Orest
That’s good about the rpm I thought they must have been
Yes I am recommending 10 and 15/16ths – at the moment - it is a theoretical calculation, but yacht hulls seem to be remarkable consistent up to about 95% of their hull speed.
So the plan is slow the boat down a little and use far less input power, for the same or better performance
Any thoughts on why the voltage was lower?
Finally what is the LWL of you boat?
Yours,
Andrew Gilchrist
fastelectrics.com
Australia
0419 429 201
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Orest Iwaszko
Sent: Tuesday, 23 April 2013 2:45 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Results on paper including new under way dc voltage draw and amp draw
The rpm figures under way are all higher than the static test culminating with 1337/334 (4:1) at 100% throttle under way. compared to 1100/275 rpm at 100% throttle at the dock .
I will retest the voltage/amps at the dock and under way and add rpms underway to the chart.
No the controller didn't seem to heat up quite as badly .
Are you recommending 10 15/16ths ? I will recheck the data and add rpms . Really appreciate the help . wow
On 2013-04-22, at 7:52 PM, Andrew Gilchrist wrote:
Orest
· Are the rpm figures the same as static test?? I thought for making way they would be higher – actually they have to be to drop the amps?
· The amp draw is lower across the board – in the mid-range it has improved by 30% this is very good
· The gap in amp draw narrows from 30% improvement to low 20%’s at the 70% throttle point which shows where the motor is being overloaded
· The critical 14 amp point has moved from approx. 55% throttle to 70% throttle this is excellent improvement however it needs to move to 100% throttle for optimum efficiency – the boat will feel more responsive and be very economical at same or better speeds
· The peak rpm moved up 21.5% which is excellent but needs to rise by another 31% to put the 100% throttle at 14ish amp draw
· In this test the voltage is less at higher throttle position than it was in the static. Any idea why? For lower amp draw it should have been equal or better, due to less load
· How did the controller go – was it getting hot as on the static test?
· Given the load rises exponentially, in proportion to the cube of the increase in speed; The desirable reduction in amps is 31%, so the cube of this you want to reduce amp draw by .31%, you could make the reduction 1.31% of the 4:1. However, this would reduce load by 50%, too much. The cube root of 1.31 is 1.094. That means a large pulley of 10 15/16” diam and you should be on 14 amps or very close.
Yours,
Andrew Gilchrist
Australia
0419 429 201
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of oree zko
Sent: Tuesday, 23 April 2013 11:19 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Results on paper including new under way dc voltage draw and amp draw
Did one final tac test full out the highest motor rpm was 1337. 420 below the 1750 motor rating . Don't think Imissed anything now
Sent from my iPhone
On 2013-04-22, at 5:55 PM, "Andrew Gilchrist" <andrew@fastelectrics.com> wrote:
Orest
Just going to have a look at this in a table. Sounds much better
The gear ratio does NOT affect the HP
The gear ratio DOES affect the torque so for a reduction ratio like yours multiple the torque by the ratio and you have the torque at the prop
For an overdrive ratio divide the torque by the ratio – ie torque output falls
Yours,
Andrew Gilchrist
Australia
0419 429 201
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Orest Iwaszko
Sent: Tuesday, 23 April 2013 4:19 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Results on paper including new under way dc voltage draw and amp draw
significant less amp draw while under way
My actual pulley ratio now is 4:1 = 1100 rpm as high as fast as it will turn so if changed to 6:1 would get up to 1650 rpm ( im guessing a little higher with the extra 33% torque )
throttle motor amp under way underway dc shaft Hp developed boat HP developed &nbs! p; ;possible ( I DIDNT MEASURE BOAT SPEED BECAUSE IT WAS THE MOST UNRELIABLE MEASUREMENT OF THE LOT )
level rpm draw amp draw dc voltage voltage rpm at motor speed at shaft eg ? 6:1 HP at shaft IM CONFIDENT THAT 60% POWER WAS AROUND 2.3 -2.5 AND TOP SPEED OVER 3 MPH )
amps X volts motorHp x gear ratio
750
10 120 2.3 16 18 30 .05 .2 .3
20 310 4.6 4.1 35 38 77 .23 .92 1.38 actual pulley ratio is 4:1
30 490 7.0 5.4 54 56 122 .52 2.08 .312 so motor HP x 4 = Hp at the shaft ?
40 650 9.8 7.2 72 74 162 .96 3.84 5.76
50 790 12.5 9.6 93 92 197 1.53 6.12 9.18
60 910 15.1 11.7 110 108 225 2.17 2.3 8.68 13.0270 1005 17.1 13.9 125 120 251 2.73 10.92 16.38
80 1180 18.1 16.7 140 128 270 3.08 3.2 12.32 18.48
90 1100 18.6 18 148 128 275 3.2 12.83 19.2
orest
On 2013-04-21, at 5:30 PM, Orest Iwaszko wrote:
HI J , The transmission remains in neutral while the electric motor turns the propeller shaft . When I want to go fast I take off the elecric motor belt , start the big diesel and put the transmission in gear. The big diesel is 120 HP and pushes the boat to aprox 7-8 mph.
On 2013-04-19, at 11:41 AM, c.joseph@kbelectronics.net wrote:Hi Orest,
I don't know that a 3 HP motor can run that transmission. what size motor
was originally connected to that transmission?
Regards.
Charles J. Joseph
Applications Engineer
KB Electronics, Inc.
P. 954-346-4900 X 1128
F. 954-346-3377
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