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Author: mikemike Date: May 7, 2008 21:30
On May 7, 12:41 pm, Jack Linthicum earthlink.net>
wrote:
> How much of the 109's ability to kill new pilots could be traced to
> the landing gear? I notice the FW 190 had a very "wide stance" as it
> were.
Not as much as thought: after all, Spitfire and Wildcat pilots
did OK without such a high bodycount
>
> I am concerned that German pilots got tired while British and American
> ones didn't. The cockpit of the 109 was very cramped and the pilot had
> to do a lot of things that tabs and better canopy design did for the
> Allies. No one ever designed a "bubble canopy" for the 109?
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Author: mikemike Date: May 7, 2008 21:53
> Sure, but with 130 octane fuel you could get somewhere between 10 and
> 20%% better efficiency. You dont have to use that improvement for more
> horsepower, just lower the boost and gain range instead.
Doesn't work that way: the high octane doesn't help as much
with part throttle cruise operation, only really comes into play
for what the US called 'Military Power' and 'War Emergency Power'
settings, high HP settings that could only be used for minutes.
And if used, meant the engine had to be rebuilt afterwards
The US AvGas rating system wasn't direct Octane numbers, but was
like 100/130 and 115/145, where the first was an equivalent #in Lean,
and the 2nd in AutoRich mode
That said, going from 87 to 100 was about an average 11%% increase in
performance, and increasing TEL to get v. high octane will get you
Lead fouling and other troubles like fuel shelflife: tradeoffs abound.
**
mike
**
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Author: s2artms2artm Date: May 7, 2008 23:27
On 7 May, 20:53, mike yahoo.com> wrote:> On May 7, 12:33 pm, s2a...@ gmail.com wrote:
> >> Sure, but with 130 octane fuel you could get somewhere between 10 and
>> 20%% better efficiency. You dont have to use that improvement for more
>> horsepower, just lower the boost and gain range instead.
>
> Doesn't work that way: the high octane doesn't help as much
> with part throttle cruise operation, only really comes into play
> for what the US called 'Military Power' and 'War Emergency Power'
> settings, high HP settings that could only be used for minutes.
>
> And if used, meant the engine had to be rebuilt afterwards
>
> The US AvGas rating system wasn't direct Octane numbers, but was
> like 100/130 and 115/145, where the first was an equivalent #in Lean,
> and the 2nd in AutoRich mode
>
> That said, going from 87 to 100 was about an average 11%% increase in
> performance, and increasing TEL to get v. high octane will get you ...
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Author: mikemike Date: May 8, 2008 05:07
> I am afraid it does work like that. The thermodynamic efficiency of an
> engine is proportional to the compression ratio, higher octane allows
> for higher compression ratios. Of course the engine in question has to
> be strong enough to stand the improved BMEP etc, but higher
> compression will always improve your MPG.
Octane add nothing to the power of the fuel, just delays detonation
aka knock. you can add in more compression, which gives more
power, and more heat, which isn't linear, but geometric.
Set where knock is around the corner at cruise, trouble waits at WEP
The DBs direct injection masked the need for that octane boost
somewhat, giving better fuel distribution that carbs overcame
with richer mixtures, reducing dangerous cylinder conditions
(sidenote, DFI was one of the final fixes that helped reduce the
problems on the B-29), but the DB was already ahead of every other
engine in having higher C/R already
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Author: MicheleMichele Date: May 8, 2008 09:03
"mike" yahoo.com> ha scritto nel messaggio
news:2d06b767-ea59-46f5-b163-39ba7c2bf283@l64g2000hse.googlegroups.com...
On May 7, 12:41 pm, Jack Linthicum earthlink.net>
wrote:
>> How much of the 109's ability to kill new pilots could be traced to
>> the landing gear? I notice the FW 190 had a very "wide stance" as it
>> were.
>
> Not as much as thought: after all, Spitfire and Wildcat pilots
> did OK without such a high bodycount
The Spitfire's carriage was narrow and folded outwards, like the Bf 109's;
but the carriage of the latter also folded from the fuselage, not the wings,
making it even narrower. If you couple that with the strong engine torque,
add a new pilot and a slightly uneven runway (like the makeshift ones they
had to use in the Pas de Calais), you'll easily get a deadly sideways tilt
on take off; a wing touches ground and it's over.
