Hydraulic drive system?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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fishonhenson
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Hydraulic drive system?

Post by fishonhenson » Sat Jul 18, 2015 12:17 pm

Has anyone ever thought or tried to make hydraulic drive system for an airboat prop? most heavy equipment uses it, why wouldn't it work for a boat?

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mojoe
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Re: Hydraulic drive system?

Post by mojoe » Sat Jul 18, 2015 2:18 pm

Hydraulic steering would work. Expensive and complicated, but it would work. How would a hydraulic driven prop work? What would the benefit be?
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fishonhenson
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Re: Hydraulic drive system?

Post by fishonhenson » Sat Jul 18, 2015 3:17 pm

you can place the engine anywhere you like for torq to raise the bow. the engine can sit on the bottom of the boat for a lower center of gravity. a hydraulic pump is close to 100% efficient. you can actually reverse the prop motor to back up if needed. they are fairly light weight now. hoses go from the engine pump to the hydraulic motor which is small. it should work.

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Re: Hydraulic drive system?

Post by fishonhenson » Sat Jul 18, 2015 3:21 pm

A hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to power hydraulic machinery. The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow.

A hydraulic drive system consists of three parts: The generator (e.g. a hydraulic pump), driven by an electric motor, a combustion engine or a windmill; valves, filters, piping etc. (to guide and control the system); and the actuator (e.g. a hydraulic motor or hydraulic cylinder) to drive the machinery.

Afflicted
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Re: Hydraulic drive system?

Post by Afflicted » Sat Jul 18, 2015 7:59 pm

It'll work pretty easy but wouldn't have the response needed for an airboat. It would be dangerous and sluggish I think
A guy a while back made a pusher fan for bowfishing that was hydraulic. But that's no airboat
Your throttle wouldn't control the engine. It would control the hydraulic motor that can't respond like a crank shaft
There are hydraulic things that spin really fast but it takes a little bit for them to get up to speed.
If hydraulics r under a load they slow down. To get a hydraulic motor with the balls to spin up a prop with a decent amount pitch but not load the motor down to much, the motor would have to take a minute to get up to speed.

I may be totally wrong but that's my opinion

fishonhenson
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Re: Hydraulic drive system?

Post by fishonhenson » Sat Jul 18, 2015 8:07 pm

Variable pitch prop

Afflicted
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Re: Hydraulic drive system?

Post by Afflicted » Sat Jul 18, 2015 8:27 pm

Getting too complicated and expensive if u gotta go that far to achieve what u want. In the end u could have just boat a nice boat.. But I'll put as I saw a guy on another forum say one time

"At best it would be a trailer queen with a dark history"

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Deano
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Re: Hydraulic drive system?

Post by Deano » Sat Jul 18, 2015 8:44 pm

My opinion is not unlike Afficted's. And like MoeJoe, I don't see the advantage/benefit.

If a man had more time and money than anything else, it could be a good means of addressing both.

IMO, producing a variable pitch prop would be a much more productive use of both resources.
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fishonhenson
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Hydraulic drive system?

Post by fishonhenson » Sun Jul 19, 2015 5:50 am

Advantage:
Placement of engine anywhere you want and low center of gravity. Smaller engine needed for pump. Instant pressure because the fluid is always running at full volume, valves open and close for speed of prop.
The parts are not that expensive and are readily available. Almost every drive system in the world is a hybrid of hydraulics.

You wouldn't need a variable pitch prop, the rpm ramp up would be very close to direct drive. Remember the fluid is a closed loop system constantly running.

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Prototype
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Re: Hydraulic drive system?

Post by Prototype » Mon Jul 20, 2015 10:23 pm

Fish,

Take one giant simon says step backwards! Do you know what a hydraulic drive consists of and or what it takes to run and cool it at maybe 1k rpm not to mention 2-3k rpm if a drive could be geared to that. My 25 gallon res still gets burning hot running 2 hours at 3k at 3000 psi even with a after cooler.

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Re: Hydraulic drive system?

Post by happy harold » Tue Jul 21, 2015 8:31 am

I shouldn't get into this. debates like this sometimes take on a life of their own. ok. with an airboat, its all about weight. that quickly takes hydraulics out. on a barge or even a ship you no doubt could make it work especially with hull pipes to cool the oil. but running dry with a system turning the prop tips at just under the speed of sound? we had a local man spend a lot of time and money trying to make it work. with the 500 gallons of fluid you would need alone, would overpower most airboat hulls. unless you are financially in the category of trump, I would suggest you take the road travelled by the rest of us. don't give up your dream, just keep it for happy hour. jmo

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keebo
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Re: Hydraulic drive system?

Post by keebo » Tue Jul 21, 2015 4:41 pm

Harold is spot on with his take, for fun I ran the numbers to see what it would take to swing a 72" prop at 3000rpms, the amount of fluid alone to achieve this was entirely too heavy to be efficient not to mention the tank, cooler and everything else.
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glades cat
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Re: Hydraulic drive system?

Post by glades cat » Wed Jul 22, 2015 9:16 am

Some other stuff to consider.
The transformation of one form of energy into another is usually accompanied by losses. Think about the hydraulic drive system you desire. You begin with fossil fuel converting to heat in combustion(heat loss), coupled to a hydraulic pump(mechanical loss), pushing fluid(friction/heat loss) to high pressure accumulator, then to a valve body(internal friction), driving a hyd motor(internal friction loss) converting to rotational force, fluid returning to a low pressure reservoir and heat exchanger back to the pump.
That is a lot of energy conversion. Not as efficient as it may appear unless you recover the heat loss and use it for something else…like cooking a roast on the ride out to the swimming hole. :cheers: These systems require a constant pressure to do their work…so the engine must stay at its design RPM.
If you build it, it would be revolutionary and I'd sure like to see it.
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Re: Hydraulic drive system?

Post by Afflicted » Wed Jul 22, 2015 9:52 am

To add to the weight issue, u wouldn't have a robust LS or a hot small block turning a hudraulic pump.. It would be more suited with a very heavy industrial diesel

That's y heavy equipment doesn't have LSs and 383s

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Prototype
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Re: Hydraulic drive system?

Post by Prototype » Wed Jul 22, 2015 10:08 pm

Afflicted wrote:To add to the weight issue, u wouldn't have a robust LS or a hot small block turning a hudraulic pump.. It would be more suited with a very heavy industrial diesel

That's y heavy equipment doesn't have LSs and 383s

Your dead on plus at 3000 psi pushing over 200 degree oil the flaws of not replacing a hose before it fails is kind of obvious. To date I've never seen a hydraulic hose life replacement statement from any manufacture? Plus the fact that most high pressure hoses with big psi and volume behind them are mounted so the op is steel cased from them.
It does sound cool with a little 40 hp diesel and a butt load of time and money though on a small scale. I'd honest forget/block out reverse though for obvious reasons LOL

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