I need some help in determining if this mechanism applied to an engine is really a poor idea:
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Spare no criticism.
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help to tear this engine apart 2
- Thread starter borinotus
- Start date
patprimmer
New member
The cost of a circular bore will be a lot of money.
Regards
Pat
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Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
Seems to me that there is a lot of mass (all the red bits) that is being oscillated rather that rotated and I'd guess it has to be pretty robust to withstand the loads it will be subjected to).
Isn't that going to absorb a lot of energy?
But what I didn't see was how the blue crank continues to rotate even when the red piston carrier stops and reverses.
JMW
Isn't that going to absorb a lot of energy?
But what I didn't see was how the blue crank continues to rotate even when the red piston carrier stops and reverses.
JMW
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2
- #4
borinotus,
I admire your intellectual courage soliciting criticism of your "baby" here on this thread.
While your concept shows lots of creativity, it would not make a practical or reliable IC engine for lots of reasons.
Among the issues that I can see (some of which you seem to be aware of) are:
-manufacturing costs. Machining an accurate toroidal shaped cylinder surface would be very difficult for a new engine. And next to impossible to rework during an engine rebuild.
-size and shape. Based purely on the animations in your website, the height/width of your engine package would be about 8 times the bore size. So an engine with a 4 inch diameter bore would have a height/width of over 30 inches.
-reversing gear loads. Gears must have backlash to function properly. As a result, they don't like reversing loads. These load reversals cause very high dynamic impact loads on the tooth flanks.
-lack of control over valve timing. Accurate, and even variable, valve timing is very important for modern engine performance. Plus, automatic, spring-loaded "check" valves would produce large pumping losses.
-loss of operating clearances due to thermal expansion mismatch and structural deflections in the large mechanism components. Tight clearances between the piston and bore is critical for proper function and gas sealing of piston engines. The rigid structural nature of your "piston" assembly and the relatively large pitch diameter of the toroidal bore in the block, would seem to make it very difficult to ensure adequate piston-to-bore running clearance under all thermal conditions the engine must operate in. This situation would be made even worse with a liquid cooled block and an un-cooled crank assembly.
-poor throttle response. Your engine would likely have poor throttle response due to the high polar MOI's of the cranking assembly.
However, to be fair, your engine concept does seem to have some beneficial characteristics. The gearing arrangement provides a reduction in output shaft speed which would help simplify a car's transmission. And while the height/width dimensions of the engine would be undesirable, the overall length of the engine would be very good.
Best regards,
Terry
I admire your intellectual courage soliciting criticism of your "baby" here on this thread.
While your concept shows lots of creativity, it would not make a practical or reliable IC engine for lots of reasons.
Among the issues that I can see (some of which you seem to be aware of) are:
-manufacturing costs. Machining an accurate toroidal shaped cylinder surface would be very difficult for a new engine. And next to impossible to rework during an engine rebuild.
-size and shape. Based purely on the animations in your website, the height/width of your engine package would be about 8 times the bore size. So an engine with a 4 inch diameter bore would have a height/width of over 30 inches.
-reversing gear loads. Gears must have backlash to function properly. As a result, they don't like reversing loads. These load reversals cause very high dynamic impact loads on the tooth flanks.
-lack of control over valve timing. Accurate, and even variable, valve timing is very important for modern engine performance. Plus, automatic, spring-loaded "check" valves would produce large pumping losses.
-loss of operating clearances due to thermal expansion mismatch and structural deflections in the large mechanism components. Tight clearances between the piston and bore is critical for proper function and gas sealing of piston engines. The rigid structural nature of your "piston" assembly and the relatively large pitch diameter of the toroidal bore in the block, would seem to make it very difficult to ensure adequate piston-to-bore running clearance under all thermal conditions the engine must operate in. This situation would be made even worse with a liquid cooled block and an un-cooled crank assembly.
-poor throttle response. Your engine would likely have poor throttle response due to the high polar MOI's of the cranking assembly.
However, to be fair, your engine concept does seem to have some beneficial characteristics. The gearing arrangement provides a reduction in output shaft speed which would help simplify a car's transmission. And while the height/width dimensions of the engine would be undesirable, the overall length of the engine would be very good.
Best regards,
Terry
Why a toroid?
Why not have each pair of pistons run in a cylindrical chord?
They can be rigidly linked to each other but connect to the gear via a pivot pin (or even a more crude linkage such as found in a ball float arm) that will allow them some freedom to twist slightly relative to the gear as they move in the cylinders but the pistons would actually now reciprocate in a straight line which might confer more uniform wear and less lost energy.
That would allow individual cylinders to be independently repairable and the repairs to be more simply achieved and the components more easily and cheaply fabricated.
JMW
Why not have each pair of pistons run in a cylindrical chord?
They can be rigidly linked to each other but connect to the gear via a pivot pin (or even a more crude linkage such as found in a ball float arm) that will allow them some freedom to twist slightly relative to the gear as they move in the cylinders but the pistons would actually now reciprocate in a straight line which might confer more uniform wear and less lost energy.
