Crunch,
We're back to the gearing, it seems.
I can't see, how we can change the gears in a lower unit, so an extra belt drive on top, as Myles suggested, remains the only option to change the prop revs with a given motor.
You'll need an extra bearing for the top end of the drive shaft and a plate to hold that bearing.
The huge advantage is, that we can play with different pulley sizes for optimum results.
Let me know how the dinghy performs with the 10HP in the back and a test with an even smaller outboard could be useful as well.
Rob on Linda
--- On Tue, 5/24/11, bethanne Hazelton <antaraz2000@yahoo.co.uk> wrote:
From: bethanne Hazelton <antaraz2000@yahoo.co.uk>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Tuesday, May 24, 2011, 3:03 PM
Hi Robby, guess who? I buzzed your boat this am but I guess when you are retired you dont have a need to get out of bed and start the day by 0830 like the rest of us. anyway, I am having second thoughts about the 72 v system we have come up with. It seems too risky and too expensive.(I will explain risky to you in person) 7000$ packed with electronics on a few sheets of foam in the salt water is one of my fears. Im trying to get a 9.8 hp Yamaha to see what the dinghy reacts like...rpm etc. the one I have located has mechanical pump problem. The guy with the ICE figures doesnt know I guess or I misunderstood what he was saying.
The 15 yamaha 5300rpm peak 36 kgs 27:13 ratio ...prop turns at 2551 rpm (stock engine) . If we got a red that would raise the rpms up to 3000 or 3500 with a diff. red. and THEN began playing with the prop pitch/dia. we might get close. It seems the 1" pitch only goes up 200 rpm which sounds like a sizeable bend? we would never get 1000 extra revs.... I dont think. 1/4" diameter offers 200 rpm as well which is pretty good if we can get around that anti cavitation plate above. Since the torgue curve of an elctric motor seems to be fairly flat it might be able to handle the different reduction...? one ......of your friends Crunch
From: rob linda <rob_linda_2000@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Sun, 22 May, 2011 18:41:07
Subject: Re: [Electric Boats] Electric planing dinghy
Rob,
I have no torque data on the ICE, but I understood, that electric motors have full torque at low revs, reason one can use a bigger and more efficient prop, without stalling it at low revs, like what would happen with an ICE if the torque is insufficient at low revs to swing an over sized prop.
Rob on Linda
--- On Sun, 5/22/11, Rob Johnson <dopeydriver@yahoo.com.au> wrote:
From: Rob Johnson <dopeydriver@yahoo.com.au>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Sunday, May 22, 2011, 2:38 AM
As a matter of interest , how does the ICE torque figures compare to the electric motor proposed. Can anyone give accurate figures ?. Regards Rob J.
From: GeoMar Logistics <geomarlogistics@gmail.com>
To: electricboats@yahoogroups.com
Sent: Sat, 21 May, 2011 11:27:32 PM
Subject: Re: [Electric Boats] Electric planing dinghy
An ICE outboard run for prolonged periods at 5000 RPM will not last long and the fuel consumption at that throttle setting would be horrific. Having said that, electric motors have a pretty flat torque curve which should allow for a prop that takes a bigger bite either through pitch or increased diameter. Most outboard lower units have a horizontal tab above the shaft which limits the diameter of the prop. The following link may be helpful in determining your best prop size. http://www.rundquist.com/how_change_pitch.htm
Good luck,
George
On Sat, May 21, 2011 at 7:10 PM, rob linda <rob_linda_2000@yahoo.com> wrote: Kevin,
Thanks for responding.
We also concluded, that the weight of these AC induction motors is to high for use in an outboard, hanging from the stern.
We'll probably will go with a brushless Etek/Mars motor, that seems to have more rpm, than the brushed ones.(4000 rpm)
The ICE outboard runs at about 5000 rpm on the plane
We're hoping to compensate for the "lacking" 1000 rpm or so, by fooling with higher pitched /diameter props and different outboard legs.
Does anybody have an opinion on the feasibility of this?
Rob on Linda
--- On Thu, 5/19/11, Kevin Pemberton <pembertonkevin@gmail.com> wrote:
From: Kevin Pemberton <pembertonkevin@gmail.com>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Thursday, May 19, 2011, 6:26 PM
I guess you are asking about AC induction motors sold by EV companies.
Induction motors cover a much broader spectrum.
The industrial controllers used on 3ph motors can run the RPMs up to
double or more the rated RPM of the motor. According to literature on
the net 1800RPM motors when used with VFDs are the most efficient. The
controller I use with my 1800RPM motor will give 2.5 times the design
speed of the motor. The torque flat lines at 1800RPM, but this should
not be a problem as the motor still gives 100% of the torque it was
designed to give. DC motors give RPM based on voltage, induction motors
give the RPM based on frequency of the drive. You will not be able to
get more HP from the motor because of the controller design, limits
current, based on the motor connected to it, so size the motor
correctly. AC induction motors are larger and heavier than the DC motors
of the same HP. Inside a boat no problem, off the transom? Maybe.
You could use industrial equipment for your job, but high voltage (over
48) requires much more attention to legal issues. I invision supply
inverter(24 to 220), VFD, and motor under the hood of the outboard. 24v
supply cables into the hood completely water proof. Cooled using water
and coils around the motor and water heat sinks on the VFD and inverter
housing.
Seems like a lot of work!
Kevin Pemberton
On 05/16/2011 03:49 PM, rob linda wrote:
> We're still trying to make up our mind about the rpm issue, one
> encounters, if replacing the ICE power head on the outb
> oard with an electric motor for planing speed.
> Miles suggested belt gearing, which means extra bearing at high end of
> drive shaft.
> There also may be props pitched high enough, if we can find them.
> There is the Agni motor, which is pricey and probably overpowered.
> We're focussing at the moment on using an AC induction motor like
> this: http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac9.php
> At 6000 rpm this seems like a candidate.
> Looking at the power/rev curve :
> http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC9.pdf
> , it has this "bump" at 2000 rpm and looks like the power curve for a
> planing dinghy, where the "bump" happens while "getting on the plane",
> or am I guilty of naive and wishful thinking.
> Any opinions on this ?
> Anybody has experience with AC induction motors?
> Thank you
>
> Rob on Linda
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GeoMar Logistics
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