84 replies to this topic

[mariner]

I know the deltic diesel has been discused here before but this article from the enginelabs website has a lot of info. I didnt know of e.g the  firing order tuning for smoothness and the use of Deltic  by the US in Vietnam

 

 

http://www.enginelab...c-diesel-works/

 

Having seen th Deltics at Kings Cross station in London I always loved the smoky starts and the great noise.

[bigleagueslider]

Thanks for link. Napier's engineers were definitely gluttons for punishment when it came to their choice of engine designs - the Saber, the Nomad, the Deltic. In fact, Napier actually built and tested a 24 cylinder, 4 crankshaft, compound "Deltic Diamond" engine. But the British government quickly thought better of it and cut off funding.

 

 

Here's a good website dedicated to the US PTF class boats used in Vietnam, including lots of technical info on their Deltic engines.

 

If you have an interest in OP engines like the Deltic then this 563 page book is a must-read.

[manolis]

Hello.

The main advantage of the Deltic as compared to the conventional Opposed Piston is its lightweight (and the decrease of the mechanical friction and cost).

While the conventional Opposed Piston needs two crankshafts per pair of opposed pistons, the Deltic needs only three crankshafts for the three pairs of opposed pistons, i.e. only one crankshaft per pair of opposed pistons.

A side effect of the Deltic is the phase difference between the intake and exhaust crankshafts; it is necessarily 20 degrees, which is almost double than the "optimum".

The "Deltic diamond" has four crankshafts for four pairs of opposed pistons, i.e. a crankshaft per pair of opposed pistons, i.e. the same as the "triangular Deltic", i.e. it is neither more lightweight, nor it further reduces the mechanical friction and cost. However, the phase difference between the intake and exhaust crankshafts can be optimized.


In comparison to the Deltics, the Radial Bristol Centaurus (or Hercules) engine by sharing a small / lightweight crankshaft among 18 (or 14) cylinders becomes way more lightweight; however it operate at four strokes which is bad for the "power to weight" ratio.


The PatATi Cross-Radial 2-stroke engine:



combines advantages from both schools, like:

it needs only one crankpin per four pistons (i.e. half than in the Deltics),
it has optimized built-in asymmetric transfer,
it has better balance than the conventional Radials and true "internal symmetry".


Quote from http://www.pattakon....ttakonPatAT.htm :

“The above even-firing Cross-Radial PatATi is as vibration free as the best V8, it has firing intervals equal to those of a V8 four-stroke, it has four-stroke lubrication (plain bearings, forced / splashed lubrication in the crankcase, oil scraper rings), it can utilize a central scavenging pump (a turbocharger, for instance), etc.”

“In comparison to the convetional Radial engine, the Cross-Radial with the four cylinders and with the forked connecting rods is a true "vibration free" engine (better balanced than the "master-slave-rods" Radial regardless of the number of cylinders of the later), it is also a true "symmetrical" engine: all the four cylinders run under the same conditions: same piston stroke, same piston motion profile, same connecting rod leaning (thrust loads), etc.”



Advantages of the Deltic: the "through scavenging" and the absence of cylinder heads.

As a turbocharged Diesel (the energy of the exhaust gas is used for the scavenging) the PatATi seems as having the qualifications for extreme "power to weight" ratio and, at the same time, for top fuel efficiency (small airplanes, helicopters, paragliding etc).

Thanks
Manolis Pattakos

Edited by manolis, 17 June 2015 - 04:09.

[bigleagueslider]

"In comparison to the Deltics, the Radial Bristol Centaurus (or Hercules) engine by sharing a small / lightweight crankshaft among 18 (or 14) cylinders becomes way more lightweight; however it operate at four strokes which is bad for the "power to weight" ratio."

 

Here's a picture of the Bristol Hercules front end. Are you seriously claiming that this mechanical nightmare is more efficient than other similar engines of that period?

 

[mariner]

Backlash, what backlash?

[gruntguru]

 Are you seriously claiming that this mechanical nightmare is more efficient than other similar engines of that period?

 

Yes - and no. Depends what type of efficiency you are talking about.

[manolis]

Hello Bigleagueslider.

You write:
“Here's a picture of the Bristol Hercules front end. Are you seriously claiming that this mechanical nightmare is more efficient than other similar engines of that period?”


According the Internet:

“The Bristol Centaurus has 18 cylinders in two rows, and is a sleeve-valved radial air-cooled engine. The first version produced 2,000 bhp, and the most powerful variant produced 3,200 bhp. It was the ultimate radial engine, and was developed primarily for heavy bomber and transport aircraft. Over 8,000 were produced. The Centaurus radial engine made the Sea Fury one of the fastest piston-engine aircraft ever manufactured.”

and

“There were about 75 thousand Hercules engines manufactured.”


Through the gearwheels of the “mechanical nightmare”, as you call it, they were driven the sleeve valves.
The breathing efficiency was top (comparable only with radials having four poppet-valves per cylinder).
If besides the picture with the gearwheels of the Briston Centaurus you put the required poppet valves (4*18=72), restoring springs, rocker arms, pushrods, cylinder heads, camshafts etc) of a conventional 18-cylinder Radial of the same era, the "mechanical nightmare" turns to a simple, lightweight and reliable solution (desmodromic?).


Either with sleeve valves, or with poppet valves, the conventional Radial (a master connecting rod with several slave connecting rods per row of cylinders) has a substantial internal asymmetry: a 10% piston stroke difference between the cylinders of the same row (same crankpin) is "reasonable" as shown in the following animation:



Worse even, the piston motion profile (how quickly the piston approaches the TDC and how quickly it leaves, after the combustion, the TDC) depends on the position of the specific cylinder relative to the “master” cylinder of the row.


Compare the previous with the simplicity, the perfect "internal" symmetry and the better vibration-free quality of the Radial Cross PatATi shown at post #3. Isn't this architecture more lightweight than the Deltic?

Thanks
Manolis Pattakos

[bigleagueslider]

"According the Internet:  “The Bristol Centaurus has 18 cylinders in two rows, and is a sleeve-valved radial air-cooled engine. The first version produced 2,000 bhp, and the most powerful variant produced 3,200 bhp. It was the ultimate radial engine, and was developed primarily for heavy bomber and transport aircraft. Over 8,000 were produced. The Centaurus radial engine made the Sea Fury one of the fastest piston-engine aircraft ever manufactured.”  and  “There were about 75 thousand Hercules engines manufactured.”

 

The Pratt & Whitney R-2800 was also an 18 cylinder, two row radial, air-cooled engine. But there were over 125,000 of these engines produced, and many are still flying today.

 

I agree with your point that radial engines using a master/slave conrod arrangement have assymetric piston kinematics. But the designers of these radial engines understood this fact, and adjusted the valve timings, ignition timings, and fuel mixtures to each cylinder to compensate for it.

[Wuzak]

The Centaurus differed from teh Hercules in having the sleeve drive for the back cylinders at the back, whereas all 14 sleeve drives for the Hercules were at the front.

