I agree with Eric on this as regards designing, building, spec'ing and selling outboard motors with props.
AMeP is not developing and selling propulsion systems to include a prop, but rather, they are producing integrated electric motor/controllers.
For over 100 years, performance characteristics for electric motors have been fairly standardized to include:
(1) A PLOT of the following parameters on the same graph: Torque vs [Speed, Current (amps), Volts, Power, Efficiency] --- all these can easily be shown on the same graph
(2) Absolute Max Speed or Voltage
(3) Max Peak and Sustained Average Current and Power
(4) Thermal characteristics and cooling requirements as f(power)
Additionally, as applies to your boating clients, and since you're developing integrated motor/controllers, we'd like to know:
(1) Types of throttle sensors compatible
(2) Programmable options, if any
(3) Controller drop-out voltage (e.g. 48v rated motor/controller, is it good to 30v, 20v, 12v? My 48v Alltrax controller has been demonstrated to not drop out to 18v)
(4) Motor default direction and control means---e.g. brush motor controllers typically require external contactors to do this
(5) Any warning or safety features of note?
(6) Acoustic noise specifications and mounting considerations to reduce noise
(7) Electrical noise specifications, filtering, pre-charge or other requirements
You don't have to look far or look outside this industry to see what we expect.
Look at your competition, the MARS brushless motors.
Here you can find their specs: http://www.marselec
This is a bit frustrating for me as I expected better by now after discussing this issue well over a year ago with your designer.
Not only is there no published motor curve for the motor that has been "in production" for over a year now, but now you're already moving forward to produce and sell yet another unspec'd motor. That you would not realize that you are producing a motor and that the minimum you should spec is a motor curve is disturbing to me as an engineer.
On other lists, this would be the smell of snake oil. You can do better…injest the details provided above at the MARS site.
The bar has been set there.
Hope this helps-
-Myles Twete, Portland, Or.
From: electricboats@
Sent: Monday, February 15, 2010 9:30 PM
To: electricboats@
Subject: [Electric Boats] Performance figures
Kevin,
I think one effective way to publish performance results is to describe as much of the installation as possible. For example, if you published a small table of speed and current results and stated that they came from what boat, most people could extrapolate those results towards their own potential installation. Because most of these systems can be operated on multiple voltages, listing your performance figures in watts consumed at a given speed creates a baseline where disparate systems can be compared. Since we're dealing with boats, listing speed results in Knots rather than MPH is also helpful. Publishing average figures collected over time in various conditions should normalize your measured performance closer to real world conditions.
Let's say your first installation was an Ericson 28. With a displacement of 7,500 pounds, a LWL of 24'2" and a PHRF of 186, one can figure how that would compare to another fin keel boat in the 27' to 30' range. Once the basic specs are published about your drive, the battery bank and prop are the only remaining important variables. If the boat goes 3 kts with 800 watts, 4 kts with 1600 watts and 5 kts with 4000 watts, this data would tell a great deal about the system's overall performance. Posting additional results from other described installations would really start to build an efficiency model that would be meaningful to a wide variety of potential customers. Although some manufacturers publish observed top speeds, I don't find that data as relevant to auxiliary sailboats, power boaters may be more interested in this figure.
I have only found a few systems that have published this type of data, Torqeedo is a name brand that comes to mind with performance data for their various systems. That's one of the reasons that I am a Torqeedo owner today. My observed results are close enough to their figures that I would say that their data is realistic.
That's the kind of information that I look for. I'm surprised that most companies don't publish these figures and let their existing customers bear the responsibility for telling other potential customers how well the systems work. Anyway, this is just one man's opinion...
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@
>
> Myles,
>
>
> My apology for our exuberance, I have been withholding information on our site until finial testing is done as there has been much interest in this motor. We have two installations for the 5kw done and Arby is very eager to get the product out, which I have been developing the website for.
>
>
> As each boat is different, ie. displacement, prop size or other variables that affect any power curve a chart, showing unloaded power is the only one that would remain constant making a loaded power graph a sales tool only and will not represent what occurs in the “wild†with added variables such as topside wind, current and so on. If you have a workable suggestion as to how you would like to see a data graph done, or know of a standardized test that other companies follow, I will see if it is possible and have it done, for you.
>
>
> Thank you,
>
> Kevin Mannell
>
> AMeP
>
No comments:
Post a Comment