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Old 14-08-2017, 09:26   #1
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Utilizing free wheeling prop spin

It would seem to me to be beneficial to use the free spinning rotation of the prop under sail to generate free power. I have devised a simple solution for utilizing the prop spin. Would not cause any wear to the transmission as it is an independent disconnect system. When the engine is stopped the Electro-mechanical clutch is disengaged. When the engine is started it engages. Mounted on the interior propeller shaft there is a pulley/alternator system. It will generate under power or when free wheeling.
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Old 14-08-2017, 16:08   #2
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Re: Utilizing free wheeling prop spin

Lots of previous discussion here about hydro generation, including shaft driven, low speed alternators.

The most recent one about your idea that I can recall is here:
Hydroelectric Generator

and here's one that discusses hydro generation more broadly (mainly about towed and Watt & Sea type hydro generators)

You may like to review those threads for a few ideas.
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Old 14-08-2017, 17:27   #3
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Re: Utilizing free wheeling prop spin

How about a better explanation or pictures of this coupling in your drive shaft?
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Old 15-08-2017, 04:02   #4
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Re: Utilizing free wheeling prop spin

I am a retired product design engineer, and I love to design and invent. I have read a few threads about complaints of free spinning props. To me it seems that this is an excellent way, a free way to produce another source to charge the batteries. I do have some sketches but need your email. Mine is robmclenn at yahoo dot com. I will send as jpg.
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Old 15-08-2017, 04:11   #5
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Re: Utilizing free wheeling prop spin

There are numerous types of electromechanical clutches available here is one.
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Old 15-08-2017, 04:44   #6
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Re: Utilizing free wheeling prop spin

Seems to me there's always a trade off ,

There are of course draw backs such as NOISE which seems to work it's way around the boat one way or another,(especially in some materials/construction methods. P brackets or not etc)

Also many marine transmissions are not designed to be free wheeled, wear and tear of bearings, higher risk of fouling from floating/submerged debris if the prop is turning as against locked,

All that said would like to see any new idea's on this for sure
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Old 15-08-2017, 06:23   #7
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Re: Utilizing free wheeling prop spin

The transmission would be isolated by the electromechanical clutch. The position of the transmission shifter would be inconsequential. The clutch when un-energized is free wheeling. Only when the engine is turned on is the clutch energized and turns the propeller shaft. But in both modes the shaft and pulley system will be generating power. I am well aware that there are pricy systems out there. The cheapest was around $1,800, and the most expensive around 100K that has swivel Sail Drives.
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Old 15-08-2017, 06:36   #8
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Re: Utilizing free wheeling prop spin

Just keep in mind that it's not actually "free power". An unfeathered prop creates a lot of drag and will slow you down. You might not care if you have lots of wind, but if you have little wind, you might.

Note that I'm not saying it's not worthwhile -- I'm just saying it's not "free", in the sense that sunlight for solar is really free.
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Old 15-08-2017, 06:50   #9
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Re: Utilizing free wheeling prop spin

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Originally Posted by Dockhead View Post
Just keep in mind that it's not actually "free power". An unfeathered prop creates a lot of drag and will slow you down. You might not care if you have lots of wind, but if you have little wind, you might.

Note that I'm not saying it's not worthwhile -- I'm just saying it's not "free", in the sense that sunlight for solar is really free.


This is so true, thanks Dockhead for putting it in such a non-judgemental way! I am surrounded by young idealistic people convinced of things like the oil companies keeping 100mpg carbs away from us and seemingly unable to grasp the really basic physics of things. I am going to try to use more of your tone than the know-it-all indignation that I normally throw at them!
Thanks, Dan
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Old 15-08-2017, 07:19   #10
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Re: Utilizing free wheeling prop spin

My original thought was to use a retractable Sail Drive, but that would be expensive. Also something that could be added to a new Hull during construction, but not so for existing configurations. So I read on here many complaints about spinning props. It strikes me that it is a free source for power generation. I have been inventing and designing stuff for 45 years. I am no novice at it. There are many manufactures that are designing electric drives. Some can be regenerative some aren't. What I do know is there is an never ending need for more power. As well as a quicker way to recharge one's battery banks! while sailing at night solar panels are useless, and fuel for the generator is expensive. Utilizing something that occurs naturally seemed to be a win, win, but I guess not?
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Old 15-08-2017, 07:30   #11
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Re: Utilizing free wheeling prop spin

What is the failure mode? Fail safe would be the only way to go on a cruising boat. It looks like you need power for it lock up.
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Old 15-08-2017, 07:31   #12
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Re: Utilizing free wheeling prop spin

Never attribute to malice what can be explained away by stupidity. Thomas Edison tried 2001 times to find a filament that would last. He said I didn't fail 2,000 times. It took 2001 to find what worked. When brain storming a product it is best, if no negativity is thrown into the pot!
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Old 15-08-2017, 08:00   #13
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Re: Utilizing free wheeling prop spin

What is the failure mode? Fail safe would be the only way to go on a cruising boat. It looks like you need power for it lock up. Okay you are correct it needs to be energized in order to use the power from the motor. I suppose a Mechanical Drive dog could be added in case of a failure. What happens if you have a clogged injector, Cracked Head, a blown connecting rod, water in the fuel? There is nothing in life that is guaranteed 100% except Death and Taxes! I suppose I would carry a spare clutch.
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Old 15-08-2017, 08:29   #14
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Re: Utilizing free wheeling prop spin

Quote:
Originally Posted by Dockhead View Post
Just keep in mind that it's not actually "free power". An unfeathered prop creates a lot of drag and will slow you down. You might not care if you have lots of wind, but if you have little wind, you might.

Note that I'm not saying it's not worthwhile -- I'm just saying it's not "free", in the sense that sunlight for solar is really free.
I agree, it's not free energy. It will slow the boat.
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Old 15-08-2017, 08:50   #15
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Re: Utilizing free wheeling prop spin

I believe that the situation with a prop in water is not the same as for one in air. A free wheeling prop in water generates less drag than a stationary one.

If you apply a load, the prop will slow down, thus generating more drag.
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