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Big Piston Aero Engine using today's technology


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#151 Grumbles

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Posted 04 May 2013 - 23:27

10 seconds is pretty good considering:
- poor weight distribution/transfer. The bike doesn't look even close to lifting the front wheel.
- smoking launch on a cold tyre
- no "hook up" till at least 1/2 or 3/4 track

His bikes were clearly never optimised to run great times. They were designed to put on a spectacular show and succeeded magnificently.


I think that the bike would be (even more) terrifying if it was allowed to hook up off the line. In the video he appears to launch from the bare concrete off to the side of the usual start area. Attempting to launch a direct drive bike like EJ's from the normal glued-rubber surface would be exciting in all the wrong ways.


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#152 Magoo

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Posted 04 May 2013 - 23:57

I think that the bike would be (even more) terrifying if it was allowed to hook up off the line. In the video he appears to launch from the bare concrete off to the side of the usual start area. Attempting to launch a direct drive bike like EJ's from the normal glued-rubber surface would be exciting in all the wrong ways.


Exactly, good eye. EJ would deliberately stage the bike way out of the groove. He didn't want the extra bite or the inconsistency (or to tear up the groove for the class raceers). His whole deal was about producing and managing huge amounts of wheelspin, both to put on a show for the fans and to get the bike down the track. The last thing he ever wanted was for the bike to hook up.

The bike had sort of a funny career. I could be wrong about this but to my knowledge, I don't think he ever lined up and raced against anyone even once...maybe as a stunt somewhere. When he started with it, it was one of the fastest vehicles in drag racing. Except for dragsters, there wasn't much that could touch it. Besides, it didn't fit in any class for car or bike and it didn't meet the safety regs anyway. Even in the early '60s it could run high 9s at over 150 mph most anywhere, and when he stepped on it, high 8s at 170mph. But by the end of the bike's career a dozen years later, it had been eclipsed in performance -- but not in the quality of the show it put on.



#153 scolbourne

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Posted 05 May 2013 - 05:37

Rather the opposite of big piston, but I thought it would be of interest.

Radical Performance Engines is pleased to confirm its association with the Bugatti 100P project, a recreation of the most advanced aircraft of the 1930s, by supplying two RPE 1500cc powerplants and technical support to the project.

The Bugatti 100P Project's aim is to bring to the skies a reproduction of the original Bugatti 100P airplane, an elegant design that sadly never saw the light of day due to the outbreak of WW2. A dedicated team of volunteers has painstakingly constructed the airframe, working towards a completion date at the end of the year. The Bugatti 100P featured a number of ground-breaking techniques, including dramatic, forward-swept wings, counter-rotating propellers and automatic wing-flaps.

RPE will supply two 1500cc, 260bhp four-cylinder engines to the project, highly-compact engines that are situated in the fuselage behind the pilot and connected to the nose mounted gearbox with driveshaft’s that run below the pilots elbows. The same engine design is well-proven, used in Radical Sportscars' best-selling SR3 RS racecar, in production for over a decade. Just like the original, the new Bugatti 100P will be using a race-proven engine, albeit this time controlled by an advanced engine management system with full data logging.

"RPE is extremely proud to be assisting the Bugatti 100P Project on this exciting venture, bringing one of the most distinctive aero shapes of the 30's to the skies at last," said RPE General Manager, James Williams. "With RPE power, the Bugatti 100P can exhibit the same outstanding performance and manoeuvrability that was envisaged for the aircraft over 70 years ago."

Radical Performance Engines are the world’s leading small-capacity racing engine and drive system specialists. With over thirty years’ experience in engine tuning, Radical Performance Engines has established an enviable reputation in the design and production of an increasing range of four and eight-cylinder race engines, all of which are built and developed in-house. Such is RPE’s confidence in the reliability of the engine work it carries out, much is covered by a warranty for 40 racing hours; no other manufacturer at this level of motorsport offers such cover.

http://eaa.org/news/...-100P-racer.asp

#154 Wuzak

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Posted 05 May 2013 - 06:42

Interesting....

Though they will be somewhat short of the power of the two straight eights that were originally to be used for the 100P, but somewhat lighter.

The 100P was beaten to the contra prop by the Macchi M.C.72.

