Hi,
A bit off topic but hoping someone in here might have the experience to help
so here goes.

Have the need to put together a generator. Have a cat 3208 motor and allison
automatic with a pto output. The motor is the drive engine for a large
boat(stern wheel boat, 65 foot). I want to drive the gen head with the pto
through hydraulic pump, flow control valve, hydraulic motor to the head. The
head is a 12kw that needs 22 hp at 1800 rpm to run at full load. The motor
will run from idle to aprox 1000 to 1100 rpm for cruise speed. Have plenty
of extra hp to run the genset, only need aprox 85 hp to run boat at cruise
speed. The cat is rated at 225 hp. Would like to have some spare hydraulic
umph to also run a hydraulic controlled rudders. Won't take much for that.
Need to know what pump/motor/flowcontrol configuration I should look for to
make this work. Also, the pto unit has an air operated engage unit and the
genhead I was looking at has a field disconnect that could be coupled to the
tach to disconnect if rpm to low to drive the motor at the needed 1800 rpm.
I am pretty mechanically inclined and have no problem working on anything,
just don't have much experience with hydraulics and don't want to reinvent
the wheel if I don't have to. Any help would be appreciated.
Thanks
Mike

Michael Briggs wrote:
Hi,
A bit off topic but hoping someone in here might have the experience
to help so here goes.

Have the need to put together a generator. Have a cat 3208 motor and
allison automatic with a pto output. The motor is the drive engine
for a large boat(stern wheel boat, 65 foot). I want to drive the gen
head with the pto through hydraulic pump, flow control valve,
hydraulic motor to the head. The head is a 12kw that needs 22 hp at
1800 rpm to run at full load. The motor will run from idle to aprox
1000 to 1100 rpm for cruise speed. Have plenty of extra hp to run the
genset, only need aprox 85 hp to run boat at cruise speed. The cat is
rated at 225 hp. Would like to have some spare hydraulic umph to also
run a hydraulic controlled rudders. Won't take much for that. Need to
know what pump/motor/flowcontrol configuration I should look for to
make this work. Also, the pto unit has an air operated engage unit
and the genhead I was looking at has a field disconnect that could be
coupled to the tach to disconnect if rpm to low to drive the motor at
the needed 1800 rpm. I am pretty mechanically inclined and have no
problem working on anything, just don't have much experience with
hydraulics and don't want to reinvent the wheel if I don't have to.
Any help would be appreciated.
Thanks
Mike

I always found the people who supply custom replacement hoses to the
building industry to be very knowledgable about these things, and willing to
give advice. I would try them first.

"Michael Briggs" wrote in
:

Have plenty
of extra hp to run the genset, only need aprox 85 hp to run boat at
cruise speed.

It's not the power that's the problem, it's the FREQUENCY. A 4-pole
alternator needs to turn a CONSTANT 1800 RPM shaft speed to produce 60 Hz
AC power (1500 RPM is 50 Hz). Considering the pulley sizes for the
ratio, then engine would be turning less.

However, how are you going to run the big diesel at, say, 1800 RPM to get
60 Hz to run the motors on AC, Air conditioning compressors, fridge and
freezer compressors who all demand fairly stable frequency....and back
the boat in the slip...slowly...no changes in engine speed allowed, like
ALL BACK EMERGENCY OR WE'RE ALL GONNA CRASH!...???

Then there's the fuel at $4/gallon. The big diesel anchored out for the
night has to sit there and turn 1800 RPM at 30HP, all 7 litres of
displacement, 24/7 at anchor, or drifting or any time you don't need
propulsion.

Then there's maintenance. The big diesel has an hour lifespan limit at
some point. The faster you get there, running this stupid main engine
genset, the faster the engine shop will own your savings accounts to do
the overhaul. Most of the 9000 hours on the meter was pulling the genny
to drive the fridge in the galley and a few lights. This is insane!

That's why 65' boats all have one...or (gasp) maybe TWO...separately-
powered gensets with little engines puffing away at 2/3 of a gallon per
hour all night doing what you need.

Get a full genset. This main-engine-driven-AC-powerplant is economic
insanity.....

On Sat, 04 Mar 2006 23:44:13 -0500, Larry wrote:

Get a full genset. This main-engine-driven-AC-powerplant is economic
insanity.....

Not necessarily. If you already have one or more gensets for use at
anchor, and you spend a lot of time underway, it might make sense to
have a way to generate power from the main engines. The hydraulic
equipment can take care of speed regulation totally independent of
main engine speed, no reason to run it at 1800 RPM, all it's doing is
driving a hydraulic pump. It might be more cost effective however to
drive a large alternator from the main engine, either mechanically or
hydraulically, and use the DC output to power a large inverter. That
eliminates the complexity of hydraulic speed regulation.