Back to true diesel model engines.
Vertical A frame Diesel Engines.
In 1995 I tryed to build a true diesel model engine with governor controlled injected fuel,
but with no succeed, it ended up to be a hot bulb engine (The pictures below)
Hot bulb Engine No. 1-95 Bore--Stroke 20mm--36mm Fuel: Turpentine
12 Cubic. True Diesel Model Engine
Since I build hot bulb engine No. 1-95. I have dreamed of building a true diesel engine again,
and now I have one running. The engine do not use a pre camber, but has direct injection.
The engine is vertical, and has like engine No. 1-95 an A frame construction, like old Danish
build B&W air blast injection diesel engines.
I build the engine stronger and the crankshaft too, with thicker journals, to withstand the high
compression. Then I drilled an oil way in the crankshaft, to have a continuous lubricated big end,
The pictures showing the engine from different angles.
Starting the engine for the first time.
At the first start attempt I tryed to start the engine using ether diesel start, it started and ran,
but only at the diesel start, not on the engine fuel. At the third start attempt the flywheel
broke loose. I fixed the flywheel, and tryed again still using diesel start, this time it started
and ran on the fuel, I tell you I was happy. Next start attempt still using diesel start, the
engine started, but with an awful noise, The connecting rod was bended, but luckily nothing
else had happened to the engine. I made a new and stronger connecting rod, now 6 mm.thick,
the old one was 5 mm. thick
The picture show the bended 5 mm. thick connecting rod below the new made 6mm.
At the nezt start attempt I thought no more diesel start, why not try to use your wife`s
hair dryer. I tried the hair dryer, and when the engine was about hand warm, I tried to start.
I could not at that time hand crank the engine because of the high compression, so I used
an electric drill machine, and to my surprise, it started and ran.
Since then I have made experimentals with the injection pressure, the injection timing and
different kind of fuel, so now it is possible to hand start the engine from cold. I found that
it is very important that the injection timing it right, a few degrees before or after the right
point, and the engine will be hard to start, and not run properly.
" Engine Handles "
The picture show my fingers on the governor spring handle, to adjust the speed.
This is a handle coupled to the governor system, to stop the engine, or to change the speed manual.
This is the handle that operates an eccentric on the inlet rocker arm, to change the stroke of the inlet valve, thereby changing the compression pressure.
I found that it was very god, to have the ability to change the compression
pressure when I had my experiments with the engine.
When the handle is in its outer position, it works like a de compressior.
My fingers on the injection pump handle to bleed the fuel system.
I use as you perhaps can see, the same well proved governor controlled
injection pump system, as on my previous buil hot bulb engines, it seem
to work very god on the diesel to. I just had to change the injector a bit,
with a build in non return spring loaded 1,5 mm. ball valve, and then atjust the 15 degrees needle valve to a higher opening pressure.
I was afraid that the injection pump would not stand the high injection pressure, but it did.
Engine specifications.
Engine build: 2011
Engine No.: 2 - 011
Bore - Stroke: 20 mm. - 40 mm.
Compression ratio: 21 - 1
Fuel: Kerosene, mixed with 2 % two-stroke mineral engine oil.
Engine lubrication: Mineral engine oil with a grade of 15 - 40 to 20 - 50
Engine cooling system: Water cooled, using water pump.
My thoughts about building a small scale true diesel engine.
1. The compression must be about 100%, with no leaky piston rings, garskets ore valves,
because the compression heat is the only igniter.
2. The compression ratio should at least be 20 - 1 for an easy start and properly run.
If the compression ratio is low, say 16 - 1, the engine need to be pre-headed a lot
before started from cold.
3. The injector must atomize the fuel very god, because the compression heat is the
only thing to vaporise the fuel before it is ignited.
4. The engine should have som kind of governor controlled injection system, without
a system, the engine would be very difficult to controll when running.
5. Using a light fuel as kerosene instead of diesel is better, because it vaporise and ignite
more easy and burns much better with only a little or non smoke.
6. The crankshaft, crankshaft bearings, big end bearing, piston pin and connecting rod,
must be made bigger - stronger, to with stand the compression - combustion pressure.
Because the load on a say 20 mm. piston, with a compression ratio of say 21 . 1
is about 160 kg. and when the fuel is ignited, the load is about 300 kg. and if
pre ignitions appear (Diesel knocking) the load rises to about 400 kg. It is wonder that
the engine will stand this heavy load. Also must the hole engine construction be made
stronger.
7. The main bearings and especially the big end bearing should have a god continuous
lubrication, while the engine is running.
Watch the engine running.