What size motor?? (Full Version)

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soccer du25 -> What size motor?? (10/8/2012 1:41 AM)

 Hey guys, I made a cardboard jet ( yes i know foam is better but i just had cardboard around ) and I am using an exceed rc rocket 1820 kv, blue lipo20c 7.4v 1500 mah battery, and a dynam rc 70a esc, ( yes i know it's an overkill ) i Tried it with a 6x4 prop and it didn't have enough thrust to get it going, and then the 7x4 had just a bit more thrust. 

Here's the question:
I am not familiar with kv ratings and what exactly they mean, i was looking at going for a 3000kv exceed rocket or a 2850 exceed rocket, i just don't know what will be stronger? mayber lower kv... IDK!! haha, I also want quite a bit of speed.



gaRCfield -> RE: What size motor?? (10/8/2012 1:48 AM)

kV is the number of RPM you get per volt - 1820kV x 7.4v = 13,468 rpm

Higher kV gives you more RPM, but you need to know the current rating (amps) of the motor - a bigger prop will give you more power, if you're not maxing out the motor's current capacity. 4 pitch is very low.

What does the 'airplane' weigh?



soccer du25 -> RE: What size motor?? (10/8/2012 2:01 AM)

 Im not 100% sure, somewhere close to a pound



soccer du25 -> RE: What size motor?? (10/8/2012 2:04 AM)

  http://www.hobbypartz.com/86ma04-2210-1820kv.html
that is my current motor:
And i have two of the servos listen below

the rest of the set up:
http://www.hobbypartz.com/83p-1500mah-2s1p-74-20c.html

http://www.hobbypartz.com/60p-dye-1018-70a-esc.html


http://www.hobbypartz.com/60p-dy-1007.html







iron eagel -> RE: What size motor?? (10/8/2012 2:51 AM)

With a 200 watt rated motor on a two cell don't hold your breath looking for speed. A lower pitch prop would give you more thrust but less speed same thing with a larger diameter prop.
You motor is rated for 30 amps on two cell li-pol this is not a good setup for speed by any stretch of the imagination.

I'd would be looking at something in the 50-70 amp range on 3-4 cells.
If size and weight of the motor is an issue try, Ammo 28 mm 3200 kv, himax or HET 2850 kv motor something in the 500-700 watt range.



soccer du25 -> RE: What size motor?? (10/8/2012 3:01 AM)

 alright well im looking at this being my new set up:

with the same battery

http://www.hobbypartz.com/86mb19-rocket-3015-2850kv.html

or

http://www.hobbypartz.com/86ma68-2205-3400kv.html



http://www.hobbypartz.com/60p-dye-1004-40a-esc.html








iron eagel -> RE: What size motor?? (10/8/2012 4:17 AM)

Still not stellar but better.
The two cell setup is more for the car guys not for a speed plane. Heck most guys are running 6-8 cell batteries with around 3KWW of power for speed planes.
Using a High End Technology 2w 23 (600 watt) motor on a 2.5 43 inch span airframe the bet I have gotten out of it on a three cell with a 6X5 prop was about 150 or so at 920 watts.
I have been trying to get it to work with a smaller prop but have yet to test fly it with the mods for the smaller prop diameter. That and I have yet to fly it with the four cell (full power) setup just trying to tune the prop size to the airframe or airframe to the prop size depending upon your perspective.
If cost is a factor try a BP hobbies lower KV motor with a higher cell count, something like 4-5 cells and a 2 KV motor.



jester_s1 -> RE: What size motor?? (10/8/2012 1:34 PM)

I responded to your cross post in the beginner forum. For future reference, it is generally frowned upon to post the same question in more than one forum. Pick the right one and go from there.



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