#155 scolbourne

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Posted 05 May 2013 - 07:29

Interesting....

Though they will be somewhat short of the power of the two straight eights that were originally to be used for the 100P, but somewhat lighter.

The 100P was beaten to the contra prop by the Macchi M.C.72.

I expect they are trying to make the aircraft lighter so that it lands and takes-off at slower speeds for a safer flight envelope. Pure speed is probably not a major concern at this stage.

#156 bigleagueslider

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Posted 07 May 2013 - 03:34

One thing you can say about Bugatti, everything Bugatti designed looked beautiful.

However, I don't see how this aircraft would ever have achieved the speed of 500mph claimed by it's designer, given the modest 900hp combined output (optimistically) quoted for its twin engines. The forward swept wings would also likely have resulted in unstable flight due to the significant inherent problem of structural divergence at high speeds. Especially with the wooden wing structure. Fortunately for the potential test pilots, the aircraft was never flown.

#157 scolbourne

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Posted 08 May 2013 - 09:06

One thing you can say about Bugatti, everything Bugatti designed looked beautiful.

However, I don't see how this aircraft would ever have achieved the speed of 500mph claimed by it's designer, given the modest 900hp combined output (optimistically) quoted for its twin engines. The forward swept wings would also likely have resulted in unstable flight due to the significant inherent problem of structural divergence at high speeds. Especially with the wooden wing structure. Fortunately for the potential test pilots, the aircraft was never flown.

I hope that they test fly the replica under radio control initially as I can see that this could be a very dangerous aircraft.

Even making a half scale RC model might be a good way to solve some of the issues before putting a pilots life at risk.

#158 Wuzak

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Posted 08 May 2013 - 12:13

I hope that they test fly the replica under radio control initially as I can see that this could be a very dangerous aircraft.

Even making a half scale RC model might be a good way to solve some of the issues before putting a pilots life at risk.


Like this?






And some more about the 100P project (Please halp and give some money)


#159 gruntguru

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Posted 08 May 2013 - 23:14

I hope that they test fly the replica under radio control initially as I can see that this could be a very dangerous aircraft.

Even making a half scale RC model might be a good way to solve some of the issues before putting a pilots life at risk.

A bit of CFD and FEA would quickly indicate whether structural divergence is an issue. The forward sweep at the leading edge is only slight.

Beautiful aircraft!!!!

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#160 bigleagueslider

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Posted 15 May 2013 - 06:08

A bit of CFD and FEA would quickly indicate whether structural divergence is an issue. The forward sweep at the leading edge is only slight.


A model using coupled CFD and FEA is no simple matter. It would be even more difficult to model a wing structure made from wood, that has non-linear material properties.

And even if you were able to accurately model this aircraft's aero-elastic structural performance, it would still be difficult to create a control system capable of keeping the aircraft under safe control in flight.


#161 morerevsm3

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Posted 23 December 2013 - 12:16

merlin/meteor hybrid, double overhead cam, motec M800, twin turbo etc, etc...

 

Picture254.jpg

 

Picture255.jpg

 

Picture256.jpg


Edited by morerevsm3, 23 December 2013 - 12:20.


#162 morerevsm3

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Posted 23 December 2013 - 12:22

Picture011_zps1559778d.jpg

 

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#163 indigoid

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Posted 23 December 2013 - 12:27

Berrigan! I used to live near there, in Deniliquin. Bloody hot in summer.



#164 Lee Nicolle

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Posted 24 December 2013 - 00:50

merlin/meteor hybrid, double overhead cam, motec M800, twin turbo etc, etc...
 
Picture254.jpg
 
Picture255.jpg
 
Picture256.jpg

I saw a tractor pull tractor with that sort of engine on TV recently. Developed on country Vic or NSW. I presume it is the same people? Or are 2 developers modifying and turboing Merlins?

I guess if I had looked I would not have asked. The tractor in the background probably gives it away!

Edited by Lee Nicolle, 24 December 2013 - 00:53.


#165 indigoid

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Posted 24 December 2013 - 12:22

I saw a tractor pull tractor with that sort of engine on TV recently. Developed on country Vic or NSW. I presume it is the same people? Or are 2 developers modifying and turboing Merlins?

