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On 19 Jan 2017, at 08:42, Hannu Venermo gcode.fi@gmail.com [electricboats] <electricboats@yahoogroups.com> wrote:
I am 99% sure that paddlewheels are no-where near 90% efficient at any
speed.
Think of it this way.
Pull the craft with a rope, using motor output as the measure of power used.
This will have zero slip and the power transmission will be 100%
efficient (no stretch on rope).
OR like this.
A human being can output about 100W max power, for a short time, when
trained, like on a bicycle by an athelete.
Pulling by hand, when standing on shore, the power is perhaps 20-50 watts.
By hand, you can pull a heavy 28 metric ton, 24 m powerboat (Baia
azzurra, 2x1300 hp, 60 knot deep v hull) at about 1 km/hr with no wind.
The boat will move exactly no-where with a prop or paddlewheel when
powered by 50 Watts.
You can also pull a 70 metric ton steel riverboat / lakeside craft by
hand, a bit slower, but it moves just fine.
What do You need in terms of hp ?
No idea whatsoever.
But since electric motors are cheap, or very cheap, does it matter ?
I would use an inverter and a 3-phase motor or better yet a servo motor,
both at 220V (50 hz, EU).
Since they are;
1. more efficient
2. cheap
3. any power levels are available for little relative cost 0.5 hp - 1000
hp or more
4. are meant for continuous duty and will last forever
I think most other motors would not last at all long, if actual use will
often or usually be 5 hours per day.
My thinking is influenced by the fact I went from 48V DC to 72 V DC, and
from 3-phase motor with VFD to 220V ac servo brushless, and the
difference is enormous.
Using several makes of drivers.
A 1-2 hp 3-phase motor is about 100$, and any power level is not much more.
Second hand is likely fine, and you can probably get 1-10 hp for not
much more.
Surplus center shows a 2HP one for 150$, and 5 HP for 406 $ new.
http://www.surpluscenter.com/Electric-Motors/3-Phase-Motors/3-Phase-Motors-Base-Mount/?page_no=1&fq=ATR_Motors_HP:5
Ebays shows new 4 kW VFDs for 150$, chinese (they will usually be fine).
Or a used hitachi 4 kW for 120$.
For my druthers, 4 kW motor + Hitachi VFD.
5 kW (20 kW peak) 12V - 220V inverters show up from 380 - 460$, ebay,
chinese.
And a heavy gearset to drive the paddlewheel.
Make sure the power electronics do not collect humidity, so they dont
rust inside !
A preventive laquer coat from the electronics shop might also be in
order, after they have been run a few times for a few hours.
HTH.
On 18/01/2017 20:03, elwelldon@yahoo.com [electricboats] wrote:
> But what DO i need in terms of HP/torque, etc. In a paddlewheel,
> torque, not speed is the issue. I suppose I could take a 1000W
> electric and chain gear the thing down from 1500 to 40 rpm at the
> wheel (which would probably exhaust the motor shortly), but you see
> the variables. Paddlewheels are about 90% efficient in transferring
> energy to the water, but only at low speeds, but that's fine. Not
> anticipating the boat operating for more than about five running hours
> a day.
>
> We are currently planning on something like four 100AH batteries wired
> up at 48 volts.
>
> More thoughts kids?
--
-hanermo (cnc designs)
Posted by: alexander jones <73foster@live.com>
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