1.2 TDI for Aircraft

tdihopeful

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I'm seeking information and advice for conversion of a 1.2 TDI to use in aircraft. I have contacted a seller in Germany that has used 1.2's for sale and was told they weigh around 190lbs. They are used in the Volkswagen Polo Mk5, SEAT Ibiza Mk5 Ecomotive, Skoda Fabia Mk2, Skoda Roomster a question is that I have seen conflicting information as to what the block is made. Wikipedia states aluminum though other sources say cast iron. At less than 200lbs if accurate that seems to me to indicate aluminum. I'd like to learn what TDI engines are available with an aluminum block and clear that up as well as information related to ecu tuning for performance as well as to remove unnecessary automobile parameters such as limp mode and (limp mode could be dangerous in an aircraft) I would also appreciate estimated possible H.P. that is possible while maintaining strong reliability.

This is likely to be an ongoing thread and I'm thankful for you're contributions. Also if there is a more appropriate place to post this please let me know.
 

solarboy

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The 1.4 TDI is essentially the same but lighter and more powerful and usually remapped to around 100bhp. You should be able to get 75% the power of a 1.9 PD as they are basically the same engine with one less cylinder and a balance shaft.
 

tdihopeful

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I thought the 1.4 is a 4 cylinder. And as much as I looked back searching for aluminum block codes and such nowhere on Wikipedia do I see any references to an aluminum block in engine specifications. It seems to me that there are many codes and specifically in regards to variations in engines developed through VW industrial and marine. 4 cylinder would be fine and I'm thinking more and more I'd like to cast or cnc my own block for a PD engine. Maybe SLS or cast Titanium connecting rods and I know of a source for a newly developed aluminum alloy that is extremely strong and castable. In aircraft the Aircooled VW engines as used in the Beetle,Bus,Ghia are commonly built to Aerospace specifications and have basically all newly manufactured non-oem parts. Why not build a TDI with many new blueprinted parts utilizing modern manufacturing practices and top quality materials. Obviously 3d printing Inconel exhaust headers with integrated turbo was not economically viable at the time the first PD engines were produced but for my own very specialized useage why not?
 

Thunder Chicken

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Sounds like a fun project! What airframe are you looking to put this in? I’m not up on homebuilts, would you need to run a reduction gearbox? Do Subaru’s or Rotax’s?
Would you plan to run Diesel, or buy Jet A? I’d think you’d have to put additive running Jet fuel? Just some quick thoughts! Keep us updated!
 

Vince Waldon

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In aircraft the Aircooled VW engines as used in the Beetle,Bus,Ghia are commonly built <snip>
As I understand it the vast majority of small aircraft engines are air-cooled, for a host of reasons. One thing to think thru perhaps is the ramifications of using a water-cooled powerplant.

For example:

-will the cooling system function properly at all the angles and barametric pressures an airplane engine is subjected to?
-5 gallons of coolant weights 50 lbs, plus weight of the rad, fan, hoses, etc... is this a relevant consideration. Etc. :)
 

GTiTDi

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As I understand it the vast majority of small aircraft engines are air-cooled, for a host of reasons. One thing to think thru perhaps is the ramifications of using a water-cooled powerplant.

For example:

-will the cooling system function properly at all the angles and barametric pressures an airplane engine is subjected to?
-5 gallons of coolant weights 50 lbs, plus weight of the rad, fan, hoses, etc... is this a relevant consideration. Etc. :)
MANY aircraft engines have been water cooled over the years. Not many in general aviation, but it is not nearly as complicated as you think.
 

Pat Dolan

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To begin with, the largest volume aircraft engine manufacturer is Rotax, and all 4 cycle and the only current 2 cycle aircraft engines from Rotax are water cooled. The most common certified diesel aircraft engines are Thielert (now Continental) and Austro - and both are auto conversions of M-B 4 cylinder engines. What is true of ALL of the above engines is that they use gear reduction boxes. What is true of the automotive conversion engines is that they need REALLY BIG reduction gearboxes that are not simple to make (that is why Thielert is no longer Thielert) and very, VERY overweight. A 135 HP Conti diesel weighs in around 300 lbs. http://www.continental.aero/diesel/engines/cd135.aspx or about TWICE the weight of a Rotax 912 ULs (100 HP). So, the takeaway here is that if you had nearly unlimited resources you MIGHT be able to build a workable prop drive and keep the end product somewhere under 300 lbs., but there are no little airplanes out there that can haul a boat anchor around on their snout.

