Reading an article on early diesel locomotives, I came across the term “true diesel.”
As opposed to what?
What diesels specifically? Some of the early small locomotives were diesel-mechanical, like a car. So maybe they meant it as opposed to diesel-electric.
Back in the day there were semi-diesels as opposed to true diesels.
“The semi-diesel or hot-head engine is not a true diesel, but retains the operating functions of the diesel with the exception of high compression. On these engines, the head or a bulb in the combustion chamber is heated to near red heat, usually with a kerosene torch. The engine usually has a manual pump that will force an amount of fuel that will be sprayed through a nozzle in the combustion chamber against the heated area. As the engine is rolled against compression, the manual pump is activated and the sprayed fuel ignites. This in turn creates pressure in the combustion chamber against the piston, thus starting the engine.”
Remember the model airplane you flew as a kid? The one where you attached leads from a battery to heat the cylinder before you released the spring loaded prop? That’s what’s known as a glow plug engine, the semi-diesel is a giant version of that. Notice how the heating leads are removed at the beginning of this video
Thanks, Beau. Got it.
50+ years ago, I was told that locomotive and truck diesels aren’t true diesels – it’s ships that have true diesels. Don’t recall the difference – maybe the huge slow-turning diesels come closer to maintaining constant pressure during the piston stroke, and that’s the criterion?
My sailboat’s diesel engine has glowplugs to use on cold days. On warm days it will start without use of the glowplugs.
Is it a true diesel?
Or a true sailboat?
If your air intake faces into the wind, does that count as supercharging?
Diesel engines engines ignite from the heat of compression once started, the glow plugs are no longer needed once the engine fires.
Hot bulb engines have a much lower compression ratio and do not ignite from compression alone. This is a double edged sword, they can run on a variety of liquid fuels but if run at very low load the engine won’t generate enough heat to keep the bulb hot and it will die (this is also possible on diesels, but it is rare and I’ve only heard of it happening at idle in very cold weather).
[:)]
Do the Diesel engines in locomotives have glow plugs?
I don’t think so.
Besides, at temperatures where they are needed you would also run into bigger problems with cooling water freezing and poor lubrication from cold oil upon starting. And more cranking power being needed due to cold oil.
I’ve seen old EMDs cold started at about 5 degrees above freezing a few times. They go but they aren’t happy.
I recall reading a story on another forum about a shortline operator who had antifreeze in their EMDs and sometimes had to start them outside during winter. In addition to having block heaters they would put a couple stock tank heaters in the crankcase to warm up the oil and thin it a bit.
Remember - Gen 1 diesels were left to run 24/7 back in the day. They only had plain water as their cooling fluid and their normal lubricating oil was in the 80-90 range and at normal room temperatures was more akin to grease that it was to oil.
Even today engines without AESS (Automatic Engine Start Stop) when they are shut down and the expected ambient temperature will be 40 degrees F or less, the rules (at least on CSX) were for the cooling system to be drained to prevent damage from freezing as the cooling system is still plain water - not antifreeze.
Locomotive cooling water has used an anti corrosion treatment for decades. It gives the water a green color that looks like anti freeze but is supposed to be non toxic. It still makes a nasty looking puddle when it drains onto the ground.
I’ve seen green, pink and purple in water sight glasses over the years. Not to mention plain old clear water after we refilled one that ran out.
I suspect and hope that the railroads now use the borate/nitrite treatments, as opposed to the chromium compounds that became infamous after the Hinckley, CA groundwater contamination case (Erin Brockovich).
The ‘non-true-diesels’ in this context will almost certainly be “distillate engines”, like the original powerplant in the Union Pacific M-10000. These are fascinating in their construction and operation.
There is some material on the Web from a group that actually restored one of these engines, in a railcar, to operation. The engine has comparatively large bore, and runs with high compression, but uses spark ignition for timing – the engine in question having 4 plugs per cylinder!
Naturally as soon as proper solid injection, either with injection pumps improved a la Cummins or with ‘jerk’ pumps, was worked out, the compression-ignition Diesel cycle offered better economy with fewer compromises – the GM 2-stroke directed research that culminated in the 201A and then 567 being a compelling example.
For fun, look up Fritz Huber’s engine for the Lanz Bulldog, an engine that can idle at zero net rpm. There are a number of videos that show the starting ritual, often involving a somewhat lavish amount of flame, and others that show the ‘dance’ when the engine is run very lean. These always make me think of the original Thernolokomotive fiasco, although of course very different principles were involved in detail design…
A “true” Diesel is an engine that uses a true Diesel cycle, where fuel is injected slowly to maintain constant pressure in the power stroke. Most diesel engines are effectively using the Otto cycle (combustion takes place almost entirely at the beginning of the power stroke) substituting compression ignition for spark ignition.
One of the great innovations that true electronic fuel injection brought to compression-ignition direct-injection engines is the ability to perform both pilot injection and modulated main-charge injection, to give the best ‘compromise’ among constant-pressure rise, pressure rise relative to crank angle, and high-speed capability.
Ford apparently got into a little trouble when it converted the VT365 schoolbus engine for higher performance. Apparently the original program for pilot injection did not recognize that the flow from the nozzles in this application was supersonic, and the resulting shockwaves caused ‘trouble’ with the subsequent lightoff of the main injected charge. Quickly and quietly pilot injection disappeared from the engine program…
That was probably the least of the many, many problems with those engines, and perhaps the only one that Ford fixed on their own.
If VT365 sounds foreign, Ford branded them as the 6.0 and 6.4 Power Stroke engines…