Bill:
Somewhere your arithmetic is incorrect on the cost of valves.
The price I quoted of $14.00 was from my brother in law about 2 years ago who
was superintendent of transportation for Arco operating 100 tankers and
semis.
That is what they paid for sodium filled exhaust valves for Cummings or
Detroit Diesel.
My guess would be that there are many off the shelf valves available so the
designer just finds one that fits.
Hank
As Jon said, just because it fits doesn't mean it will work. Diesels expand
their combustion gases MUCH more than gasoline engines so the exhaust
is much cooler. I have no doubt that either Eaton or TRW makes the
valves for both Lyc and Cont, but this has nothing to do with the basic math
of the setup cost and the per unit cost.
I work in a manufacturing environment where we make extremely high quality
absolutely critical stuff, and this sort of discussion is often thrown about.
Like "why do we charge $50 for a 5 cent diode?" Well, it has to meet
Mil Spec, be tested in statistically significant batch sizes and in
substantial numbers,
for several different mechanical and electrical tests which cost a lot of
engineering
time, lots of technician time, lots of expensive testing equipment, lots of
planner
and purchasing agent time and lots of throwaway parts. Yes, it is "the same"
as the 5 cent diode, but not really. You may say it is just a paperwork
exercise,
but actually we reject some batches as having too many problems, and this is
critical to ensure downstream reliability, which is absolutely mandatory. I
suspect these reject parts are what you buy at Radio Shack.
The trick would be to find out who makes them and have an identical, larger
batch made. This is essentially what Superior is doing. Also, guess how
many Cummins semi tractors are out there buying valves compared to ALL
the airplanes, let alone all the airplanes that use ONE particular valve. I'd
guess about 1000 to 1, maybe 10,000 to 1. I'll bet Lyc builds less than
1000 of ALL model (new) engines per year, probably less that 100 of each
model.
Yes, Lyc and Cont have problems and are likely relatively inefficient (high
overhead) but this comes with the territory in small lot production, esp in
a highly regulated environment.
Bill
Continental was building and overhauling about 17 engines per day or about
4000 per year when I was down there a year and a half ago.
I suspect the material used in the AC exhaust valves is the same material
used in the diesel engine valves simply because they are all mass
produced on the same automated line. One could have them both analyzed
for materials used.
Paul Lamar
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