For the non-aviation types here, weight is such a big deal that adding 10 lbs. to the engine or propeller is a big deal. DOUBLING the weight would require complete re-engineering of the entire aircraft design.

The only current air cooled aircraft diesel SMA 305, direct drive, very expensive, also very heavy - way too large for any existing 2 place design. If you wait a while there WILL be a light weight, liquid cooled, Rotax weight and size 2 cycle aircraft diesel on the market (expect some time in 2021), There are actually a few companies working on this exact thing.

The 1.4 3 cylinder engine (that is the 3/4 of a 1.9) is a 6 valve direct injection engine while the 1.2 is a newer 12 valve common rail design. Both are cast iron block, aluminum head.
 
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Vince Waldon

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My point was not that the OP was talking about using a water-cooled engine in general, it was the hypothesis that since VW air-cooled engines were used in aviation why not use a water-cooled VW (post #3). As such there might be some considerations to think thru if adapting a cooling system designed for level flight, mostly constant barometric pressure, and few concerns from a weight perspective. Didn't use the word "complicated" once. :)
 

Pat Dolan

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My point was not that the OP was talking about using a water-cooled engine in general, it was the hypothesis that since VW air-cooled engines were used in aviation why not use a water-cooled VW (post #3). As such there might be some considerations to think thru if adapting a cooling system designed for level flight, mostly constant barometric pressure, and few concerns from a weight perspective. Didn't use the word "complicated" once. :)
And what I tried to explain is that there are more general aviation engines manufactured today in both spark ignition and compression ignition format that are water cooled than air cooled - it isn't difficult or unusual. Atmospheric pressure not a concern - the most efficient engines EVER installed in an airframe were water cooled diesels that started life working at 10,000 meters and completed development at 14,000+, all more than 77 years ago.

The thing that is going to limit the OP's intention is not water (and it would require less than a US gallon to cool, 5 gallons is what a semi needs to cool its ton of engine) it is complexity of the gear reduction (automotive engines have no thrust bearing so you can't direct drive the propeller directly from the crank - at least not for very long). Frank Thielert built formula 1 stuff but could not make a compact, light, reliable or durable re-drive to get needed RPM, thrust bearing and weight. While many people claim to have workable re-drives in the non-certified aircraft world, very, very few will actually ever manage to do this job. THAT is what will result in any attempt to do an auto conversion with a little TDI engine being unbelievably expensive proposition. Yes, there are successful auto conversions with re-drives, but none I am aware that use VW bolt pattern. Also important to realize that 3 and 4 cylinder 4 cycles and 1 and 2 cylinder 2 cycle diesels have extreme angular velocity variations (and rate of change of variation) that excite some...er...INTERESTING harmonics into propellers (especially aluminum ones). That means a one-off custom design. It's one of those things that if you are asking the question, you are not the right person to go down that very long, complex and expensive road. Now, all of that said, I believe there are already some TDIs flying in Europe, and the OP might be able to find hardware and engineering advice from someone who is already in the groove. BUT: automotive diesel conversions are heavy, heavy, HEAVY from a light homebuilt frame of reference.
 
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Pat Dolan

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I'm seeking information and advice for conversion of a 1.2 TDI to use in aircraft. I have contacted a seller in Germany that has used 1.2's for sale and was told they weigh around 190lbs.
Forgot to mention: since the current1.2 is a common rail engine, you will also need an ECU that will need to be reprogrammed radically to work at all. There ARE stand alone ECU options for CR engines, but they tend to be pretty expensive.

