Engine technology free-for-all

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
wuzak
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Joined: Tue Aug 30, 2011 2:26 am

Re: Engine technology free-for-all

Post by wuzak » Thu Sep 25, 2014 1:19 am

Tommy Cookers wrote:yes, my main point was to proclaim the easy ways whereby people often obtained more power than doing say 420 at lowish level, how would it not reach about 500 after a modest dive ?
Remember that IAS is always less than TAS except very near sea level.

Mosquito B.XVIs had a top speed of around 420mph TAS at around 20-25,000ft.

To get 420mph at low level is going to require some serious horsepower.

trinidefender
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Joined: Fri Apr 19, 2013 7:37 pm

Re: Engine technology free-for-all

Post by trinidefender » Thu Sep 25, 2014 2:13 am

wuzak wrote:
Tommy Cookers wrote:yes, my main point was to proclaim the easy ways whereby people often obtained more power than doing say 420 at lowish level, how would it not reach about 500 after a modest dive ?
Remember that IAS is always less than TAS except very near sea level.

Mosquito B.XVIs had a top speed of around 420mph TAS at around 20-25,000ft.

To get 420mph at low level is going to require some serious horsepower.
A good rule of thumb to work out TAS from IAS that I use while flying is add of 2% of IAS for every 1000ft of altitude at ISA conditions. Of course this doesn't take into account non-standard temperature differences but it gets you close enough.

J.A.W.
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Re: Engine technology free-for-all

Post by J.A.W. » Thu Sep 25, 2014 4:20 am

This 'Flight' article on the Bristol Hercules includes designer Roy Fedden's reasoning for the utilization of sleeve valves..
http://www.flightglobal.com/pdfarchive/ ... 02830.html
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"

J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: Engine technology free-for-all

Post by J.A.W. » Thu Sep 25, 2014 7:21 am

wuzak wrote:
Tommy Cookers wrote:yes, my main point was to proclaim the easy ways whereby people often obtained more power than doing say 420 at lowish level, how would it not reach about 500 after a modest dive ?
Remember that IAS is always less than TAS except very near sea level.

Mosquito B.XVIs had a top speed of around 420mph TAS at around 20-25,000ft.

To get 420mph at low level is going to require some serious horsepower.
True, since as posted, the increase in sea-level speed shown by the Sabre Tempest from ~375mph to ~420mph required
an increase of ~ 800 hp.

& per fiddly American engine management, here's a quote from a USAAF pilot who flew combat missions in the
8th AF in both P-38 & Merlin Mustangs.. .. Arthur Heiden..

"The P-51 was a new airplane & we were eager to fly it & were happy with it.
The P-38 kept us on our toes & constantly busy - far more critical to fly.
You could never relax with it."

No so conducive to effective combat flying, & this was shown in results.. the P-38 was dumped by the 8th AF..
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"

Tommy Cookers
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Re: Engine technology free-for-all

Post by Tommy Cookers » Thu Sep 25, 2014 10:04 am

McV bought the plane to win the race, it was a very rare and far from usual Mos
this engine spec was shown to destroy exhaust stubs in hours, causing real hazard to the airframe
it finished 3rd flying about 800 miles single-engined (this famous event is readily checkable ?)

his written account of what I call screwdriver tuning (by reducing the prop pitch) is the only one I have ever found
IMO vindication, if Merlin nn gives 1600 hp at 3000 rpm it will give maybe 1700 hp at eg 3150 even with auto boost control
I suspect that many fighter COs would make sure their engineer found them an extra 50 rpm eg 50 hp this way
also the auto boost is not invincible ?, it's only a pressure capsule moving a butterfly throttle against a big air load ?
maybe auto boost actually yielded slight overboost from selecting High Blower when the book said Low Blower ?

also McVs mention of 'manually' overboosted operation (and its legitimacy) in 'bush' flying, it's all in his last book

there was an official report on RAF Allison Mustangs in the TAF in 1942 run overboosted to eg 75" to survive over France
of course this 'manual' overboosting potential only exists at low altitude ie below FTH
just read of B-24 pilots crashing, scared to go WOT because they were on 91 Octane not their accustomed 100 Octane
the accident report said they should have overboosted as necessary even with the 91 Octane
Cook Cleland said he ran his '3000 hp 5min on ADI' engine at 4500 hp for 70 min with continuous ADI (80 gallons)
the most overboostable engine ever was the '450 hp' P&W Wasp Junior, ridiculously low-rated rpm and boostwise (80 Octane)
airshow people like the Coles bought them new (surplus) for $50 and got maybe 700 hp just by using WOT and 100 Octane


thanks Trini about the Robby transmission ('elastic bands') - and no need for a torque-limiting slipper clutch for rotor run-up
I assume that no (N/A) piston engined fixed-wing aircraft are throttled as per the Robby