I guess if I had looked I would not have asked. The tractor in the background probably gives it away!

 

A quick Google of the company name... Tractors indeed!

 

http://www.cottameng...or_pulling.html



#166 bigleagueslider

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Posted 25 December 2013 - 02:05

After going to all the expense and effort of designing a DOHC replacement head for the R-R V12, why didn't they splay the intake/exhaust valves to allow a proper chamber shape?



#167 Wuzak

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Posted 25 December 2013 - 06:01

After going to all the expense and effort of designing a DOHC replacement head for the R-R V12, why didn't they splay the intake/exhaust valves to allow a proper chamber shape?


Wouldn't that require completely new heads? I would imagine that the cooling passages woud limit how much "splaying" could be done.

And if they wanted a pent-roof style chamber they would have been better off starting with a V-1710.

Edited by Wuzak, 25 December 2013 - 06:01.


#168 Lee Nicolle

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Posted 25 December 2013 - 09:27

After going to all the expense and effort of designing a DOHC replacement head for the R-R V12, why didn't they splay the intake/exhaust valves to allow a proper chamber shape?

If you look it is a DOHC conversion to the existing head.
A lot of work for a country engineering firm. Starting a head from scratch for that engine is probably beyond their capabilities and more importantly budget.
Really quite a considerable improvement for their application of this engine.

#169 morerevsm3

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Posted 26 December 2013 - 11:46

just the modifications to the inlet ports, along with using Chev inlet and Chrysler exhaust valves with much smaller stems, and bigger inlets saw the flow potential go from 1100hp to 1450hp NA, as well as now not requiring backfire plates anymore, when it goes back together, it should make around 4000hp



#170 bigleagueslider

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Posted 27 December 2013 - 03:32

Wouldn't that require completely new heads? I would imagine that the cooling passages woud limit how much "splaying" could be done.

And if they wanted a pent-roof style chamber they would have been better off starting with a V-1710.

 

 

C'mon, this is the modern age of digital CAD and rapid protyping.  If you have enough engineering capability to design this valvetrain conversion, you should be able to design a replacement head casting with a pent roof chamber and a DOHC valvetrain.  The protoype head castings would cost about $10K each from these guys http://www.exone.com...ions/automotive



#171 rory57

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Posted 27 December 2013 - 12:05

Nice work there.
Obviously not possible as a mod to these cylinder heads, but I am wondering how much of a ( further) improvement would come from a central spark plug, rather than two, at opposite sides of the combustion chamber? (Dual ignition not a reliability requirement for the tractor pulling application)

#172 morerevsm3

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Posted 28 December 2013 - 10:12

higher static compression, central spark plug, and proper squish area would yield pretty good improvement in power and detonation resistance, but casting complete new heads to achieve it would be time and cost prohibitive. there has been some communication between the owner, and a reno racer team and Motec...



#173 bigleagueslider

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Posted 29 December 2013 - 04:01

Nice work there.
Obviously not possible as a mod to these cylinder heads, but I am wondering how much of a ( further) improvement would come from a central spark plug, rather than two, at opposite sides of the combustion chamber? (Dual ignition not a reliability requirement for the tractor pulling application)

The ramp head chamber used on the RR Meteor V12 was a miserable design.  A pent roof chamber would be a massive improvement.  Spending $20 or $30K on a set of custom DOHC heads using a modern pent roof chamber and matching pistons would be the most cost effective way to improve the performance of a RR Meteor V12 engine.



#174 Wuzak

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Posted 29 December 2013 - 04:09

The ramp head chamber used on the RR Meteor V12 was a miserable design.  A pent roof chamber would be a massive improvement.  Spending $20 or $30K on a set of custom DOHC heads using a modern pent roof chamber and matching pistons would be the most cost effective way to improve the performance of a RR Meteor V12 engine.

 

The Meteor engine did not have the Ramp Head.

 

The Meteor was a detuned Merlin, without supercharger, IIRC. It had the Merlin flat head style. Maybe also had some different materials - such as cast iron for the blocks instead of aluminium.

 

The Ramp Head was abandoned quite quickly by Rolls-Royce after early tests showed that the full size engines were not getting as good results as the single cylinder development engines.