What MIGHT be a far better option is not the current common rail, but the legacy TDI engines going back to the "3 litre Lupo". That started with a 1.2 diesel that DID (or more to the point DOES) have an aluminum block casting. That is a PD engine using EDC15, so the original ECU can probably be made to run just fine without a car wrapped around it. BUT: this is still a 220 lb. engine (probably what the seller is claiming as 195) that makes 60 HP at best. You would be looking at a 300+ lb., 60HP engine with re-drive (PSRU) that could cost a fair bit to get together and flying. In other words: twice the weight for half the power of a Rotax 912.
 

nicklockard

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And what I tried to explain is that there are more general aviation engines manufactured today in both spark ignition and compression ignition format that are water cooled than air cooled - it isn't difficult or unusual. Atmospheric pressure not a concern - the most efficient engines EVER installed in an airframe were water cooled diesels that started life working at 10,000 meters and completed development at 14,000+, all more than 77 years ago.

The thing that is going to limit the OP's intention is not water (and it would require less than a US gallon to cool, 5 gallons is what a semi needs to cool its ton of engine) it is complexity of the gear reduction (automotive engines have no thrust bearing so you can't direct drive the propeller directly from the crank - at least not for very long). Frank Thielert built formula 1 stuff but could not make a compact, light, reliable or durable re-drive to get needed RPM, thrust bearing and weight. While many people claim to have workable re-drives in the non-certified aircraft world, very, very few will actually ever manage to do this job. THAT is what will result in any attempt to do an auto conversion with a little TDI engine being unbelievably expensive proposition. Yes, there are successful auto conversions with re-drives, but none I am aware that use VW bolt pattern. Also important to realize that 3 and 4 cylinder 4 cycles and 1 and 2 cylinder 2 cycle diesels have extreme angular velocity variations (and rate of change of variation) that excite some...er...INTERESTING harmonics into propellers (especially aluminum ones). That means a one-off custom design. It's one of those things that if you are asking the question, you are not the right person to go down that very long, complex and expensive road. Now, all of that said, I believe there are already some TDIs flying in Europe, and the OP might be able to find hardware and engineering advice from someone who is already in the groove. BUT: automotive diesel conversions are heavy, heavy, HEAVY from a light homebuilt frame of reference.

This^^ Listen to this. Also, see the struggles of Raptor Aircraft on youtube. He's converted an Audi Tdi to power a canard pusher aircraft, but has some real challenges. I had to unsubscribe from his channel--he's taking way too many shortcuts and depending on swags in place of proper engineering. His aircraft weighs about as much as a passenger sedan (3500 ish lbs)...barely able to fly. Ridiculously complicated cooling; supposedly wrong turbos selection. Not sure what he's doing for thrust bearing though.
 

tdihopeful

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This thread is developing nicely... To reply I'm going to do that from last comment first. Raptor: I've been following this project since at least near the beginning before most of the tooling had been produced. There are many people mostly in the Homebuilt Aircraft community that have been ridiculing Peter for his unconventional design but mostly for his choice of Engine and his seeming learning while he goes build process.

Many of these naysayers are opinionated without a true insight into specifics. One is aircraft weight. Raptor utilizes a newer fuselage design called lifting body. This design can contribute something like 30% lift over conventional fuselage designs. There are numerous factors, including projected calculation and known construction parameters that Peter likely factored into the Project Prototype.

I believe he is far more competent than people recognize. As for the recognized wisdom of not testing a new power plant with a new airframe either one or the other. I agree with the development philosophy of reducing variables for lessened risk in a rapid and less than thorough flight test regime. Though that is not to say doing other than that will not work!

Raptor to me looks relatively well though out and I congratulate Peter on the safe beginnings of flight testing and wish him continued success and safe flights through testing and for the future of Raptor with thanks for making bold steps forward in the field of Aerospace.

I will continue the reply to comments shortly
 

tdihopeful

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Ok to address the problem with torque reversal and associated harmonic vibration issues one is I would likely not be direct driving the propeller. If I did and as a practice even with an advanced drive design is to limit the time spent outside of particular RPM ranges.

This means no extended use of the engine at other than a low idle and rpm of 2,500-3,000 where the engine is smooth. Limiting the time the Propeller and drive is within ranges of say high idle to 1,000-1,500 reduces the stress on these components.

A dual mass flywheel may be utilized and from what I understand is what allows the Austro engines to perform sufficiently.

