Hydraulic Propulsion

[Jmarkley]

I'm convinced that it's possible to use hydraulic fluid to turn a prop instead of using a direct mechanical connection. The advantages are less maintenance, less vibration, placement of the engine anywhere on the boat.

Does anyone know of a firm which markets this type of drive system?

[yipster]

read http://www.boatdesign.net/forums/showthread.php?t=1355&highlight=vetus and more using the search button above :cool:

[JR-Shine]

Those drives range from $1,800 to $3,000.

Joel
Boatbuildercentral.com

[FAST FRED]

Most pumps are about 92% efficent , there are cooling,piping & valving losses , then the motor is only about 92% .

Multiplied together your loosing about 25% of your fuel in heating Hyd fluid.

Great if you wish to go from Full foward to Full reverse in an instant , but for cruising?

Most hyd parts have long but limited service life, so will need rebuild , timed about with the engine.

Best use would be for multiple apps , hyd windlass, hyd steering , hyd crane , and very low speed ops. Electric can be made quite stably from hyd , and it can power refrigeration system compressors too.

FAST FRED

[jehardiman]

I'm convinced that it's possible to use hydraulic fluid to turn a prop instead of using a direct mechanical connection. The advantages are less maintenance, less vibration, placement of the engine anywhere on the boat.


Possible yes, practical no.

In my experience, the only advantage of a hydraulic drive is in arrangements, and in this it has only a slight advantage over electric drives due to size of the power head.

They are about half as efficient as a gearbox or electric drive, and about twice as costly to maintain (ICE-gearbox or ICE-GEN-MOTOR vice ICE-HPU-HD). They are about as heavy either a gearbox or GEN-MOTOR, and only provide a reduction in vibration if the right components are selected. Additionally they are very noisy if the wrong components are selected.

All this is based upon design studies to replace existing electric drive systems of 5-250 Hp systems. ICE-GEN-MOTOR is far more suited for for low power application on a boat if arrangements warrant not fitting a gearbox.

The only other reason to fit a hydraulic drive is the very special case of a vessel that needs a huge hydraulic plant to perform its mission, but transits while not working. In this case, there is an argument to be made for saving space by not fitting a prime mover, but using "free" hydraulics.

[woodboat]

The trash boats here in Baltimore inner harbor use hydraulic. They move slowly around the harbor, go from forward to reverse alot and the pump also drives some scoops and a track belt to pull trash up and into the hopper. The drive units look like outboards.

[MikeJohns]

Gives some interesting design options. Can put the engine anywhere and any orientation. The same pump can drive thrusters, winches, Prop. Seems a good auxiliary option for a blue water sailing yacht. As for life and reliability they seem better than the modern cheaper mechanical boxes.
Horrible mess when bleeding the system uness you are careful.

Aside.......I've seen a 70' fishing boat pull itself off a sandbank with a hydraulic capstan winches. Would have burn't out the equiv electric one, first try it ripped the tree right out of the bank!

[John Perry]

Back in the '80s I worked on a big R + D project to develop hydraulic drive for warship propulsion with the hydraulic motor within the propeller hub and power output up to about 40MW. After building and testing expensive prototypes the conclusion was that the power losses would be prohibitive, not just because of the cost of the extra fuel but also the weight of that fuel or alternatively the loss of range. At that time the conventional wisdom was that the propeller hub must not be more than 30% of the propeller diameter and this ruled out an electric system with an electric motor in the propeller hub. Nowerdays such electric systems are the preferred option for many ships, espeicially cruise liners (eg Azipod drive) and I think they do have a larger propeller hub diameter than was considered acceptable at the time of our project.

Cruise ships and warships have a high electrical demand from the 'hotel load' and this usually requires a number of diesel generators to be installed. It is then logical to add a few more similar generators so that the power available is enough to cater for the main propulsion motors giving a flexible system where the number of generators running can vary according to the total load while keeping each generator operating close to its optimum power setting. The efficiency benefit this gives can more than compensate for the losses due to the need to transform mechanical power to electric power and back again.

For ships such as tankers which have small hotel load and which operate mostly at one power setting the most efficient system is still a simple mechanical drive from engine to propeller and with large direct drive reversible diesels the losses due to a reversing gearbox are avoided hence mechanical efficiency is almost 100%.

John

[dereksireci]

I've used a hydraulic power take off pump on the front of an engine to run a water pump on a fire boat. All that fluid can be heavy

[Ilan Voyager]

Hydraulic systems are used on harbour tugs or servitude boats where the inherent losses of hydraulics (and the fuel consumption) do not matter. These boats do not travel, and hydraulics is the solution for the numerous equipment requiring power on these boats.

On boats needing a good range of cruising these losses and very bad total efficiency are unacceptable; any % of efficiency gained has important economics consequencies. We made in 1983 a study for a mines sweeper and this technical option has been abandonned. It was far better to put a propeller with an electric motor on the rudder and start a 250HP gas turbine generator while hunting mines at low speed, the main diesel engine being stopped.

The current engineering trend, as it has been written by Johnn Perry in a former post, is electric; good global efficiency, no problems of reliability (the hydraulic hoses and connections may be problematic), no problems of cooling a fluid running in hoses inside the boat. Or the absolute simplicity; big slow diesel (85 to 120 RPM), no gear box, simple shaft, big slow propeller. The global efficiency is excellent: almost 50% for the engine (to compare a marine gas engine about 25%), no gear box losses, propeller about 85 to 90 %. Very reliable also, it's the choice for tankers, container carriers etc... It handles very well very big powers: the biggest diesel engine gives 110000 HP at 102 RPM.

On a yacht, a semi fast diesel generator and an electric engine would be a good solution. The mixte buses (diesel and electricity) equipment should be a starting point as they have similar requirements and are in the range of power as a small yacht.

I have seen hydraulic transmissions a race sail boats in the 70's, and they were always unreliable and often noisy.

[Lda]

In electric transmission you have two kinds of solutions:
1) Without electronic control (DC generator and engine directly connected...) simple and reliable but heavier than mechanical. Expensive if you use marine grade equipment. Nearly as efficient as mechanical. Ships don't use this solution any more.
2) With electronic control (AC generator and DC or AC-self-piloted motor connected through intelligent "drive" electronics). Light and very efficient. Control electronics is expensive if you want it reliable. For low power systems, electronics might be prohibitely expensive because part of it does not depend from the size of the engines. Might be dificult to maintain in some area. Efficiency is typically better than mechanical because transmission has continuously variable ratios you can optimise depending on actual use.

In hydraulic transmissions you also have two kinds of solutions:
1) closed circuit, piston type pump and motor (classic "earthmover type" technics). Light and #80% efficient. Efficiency can improve if you use variable-displacement or automatically-adjustable pumps, because transmission will have continuously variable ratios (transmission losses remain at #20% but chances are you will more than recover them through better continuous adjustment of propeller rpms). Reliability is good for fixed displacement pumps, lower for variable displacement. Generally rather expensive.
2) Open circuit, gear type pump and motor ("agricultural" or "log-splitter" type technics): cheaper but limited in size due to availability of bigger components (<=#150 hp). Also requires rather cumbersome hydraulic reservoir (about 4 liters oil per transmission hp). Efficiency #80%.

I understand that US is more conservative than Europe for hydraulic solutions although it looks like they are still quite interresting for yachts vs. electrical, depending the needs.

[PADDLEGUY]

An All Hydraulic Drive System Is What I Have Designed For My Twin Sternwheel 28` Week Ender. A 25hp Diesel With Pump, Running Twin Low Speed, High Tourque Hydraulic Motors Bolted Directly To The 6` X 2` Wheels With 8 Buckets Each.. My Hydraulic Engineer Tells Me This Will All Be Fine,, With Just One Problem Remaining.. Keeping Saltwater Out Of The Motors.. Any Ideas, Comments, Advice Will Be Well Taken,, Thanks

[gtsmarine]

for information on drive systems contact Duckworth Steel boats
Tarpon Springs Fl

[gtsmarine]

contact Duckworth Steel boats in Tarpon Springs Fl

[John Perry]

I think that 80% is a bit optimistic for the efficiency of a hydrostatic propulsion drive. A good axial piston pump or motor may manage 90%+ but only under an optimum combination of rpm and torque. You have to add the losses in pump, motor, pipework, plus mechanical losses in shaft seal and bearings. Hard to quote a general figure, it will depend on the operating conditions anyway and also on wear in the pump and motor but I think 60-70% is nearer the mark than 80%. That is a rather large power loss, you also need to dump the heat somehow. A small system based on gear pump/motor can be expected to be rather less efficient than a larger one based on axial piston machines. This is the main reason that hydrostatic transmission has never been much used for ship/boat propulsion.

Many modern ships have electric drive for controllability, fault tolerance, ability to match number of active prime movers to varying power requirment and the ability to supply both propulsion and 'hotel' loads from the same set of generators. But for ships where these aspects are less important, that is ships which run mainly at a steady cruising speed and which dont have large and/or variable hotel loads the preferred and most efficient drive is still a mechanical one, preferably without a gearbox. Large tankers and containerships use a direct drive from a reversible diesel engine to the prop and no alternative transmission is going to beat that for efficiency.

[brian eiland]

...a portion from my website....http://www.runningtideyachts.com/power/
"While working on a new bow thruster design, a Hungarian gentleman has developed and built several entirely new and unique gearless, twin-rotor, angular-piston, hydraulic motors. This patented mechanism employs two rotors which are interconnected by angular pistons that are all contained and bearing mounted in a common housing. The linear displacement of the pistons in one of the rotors is directly converted into the rotational motion of the other rotor, interactively. The geometrical and mechanical relationship between the two interconnected rotors provides optimum conditions for direct conversion of linear displacement of the pistons into rotational displacement of the rotors. Barring frictional losses, the conversion is 100% efficient. None of the commercially available axial piston motors have such direct and efficient means for converting linear displacement into rotational motion."

I was contacted over 6 months ago by a British firm wishing to know more about this design. I believe thay made contact with the patent holder. Don't know the outcome yet.

[John Perry]

Brian

Looking at the pictures on your website the new hydraulic motor referred to would appear to be a 'bent axis' design, I think with pairs of pistons connnected by rigid 90 degree links spaning between the two rotors. As I mentioned above, I was involved at one time in a R+D project on hydraulic motors and this was one of umpteen configurations we considered in the early stages of the project. We found that almost all of the many configurations that we considered had been patented, if not as hydraulic machines then as rotary steam engine possibilites by victorian engineers. I cannot remember whether or not the design with rigid 90 degree links was one for which we found an existing patent but I have definitely seen drawings of the same mechanism used not as a hydraulic machine but as a means of transferring rotational power through an angle from one shaft to another, the linked pistons will do that even without any hydraulic fluid present.

My initial thought regarding the design you refer to, assuming I have interpreted it correctly from the small picture, is that it is potentially a pretty good design but it still suffers from the same power losses which apply to all designs of hydraulic motors, the main ones being viscous friction loss, leakage losses and compressibility losses. I would be surprised if it turns out to be so much more efficient than existing hydraulic machines that it changes the direction of development of ship/boat transmissions. Comparing it with a conventional axial piston machine, which is the 'gold standard' for high efficiency hydraulic machines, it has the advantage that it avoids the frictional losses of the 'slippers' which drive the pistons of a conventional machine in and out of their bores. However this advantage is not as huge as one might imagine, slippers run with surprisingly little friction since they glide on a cushion of high pressure fluid fed from the cylinders, rather like small hovercraft. Against this advantage, the pistons in this design are going to be more heavily loaded sideways against the cylinder bores than in a conventional design.

The design which our R+D project eventually adopted for further development was a rotary vane design with unusual axially moving vanes. This was not my decision and I think it was a mistake, a conventional axial piston pump would have done the job better. In fairness to my bosses there was an externally imposed requirement to keep the diameter of the machine as small as possible and the axial vane design was good that way.

John

[brian eiland]

Hello John,
That is real interesting that you should be so knowledgable about this subject. I will definitely get back to you on this subject. I just happen to be real busy with 4 unrelated projects at the moment

[the yacht shop]

you guys bring up many good points but i can tell you from past experience that a good hydraulic drive setup can be (no, make that is ) just as efficent as a hydraulic transmission such as a paragon or borg warner. I had a westerbeke 4/107 with a paragon in a 40' sail and then changed to the vickers hydraulic pump and motor. fuel consumtion was the same with both units but the vickers was smooooooth and quiet. and it blows the socks off a conventional trans in close quarter docking.

[FAST FRED]

The advantages are many , besides effortless shifting at any engine speed the ability to power a gen set , bow thruster (with out 30 second restrictions ), hoists anchor windlas and even stabelizers is grand.

The problem is efficency as most pumps are at best 92% efficent as are the motors (in the correct operating range) .

The problem is these 2 efficencys multiply , and compare poorly with the 2 or 3% loss in a std mechanical tranny.