#175 gruntguru

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Posted 31 December 2013 - 08:05

Hi morerevs. Any info on how much power the engine has made so far?

 

There is a fair bit of potential for improvement in the exhaust system. Although there appear to be four exhaust manifolds of three cylinders each, the three cylinders chosen are not equally spaced in the firing order. This means the exhaust periods in any particular manifold will overlap and the opportunity to utilise blowdown energy is lost.

 

The correct grouping would be the front three and rear three cylinders from each bank. The turbine housings would need to be the divided type to give a total of four inlet connections (two on each turbo) but most large turbos have divided housings already. Finally the turbine housings would need to be a larger A/R to keep the boost at the same level as currently.

 

It may not sound like a big change, but the end result should see exhaust back pressure fall to significantly less than boost pressure. This alone means more power but the better scavenging that results will also permit higher boost pressure before detonation and thermal loading limits are reached.



#176 gruntguru

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Posted 31 December 2013 - 08:32

Also interesting to note (from the linked website) the primary motivation for developing the quad cam conversion was cam follower wear resulting from heavier valve springs. I wonder if a set of roller cams and rockers from Jack Roush would have been a simpler fix?



#177 morerevsm3

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Posted 31 December 2013 - 16:26

Hi morerevs. Any info on how much power the engine has made so far?

 

There is a fair bit of potential for improvement in the exhaust system. Although there appear to be four exhaust manifolds of three cylinders each, the three cylinders chosen are not equally spaced in the firing order. This means the exhaust periods in any particular manifold will overlap and the opportunity to utilise blowdown energy is lost.

 

The correct grouping would be the front three and rear three cylinders from each bank. The turbine housings would need to be the divided type to give a total of four inlet connections (two on each turbo) but most large turbos have divided housings already. Finally the turbine housings would need to be a larger A/R to keep the boost at the same level as currently.

 

It may not sound like a big change, but the end result should see exhaust back pressure fall to significantly less than boost pressure. This alone means more power but the better scavenging that results will also permit higher boost pressure before detonation and thermal loading limits are reached.

there are new inlet and exhaust manifolds for the new build, both far more efficient design than originals, going double overhead cam and shim on bucket has other advantages to the finger followers too, allows individual cam timing changes for fine tuning etc, the original finger followers go under the cam, and don't allow much more lift either, the guy that owns it has a specialist gear cutting bussiness, so conversion was done in house (as was complete gear drive setup on the new one) old engine made a little over 2600hp with conservative rpm limit and tune, new one should go close to 4000hp at 29PSI



#178 scolbourne

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Posted 02 January 2014 - 03:24

http://www.aafo.com/...lins-for-racing

 

To see the future of aero engines follow the Reno air racing threads. Obviously they are limited by cost  so have to make do with mostly what ius available but they can use modern technology and materials.



#179 bigleagueslider

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Posted 03 January 2014 - 05:35

Sadly, there is not much money available for Unlimited Air Racing.  So the only Unlimited racers remaining are those that have been racing for the past decade or two.  And most of the fastest of these are Merlin or Griffon powered. A few years back, there was the Pond Racer that used a pair of turbocharged 3.0L V6 Nissan race engines burning methanol. But after it crashed the project was stopped.

 

If someone with sufficient financial resources was serious about building an Unlimited Air Racer, it would be no problem to design and build a clean-sheet piston engine using modern technology that could easily out-perform any Merlin or Allison.



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#180 morerevsm3

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Posted 03 January 2014 - 09:09

http://www.aafo.com/...lins-for-racing

 

To see the future of aero engines follow the Reno air racing threads. Obviously they are limited by cost  so have to make do with mostly what ius available but they can use modern technology and materials.

those guys do what they know and what they have always done, I have had discussions with a couple of them that were mildly interested in Motec, but have no interest in trying turbos, or even updating to multiple stage pro chargers which are far more efficient than the original blowers, the boost levels they claim cannot be achieved with the standard valvetrain components, they blow open, you can't raise spring pressure because rockers then fail, and excessive cam wear is also a problem, and the bevel drive for the cams is also marginal, so I am very sceptical on their claimed power levels too



#181 bigleagueslider

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Posted 06 January 2014 - 01:34

The Unlimited Air racers use the mechanical superchargers the engine was designed for, rather than switching to turbochargers, because it would be extremely difficult to retrofit the existing airframes for all of the additional plumbing needed for turbocharging systems.

