to measure detonation in the octane engine.
A Gas Evolution Burette was used
with the early Bouncing Pin and
was incorporated with the first CFR
units in the 1920's.
Light knock would result in low current
flow through the sulfuric acid,
generating a small amount of hydrogen
gas. As the knock increased, the gas
( and you thought octane rating
was difficult today!)
The knock meter (Weston) was not
conceived & designed until 1929.
Knock Engine Manual dated May 1942.
20's, when Dr. H.C. Dickinson described
a " diddle pin" (not shown) he used to detect
whether an airplane engine was knocking.
The diddle pin was simply a free pin
held loosely in a guide with it's lower
end resting on the engine cylinder surface.
The pin vibrated during normal combustion
but bounced violently when knock occurred.
At right: An experimental Bouncing Pin.
|The Bouncing Pin was steadily improved
through changes that came from many sources.
Bouncing Pins remained standard instrument
of knock intensity until 1948.
Left: Leverage Bouncing Pin
|The Bouncing Pin and the characteristics
of the knock intentsity signal it produced
were, and continue to be an integral
component of the complex collection of
factors that define octane numbers that as
measured by Research & Motor Methods.
Left: Plungerless Bouncing Pin.
Right: Electro Magnetic Knock Indicator --->
Not really a bouncing pin, but an early type
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