Home made hydraulic tranny

Discussion in 'Boatbuilding' started by stimulak, Jul 30, 2003.

  1. stimulak
    Joined: Jul 2003
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    Location: Panama City, Florida

    stimulak New Member

    Any tips on a self made hydraulic transmission? It's mentioned as a viable alternative in both George Buehler and Reaul Parkers books. Seems easy to self service and able to locate the engine advantageously. We are building on the cheap and have a nice Isuzu truck engine that might live long if run at a constant RPM. Our boat is very light displacement (a motor sharpie so to speak). Any experiences in this area? Best wishes from the gulf coast. BG
     
  2. gonzo
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    gonzo Senior Member

    Hydraulic systems are rather heavy and inefficient. Unless you spend a lot of money consider a 30% loss of power as average. Also, the high pressures of a hydraulic system are very dangerous. At 2500 psi, hydraulic fluid can kill you. I don't know why do they consider it a viable alternative. They should include designs with specifications if they are serious about it. Also, truck engines are not well suited for marine use. The torque curve is wrong, electrical systems are not shielded, the gaskets are not stainless or other marine grade material and it doesn't have a appropiate cooling system.
     
  3. Guest

    Guest Guest

    Hydraulic tranny

    There are tonnes of resources for doing this, but what do you want to achieve? why are you doing this as opposed to buying something off the rack or from a scrap dealer? Just for fun or what?
     
  4. betelgeuserdude
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    betelgeuserdude Junior Member

    There's a whole lot of ways to skin a cat. I've met several people with hydraulic drive systems. When you get past the noise, heat, and inefficiency problems, the benefits become apparent. One engine can run at optimum RPM and fully power propulsion, thruster, generator, watermaker, refer, freezer, windlass, dive compressor.... and all by means of hydraulics. Engine alignment isn't an issue, in fact, the engine can be mounted off CL, transversely, etc. One engine can power multiple shafts, such as aboard a catamaran. Shaft angle can be optimal, without regard to the engine.

    Folks have been using truck engines for years and years. Most diesels on the market are marketed to anyone who will buy them. There's taxi engines (Westerbeke), tractor engines (Kubotas, Yanmars, Deeres, Caterpillers) , truck engines (Detroit, Cummins, Izuzu, Ford), even car engines (VW, Mercedes). Sabb is well and truly designed for marine applications. As a matter of fact, the engine that I have in my old GMC Jimmy is more popular on boats than in vehicles. Improved cooling and constant RPM are a few of the reasons. It naturally goes without saying, any engine must be marinized with cooling, electrical, aspiration, and fuel considerations.

    I recommend learning about hydraulics first. Check with the local community college, and pick up a Grainger catalog. As mentioned, there are some negative aspects, but it is a solution worthy of consideration if one is so bent. Even if you decide to go the route of society's comfort, you will have learned something valuable.

    Oh, and by the way, it's not a "tranny" per say. The system consists of a an engine mounted hydraulic pump, coupled to a motor(s).

    DC
     
  5. gonzo
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    gonzo Senior Member

    Engines, even though they share a block, don't readily transfer from one application to another. Automotive engines have a torque curve that peaks at high RPM's. Marine engines have a torque curve that starts much lower. Generator and pump engines are designed to run at a narrow range of RPM's. Camshafts, injection pumps, injectors and other components are set up differently. It is possible to sort of, kind off, somewhat make them work, but inefficiently and sometimes dangerously. All those hydraulic accesories can be driven from a pto in a standard marine engine.
     
  6. betelgeuserdude
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    betelgeuserdude Junior Member

    No disrespect Gonzo, people have been shoveling engines of all types into boats since there have first been engines. The real world is out there. A stroll down the commercial docks could be instructive to all recreational boaters. :)

    The marine environment is dangerous. We must take the precautions to discover the degree of safety to which we individually feel comfortable. This applies to all systems, not merely hydraulics.

    I have never owned a hydraulic system as I've described. All of my marine diesels have turned a shaft. The people whom I have known to possess such a system seemed to be normal and functioning human beings.

    Whether you believe a hydraulic system to be inferior or not, others have found it to be the perfect solution to their needs.

    I would not encourage anyone to arbitrarily choose a hydraulic system, but neither would I flatly refute the possibility. In some situations, a hydraulic system is perfect, in a typical production monohull scenario, why bother? As you have stated, a combination of both a typical shaft drive and hydraulic accessories may be best. Can a hydraulic system be disappointing? Of course! Progress is not always measured by success.

    For anyone interested in unconventional solutions, I encourage extensive research. Specific, objective, informed criticism is incredibly valuable.

    The world now has canting keels, canting rigs, unstayed Open 60's, hydrofoils, Z drives, full automation, etc, etc... ALL UNCONVENTIONAL. You can bet that there was an initial interest followed by immediate scepticism in all of these solutions. Yet, they are here to stay. Would you fit a Catalina 30' with a canting keel? What about foils under a Bayliner? Of course not. The fact that there are infrequent applications for unconventional systems shouldn't take away from the solution in general.

