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?what causes wear in generator engines?

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Posted by philkryder on January 29, 2006, 8:01 pm

During my recent research into generators, I noticed that they heavy
duty prime movers listed piston speed and travel in their specs.

This caused me to wonder.

The "stroke" on a 2-71 Detroit is 6 inches.
The stroke on a new Cat C15 is over 7 inches.

At 1800 RPM, the Detroit piston moves 1800 feet (12 inches per
revolution) per minute.
The Cat would move even more.

Meanwhile, the stroke on our little briggs tri-fuel is just under 2.5
At 3600 RPM it travels fewer than 1500 feet in a minute...
So the relative piston speed is about 16% less in the Briggs compared
to the Detroit.

Similarly, the Rod and main Journals on the big prime movers are more
than twice as large in diameter as the Briggs.

The propane fuel keeps the oil cleaner on the tri-fuels.

And all the engines can use high quality synthetics with with viscosity
ranges and good film strenghts.

And all the engines can have low oil and high temp shutdowns...
And with the small oilsump capacity, we can change the oil in the small
engine as frequently  (or more frequently ) as the big ones at less

Yet, I don't think that there is any reasonable expectation that the
Briggs would last even a tenth as long as a new CatC15 or even
venerable Detroit...

So, ??Where does the WEAR come from in these generator Wares??


Posted by Antipodean Bucket Farmer on January 29, 2006, 8:56 pm

In article
, alt.google@Kryder.com says...

Offhand, I would guess two factors.  Quality of the
metal, and precision of the parts fitting together.

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Posted by Allison-nospam on January 29, 2006, 9:23 pm


One word, heat.

Most of the smaller gens are aircooled and rely on wider tolerences to
withstand the range of temp they experience.    Water cooled engines
run at far more consistant temps and generally cooler as well so
closer tolerences are resonable and wear longer.


Posted by SQLit on January 29, 2006, 10:01 pm

I would agree with the heat principal to a larger extent.
Also the larger engines once started have enough mass in motion that they
are not constantly governing themselves up and down for the load.

I would imagine that if someone blue printed a 3600 rpm engine that it could
last a lot longer. Of course COST come in as a huge factor on them.

I have a 35 year old 5 hp Briggs attached to an Pincor 2k generator. Head,
valves rings and bearing  have been replaced once. This was a daily runner
for the first 15 years of its life. I have changed the oil  religiously
every 40 hours or once a week when it was being used. The bolts near the
exhaust are fused and every one has refused to fix the muffler. (more than a
tad loud now days)
This was an cast iron block B&S. The new ones are not made like this one
was.  I will replace it someday. But it is going to have to break first. I
will definitely go with a water buffalo when it comes time.

Posted by George Ghio on January 29, 2006, 10:36 pm

Metallurgy is a good start

philkryder wrote:

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