Received-SPF: none
 receiver=logan.com; client-ip=216.148.227.151; envelope-from=rlwhite@comcast.net
Date: Sat, 8 Jul 2006 09:55:49 -0600
From: Bob White <rlwhite@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Nothing to do with Rotary Engines, but....
Message-Id: <20060708095549.46cc9f98.rlwhite@comcast.net>
In-Reply-To: <list-1228826@logan.com>
References: <list-1228826@logan.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit

Hi Wendell,

I think a hp is a hp, but the electric motors are rated at continuous
power and the gas engine is rated at peak power.  So indeed based on
the rating, a smaller electric motor is sufficient.  Particularly when
you can super juice them to get much higher power for a short time.

Another thing I forgot is that there will be 300 lbs of gas I won't
need.  So if I add that, then give up 300 lbs of useful load, I could
get 900 lbs of batteries in my BD-4 and still have enough useful load
for me and a small passenger.  If I then run a low cruise speed on 100
hp I will get a 4 hour endurance or so.  Using Bill's earlier estimate,
the batteries will cost $270,000!  They will be good for 2000 cycles,
or 8000 hours so cost will be $33.75/hr.  That's about the same as gas.

Fortunately, my house isn't worth enough, so I still can't do it. :)

Bob W.

On Sat, 8 Jul 2006 10:29:24 -0500
"Wendell Voto" <jwvoto@itlnet.net> wrote:

> What is the equivalent hp conversion of electric to gas engines? I'm thinking it is about 2:1 (tried to look it up quickly, couldn't find it), so instead of 180 hp, you would only need 90 hp electric.
> 
> Wendell
> 
> 
> Subject: [FlyRotary] Re: Nothing to do with Rotary Engines, but....
> 
> 
>   Think about how small the alternators on big HP APU's are and you get the picture on how small you can make a powerful electric motor if you are willing to work at it a bit. You can easily make a 100 HP electric motor that weighs 100 lbs. It would not likely be DC, however.  
> 
>   Electric motors for stationary use have no constraint on weight. The only reason you would want to make one lighter would be to save on materials and/or on shipping. If you make a motor of a given HP lighter, it will cost more, spin faster, or be less efficient than the heavier motor. If you are running on batteries, you must be careful not to save weight on the motor by compromising efficiency, only to add to the total vehicle weight by requiring more batteries to make up for the reduced motor efficiency. 
> 
>   Bill Dube'
> 
>   george lendich wrote: 
> Hi Bill,
> 
> I'm relieved.  I won't have to mortgage the house until the technology
> advances enough to reduces the weight by a factor of 5. Currently it
> looks like I would need about 1400 lbs of batteries.  Get it down to
> 280 lbs and allow 100 lbs for the electric motor and my W&B will work
> out about right. :)
> 
> I'm looking forward to seeing what you come up with for the aircraft
> batteries.
> 
> Bob W.
>     
> 
> Bob or Bill
> I would have thought a 130hp DC Motor  would weigh more than 100lbs.
> Any rule of thumb on weight of motor to power output ?- I guess there's a
> lot of copper windings per HP!?
> George (down under)
> 
> 
> 
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/
> 
>   
> 
> 


-- 
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (first engine start 1/7/06)
Custom Cables for your rotary installation -
http://www.roblinphoto.com/shop/