Vibration free powerplant.

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Niels

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- how does the engine generate enough excess torque to turn the props?
To proced the explanation.
If the two pistons do same work,have same friction and underside pumping and the two propellers are equal but mirrored, generators will take no power but Will continiously compare voltage and phase and try to be in step.
If piston masses are the same there will be no mass forces or torques coming out as they cancel.
Problem is the propellers.We can either separate them so far that they do not intefere but it takes mass space etc.When a propeller blade goes into the common zone as shown on picture it will be unloaded that is try to accelerat more than sister prop that has all three blades doing full work.Next moment Sister send one blade into the zone an unloads by accelerating but is running the opposite direction.As said before the first order torque reactions will cancel but the propeller blade number order will not and be unpleasant..The electronic saving can be to take Power from one side and offer to the other three times per engine rev and the we will have turbine smoth power from a single cylinder two stroke even if it misfires s such creatures sometimes do.
 
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n3puppy

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If piston masses are the same there will be no mass forces or torques coming out as they cancel.
Problem is the propellers.
That is what I was thinking - Propellor loads - but a little different view.

What happens in a climbing turn?
Load is different on inside and outside props due to arc of the turn.

Granted not as bad as widely spaced twin engines mounted on different wings. But still there.
 

Niels

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I have tried for years to design a mechanical synchro gear and have never succeded in thinking this is it.The electrical solution has been known to me to work since 1992 but I have erroneously thought it to heavy.
Greenass532 put in a link to the Emrax motors of Pipistrel fame and let me try to speculate how heavy they will be for synchronising two threebladed props going into a common zone.Each prop uses 15kWthat means 5kW to each blade as mean value.Let us asume that it frees 2.5 kW for trouble making and has to be kept in check.I think it is wildly pessimistic but it defines the playing field.The torque of 2.5kw at 60 rps is 7Nm.
The Emrax cataloque
Emrax

The Emrax 188 handles 50Nm and has a mass of 7kg or a machine of 1kg handles 7Nm ,more or less.
The 1.2litre pure engine was about 22kg plus two kg makes 24kg for completely vibration free 30kW engine and good fuel economy as well.
 
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Niels

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That is what I was thinking - Propellor loads - but a little different view.

What happens in a climbing turn?
Load is different on inside and outside props due to arc of the turn.

Granted not as bad as widely spaced twin engines mounted on different wings. But still there.
I will start to sell to powered parachutes and ultralight trikes.Aerobatic planes are for my inheritors
 

PMD

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Do you have any idea what it takes to design, prototype, test, re-design and tool up to make an engine???? If your name isn't Bill Gates, it is a number for both years of work and cubic dollars/pounds/Euros that will leave you flat footed. Take note of some of the discussion in the Frankenengine thread - we were discussing a guy who started with an existing UAV engine design and tooling and tried for 15 years and a LOT of money to de-bug it to a satisfactory level. He was a mechanical engineer and a FAA/PMA manufacturer of airplane parts with all of the facilities needed to do so. He died of old age before it really reached marketability status.
 

Niels

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He was a mechanical engineer and a FAA/PMA manufacturer of airplane parts with all of the facilities needed to do so. He died of old age before it really reached marketability status.
Sounds like a very good way to spend a life
 

Daleandee

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I think I figured it out .... it is a powerplant that does not exist ... it does not run .... thus it is truly vibration free ..... hehe

.
Any powerplant will qualify as vibration free if it ain't running. As odd as it sounds, the loudest engine I ever heard had just quit on me during take-off. ;)
 

Pops

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My 1835 VW, as mounted in the Longster, weighs 137#.
My 1835 cc VW engine firewall forward weight including engine mount , prop, oil cooler , etc. Unbolt the engine mount from the firewall and weigh, is 141 lbs and I tried to save every ounce.
 

Armilite

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==============

Neils, I have to ask WHY? With over 32+ different 2 Strokes made in the World. Most smooth out as the rpm increases. Most all 2 Strokes are not really Balanced, Cranks are also out of Phase. On most of these Ultralights and Small Kitplanes, there is so much Slop in the parts. The Mazda Rotary is one of the Smoothes out there. Stock Engines are good up to 10,000rpm. The one used at Indy was turning 18,000rpm and WON Indy that year. The same goes for most 4 Strokes. How many 4 Strokes have been discontinued in the World? Learn how to Improved the Existing Engines out there would be more useful to people.
 
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PMD

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If You dont see the potential advantage relative to state of art engines, why bother?
You are suggesting going down a road (opposed piston, opposed cylinder) that began around 1885. It has been very successfully done in the past (Junkers plus MANY marine and land transport examples) but the elements of modern technology required to re-introduce this design are very different from what you propose. Take a look at what Achates Power has been doing. Also bear in mind they have BILLIONS available to play at this table, not to mention a very deep field of academic and industrial talent and experience.

Done right, this technology has the potential to be Rotax power/weight ratio (something Lyc and Conti can only dream about).
 