not yet looking at the sleeve valve info linked by JAW
AFAIK ......
the SV was a British fetish via Ricardo's finding in the 20s that the SV was the answer to detonation limiting mep and/or CR
this was with the (then) low Octane fuel and no internal valve cooling
then ......
Heron took his 'sodium cooled' valve to the US and it was made to work well
a NACA paper reported that piston crown temp was the driver for detonation (presumably they had cooled valves)
fuel Octane was improveable, and was steadily improved for 20 years, enabling increased CR, power and efficiency
so .....
by the time the SV was made to work it was unnecessary or pointless
in the US the military liked the idea, but that's their job
the engine makers didn't like it, nor did the airlines

like all cylinder-wall valving/porting, the SV becomes less competitive at larger bore: stroke ratios
(as a conventional 2 stroke would be badly matched to frozen N/A F1's huge and unprecedented B:S ratio of 2.7)
unlike cylinder-head valving/porting (ie poppet or rotary valves), which becomes more competitive at larger B:S ratios
the 100000 ? Bristol SV engines had quite a low B:S ratio, poppet valved engines gradually went to higher B:S with rises in fuel Octane
C F Taylor said that the SV was deficient in port area (ie the 4 stroke SV, not necessarily the 2 stroke Crecy etc open-top SV)
yes, this deficiency could be relieved with eg 24 smaller cylinders as the Sabre, but why bother ??

btw @ JAW
according to Eric Brown the 8th AAF was losing P-47 and P-38 pilots who dived into the ground (in pursuit) due to compressibility
Doolittle was all over Farnborough about this, and F's mod of the 47 became standard in production (Brits also needed 47s)
the 38 was worse, but Lockheed went their own way

the Mustang airframe was better compressibilitywise than either
the Merlinisation of the Mustang standardised internal tankage that took the cg aft of safe limits at full fuel
because of this thousands of missions would have been abandoned if there had been early enemy intrusion

btw the Mosquito suffered from potentially poor dive pullout due to 'leading edge bubble' (a premature and partial stall)
due to the wing section, chosen for speed, unrelated to compressibility but maybe a cause for a speed restriction
btw British load factors (strength requirements) were lower than the US's, and later the Mosquito was found to fall short anyway
and the whole 'lightweight Mustang' project was a designing-down to the British level, and the US didn't want it
they wanted and got a lengthened Mustang so there was no cg issue with fuel

trinidefender
315
Joined: Fri Apr 19, 2013 7:37 pm

Re: Engine technology free-for-all

Post by trinidefender » Thu Sep 25, 2014 4:13 pm

Tommy Cookers wrote:McV bought the plane to win the race, it was a very rare and far from usual Mos
this engine spec was shown to destroy exhaust stubs in hours, causing real hazard to the airframe
it finished 3rd flying about 800 miles single-engined (this famous event is readily checkable ?)

his written account of what I call screwdriver tuning (by reducing the prop pitch) is the only one I have ever found
IMO vindication, if Merlin nn gives 1600 hp at 3000 rpm it will give maybe 1700 hp at eg 3150 even with auto boost control
I suspect that many fighter COs would make sure their engineer found them an extra 50 rpm eg 50 hp this way
also the auto boost is not invincible ?, it's only a pressure capsule moving a butterfly throttle against a big air load ?
maybe auto boost actually yielded slight overboost from selecting High Blower when the book said Low Blower ?

also McVs mention of 'manually' overboosted operation (and its legitimacy) in 'bush' flying, it's all in his last book

there was an official report on RAF Allison Mustangs in the TAF in 1942 run overboosted to eg 75" to survive over France
of course this 'manual' overboosting potential only exists at low altitude ie below FTH
just read of B-24 pilots crashing, scared to go WOT because they were on 91 Octane not their accustomed 100 Octane
the accident report said they should have overboosted as necessary even with the 91 Octane
Cook Cleland said he ran his '3000 hp 5min on ADI' engine at 4500 hp for 70 min with continuous ADI (80 gallons)
the most overboostable engine ever was the '450 hp' P&W Wasp Junior, ridiculously low-rated rpm and boostwise (80 Octane)
airshow people like the Coles bought them new (surplus) for $50 and got maybe 700 hp just by using WOT and 100 Octane


thanks Trini about the Robby transmission ('elastic bands') - and no need for a torque-limiting slipper clutch for rotor run-up
I assume that no (N/A) piston engined fixed-wing aircraft are throttled as per the Robby