 

Regarding the connecting rod arrangement, imagine hwo much longer and flimsy the crankshaft would be if it used Manolis' connecting rod system for 7 or 9 cylinders?

 

The Rolls-Royce Vulture and Pennine used the master and slave rod arrangement. So much trouble was had with the system on the Vulture that pairs Fork and Blade rods, side by side, were considered for future versions before the program was axed. The earlier Rolls-Royce experimental X-16 Eagle XVI also had pairs of Fork and Blade rods side by side, meaning that the top pair of cylinders were offset to the bottom pair.

 

The Allison X-3420 also had side by side Fork and Blade rods.

 

I think, also, that the Daimler-Benz DB604 X-24 had the master and slave rod system.

 

The original 1929 Rolls-Royce R, based on the Buzzard, had fork and blade rods. In 1931, with increased boost, the big end bearings were failing, so they were replaced with a master and slave rod arrangment.

[manolis]

Hello Wuzak

You write:
“Regarding the connecting rod arrangement, imagine hwo much longer and flimsy the crankshaft would be if it used Manolis' connecting rod system for 7 or 9 cylinders?”

The Cross Radial PatATi is a two-stroke engine.

With four cylinders per row it is equivalent, as regards the number of combustions per crank rotation and the smoothness of the delivered torque, with a conventional 4-stroke radial having 8 cylinders per row (the Hercules has 7 cylinders per row, the Centaurus has 9 cylinders per row).

As regards the inertia smoothness (vibration-free-quality), a single row 4-cylinder PatATi is better than a single row 7 (or 9) cylinders Conventional Radial.

Actually, a single row 4-cylinder PatATi (the cross radial engine shown in the animation) is more vibration free than the 14-cylinders and 18-cylinders double-row conventional master-rod Radials (wherein, in some cases, there were used additional counterbalancing shafts to reduce vibrations).

If you want more cylinders in the PatATi radial, you can add another row of 4-cylinders. In case of air-cooling, the two rows should be arranged at 45 degrees from each other:



As shows the animation (post #3), the crankpin of the Cross Radial PatATi (4-cylinders per row) is not long.
Besides, the symmetrical arrangement of the forked connecting rods makes the loading of the crankpin / crankshaft better.
If you look carefully at the second animation of the Cross Radial PatATi (that with the moving parts orbiting in the space) you can see that the heavily loaded side of the big end of each connecting rod has a larger area than the opposite (and slightly loaded) side of the big end.
The yellow part, which is secured to the crankpin, is the common bearing for all four connecting rods.


From another view-point:
With only three cylinders per row a radial engine (either 4-stroke or 2-stroke, conventional or PatATi) has strong inertia vibrations.
With four cylinders per row, the two-stroke Cross Radial PatATi is as vibration free as the best V-8 four stroke engines. It is also even firing (in comparison, a four cylinder 4-stroke radial cannot be even firing).
With only four cylinders per row, the length of the common crankpin of the PatATi is acceptably short.
So, is there any reason to go to Radial PatATi’s having more than 4 cylinders per row?


The four-stroke lubrication of the crankcase / lower-cylinder-liners of the Cross- Radial PatATi is a requirement if it is to run reliably as a heavily supercharged (by its turbocharger) Direct Injection Diesel.

Combining top power-to-weight ratio with top fuel efficiency, simplicity and reliability seems as the “holy grail” for airplane / helicopter engines.

So, please take another look and compare a turbocharged Direct Injection Diesel Cross Radial PatATi (like that of the animation) with the state-of-the-art modern reciprocating piston airplane engines.

Thanks
Manolis Pattakos

Edited by manolis, 21 June 2015 - 06:41.

[bigleagueslider]

I would agree with Wuzak's point about the axial length required for the crank conrod journal with this concept. The fork/blade conrod designs used by V-type engines like the R-R Merlin only involved two conrods per journal, while the design proposed above involves twice as many. This would require a crankpin journal at least twice as wide, which would present torsional stiffness and journal bearing edge loading issues due to pin bending.

 

Then there is the issue of air-cooling a multi-row radial engine. It was a big challenge to air-cool high-performance multi-row 4-stroke radial engines. The greater thermal loads of a 2-stroke would present a far greater design challenge.

[gruntguru]

The fork/blade conrod designs used by V-type engines like the R-R Merlin only involved two conrods per journal, while the design proposed above involves twice as many. This would require a crankpin journal at least twice as wide, which would present torsional stiffness and journal bearing edge loading issues due to pin bending.

 

Then there is the issue of air-cooling a multi-row radial engine. It was a big challenge to air-cool high-performance multi-row 4-stroke radial engines. The greater thermal loads of a 2-stroke would present a far greater design challenge.

 

Not sure why you would think that. Twice as many conrods, twice the width would be a maximum IMO. One criterion dictating the width of a crankpin is bearing area required to support the load. The Merlin bearing probably has enough area to support twice as many cylinders so any increase would be mainly to accomodate the additional rods. Don't forget this is a two stroke and Manolis has already stated that his crankpin design has the bearing area biased towards the top of each rod. I am thinking 50% increase. Can't see any issue with pin bending as the design allows absolute symmetry of pin loading.

 

The high performance 4 stroke radials were all supercharged. The NA 2 stroke design in an aircraft application (high air velocity) would have to be easier to cool than a two stroke chain saw or motorcycle.

[manolis]

Hello Bigleagueslider.

You write:
“Torsional stiffness and journal bearing edge loading issues due to pin bending”

The simplest answer is a larger crankpin diameter.

On the other hand, take a look at the crankshaft structure of the double-row Hercules Bristol Radial engine wherein there is no central crankshaft bearing:



How the left end of the crankshaft takes the forces acting on the right crankpin?
Don’t they create heavier – as compared to the PatAT Cross Radial – bending loads on the left crankpin?

CORRECTION:
There is a central bearing in the Hercules Bristol.
The longer crankpin of the Cross Radial PatAT can be compared with a conventional straight four having only three crankshaft main bearings.
END OF CORRECTION


You also write:
“Then there is the issue of air-cooling a multi-row radial engine. It was a big challenge to air-cool high-performance multi-row 4-stroke radial engines. The greater thermal loads of a 2-stroke would present a far greater design challenge”

Take a look at the drawing of the double row Cross Radial PatAT (post #10) and compare it to the Centaurus multi-row Radial:

.

The cylinders of the back row of the Centaurus Radial receive the hot air from the front row (each pair of neighboring front cylinders is a 40 degrees Vee engine; the back-row cylinder arranged in the bisecting plane of the above Vee has a small “window” through which fresh air comes for its cooling).

In comparison, the cylinders in the back row of a Cross Radial PatAT see as much cool air as the cylinders in the front row (each pair of neighboring front cylinders forms a 90 degrees Vee engine; the back-row cylinder arranged in the bisecting plane of this Vee has a wide window through which cool air comes).

That is, the cooling of the back row of cylinders of the Cross Radial PatAT is as good as the cooling of the front row.

