Hydraulic Drive

[Biggles]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

[ditchcrawler]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

Yes.see http://www.harnser.info/html/building_harnser.html

[Tony Brooks]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

 

 

I built & operated a number of hydraulic drive hire boats in the 60s and acted as a very minor "practical" consultant for a then well known maker of yachts who was installing them.

 

I also know of a recent narrowboat with a hydraulic drive that suffers from overheating and from what I can gather I feel excess friction in the hydraulic pipes may well be contributing to the problem.

 

If you have an "unconventional" engine position that is as it is for a very good reason then solve a lot of problems and are probably require less maintenance than a mechanical solution, however diesel electric at 48 volts may also be a more modern answer to this.

 

If you have the need for a constant speed engine (say) driving an AC generator as well as propulsion then a variable swash plate hydraulic pump or motor will allow full control of boat speed with constant engine revs.

 

It is easy to get almost any reduction "gearing" you want by altering the pump and motor capacities.

 

If you have a proven need for other hydraulic equipment like a lift, bowthruster or a selection of "workboat tools" it may economic.

 

 

Now the downside.

 

Cleanliness of the oil is paramount and my experience was that filters tended to disintegrate. I put it down to pressure/volume pulses in the system, however it seems modern systems may have overcome this.

 

There are no two ways about it, they are inefficient when compared with shaft drive but modern piston pumps and motors will be more efficient than the units I was using. With the rising cost of fuel this may be an important consideration and it also has implications for skin tank size because of the oil cooler that is normally required.

 

If a hose bursts you will very quickly spray oil all over the boat and empty the system. This is an almost immediate failure and not something one wants on flowing water. Its hard to clean up the oil as well.

 

On the upside almost all large towns have hydraulic suppliers to the construction industry so obtaining spares is probably easier than for a conventional drive.

[Phil Ambrose]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

 

For what it's worth, an awful lot of boats (including hire craft) are rear engined with hydraulic drive down here on The Broads. I have not heard of too many problems.

[koukouvagia]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

 

I've had an ARS hydraulic drive on the butty for over10 years. I've never had any problems with it and I've changed the oil only once during that time (and that was only because ARS, who are very helpful BTW, said I should do it every ten years.)

The only slight drawback is the high pitched whine, but I've got used to that, and the fact that the blade is a bit like an egg whisk, so it takes a bit of forethought when stopping the boat.

The butty weighs, I guess, 25 tons and is powered by a bog-standard 1.8 BMC. It goes like the clappers and, I regret to say, I can't keep up with it in Owl with its Kelvin K2.

[Whitewater]

I spent 8 weeks on a friends boat with hydraulic drive on it. It drove a RN2, it was great, twice it saved me from searing the prop shaft when I got a sleeping bag and then a large log around the prop. Esp after i heard the story of a new build that had some thing wrapped around the prop. It sheared the prop shaft and also lifted the engine of its bearers. It cost thousands to repair, a lot more than the hydraulic drive....

[ditchcrawler]

I spent 8 weeks on a friends boat with hydraulic drive on it. It drove a RN2, it was great, twice it saved me from searing the prop shaft when I got a sleeping bag and then a large log around the prop. Esp after i heard the story of a new build that had some thing wrapped around the prop. It sheared the prop shaft and also lifted the engine of its bearers. It cost thousands to repair, a lot more than the hydraulic drive....

On two occasions I have ended up with a lump of wood jammed between the tip of a blade and the bottom of the boat. This just resulted was just the relief valve lifting and then spending half an hour with the mooring hammer driving the wood out.

[DHutch]

The owner of one of the newer steam narrowboats on the system had a previous boat (also built by him) the used a marinised transit engine, second hand pump, and a motor from a cement mixer.

- He said it was great, and if nothing else, allowed the enigne to be mounted on what would be considered very soft mounts within the canal industry.

 

He is also runs a crane mechanic and service company, so is clearly very familuar with hydrolic systems, and was able to lay his hands on a range of parts needed very cheaply.

 

 

 

Daniel

[Arnot]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

 

Biggles

I am just putting another couple of hydrostatic drive systems, one on a tug and one on an ex working boat. Both have vintage diesels.

 

Both are closed loop variable swashplate systems with radial piston motors but this is not the only way of doing it, just the most effective for propeller drive. If you anticipate using a hydrostatic system to allow the power of the main engine to be used for bow thrusters or a mains generator you cant use this sort of system, you will have to use open loop which is an order of magnitude more complex, more expensive and less efficient.

 

The benefits and drawbacks of closed loop hydrostatic drive are more or less as Tony describes but really come into their own with the vintage diesels.

 

Essentially the torque demand curve of a propeller is exponential, i.e. as the speed doubles, the torque demand quadruples. The torque output curve on a vintage diesel however is a completely different profile with the peak torqe occurring at about half maximum revs and sometimes even lower than that. The consequence is that with a fixed ratio drive you either use the power of the engine at medium speed effectively and accept that if you try to give it full throttle is will just black smoke - or - you gear it to allow maximum speed and accept that you are only using about 25% of its capability at low to medium speed.

 

A closed loop hydrostatic drive with a variable swash plate pump allows the drive ratio to be varied to achieve both effective low and mid power usage and at the same time be able to use maximum revs when required.

 

I don't entirely agree with Tony on the fuel efficiency thing though when using a vintage diesel. The ability to run the engine at about half the speed or less under normal cruising conditions should save more power than the fluid drive wastes in lower efficiency but this will vary with the engine and the running speed/load.

 

Don't however get the impression that this is a simple engineering solution or a cheap one. The complexities, calculations and techniques necessary to design and construct an efficient and reliable hydrostatic drive are difficult and expensive.

 

I guess that my take would be that if you intend using a modern engine then unless you have some unusual usage in mind, hydrostatic drive would not be particularly beneficial and definitley not be commercialy viable. If you have a vintage engine and/or an unusual commercial usage in mind then it is worth a look. The problem is finding someone who understands the application of hydrostatic drive to narrow boats.

 

It has been mentioned that one problem is the fluid overheating. This is (as postulated) usually down to the design of the pipework, it is important to make sure that the flow velocities are kept low and that the fluid has to negotiate no sudden changes in direction such as in valves, unions and sharp pipe bends. Of course if regular hard work is anticipated then a keel cooler for the hydrostatic fluid can easily cure this.

 

It has also been mentioned that such systems can be mechanically noisy. Again this can be minimised to the extent of inaudability with careful design and construction. It is essential that the complete system is acoustically decoupled from the hull and the engine, any hard connection (including the pipework) to the hull will transmit the noise that is an inevitable function of piston pumps and motors. Also mounting brackets may require the application of acoustic damping.

 

Hope this helps...

 

Regards

 

Arnot

[Biggles]

Hello Everyone

 

Thanks for all the replies so far its a very interesting debate. I am seeing there is more to it than meets the eye.

 

See my blog. I have no problem with putting in a standard shaft drive system, I just thought this might be worth a thourght, and a bit of debate.

 

Keep it comining :-)

 

Biggles

[laser]

Hello

 

Is anyone using hydraulic drive, or have direct experience of it.

 

I am considering it for my build, but would like to hear from users of their opinions comment or experiences.

ve

Biggles hi biggle im a few pages behind the current, but if you are still interested in hydraulic drives Im your man. I will give you a personal view on my take on the subject. Im now fitiing out my second boat with hydraulic drives ,my last boat was a 50ft J Wilson shell my home waters was the Trent and Soar rivers I had it for 17 years , and being an engineer with hydraulic skills ,and being new to boating I had no pre conceived ideas on what drive system to use I considerd the cost of both and found that I could fit two thrusters bow and stern with the hydraulic system at a affordable price providing I purchase all my gear thru normal channels not the marine companies . In 17 years of extensive cruiseing I have had two engines ,firstly a BMC 1.5,for 10 years and then a Ford 1.6 but the hydraulic system was still as good and reliable as from new, the reason being industrial hydraulics are designed and made to run on load for thousand of hours with normal oil and filter changes. Seventeen years of pushing my boat forward and backward,side to side merrits about 10% of what this stuff can do ,no doubt it will go on for another 17.a few technical details , the main drive motor a 30 HP Danfoss wheel motor I chose this because it has a massive thrust bearing supporting the 40mm shaft on which a 20 X 20 prop is fitted no alignment problems here. A very efficient 3 to 1 ratio ,with the the rev counter and pressure gauge readings taken ,and doing 7MPH up the Tent towards Sawley locks acouple of years ago I calculated that this motors output was just 12HP. My new boat ,58ft has a 22 HP wheel motor this is fitted half in and half out of the stern doing away with the prop shaft ,and stern gland but acting as an oil cooler since the motor can not get much hotter than the canal the half inside the stern is connected to the oil supply The bow and stern thrusters for my new boat are just danfoss 95mm dia 1500 RPM 7HP small enough to fit into the 12inch dia tube these should have ample thrust for hovering when Im singlehanderling .Cost of hydraulic estermated about 2 to 2.5K

.

[Biggles]

Having just come back form the Crick show I am again enthused by Hydraulic Drive.

 

Have a gander at this thread. Has anyone anything to add?

 

Biggles

[WotEver]

Having just come back form the Crick show I am again enthused by Hydraulic Drive.

Did you see the rather nice boat with the disabled buggy on the front? That had bow and stern hydraulic thrusters and the owner was really enthusing about them (and the builder, who built the whole boat by remote via email from the States).

 

Tony