The semi diesel engines , also knows as the hot-bulb engines , are a type of internal combustion engine where fuel is ignited by touching a red-hot metal surface, and also oxygen, which is compressed into the hot-bulb chamber by the rising piston.
Most hot-bulb engines were made as one cylinder, low speed two-stroke crankcase scavenged units. This hot-bulb engine one the other hand, was made pre World War ll and it burns a charcoal fire on the cylinder head, and heats the hot-bulb. Pretty amazing to see something from the past.