The particular drive and propeller design I'm planning is quite unconventional tough and while it is unlikely to be effected by low frequency harmonics it could experience issues with higher frequency vibration. The higher frequency vibrations and the design I have in mind while less likely to be affected if it is the likelihood is that the failure would lead to catastrophic and instantaneous shedding of Propeller blades. As such a regimented, thorough and extensive testing both static and flight should be planned for.
 

tdihopeful

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Here is a question that I'd like to hear comment on. What could be potential problems with lightening a TDI by an extreme margin?

My thinking is the engines heaviness would tend to dampen vibration and lightening the block would lessen dampening effect. What about rotating assemblies such as crankshaft and cam shaft?

Crankshaft would have obvious ramifications and would necessitate lightening of rods and pistons but camshaft other than maybe a harmonic interaction seems like it would be as simple as a swap (Titanium Cam)
 

tdihopeful

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I wonder why you say a 200lb engine then in the same post make a 300lb figure? Are you saying 200lb is what you think the bare block would weigh and with turbo, exhaust, radiator and coolant 300lb? The HP of around 70 stock could be reliably increased to twice that from what I understand and that would be with stock turbo. That would make the engine on par or better than many certified aircraft engines, far more fuel efficient and far less expensive.

Forgot to mention: since the current1.2 is a common rail engine, you will also need an ECU that will need to be reprogrammed radically to work at all. There ARE stand alone ECU options for CR engines, but they tend to be pretty expensive.

What MIGHT be a far better option is not the current common rail, but the legacy TDI engines going back to the "3 litre Lupo". That started with a 1.2 diesel that DID (or more to the point DOES) have an aluminum block casting. That is a PD engine using EDC15, so the original ECU can probably be made to run just fine without a car wrapped around it. BUT: this is still a 220 lb. engine (probably what the seller is claiming as 195) that makes 60 HP at best. You would be looking at a 300+ lb., 60HP engine with re-drive (PSRU) that could cost a fair bit to get together and flying. In other words: twice the weight for half the power of a Rotax 912.
 

Pat Dolan

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300 lb. with all accessories would be about right, but then you need a PSRU so add another bunch of weight thus why I mentioned 300 at best. The best way I can frame it is that if the F1 engineering guys who used first a custom 1.7 aluminum block and then a production 2.0 cast iron block (Thielert the former and both them and Austro the latter) can't come anywhere near a decent power/weight ratio with a workable redrive (both now work, but neither exactly bulletproof and a very long way from light) - what makes you think a little backyard engineering is going to find design solutions that haven't already been tried by people with a lot of experience and nearly unlimited budget? Don't want to discourage experimentation, just need to inject a solid dose of reality in expectations. A very high performance engine such as a 100HP 912 ULs starts off just over 130 lb. but with everything but a cowling is more like 195, so 2.0 lb/HP is a goal for an extremely well developed design. To expect an amateur design of a very non-optimum engine to come in much better than 4.0 lb/HP is unrealistic. IMHO even 5.0 would be nothing to be ashamed of.

Making a TDI a lot lighter could be done, but it would be a VERY expensive proposition with all kinds of reliability and durability risks. Now, bear in mind DIY aircraft have flown quite happily behind Model T Ford engines. Heck, even the V8-60 has flown with cast iron block and PSRU. (on edit) I should have mentioned that was actually a certified aircraft engine in the '30s - you can see one at Old Rhinebeck if you are interested Same power you are contemplating, but WELL over 500 lbs.! My advice is thus to get flying with the weight and cost that fits your budget and schedule and not to obsess about re-inventing what could become a very expensive and slow wheel.
 

Andyinchville1

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HI,

Maybe a little out of the box , but I read that in the old days when cars were mostly made of steel, some drag racers would dip parts in acid to reduce weight..... easier than machining large complex shaped parts.

Not sure how something like that would work engine wise since I'd imagine bearing tolerances , heat treated surfaces etc would be affected (not to mention other materials like aluminum etc) but I suppose custom bearings could be made and surfaces refinished as needed (at least a new block would not have to be cast or machined from scratch).

While not an engine BUT engine related and a way to save weight , how about using a lithium type battery .... Antigravity , braille , and others make batteries quite a bit lighter than lead acid batteries .... a few lbs here and here can add up... ( I was researching their batteries as a way to lighten the front end of my car but they lighten the wallet quite a bit also!).

