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Axial engine - Wikipedia, the free encyclopedia

I was obsessed with axial engines back when i was in high school. I wanted to build an engine where the compression and exhaust strokes had a shorter duration than the intake and power strokes.

unfortunately this duke engine has a number of issues that i can see.

1. the seals on its top end. looking at the video, these are going to have a lot of wear on them. this will limit its life between rebuilds, limit their compression ratios for non bench top engines, and limit the thermal efficiency of the engine.

2. like a rotary engine to increase the rpm's you not only have to accelerate the pistons and crank, but the whole block as well. the engine will not want to speed up, or slow down.

3. overly complex, while having a power output shaft rotate the opposite way of your crank is nice for vibrations, it makes the bottom end more complex.

4. none of the stuff they had showed how they pull the piston down for the intake stroke. i'll just assume they have one, cause otherwise they are being very foolish.
 

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I was curious about #4 too.

Can you explain #2 better?
 

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if it was more efficient wouldn't we see them in super cars are concept bikes? makes me think of a mix between a rotary and propeller engine.
 

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Mexican Hard Shell Taco
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1. the seals on its top end. looking at the video, these are going to have a lot of wear on them. this will limit its life between rebuilds, limit their compression ratios for non bench top engines, and limit the thermal efficiency of the engine.
Wear? Getting good compression out of them when new will be quite a challenge, area for those seals is freaking huge...

2. like a rotary engine to increase the rpm's you not only have to accelerate the pistons and crank, but the whole block as well. the engine will not want to speed up, or slow down.
The "Duke" is an Axial engine, hardly new...

Axial engine - Wikipedia, the free encyclopedia

In fact, pretty old design with many drawbacks.

3. overly complex, while having a power output shaft rotate the opposite way of your crank is nice for vibrations, it makes the bottom end more complex.
The bottom end is not that complex, it is in fact quite simple and it has a built in balancer in the shape of a rotating engine block. That doesn't matter as it is basically a 2 stroke that has seals that will leak like there is no tomorrow and there is no way in hell it can even get close to being compliant with current emission regulations.

4. none of the stuff they had showed how they pull the piston down for the intake stroke. i'll just assume they have one, cause otherwise they are being very foolish.
That big hunk of metal that pushes the pistons into the exhaust/compression stroke also pulls them down. As it is pushing one piston it is pulling another, quite simple actually...

Too simple, all engine power would be transferred to the output shaft via a simple ball joint? Don't think so, at least, it won't be for too long before it wears down to scrap.
 

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The "Duke" is an Axial engine, hardly new...

Axial engine - Wikipedia, the free encyclopedia

In fact, pretty old design with many drawbacks.
hey, that's my link, go find your own.

The bottom end is not that complex, it is in fact quite simple and it has a built in balancer in the shape of a rotating engine block. That doesn't matter as it is basically a 2 stroke that has seals that will leak like there is no tomorrow and there is no way in hell it can even get close to being compliant with current emission regulations.
from the animation i saw it looks like a Suck/Squeeze/Pop/Foie four stroke, with seals that will leak like no tomorrow.

As for complexity, they could have left the block standing still, had a rotating crank shaft with the swashplate (or whatever they call the thingy that drives the pistons in their going up and down) an integrated part of the crankshaft, geared the top plate (intake/exhaust ports and all) to the crank with a 4:1? 2:1? (whatever they need) reduction, and been fine. The rotating block, counter rotating crank, and swashplate driving a separate power output shaft might eliminate vibrations, but it makes the engine much more complex.
That big hunk of metal that pushes the pistons into the exhaust/compression stroke also pulls them down. As it is pushing one piston it is pulling another, quite simple actually...

Too simple, all engine power would be transferred to the output shaft via a simple ball joint? Don't think so, at least, it won't be for too long before it wears down to scrap.
from the animation it looked like the bottom of the connecting rods were little paddle things that just road along the "recipricator" with no way to pull the pistons back down. I'm willing to assume that they have some way of pulling the pistons back down (ball joints, and u-joint are the first things that popped into my head).
 

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Can you explain #2 better?
i'll try, but no guarantees.

they are spinning the block (big chunk of metal that the pistons move back and forth in), the pistons, the connecting rods, and the "resipricator", opposite the direction they are spinning the crank, power output shaft, and swashplate (the lop sided thing they use to drive the moving up and down of the pistons (technically it might be called something else, but i have heard "swashplate" used and ill stick to that term until some cranky person get their panties in a twist.)).

any way these parts have inertia, you have to add rotational kinetic energy to make them spin faster. If you want to make this engine gain rpm you have to add rotational energy to the block, to the pistons, to the connecting rods, to the crank, to the power output shaft, and to the swashplate.

In an traditional engine, you only have to add rotational energy to the crank, flywheel, cams, clutch, and crankshaft pulley.

Sense this axial engine is spinning more stuff, more energy will be required for it to change rpm's.

this greater energy requirement for the engine to change rpm's will make the engine feel unwilling to quickly change rpm's.
 

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so i had a thought about this while sitting in traffic today. it appears that the shaft and counter rotating block are at a 1:1 ratio, right? if that is the case, at 5000 rpm, the pistons are being forced into the outer cylinder wall at over 4000 g's (assumed 12"/ 30cm diameter for the 5 bores) i can't imagine that rings and piston skirts will handle that for very long even with a steady supply of oil. also, the oil will also be forced outward where it will spread on the outer wall (and just the outer wall) of the cylinder bore and the piston will have to scrap it back out of the rotating block... or does this oil pooling (@~4000 g's) actually keep the engine alive? i don't know.

oops, no, with 3 spark plugs it would be a 1:3 rate, so at 5000 rpm, the block would spin at 1666 rpm, which would be ~465 g's. that's still a lot of force between the two. how high is this thing supposed to rev?
 

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they (duke) say it spins faster that other axial engines did, however fast that is. i hadn't thought of the oiling issues this will face.

at this point i think i will file this engine in the beautiful idea ruined by ugly reality section of my mind until one of these engines actually drives by consuming only sky pie and producing only unicorn farts.
 
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