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Baby Blender Help Needed

#1
Hey guys, just built a baby blender with the recommended components (Turnigy plush 25amp, NTM 1200kv, 3s 2200mah 8x4 prop) And I just can't get it to take off. It seems to me like it does not have enough power or my plane is too heavy. Do you think that an 8x4 prop is too small. Is there any other prop that would give me more torque. Because I feel the plane is having trouble getting up to speed and therefore not taking off. This also may be due to my poor piloting skills.

Any help would be appreciated.

-George
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
Hey George!

I'm assuming you bought this motor (only 1200 NTM I see):

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17345


Nice motor. Looking at the specs on the HK site, powered by 3S turning an 8x4 prop is not the most you can get out of this motor, but you should be burning around 100W at WOT -- respectable. At 100W, The BBender wouldn't be the fastest thing in the air, but it should be flying.


If you hold it back and go WOT, it should feel like it's pulling hard against you -- around 800g of against you (~1 3/4 lbs). If it feels like you're getting a lot of blowing air, but not much pull, somethings not running efficiently.

First, make sure the writing on the prop is facing forward, toward the fresh air (backwards it'll just stir the air, not throw air back for thrust). It's easy to mess up but just as easy to fix.

Spin the motor by hand -- it should spin freely. If it feels stiff (not the click of the magnets but like someone's stepping on the breaks), you've likely got an overtightened set screw somewhere. loosen them one at a time and re-test. if it spins easier, you might have found the culprit, otherwise, gently tighten it back up.

Finally, check those solder joints -- a cold solder joint will cost you valuable power to the motor. At the joints, look for dull blobs of solder. there are plenty of good how-to's online about cleaning cold solder joints.

Whatever is keeping you on the ground, you need to fix that before you soup up. Getting a faster prop/battery won't get you in the air if you're wasting power somewhere instead of putting it into the air.


Now *after* you've found the problem:

Want a little more juice? The datasheets show you could step up to a 9x4.7 and pick up another 50-75g, or a 10x8 to add 70-115g (with added speed). From the data chart someone submitted, the 10x6 will burn out your motor if run WOT for too long, but could cruise nicely on it if you keep the throttle back (if you've got a watt meter, check current before you go flying, and think about reducing your throttle's throw). Your other alternative for punch is up to a 4 cell, but props are cheap.

Best of luck tearing up the air!