 

As for the issue of extremely high forces on the valvetrain required to open exhaust valves, this was indeed a problem with the very large diameter exhaust vales used on some of the big displacement pushrod 2-valve radials, like the R-4360. But was not likely much of an issue with the much smaller diameter exhaust valves used on the 4-valve engines.



#182 morerevsm3

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Posted 08 January 2014 - 11:14

you didn't read what I said, nothing to do with exhaust valves, with boost, inlet valves have boost on the back of them pushing against spring pressure, so you need higher seat pressure to compensate, but the RR merlin rockers are too weak, and camshafts too soft to raise the seat pressure, limiting the amount of boost that can be run, therefore, limiting horsepower, I also said that new pro chargers (centrifugal superchargers) would be far more efficient than 1940's designed ones that are still used today



#183 gruntguru

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Posted 09 January 2014 - 07:34

I also said that new pro chargers (centrifugal superchargers) would be far more efficient than 1940's designed ones that are still used today

I would doubt that.



#184 Wuzak

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Posted 09 January 2014 - 08:41

I also said that new pro chargers (centrifugal superchargers) would be far more efficient than 1940's designed ones that are still used today

 
 

I would doubt that.


According to Lovesey, a 2 stage supercharger for a Merlin had 70% efficiency up to a pressure ratio of 5, and a peak efficiency of ~72-73%, which was maintained from a pressure ratio of 2.5-3.5. The single stage Merlin supercharger was more efficient than the 2 stage up to a pressure ratio of ~3.5 and a peak efficiency of ~75% at a pressure ratio of 2.5.

#185 bigleagueslider

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Posted 10 January 2014 - 03:52

you didn't read what I said, nothing to do with exhaust valves, with boost, inlet valves have boost on the back of them pushing against spring pressure, so you need higher seat pressure to compensate, but the RR merlin rockers are too weak, and camshafts too soft to raise the seat pressure, limiting the amount of boost that can be run, therefore, limiting horsepower, I also said that new pro chargers (centrifugal superchargers) would be far more efficient than 1940's designed ones that are still used today

I read your comments.  But I don't think you understand what determines the amount of spring force required at engine valve seating.  The spring force at valve seating, whether an intake or exhaust valve, is determined by the valvetrain kinematics.  The spring seat force must be sufficient to keep the valve and rocker follower surface in contact with the cam profile and prevent bouncing at the point of closure.  The valve seat spring force used on any recip engine would be many times greater than the opposing force produced on the backside of the intake valve by even very high intake manifold pressures, and would not present a problem.



#186 gruntguru

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Posted 12 January 2014 - 02:20

No the boost pressure does have a significant effect. When added to the inertial force, boost can make the difference between a valve "floating" or not.



#187 bigleagueslider

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Posted 12 January 2014 - 02:41

No the boost pressure does have a significant effect. When added to the inertial force, boost can make the difference between a valve "floating" or not.

 

Valve "float" usually only occurs at or near the point of max valve lift (ie. over the nose of the cam lobe). I can't see how intake manifold air pressure would produce much net force on the intake valve due to pressure differential, since the air pressure acting on opposing sides of the valve would be similar at this point in the cycle.



#188 JAW

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Posted 13 January 2014 - 09:43

Sleeve valves don't have that issue..

 

Looking at the published rated figures for the final production variant of the Napier Sabre 7,

as listed in  'Aircraft Engines of the World' P. 256, it gives..

 

"B.m.e.p. (max) .............. 321 lb/Sq.in.

Output/displacement .....1.56 h.p./cu.in.

Piston speed (max) .......3,048 ft./min.

Weight/h.p......................0.73 lb./h.p.

S.F.C.(cr.) ......................0.45 lb./h.p./hr.

 

Rating (take-off, wet) ......3,500 h.p./3,850 r.p.m./70.6in

Rating (military, low)........3,055 h.p./3,850 r.p.m./2,250ft

Rating (normal, low).........2,850 h.p./3,750 r.p.m./8,500ft

Rating (cruising, low)........1,750 h.p./3,250 r.p.m./8,500ft

 

Not too shabby..