One saving is the engine speed under way can be matched to the power required, if the pump has large enough low RPM output.

If fuel consumption is less of a hassel than burning out electric motors in windlasses and thrusters , GO for it!!


FAST FRED

[Dynaset]

Only one petro/diesel engine and hydraulic pumps are enough.
Hydraulic system gives the variable speed control, very fast exchange of the propeller rotation direction without breaking anything, bow thrusters, stabilizers, generator, high pressure bow thruster/washing system and etc.

Your ideas are just the limit.

[Easy Rider]

I'm surprised no one has mentioned Vetus. They offer 100% ready to go hyd systems around 20 to 30 hp.
I wonder if one used a 2-1 to 3-1 gear w a hyd pump on the end of the gear and located the pump and motor very close to each other one would have very low velocity fluid w large dia and fairly short hoses. In my hyd steering system the friction seems to come from cylinders and pumps. If the majority of the friction came from fluid in the hoses rather than pumps and motors this idea would seem to have merit.

Easy

[joseph fasola]

I'm convinced that it's possible to use hydraulic fluid to turn a prop instead of using a direct mechanical connection. The advantages are less maintenance, less vibration, placement of the engine anywhere on the boat.

Does anyone know of a firm which markets this type of drive system?

YES I DO YOU NEED TO SEE PLAN AND VESSEL .I'm in the patent process need a parnter let's talk 205-504-9416

[joseph fasola]

I'm convinced that it's possible to use hydraulic fluid to turn a prop instead of using a direct mechanical connection. The advantages are less maintenance, less vibration, placement of the engine anywhere on the boat.

Does anyone know of a firm which markets this type of drive system?

yes , need someone not afraid to go out there in the water where nobody else has gone call me at 205-594-9416 emIL ME AT onicefishing@att.net are visit my web site at www.reeldealpolecaddys.com click about us you would not believe what I've done 53' vessel 54m.p.h 3800 mile range on 400 gals of diesel propane is off the chart and your right no maintenance sealed unit, no vibration, and take up 80% less room in engine space and it's green propulsion no emissions in water

[brian eiland]

.... or visit my web site at www.reeldealpolecaddys.com click about us you would not believe what I've done 53' vessel 54m.p.h 3800 mile range on 400 gals of diesel propane is off the chart and your right no maintenance sealed unit, no vibration, and take up 80% less room in engine space and it's green propulsion no emissions in water

Your website reference could not be accessed??
Brian

[gonzo]

The website sells fishing rod holders. Joseph: can you provide any evidence of you claims? No vibration, for example, is a good sales pitch but an engineering impossibility. No emissions in water is another claim that is not possible.

[FAST FRED]

"you would not believe what I've done 53' vessel 54m.p.h 3800 mile range on 400 gals of diesel propane is off the chart and your right no maintenance sealed unit, no vibration, and take up 80% less room in engine space and it's green propulsion no emissions in water"

Yes it is unbelievable , so how about posting an article on your method of operating?

Details , photos and logs?

[tugboat]

http://www.youtube.com/watch?v=-cWoy2IjP0Y&feature=plcp&context=C34810baUDOEgsToPDskLED7TPBXpjjaS4ZRwHAkGQ

they work great ---watch all this guys vids...im doing this on my tug--engine to pumps to two drive units...might be a little extra fuel but it has advantages i really lik e such as on a tug-instant reverse and the motors i want are continuous duty,...two props beats one for maneuverability and i can use two cheaper common props...

i like your idea ...let me know how it works...

[tugboat]

I'm surprised no one has mentioned Vetus. They offer 100% ready to go hyd systems around 20 to 30 hp.
I wonder if one used a 2-1 to 3-1 gear w a hyd pump on the end of the gear and located the pump and motor very close to each other one would have very low velocity fluid w large dia and fairly short hoses. In my hyd steering system the friction seems to come from cylinders and pumps. If the majority of the friction came from fluid in the hoses rather than pumps and motors this idea would seem to have merit.

Easy

i agree with you easy rider--i corresponded with someonme off here- who used the same setup i plan--i think he even coolled the motors by running them under water..in this vid the hydraulic motors are just standard cooled with oil reservoirs...

http://www.youtube.com/watch?v=-cWoy2IjP0Y&feature=plcp&context=C34810baUDOEgsToPDskLED7TPBXpjjaS4ZRwHAkGQ