Mean piston speed

[JHertzman@xxxxxxx]

In AD7- 129 Bill Magoffin asks 
"Ok then, at what RPM do our 2L Alfa Nord motors hit the magic 2500 fpm
piston speed barrier? One would assume they would be safer higher than that
given the longer stroke and 5 bearing crank?"

The last listings I find that R&T published for their magic numbers were back
in the neanderthal era; their 1968 test of (flourish of trumpets!)the Giulia
Super gave RPM @ 2500 ft/min as 4645, and equivalent mph as 93. By the time
they tested the 2000 GTV (which they did refer to as GTV, not GT Veloce as
purists do) they had substituted piston travel in feet/mile (2060) along with
engine revs/mile @60 mph (3550) in the calculated data panel, suggesting about
73 mph for 2500 ft/min which, as has been pointed out, was just a comparative
ballpark index with which to judge the probable comparative reliability of
thoroughly mundane machines, Austin A-40s and the like. It is a fairly safe
assumption that the reason listings of piston speeds were dropped in the late
sixties is that they had become generally irrelevant. In the particular case
of two-liter Alfas, that same 2000 GT Veloce developed its peak hp (129) at
5800 rpm, equivalent to 112 mph, which (running the numbers in my head,
offhand) should be well under the 4000 ft/min which, as has been pointed out,
Indy Offys were running aeons ago and the Peugeot voiturette was running in
1910. 

In the USA, at least, mandatory certification testing for long-term emissions
compliance has radically altered minimum durability standards. I probably
wouldn't worry too much about piston speeds unless, like Fred and Bill
Harkell, I might be expecting a boost from 120 mph tailwinds.

Cordially, 

John H.

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