not yet looking at the sleeve valve info linked by JAW
AFAIK ......
the SV was a British fetish via Ricardo's finding in the 20s that the SV was the answer to detonation limiting mep and/or CR
this was with the (then) low Octane fuel and no internal valve cooling
then ......
Heron took his 'sodium cooled' valve to the US and it was made to work well
a NACA paper reported that piston crown temp was the driver for detonation (presumably they had cooled valves)
fuel Octane was improveable, and was steadily improved for 20 years, enabling increased CR, power and efficiency
so .....
by the time the SV was made to work it was unnecessary or pointless
in the US the military liked the idea, but that's their job
the engine makers didn't like it, nor did the airlines

like all cylinder-wall valving/porting, the SV becomes less competitive at larger bore: stroke ratios
(as a conventional 2 stroke would be badly matched to frozen N/A F1's huge and unprecedented B:S ratio of 2.7)
unlike cylinder-head valving/porting (ie poppet or rotary valves), which becomes more competitive at larger B:S ratios
the 100000 ? Bristol SV engines had quite a low B:S ratio, poppet valved engines gradually went to higher B:S with rises in fuel Octane
C F Taylor said that the SV was deficient in port area (ie the 4 stroke SV, not necessarily the 2 stroke Crecy etc open-top SV)
yes, this deficiency could be relieved with eg 24 smaller cylinders as the Sabre, but why bother ??

btw @ JAW
according to Eric Brown the 8th AAF was losing P-47 and P-38 pilots who dived into the ground (in pursuit) due to compressibility
Doolittle was all over Farnborough about this, and F's mod of the 47 became standard in production (Brits also needed 47s)
the 38 was worse, but Lockheed went their own way

the Mustang airframe was better compressibilitywise than either
the Merlinisation of the Mustang standardised internal tankage that took the cg aft of safe limits at full fuel
because of this thousands of missions would have been abandoned if there had been early enemy intrusion

btw the Mosquito suffered from potentially poor dive pullout due to 'leading edge bubble' (a premature and partial stall)
due to the wing section, chosen for speed, unrelated to compressibility but maybe a cause for a speed restriction
btw British load factors (strength requirements) were lower than the US's, and later the Mosquito was found to fall short anyway
and the whole 'lightweight Mustang' project was a designing-down to the British level, and the US didn't want it
they wanted and got a lengthened Mustang so there was no cg issue with fuel
No problem. You have it muddled up a little bit though. In the Robinson R22 helicopters case the "elastic bands" are actually belts, similar as to what you would find in your car to power the ICE ancillaries such as a fan, alternator and such. Big difference being the strength of each belt. They have a little stretch in them but not to much.

There is a clutch unit of sorts, the belt tensioner and the belts themselves are he clutch. When you initially start the engine the belts are fairly slack and so will slip on the output drive from the engine and input drive to the rotor system. This allows the engine to start without having the starter trying to turn the rotor system as well. After start the belt tensioner then starts to place tension on the belts pulling them tight against in input and output 'gears' the tension on the belts is what actually keeps the, locked and keeps the input and output drives spinning at the same RPM. There are main rotor rpm and engine rpm sensors that control the action of the belt tensioner automatically if slip starts to happen (although if you see the clutch light come on for more than 7 seconds, as per the pilot operates handbook, then you want to pull the clutch circuit breaker to freeze the tensioners action. The light coming on means the tensioner is either getting tighter or looser).

The transmission also consists of a free wheeling unit that works by only locking drive in one direction (like pedalling and then coasting on bicycles). This is so that of the engine quits it doesn't not stop the rotor system from spinning.

Last but not least there is the transmission unit itself which consists of step down gears going to the main rotor. The tail rotor is driven directly by a shaft coming off of the freewheeling input.

Of which of them is the limiting factor I can't remember as it was a few years ago that I went but I would suspect that it is the drive belts themselves. Those are the most commonly replaced items.

As per your next question there are other N/A piston engines aircraft throttled this way (by limiting allowable manifold pressure) but many times the limitations are there more to extend in service engine life than specifically altitude performance.

J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: Engine technology free-for-all

Post by J.A.W. » Thu Sep 25, 2014 10:41 pm

T-C, a couple of quick correction points..

About F1 4-stroke bore/stroke ratios being unsuitable for effective 2-stroke power outputs..
..of course, a fundamental issue being that the naturally aspirated 4T is inherently handicapped..
..& must find a method to compensate ( maximising rpm, an expensive battle) for its lazy torque production..
..a 2T makes power on every down stroke..& thus.. its cylinder architecture is predicated accordingly..

