Can a Direct Link Between Car Engine and Jet Pump Power an Amphibious Vehicle?

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Discussion Overview

The discussion revolves around the feasibility of converting a car into an amphibious vehicle by linking its engine to a jet pump for water propulsion. Participants explore mechanical design considerations, power requirements, and structural modifications necessary for such a conversion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes using a sprocket/gear attached to the crankshaft of the car's engine to drive a hydraulic pump, which would then power a jet ski impeller assembly.
  • Another participant questions how the car will float, highlighting that cars are not designed to be watertight.
  • Concerns are raised about the need for a clutch in the marine drive system to prevent constant engagement when the land drive is active.
  • Some participants suggest that the weight and inefficiency of hydraulic systems may be problematic, proposing alternatives like a second motor directly connected to the jet pump.
  • Discussions include the necessary RPM for the jet pump, with estimates suggesting around 5000 RPM for a 6" jet ski pump designed for 50 to 60 hp.
  • Participants express skepticism about the structural integrity of the car when modified for buoyancy and the challenges of sealing it against water ingress.
  • One participant mentions using materials like urethane-based plastic spray and foam for buoyancy and structural support.
  • Concerns are raised about the potential for the vehicle to be unstable or roll over in water, with references to existing amphibious vehicles and their design challenges.
  • There is a discussion about the necessity of a boating license depending on local laws for operating such a vehicle in water.

Areas of Agreement / Disagreement

Participants express a range of opinions on the feasibility of the proposed design, with no consensus reached on the best approach or the practicality of the modifications. Multiple competing views on the use of hydraulic systems versus direct drive motors are evident.

Contextual Notes

Participants highlight various assumptions regarding buoyancy, structural integrity, and the efficiency of different propulsion systems. The discussion reflects uncertainty about the necessary power and RPM requirements for the jet pump, as well as the implications of using hydraulic systems.

Who May Find This Useful

Individuals interested in vehicle modifications, amphibious vehicle design, mechanical engineering, and those exploring unconventional propulsion systems may find this discussion relevant.

  • #31
Well if you do intend to chop the top off so you can use welded doors and drop some weight, and still want to drive this vehicle on the road, I must insist a roll cage be installed. Removing the roof lowers the structural integrity of the safety bubble designed into unibodies.
 
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  • #32
Modern alternators/generators as used in hybrid cars are much smaller and lighter than they were in the past. The problem with these are not size or weight but complexity and cost.

The clutch off an AC compressor can not handle anywhere near the power you will need. You may want to consider a simple mechanical dog clutch. This is the common way forward and reverse are engaged in boats.
 
  • #33
Going back to basics, instead of connecting your engine crankshaft to an hydraulic pump or generator, you could link it directly to the jet pump.

All you need is a mechanism to lower the jet pump when you're in water, some sort of clutch to engage it, put the car in neutral and you're in for a great boat ride! I don't think that the fact that the jet pump is under the boat instead of being behind it will make that much of a difference on thrust power. Worst case scenario, you could have two of them coming out on each side.
 

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