 

& as mentioned, a it is a real fighter mill, with coordinated engine management controls for the pilot,

so he did not have to faff about in combat, fettling myriad fuel mixture, cooling gill, boost, etc,etc

settings as demanded by US Radials, - which were properly the province of a dedicated flight engineer..


Edited by JAW, 13 January 2014 - 09:44.


#189 Ron B.

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Posted 14 January 2014 - 00:47

" using todays technology" mmmm I wonder.. having worked on engines built from 1913 through to 2013 i can assure most folks that all internal combustion engines do the same thing,they just look different.. :yawnface:

i am sure that the piston engine for aircraft had reached it's Zenith by 1944 and the only thing that wasn't used by the allies was bosch's Mfi ,later used by Gutbrod then Mercedes Benz. 

As an example of this technology i present this...

 

http://www.allpar.co...i-aircraft.html

 

V16-Aircraft-Hemi-1945.jpg

 

 

 



#190 JAW

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Posted 14 January 2014 - 00:53

Interesting find..

 

The Allies didn't use the German DFI system,

but post-war investigations by Bristol for their sleeve valve radials showed it held some promise..

 

Counter-wise the Germans didn't use turbos, or high supercharger pressures either,

& both largely due to technical/metallurgical reasons.. 



#191 bigleagueslider

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Posted 14 January 2014 - 03:39

JAW-

 

While it's true that the Allies did not use direct fuel injection systems on their piston aircraft engines during the war, the US did make extensive use of the Bendix injector carburetor design.  One difficult problem with using the crude mechanical direct injection systems available during the war was the inability of the systems to accurately control the fuel/air ratio at each individual cylinder, given the huge variation from cylinder to cylinder in intake manifold pressure, temperature, etc.



#192 JAW

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Posted 14 January 2014 - 04:19

Ah, actually the Germans were happy to run higher comp ratios/less boost as compared to the Allies,

&  the Allies liquid cooled mills esp' wanted the charge cooling value of a fuel mixture running through

the supercharger/inter-aftercoolers.

 

The ADI equipped Merlin-9 in the P-51H was cleared for a WEP of 2,200hp @ 90in, much higher boost than the R-2800s.

Higher B.M.E.P./power density too. Compare that Napier Sabre B.M.E.P. with the best service rated R-2800 figure.

 

Those fat radials were real gas hogs when juiced up to WEP, needing to run ultra-rich mixtures as 'internal' liquid cooling.

& the radial inlet/exhaust systems were less efficient than the in-lines too, even-mixture & exhaust thrust-wise..



#193 JAW

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Posted 14 January 2014 - 05:00

B-L-S, you do realize that the German DFI used on their big aero-mills was directly injecting petrol/gasoline into each cylinder,

- to ensure even mixture, it was based on Diesel injection systems & typically Germanic in precision/complexity/cost..

 

That precision was what made it attractive to use in big radials where mixture distribution could be problematic & inefficient,

compared to the even firing multiples of 120` cylinders so logically laid out - typical of well designed inline mills.



#194 Wuzak

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Posted 14 January 2014 - 06:10

JAW-
 
While it's true that the Allies did not use direct fuel injection systems on their piston aircraft engines during the war, the US did make extensive use of the Bendix injector carburetor design.  One difficult problem with using the crude mechanical direct injection systems available during the war was the inability of the systems to accurately control the fuel/air ratio at each individual cylinder, given the huge variation from cylinder to cylinder in intake manifold pressure, temperature, etc.


Wright went to Direct Injection to solve the mixture distribution issues with the R-3350. But that was after the war.

#195 Wuzak

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Posted 14 January 2014 - 06:19

Interesting find..
 
The Allies didn't use the German DFI system,
but post-war investigations by Bristol for their sleeve valve radials showed it held some promise..
 
Counter-wise the Germans didn't use turbos, or high supercharger pressures either,
& both largely due to technical/metallurgical reasons..


More correctly it was Rolls-Royce and, later, Allison who went for a lot of boost.

The Sabre didn't use a lot of boost - peak war time usage was +11ps to +13psi boost, compared with +25psi for wartime Merlins and +25psi for Griffons.