By the way, as a Direct Injection Diesel the Cross Radial PatAT has higher fuel efficiency and needs less cooling for the same power output.

Thanks
Manolis Pattakos

Edited by manolis, 22 June 2015 - 06:25.

[bigleagueslider]

Consider the six-row radial Rolls-Royce Pennine engine that has a 4x90deg cylinder spacing in each row, similar to your concept. You'll note that R-R opted to use a master/slave conrod design rather than your proposed fork/blade conrod arrangement, which they were already using on the Merlin.

 

As for the Bristol Hercules two-row radial crankshaft, if you look at the cross section below you'll note that there is a roller main bearing used between the front and rear crank throws. Use of roller main bearings and multi-piece cranks, like the Hercules engine, was common practice. The P&W R2800 used this same design initially, but soon abandoned it in favor of a more reliable single piece crankshaft and split master rods.

 

 

Lastly, the arrangement of cooling fins shown on the cylinder heads in your post #10 appears to be less than optimum for an airflow in the axial direction.

[Wuzak]

Note that the Pennine has all cylinders in a row. Cooling was by force guiding air from inside the intake vees (top and bottom) past the cylinders and exiting the exhaust vees to the sides.

 

Guiding of the air was very important for multi-row radials as well.

 

The Armstrong Siddeley Deerhound had its cylinders in a line front to back. It had cooling issues until they opted for revese flow (back to front cooling).

 

 

The R-2800 and R-4360 certainly used baffles to guide the air through the cylinders, and so that the hot air from one row wasn't trying to cool th enext.

 

Edited by Wuzak, 23 June 2015 - 08:15.

[Wuzak]

As for the Bristol Hercules two-row radial crankshaft, if you look at the cross section below you'll note that there is a roller main bearing used between the front and rear crank throws. Use of roller main bearings and multi-piece cranks, like the Hercules engine, was common practice. The P&W R2800 used this same design initially, but soon abandoned it in favor of a more reliable single piece crankshaft and split master rods.

 

The R-2800 stayed with the built-up crank and single piece master rod throughout its life.

 

The R-4360 was based on the R-2800 cylinder, but had to go to a single piece (4 throw) crankshaft and split main bearing master rods.

 

While the R-4360 cylinder started out the same as the R-2800's it soon evolved so that it was a crossflow design, rather than both intake and exhaust pointing rearwards. This was done to ease making manifolds that worked.

[manolis]

Hello Bigleagueslider

See the length of the crankpin of the R-R Pennine in the drawing.
It is as big as the cylinder bore.
And it transfers the combustion torque from some three cylinders (there is one combustion per 30 crank degrees): if a piston is at 20deg after the TDC, there is a second piston at 50deg after TDC and a third piston at 80deg after the TDC, all three at the expansion stroke.

Besides the heavier combustion loads, the crankpin is additionally loaded by heavy inertia forces: Take the one row; with the one piston at the “overlap” TDC, the other at the BDC and the rest two at middle stoke, the inertia force on the crankpin bearing is strong.
In comparison, in the two stroke Cross Radial PatAT the compression / combustion force cancels a good part of the inertia force acting on the crankpin from the four pistons of the row.

The modern bearings are much better than those in the R-R Pennine. Thin connecting rod big end (15mm or less for normal size bore, even for racing engines) is not rare.

Four such connecting rods on a common crankpin would require only 60mm crankpin length. To cancel the inertia moment (offset cylinders) and to distribute the loads along the common crankpin better, fork connecting rods can be used used.

With the fork connecting rods of the Cross Radial PatATi and 60mm total pin length (for a, say, 86mm bore 86mm stroke 2,000cc two stroke engine), the total bearing area at the heavily loaded side of each con-rod big-end is substantially larger (say 40%) than in a 15mm wide conventional connecting rod.

Besides, the Master – Slave connecting rod architecture is not good for a single row (or a double row) two-stroke engine because it comes with strong vibrations, it introduces internal geometrical asymmetry that effects the combustion, the tuning, the fuel efficiency etc.


Regarding the cooling:

If you mean the shape of the cooling fins, you are right; in the drawings/animations of the Cross Radial PatAT, each cylinder was made by revolving of a cut view for simplicity.


Hello Wuzak.

The front row and the rear row of cylinders of the double-row Cross Radial PatAT are equivalent: there are no obstacles hiding the rear cylinders from the cooling air stream (from the top of the cylinder head till below the exhaust ports).

Some modern BMW Boxer motorcycle engines use air-cooling for the cylinders and water-cooling for the cylinder heads.

With the Cross Radial PatAT driving the propeller of a small airplane, the air falls on the engine with substantially higher speed than in a motorcycle.


The famous Rotax 912 uses liquid cooled cylinder heads and air-cooled cylinders:



With 1,352cc (82 cu.in.) the Rotax 912 makes 100bhp at 5,800rpm. Its weight (together with the speed reduction unit) is 56Kp (124lb).


Compare the vibration-free quality of the 4-cylinder Cross Radial PatAT with that of the four-cylinder Boxer Rotax 912; besides its unbalanced inertia moment (due to the cylinder offset) the Rotax 912 also suffers from a heavy (as heavy as in the even firing in-line-four engines) inertia torque.


With its unconventional architecture and its lightweight crankshaft, a single-row 4-cylinder 2,000cc (86x86) Cross Radial PatAT will have half the weight of the Rotax 912, will provide (as a turbocharged Direct Injection Diesel) twice as much power (200bhp) and will achieve a substantially higher mileage.

Thanks
Manolis Pattakos

Edited by manolis, 23 June 2015 - 13:37.

[Wuzak]

Rolls-Royce X-24s had pairs of cylinders firing at the same time, so there would be 60° between firing events, not 30°.

[manolis]

Hello Wuzak.

You write:
“Rolls-Royce X-24s had pairs of cylinders firing at the same time, so there would be 60° between firing events, not 30°.”

With simultaneous combustion in pairs of cylinder the loads on the long crankpins of the X-24 crankshaft get even higher.


Unless I am wrong, a R-R X-24 can be even firing:

According the drawing of the X-24 Pennine of Rolls Royce, you can think of it as made by four “conventional” even-firing “straight-six” engines sharing the same crankshaft (the crankpins are arranged at 0, 120, 240, 240, 120 and 0 crank degrees).

The two oppositely-arranged six-cylinders (top left and bottom right) form a 12-cylinder boxer engine. The two sides of the boxer-12 have a 180 degrees phase difference (when the first piston of the one bank is at the TDC, the first piston of the opposite bank is at 180 degrees). This allows an even firing 12 cylinder (combustions per 60 crank degrees). I.e. combustions at 0, 60, 120, 180, 240, 300, 360, 420, 480, 540, 600 and 660 crank degrees

The other two six-cylinders (top right, bottom left) form another 12-cylinder boxer engine, which can be even firing, too (combustions per 60 degrees).

The two abovementioned 12-cylinder boxer sub-engines have a 90 degrees phase deference, which means that the second 12-cylinder boxer fires at: 90, 150, 210, 270, 330, 390, 450, 510, 570, 630, 690 and 30 (30=750-720) crank degrees.


