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Hydraulic driven boat car

  1. Nov 13, 2014 #1
    So her is my predicament. I plan to convert my car to a amphibious car. Don't be negative and judgemental about it but I need help to figure out how I should power it on water.

    I have a 1400 lbs car. It has a 67hp engine. What I'm thinking I want to do is have a sprocket/gear attached to my crank shaft of my engine. In which I will have a hydraulic pump being chain driven from that spricket. In which two lines will be run back to where I want to take the impeller jet assembly off a jet ski. Where it will also be chain driven to adjust torque and rpm as need.

    I think that cover the jest of it. But what I need to know is how fast does jet ski assembly need to turn. What size hydraulic pump and motor will I need? Does my idea seem scientifically plausible the way I have thought of it?
  2. jcsd
  3. Nov 13, 2014 #2
    Ignore my crappy typo and grammar please. I'm a grease monkey with an idea. The rest of the calculations and stuff isn't my thing. I would do it through trial and error. But I don't have the funding...
  4. Nov 13, 2014 #3


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    Before you get into the mechanicals, how are you going to make your car float?

    Unlike the VW in this ad parody, cars are not known for being watertight:

    http://www.threesistersnovel.com/wp-content/uploads/2013/06/Tedkennedyvw1.jpg ​
  5. Nov 13, 2014 #4
    I have that part planned aready. It's acactually rather simple. Cars may not be water tight.. but in a relative way of looking at it. If you take off the roof. You have what would mildly resemble a boat. With tires. If you set that boat with tires in water. It will clearly sink. But is the water going to collapse it? Nope. It will come through holes in the floor. And the sides. And the corners. And miscellaneous locations. So its quite simply, a holy boat (;
  6. Nov 13, 2014 #5
    I just read under that picture (; rather interesting!
  7. Nov 14, 2014 #6
    The problem I see with the set up you propose is that the marine drive will be running all the time that the land drive is running, I think you need some kind of clutch in the marine drive.
  8. Nov 14, 2014 #7
    I figured I would be able to do something like on a actually compressor. With that but in clutch type deal. I just dont now how big of a pump I can run. And how big of a pump I will need. Or if what I'm thinking will even turn the marine drive portion fast enough.
  9. Nov 14, 2014 #8


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    And it will stay afloat how exactly?
  10. Nov 15, 2014 #9


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    Spoilsport! I was going to ease him into that by asking how he was going to keep his electrical system from shorting out... :p
  11. Nov 15, 2014 #10
    eurathan based plastic spray will be coated on the bottom 1/8 to 1/4 inch thick. Will be using the foam that is used in boats to stick top of that. And it will be shaved how seen fit. That no top of that will be fiberglass. Will have a sealed removable panel under the engine bay. Also the bump will be replaced with a square pontoon looking float. To hold engine weight. Better. For the cv axle they are gonna be tricky. Will sermon them when I get to it cause they move in every direction with bumps. I have a general idea but not for sure yet
  12. Nov 15, 2014 #11


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    Is it for fresh water only? If you use it in a marine environment, how will you remove the chloride ions from any exposed steel, (such as the suspension), after it has been baptised?
  13. Nov 15, 2014 #12
    I live in northern minnesota. Whats salt water?
  14. Nov 15, 2014 #13


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    So, now you mention sealing. Before, you said that it would leak through multiple locations and would indeed be a "holy boat".
    One thing still puzzles me immensely: what the hell kind of car has a 67hp engine?! That's barely more than a decent chainsaw.
    Anyhow, I'd recommend going with a belt drive rather than chains, simply because you don't need precision, it would be a lot quieter, and you wouldn't have to worry about lubrication or corrosion issues like you would with metal.
    Also, depending upon local laws, you might need to obtain a boating license in order to legally put it in the water.
  15. Nov 16, 2014 #14
    Hydraulics are heavy and inefficient. Assuming you want to transfer a fair amount of the 67 hp and you are using utility type equipment your hydraulic system will most likely be well over 200 lbs. For this same weight and about the same cost you could have a second motor directly connected to the jet pump. Another choice would be to use an electric system from a hybrid car but this will be only a little lighter and more expensive. A drive shaft may be a better choice if possible.

    Most of the 6" jet ski pumps were originally designed for about 50 to 60 hp. Of course as time went on they kept increasing the power and pitch and area on the impeller. For about 60 hp a 6" jet pump should turn about 5000 rpm. More pitch and area on the impeller will make for a lower rpm at this same power.
  16. Nov 16, 2014 #15


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    Yes, you;re gonig to have a heckuva time balancing weight.

    And keeping it from rolling. It may actually be too buoyant to be stable, and may go turtle on you.

    Look how low in the water this amphicar needs to be so it doesn't flip.

    BTW, how will you seal big seams like the doors. Lot of pressure there. These amphicars leak like a sieve.

  17. Nov 16, 2014 #16

    jack action

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    To size the pump and motor, you first need to know how much power you need to do what you want. Interesting links:
    For the speed of a jet ski assembly, this motor with jet drive develops its 80 hp at 5500 rpm and it's a direct drive. There is also a «conversion guide» that seems to suggest you need less power with a jet pump than with a prop shaft. I suppose it is because there are no transmission losses since it is direct drive.

    [/PLAIN] [Broken]
    Last edited by a moderator: May 7, 2017
  18. Nov 16, 2014 #17
    I work on ch-47 chinooks for the army. Which is 90% hydraulics. And you are the first person I have ever heard say hydraulics are heavy and inefficient. Could you explain your reasoning behind that? Also that you very much a had no clue what rpm the jet pump would need to spin.
    Hybrid is out of the picture because I don't feel save with all that electricity... on a water source lol. And I thought about the 2nd engine but I'm doing this work on a 1993 ford festiva. And I want to be able to have 4 seats.
  19. Nov 16, 2014 #18
    I thought about belt drive but belts slip? And that would be loss of power? Yes I will neneed a boat license on it which is 37 dollars. A 1993 ford festiva wI'll be my car of choice
  20. Nov 16, 2014 #19
    I figured I would conquer weight and balancing when it arose. I was thing extendable arms on each side with floats on them like some sail boats I believe it is has. And for doors.... ohh doors. If necessary I will weld the majority of the door shut and make it custom. If i can, what I want to do is look aat the 1990s cj3 jeeps. Which have sealed cabs. I wold borrow some ideas. Also I was thinking. A dam good seal on the door and then a lever that will suck the door in tight against the jam.
  21. Nov 16, 2014 #20
    So do you by chance have a general idea of what I would need and where I could locate such materials. 70hp engine (1395cc) and it will be a jet ski assembly so it will be at 5000-5500 rpm. And I will not be attaining jet ski speeds at all. I would be happy with 15 to 20 mph. Pushing it. Don't Wana risk flipping too much.
    Last edited by a moderator: May 7, 2017
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