The statement that it takes 750W to displace 1tone is true but will bring you to hull speed in no wind conditions
--- In electricboats@yahoogroups.com, "hardy71uk" <p0054107@...> wrote:
>
> boats are different to airplanes because although the formulas are the same there are different practical limits . For example in boats the larger the prop the more efficient ( that is at slow and medium speed ; the normal electric range) thats why , as I understand it, Larry recommends beginning with the biggest propellor that has adequate clearance .Find the power needed for the desired performance and then select pitch ,gear ratio and motor to match.
>
> Chris S
>
> --- In electricboats@yahoogroups.com, Daniel Michaels <nov32394@> wrote:
> >
> > Thanks for the input Larry.
> >
> >
> >
> > I am more familiar with airplanes and props but I think they work about the same.
> >
> >
> >
> > We first take the max rpm we are running plug that into the chart to
> > find out how fast the plane will go with each pitch. Shorten or lengthen
> > the prop to let the engine run at max rpm. The pitch tells you how fast
> > the plane will travel.
> >
> >
> >
> > I am not sure the Triton was designed around an Atomic 4. I think an
> > Atomic 4 fit into the general usage for the Triton. The Atomic 4 went as
> > high as 20 hp. When only 10 to 12 could really be used. Running the rpm
> > only to 1500 gave you 11.9 BHP. It has a 13 inch 2 blade prop. So if I
> > had 12 hp available at 1500 rpm it would do the same thing. If I found
> > out what hp the electric motor had at 1500 rpm I should know if it will
> > turn the prop. Alternatively I could shorten the prop and turn a higher
> > rpm. I could also go with a 3 bladed prop. The electric motor I am going
> > to use is 13 hp @ 48v same as the Atomic 4. Only this will far
> > outperform the Atomic 4.
> >
> >
> >
> > This is what I have so far. this is from limited knowledge but I am learning every day.
> >
> >
> >
> > It takes 1 Kw per ton of displacement.
> >
> > 750w = 1 hp
> >
> >
> >
> > 36 v 140 amps 1400 rpm 3500 watts E Teck motor.
> >
> > comes to 3500/750=4.7 hp * 2.5 conversion factor to compare it to the
> > Atomic 4 = 11.75 hp. @ 1500 rpm the Atomic 4 is 11.9 Very close.
> >
> >
> >
> > 48 v 180 amps 4800 rpm 9800 watts E Teck motor.
> >
> > comes to 9800/750=13 hp * 2.5 conversion factor = 32.5 hp but at 4800 rpm if I cut the rpm in half I am at 16.25 The Atomic 4 is 16.2 @ 2000.
> >
> >
> >
> > At 36v 3500 watts the 1 kw per ton works out very close to a Triton at 4 ton.
> >
> > At 48v 9800 watts /2 = 4900 it comes out in my favor with a half ton to
> > spare and that is at half throttle. If I use a reduction drive on the
> > 48v of 2 to 1 I am out performing the Atomic 4 at every level.
> >
> >
> >
> > 36v at 140 amps run wide open
> > 6 * 260 Ah batteries / 50% = 780 usable Ah. 780 / 140 amps = 5.5 hrs.
> > run at half throttle or less and you will go much farther same as if you
> > throttled back on the Atomic 4.
> >
> >
> >
> > 48v at 180 amps 8 * 260 Ah batteries / 50% = 1040 usable Ah. 1040 / 90
> > (180/2) amps = 11.5 hrs throttle back even more and even I need some
> > sleep.
> >
> >
> >
> > Is any of my math correct. I gave it my best shot.
> >
> >
> >
> > Dan
> >
>
No comments:
Post a Comment