That would allow individual cylinders to be independently repairable and the repairs to be more simply achieved and the components more easily and cheaply fabricated.
JMW
ornerynorsk
Industrial
Interesting idea, but oh my, would it be expensive to manufacture!
- Thread starter
- #8
Tbuelna,
Good points. The one about thermal expansion is my favorite. Well, that and cost of course, but that’s so materialistic …(;->). Oh, and backlash too. Could it be possible to spring-load the planet gears against the ring gears?.
On the other hand, with a 4 inch diameter bore you would end up with a 6.5 l displacement aprox. if I do the maths right. That would be quite an engine/compressor. And I just don’t see why the high MOI of the pseudo-rotor would result in a poor throttle response. The pseudo-rotor gives and takes an equal amount of energy at every period of oscillation. It’s not a rotating part so it doesn’t absorb any net energy.
Overall, I think that you’ll help disabuse the author of some cherised beliefs. On a lighter note: why are you assuming that the “baby” is mine?
Best regards,
borinotus
P.S: dicer, jmw: whence the lost energy?
Good points. The one about thermal expansion is my favorite. Well, that and cost of course, but that’s so materialistic …(;->). Oh, and backlash too. Could it be possible to spring-load the planet gears against the ring gears?.
On the other hand, with a 4 inch diameter bore you would end up with a 6.5 l displacement aprox. if I do the maths right. That would be quite an engine/compressor. And I just don’t see why the high MOI of the pseudo-rotor would result in a poor throttle response. The pseudo-rotor gives and takes an equal amount of energy at every period of oscillation. It’s not a rotating part so it doesn’t absorb any net energy.
Overall, I think that you’ll help disabuse the author of some cherised beliefs. On a lighter note: why are you assuming that the “baby” is mine?
Best regards,
borinotus
P.S: dicer, jmw: whence the lost energy?
I assume that each oscilation cycle will lose some energy to the mountings. That is not just a piston reciprocating, it appears to be all at once and the ring gear too.
Unless all that energy is being absorbed into the crank somehow, at least half a cycles worth is going somewhere.
But don't mind me, I didn't figure out yet how the crank keeps turning smoothly in one direction while the ring gear is reversing itself each cycle.
JMW
Unless all that energy is being absorbed into the crank somehow, at least half a cycles worth is going somewhere.
But don't mind me, I didn't figure out yet how the crank keeps turning smoothly in one direction while the ring gear is reversing itself each cycle.
JMW
LionelHutz
Electrical
This reminds me of the MYT engine/compressor. Honestly, it looks like another case of someone with too much CAD experience and not enough practical know-how.
The design will need some type of connecting rod between the gear and each piston. Then, might as well make the bores straight to avoid the high cost of manufacturing the curved bores. Oh, now it has the same design basics as every other engine - might as well just put in a simple crankshaft.
jmw - I'd have to assume inertia of the rotating carrier will carry it through the dead zone.
The design will need some type of connecting rod between the gear and each piston. Then, might as well make the bores straight to avoid the high cost of manufacturing the curved bores. Oh, now it has the same design basics as every other engine - might as well just put in a simple crankshaft.
jmw - I'd have to assume inertia of the rotating carrier will carry it through the dead zone.
- Thread starter
- #11
Just for completeness: there seems to be a Chinese company (who else?) that specializes in manufacturing non-circular gears. They display some amusing real gearings on their website ( Maybe it doesn’t seem so expensive now… 
To JMW (belatedly): LionelHutz is right. If you think about it, it’s just the same as in a conventional 4-cylinder where all the pistons are at a dead centre at the same time and they get past it due to the momentum of the rotating parts, when idling. When the clutch is engaged, the whole mass of the vehicle acts as a giant flywheel.
To JMW (belatedly): LionelHutz is right. If you think about it, it’s just the same as in a conventional 4-cylinder where all the pistons are at a dead centre at the same time and they get past it due to the momentum of the rotating parts, when idling. When the clutch is engaged, the whole mass of the vehicle acts as a giant flywheel.
patprimmer
New member
Single cylinder engines run due to inertia in the flywheel. This case is no more difficult in that regard.
As to machining a curved axis bore and running pistons up and down inside that without undue wear, poor sealing, poor piston skirt durability or high friction, that is another story. I can't begin to imagine the motion created in rings with different effective piston speeds on either side of the piston, nor the difficulty in machining a piston skirt shape to accommodate the curved axis bore. Piston skirts are complex enough in straight bores.
Regards
Pat
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As to machining a curved axis bore and running pistons up and down inside that without undue wear, poor sealing, poor piston skirt durability or high friction, that is another story. I can't begin to imagine the motion created in rings with different effective piston speeds on either side of the piston, nor the difficulty in machining a piston skirt shape to accommodate the curved axis bore. Piston skirts are complex enough in straight bores.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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- Thread starter
- #13
No doubt piston rings would be challenging. But I think there’s a flaw in that design regarding piston skirts. You can basically do away with them because there’s no side thrust on the cylinder bore. Wear on bore and rings should be also minimized because of this.
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