On Thu, 2 May 2019 07:00:44 -0400, "Mr. Luddite"
wrote:

On 5/2/2019 12:03 AM, wrote:
On Wed, 1 May 2019 19:24:04 -0700 (PDT), Its Me
wrote:

You actually don't need much of that. I had a friend growing up that had a neighbor with a "collection" of those old single cylinder engines that fired once every 4-6 revolutions. They have almost no compression, and run just fine, sort-of. Similar to this:

http://prestonservices.co.uk/item/horizontal-single-cylinder-workshop-engine/

It was pretty cool to go over on a weekend and see him fire one up.

===

I think those were engines with "spark interrupter" governors. They
had big fly wheels with a lot of momentum. In order to maintain a
constant speed and prevent over revving, the governor would actually
disable the ignition until the speed came back down. I once saw a big
collection at a county fair in upstate NY, and they were a lot of fun
to watch. Running under load they'd generally fire on every
compression stroke.




One of the dangers of diesel engines (although rare) is a "runaway"
condition whereby the governor controlling fuel intake fails and
the engine will increase RPM until something explodes or breaks.
No "ignition" to stop it or limit the engine RPM.

My wife's uncle was a diesel engine instructor in a trade school
and he described a situation when this happened with one of the
diesels used in the school's garage. A student had reassembled
the engine incorrectly, the governor didn't function and they
had a runaway when it was started. Sounds scary but was
remedied by discharging a fire extinguisher into the air
intake, robbing the engine of oxygen.


I had a situation on the Navigator once when I couldn't shut one
of the engines down. It wasn't a "runaway" but when I turned the
key fully left that is supposed to energize a solenoid in the fuel
line, stopping fuel from being supplied, it didn't work. Couldn't
shut the engine down. Finally found a manual lever on the engine
that closed off fuel and stopped the engine. The problem with the
key/solenoid turned out to be a re-settable fuse in the electrical
supply to the solenoid.


===

The "runaway" diesel syndrome that I'm familiar with is peculiar to
2-stroke models, mostly Detroits. On older engines when the piston
rings start to wear, the engine can actually start to run on its own
crankcase oil, so the throttle and governor are totally out of the
loop. Since this condition will eventually result in total
destruction of the engine, a lot of boats with Detroit Diesels have
emergency engine shutdown controls for just that contingency. When
you pull the knob it releases a spring loaded plate that closes off
the air intake to the engine. The only way to restart is to manually
reset the plate in the engine room and re-engage the latch.

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