On Fri, 21 Mar 2008 07:51:59 -0400, "Roger Long"
wrote:

You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?

I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react. The weights stick slightly and then let go.
Increasing the rate at which fuel flow can be increased during accelleration
might compensate but, if this is the case, could lead to further instability
because of "overshoot" when the governor weights unstick.

It also sounds like you might have too large an alternator. Prop demand
won't, or shouldn't, change suddenly but a sudden load like a large
alternator on a small engine like this may simply be outside the design
envelope of the fuel control system. Actually, it is probably right on the
edge so one engine is OK and the other has problems. This whole
installation was about 30 feet long so it was pretty impressive.

Here's my governor sea story:

I worked on the repowering of a large oceanographic vessel. We installed
two EMD engines (same as in railroad locomotives) that had been in a
government warehouse since about WWII. Each gearbox had a shaft running
back to DC drive motors taken out of an older diesel electric vessel and
converted into generators to run the ship's bow thruster. These motors were
about 5 feet in diameter and I put a big flexible coupling on the front of
the generators that was like half of a car tire bolted to a big metal disc.

When we first fired up the engines, one ran fine. The other began surging
and lunging back and forth as soon as the generator was clutched in with
such violence that we could see the generator beds and ship structure flex.
It was astounding and alarming during the second or two it took to grab the
PTO handle back into OFF. The whole installation was about 30 feet long so
it was pretty impressive. Both were identical so it was a real mystery.

They called in an EMD expert from Texas who flew up. We stated up the
engine, clutched it in, watched the lunging for 2 seconds and shut down.
The expert hopped up on the engine, took the cover off the governor and
said, "Get me a drill with a 3/16" bit." He drilled a hole in something,
fiddled around for about 10 seconds, put the top back on, and started to
leave. We asked if he wanted to see it run and he said, no, he knew it
would work. It did. He was on the ship for about 20 minutes.

It turned out that one engine had a marine governor and the other a railroad
locomotive governor. The railroad governor had a second set of weights
that, when sudden load was put on the engine, would rapidly increase the
fuel flow. This was so the engine wouldn't bog down when the slack came out
of the couplers of the railroad cars. When we clutched in the PTO, the
rubber tire flex coupling would wind up as. The load would cause the
governor to goose the engine and the timing was such that the unwinding of
the flex coupling would exactly match up with the time it took for the
governor to react. The impulse went back and forth magnifying each time
like a huge mechanical laser. All the fellow from Texas did was drill a
hole in the two discs that held the two sets of weights and insert a pin to
disable the goosing function.


You flew him in from Texas?

Good Lord I must be getting old. EMD guys used to be all over the
place. A very common engine at one time, We had a whole generator
house full of them at one time in Irian Jaya.

Then the company decided to modernize and sold all the old engines and
replaced them with turbines. do you have any idea how fast the shut
downs work on a turbine?

Once they got the new plant set up the entire site used to go down
several times a day. One turbine would hiccup and go off line. The
remaining units would sense an overload and Bam they would all shut
down.

That story makes me wonder, do any of the smaller commercial vessels
use turbines?




Bruce-in-Bangkok
(correct email address for reply)