Niels

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Take a look at what Achates Power has been doing.
, this technology has the potential to be Rotax power/weight ratio (something Lyc and Conti can only dream about).
I believe I can make power/mass better than Rotax.
If not I would not waste Your valuable time here.
The mechanical layout of Achates is to complicated but they must have done some very good and expensive work in piston rings and cylinder ports.
 

wsimpso1

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After looking over the associated documents, I have figured out more of the sketches.

Intake is at one end, exhaust at the other, piston is much longer on right end to make the porting work. So right away the pistons have different weight and will produce a significant left-right vibe in first order of rotation. Balancing the pistons to same mass can eliminate this. As drawn that might prove difficult.

In Dr Junkers design and in the Gemini diesel, the crankshafts rotate in the same direction. This nulls out 1st order block oscillation from side to side from the unavoidable imbalance between big end of the con rod and the crankshaft counterweights, but introduces 1st order roll axis excitation of block. Usually this is a good trade. Why is this design going for opposite rotation direction of crankshafts?

Some of the drawings seem to imply crankcase pumping for induction which usually means either mixed gas-oil or a total loss oiling system. Am I seeing this correctly? Junker, Gemini, and Deltahawk all use closed loop lube.

Dr Junker used a two stage step up gearbox and a centrifugal super charger to provide induction air, while the Gemini design uses a Roots style blower and then turbocharging. If this scheme is not going with crankcase pumping, then how is it to get induction to work?

More questions as I noodle on this scheme.

Billski
 
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PMD

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I believe I can make power/mass better than Rotax.
If not I would not waste Your valuable time here.
The mechanical layout of Achates is to complicated but they must have done some very good and expensive work in piston rings and cylinder ports.
To get a 2 cycle diesel (or spark ignition) to meet current emissions standards you are very right. What took 2 cycle diesels (that were VERY common in uniflow form from Detroit Diesel and Commer TS3) out of the road marketplace was control of lube oil and ancient fuel injection technology. Oil control still VERY challenging but HPCR injection technology solves the other big issue. Achates core engines are VERY simple, but to achieve automobile emission levels, the turbocharger/inlet/EGR systems will be very complex - and completely unnecessary in aviation use. Cylinder ports are another topic altogether - but I
 

Armilite

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You are suggesting going down a road (opposed piston, opposed cylinder) that began around 1885. It has been very successfully done in the past (Junkers plus MANY marine and land transport examples) but the elements of modern technology required to re-introduce this design are very different from what you propose. Take a look at what Achates Power has been doing. Also bear in mind they have BILLIONS available to play at this table, not to mention a very deep field of academic and industrial talent and experience.

Done right, this technology has the potential to be Rotax power/weight ratio (something Lyc and Conti can only dream about).
======================================

Just about every 2 Stroke Engine Company 32+ at one time made an opposed Engine in the late 60's for Snowmobiles and only lasted about 3-5 years. VW, Corvair, BMW, etc, made opposed Engines, most aren't around today. Even many of the Certified opposed Airplane Engines aren't around today. Most (2) Seat Aircraft need 80+ hp.
 

Niels

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Counterrotating cancels torque reaction and make less prop noise.
A mean effective pressure of 4 to 5 bar will only need little turbo and cold inlet crankcase in series.
Exhaust piston can then be oil cooled if needed.
Achates can make more usefull engines using the twin AC generators method but it is a free country and not my money.
 
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n3puppy

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======================================
Just about every 2 Stroke Engine Company 32+ at one time made an opposed Engine in the late 60's for Snowmobiles and only lasted about 3-5 years. VW, Corvair, BMW, etc, made opposed Engines
There was never an OPOC (opposed piston opposed cylinder) snowmobile engine of the type being discussed here. Neither were VW's, Corvairs, or BMWs.
 

PMD

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======================================

Just about every 2 Stroke Engine Company 32+ at one time made an opposed Engine in the late 60's for Snowmobiles and only lasted about 3-5 years. VW, Corvair, BMW, etc, made opposed Engines, most aren't around today. Even many of the Certified opposed Airplane Engines aren't around today. Most (2) Seat Aircraft need 80+ hp.
You are confusing opposed cylinders with opposed PISTONS. OPOC engines have only one cylinder for each opposed pair of pistons with a crankshaft at each end. Being mostly 2 stroke cycle, there haven't been many around for emissions reasons for some time (the Commer TS3 being the last in a production road vehicle I can think of). While they have two crankshafts, they have no cylinder head nor valve gear and save a lot of weight, complexity, cost and efficiency by being such a simple design. They are also "uniflow" engines in that inlet is on one side and mass of combustion gasses keeps moving the same way to exhaust on the other side.

Here is a good video giving you a quick summary:
 
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PMD

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Problem is the propellers.We can either separate them so far that they do not intefere but it takes mass space etc.When a propeller blade goes into the common zone as shown on picture it will be unloaded that is try to accelerat more than sister prop that has all three blades doing full work.
Your propeller layout would be a disaster on a tractor installation, as the fuselage will be right behind a significant portion of the prop wake. Given very long driveshafts, though, it could be a really good way to do a pusher configuration as it would allow for shorter landing gear legs.
 
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