That is, a R-R X-24 can be even firing (one combustion per 30 crankshaft degrees).

Is there a reason behind the uneven firing in the Rolls Royce X-24?

Thanks
Manolis Pattakos

[Wuzak]

I am not certain with the Pennine, but it certainly was the case with the Vulture.

 

I think that the dual firing was to simplify the ignition system.

 

The Cylinder banks were number A and B top, C and D bottom, the cylinders in each bank numbered from 1 (at the airscrew end) to 6.

 

The firing order was

1A, 3D, 2C, 6B, 3A, 5D

1C, 4B, 5A, 6D, 3C, 2B

6A, 4D, 5C, 1B, 4A, 2D

6C, 3B, 2A, 1D, 4C, 5B

 

The Vulture had two magnetos for safety, each firing one of the two plugs per cylinder.

[manolis]

Hello Wuzak.

In case the R-R X-24 Vulture has the same arrangement with the Pannine, with dual firing you cannot have 60 degrees intervals between combustions.

The dual combustions will happen at 0, 90, 120, 210, 240, 330, 360, 450, 480, 570, 600 and 690.

The intervals between combustions are: 90 degrees, 30 degrees, 90 degrees, 30 degrees and so on.


At the end, the Rolls Royce Pannine (one of the biggest and most complicated reciprocating piston airplane engines, ever) has several issues to address.


Forget the R-R X-24, choose your favorite reciprocating piston airplane engine and compare it with a turbocharged direct-injection Diesel single-row Cross Radial PatAT.

Thanks
Manolis Pattakos

[gruntguru]

The firing order was

1A, 3D, 2C, 6B, 3A, 5D

1C, 4B, 5A, 6D, 3C, 2B

6A, 4D, 5C, 1B, 4A, 2D

6C, 3B, 2A, 1D, 4C, 5B

 

Didn't you mean:

 

1A, 3D, 2C, 6B,

3A, 5D, 1C, 4B,

5A, 6D, 3C, 2B,

6A, 4D, 5C, 1B,

4A, 2D, 6C, 3B,

2A, 1D, 4C, 5B

 

?

[Wuzak]

The way I put it was the same way it was in the document Air Publication 1801A: The Vulture II and IV Aero-Engines (December 1940) I obtained from the British National Archives.

[gruntguru]

Well aren't they silly.

(Tongue still wedged firmly in cheek)

 

Not sure why they grouped it that way - each line represents 1/2 revolution.

 

I think the 6 x 4 table makes more sense, each column represents the firing order for an in-line bank.

Edited by gruntguru, 25 June 2015 - 06:23.

[bigleagueslider]

Forget the R-R X-24, choose your favorite reciprocating piston airplane engine and compare it with a turbocharged direct-injection Diesel single-row Cross Radial PatAT.

Thanks
Manolis Pattakos

OK. Let's compare your Cross Radial PatAT with a pedestrian Lycoming O-360. Lycoming has manufactured and sold thousands of O-360 engines, and they have performed safely for hundreds of thousands of flight hours. As for your Cross Radial PatAT engine, I would speculate that the total number of this type of engine in service is currently somewhere between zero and one. Can you provide any evidence to the contrary?

 

Don't get me wrong, I truly admire your creative efforts. But you should not make unwarranted comparisons of your unproven concept to engine designs with established track records.

[Wuzak]

Or, less than the number of Pennines or EXEs (pre-war, 22l air cooled X-24) built? ie 1 of each.
 
The Pennine only ran on the test bench, but made 2800hp for a 5 minute take-off rating for slightly better than 1hp/ci (~2750ci capacity).
 
The Exe was not taken into production but was flown for many hours in Rolls-Royce's Fairey Battle test hack.
 

 

The Exe wasn't pursued because resources were needed for the Merlin.

 

The Pennine wasn't pursued because Rolls-Royce saw the gas turbine writing on the wall.

[manolis]

Hello Bigleagueslider.

You write:
"OK. Let's compare your Cross Radial PatAT with a pedestrian Lycoming O-360."


In the following is a theoretical comparison of the two engines.


Lycoming O-360, general characteristics

Type: Four-cylinder, dual magneto, horizontally opposed, four-stroke aircraft engine

Bore: 5.125 in (130 mm)

Stroke: 4.375 in (111 mm)

Displacement: 361 cu in (5,916 cc)

Dry weight: 258 lb (117 kg)

Fuel type: 91/96 avgas minimum grade[12]

Oil system: 8 US qt (8 l) dry sump

Cooling system: air-cooled

Power output: 180 hp (134 kW) at 2700 rpm

Compression ratio: 8.5:1




Cooling:

Don’t the front cylinders of the Lycoming hide the rear cylinders from the cool air stream? Reasonably the rear cylinders run hotter.

Isn’t the cooling of the four-cylinder Cross Radial PatAT by far more uniform?


Lightweight:

A turbocharged di Diesel 2,000cc Cross Radial PatAT (the turbocharger is the scavenging pump, too) is several times more lightweight.


Power:

In order the Lycoming to make at 2,700rpm 180bhp, the required torque is: 180 / (2.7*1.4)= 467Nm.

The straight-four 2,000cc turbo-diesel 4-stroke of BMW X3 provides 360Nm of torque from 1500rpm to 2250rpm.

The 2,000cc Cross Radial PatAT is a 2-stroke; 467/360 = 1.3, i.e. the Cross Radial PatAT has to operate at only 65% of the mean effective pressure of the above BMW engine in order to achieve the same power with the 6lit Lycoming engine (direct drive of the same propeller at both cases).


Smoothness and vibrations:

With four 4-stroke cylinders (Lycoming) a power pulse happens every 180 crankshaft degrees.

With four 2-stroke cylinders (single row Cross Radial PatAT) a power pulse happens every 90 crankshaft degrees.

For the same power at the same revs the power pulses of the Lycoming (which load the casing of the airplane) are twice as strong than those of the Cross Radial PatAT.

In the Lycoming there is a significant unbalanced inertia torque on the airplane frame (with the one piston at TDC all the four pistons are stopped, after 90 degrees all the four pistons move with high speed). Pistons of 130mm diameter cannot be lightweight.

In the Lycoming there is also an unbalanced 2nd order moment (rocking couple).

In comparison, the Cross Plane PatAT is fully balanced; taken together with the substantially weaker power pulses of the PatAT (for the same power at the same revs), a more lightweight airplane frame is allowed.


Crankshaft:

The Lycoming crankshaft has four crankpins and only three main bearings.

By the way, when the back cylinder (away from the propeller) is at some 50 crank degrees after combustion, what is the loading of the front crankpin?
Is the case worse or better than the “long” crankpin of the Cross Radial PatAT?


Cost:

From e-bay:



for US2,500$


Complexity:

Too many parts (pushrods, rocker arms, pivots, valve springs, valves, cylinder heads, camshaft).



