*This message was transferred with a trial version of CommuniGate(tm) Pro*
----- Original Message -----
From: "Jeanne Lacourse" <cckw@mediaone.net>
To: "Military Vehicles List" <mil-veh@uller.skylee.com>
Sent: Friday, June 09, 2000 12:11 AM
Subject: [MV] Gasoline in WW2
> I heard one time a few years ago that the allies had started with 3 grades
> of gasoline: 70 octane, 80 octane, and 110 octane avgas and that after
> D-Day, they dropped the 70 octane. As a result, as I recall, some of the
> British engines could not stand the higher octane gasoline and lost valves
> due to this change.
>
I don't think its that simple, perhaps we will stir up someone with
documented records, however, it has only become important/interesting now so
documented evidence is sparse.
The one reference I had is back in the public library so memory comes into
play. At the start of WWII AVGAS was 80 octane and army pool petrol pretty
poor stuff around 60 octane, we mustn't confuse octane with other fuel
properties though, octane ratings describe only one parameter as the RAF
found out.
It would seem that 70 octane was standardised relatively early on although
the post war standard here was 80 octane. The rationalised post war RR B
Range engines were designed for 80 oct (RON) min with the high output units
(Stalwart and FV432) requiring 86 RON.
I suspect there's a connection to lead levels in the question which
generally provides a puzzle, the Ford CMP manuals of 1942 refer to "highly
leaded" fuels presenting a different and unexpected deposit in stripped
engines, there are no folklore tales here of certain types regularly burning
exhaust valves although the valve life and de-carb intervals then were
vastly different to current expectations and nimonic steel alloys were the
preserve of aero engines only, eg., Jessops KE965, today known as 21-4N
being a high chrome/nickel, non-magnetic stainless steel and highly lead
resistant.
The RAF re-visited the Schneider Cup findings, that spawned the Merlin and
Spitfire anyway, having the Associated Ethyl Co (now Ass. Octel) do some
fuel chemistry, largely the addition of huge amounts of TEL with associated
bromides to clear the lead oxide so formed into a lead halide, and we can
all see these tell-tale traces of grey streaks down aircraft cowlings and
over the wings especially on multi-engined radial powered aircraft.
With mechanical superchargers the throttle becomes a variable compression
ratio control and such WW II types have a chart of boost vs height vs revs
and there is often quoted the full throttle altitude, after this the power
falls off since boost falls off too. To an extent you can fiddle this with
prop pitch to keep the revs and boost down at lower altitudes but there is a
risk of seriously overloading the engine which did happen. Remember all BoB
fighters only had two speed props so an amount of continuous throttle
juggling was needed, the US tended to favour the exhaust turbo-charger which
is pilot-friendly self compensating but very advanced at the time and making
demands for special steel alloys that could not be produced here in quantity
under wartime conditions.
The shortage of 100 oct AVGAS which allows simply larger throttle openings
and therefore boost, led to an order being placed on the US for bulk
supplies, however this proved disappointing in service with engines being
truculent and mis-performing on the fuel supplied, detonation and damage
being the norm. Further analysis showed the blending of base fuels to be
important and the UK fuel differed greatly from the US supply mainly in the
aromatic factions, with a comprehensive and fully definitive spec a re-order
was made resulting in the first delivery of an entirely satisfactory 100 oct
AVGAS in the tanker "Beacon Hill", a large quantity was taken and stored for
reference testing and is known to this day as "Beacon Hill 100". Of course
there was plenty of TEL in there too.
We should be aware, and the States suffered before us, that lead (TEL) in
motor gasoline does _not_ produce lead in the environment, something wholly
misunderstood by the Greenies, pressure groups and subsequently, legislating
bodies. A fact borne out by the recent discovery here of well preserved
pre-Roman remains having entirely the same bodily lead absorption levels as
people in the leaded heydays of the 60's and now.
The lead burns to a lead oxide and in doing so forms a heat reflective
sphere around the burning mixture preventing detonation by radiation of the
remaining charge, the lead oxide causes fouling in the head and especially
to spark plugs and needs to be cleared. The initial, but expensive way is
to add bromide in the form of ethylene dibromide and later chlorine
eliminators. These convert the lead oxide into a lead salt that melts at
370C for a lead bromide salt and being deposited on the exhaust seat acts as
a lubricant. Crucially these lead salts are water soluble and wash out of
the environment very quickly well before ever being taken up in the food
chain. Lead in the environment largely comes from old lead pipes, anglers
line weights and shotgun pellets, not leaded gasoline.
Have we been conned. . . . . . . . . . . . . . . . . . .?
Pre war high performance engines were often specifically specified for
"non-ethylised" (unleaded) fuel, whilst the seats get a hard time the low
alloy chrome/silicon steels then in use would have the leaded fuels rot the
valve away first.
The jeep engine was originally designed to run on low octane, lead free army
petrol because the stocks and supply of precious nickel and chromium was
more importantly needed for other things, we do have a case of one unit's
jeeps being fed "liberated" 100 oct AVGAS in Italy. These were amazingly
transformed for a week or so before the valves themselves were eaten away by
the high lead fuel.
Then there is the story propagated by an innocent but somewhat loopy S.
African "engineer" about the use of metallic tin or lead to improve fuels,
this person claimed, to a competent, qualified petro-chemical chemist here,
that he helped the Russians out in WW II with just this procedure. He bases
his marketing claims for those wholly useless add to the tank tin catalyst
pellets on anecdotal hearsay and is unaware of the chemical differences
between metallic lead and fuel soluble organometallics such as TEL. It is a
known fact that the Russians had an excellent oil industry dating to 1890
and quite capable of making and operating good in-line and radial aero
engines at low altitudes where the fuel performance is so critical, they are
also renown for being somewhat less than enthusiastic about foreigners
telling them their business also.
It rates along with the $50 new jeep in a crate story.
Richard
Southampton - England
This archive was generated by hypermail 2b29 : Sun Jul 02 2000 - 23:51:28 PDT