Sabres had a compression ratio of 7:1, Merlin and Griffon 6:1. The Allison V-1710 had 6.65:1 in early versions, and 6:1 in later versions. Daimler Benz's DB series were about 8-9:1, depending on model year and which bank (different CR on each of the banks).

The Germans did play around with turbos. BMW built a turbo with a 2 stage compressor and air-cooled turbine, which they then based their first gas turbine engine (cancelled before run). Daimler Benz had a few project engines with Hirth turbos. I think there were a few BMW 801 with turbo units built and in service.

#196 JAW

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Posted 14 January 2014 - 06:20

Yes, post-war, as Bristol tested too on their radials (noted post #190)..

 

Obviously the Wright was for multi-engine transport use, & pampered by a dedicated flight engineer,

rather than in a fighter, although the Bristol Centaurus fighter mills did have coordinated engine management controls..

 

The Wright always presented as a problematic mill, & Boeing re-engined their big Strats with P&W corn-cobs..



#197 JAW

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Posted 14 January 2014 - 06:28

Or, more correctly, the Sabre didn't need as much boosting, since it could out-power the equivalent capacity R-R Griffon,

( & the Griffon had to be backed off from +25lbs due to premature crankshaft bearing failure).

 

The Sabre was strong enough to hack full throttle for take-off..

When really boosted up on test, the Sabre made big power, accordingly.

 

Wartime Sabres were boost-limited due to propeller capacity,

they were cleared for +13lb once Rotol ( coincidentally Rotol was owned by R-R)

props finally became available, after much pressure was applied due to the V1

assault on London in `44..

 

Bristol also 'played around' with turbos pre-war & used them for setting altitude records..


Edited by JAW, 14 January 2014 - 06:33.


#198 JAW

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Posted 14 January 2014 - 06:47

Ricardo demonstrated that sleeve valves offered a higher tolerance to comp ratio partly due to swirl effects

& also due to no incandescent poppet valves crowding the combustion chamber..

 

I have enjoyed manually working the smooth operating sleeve valve of the display Bristol unit at the RNZAF Museum,

it is clear that once the metallurgical/tribological issues were solved, that the sleeve valve offered

significant efficiency advantages, just look at the Bristol 3,000 hour T.B.O. , & compare its S.F.C.

to R-R mills, or the B.M.E.P. of the Sabre like-wise, let alone vs the 'lazy-bones' U.S. radials..


Edited by JAW, 14 January 2014 - 07:28.


#199 gruntguru

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Posted 14 January 2014 - 06:50

" using todays technology" mmmm I wonder.. having worked on engines built from 1913 through to 2013 i can assure most folks that all internal combustion engines do the same thing,they just look different.. :yawnface:

i am sure that the piston engine for aircraft had reached it's Zenith by 1944 and the only thing that wasn't used by the allies was bosch's Mfi ,later used by Gutbrod then Mercedes Benz. 

Advances in engine technology are not limited to obvious design innovations. In 1977 the first turbo F1 engine was making about 500hp from 1.5 litres. Ten years later (under tighter regulations) F1 engines were making 800 - 1000hp in race trim and considerably more for qualifying. There were no obvious differences in the technology.

 

I have said before in this thread - a 37 litre fighter powerplant built using today's technology could have at least double the power (2,500 hp) of the Griffon. The technologies responsible would include

- Turbochargers and turbocharger design

- Materials (particularly turbine)

- Combustion chamber design

- Electronic engine management



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#200 JAW

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Posted 14 January 2014 - 07:03

Back to 1st principles time perhaps..

 

B.M.E.P. is the fundamental figure..

 

& made by high pressures in big cylinders at low revs, or small cylinders at high revs..

 

Look again at the power/weight & power/capacity ratio of that Sabre,

it offered 3,500hp ( also at 36ltr capacity) for take-off.

 

Would a 1500hp 1 lap wonder F1 turbo pass a 100 hour type-test at those out-puts?

 

Cant have DNFs - too frequently - in aircraft service you know.

 

Perhaps a look at those off-shore boat-racing Lambo 6ltr V-12s might be worthwhile..


Edited by JAW, 14 January 2014 - 07:05.