A comment and a question

Hello everyone. I have a basic interest in steam locos and something came to mind the other day which I thought I would mention: it amazes me that the sole driving force on those enoromous steam engines were two (or four) connecting rods pushed by steam to move those massive wheels. All the power to pull that much weight on those relatively tiny rods! My question is this: why were there no gasoline powered locomotives? There are many car enginess over 400HP and they weigh maybe 800 ibs? To get 8000HP, I would imagine that one couls build one a lot lighter than the average stem locomotive!
Thamks!

pandadug wrote:Hello everyone. I have a basic interest in steam locos and something came to mind the other day which I thought I would mention: it amazes me that the sole driving force on those enoromous steam engines were two (or four) connecting rods pushed by steam to move those massive wheels. All the power to pull that much weight on those relatively tiny rods! My question is this: why were there no gasoline powered locomotives? There are many car enginess over 400HP and they weigh maybe 800 ibs? To get 8000HP, I would imagine that one couls build one a lot lighter than the average stem locomotive!
Thamks!

Three reasons, among others:
1) Gasoline is much more volatile than diesel, and should it leak it's more likely to catch fire and/or explode.
2) Diesel contains more energy per gallon than gasoline.
3) Weight isn't an issue with locomotives - in some respects, the more weight the better, because that provides more tractive effort.

Having said that, there were several early self-propelled railcars and locomotives powered by gasoline, but the flammability issue largely restricted gasoline to automobiles.

Ah! I see. Thanks for the quick answer. And sorry about all of the typos; while I was writing, I had a baby demanding my attention and I didn't proof-read what i had just written.

I have no authoritative source to quote, but another point that likely influenced motive power fuel was the torque available at the crankshaft.

As a general rule, diesel engines produce much more torque on the crankshaft than a comparable gasoline engine. As an example, a modern six-axle locomotive's engine tach's out at just over 1100rpm (the gauges on the DASH-9's & Evolutions I've run usually tach about 1095-1097) At that speed, the diesel is producing in excess of 4400hp (4400 tractive plus parasitic loads).

This comes into play back then especially, and even today, when you figure that increasing speed increases the friction heat that needs to be dissipated. Slower speed means it is easier to lubricate, which means bearings are less of a maintenance issue
(though with modern ball, roller and needle bearings, its not as big of a design constraint).

When fuel handling issues are coupled with engine operation characteristics, diesel is the clear winner.

Historically, there have been lots of gasoline-engined locomotives (mostly small), and much of the technology of the diesel electric locomotive was developed in Gasoline-electric self-propelled passenger cars between 1910 and 1920.

Well, also we had to consider:
Fuel needs air to burn. Diesels and gasoline engines 'draw' their air,. Common gasoline engines do at the first downward motion of the piston, and aspirate their combustion air.
In Diesels they found, that only aspirating isn't worth, to successfully burn the fuel economically, so the turbo diesels made the game. Here the exhaust gas turbine propells the air compressor in the aspiration tubes and pumps air into the space of the cylinder, to maximize air volume in the cylinder.
So to burn gasoline, much concrete air fuel mixture has to be ensured, and also it's very dangerous to fire that as an open flame, but it can be done.
Done by gasoline evaporation, air mix nozzles and secondary air cooled burners.... usually those burners are difficult to handle and difficult to operate, because a high risk of flash overs during burner shut down or burner starting processes. Not realy a good ideal, also if the tank has a problem, you run around with a several kilo ton bomb behind you, ready to explode and shoot your tail right to the moon. That's much more dangerous than the boiler in front....
Also, steam engines aspirate their air by the blow pipe, or so called exhaust ejector. If the engine is on idle, the fireman had to power on the fresh steam ejector, to ensure a good draft... consider: The fireman has to start the ejector, before the driver will shut the throttle and go to idle. If any failure happens, you got the best flash over in the cab you ever seen, because the burners where at full power and to shut them down will require a time.
Dangerous...
So how to ensure the best combustion air mass to the combustion area by only ejector and exhaust steam? Impossible.... if you burn such a high value fuel, you have to ensure a complete combustion, and this means a full control of the air flow for combustion.
That's why modern natural gas heatings have electronical air flow control.

So also gasoline is a fuel, usually for internal combustion engines. In heatings, and a boiler is only a form of high pressure heating, fuel is used for heating purposes and not to generate high torque power... os it has to burn, rather than to explode.
So a less valueable fuel can be used, and can be fixed to a complete smokeless combustion. This is natural oil, like sunflower or rape oil, also coconut oils can be used. Usually a common diesel relative for heating purposes is used.
This burns well, has a high heat value and isn't that dangerous to operate and handle like more value fuels.
The power isn't only depending on the fue used, it's more depending on the fuel can be used and completely burned, smokeless combustion is the goal. And if you can ensure such a good combustion, you can get awesome power out of a boiler....
Well those tiny rods... are very massive constructions, able to widstand all the force from the piston power... but look what happens if the main bearing get's stuck: