hydraulic drive

[Guest]

Picture shows hydraulic pump.Seller says it is rebuilt and cost $2k.Just needs to be reconnected .Is this a can of worms?How common is this type of drive?I have only ever been on one yacht with hydraulic drive and that was years ago and it was noisy as hell.I have never worked on them and know nothing.Is it something to avoid or can they generally be sorted out to give good use?

[marinheiro 352]

they are very common on large yellow (and other colours) machines used for moving rocks and dirt, and driving drums on concrete agitator trucks and all sorts of other things - still noisy and guaranteed to have an oil leak somewhere. Not many used in yachts here since the 70's, examples are some Cav 32's, Diva (formerly Whispers of Wellington) and the odd cat.

What are you going to do with it?

[Guest]

I am looking to livaboard and cruise the coast.

Are you saying that size pump would work on earthmoving machinery?

[marinheiro 352]

They come in many many sizes, have a look at a bobcat or concrete truck for an idea.

I saw your other post with the pictures of the yacht.

If it is so easy to connect up, the should do this before trying to sell the boat (i would row around it once and then row away very fast!!!).

[wheels 543]

Ummm, hmmmm, where to start??

Hydraulics are good at doing a specific job in a way that no other machinery could do. But if something else can do the job, then the hydraulics should be the last resort. The first issue with Hydraulics is that it is very very inefficient. The most efficient hydraulics still waste 50% of the power in just pushing the oil around. The second issue is that they are real expensive. Yes it could easily cost 2K to recon the pump. It could easily cost the same for the hyd motor. The same again for the control bank. And if something fails at sea, there are no make shift easy fixes. Hoses cost an arm and a leg and if you blow one, you have oil everywhere and they are specialised to repair. No bit of tape wrapped around a leak to get you home. The pumps can create prssures anywhere from 1000PSI to 3000PSI for most mainstream systems. Specialized go to 10,000PSI. But even 1000PSI and you lose a liot of oil real quick with a leak.

If the system is new, I would not expect any oil leaks. They can be clean as a whistle. But the day will ocme when seals wear and oil drips and they need overhauling.

Yes they are noisy. They whine like a banshee. And the other problem is that the pump needs to be driven at full RPM to be the most efficient. So the Engine has to be full noise all the time. The speed is controlled by the controll gear controlling the hydraulic motor. So the throttle will not be just the engine throttle.

So what's the story here? is there a hydraulic motor connected to the shaft?

I don't understand what the intentions were with this idea. Unless the engine is not where it was designed to be, not angled for shaft alignment and shaft not aligned properly. It is an area that needs someone clued up to look at and some very careful consideration. In a nut shell, if this installation can not have a Gearbox fitted and connected to the shaft, i would run from this.

Now on the other hand, hydraulics can really come into their own when doing things like controlling anchor winch and some real big yachts even have furling systems and mainsheet winches controlled by hydraulics. But that is real big mega yacht type stuff. Anchor winches are common of commercial boats. But they go that way only because they already had pot haulers or net winches.

This boat better be damn cheap mate. I can see the possability of some big bucks being sunk into this thing.

[Bad Kitty 252]

Yeah what wheels said.

I looked at this when we built the cat.

Noisy, inefficient & produce lots of heat.

If it can be done with a standard installation, ie gearbox & shaft, or saildrive etc then save the grief.

[wheels 543]

A thought, if you had the money, you could always fit Electric Gen/motor.

However, there is one thing that worries me. If the builder has done this, then what other weird and wonderfuls have been done. I imagine he had this stuff and thought he could save a buck. Which makes me wonder where and what else was done to save the bucks.

[Guest]

Wot wheels said ... and never search for a hydraulic leak with your hand, use a bit of cardboard or paper.

 

A fine leak at 3000psi will dock your fingers off before you know it - think like a water-cutter cutting steel plate.

[Guest]

I certainly dont recomend it.

 

I put a hydraulic system in Midnight Oil a hundred years ago, infinitly variable pump, flush lifting drive, fixed prop, engin over the keel etc. While it should have been efficient, it was a lemon.

 

Heavyer than standard system, wined worse than DR, big heat losses ......

 

wouldnt advise it

[PaulR 3]

Further to above, the motor pod / shaft can be easily cracked (Hit a log?) and you lose all oil underwater rapidly. Been there, done that.

 

Compare the cost and ease of installation of a sail drive.

1 hole in hull, seal timbers, bolt on mounting ring, rubber seal and poke leg through.

You could re-mount existing motor. I don't know if it could work, but could you fit a shaft between existing motor and sail drive? Could be cheaper / easier than new motor mounts etc.

 

Then again, traditional shafts seem to work well for most people; otherwise the vast majority would of swapped a long time ago.

 

The biggest pain is the fully rpmed engine for hour after hour after hour. Noise heat and vibration. Enough to turn anybody to drink heavily & quickly!!! Check fridge size ASAP!!

[Guest]

Thank you everyone for the reasoned replys.No thanks to the mindless baggers.On my budget I am always going to be looking at boats with defects but this looks like more work than I can do.To normalise this boat the engine would need to be dragged out of the stern and mounted probably somewhere under the companionway.A suitable transmission would need to be found and mated.Any pro's here,feel free to comment on the cost of professional help.

 

Anyone know if there is any market for the hydraulic parts?There must be some kind of hydraulic transmission connected to the shaft.

[davidj 0]

For what it is worth, I have had a similar system on my Cavalier 32 mated to a Bukh 20 for the last 15 years without any major problems.I have blown an o ring once and lost all the oil into the bilge, and I have had the Pump and drive unit overhauled once in fifteen years, it is still going strong, it does leak a little oil but it is not noisy.

 

David j

[Guest]

Thanks for that David.I think I am going to let it go.I have no way to get out to the boat to view the outside and the seller wont help without $1000 non refundable.I offered to do the deal without him coming up from Greymouth but he insists I pay his travel costs up front.

[Dagwood 57]

Thanks for that David.I think I am going to let it go.I have no way to get out to the boat to view the outside and the seller wont help without $1000 non refundable.I offered to do the deal without him coming up from Greymouth but he insists I pay his travel costs up front.

 

That's a weird approach on the part of the seller! I'd wager it'll still be on the market in 6 - 12 months time and he might be a little more "negotiable".

[Guest]

I had a hydraulic drive on one of my barges. 14mts shoebox shaped barge that at times displaced 45-50 tonnes and had nice windage, all driven at a 6kt cruise by a old 60hp Perkins that usually ran at around 1/2 revs. Worked exceptionally well but we did take time to make sure all components were well matched, that did make a big difference.

 

Would I use the same in a pleasure boat? Probably would if it was a bigger boat, knot in anything small though.