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Half-Breed Hot Tub/Bulb/Oil Fuel

Sooty Jim

I write a column in Diesel World magazine called "Vintage Smoke." It's about early diesels, which includes oil engines (semi-diesels) and things leading up to them. I've been intrigued by the half-breed engines and am looking for some connections to them on the diesel family tree.

I have spoken with a couple of half-breed operators that have hot-tube/bulb versions that do not use a spark plug. All I have see are run on propane but I have been told, but have not been able to verify, that some used fuel oil. Can anyone point me in the direction of those? My resources on the half-breed is limited and I haven't yet found a connection.

If I can find the slightest connection to oil engines, e.g. hot tube/bulb fueled by oil, I will have the justification for a story on the half-breeds. There have been a lot of "diesel conversions" over the years and if half-breeds were run on fuel oil, they would be the first... maybe.

Bill Hazzard

Last Subscription Date
As far as I know there were not any oil engine conversions for steam engines, they were all gas engines since the gas was free. They were hot tube ignition only, no hot bulb surface ignition engines.

Hot tube and hot bulb are completely different ignition systems. A hot tube just provides the heat to ignite a already mixed combustible mixture, just like a spark plug. A hot bulb's job is to vaporize the fuel and add heat for ignition so that when hot air enters from the cylinder due to compression, the added heat from the bulb causes ignition.

Andrew Mackey

Last Subscription Date
Bill has it right. Hot tube and hot bulb 2 seperate ignition systems. The hot bulb is used in oil engines, a liquid fuel is injected onto the heated surface of the hot bulb which ignites the fuel. Timing of the injection and duration provide the power and the ability to govern speed. There is no throttle nor restriction on the air supply. Compression is usually between 5 and 7 to one and the operation is just like a diesel but the compression is too low for self ignition.

A hot tube uses gasseous fuel (natural gas in the field), and is simply a small closed ended tube that ignites a compresed fuel/air mixture. The mixture ignites in the tube and a flame front travels back to the main charge in the combustion chamber. When the half breeds wee built, they did not use liquid fuels. The crude oil pumped did not vaporize easily to be used as a fuel.

There were some oil engines used to pump oil, St Marys I believe was one of them, used crude from the well. Crude made a poor fuel though, it tended to coke up the bulb with carbon and mineral deposits from impurities, and was abrasive to the oil pump/injectors too. You have to remember that oil engines were purpose built, not converted as half breeds were.

Perhaps you could write an artical on how different, not similar half breeds were to oil engines. Just thinking. Read my articals in the GEM on ignition systems and on the OCSP oil field engine I restored.

Sooty Jim

I recently viewed a Buckeye oil engine, a Model L, that has a hot tube (called a "hot stud") screwed into the ignition bowl. It wasn't used in every engine, apparently, but was useful in certain situations... part load and cold weather I would assume. The depth at which the tube was screwed into the combustion chamber dictated it's effect. This is why I said "Hot Tube/Bulb" just to cover all the bases.

Anyway, this is obviously why I haven't found any references to a half-breed oil engine. Pity!

Thanks for the input. I'll move onto other projects but if down the road, somebody runs across a half-breed oil engine, I'll open this subject again.

Tim B

Last Subscription Date
I thought I saw a Reid conversion at the Gas and oil festival in Sistersville WV a few years ago?