New diesel engine

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Daleandee

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The "stepped piston" engine is very intriguing to say the least ...

http://www.bernardhooperengineering.co.uk/opads.htm

http://papers.sae.org/940400/

http://aut.researchgateway.ac.nz/bitstream/handle/10292/6846/P%20IMechE%20Propulsion%20Systems%20for%20UAVs%28300NA%29.pdf?sequence=2&isAllowed=y

That last link has some very detailed information ...

EDIT - Here's another good presentation: http://www.ukintpress-conferences.com/uploads/SPKEX14/d2_s0_p2_peter_hooper.pdf

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
143.7 hours / Status - Flying

PS: Hopefully one of these will be available/affordable before I wear out the Corvair! :gig:
 
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pictsidhe

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I'm wondering how the top cylinder and rings will wear without oil. One of my engine books suggests that a centrifugal supercharger is well matched to a 2 stroke. Seems easier, too. Don't patents expire after 25 years?
 

Swampyankee

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I'm wondering how the top cylinder and rings will wear without oil. One of my engine books suggests that a centrifugal supercharger is well matched to a 2 stroke. Seems easier, too. Don't patents expire after 25 years?
Centrifugal blowers are used by most two-stroke diesels; they tend to be more efficient than positive displacement pumps, like Rootes blowers or piston pumps.
 

Vigilant1

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That's a cool concept, lots of nice features. Maybe the oiliness of diesel fuel, together with some modern vundermaterials, takes care of the lubrication requirements of the top cylinder. It looks like Mr Hooper's designs (at least some of them), used a small amount of metered oil (total loss system) to lubricate the top cylinder. It's a bit of a PITA, but not a showstopper.
 
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Hot Wings

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Don't patents expire after 25 years?
In as little as 3 1/2 years - if you don't pay the maintenance fee on time. Normal is now 20 years, but there are apparently some kinds of "legal shenanigans" that can effectively get the patent updated or reissued and start the clock over. Haven't bothered to investigate all of the details but it's generically referred to as Evergreening.
 

cheapracer

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I'm wondering how the top cylinder and rings will wear without oil.
Oil and or oil vapour is fed through fine holes between the 2 upper piston rings. Some gets from the lower chamber as well via being washed by the passing fuel and if no fuel, vapour. You would be surprised how little it takes.


Don't patents expire after 25 years?
If you read the succession of Hooper's patents, you will see he renewed via small modifications using is own previous artwork as reference. I forget the date of the last one, but it wasn't that long ago.
 

Vigilant1

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Oil and or oil vapour is fed through fine holes between the 2 upper piston rings. Some gets from the lower chamber as well via being washed by the passing fuel and if no fuel, vapour. You would be surprised how little it takes.
For aviation use, I wonder if you could just mix the oil (50:1?) with the fuel rather than depend on the metering system for the oil lube (same as the Mazda fliers do). It's more reliable, lighter, and not much trouble.

In the car biz it is said that "safety doesn't sell." Maybe that's true with airplanes, too, but a lightweight, practical GA engine that uses a fuel with a flashpoint higher than 100 deg F (Jet A, diesel, etc) would be a significant advancement in small airplane safety.
 
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Swampyankee

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For aviation use, I wonder if you could just mix the oil (50:1?) with the fuel rather than depend on the metering system for the oil lube (same as the Mazda fliers do). It's more reliable, lighter, and not much trouble.

In the car biz it is said that "safety doesn't sell." Maybe that's true with airplanes, too, but a lightweight, practical GA engine that uses a fuel with a flashpoint higher than 100 deg F (Jet A, diesel, etc) would be a significant advancement in small airplane safety.
Well, lube oil would probably muck up the injectors. It's not unusual for diesel injectors to run at 10,000 psia or more; at those kinds of pressures, lubricating oil frequently has some odd properties.
 

cheapracer

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For aviation use, I wonder if you could just mix the oil (50:1?) with the fuel rather than depend on the metering system for the oil lube
As a diesel with it's natural lubricating properties it may be ok by itself, not 100% sure.

I do know the CITS 2 stroke is fine with oil vapour that is sent up through it's piston shaft and exits between it's 2 rings to lube the bore.

EhvBB.png
 

tspear

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I see a bright future for clean and economical 2 strokes.
I am pretty sure a two stroke engine by its very nature is less efficient then a four stroke. The question is if the two stroke can deliver more power per pound to reduce the weight to make up in the lack of efficiency or reduce the parts count to increase reliability to the point it is an overriding issue(ports versus valves for example).
From what I see when you look at the Continental CD135, CD155, CD230, EPS (Flat V) and Deltahawk; the answer is not likely anymore.
I think they missed the market.

Tim
 

cheapracer

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I am pretty sure a two stroke engine by its very nature is less efficient then a four stroke.

The question is if the two stroke can deliver more power per pound to reduce the weight to make up in the lack of efficiency or reduce the parts count to increase reliability to the point it is an overriding issue(ports versus valves for example).
Besides the world's most efficient engine is a 2 stroke, there's millions of 2 stroke engines running around that are incredibly more powerful per pound than 4 strokes. Anywhere from double to 4 times the hp per lb dependent on cylinder capacity.

It makes me wonder why these myths and lore about 2 strokes continue, admittedly the antiquated pieces of miserable 1960's tech 2 stroke rubbish that flyers use doesn't help, but dirtbike, snowmobile and jet ski users know better.

2 stroke's fail when compared to a 4 stroke is emissions output and space for the exhaust, but both have been turned around in recent years.

165 hp at 90 lbs, what more could you want ...

https://www.rotax.com/en/products/rotax-powertrains/details/rotax-850-e-tec.html

Mercury and Evinrude 2 stroke outboards not only meet Californian emissions law, they are now cleaner than many of their 4 stroke counterparts.
 

tspear

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Besides the world's most efficient engine is a 2 stroke, there's millions of 2 stroke engines running around that are incredibly more powerful per pound than 4 strokes. Anywhere from double to 4 times the hp per lb dependent on cylinder capacity.

It makes me wonder why these myths and lore about 2 strokes continue, admittedly the antiquated pieces of miserable 1960's tech 2 stroke rubbish that flyers use doesn't help, but dirtbike, snowmobile and jet ski users know better.

2 stroke's fail when compared to a 4 stroke is emissions output and space for the exhaust, but both have been turned around in recent years.

165 hp at 90 lbs, what more could you want ...

https://www.rotax.com/en/products/rotax-powertrains/details/rotax-850-e-tec.html

Mercury and Evinrude 2 stroke outboards not only meet Californian emissions law, they are now cleaner than many of their 4 stroke counterparts.
I was ignoring traditional gas engines and only thinking of compression ignition.
If you want to find super efficient engines, they are all really constant speed. e.g. The huge diesel engines used in ships.
Now find a two stroke engine which is used in a variable speed application which beats the performance of a four stroke (again, diesel only). I have yet to see one of these unicorns...

Tim
 
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