If you can omit several of them, you avoid the problems they could generate.


Fuel / mileage.

Besides the heavy 6lit Lycoming engine, the airplane has to carry the required fuel. And this fuel is a couple of times more (spark ignition, low compression, old technology) than the Diesel fuel required by a similar power direct injection Diesel for the same range.
Besides the smaller quantity of fuel for a specific range (lower operating cost etc) it is also the safety of the Diesel engine (way less flammable fuel, no high voltage circuit, no need for electric circuit in case of emergency, etc).


It is only a theoretical comparison; however it shows many advantages of the one engine over the other.
Do I miss something?

Thanks
Manolis Pattakos

Edited by manolis, 25 June 2015 - 07:45.

[Wuzak]

I would be wary of comparing car engine ratings with aircraft engine ratings, particularly for general aviation engines. I'm quite sure that a car engine when modified and rated for aircraft use will lose quite a lot of its power.

[manolis]

Hello Wuzak.

You write:
“I would be wary of comparing car engine ratings with aircraft engine ratings, particularly for general aviation engines. I'm quite sure that a car engine when modified and rated for aircraft use will lose quite a lot of its power.”


You are right.
A conventional car engine cannot operate at its top power permanently.

But this is not the case with the Cross Radial PatAT 2,000cc di Diesel running at 2700 rpm and providing 180bhp.


Here are some specs of the BMW 2.0d (diesel) 6MT (190 HP) engine:
Cylinders: Inline 4
Displacement: 1995 cm3
Power: 190 HP @ 4000 RPM
Torque: 400 Nm @ 1750–2250 RPM
Fuel: Diesel
CO2: Emissions 143 g/km
Turbocharger with variable inlet geometry, common rail direct injection

This BMW engine makes 190HP at 4000 rpm.
At only 2700 rpm, this 4-stroke diesel engine provides about 140HP. (i.e. some 75% of its peak power), with a mean piston speed lower than 9m/sec.
This engine can operate at 2.700rpm and full load for several days without reliability issues (actually this BMW engine can operate permanently even at 4,000rpm and full load without reliability issues)..

As the BMW diesel engine, similarly the 2,000cc Cross Radial PatAT can operate for several days at 2700 rpm wherein it provides only a part of its peak power.
In analogy to the BMW diesel engine, at 4,000rpm the Cross Radial PatAT would provide 190*(0.65*2)=247HP, keeping the mean effective pressure at only 65% of the BMW.


From another viewpoint:

It is not strange for a giant two-stroke marine engine to operate continuously (for weeks) at full load with 20bar mean effective pressure, 9m/sec mean piston speed and a TBO (time between overhauls) a few years.

To make with the Cross Radial PatAT 180bhp at 2700 rpm (i.e. as much as the Lycoming) the required mean effective pressure is only 15bar (75% of that of the above giant marine engine) and the mean piston speed (for 86mm stroke) is only 7.8m/sec.


According the previous analysis, a 2,000cc 4-cylinder direct injection Diesel 2-stroke providing – on a continues basis - 180bhp at 2,700 rpm is nothing special, and the engine operates reliably, away from its peak power and away from the high revving range.

Differently: Based on the data from the 2,000cc Diesel of BMW, in order to make 180bhp at 2,700rpm the 2,000cc direct injection Diesel Cross Radial PatAT operates at 2/3 of the peak power revs and at some 2/3 of the full load.

Thanks
Manolis Pattakos

[Greg Locock]

"A conventional car engine cannot operate at its top power permanently"

 

How many hours would you mean by that? just interested - the very first Metro A+Turbo proto ran 100 hours at full power straight off the drawing board. When car engines are used as stationary engines they tend to be run at 3000 or 3600 rpm obviously, but they run at almost full throttle to get good efficiency. And that is for lifetimes of the order of thousands of hours. So perhaps that canard is just an old wives tale - the rest of the car would fall apart but the engine would just sit there doing what it was designed to do, drink, breathe, go round.

Edited by Greg Locock, 26 June 2015 - 00:40.

[Kelpiecross]

I am not certain with the Pennine, but it certainly was the case with the Vulture.
 
I think that the dual firing was to simplify the ignition system.
 
The Cylinder banks were number A and B top, C and D bottom, the cylinders in each bank numbered from 1 (at the airscrew end) to 6.
 
The firing order was
1A, 3D, 2C, 6B, 3A, 5D
1C, 4B, 5A, 6D, 3C, 2B
6A, 4D, 5C, 1B, 4A, 2D
6C, 3B, 2A, 1D, 4C, 5B
 
The Vulture had two magnetos for safety, each firing one of the two plugs per cylinder.

If the RR X24 had pairs of cylinders firing together - shouldn't the firing order be listed as twelve pairs of firings - not 24 separate firings?

[Kelpiecross]

Manolis - aren't you assuming a little too much - like- the power output, that it would run for several days etc.? I presume the engine has not been built let alone tested - you may find that odd piston induction arrangement doesn't work as planned.
But - I do like the crankshaft/big end layout - why not a conventional 2-stroke diesel arrangement?

[manolis]

Hello Greg Locock.

The "100 hours at full power" of the Metro A+Turbo at its first run is impressive.

But the TBO of the reputable airplane piston engines (like the Rotax boxer, the Lycoming O-360 etc) is much longer: 2,000 hours (i.e. 83 days, or 12 weeks, or 2.7 months!).

And while a malfunction of a car engine is just a problem (a trouble), the malfunction of an airplane engine can easily end up into a catastrophe.

Oppositely to a car engine (that runs at its full power for short periods and only from time to time), it is easy to keep an airplane engine at its full power from take-off to landing (the Rotax 912 comprises a 2.4:1 propeller speed reduction unit).

The modern car Diesel engines (like the BMW 2,000cc of X3) provide their peak power at low revs (4,000 rpm for the BMW, which means a mean piston speed of only 12m/sec). It would not be a surprise if they can operate reliably at full power for several months.
On the other hand, the high revving gasoline engines (like the Honda Civic B16A VTEC 1,600cc, 160bhp/7600rpm, 19.5m/sec mean piston speed) cannot do the same.


Hello Kelpiecross.

Theoretically speaking:

With 86mm bore and stroke, a 2,000cc di turbo-Diesel Cross Radial PatAT has, at 2,700rpm, a very low mean piston speed (7.8m/sec).
In order to provide the 180 bhp of the Lycoming O-360 / 6lt, it needs a lower supercharging than the abovementioned BMW engine.
It has four-stroke lubrication (crankcase, crankshaft, connecting rods and piston skirts / lower cylinder liners wherein the thrust loads are taken).
It is fully balanced.
It has top mileage (a “compound” – the turbocharger is also the scavenging pump – direct injection Diesel having, as a 2-stroke, substantially lower mechanical friction).
It is green.
It is simple.
It is cheap.
It is extremely lightweight.

Theoretically speaking, the above characteristics make a top airplane engine.
Are there any mistakes in the theory?


