WORLD’S SMALLEST TWO-STROKE HOT BULB ENGINE

By Find Hansen

I had never tried to build a two-stroke hot-bulb engine before, only four-stroke engines, so I thought that the time had come to try to build one. The engines I had built before were so called ‘open crankcase’ engines, so this one is open, too, using a cross-head to guide the piston-pin. I was, as you perhaps can see, very inspired by Swedish two-stroke engine builders like Beijers Kristala, when I designed and built the engine.

You might think that it would be much easier to build a two-stroke engine compared to a four-stroke but it is actually more complicated, especially when you build it as an open crankcase engine, using a cross-head.The cylinder is rather complicated to construct, too, because of the built-in intake - scavenge - exhaust channels, which must be separated from each other, and from the cooling water channels.

The two photos above show, my well-proven fly-ball governor controlled injection-pump system, used on my four-stroke engines. It seems to work well on this engine, too. I just had to make an injection-pump cam with two cams, because the side shaft only turns at half the crankshaft speed. 
Photo above shows the side shaft with gear wheels for the fly-ball governor and the crankshaft. To the left under the shaft, the ‘double’ injection-pump cam, the green painted side shaft bracket, and the governor with its connection links. Moving to the right, first the other side shaft bracket, and then the eccentric operated water-pump.
The two photos above show, first, the cylinder and the cross-head guide. From left to right lower in the  photos, is the piston, the piston-rod, cross-head, connecting-rood and the crankshaft big end bearing, and under this in the first photo is the intake valve, shown in more detail below.
And the intake valve in place in the cylinder.
Next photo shows the parts assembled...
... ready to be mounted on the engine base.
Completed fabricated flywheel and crankshaft (above).
Crankshaft bearings.

Engine specifications:

Engine built: 2014.

Engine No.: 1-014.

Engine type: Two cycle, cross-head, hot-bulb engine.

Bore - Stroke: 20 mm. - 32 mm.

Fuel: Mineral turpentine or kerosene, injected into a vaporiser tube, mounted in the hot-bulb.

Preheating of hot-bulb: Adjustable blowtorch, using lighter gas as fuel. Preheating time 2-3 min.

Injector type: Adjustable spring loaded needle valve injector, adjusted to open at 10 Bar. 

Compression ratio: 8-1.

Lubrication: Mineral engine oil with a grade of 15-40.

Cooling system: Water cooled using water-pump.