Hydraulic Drive Ideas

[forsailbyowner]

So I have a boat with a running diesel and a junk transmission. I started rebuilding the trans hbw 50 hurth and find out its just not a long lasting reliable unit. I don't want it in my boat. After kicking around adapting a different trans ii come up with the idea why not just mount a hydraulic pump and a generator head to the diesel. Then use a hydraulic motor to drive the propshaft. This opens up the option of using another motor to drive the windlass. The pumps and motors I looked at were all relatively inexpensive, although I can see money going into piping control valves etc... So why not?

[Lake-Effect]

less efficient? less reliable than the hurth?

(just spritzing; I don't know hydraulic drives)

[forsailbyowner]

[QUOTE=Lake-Effect;1099608]less efficient? less reliable than the hurth?

Dpnt know efficiency of hurth. Hydraulic ad states 95% efficiency.

Hurth is described as 1000 hour transmission at cost of $1000 to rebuild. Pita to remove and reinstall.

Hydraulic drive rated for 1000 rpms continuous duty in industrial or agriculteral setting. Would be very simple to remove and replace. Cost around $300 so carry a spare or two.

[DeepFrz]

Gee, I wonder why no one else has thought of this?

[onestepcsy37]

not too common, but i read about one racer a dozen or more years ago that did that very thing. was a fairly large boat - over 50'. the advantage to the racer was that the heavy engine could be installed in the most advantageous position - directly over the fin keel, and the connection to the hydraulic motor was by flexible hose, rather than a solid shaft.

i've always thought it was a really good idea, but i haven't got the skill or the time or the $$$ to try it...

[capngeo]

Well.... it has been thought of. I used to skipper a dinner boat that was hydraulic drive; 85' of hydraulic drive. It was done so as to locate the machinery away from the diners. The main propulsion engines were also coupled to gensets which were huge as the galley was all electric. The engine room was directly below the wheelhouse and the galley was between it and the dining room. The hydraulic lines ran aft OUTSIDE THE HULL in order to cool the oil. Also it used vegetable oil in case there was a leak (there were many).

The biggest issues as I recall were corrosion as the components were off the shelf for industrial applications and not marinized.... in spite of an almost full time painter there was a lot of rust. Many bow/stern thrusters on commercial vessels are hydraulic, so I would think marinized parts should be available.

[Lake-Effect]

Originally Posted by forsailbyowner

Hydraulic ad states 95% efficiency.

This forum post suggests that hydraulic drive efficiency is in the 70's whereas motor to transmission to prop is in the 90's

I have seen hydraulic drives on applications like boat carriers (we have 4 at our club), where the big requirement is drive flexibility (pivoting drive wheels) and other uses (hydraulic lift).

This article suggests that hydraulic marine drive is more robust in variable conditions with lots of shifting. Probably not applicable to the average cruiser.

Originally Posted by onestepcsy37

i read about one racer a dozen or more years ago that did that very thing. was a fairly large boat - over 50'. the advantage to the racer was that the heavy engine could be installed in the most advantageous position - directly over the fin keel

This of course is an advantage in boat design.

I'd be much more inclined to use a diesel generator-electric motor arrangement than hydraulic. I think a diesel-electric system is much more maintainable by the average cruiser, and of course will also charge boat batteries.

I don't have the numbers but I believe a diesel-electric system with modest battery capacity (eg 1 hour of motoring) is still more efficient than hydraulic drive, and has the added bonus of battery-only operation for short jaunts like entering/exiting a marina
.

[TeddyDiver]

It's doable. Thou a couple of down sides. To get high effiency you need closed circuit hydraulics (higher pressure, costing more) Did a lot research some years ago pondering the same thing..
If you get your hands on reasonbly new Bobcat or another work machine apropriate size you could harvest most parts but they are not too cheap either..

[bobconnie]

Have been on a couple of Hydr propelled boats in the past ! One of which was a school boat for teaching folks marine subjects offshore. had two 671 detroits running hydralic pumps which ran everything aboard from movement to gennys! boat was a poor design for handling at sea, but the hyd drive worked wondefully! boat would turn in its own lenght, go from forward to reverse faster then any tranny boat Ive ever ran!! and makeing a dock in high winds it was a pure pleasure! But the whole boat was a terrible rough water boat, lots of rock and roll!! LOL and lots of sick students LOL Im sure if ya can fix the prop shaft to be fixed in place then a hydralic system should work well !! altho I would go with the biggest pump ya can fit to be able to have the thrust ya need !! Just my 2 cents

[roverhi]

Hydraulic drives were much more common when diesel was $.50 a gallon. Seemed to drop out of favor as the cost of diesel rose and the inefficiency of the hydraulic drive began to seriously hurt the pocketbook. Also think that hydraulics are high maintenance and a super big mess if a hose blows. Judging by the yellow equipment I've seen on construction sites, hydraulics seem to be leakers even when it's working properly.

[RabidRabbit]

Putting a hydraulic system is a great idea but it wont be great if you try to do it on any sort of budget. Its not the cheaper route by any means. slapping the same tranny in would be way cheaper. Ever tried to build a kick ass log spliter? Maybe the heavy duty pump and motor only cost a grand or so, but valves, hoses, brackets, custom fab, and new prop will cost you. Depends if you do it like a hack or make it a work of art. A new pump would last a very long time, no need for a spare.
Also most electric boats suck because they lack a diesel genny big enough to run them at full throttle all day.

[DeepFrz]

Hydraulic systems on a boat like drives or stabilizers also need cooling systems which add a lot of cost, complexity and weight. Properly installed hydraulic systems wont often leak however each connection is a point of failure. Trying to go cheap with hydraulics will ruin your day.

By the way my comment above was meant as tongue in cheek. If it came across as to sarcastic I apologize.

[SkiprJohn]

My friend installed one in his Juno many years ago. Had a Lister air cooled diesel and ran a pump and motor for his drive. Worked but not very well. He had a devil of a time mating the size of his prop to the drive train.

[Astral Blue]

Cost is going to be your biggest obstacle. Yes, it can be done. I have experience working with hydraulic drive systems and can without a doubt tell you it will cost far more than $1000. Your Hurth transmission will seem like a bargain compared to the cost you will incur with a properly designed system.

This isn't anywhere close to being as simple as a hydraulic drive system for a bow or stern thruster. Those systems are not designed for continuous use; nor do they have much horsepower. When you need a system rated for continuous use in a power intensive application as you describe, it becomes increasingly complex, hence increasingly costly.

You will need to have a cooling system designed for such an apparatus. This cooling system will need to handle the high pressure flows of most hydraulic systems (unless it is on the low pressure end, which has disadvantages associated with it).

Once this system is designed, purchased/fabricated, installed, and tested...then comes maintenance. That's the fun part of working with hydraulic systems. Every single point of connection will need to be constantly monitored in the initial stages of operation. And in a system like the one you propose, there will be many many many points of connection. The oil needs to be changed on a regular basis...and perhaps more often than on a transmission. There will be several filters that need to be replaced frequently.

The quick and dirty answer is "Yes. It can be done!" But since it is your boat and your project, I would suggest you do a lot of research beforehand. A good starting point is a book titled "Introduction to Fluid Power" by James Johnson. It will give you a good starting point in thinking about the advantages and disadvantages of such a system.

[TeddyDiver]

Originally Posted by Astral Blue

can without a doubt tell you it will cost far more than $1000. Your Hurth transmission will seem like a bargain compared to the cost you will incur with a properly designed system.

Think it's closer to $10000 to invest for a proper setup