LETTERS

By Staff
Published on November 1, 1960
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10 hp Russell and 4 roll McCormick husker and shredder. (Picture taken in 1900 or 1901)
10 hp Russell and 4 roll McCormick husker and shredder. (Picture taken in 1900 or 1901)

THAT MARSH VALVE GEAR AGAIN

Since the Advance is one of my favorite engines and I like the
Marsh valve gear, the recent articles by LeRoy Blaker, Edward
Hutsel and Joseph May were very interesting to me. I have
engineered two different Advance engines with Marsh gears a total
of six threshing seasons, also several different engines with Woolf
and Link gears, and I certainly will not agree that the Marsh is
the ‘worst’ valve gear.

I agree with Mr. May in that I do not think a clear exhaust or
‘bark’ is an indication of economy or efficiency. I think
engines with a short distance from exhaust port to nozzle such as
the Advance simple or Avery under-mounted will ‘talk’
louder than where the exhaust steam has to travel farther and maybe
thru a heater. The tandem-compound Advance engines have a soft,
muffled exhaust, this means to me that the expansive force of the
steam has been used in the cylinders to produce power instead of
making a bark up the stack. Advance engines are usually considered
as very economical so the Marsh gear must not be too bad. I
understand Advance Rumely tested other valve gears on their new
engine, before deciding to use the Marsh gear.

I have found the Marsh gear easy to care for and keep snug. I
believe the small number of joints and the short, easy motion
accounts for this. And in spite of the lack of extra notches for
the reverse lever the Advance seems to handle as easy or easier
than most engines, running slow ‘stiff-geared’.

The large, heavy strap and arm of the Woolf and other
single-eccentric gears, with considerably more throw than the
travel of the valve-stem, along with the sliding block, guide and
pivot all add up to many joints with possible lost motion and
noise. I am not trying to say that the Woolf is the ‘worst’
gear, I like the sound of a well-adjusted Case as well as the next
man, but I will not agree that the Marsh is the ‘worst’
valve gear either.

I agree with Mr. May, that a properly designed valve seat will
not wear uneven from ‘hooking up’. When the valve opens to
‘lead’ at one end the other end slides off the raised edge
of the valve seat, if not made this way it could possibly wear
shoulders on the seat even with fixed cut-off gears. I would be
inclined to believe that with reasonably good water and good
lubrication it would take a long time to wear a shoulder even if
the valve stopped short of the edge of the valve seat.

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