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marcham · 09-02-2009, 01:21 AM

Also keep in mind that the kv rating is established with no load (ie a flat piece of wood as the "prop"). Given that assembly and design standards vary from one manufacturer to another, 2 similar sized motors with the same kv rating will not give you the same RPM spinning identical props.

Generally speaking, comparing 2 motors of identical kv and similar dimensions, the more expensive motors will spin the same prop faster for the same amount of input current. Going with a cheaper motor sometimes requires getting a higher kv rating and expecting a higher current consumption.

Recently, I've been comparing cheap (hobbycity) motors versus mid-price motors (Scorpion). To obtain similar thrust, the Scorpion requires a 710kv motor whereas the hobbycity (Turnigy) requires an 800-900kv motor and consumes more current to spin the same prop at the same speed.

So the best way to shop is with the manufacturer's specs for a specific motor, at a specific voltage, with a specific prop.

Ex: http://innov8tivedesigns.com/Scorpio...30%20Specs.htm

http://www.bungymania.com/imageshome...erf1.php?id=73

There are websites dedicated to help us ballpark electric power systems. This is one I use often, although it takes a little getting used to:

http://www.rcadvisor.com/

09-02-2009, 01:21 AM	#5
marcham RCC Senior Contributor I am: Marc P Join Date: Apr 2008 Location: Manitoba, land of potatoes! Radio of choice: JR x9303 2.4 # of RCs: 8 Feedback: 0 / 0% Posts: 726 Total Props: 1	Re: What is KV Also keep in mind that the kv rating is established with no load (ie a flat piece of wood as the "prop"). Given that assembly and design standards vary from one manufacturer to another, 2 similar sized motors with the same kv rating will not give you the same RPM spinning identical props. Generally speaking, comparing 2 motors of identical kv and similar dimensions, the more expensive motors will spin the same prop faster for the same amount of input current. Going with a cheaper motor sometimes requires getting a higher kv rating and expecting a higher current consumption. Recently, I've been comparing cheap (hobbycity) motors versus mid-price motors (Scorpion). To obtain similar thrust, the Scorpion requires a 710kv motor whereas the hobbycity (Turnigy) requires an 800-900kv motor and consumes more current to spin the same prop at the same speed. So the best way to shop is with the manufacturer's specs for a specific motor, at a specific voltage, with a specific prop. Ex: http://innov8tivedesigns.com/Scorpio...30%20Specs.htm http://www.bungymania.com/imageshome...erf1.php?id=73 There are websites dedicated to help us ballpark electric power systems. This is one I use often, although it takes a little getting used to: http://www.rcadvisor.com/ Last edited by marcham; 09-02-2009 at 01:25 AM.