The more things change... Powerplant Developments UK

Group,
Another entry on the opposed piston diesel front. With claims of "new" and "revolutionary" Powerplant Developments of merry olde UK has reinvented the opposed piston diesel. I love this style engine, it's one of the most efficient configurations. The idea isn't new though. They claim 100 HP at a weight of 166 pounds, or 11.9 stone. Not too bad. The guys at DAIR might be a bit upset about the "new" claims. PPD uses a 3 cylinder (6 piston) layout. All complaints about their new and improved claims aside, the engine does bare watching.
Bill Jepson

Lighter

Rotary10-RV said:

Group,
Another entry on the opposed piston diesel front. With claims of "new" and "revolutionary" Powerplant Developments of merry olde UK has reinvented the opposed piston diesel. I love this style engine, it's one of the most efficient configurations. The idea isn't new though. They claim 100 HP at a weight of 166 pounds, or 11.9 stone. Not too bad. The guys at DAIR might be a bit upset about the "new" claims. PPD uses a 3 cylinder (6 piston) layout. All complaints about their new and improved claims aside, the engine does bare watching.
Bill Jepson

Click to expand...

How do they get lighter with two crankshafts and the associated stuff to connect them together?

gil A

me too

az_gila said:

How do they get lighter with two crankshafts and the associated stuff to connect them together?

gil A

Click to expand...

I've often wondered that myself. I suppose that the loss of two cylinder heads and the gain of a crankshaft has worked in their favor.

It seem like it would be a wash at best.

-mike

(august 31st, unemployed!)

mlw450802 said:

I've often wondered that myself. I suppose that the loss of two cylinder heads and the gain of a crankshaft has worked in their favor.

It seem like it would be a wash at best.

-mike

(august 31st, unemployed!)

Click to expand...

Don't forget this is a 2-CYCLE diesel. No cams, no valves, no cam drive. If they use 3 gears to tie the cranks together taking the drive from the center gear it can be very light. The removal of the valve train and cylinder heads makes a big difference. For a point of reference, Renault's F1 V-10 started the trend of F1 engines using AIR SPRINGS on the valve train. Two advantages were gained, first: the air springs never fatigued, no breakage. (Didn't you ever wonder how they were reliably getting 18K RPMs in the newest cars without brakage?) More important to this discussion though was the fact that replacing the 40 valve springs of the V-10 with air springs saved almost 8 POUNDS! Remember these guys were spending thousands of dollars to lighten the car by ounces. Talk about a win-win. No fatigue failures, AND 8 pounds lighter! Getting back to the opposed diesel, No valves, no cylinder heads, no valve gear, and 3 cylinders serving the swept area of 6 pistons. Yes this engine has the potential of being MUCH lighter even with the 2 cranks, one of which they would need anyway. If you think about it they are only adding the weight of 2 pistons and rods etc... Because you would need at least a 4 cylinder conventional engine to make the same power from a standard poppet valve engine. Like the the Rotax 912.
Bill Jepson

Do you have a link?

I'd like to look at this "new" engine. Do you know if they have a website?

Thanks

The key innovation (i.e. borrowing the 1930's design) is that it's a two-stroke engine. This reduces weight be eliminating cam shafts and valves, and doubling the number of power strokes per revolution.

The problem with this design is coupling the power between the two crankshafts. The gearing may be the weak point in the design. The 1930's engineers minimized some of these issues by driving the prop from one crankshaft and the accessories from the other. That way the gearing was coupling less load... but does not seem like a robust solution.

The engine is not truly dynamically balanced, because the opposing pistons are offset in timing in order to allow efficient intake and exhaust 'strokes'. That will require some propeller vibration testing.

Ignoring the spark plug in the following, here it is:

Animation.

fmarino1976 said:

I'd like to look at this "new" engine. Do you know if they have a website?

Thanks

Click to expand...

It is easy to find pictures of the engine, just search "Powerplant Developments" include the caps. I haven't found the website yet. In the past they timed the cranks as mentioned in another post which meant that the "trailing" crank delivered nearly 80% of the power. don't know if they are doing that.
Bill Jepson

vlittle said:

The key innovation (i.e. borrowing the 1930's design) is that it's a two-stroke engine. This reduces weight be eliminating cam shafts and valves, and doubling the number of power strokes per revolution.

The problem with this design is coupling the power between the two crankshafts. The gearing may be the weak point in the design. The 1930's engineers minimized some of these issues by driving the prop from one crankshaft and the accessories from the other. That way the gearing was coupling less load... but does not seem like a robust solution.

The engine is not truly dynamically balanced, because the opposing pistons are offset in timing in order to allow efficient intake and exhaust 'strokes'. That will require some propeller vibration testing.

Ignoring the spark plug in the following, here it is:

Animation.

Click to expand...

Same principle as a Fairbanks Morse diesel........
http://www.sdrm.org/roster/diesel/fm/index.html

FDNY used an engine with similar technology in their "Super Pumper Complex"

If I recall correctly, 18 cylinders, three crankshafts in a triangle setup.

