aldeburgh
Well-Known Member
Can someone tell me where i can buy a suiatable permenant magnet altenator between 18 and 40 volts and an rpm range of between 200 and 400 as the bespoke units are all too expensive.
Towed altenator
- Thread starter aldeburgh
- Start date
MASH
N/A
By the time you've spent all that time finding suitable parts, made it waterproof, cobbling it together, probably failed to get the impeller properly efficient and messed around for months the commercial ones begin to look like pretty decent value.
However, google is your friend, and e-bay his partner...
However, google is your friend, and e-bay his partner...
Ric
Well-Known Member
Agreed - I built my own about ten years ago - after much trial and error it sort of worked then fell to bits on a measly 200 mile crossing. I bought a commercial one that cost about the same as I had spend on all the bits for my first attempt - and it is still going strong 3000 miles later and produces double what my homebuilt one did. Sometimes you have to bow to proper r&d and economies of scale and buy something ready built...
vyv_cox
Well-Known Member
There are articles in both PBO and YM about them at the time of writing. I was quite surprised to read that the Aquair 100 costs less than £1000, producing 5-6 amps at 5 knots.
contessaman
Well-Known Member
Your easiest and cheapest option must surely be a second hand purpose made one? I was lucky enough to pick up an LVM AquaGen for 60 quid at Beaulieu's trunk -traders last year. It works a treat and has either seen little use or has been well maintained with new bearings etc.
Just from first principles, the AquaGen kicks out about 4 amps on average when I have used it (5 knots) The towed spinner is pretty hefty to extract that 48 watts from the water. Even if you got a small alternator its going to be kicking out a lot more wattage than that unless your batteries are fully charged (if so, whats the point!!) so your homemade spinner would be about the size and weight of your bower anchor in order to work?!!
If you are going to make your own you probably be better off using a 24 or 36 volt permanent magnet dc motor. this will give you the 14-15v you want to charge at modest RPM. you can find one thats quite small so wont need such a sea-anchor behind you to turn it...
Final thought, I have an old book on yacht design and it shows a picture of a dynamo belted off the prop-shaft to harness the power of a free-wheeling prop under sail. No idea how that would compare to a proper towed generator in terms of Watts per lb of drag. but its all interesting stuff.
Just from first principles, the AquaGen kicks out about 4 amps on average when I have used it (5 knots) The towed spinner is pretty hefty to extract that 48 watts from the water. Even if you got a small alternator its going to be kicking out a lot more wattage than that unless your batteries are fully charged (if so, whats the point!!) so your homemade spinner would be about the size and weight of your bower anchor in order to work?!!
If you are going to make your own you probably be better off using a 24 or 36 volt permanent magnet dc motor. this will give you the 14-15v you want to charge at modest RPM. you can find one thats quite small so wont need such a sea-anchor behind you to turn it...
Final thought, I have an old book on yacht design and it shows a picture of a dynamo belted off the prop-shaft to harness the power of a free-wheeling prop under sail. No idea how that would compare to a proper towed generator in terms of Watts per lb of drag. but its all interesting stuff.
contessaman
Well-Known Member
got me curious looking at dc motors on ebay and then I saw this:
http://www.ebay.co.uk/itm/12V-Ampai...trial_Tools_Generators_ET&hash=item19f5a593e8
could that be rigged off your transom to swivel up when not needed?
http://www.ebay.co.uk/itm/12V-Ampai...trial_Tools_Generators_ET&hash=item19f5a593e8
could that be rigged off your transom to swivel up when not needed?