According the previous, theoretically the di turbo-diesel Cross Radial PatAT fits with cars and trucks, too.
As a diesel its load control is based on the quantity of fuel injected.

Thanks
Manolis Pattakos

Edited by manolis, 26 June 2015 - 05:12.

[bigleagueslider]

"...It is only a theoretical comparison; however it shows many advantages of the one engine over the other.....Do I miss something?"

 

Manolis-

 

Indeed, you entirely missed the point I was making. I intentionally chose the O-360 for my comparision specifically because it is a very simple, crude design that has been commercially successful in spite of these factors. Any comparison, even theoretical, between your engine concept and the O-360 is meaningless, since you have no performance, reliability, or marketing data to support your claims. Unlike Lycoming, who have been producing and selling thousands of their O-360 engine model for over 4 decades, you have yet to even build and test a single example of your engine. Let alone get it approved for type certification, and then manufacture and sell it at a profit to general aviation.

 

The current list price of a new O-360 is over $40K. If you honestly think your engine concept is so technically superior, you should have no problem making $millions selling it. However, you should remember that something like half of the sales price of a new O-360 goes just to cover the legal liability costs Lycoming will be subject to over the life of that engine.

 

While I appreciate this thread is just a topic of dicussion, I also would hope you might grasp just how incredibly difficult and costly it is to bring a new GA engine product to market.

[gruntguru]

If Manolis thought it was easy he wouldn't be posting here.

You are right, this is just a technical discussion.

Manolis is right, his design outperforms the Lycoming in many areas.

You are right, a new design is not going to obsolete the Lycoming overnight (and often not for technical reasons).

[manolis]

Hello Bigleagueslider.

You write:
"You have no performance, reliability, or marketing data to support your claims."


The calculations were based on the existing BMW 2.0 di Diesel engine of X3 (same number and size of cylinders, both diesel direct injection).

The calculations where also based on the typical mean effective pressure and mean piston speed of the current top-reliable giant two-stroke marine engines.

Only simpleminded assumptions and big safety factors were used.

If you see some trick or mistake in the analysis, please explain and make your own calculations.


You also write:
"The current list price of a new O-360 is over $40K. . . However, you should remember that something like half of the sales price of a new O-360 goes just to cover the legal liability costs"

So the cost reduction has to do with the other half of the "over $40K" cost.
There are still too much money to be saved.
Do you see any reasoning for being so expensive the "very simple, crude design" Lycoming O-360?


From another viewpoint:

Suppose the Cross Radial PatAT was already in production and in service.
In such a case, what would be the meaning of such a technical discussion?

Isn’t it interesting and challenging, for an engineer / scientist / mechanic, to calculate and predict before making and testing?

I am still looking for “theoretical advantages” of the Lycoming O-360 over a direct injection turbo-diesel Cross Radial PatAT.

Thanks
Manolis Pattakos

[Kelpiecross]

One of the main advantages of engines like the O-360 is the general layout and packaging of the engine. The layout gives a high centre of rotation to the propeller allowing better ground clearance for the prop - especially with a nose wheel undercarriage. (The PatAT might have a slight problem in this area). Also the flat-four configuration gives a very short engine allowing better weight distribution. As for being crude etc. - I doubt if a inline four with twin cams and four valves per cylinder etc. would make any more power than the O-360 at the same limit of 2700 RPM.

I suspect the $20K price tag (half of the $40K price) is mostly due to the better quality of the components and more careful assembly - probably to a similar standard as a racing engine for a car. $20K would be cheapish for a 360cu racing engine. I was told that the Jabiru light aircraft engine used typical race engine pistons, rods, valve gear etc. to get the quality needed. (Sadly Jabirus have proven to be a bit unreliable)

Manolis's ideas etc. are a bloody sight more interesting than a lot of the other topics on this forum.

[Charles E Taylor]

Aero Diesels

 

 

 

I do wonder why we have not seen a successful modern Aero-Diesel. Many millions expended, no notable success.

 

The Zoche has been underdevelopment for more than 25 years, and is very close to the PatAT. http://www.zoche.de/specs.html  All of the other developments are either stalled or abandoned.

 

 

 

I wonder why?

 

 

 

 

Charlie.

 

 

 

[manolis]

Hello Charlie.

In the specifications of the Zoche aero-diesels the weight of the ZO-01A (4-cylinder 2-cycle Cross Radial 2.66lt Diesel) is 84Kp (185lb) while its power is 150hp at 2500rpm.



Quote from Zoche web site:
“Charge air pressure is generated by a combination of a highly efficient mechanical blower and a newly developed advanced turbocharger, reducing power loss at altitude. The quadruple flow compressor scroll is integral to the monobloc intercooler, resulting in a very high efficiency of the turbocharger and intercooler installation.”

Are there any photos / drawings of the internals (architecture) of the Zoche engine?

Is it a master-slave con-rod design?

Is the transfer asymmetric?


While the 212gr/kWh BSFC at cruise (225gr/kWh at max power) is good giving a 38% Brake Thermal Efficiency (36% at max power), the specific power (power to weight ratio) of the Zoche is not good at all.

With (150/84)=1.8hp/Kp the power to weight ratio of the 4-cylinder Zoche is the same with the power to weight ratio of the naturally aspirating 4-cyclinder four-stroke Rotax 912 (100hp, 56Kp including the reduction gearing).

The Rotax revs at 5800rpm (with 2.4:1 reduction the propeller rotates at 2500rpm, i.e. the same with the propeller of the Zoche).
The high revving is not a problem if you think that the Rotax 912 has a 2,000h TBO.


According Zoche:
“A TBO of 2000 hours is anticipated. In accordance with certification practice, however, early production engines will have a substantially lower TBO. This will be increased according to field experience. Currently a novel buy-back scheme is planned where aero-diesels, having reached their TBO, will be returned to the factory and replaced by new ones at the cost of a conventional overhaul. . . .Without valves, valve gear, and ignition systems, the aero-diesel needs less comprehensive maintenance procedures than conventional gasoline aircraft engines, thus reducing downtime and further saving operating costs.”

Drawback of the Rotax 912 is its higher BSFC (285gr/kWh at full power, i.e. 27% more than Zoche’s, which means that for a, say, 5 hours flight, the Rotax at take off carries some 25Kp (55lb) more fuel) which also means some 25% higher running cost.
Drawback of the Rotax 912 is also the flammable fuel it uses.


The 2.66lt 2-stroke Cross Radial Zoche aero-diesel provides 150hp at 2,500rpm which means that it operates at a MEP (mean effective pressure) of only 10bar.
Only 10bar MEP is not at all good, especially if you think that it comprises a turbocharger and a mechanical blower; the low MEP explains the low power to weight ratio.

Unless I am wrong, Zoche is based on conventional symmetric transfer, which means that a substantial part of the compressed air pushed into the cylinder by the blower / turbocharger finds, after the closing of the transfer, the exhaust port open and escapes from the cylinder before compression.