    Millions of ways to skin a cat.

    DC
     
  7. gonzo
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    gonzo Senior Member

    I agree with most of your comments. What I tried to make clear is that an improper installation can be a waste of money. I've seen all kinds of unusual adaptations that sort of work. I've also seen some that didn't. Working as a surveyor investigating marine accidents made me aware of many of those which didn't work. In some cases people got hurt or killed. Hydraulics are more dangerous than a mechanical transmission. A fluid leak can kill or cripple you. At such high pressures fluid will enter the blood stream and cut the skin too. What I question the most, is that if designers claim it is a viable alternative, why don't they show a design with specifications? I believe it is irresponsible from them not to warn of the dangers of home design.
     
  8. betelgeuserdude
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    betelgeuserdude Junior Member

    Your point is well taken. That said, I have never seen a schematic for an LPG installation, a CNG installation, watermaker installations, electrics, or even a gasoline supply line installation.

    What about designs specifically drawn for steam engines? I've never seen a design which details the construction and installation of the engine, just the boat around it. Is this wrong? Hasn't the designer limited his liability by leaving the fabrication and installation up to the builder/owner? I suspect that even if the designer specified an entire system, the fickle owner or builder would have the nerve to substitute at will. Who trusts the designer anymore? :(

    I say that if Stimulak is truly interested in the possibility of a hydraulic drive system, he would do well to educate himself. Presumably, this will encompass the dangers of hydraulics, the fabrication of systems, and the proper maintenence. He would learn that hydraulics in general are quite fascinating. I also suggested a Grainger catalog because the prices of all of the necessary parts and pieces can intimidate one into submission.

    Seek out other boats with extensive hydraulics. Commercial fishing boats are a great place to start. Speak with the captains of these boats. Ask questions. Who designed the system? Likely the man in front of you. Any deaths yet, due to a catastrophic hydraulic failure? What precautions are taken? Why use hydraulics at all? What kind of maintenence is performed; what intervals?

    The exploration of ideas is incredibly valuable.

    DC
     
  9. gonzo
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    gonzo Senior Member

    There are schematics for LPG , CNG, watermakers, etc. They come with the equipment from the factory or they are specified by the designer. It is true that by not specifying something a designer limits his liability. Sadly, it is usually an indication of the inadequacy of the designer. Call any reputable designer--S&S, Frers, Farr, Bruce Roberts-- and they will have complete designs with their signature. The rest are amateurs or shysters.
     
  10. betelgeuserdude
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    betelgeuserdude Junior Member

    Gonzo, I'm sure that you must be kidding. Your assertion that "the rest are amateurs or shysters" is quite offensive.

    Perhaps you are merely naive.

    Good luck to you.

    DC
     
  11. gonzo
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    gonzo Senior Member

    I am not nauve or joking. A proper designer will include the specifications and construction details. Anyone can produce a set of lines without structural, construction and displacement calculations. What is offensive is a large group of people who call themselves boat designers, shipwrights, surveyors, etc. and don't have the expertise to back their claims.
     
  12. yipster
    Joined: Oct 2002
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    yipster designer

    nahhh,
    i was hoping i could learn something here on hydrolics.
    ok ok, power loss by oil friction, dangerous pressures etc. still, why do i prefer a hydro jack, dont cars use brake cables anymore etc?
    hope the thread gets back to the tittle,
    yipster
     
  13. gonzo
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    gonzo Senior Member

    Getting back on track. The power loss of hydraulics plus the extra weight make them useful only in heavy displacement boats. Trawlers and tugs benefit from the advantages of hydraulics. For example, they can be overloaded and the pressure relief valve will pop open preventing any damage. Another plus is that hydraulic fluid lines can be conveniently and economically routed to wherever power is needed. Also, there is a variety of servos that cover many applications: from rams with inline movement to rotary motors.
     
  14. danmarine
    Joined: May 2004
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    danmarine Junior Member

    Hydraulic drive calculations..?

    Hi Guys,

    I am seeking information on the practicality of hydraulic drive systems.

    The advantages for multi-hulls and general watercraft are fairly obvious and promoted by hydraulic pump/motor manufacturers. For me the best features would be the engine alignment and running multiple pumps off one central power source, with the option of using hydraulics on dagger-boards or a swinging keel arrangement.

    Obviously the feasibility of this drive system relies as much on my vessels configuration as the hydraulics applied to it, so I am not expecting a yes or no answer.

    Some of the downsides have been pointed out by Mr Gonzo and have been a good reality check to compete with the imagination.

    I would like to ask if there are any specific calculations available to enable an informed working design. I have found all sorts of equipment on the globalspec website (yes, I know its for industrial use, but the concepts are applicable, and probably available marinized if you know what your looking for). I am missing information on the calculated power loss of different applications (rams, motors, controls) and hose runs. Also any first hand experiences with the real applications such as reservoirs, variable/fixed output motors and compatible engines would be very much appreciated.

    Thanks,
    Dan
     

  15. gonzo
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    gonzo Senior Member

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