Also, how about lightening other parts ? When I used to race RC cars, I reduced weight by using titanium hardware in place of steel and aluminum /and carbon fiber when possible.

Andrew
 

tdihopeful

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I'm not Anti-Rotax or anti certified aircraft engines. The thing is I'm talking homebuilt experimental. If I was to always use a certified engine and airframe then it wouldn't be experimental. The only service I would be doing to advance Aerospace technology would be nothing and outside of that the only service I would be offering would be maybe promoting a slightly better percentage reduction in risking my life. That small risk I'm willing to take. I actually will likely be as or more confident in what I do in this regard. Andy yeah exactly grams add up to ounces and ounces at up to pounds ultralight backpacking is where I heard that saying. Thanks for mentioning bolts. I hadn't even thought of them as a point of weight reduction. All those bolts add up for sure!
 

Pat Dolan

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HI,

Maybe a little out of the box , but I read that in the old days when cars were mostly made of steel, some drag racers would dip parts in acid to reduce weight..... easier than machining large complex shaped parts.

Not sure how something like that would work engine wise since I'd imagine bearing tolerances , heat treated surfaces etc would be affected (not to mention other materials like aluminum etc) but I suppose custom bearings could be made and surfaces refinished as needed (at least a new block would not have to be cast or machined from scratch).

While not an engine BUT engine related and a way to save weight , how about using a lithium type battery .... Antigravity , braille , and others make batteries quite a bit lighter than lead acid batteries .... a few lbs here and here can add up... ( I was researching their batteries as a way to lighten the front end of my car but they lighten the wallet quite a bit also!).

Also, how about lightening other parts ? When I used to race RC cars, I reduced weight by using titanium hardware in place of steel and aluminum /and carbon fiber when possible.

Andrew
The old school drag guys (that's drag RACERS, not...well, you know) used to acid dip their bodies, not their engines (won't even go there relative to my other "drag" comment). Steel will dissolve at a fairly predictable but very slow rate. I would not want to try that with cast iron.

There is actually a lithium (I think LiFe) battery that is certified for aircraft use. Pricey, though.

Titanium connecting rods are common, but as with aluminum they have a finite (and rather expensive) lifespan.

There are a million things you CAN do, but the most effective weight reduction technique is to simply eliminate the part. Sadly, to make crank RPM into propeller RPM and take end thrust you have to ADD a bunch of stuff.
 

Pat Dolan

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I'm not Anti-Rotax or anti certified aircraft engines. The thing is I'm talking homebuilt experimental. If I was to always use a certified engine and airframe then it wouldn't be experimental. The only service I would be doing to advance Aerospace technology would be nothing and outside of that the only service I would be offering would be maybe promoting a slightly better percentage reduction in risking my life. That small risk I'm willing to take. I actually will likely be as or more confident in what I do in this regard. Andy yeah exactly grams add up to ounces and ounces at up to pounds ultralight backpacking is where I heard that saying. Thanks for mentioning bolts. I hadn't even thought of them as a point of weight reduction. All those bolts add up for sure!
Well, I AM anti-Rotax - and anti-anything-else spark ignition. Have to cite them, though as they literally own the market for 80 and 100HP engines worldwide, and they make a fine engine and an even better gearbox. What I was trying to convey (having to post in short bursts as I am very tied up on one aircraft and one car engine project) is that the simplest way to get 2 lb./HP is to just buy a blowtax, but just be aware going into the 3 cyl TDI route you are not going to get to those weights. If people could fly 60 HP engines that weigh over 500 lbs. 80 + years ago, you just need to adjust your airframe design for the reality of 60 HP at 300 lbs. and get on with the engine work with realistic goals. Can't help but stress looking at what IS successful in the drive world, as dealing with the torsional inputs and resonance is a huge deal. If I were going down your road, I would probably start by making an adapter plate to use a Rotax box from their 80 HPl engine. There are a few other well proven boxes on the market for gear drive. I have built both timing and HTD drives (used to manufacture commercial airboats) and can warn you that they pass torque spikes along very effectively. Experimenting is great, but re-inventing the wheel is not really necessary.

