Two engines, one prop ?

[plankton]

A random thought. Has anyone ever put a diesel engine in each hull of a catamaran, and through take-offs and a set of helical gears had them turn a large single screw set amidships on a jack-plate ?

Could it be done ? I'm just tinkering with motor-sailer ideas and trying to ideas of eliminating underwater appendages when under sail, whist still retaining the advantages of redundant twin power (say Stehr engines that can run on just about anything).

Thoughts ?

[Landlubber]

John Goss from Fastback Catamarans did the best thing i have ever seen for this, he couples his drive leg, gearbox etc to the bell housing of a Yanmar diesel so that it could pivot up and down transversly, via the spigot shaft, worked perfect, simple application to a complicated problem, but that seems to be the way his brain works, a very clever man.

[Landlubber]

Single engine of course, but it does the trick

[FAST FRED]

Could it be done ? I'm just tinkering with motor-sailer ideas and trying to ideas of eliminating underwater appendages when under sail, whist still retaining the advantages of redundant twin power (say Stehr engines that can run on just about anything).


With enough cash most anything can be done.

One advantage of the twins that would get lost is manuverability in marinas etc.

Any out drive that will swing all the way out will solve the sail drag problem.

FF

[KevinMcKee]

Diesel-electric would solve a lot of the transmission problems.

[kengrome]

Has anyone ever put a diesel engine in each hull of a catamaran, and through take-offs and a set of helical gears had them turn a large single screw set amidships on a jack-plate ?

At one time I thought about using a rear wheel drive car's 'rear end' since it is basically a cheap and readily available planetary gearbox. I wanted to install an engine where each of the rear wheels would have been on the car. This would let both engines input power through the 'rear end' and spin the drive shaft connected to a single propeller.

Only one problem, the gearing is wrong ... or 'backwards' I guess I should say. Instead of producing prop RPM's that are 1/2 to 1/3 of the engine's RPM -- which would be ideal -- this system would spin the prop 2-3 times faster than the engine!

Too bad the gear ratios messed up my plans, I would have loved to cobble such a system together if it had been feasible. I suppose a simple v-belt reduction in between the rear end and the propeller could lowered the prop's RPM to a reasonable level, but this adds even more weight and complexity. Nevertheless it could be done and very inexpensively too.

The good thing about this system is that it would work on only one engine if the other shaft were locked, so you could use it with either or both engines -- nice for a redundant power system in a seagoing vessel.

[Tcubed]

An approach that i particularly like is to have the engine and the generator connected to the drive shaft. Normally the gen. is disconnected but should there be a problem the drive can be shifted over to it. This is perfect equipment use on larger boats which have separate generators and motors anyways, i don't know if it applies in your case.

The idea of using a differential is brilliant. Pity about the gear ratios. Myself i am very fond of using chains or belts to connect, but that's not applicable for a cat. I would say converting mechanical energy to electrical energy is probably the best bet.

[FAST FRED]

I would say converting mechanical energy to electrical energy is probably the best bet.

I would think using hydraulics would be 90% cheaper and with no risk of it not working.

Additionally the Hyd system can power other toys ,refrigeration, cruising AC generator , air cond or water maker , and a windlass.

Had a friend that built a fine cruiser , and I asked him if he wanted some self tailing winches.
He claimed tailing was no problem , as the winches were hyd powered , a ride later showed he was right.

In his case he used a small lever to re pressurize the accumulator between tacks.

FF

[Tcubed]

I don't know, i've seen hydraulic problems all over the world.

And pricing being 10 to 1 .........please explain.

I would like to know the comparisons between hydraulic energy transfer efficiency and mechano-electrical energy transfer efficiency.

Anyone out there can help clarify?

[StianM]

Hydraulic make more noice than electrical.
I can point out several new builds that use electrical moring winches.
Pulling 3 cables is alot less time consuming than bending and instaling 2 pipes.
Hydraulic is less efficiant than electric.

The only weak poin off the electric are frequensy converters. They make electrical disturbance that might cause trouble if the frequensy of the IGBT's are the same or 1/2 the one for the fishfinder or whatever.
They can also mailfunction, but that is guarantie.

You have to refill hydraulics oil, but you don't have to refill curent.

[lazeyjack]

welcome back Stian
I think there are many problems with dc, especially overheating
I built two mussell harvesters with hydraulic drives, that is a leg that raisdd and lowered with the motor right at the prop, no trouble with oil hydraulics after 20000 hours, , pick you type of pump and they are quiet

[lazeyjack]

everything hydraulic, pumps engine drive, mussel washer, davits, line hauler deck hoses, no trouble the far one with outdrive leg, , to clear the mussel lines, the inner one had twin hamilton water jets

[StianM]

Originally Posted by lazeyjack

welcome back Stian

Have too mutch to do to stay here. Ben spending the last months playing with ABB and vacon frequency drives.

We use them for alot of stuff (ventilation, cooling pumps, clean power aggregates, propulsion and mooring/anchor winches.

Seriously it's the future.

[FAST FRED]

Pulling 3 cables is alot less time consuming than bending and instaling 2 pipes.

Perhaps , but installing hyd hose with swivel fittings at either end allows pretty quick instalation.

Added advantage is hanging them into the bilge water does no harm but a bunch of free hyd cooling.

Besides the lack of the chance of electrocution , the Hyd setup can be repaired at most any place in the world.

Electric controllers and many other items would need either a replacement , or shipping back to the factory for repair.

FF

[StianM]

Originally Posted by FAST FRED

Pulling 3 cables is alot less time consuming than bending and instaling 2 pipes.

Perhaps , but installing hyd hose with swivel fittings at either end allows pretty quick instalation.

Added advantage is hanging them into the bilge water does no harm but a bunch of free hyd cooling.

Besides the lack of the chance of electrocution , the Hyd setup can be repaired at most any place in the world.

Electric controllers and many other items would need either a replacement , or shipping back to the factory for repair.

FF

I would trust cables to last longer than hydraulic hoses.
Cables have insulation so they don't get harmed by bilge water.
High pressure hydraulic are just as dangerous as electricity.
I can not think of a single place in the world where it would be more difficult to fix a simple electrical setup like this than a hydraulic.
Danfoss, vacon, abb and all the others making frequensydrives have dealership all over the world and it take 10 minutes of work to change from vacon to a abb drive. 10 minutes extra for the interfacing.