Hydraulic Propulsion

The Queen of the West is a 230 foot cruise vessel propelled by a sternwheel. The sternwheel is powered by a hydraulic motor. In 2008 the Queen of the West had a major engine room fire which originated with a hydraulic fluid leak. http://www.ntsb.gov/investigations/summary/MAR0904.htm

The possibility of a hydraulic fluid leak and resulting fire risk should be considered by anyone contemplating hydraulic propulsion.

 

But given gasoline as an alternative to hydraulic fluid, which do you think would be more of a fire hazard?

That NTSB evaluation points to one thing... wet exhaust is a requirement with a hydraulic pump in the same engine room. Good post.

 

Gasoline is a source of energy, as is diesel fuel. Hydraulic fluid itself is not a source of energy. Power generated from another source of energy, such as gasoline or diesel fuel, can be moved to another a location by a hydraulic system, a shaft, a belt, etc.

Hydraulic systems typically have hydraulic fluid under high pressure and if a lead develops the many hydraulic fluids can atomize into a combustible mix. If there is an ignition source present, either an open flame or a sufficiently hot surface a fire can result. My impression, perhaps incorrect, is that some hydraulic systems built from components with fabricated hoses and tubes tend to be prone to leaks.

Not a reason to not use a hydraulic system if it makes sense for other reasons. Just a failure mode and potential consequences to be considered.

 

one danger is oil sprayed from a presureized plumbing leak onto a hot engine exhaust... Or a complete lose of hydraulic oil would rapidly cause the pump to melt down. I would say the Hydraulic PTO and its plumbing set up is the most dangerous part of my engine room. Even with oil temp and level alarms I worry.

I wouldnt consider a hydrualic system because of the high maintenece. Suction and return line filters, PTO couplings, chafe on flex hose, valve block maintenece,oil coolers, variable controlers....many pieces in the system

 

I'm sorry. I had mixed the two threads up, so my post makes little sense here.

I am personally looking into these hydraulic systems as a replacement for gasoline powered outboards and generator. Hydraulic would allow custom hydraulic "outboards" and allow me to run the boat off diesel.

Otherwise, it has to run off gasoline since there are no diesel outboards.

I enjoy your posts because they tend to make me think.

Failure mode is a good topic. Given gasoline powered outboard and generator, I would be quite vigilant as to fumes and other issues that can easily crop up. Given a hydraulic system, an "if it ain't broke, don't fix it" mentality seems like it would be more common.

Gasoline could actually be less of a fire hazard than a leaky or atomizing hydraulic system due to human factors.

Good post.

 

Cost / risk / weight analysis comes to mind.

-Tom

 

Nothing is perfect, got to run some hydraulic lines from engine room to thruster room and I haven't figured out best way to do it. It is about 40 feet both ways. Should tank be next to bow thruster or pump in engine room? What material should it use for long run hoses? I plan to add stern thruster later, do I need another tank? Boat came with Hydraulic thruster just the never finished installing it.

 

I second that--nothing is perfect--everything in boat design -including propulsion is a trade-off. what attracts me to hydraulics is the quick response of the instant reversing engines...perhaps a good gearbox can do this too but i just like the easy system to reverse and to use two props from one engine-- it eliminates the redundancy of two diesel engines... i dont find the system all that complicated on paper--if i go with hydraulics, i bet the maintenance would be balanced out to that of two engines. but i just like them...spool valves are great and very responsive.


***Micheal- what are you running with your hydraulics?..what size engines?
set-up?....just curious...you seem to have practical experience with them...as mine is solely in the planning stages...and what ive gotten from guys in the field and through the suppliers info etc...
i want to run two engines either 2 x 12 hp x585 rpm motors or two 6.2 cu in 31 hp x 720 rpm motors. one reason i like two hydraulics is it allows me to run two smaller props under my hull rather than one large one which isnt really practical on a small flat bottomed tug...two smaller dia. props makes sense...at least to me...

 

In vicinity of pump.

Metallic piping normally preferred for long runs. Usually stainless steel for yacht instalations.

Don't need another tank unless the original one is too small.

Your supplier of the hydraulics parts should be able to advise you on these matters.

 

Looks like another variation on the axial piston design. It appears that this one avoids the use of 'slippers' on the pistons by allowing the pistons to 'wobble' in the cylinders. Scanning quickly through the patent documents it looks like they do this by making the pistons with a spherical rather than cyclindrical surface, or making the pistons as thin discs, perhaps combined with non-cylindrical cylinders for some of their design options. I suppose this could be done with a normal reciprocating engine - i.e. if you make the piston as a ball that is a close fit in the cylinder you dont need the 'little end' joint on the connecting rod. What's the advantages/disadvantages? - No viscous friction losses due to slippers sliding on a swash plate - Somewhat simpler construction - potentially more leakage between pistons and cylinders? Such leakage is one of the energy losses in hydraulic pumps and motors.

I dont think they give efficiency data on their website. If the efficiency compares well with current axial piston designs then this could be a winner, otherwise its probably not going to catch on for high power transmission applications but maybe could still be used for applications where efficiency is of secondary importance, eg a pressure washer.

 

I still want to see a 53' vessel going 54m.p.h!

 

It is nice that somebody read my patent.
True is that the spherical pistons allow a little more leakage, but the efficiency is in the same range as oil-motors.
There are test data from independent Corporations:
http://www.wolfhartindustries.com/tests.htm
The efficiency increases with the speed and is at 4000rpm by 77%.
Bigger motors have also a higher efficiency.
Inventing a hydraulic motor for water the highest priority must have the eliminating of friction.
To see this is complicated, but the result is clear. This motor runs already with the pressure of a normal water system in your house. Try this with any other hydraulic motor.
(If you wish I could make a short video of it.)
Higher pressure will not increase the friction, because every sliding part is hydraulically balanced and there are no piston forces any more to deal with.
You have all the advantages of the oil hydraulic, but if you loose some fluid you fill it up with the water you are swimming in. You get motor and pump with the same principle. The pump runs with the speed of your engine and can even change the speed of the propeller regardless of the speed of your engine. What do you want more?
Perhaps this: The ceramic rotor allows even to take some foreign particles like sand without damage. The wobbling motion of the pistons is good to get rid of any particle between piston and cylinder. It is a very robust and long-live design. And if some damage occurs, a piston – what is a screw - can be changed in less then 5 minutes.

 

Thanks for re-joining the conversation John. I knew we could expect some intelligent replies from you.

Regrettably at the moment I'm in Thailand looking thru a couple of boatbuilding operations, so I can't spend much time on the subject at the right now.