poormansairforce
Well-Known Member
So I've been thinking about the engine situation so many of us have concerning airplanes. I've had this idea in my head for about a year and I still need tear down my son's GY6 engine from his go kart he replaced to weight the actual pieces. This may have been proposed/built before but here is the concept:
Buy GY6 OEM parts for 4 engines except the crankcase, i.e. just the cranks, rods, pistons, cylinders, heads, etc. and build/machine a crankcase to accept all 4 "engines" that redrive a central propshaft. Why do it this way? If it can pass the weight test then you'll have a perfectly balanced engine with a power stroke every 180 degrees. Each opposed pair of pistons move in sync with each other while the other pair does the same but offset 180 degrees. Just like a flat 4.
At 7000 rpm it would make 40 hp. The aftermarket performance parts with bigger bores and strokes could get upwards of 60 hp and 250cc parts would be 70+ hp! And 4 KF450s would be 130 hp. And if your willing to run it up to 10,000 rpm for short periods 190 hp could be had for what would be considered dirt cheap in the aviation arena. You'd be replacing piston/cylinders more often but if you had a need....
Other than the welding up/machining of a crankcase and the gears the parts would be relatively cheap as would an overhaul. Obviously, there are some questions about the longevity, weight, and probably things I haven't even begun to consider. It's just a discussion starter. Here are some really basic drawings to help visualize it. The red parts are the redrive gears and I only drew half cylinders so you can see the pistons.
Some thoughts:
The cranks would need to be rebalanced with just the rotating mass. This means lightening the wheels which is easy to do.
Since they are splash lubricated I would use a dry sump with spray nozzles where needed and pressure lubrication to the propshaft sleeve bearings from a small block Chevy? with seals from the same. We could use as many bearings beside each other as needed or machine one large one.
We are not limited to 4 cylinders, could be 2 or even 6 or more. It just gets physically bigger. But 4 cranks fit so nicely that's how I envision it.
I think this idea has a sweet spot below 100 hp, probably 40-70 hp which is where there is a shortage of engines.
As with a 447 at 2.58:1 we would have 5.16 power strokes/prop revolution so very smooth. But it might sound like a 2 stroke too!
The thing is so small that it might get lost on the front of a plane. That would be great if you want to put a cowl over it but if you want a radial it might not stroke your ego.
Thoughts?
Buy GY6 OEM parts for 4 engines except the crankcase, i.e. just the cranks, rods, pistons, cylinders, heads, etc. and build/machine a crankcase to accept all 4 "engines" that redrive a central propshaft. Why do it this way? If it can pass the weight test then you'll have a perfectly balanced engine with a power stroke every 180 degrees. Each opposed pair of pistons move in sync with each other while the other pair does the same but offset 180 degrees. Just like a flat 4.
At 7000 rpm it would make 40 hp. The aftermarket performance parts with bigger bores and strokes could get upwards of 60 hp and 250cc parts would be 70+ hp! And 4 KF450s would be 130 hp. And if your willing to run it up to 10,000 rpm for short periods 190 hp could be had for what would be considered dirt cheap in the aviation arena. You'd be replacing piston/cylinders more often but if you had a need....
Other than the welding up/machining of a crankcase and the gears the parts would be relatively cheap as would an overhaul. Obviously, there are some questions about the longevity, weight, and probably things I haven't even begun to consider. It's just a discussion starter. Here are some really basic drawings to help visualize it. The red parts are the redrive gears and I only drew half cylinders so you can see the pistons.
Some thoughts:
The cranks would need to be rebalanced with just the rotating mass. This means lightening the wheels which is easy to do.
Since they are splash lubricated I would use a dry sump with spray nozzles where needed and pressure lubrication to the propshaft sleeve bearings from a small block Chevy? with seals from the same. We could use as many bearings beside each other as needed or machine one large one.
We are not limited to 4 cylinders, could be 2 or even 6 or more. It just gets physically bigger. But 4 cranks fit so nicely that's how I envision it.
I think this idea has a sweet spot below 100 hp, probably 40-70 hp which is where there is a shortage of engines.
As with a 447 at 2.58:1 we would have 5.16 power strokes/prop revolution so very smooth. But it might sound like a 2 stroke too!
The thing is so small that it might get lost on the front of a plane. That would be great if you want to put a cowl over it but if you want a radial it might not stroke your ego.
Thoughts?