If you read Fedden's reasoning for sleeve valves, you will see that port/time/area & swirl/combustion/ign'
advantages accrue from not having incandescent poppets crammed into the combustion space.
(& not having the valve gear mechanicals above the piston was important for aero-mill frontal area.)
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"

gruntguru
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Joined: Sat Feb 21, 2009 6:43 am

Re: Engine technology free-for-all

Post by gruntguru » Thu Sep 25, 2014 11:41 pm

J.A.W. wrote:(& not having the valve gear mechanicals above the piston was important for aero-mill frontal area.)
and of course the shorter cylinder head makes space for a longer stroke and the sleeve valve breathing is restored - everybody happy!
je suis charlie

wuzak
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Joined: Tue Aug 30, 2011 2:26 am

Re: Engine technology free-for-all

Post by wuzak » Thu Sep 25, 2014 11:57 pm

Dive limiting speed was usually structural. Sometimes also related to compressibility.

Ricardo's early work on sleeve valves was partly for compression ignition engine. The first Kestrel modified with sleeve valves was a Diesel (RR/D).

J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: Engine technology free-for-all

Post by J.A.W. » Fri Sep 26, 2014 12:04 am

@ T-C, the Brits didn't really rate the US turbo-charged fighters, & didn't want/use them in the ETO.
They did like the Mustang, & wanted all they could get, Allison & Merlin powered..

The P-38 & P-47 were expensive ( not just to build, but also to operate) ~twice as costly as a P-51..

& as the results of 8th AF combat mission effectiveness analysis showed,
the winning combination of high efficiency Merlin mill in aero-slick Mustang airframe - made the P-38 & P-47 also rans..
.. so that even with their expensively high altitude optimised turbo set ups,
.. they were dumped by the glamour 8th AF & relegated to 9th (tactical) AF for low level mud moving duties..

( & for really fast low-level work, like intercepting Nazi V1 cruise missiles, the P-38 & P-47 were too slow)..
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"

J.A.W.
83
Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: Engine technology free-for-all

Post by J.A.W. » Fri Sep 26, 2014 12:10 am

wuzak wrote:Dive limiting speed was usually structural. Sometimes also related to compressibility.

Ricardo's early work on sleeve valves was partly for compression ignition engine. The first Kestrel modified with sleeve valves was a Diesel (RR/D).
Halford's Sabre design for Napier was for Diesel, initially.. ..& then went as far as projected 2-stroke SI function..

Napier, oddly enough did not utilize sleeve valves in either Nomad or Deltic 2T Diesel mills though..
..yet NASA - in that high efficiency 2T Diesel turbo-compound study - still sees merit in the S-V..
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"

gruntguru
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Joined: Sat Feb 21, 2009 6:43 am

Re: Engine technology free-for-all

Post by gruntguru » Fri Sep 26, 2014 12:25 am

Tommy Cookers wrote:. . . . . like all cylinder-wall valving/porting, the SV becomes less competitive at larger bore: stroke ratios (as a conventional 2 stroke would be badly matched to frozen N/A F1's huge and unprecedented B:S ratio of 2.7) . . . .
Current F1 B/S = 1.509
Previous (V8) F1 B/S = 2.46

Nice post otherwise Tommy.
je suis charlie

wuzak
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Joined: Tue Aug 30, 2011 2:26 am

Re: Engine technology free-for-all

Post by wuzak » Fri Sep 26, 2014 1:45 am

J.A.W. wrote:Halford's Sabre design for Napier was for Diesel, initially.. ..& then went as far as projected 2-stroke SI function..
The starting point for the Sabre was the same as for Roll-Royce's Crecy - Ricardo's single cylinder 2 stroke compression ignition sleeve valve test mule.

The Crecy continued on as a CI engine long after the Sabre had become a 4-stroke petrol engine. Then it was realised that the Crecy could be used as a "sprint" engine and it too was changed over to petrol, though still retaining direct injection.

J.A.W. wrote:Napier, oddly enough did not utilize sleeve valves in either Nomad or Deltic 2T Diesel mills though..
..yet NASA - in that high efficiency 2T Diesel turbo-compound study - still sees merit in the S-V..
Nomad was sleeve valve.

The Deltic was based on the pre-war Junkers Diesels that Napier had been building under licence. These were opposed piston 2 strokes, with 2 crankshafts.

http://en.wikipedia.org/wiki/Napier_Culverin

Image
Last edited by wuzak on Fri Sep 26, 2014 1:50 am, edited 1 time in total.

wuzak
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Re: Engine technology free-for-all

Post by wuzak » Fri Sep 26, 2014 1:49 am

Image

J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

Re: Engine technology free-for-all

Post by J.A.W. » Fri Sep 26, 2014 2:00 am

Nice images W, but if you put a Nomad diagram up, you will see its a uniflow 2T, & sans S-V.

The Napier skill in packaging that Junkers design into the Deltic was cool, the Germans had intended to do a quad,
but then ran in to all sorts of difficulties making it work.. ..the Deltic worked by turning one crank in opposite rotation.
Dr Zachary Smith sez..
"Yes.. spare us your ridiculous remarks, you insensitive idiot!"