Throwing away the mechanical blower of the Zoche aero-diesel and applying the asymmetric transfer ( http://www.pattakon....ttakonPatAT.htm ) things change a lot because at the beginning of the compression a substantially larger quantity of air is trapped into the cylinder.
And double (i.e. 20bar) MEP means double power at the same revs.

EDIT:

Isn't a 20bar mean-effective-pressure too high ?
Can the engine operate reliably at 20 bar MEP?

The giant 2-stroke marine engines operate constantly at 20bar MEP for most of their long "life".
But they are giant, making the comparison questionable.

The BMW 2.0lt 4-stroke 190 HP diesel engine of X3 (previous post) provides 400 Nm of torque @ 1750–2250 RPM.
This simply means that from 1750 to 2250 rpm the BMW 2,000cc 4-stroke operates at 25bar MEP (the calculations are quite simple).


Thanks
Manolis Pattakos

Edited by manolis, 29 June 2015 - 02:43.

[manolis]

Hello Kelpiecross

If the layout of the Cross Radial 4-cylinder PatAT puts limitations in the ground clearance with a nose wheel undercarriage, you can turn the engine 45 degrees (as an “X” instead of a “+”) and mount it in the airplane frame.

An alternative is the opposed piston PatAT, with a pair of counter-rotating propellers:



The youtube video is at https://www.youtube....h?v=aXvRaVqiHxs

With a turbocharger as scavenging pump and 4-stroke lubrication of the crankcase / crankshaft / connecting rods, the slightly longer pistons (with the oil rings at their middle) allow bigger propeller diameter.

With such an engine at the nose (or at the tail) of a small airplane, the airplane frame becomes extremely lightweight because it is loaded only by the weight of the engine (which is small) and by the forward thrust force from the rotating propellers; nothing else. All inertia and combustion loads are cancelled inside the engine before the engine mounts.


The airplane gets more stable, too.

Imagine a conventional small airplane; if the almost closed throttle gets suddenly “wide open”, the airplane destabilizes (it can even turn upside down).
The same if, for some reason, during a flight with the engine operating at max power the ignition systems fails suddenly to provide high voltage to all spark plugs.

Think the great difference in the case the PatAT Opposed piston with the two counter-rotating propellers is used as the power unit in the same small airplane.

Thanks
Manolis Pattakos

[bigleagueslider]

"From another viewpoint:  Suppose the Cross Radial PatAT was already in production and in service. In such a case, what would be the meaning of such a technical discussion?"

 

If this were the case it would no longer be a "technical discussion", since you would have legitimate performance data to support your claims, but you don't. What is so difficult to understand about this fundamental point?

 

While you are free to make any claims or comparisons about the perceived technical superiority of your engine concept you like, that does not provide proof of their legitimacy. Ultimately, the commercial market decides what the best product is. And until your engine concept has displaced existing products like the O-360, your claims have no basis.

 

There have been numerous recip diesel aircraft engine efforts over the past 15-20 years (like Zoche, Delta Hawk, SMA, Diesel Air Limited, Wilksch, or Thielert), and none of them have achieved commercial success despite spending millions of dollars on their development. So why would your proposed concept be any different?

[manolis]

Hello Bigleagueslider.

You write:
“So why would your proposed concept be any different?”


Because without introducing serious side effects it solves significant problems of the prior art.

The only technical objections I heard so far, were the cooling and the “long” crankpin of the Cross Radial PatAT.
The cooling could not be better (think of the cooling of the rear cylinders of the commercially successful O-360 Lycoming).
As for the “long” crankpin, it is not a significant issue as explained. The long crankpins of the R-R X-24 (as long as the cylinder bore) proved not an issue. The crankshaft of the Rotax 912 (with the four crankpins and the only three crankshaft main bearings) proves reliable in practice (2,000h TBO) despite its worse loading.


The saving of some 150Kp (330lb) from a small airplane is an important issue (it means a substantially longer range and / or more passengers and / or more luggage).
How?
By making the same power at the same revs with a, say, 80Kp (176lb) lighter engine.
By reducing the weight of the airplane frame because the engine is rid of inertia vibrations and because the combustion pulses are weaker and more frequent (smoothness, quietness).
By reducing substantially the quantity of fuel required for a specific range.


Take in comparison the EcoMotors OPOC wherein two oppositely located Junkers-Doxford share the same crankshaft for the sake of a more vibration-free operation and a more lightweight structure.
Despite the big names involved (Bill Gates, Khosla etc) and the big money funded (some $100M, I thinl), they failed to make it a commercial success; worse even they failed even to put an OPOC prototype in actual service (in a truck) and give it for tests to the journalists.


Back to PatAT Cross Radial.

Besides the weight saving it is also the cost saving.
The ownership cost drops a lot (cheaper engine, simpler airplane frame, smaller fuel tank etc).
The running cost drops a lot, too (substantially better fuel efficiency resulting in higher mileage).

For the sales, all these are important key points.


On the other hand you are right: it is not at all easy to compete big long-established companies and tested / reputable products.


If you look at the Opposed Piston PatTAi engine :



what you can see is a highly specialized engine, “perfect” for a specific unconventional use: the Portable Flyer (today a niche product, tomorrow “who knows?”).

According the theory the PatATi Portable Flyer can fly way better than the spectacular / unbelievable Rossy’s Jetpack (vertical take-off and landing, hovering, hours flight duration, fuel efficient, etc, etc).

Proving the potential of the PatATi Portable Flyer in practice (take-off, hover, fly horizontally at high speed / high mileage, aerobatics, landing), the Cross Radial PatAT (and several other projects like the PatMar at http://www.pattakon....takonPatMar.htm , for instance, about which we had a long discussion in another thread) will be seen without suspicion.
And then, “who knows?”

Thanks
Manolis Pattakos

[gruntguru]

 

 

If this were the case it would no longer be a "technical discussion", since you would have legitimate performance data to support your claims, but you don't. What is so difficult to understand about this fundamental point?

 

While you are free to make any claims or comparisons about the perceived technical superiority of your engine concept you like, that does not provide proof of their legitimacy. Ultimately, the commercial market decides what the best product is. And until your engine concept has displaced existing products like the O-360, your claims have no basis.

 

There have been numerous recip diesel aircraft engine efforts over the past 15-20 years (like Zoche, Delta Hawk, SMA, Diesel Air Limited, Wilksch, or Thielert), and none of them have achieved commercial success despite spending millions of dollars on their development. So why would your proposed concept be any different?

It will only be a truly "technical discussion" when posts like this (mine) and that (yours) disappear. Manolis continues to make sound technical arguments in favour of his claims while you continue to state the obvious yet irrelevant - "many have tried, none have succeeded, why would yours be any different?"

[bigleagueslider]

It will only be a truly "technical discussion" when posts like this (mine) and that (yours) disappear. Manolis continues to make sound technical arguments in favour of his claims while you continue to state the obvious yet irrelevant - "many have tried, none have succeeded, why would yours be any different?"

How does stating the obvious qualify as irrelevant?

