Backup Hydraulic Drive

>s his system noisy, one of the problems im imagining is the noise from the oil passing through the lines and particularly the solid mounted drive motors telegraphing the sound through the hulls.<

Hyd motors or pumps can be noisy , just listen to all that whining and grinding on an aircraft cleaning up the wheels and flaps after Take off.

They can easily be rubber mounted as a diesel engine is , just with different mounts.

The size of the hyd reseivoir helps cooling the fluid , but a cooler WILL be required . look at a keel cooler system for almost no maint, or extra crap aboard (like another sea water pump).

ASK the folks you purchase from which of their motors is quietest , there are multiple internal designs , some quieter than others.

When purchasing hose be sure a swivel connection is at BOTH ends , making servicing later easy.

 

Thanks Fred, i believe that much of the noise could be easily taken care of by insulating lines and it would be fairly easy to compartmentize the areas where the motors are but at some point you have to hard mount the motors and that could telegraph the whine through the structure. Im not yet convinced that hydraulics are the way to go partly because of the amount of oil that may be required.

Steve.

 

Just heard back from my mate on the fluid reservoir issue - he reckons it's about 15L, and he thinks it has a cooler, but is not sure, so maybe not.

Uses ATF, which was recommended by Volvo initially, although they prefer Shell Tellas, but as that may not be available everywhere and auto transmission fluid usually is......

Been changed only three times in 35 yrs, so low maintenance is the watchword.

Motors are in compartments at rear of hulls and vibration can certainly be felt through the hull but not a whine as such. Probably no worse than twin diesels.

 

> Im not yet convinced that hydraulics are the way to go partly because of the amount of oil that may be required.<

If proper cooling is installed many boats have a 10G aluminum tank .

There will be a filter to change yearly , but the make up oil is minor.

A 3/4 or 1 inch hose is required for 30 Hp of work at modest pressure , but it takes many feet of hose to hold even one gallon of fluid.

So what IS the problem?

It is true that sail boat feathering or folding props stink at propulsion , because they are created to lower drag under sail.

The prop to look at is made by Luke in Maine.

These are an old design made for motor sailors back in the 20-30s.

Inshore these are motor boats so the prop is very efficient , even in reverse.

They feather to lower the drag ,and can be locked behind the deadwood if desired to not catch crab pots.

Automatic Feathering Propellers - Paul E. Luke, Inc.
www.peluke.com/marine-hardware/boat-props/
Automatic Feather Propellers, P. E. Luke. Each propeller is custom crafted from a heavy duty aluminum bronze alloy. Full service boatyard, East Boothbay, ...

THRUST is what pushed any boat so a large diameter prop and 500rpm or so shaft speed is about as good as it gets IF you can handle the prop diameter.

The proper selection of hyd pump and motor can create almost any working reduction you desire.

And an emergency shift from Fwd to Rev at Flank ? No problem .

 

Thanks for the info Buzz, i don't see eliminating vibration but that's the case with all drives but good to hear that the whine is not an issue 15L is not too bad. FF, a lot of good info there. With the info that Buzzman has supplied I think I have enough to give to the guys at Air Hydraulics and see what they come up with. FF, how do you get the reduction with hydraulics?

Steve.

 

Try Key Power out of Surrey BC (Canada) (also reps in the US, Australia, Europe).They have a hydraulic 'get home' drive. Had one on a 55' sportfisher in 1987 for slow speed running/fishing. Driven off a genset aux. and power unit mounts between engine and shaft flange with a drop down pinion gear to engage.

 

> how do you get the reduction with hydraulics?<

The motor speed is selected for the shaft RPM you want to cruise at ,

the pump capacity is selected to satisfy the motor at the engine speed selected .

 

Aha, so you would be wanting to select an engine before designing the system. One engine that interests me is a Toyota 4y industrial gas engine, apparently a bulletproof engine with some examples having logged 80000 hrs before a rebuild in forklifts. Just pulling the specs out of my head they are about 4cyl, 2.3l 55-60hp @2300rpm, I don't remember the torque but it was given at the same rpm, so how do you determine what rpm you will cruise at to design the system around? and how do you determine prop size.

Steve

 

My mate's system is powered by a single Perkins 4-cyl diesel, mounted on the bridgedeck in the coickpit area, with the pump under the central helm station.
I think it's a 4108, but don't quote me...

 

Thanks Buzzman, particularly want to use a gasoline engine for several reasons, a gas engine itself is generally lighter due to lighter castings because they don't run at the high compression of a diesel, they are much smoother and quieter too and the usual safety issues just don't apply when mounted on the bridgedeck of a cat and free to vent vapors out the bottom and finally, the better fuel economy are largely offset here by the lower fuel cost of gasoline, its about $1.20 a gallon cheaper where i am right now. Do you know what shaft rpm he cruises at and what the prop sizes are?

Steve.

 

Nah, I don't, but you'd have to work all that out with your engineer anyway, as it depends on the weight of the boat, and his is an old heavy glas on ply cat, 47ft and about 8.5 tonnes

 

The cat I have in mind is actually pretty similar at 44ftx25x15000lbs, I am only exploring the idea at present as the original boat used a single 50hp outboard but its hard to give up that nice wide prop spacing available on a cat when it comes to maneuvering in tight spaces but as the boat is fairly light I would not want the weight of a conventional twin diesel installation. Ive owned a 36ftx18ft cat and even that is a big platform in a tight marina.

Steve.

 

Another alternative which would keep weight low would be to put bow thrusters in it, and keep the outboard.
The weight of the outboard is probably less than any 4-cyl cast iron diesel, and by the time you add the hydraulic pump, motors and lines, it's a lot of weight, which cats don't like, as you know. Light is fast, and economical.
You could also consider having thrusters mounted in the stern of the hulls as well. I've seen this on big powerboats and they can turn within their own length.
The thruster people have gizmos that enable them to operate with the steering wheel (when activated) so that as you turn the wheel either port or starboard thrusters are activated.
They can also fit switches on the gear lever controls to the outboard so that they thrusters will work in reverse or forward as appropriate.
Might be worth investigating that as an option.
Also might be worth thinking about servicing and re-sale. A 50HP outboard is a pretty common item globally, so parts and mechanics would be easy to find wherever you roam, whereas high pressure hydraulics mechanics are less common.....
Just sayin'....

 

It is pretty hard to beat an outboard, but with a wide cat there is also the opportunity to use a pair of smaller outboards for manouverability. Once i can nail down the sizes of all the hydraulic components though i can figure out the weights and see if it makes sense. I do not want a diesel, and a typical twin diesel shaft drive system would be way too heavy so of no interest. Hydraulic components are actually very available just about anywhere as they are industrial components.

Steve.

 

The problem with twin outboards is you lose the stern access on each transom.

Believe me, stairs and a handrail on the transom is the ducks guts for boarding from a dinghy.

So more negatives to consider....

Personally, I think the central 50HP and the thrusters idea would be lighter, take up less space, retain the usefulness of transom access, and be cost-effective to run.

Now, cost-effective to install might be trickier to achieve, but do your homework and let us know what you discover.