Engine originally from a locomotive.

Deltic locomotives

Mike S said:

FDNY used an engine with similar technology in their "Super Pumper Complex"

If I recall correctly, 18 cylinders, three crankshafts in a triangle setup.

Engine originally from a locomotive.

Click to expand...

Mike.... that probably would be the English Deltic Locomotive used in the 60's and 70's

http://www.thedps.co.uk/staticpages/index.php?page=locos

...but the engine was originally developed by Napier in Manchester, England for fast navy boats....

Nice BBC history of the engine here...

http://www.bbc.co.uk/dna/h2g2/A11815175

gil in Tucson

OK... I admit to being a trainspotter in my youth, and remember the Deltics coming out... but trainspotting soon became aeroplane spotting at Speke Airport (now John Lennon International... ...).... and we all know where that can lead to...

Right

Gil, you hit it on the nose.

Quote from article about the pump module--"Powering this pump was an 18 cylinder, twin turbo Napier-Deltic T18-37C locomotive diesel."

I did a bit of quick searching, couldnt find any photos. I think the hyphenated name must have confused Google.

Memory....

Mike S said:

Gil, you hit it on the nose.

Quote from article about the pump module--"Powering this pump was an 18 cylinder, twin turbo Napier-Deltic T18-37C locomotive diesel."
.....

Click to expand...

So the memory isn't always the first thing to go.....

gil A

If they (PPD) succeed in certifying this Powerplant (to FAR 33) and gain enough positive field experience with competitive pricing/support, then ROTAX need to be worried, especially in Europe where the latter is very popular. 2 strokes diesel might be OK for the 100 HPish segment but 4 strokes direct drive diesel need to be considered for the 200-500 HP range...decent and proven technology that delivers lightweight/performance/reliability is now on the rise and that is much better than the ones used by the TAE and SMA or, like engines.

Gemini 100

These folks were at OSH with the 100 HP engine. They are working on a 360HP version and a 200HP version. Nothing flying yet though...
Here's the link: http://ppdgemini.com/

JetA4GA said:

If they (PPD) succeed in certifying this Powerplant (to FAR 33) and gain enough positive field experience with competitive pricing/support, then ROTAX need to be worried, especially in Europe where the latter is very popular. 2 strokes diesel might be OK for the 100 HPish segment but 4 strokes direct drive diesel need to be considered for the 200-500 HP range...decent and proven technology that delivers lightweight/performance/reliability is now on the rise and that is much better than the ones used by the TAE and SMA or, like engines.

Click to expand...

Don't see why this idea wouldn't scale to 200hp. Bigger pistons, more cylinders, whatever.

DeltaHawk is also 2-stroke, and is reportedly nearing certification. Theirs IS direct drive. The 2-stroke has an advantage in that it acts as if it has more pistons, with each "power stroke" providing less of a jolt than an equivalent 4-stroke. The result should be smoother operation.

Not to rain on the parade, but the hard part for the new guys (besides meeting the claims and longevity) will be to be able to produce in numbers at a cost less than the current offerings and with proper, widespread tech support. This is very difficult to do in a short period of time. Rotax has a pretty massive network worldwide with good training support and documentation.

If we look at how long it took Jabiru to get to where it is now and how poorly Wilksch, SMA, Deltahawk and Thielert have done after a number of years in the market, you'll realize that this is a hard nut to crack.

I wish them well but believe that any certified engine will be massively expensive and massively expensive to certify. All comers better have big financing behind them. I think it is a huge mistake business wise to concentrate initially on certifying new engines where there is a huge experimental market worldwide for manufacturers to recover initial investments on and refine their designs in actual use before proceeding to certification.

Direct Drive

Guys, This engine is direct drive to the propeller. The only gearing involved is 1:1 to gear and time the two crankshafts together. They don't need a gear reduction for RPM. I really like this style of engine it has many advantages. The super long effective stroke and good cylinder filling are both great for getting efficiency up. The Fairbanks-Morse engine was mentioned along with the Napier Deltic, and both of these engines were considered very efficient in their time. Modern materials applied to the same basic design should really produce a winner. Making it beyond the prototype stage is the tough part, as Ross mentioned. If you really wanted to make a stir it would be a great idea to develop in secret and be ready to produce when you release the engine to the public. I think people would nearly fall over backwards if when asked, "When will engines be available?", your answer was, "As soon as your check clears!"
Bill Jepson

Their website is at www.ppdgemini.com. It came from a podcast on AvWeb.com.

Plus: Full rated hp to 5kft, compact, and designed for aircraft. Negative: no torsional damper. Interesting concept, but I want to see more proven field useage. Could be a winner. Hope it is.

Joe

I agree with ROTARY10-RV, the gearing is a non-issue with this design. This is due to no small amount of existing analysis on gear design and materials that can be referenced to easily design a bulletproof gear train.