 

Apparently you have no experience working in any field of science or engineering. Such claims as those made above are never accepted as fact without any reliable/comprehensive data to support them. As an engineer, if I submitted a design/analysis report for critical review without comprehensive /reliable/established data sources to support it, I would be roundly criticized by my peers. While I appreciate the creative efforts of Manolis, I have not seen where he has even come close to making a comprehensive technical validation that his concept is everything he claims. It is not acceptable scientific/engineering process to make a couple unsubstantiated claims, and then say "prove me wrong". Unfortunately for Manolis, in these situations the burden of proof lies entirely with the party making the claims.

[Lee Nicolle]

One of the main advantages of engines like the O-360 is the general layout and packaging of the engine. The layout gives a high centre of rotation to the propeller allowing better ground clearance for the prop - especially with a nose wheel undercarriage. (The PatAT might have a slight problem in this area). Also the flat-four configuration gives a very short engine allowing better weight distribution. As for being crude etc. - I doubt if a inline four with twin cams and four valves per cylinder etc. would make any more power than the O-360 at the same limit of 2700 RPM.

I suspect the $20K price tag (half of the $40K price) is mostly due to the better quality of the components and more careful assembly - probably to a similar standard as a racing engine for a car. $20K would be cheapish for a 360cu racing engine. I was told that the Jabiru light aircraft engine used typical race engine pistons, rods, valve gear etc. to get the quality needed. (Sadly Jabirus have proven to be a bit unreliable)

Manolis's ideas etc. are a bloody sight more interesting than a lot of the other topics on this forum.

Having seen a Lycoming in bits I was actually underwhelmed by the quality. It was the turbo version that had burnt a piston after about 300 hours in a twin engine 8 seat aircraft.. How well it had been treated is a matter of conjecture.

 

The Whyalla airlines disaster a decade or so ago was a recently overhauled [by Lycoming] that seemed to have been assembled with that Copper no stick 'grease' that many use [inc me] to install spark plugs in alloy heads. You have to be very carefull or it will get in the combustion area and glow and cause detonation. This it appears was the cause of the engine failure. Though one engine was quite fresh [as described] the other was near the end of its life and when stressed it too failed.  I have seen broken race engines that have had an excess of that stuff cause detonation and break pistons, hammer rod bearings and blow out head gaskets. from supposedly proffesional people.

 

To me Manolis engine is so theoretical as never to be produced. As is thousands of other designs. Some of those stupidly over technical radials from the war too did not seem to be around for very long. The jets, at least in theory are so simple.

As was the more simple piston engines such as the Merlin.

Radials ever only make sense? in an aircraft because of size considerations.

Though the above simple agricultural Lycoming probably makes as much power as most of those old radials did

That is why simple is better,, and 2 stroke is a thing of the past

[gruntguru]

While I appreciate the creative efforts of Manolis, I have not seen where he has even come close to making a comprehensive technical validation that his concept is everything he claims. It is not acceptable scientific/engineering process to make a couple unsubstantiated claims, and then say "prove me wrong". Unfortunately for Manolis, in these situations the burden of proof lies entirely with the party making the claims.

Unfortunately for you, Manolis is not making such representations to a potential manufacturer. He is putting his proposals and supporting arguments to a technical forum and asking for technical criticism.

 

I am sure Manolis is familiar with the "burden of proof" cliché - from the mouths of actual engine manufacturers. Quite pathetic to have it trotted out here!

[Greg Locock]

On the other hand the Revetec engine has, apparently, been certified for aero use, and to say the least, it makes Manolis' engines look conventional.

 

http://www.revetec.com/

 

Frankly, I was a doubter from day 1 but Brad went ahead and got the thing tested properly by a 3rd party, and seems to be at least approaching critical mass.

[Wuzak]

Some of those stupidly over technical radials from the war too did not seem to be around for very long. The jets, at least in theory are so simple.

As was the more simple piston engines such as the Merlin.

Radials ever only make sense? in an aircraft because of size considerations.

Though the above simple agricultural Lycoming probably makes as much power as most of those old radials did

That is why simple is better,, and 2 stroke is a thing of the past

 

The "stupidly over technical radials from the war" lasted as long post war as the Merlin. I assume you mean the Hercules and Centaurus?

 

The Merlin was relatively small and relied on a lot of boost to make power. Not the best thing for commercial aircraft, which was, basically, the only game in town as the military changed to gas turbine designs. The Merlin was not a great commercial success.

 

Its big brother, the Griffon, remained in military service until 1991 with the Shackleton, but there doesn't seem to have been any push for a commercial application of them.

 

The American radials were simpler, probably more to your liking. They had even more commercial success in airliners such as the Lockheed Constellation and the Douglas DC-6 & 7.

[manolis]

Hello Greg Locock.

“A work of pure genius!” was the title of a technical “discussion” that lasted several years at http://www.ultimatec...read.php?t=2958

I was one of those trying to explain to Brad the technical faults of his project. He was not willing to listen.

In response to my very first post (page 9) in that “technical” “discussion”, Brad wrote among others:
“The problem with amatures like these people is that they don't understand engines and even though some theory may look good and the design looks simple, doesn't mean there are no inherant problems with what they are trying to do. Companies like this just burn investors money without having any prospect of getting an engine to perform or get to production.”

Now the money / funds of his investors are gone.
And Brad is out of Revetec for years.

I write “discussion” because Brad’s “fans” (or, perhaps, Brad himself under several names) used to point the finger at anybody daring to technically question his “genius design”.

The Australian Orbital is where the lab tests of the Revetec engine took place, giving good BTE (brake thermal efficiency).

The real problem of the Revetec design (just like the real problem of Russell Bourke design) was, and still is, its reliability: after a few minutes of operation under load, the rotor-cam (tri-lobe) surfaces and the track-roller-bearing surfaces start wearing and the engine soon falls apart (as happened in the lab tests in India, in the lab tests in Germany, in the lab tests in Turkey).

To bypass the problem, Brad left his initial design (wherein several gearwheels were necessary for the synchronization of the counter-rotating tri-lobe cams) for the sake of the simpler X-Revetec design. But the real problem was elsewhere: in the extreme loading of the cooperating surfaces between the cams and the track roller bearings (and the torsional loads / torques on the pistons, an issue Brad never understood).

When Revetec published in the Internet the video of the first (and last I think) run of the first Revetec Diesel (made in Turkey by Atalan makinen) it was really depressing to see wherein the initial great “dream” (presented in every technical magazine around the world) ended up.


Seriously now.

For a Jetpack or a Portable Flyer the prime mover has to provide, among others, top power to weight ratio and good fuel efficiency.

Top power to weight ratio with bad fuel efficiency is not a good choice.

Yves Rossy uses a set of four Jets (Cat-200).
In a previous post I calculated (based on the available data) the overall BTE (brake thermal efficiency) of these Jet engines and it is less than 2.5% (two point five per cent).
The weight of the required fuel for just ten minutes of flight is some 2.5 times bigger than the weight of the engines.

Thanks
Manolis Pattakos

[Greg Locock]

Thanks for the update, it seemed too good to be true!