchase Garratts was the Tasmanian Government Railways, as their K class.

Sadly Herbert died before seeing his design really start to become widespread though - but it's worth noting that the K class were somewhat different from later Garratts being compounds, as well as having the cylinders face inwards rather than outwards as all later Garratt designs had, as shown in that photo.

Also it should be noted that the third type of Garratt built, the WAGR M class, added non-coupled wheels to the mix too, further improving the design. But I'm rambling here.

P.S. if you think a Garratt is the oddest looking steam locomotive design, then you've clearly never seen what a wacky Scotsman came up with before then, namely, this (specifically the double type)

 

[amigacooke]

Yes and no. Herbert Garratt (the original designer of the articulated loco design that bears his name) was actually Australian originally,

Not unless being born in London counts as being Australian.

Herbert William Garratt (Festipedia)
Herbert William Garratt (Gace's guide)
Herbert William Garratt (Steamindex)

and perhaps the clincher

Garratt, William Herbert (Encyclopedia of Australian Science)

 

[itareus]

Maybe this will clear up any remaining doubts about Mr Garratt:

"...The Garratt articulated locomotive was developed by Herbert William Garratt, a British locomotive engineer who, after a career with British colonial railways, was the New South Wales Railways' Inspecting Engineer in London..."

(Extract from Wikipedia http://en.wikipedia.org/wiki/Garratt .)

I'm glad that steam locos looked as they did (do), I can't see how people get about a new diesel being built that looks about the same as the last batch, although it would make creating them for Trainz a whole lot easier !

 

[Buncs]

Oliver Bulleid, CME of the Southern Railway had a try:

Further info:

http://www.bulleidlocos.org.uk/(S(ks1h0u3sv2afrbv2qtswta2n))/_ldr/ldrClass.aspx

Regards

Dave

 

[itareus]

How could I have forgotten the "Leader", well remembered Buncs.

I think MR Bulleid must have borrowed some Underground stock for the bodywork !

 

[Bill69]

If you want a steam engine to look like a deisel how about a DD40X with an oil fired boiler in the rear half and a V12 steam engine in the front half. 'Course it might have to be a bit higher to accomodate a long stroke V12.:hehe::hehe::hehe:

Bill69