I don't know why so many people cringe when they hear the word "gears". We all use them everyday in our cars, and I've seen the gears from 50,000 lb thrust jet engines that were surprisingly small. If designed and setup correctly, gears are great!

gear ratio

The rep at OSH told me that on the Gemini 100 engine, the cranks rotate at 4000 rpm and the prop at 2500 rpm for a 1.6:1 ratio.

flytoboat said:

The rep at OSH told me that on the Gemini 100 engine, the cranks rotate at 4000 rpm and the prop at 2500 rpm for a 1.6:1 ratio.

Click to expand...

OK, I was refering to the crank gears, but this is still a very simple reduction. I notice from their line drawings that it allows a slightly higher thrust line which can be very helpfull in many tight cowlings. The 4000 RPM max won't cause any pitch line speed issues at least.
Bill Jepson
PS I'll bet their larger engine will be closer to unity on ratio.WRJ.

Thanks to you all on your feedback. Here my 2 cents on those based on experience with the design and integration with known Aero Diesel Engines brands:

- Personally no issues with 2, 4 strokes and turboshaft engines; Each has its Pros and Cons, it is just a matter of which Pros you need for your application and, what Cons you are ready to cope with. The PPD 2 stroke 100 HP engine is at about 0.75 Kg/HP and an SFC of around 0.40 lb/HP/hr on a narrow power range around cruise power. What I was saying is that the technolgy exists and is proven with direct drive 4 strokes diesel at 0.75 Kg/HP but with an SFC of 0.32 lb/HP/hr (20% less) over essentially the whole power range from idle to T/O power. However, it is more suited for 150 HP up to about say 600 HP making the PPD 100 HP engine more adapted for the smaller a/c (but not excluding it from the higher power outputs) due to its simplicity, engine-aircraft cost ratio and, lower usage applications. The 4 stroke aero diesel engines are more suited for the higher value a/c engaged in high usage (commercial, utility applications) making them good turbine competitors since the latter has a near twice SFC and higher initial acquisition and maintenance costs (reason for the ball parked 600 HP upper limit).

- Totally concurr with the remarks about a good support network for any newcommer...actually that is the challenge (the latest aero diesel "casualty" unfortunately lacked in the understanding of that concept). Unfortunately worldwide those sponserors of Aero Diesel engines that have a solid support network, deep pockets and the true will of promoting Aero Diesel engines (indeed the current AVGAS engine majors are potentially confronted with canibalism if they promote aero diesel engines) can be counted on the fingers of one hand that has been releived of a few (read plural with a capital "S") of them.

- The problem with gears is the cyclic nature of the torque signature of a recip engine where as with a turboprop engine it is for all intents purposes a constant. For the same number of pulses per rev diesels have the positive and negative peaks at essentially twice what they are with spark ignition engines. Car gearboxes are indeed reliable but are subjected to substantially much smaller torque densities and peak torque extremes than in aero applications. Car gearboxes are also not subjected to the gyroscopic effects of the propeller by virtue of their design. Though gearboxes could be better designed and beefed up (read mass), personally by experience I would rather trade the mass of a gearbox to the mass of additional pistons (comonality of parts) and have an engine with a lower peak torque signature due to the increased pulses per rev and a resulting lower volumetric power density (i.e. reliability).

JetA4GA said:

Thanks to you all on your feedback. Here my 2 cents on those based on experience with the design and integration with known Aero Diesel Engines brands:

<snip>

- The problem with gears is the cyclic nature of the torque signature of a recip engine where as with a turboprop engine it is for all intents purposes a constant. For the same number of pulses per rev diesels have the positive and negative peaks at essentially twice what they are with spark ignition engines. Car gearboxes are indeed reliable but are subjected to substantially much smaller torque densities and peak torque extremes than in aero applications. Car gearboxes are also not subjected to the gyroscopic effects of the propeller by virtue of their design. Though gearboxes could be better designed and beefed up (read mass), personally by experience I would rather trade the mass of a gearbox to the mass of additional pistons (comonality of parts) and have an engine with a lower peak torque signature due to the increased pulses per rev and a resulting lower volumetric power density (i.e. reliability).

Click to expand...

The thing here is I wonder if you are familar with this engine. All the cyclic and torque peak items are true, but easily designed for if you know your engines characteristics. This engine has 6 pistons and rods already, that despite having only 3 cylinders. For parts commonality they did use 2 crankshafts! The opposed piston diesel is considerably different than all the auto based and other aircraft design diesels. There are at least 2 manufacturers building this style engine now specifically for aircraft. DAIR, building a 4 piston 2 cylinder and PPD building a 6 piston 3 cylinder. Both of these engines have a lot of potential. FWIW The DAIR engine has flown in a cub replica ultralight.
Bill Jepson

Yes, I am very familiar with them and actually really like them. Actually I would really be curious to install and Flight Test one.

All engine designs have their place and the borders are not well defined between them and, may vary with time, the state of technology and, environmental regulations.