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Steam/ internal combustion conversions

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Hi Everyone. 

I'm new here and I may post topics that have been well discussed before, apologies in advance.

I was reading the interesting post up in the building-from-castings section about 'A Robinson in the Making' where a model is being scaled from a vintage engine.

I'm retired. Back in 2017, an engine collecting friend (who still had to go to work everyday) had me do the driving to collect an engine he'd purchased.  This ended up being about 800 miles from my location in southwest Missouri, to a little town in eastern Ohio, just on the Ohio river. 

I collect old engines, but not as early as my buddy.  He has several engines with hot tube ignition, the oldest I have use igniter points in the combustion chamber.

Until I made this trip for my friend I wasn't aware of how common steam to internal combustion conversions were say in the 1890 - 1900 time frame.  The engine shown below was an Innis steam engine having had a Bessemer conversion kit installed way back in the early days.  The engine collecting community over here refers to these as half-breed engines, -- I'm not sure if that term is generally used, I don't want to give offense.

So, I'm curious if these steam/IC conversions are modeled often. For some scale the flywheels are 51 inches in diameter.  The engine weighs around 2000 pounds.

Very interesting - I had never heard of that kind of steam-to-IC conversion before. Did some searching, and found this video of one running:
Apparently there were a lot of them done for use in the oil fields, running on natural gas.

Would be great to see pictures of some of your engines!

I'd never heard of this either, but it does make sense that there would be a lot of conversions during that time, toward the end of steam and early combustion engines.

Very interesting.  I learn something new on this forum every day!


OK - now I'm curious too .... how does it work  :headscratch:

Nice video Chris - thanks for posting it.

It's a two-stroke without crank case compression or a blower ...!... so does the cylinder part closest to the crank work as the crankcase part of the equation ?

Best wishes


OK a little Google Fu later (From Oil City Boiler Works / :

--- Quote ---The cross-breed explained
The Oil City/South Penn gas engine operates, and is constructed as follows: As I stated earlier, this engine started life as a steam engine. It was then converted to being an internal combustion engine, using the natural gas from the well, as fuel. The now replaced piston and cylinder are made entirely of cast iron. The actual cylinder is double ended. The charging (intake) end has a bolt pattern that matches the original steam cylinder’s mounting, to the engine’s bed frame assembly. An end cap is sandwiched between the cylinder itself and the engine bed frame. This cylinder end cap has a packing gland built into the center.. The end cap and the cylinder are both held in place against the block/base, with nine 5/8″ studs and nuts There is a deflector cast into the end cap, on the cylinder side, that helps direct the air/fuel mixture into the transfer passage, within the cylinder casting (it is pictured later).

The piston is attached to a 1 ¾” steel shaft that passes thru the end cap, the packing gland, and then is attached to a yoke and a set of ways, as in steam engine practice. The piston rod is locked in place by means of a double wide 1 ¾” nut, cranked tight against the crosshead yoke. The yoke (or cross head), in turn is attached to the connecting rod, which in itself is attached to the crank throw. The rear of the piston is supported by the yoke and ways, which also contain the angular thrust developed by the crankshaft and connecting rod. The motion of the piston is strictly linear,, that is, it only travels up and down the bore. Angular forces generated on the power stroke (strong), and on the intake stroke (weak), work against the yoke and crankshaft. The crankshaft has Babbitt bearings on the mains, lubricated by oil galleys and felting. The con rod bearings are made of bronze, and uses the box and wedge type of retainer, at both ends. The con rod bearings are grease cup lubed. The cross head ways are lubricated by felt filled wells, on top of the way guides. SAE 50 oil and cup grease are used for lubrication of the slides and bearings.

On the compression stroke, the intake charge is drawn into the rear section of the cylinder. As the piston proceeds up the bore, the air must pass a flat poppet type valve, which also admits the gas charge. This is accomplished as follows: The poppet valve rests on a flat surface that is approximately 3 ½” in diameter . It has a shaft that is about 5/8″ in diameter, and is about 8″ long. The valve seat is a combined device, made of cast iron, that allows gas and air to enter the intake port at the same time. Air passes directly thru the seat assembly, from an inlet set to one side. This inlet is 2″ in diameter with a 2″x1 ½” reducer screwed into it. The purpose of the reducer is to make a slight restriction on the intake, like a venturi in a carburetor or a mixer. Around the perimeter of the intake seat, are a series of 3/16″ holes, drilled about 1 ¼” apart, that go to a separate passage, that is cast into the inlet. This passage is for gas, and it is supplied by a ¾” pipe that is connected. The poppet valve is held shut by means of gravity, and a light weight spring helps prevent chattering during operation.

At the top of the compression stroke, the inlet valve closes, cutting off the flow of gas, and preventing backflow of the air/gas mixture back out the inlet. As the piston recedes in the bore, on the power stroke, the charge is compressed. When the piston uncovers the transfer port, as it travels down the bore, the compressed fuel-air charge then travels thru the transfer passage, goes thru the transfer port openings, and passes the top of the piston into the combustion chamber. The deflector on the piston directs the air/fuel mixture toward the combustion end of the cylinder.

Again as the piston rises, the transfer port and exhaust port are closed, and the charge is then now compressed within the combustion chamber. This compressed fuel – air mixture is then forced into the hot tube, where it is ignited. When the mixture ignites in the tube, a flame front travels back out the open end of the tube, and then ignites the rest of the mixture in the cylinder. Power generated by the expanding burning fuel pushes the piston down the bore on the power stroke, until the exhaust port is uncovered by the piston. At this point, the spent charge exits the cylinder, and then shortly after that, the next intake charge enters as the transfer port is again opened. The cycles then repeats, if all is well. The operation is the same as a Bessemer 2 stroke, and in some circles, I have heard that Bessemer actually had a license agreement with South Penn, to allow South Penn to build these types of engine components. Besides building the Half-Breed engine parts, South Penn actually built their own engines, into the early 1900s. The company apparently ceased operations in approximately 1910.
--- End quote ---

And just for those that has to ask - what is a Hot Bulb :

--- Quote ---The hot tube explained
For those of you who are not familiar with hot tube ignition, I will make a brief explanation. A hot tube ignition system works as follows: As the firing charge is compressed within the working cylinder, a small portion is forced into the body of the hot tube itself. The hot tube, typically, is a small diameter (¼” to 3/8″ in diameter) steel closed ended tube that is heated to incandescence, by a small external flame. This heated area can be from a dull red heat, to a bright yellow orange. As the fuel – air charge hits the red/orange heat spot on the hot tube, it ignites, sending a flame front back into the cylinder, which in turn ignites the rest of the charge within the power cylinder. Varying the heat, or location of the flame, will alter the timing, By raising the heat toward the closed end, you retard , and lowering toward the base, or adding more heat, you advance. Timing can never be retarded past TDC. This is due to the nature of the hot tube’s operation. The fuel-air mixture is compressed to its highest pressure, at TDC. At TDC, pressure is at its peak, and the mixture cannot be pushed any further up the tube. Therefore, the latest point of ignition occurs at TDC. It can be extremely advanced though, to the point that the mixture will fire almost immediately after the engine begins to compress the mixture. This super advanced timing can do real damage, if it is not remediated quickly, by either cooling the heating flame, or moving it toward the closed end of the tube.   Engine shutdown is accomplished by removing the flame altogether – this cools the hot tube below the fuel/air mixture ignition point, and the engine then coasts to a stop.
--- End quote ---

Funny - I know of many Hot Bulb Engines used in Fishing Vessels here in Denmark, that only needed the outside flame for starting the engine - after that it was self sustained .... "Killing them" required you to shut of the fuel for the engine.


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