Too bad nobody makes a smaller version of THE most efficient combustion engine ever to be installed in an airframe. A tiny 3 cylinder Junkers Jumo with modern HPCR would be the cat's ass!
 

nicklockard

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Cummins partnered with Achates Power on their Opposed Piston, Opposed Cylinder (OPOC) 2 stroke diesel successfully. They just validated a 14.3L main battle tank version. https://www.thedrive.com/news/35330...four-with-eight-pistons-no-valves-and-1000-hp This engine puts out 1000 hp @ 3900 lb -- which is 3.9 lb/hp. I imagine they could reduce accessory and block mass for an aerospace version. This is after all a combat version, so I'm sure it has tons of (absurdly heavy) redundancies built in.

I wouldn't be surprised if Achates Power is in talks with aerospace people to develop a version for aircraft, but it could be 10 years before you see a certified version for sale.

Edit: apologies if this is a diversion to your thread tdihopeful. To get back on track somewhat: in order to minimize harmful driveline harmonics, some off-the-wall thoughts of mine:

Explore the use of hydraulic drive with an accumulator, thus eliminating the need for a heavy flywheel or clutch. The accumulator absorbs the torque harmonic pulses, then feeds the energy at a smoothed output rate to the prop shaft. Further: explore the use of constant velocity, variable pitch prop along with this, if overall weight/performance goal can be achieved. Could it make it easier to engineer a thrust bearing too? Dunno, but maybe investigate. If this could all be made to work, you could run a smartfortwo 800cc CDI (Mercedes Benz OM660 engine code, 54hp variant from the third generation smartfortwo's--you could run it at it's horsepower peak during the runup to takeoff, building power reserve capacity into the hydraulic accumulator, then after you're airborne, you could throttle it back to its torque peak for max efficiency during cruise. You could manage the reserve power capacity that the hydraulic accumulator has manually by just observing pressure, to make sure you always have spare energy for doing emergency maneuvers, and for landing with some reserve power in case your engine fails.

PROS:

  • The weight that such a system would add would at least partially be offset by the weight lost from removal of flywheel and clutch.
  • Could make it easier to design a simplified, robust thrust bearing mount(?)
    • consider paying a professional aerospace engineer to do some finite element analysis of vibration, axial and radial loading, etcetera to pre-validate your designs, or just be ready for lots of trial & error.
  • Should solve all harmonics issues/concerns.
  • Benefits of a variable pitch system (& cons I suppose? I'm not up to speed on these)
  • Possible to get 15% power increase from OM660? This would get you really close to 3.0 lb/hp. And, if you size the hydraulic power system to be very well engineered, perhaps you could target a peak (short duration) power range of 100 (or your design target) hp or so, getting you closer to your power-to-wight goals--at least where it counts the most (take off & landing power)
CONS
  • $ to run FEA and vibration analysis. You COULD do this on your own through Onshape cad's simulation partners, but expect to spend $3000 for all the simulations to have confidence in them.
  • $ to fabricate and weld mounts for thrust bearing and hydraulic system.
  • Extra cad design time and longer design review cycle
  • $ and time to find a well-matched, off the shelf hydraulic drive with accumulator? Wouldn't want to design this myself--too long and steep a learning curve I bet.
  • Probably getting hard to track down an OM660 in 54hp variant
 
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Pat Dolan

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Achates has had a 2.7 litre, 270 HP 3 cylinder running for several years - but in once again uber-porky automotive trim. Superior Air Parts had a genuine aviation 100 HP 3 cylinder mockup they showed in 2015 at S&F and Osh, but their own internal problems and lack of in-house engineering capability has seen that one go nowhere. DieselAir HAD a nice two cylinder IIRC around 80 HP flying on dirigibles some time ago. But, as of today nobody is PUBLICLY declaring any opposed piston diesel aircraft engines. Achates started out aiming at low emissions and good efficiency - and the 2.7 knocks that ball right out of the park, but the auto trade is so confused and chickenshyte right now, they don't know if their rectum is punched or bored. Plus Lemke died last year, so not sure if they will get involved with any smaller engine projects (they are not a manufacturer and have no intent to be).

Back OT: we can;t forget the 3 cylinder Smart engine. 800cc but there are flying versions in Yurp at 80 HP,. Meant to ask of Hopeful: why were you (or where you?) planning on staying down at 65 HP? Either of these engines can do much more quite reliably.
 
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