Douglas Bearcat engine

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Lars Odeen

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The success of the model A in airplanes seems to be due to the long front bearing and making torque at low rpm. Maybe instead of converting car engines we should be looking at tractor engines.
 

TFF

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I got a Continental in a Lincoln welder. Pretty much a baby A Ford like engine. On a mag too. Both Continental and Lycoming made other engines.
 

challenger_II

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Lycoming... Think "Auburn"! Is a reason why E.L. Cord bought the company ! :)
As for your Lincoln SA-200, I have always drooled over the notion of trying one of those engines in a Piet'ish creation!
 

TFF

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I think one could just make a lower crankcase out of aluminum. Pick an off the shelf crankshaft and timing gear. My Alfa Romeo 4 cylinder engines are about as simple a crankcase casting as there can be. Literally a box on top for the cylinders, and a box on the bottom for the crank. A box with three partitions and you have 5 main bearings after machining. Machine one side for cam drive and the other for output. The biggest problem for home casting would be the amount of aluminum to melt.
 

Dan Thomas

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I think one could just make a lower crankcase out of aluminum. Pick an off the shelf crankshaft and timing gear. My Alfa Romeo 4 cylinder engines are about as simple a crankcase casting as there can be. Literally a box on top for the cylinders, and a box on the bottom for the crank. A box with three partitions and you have 5 main bearings after machining. Machine one side for cam drive and the other for output. The biggest problem for home casting would be the amount of aluminum to melt.
Aircraft engine crankcases often have a lot of magnesium in them, for hardness, stiffness and strength. Some are almost all magnesium. I think that's beyond the home foundry. Flammable beyond belief. Maybe other aluminum alloys would be strong enough for a low-power engine.
 

TFF

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Homebuilt does not have to be space age and the lightest. We are talking cast iron Ford engines in 1930s planes, so anything is probably better. A sturdy regular aluminum engine might not be as light as all the tricks. It’s a home made engine. It’s about the challenge just like building the plane. Who builds the most advanced airplanes? Almost no one. Even the composite planes are not cutting edge at our level. Yes, no one is casting magnesium in the USA in their garage. There is no need. There are a lot of more impossible topics this site discusses.
 

Tiger Tim

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On the subject of just making the whole thing, I kind of wonder if an air cooled Funk-like creation could just be CNC’ed into existence. You can get all of the moving internal parts for a Model A brand new out of a catalogue, including forged counterweighted cranks and domed lightweight pistons. Crib the combustion chamber shape from the Model A police head (they were a little hotter then and quite rare today) and turn it faster and surely 60hp or more must be within reach.

…but that‘s not really what this thread is about,
 

TFF

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Starting with a chunk of aluminum that big, is the real issue. That is a chunk of money. I remember looking at a CRJ 200 windshield frame and realizing that both sides were really one. They had to start with a 5’x10’x 3’ chunk of aluminum to mill that out. That is a lot of swarf. Surely they cut some out the windows for other fittings. Starting with a casting let’s one save some money, even if that casting is rough.

All these ideas require talent and tools. None are call up Bob the machinist and order one. Bob better be your dad if you do. It has to be one’s passion. I had a friend who’s dad loved machining. He made two of those live steam engines you ride on. That is what it takes. It’s not that the engines can’t be made, it’s about one doing it. Plenty of people have this type of hobby. They just are not here. It won’t ever be commercial. If you gave away plans, one maybe two others would be built if it was cool enough to be cool. One might be able to repurpose a cracked block which would be nice. If one has figured it out, one might get a trade school to whittle away at it for a couple of years, but you can’t cry if a student kills it. The only way to guarantee it works is be the one with the tools in your hands.
 

Tiger Tim

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Back to the Bearcat itself: what if it had period airplane engine cylinders on it? Is there anything that stands out as cheap, available in the US, and for some reason not desirable on its factory crankcase in the 1930s? Maybe the trickiest part is that it can’t care which port is intake and which is exhaust because near as I can tell the Bearcat used a relatively normal Model A cam that had lobes which went exhaust-intake-intake-exhaust-exhaust-intake-intake-exhaust from one end of the cam to the other and the exhaust pipes on the Bearcat Gere Sport support my position.
 

TFF

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I’m guessing Dayton is a popular name. Here is the Bear.

I would think if airplane cylinders were used, they would be LeBlond, A-40 or A-50. I don’t think it would be Harley or Indian at that time.
 

Tiger Tim

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I’m guessing Dayton is a popular name. Here is the Bear.
The trouble is the Dayton Bear and Douglas Bearcat were different engines separated by at least a decade but period publications even seem to mix up the names.

I would think if airplane cylinders were used, they would be LeBlond, A-40 or A-50. I don’t think it would be Harley or Indian at that time.
Indian would be a flathead cylinder at the time and Harleys aren’t really the right configuration of ports or pushrods or anything to work. There were a few other smaller manufacturers but given the sheer displacement I’m losing hope in the possibility that they’re motorcycle jugs.

I thought the A-40 had Siamese cylinders bolted. I know the O-145 are cast in
Yes, the A40 has Siamesed iron(?) cylinders bolted up to an aluminum or magnesium case, I forget which it was. In any case a flathead has been ruled out on the Bearcat. I was looking at 65hp Franklin cylinders today thinking they might be able to work but again I don’t think the timeline works.
Too early for an A-50, and One would be needing a good hack saw to get the cylinders off the A-40.
Just an ordinary wrench. Save the hack saw to separate the cylinder pairs into individual jugs for when you want to make an A40 radial.
 
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