TWL: emergency propulsion
I've seen different types. One was simply an electric motor directly wired to
run off the generator by throwing a single disconnect switch (normally kept
open). The other system was a hydraulic power unit in conjunction with a
hydraulic motor rigged to the prop shaft by heavy duty belts and a jack shaft.
All the others were simply variations on those themes. I had more faith in the
hydraulic drive than the electric motor 'Get Home'. As I explained to the
family member using the electric motor: His worked purely by luck and it was
only a matter of time before the starting surge of the motor he chose burned
out the generator (which has to be very much larger than the motor, his
wasn't). On my new boat I'm going for hydraulic motor and ultimately sails as
my 'Get Home" option.
docmoss wrote:
BlankHas anyone ever heard of an emergency engine power supply set up in a
single engine trawler that uses the generator to power the prop or a prop.
docmoss
mt44
BlankHas anyone ever heard of an emergency engine power supply set up in a
single engine trawler that uses the generator to power the prop or a prop.
docmoss
mt44
Yes - I have seen a couple of set-ups and the best, as far as I could see,
was where the owner had mounted an hydraulic pump to the gen-set with a
manual clutch set-up.
On the prop shaft he had a cogged chain sprocket with an hydraulic motor
mounted to a bracket next to it with a matching sprocket..
When needed, the shaft and motor were connected by a chain which had a
removable link in it allowing one to wrap it into place and put the link
back in.
The hydraulics ran via a three position "switch" at the helm which provided
forward, neutral and reverse.
Never saw it in action but do know that he used it to get back from Port
Hardy when the main engine threw a piston a few years ago.
The chap is a marine engineer so the set up was very pro and looked like it
was a simple yet secure system.
I think he said he got about 1/2 speed out of the vessel with it.
I would put a similar set up on my boat except I don't have the gen-set
!!<grin>
Cheers
John Tones MV Penta
Victoria, BC
In "Voyaging Under Power" Leishman talks about it, but not too encouragingly.
He claims that for a 45' boat losses in the system eat up a lot of power such
that a 12.5KW generator mechanically linked to your main shaft will only turn
the prop about 240 rpm which he equates to running your main engine at the
lowest possible throttle setting. Ok for flat calm conditions, but nothing
more. To use a generator successfully for backup propulsion he claims would
require a 20KW generator and you're still not protected against a transmission
failure that locks up the shaft or the prop itself having been damaged. And a
20KW generator on a 45' boat would normally be run as a generator at such
light load that it would have a short life.
Leishman recommends that if you want emergency power (and money is no object),
install a second small wing engine diesel which turns a separate small shaft
and folding prop. A 28hp engine will presumably push a 46' boat nearly 6kts
with such a setup.
Bill
docmoss wrote:
BlankHas anyone ever heard of an emergency engine power supply set up in a
single engine trawler that uses the generator to power the prop or a prop.
docmoss
mt44
Here's one idea that I've liked - hydraulically powered stern thruster units
that can rotate 90 degrees to become emergency propulsion props. At least
you get some benefit out of them besides having a wing engine that sits
unused for ten years.
http://dickson-thruster.com/home1.htm
Bob Deering
docmoss wrote:
BlankHas anyone ever heard of an emergency engine power supply set up in a
single engine trawler that uses the generator to power the prop or a prop.
docmoss
mt44
Good Morning
Check with Dickson Bow and Stern Thrusters and on their home page you
will see a link to get home systems which are powered off your
generator. There is a stern thruster which rotates to become a get home
engine or they have a hydraulic motor that can drive your shaft if it
can be run independent of the transmission if I can interpret the
picture.
Their web page is: http://dickson-thruster.com/
Cheers
Al Binnington
GB 36 FALKOR
Guelph, Ontario
At 08:07 PM 3/12/01 -0800, you wrote:
Yes - I have seen a couple of set-ups and the best, as far as I could see,
was where the owner had mounted an hydraulic pump to the gen-set with a
manual clutch set-up.
---============================
Another way of doing it is to mount the generator over the shaft if you
have room and drop a chain on the shaft when you need the auxilary.
Also saw a rig with a large 220 electric motor driving the shaft.
.
Captain Al Pilvinis
"M/V Driftwood"--Prairie 47
2630 N.E. 41st Street
Lighthouse Point, Fl 33064-8064
Voice 954-941-2556 Fax 954 788-2666
Email yourcaptain@earthlink.net
Website http://home.earthlink.net/~yourcaptain
I have been musing and measuring all winter over just such a project
and have this idea:
Get the largest Minncota electric trolling motor (about 60 lbs
thrust), install it on the stern transom and put two dedicated size
31 deep-cycles plus a separate charger under the cockpit floor. A
long-shaft Minncota can be pulled up to clear the water completely
and when not in use, I could use the extra batteriepower with a
suitable inverter to power "comfort' appliances outside in the
cockpit (toaster, coffeemaker, boombox etc).
This setup would have an additional advantage: Since I have a single
diesel with its inherent difficult reverse maneuverability, I would
have a small "maneuvering thruster" (star-trek terminology) to help
me docking and undocking.
Along with a set of diodes (from the engine alternator), one-two
switch, gauges and wiring, I think I could get all of this done for
under $1000.- Cdn.
Any comments for/against - George of Scaramouche
I calculate that I could drive my 27 ft boat for about 6 hours with
such a setup - enough to reach shore somewhere on Lake Ontario.
At 09:09 AM 3/13/01 -0500, you wrote:
I have been musing and measuring all winter over just such a project
and have this idea:
Get the largest Minncota electric trolling motor (about 60 lbs
thrust), install it on the stern transom
---==============================
On my last boat I made an outboard bracket on the swim platform and the 15
horses moved me along just fine and the rudder steered just fine with a
little way on with the OB locked in one position.
You should have seen me dock with the OB-------The neighbors cheered.
If you use this system, carry spare fuel. If you don't have a platform,
there are brackets to mount the OB on the transom.
.
Captain Al Pilvinis
"M/V Driftwood"--Prairie 47
2630 N.E. 41st Street
Lighthouse Point, Fl 33064-8064
Voice 954-941-2556 Fax 954 788-2666
Email yourcaptain@earthlink.net
Website http://home.earthlink.net/~yourcaptain