On top of that, some seem to have thought that the carriage was not strong
enough. Again, add a new pilot and a less than perfect runway, and you may
have an accident upon landing.
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Author: s2artms2artm Date: May 8, 2008 15:51
enOn 8 May, 04:07, mike yahoo.com> wrote:> On May 7, 4:27 pm, s2a...@ gmail.com wrote:
> >> I am afraid it does work like that. The thermodynamic efficiency of an
>> engine is proportional to the compression ratio, higher octane allows
>> for higher compression ratios. Of course the engine in question has to
>> be strong enough to stand the improved BMEP etc, but higher
>> compression will always improve your MPG.
>
> Octane add nothing to the power of the fuel, just delays detonation
> aka knock. you can add in more compression, which gives more
> power, and more heat, which isn't linear, but geometric.
>
> Set where knock is around the corner at cruise, trouble waits at WEP
>
> The DBs direct injection masked the need for that octane boost
> somewhat, giving better fuel distribution that carbs overcame
> with richer mixtures, reducing dangerous cylinder conditions
> (sidenote, DFI was one of the final fixes that helped reduce the
> problems on the B-29), but the DB was already ahead of every other ...
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Author: mikemike Date: May 10, 2008 09:15
> This suggests that had they had the 100/130 fuel produced by the Yanks
> they could have got the CR up to 9 ish.
But even with 115/145 fuel available the US and UK for the later Mk
Merlin, Griffon and Allison stayed at 6.0 to 6.6, choosing to run
higher boost pressures when needed, and dump in Alcohol/Water
to keep cylinder head temps from holing the pistons in combat
> Raising the CR from 7 to 9 would give a good rise (10%%+) in
> efficiency. Note that the higher the CR the less waste heat is
> produced. High octane fuel doesnt have more energy (generally) the
> gain is in the efficiency with higher compression ratios.
> With better fuel, and engines tuned to use it, the range of the 109s
> would be improved.
But the SFC of the 605 did not get much better with the increased
C/R, 0.473 from the 0.474 of the 601. The RR Griffon had .42 SFC
with 6.0 compression on 100PN fuel, and Allison had .45 on the
same fuel with 6.65 C/R
More range from C/R did not seem to be the route taken,
better mixtures were investigated, as well as RPM, boost,etc.
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Author: kenneykenney Date: May 10, 2008 22:55
In article
a23g2000hsc.googlegroups.com>,
marathag@yahoo.com (mike) wrote:
> choosing to run
> higher boost pressures when needed, and dump in Alcohol/Water
> to keep cylinder head temps from holing the pistons in combat
Compression ratios are more important in naturally aspirated engines.
When Velocette tried supercharging a racing engine they lowered the
compression ratio before applying the supercharger. Charge pressure at
ignition is the most important factor and variable boost allowed that to
be kept constant or varied regardless of altitude.
There are of course other factors involved like combustion chamber
shape, squish bands valve and plug positions.
Ken Young
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Author: Allen W. McDonnellAllen W. McDonnell Date: Sep 9, 2008 00:33
Alright at this point I really must urge you to work this all up into a
Novella or even a Novel. I am fairly confident that if the tripe that
passes for historical fiction here in the USA is saleable your fine work
here will be as well.
"Michele" wrote in message
news:481f3e58$0$18150$4fafbaef@reader3.news.tin.it...
> It has been stated that not posting counterfactual timelines and just
> criticizing those posted...
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Author: MicheleMichele Date: Sep 9, 2008 09:53
"Allen W. McDonnell" provide.net> ha scritto nel messaggio
news:Xe-dnVoA-6agNVjVnZ2dnUVZ_gWdnZ2d@provide.net...> Alright at this point I really must urge you to work this all up into a
> Novella or even a Novel. I am fairly confident that if the tripe that
> passes for historical fiction here in the USA is saleable your fine work
> here will be as well.
>
Thank you for your flattering suggestion, but I don't think so. The
historical accuracy may be higher than that of some published
alternate-history fiction, but what sells those books isn't that. It's the
shocking reversal. Seel
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