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Tailspin Ken
09-01-2005, 07:32 PM
How does one calculate W/lb? thanks!

Ken:D

Mike Parsons
09-01-2005, 08:12 PM
Take the measured Watts (using a wattmeter or similiar in line between the battery and ESC) and divide it by the weight of the plane. 600w/6lbs= 100w/lb.

Tailspin Ken
09-02-2005, 02:30 AM
I asked this question very poorly. Here is what I meant to say. Is there a mathematical formula for calculating watts without using a meter. I want to calculate W/lb.
I apologize for the really stupid question that I irst asked.

Ken

2dogrc
09-02-2005, 02:56 AM
I asked this question very poorly. Here is what I meant to say. Is there a mathematical formula for calculating watts without using a meter. I want to calculate W/lb.
I apologize for the really stupid question that I irst asked.

Ken

Yup! Watts is power! So multiple Volts*Amps=Watts!

Dr Kiwi
09-02-2005, 03:06 AM
But one needs a meter to measure the volts and the amps - so I can't see how to calculate or measure watts without one!

Mike Parsons
09-02-2005, 03:21 AM
Yup! Watts is power! So multiple Volts*Amps=Watts!
True

But one needs a meter to measure the volts and the amps - so I can't see how to calculate or measure watts without one!
And especially true.

2dogrc
09-02-2005, 03:23 AM
hmmmm...well some companies post the data for their motors. The volts are just what ever battery you are using. You can purchase a cheap multimeter at a electronics store. It is worth the price! It could save you a ESC on day!

here is a link to a cheapy!
http://shop2.outpost.com/product/2389319#detailed

Mike Parsons
09-02-2005, 03:25 AM
Yes, whether a cheaper DM or a wattmeter, knowing the amps of your setup can be the difference between successful and expensive.
-Mike

ForestCam
09-02-2005, 04:12 AM
here is a link to a cheapy!
http://shop2.outpost.com/product/2389319#detailed
I use my $3.99 Harbor Freight special. :D

jonnyjetprop
09-02-2005, 04:42 AM
IMHO, A wattmeter is the best investment you can make. Or borrow one from a friend. It can not only tell you watts and amps, but also voltage depression. I take setup info off the internet with a grain of salt. A starting point, but more than once I've been suprised by the readings I got. It will save you money in the long run.

John

Tailspin Ken
09-02-2005, 05:24 AM
No doubt a meter is in my future. I was just trying to get a ballpark figure using a chart to determine how suitable a given outrunner would be with a given prop. The site gave me a chat that would render approximate amps draw for the prop using a given battery. From that I needed to convert the amps and volts to watts to get the W/lb.
Thank you all for your help. My question has been answered more than adequately!
Ken