Zagi Sticker was on fire!  
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Zagi Sticker was on fire! - 6/27/2003 4:49:08 AM   
dadzilla-5


 

Posts: 82
Joined: 9/28/2002
From: Chetwynd, BC, CANADA
Status: offline 		Hi - I am running a stock speed 400 direct drive in a home built airplane that I designed around the old ace whizzard wing. When I use my nihm 1800 packs, (8 cell) the motor gets so hot it would burn your finger to touch. The "Zagi Trick RC" sticker actually smoldered on the last flight - I get about ten minutes. I have drilled air holes in the front and lifted the front hatch to allow for airflow through the motor area. Then I cut away a slot in the top hatch to let even more air through. The airplane needs to run at 80% throttle or better to be fun to fly...there is not room for a geared 400 unless I redesign - and this one is a blast except for the over heating. Any ideas on how to cool this one down?
       Post #: 1

Zagi Sticker was on fire! - 6/27/2003 8:41:29 PM   
Matt Kirsch



Posts: 7079
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline 		What propeller are you using? The motor should not get that hot on 8 cells unless you are using a much larger propeller than the white Zagi prop.

If you are using the Zagi prop, the motor is shot. Replace the motor with a new one. Any "6V Speed 400" motor is the same exact motor.

(in reply to dadzilla-5)
       Post #: 2

graupner 6X3 folder - 6/28/2003 2:57:00 AM   
dadzilla-5


 

Posts: 82
Joined: 9/28/2002
From: Chetwynd, BC, CANADA
Status: offline 		I am using the graupner 6X3 folder - grey one, not the CAM version.

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       Post #: 3

Zagi Sticker was on fire! - 7/5/2003 11:20:35 PM   
Derek_TX



Posts: 114
Joined: 10/1/2002
From: Temple, TX, USA
Status: offline 		Try a smaller prop to reduce the amp draw...

(in reply to dadzilla-5)
       Post #: 4

maybe go geared? - 7/5/2003 11:36:24 PM   
dadzilla-5


 

Posts: 82
Joined: 9/28/2002
From: Chetwynd, BC, CANADA
Status: offline 		Maybe I should try using a gear box? I have a friend who would let me try his 1:8:1 gearbox - think that might help?

(in reply to dadzilla-5)
       Post #: 5

Zagi Sticker was on fire! - 7/5/2003 11:48:36 PM   
Derek_TX



Posts: 114
Joined: 10/1/2002
From: Temple, TX, USA
Status: offline 		It will help plenty... try it!

(in reply to dadzilla-5)
       Post #: 6

gearboxes are a bit of a mystery - 7/5/2003 11:52:46 PM   
dadzilla-5


 

Posts: 82
Joined: 9/28/2002
From: Chetwynd, BC, CANADA
Status: offline 		That was a quick reply! Here is the thing - not being very mechanical, I don't know which gearbox to use. The 1:8:1 is here and free, but I'd like to know how you should actually choose the correct box for a model?

(in reply to dadzilla-5)
       Post #: 7

Zagi Sticker was on fire! - 7/6/2003 8:41:48 PM   
Derek_TX



Posts: 114
Joined: 10/1/2002
From: Temple, TX, USA
Status: offline 		You can do it the scientific/engineering way and use a tool like motocalc to predict and select.
Or you can do it empirically, that is to try out combinations till you hit a sweet spot. Keep your eye on both the motor and batter6y temp. Stop if the heat is rising too fast. If it is rising too fast, drop the prop pitch or diameter, or both.

Your 1.8 :1 is prolly good for the folding prop you have, or a 7x4. The penalty with too little prop is reduced thrust. Excessive RPM would also be a problem at the extremes. Usually higher RPM in a motor is desired as they are more efficient in those ranges.

So try out several props and notice how much thrust & heat are generated.

(in reply to dadzilla-5)
       Post #: 8

sounds good - 7/6/2003 10:35:44 PM   
dadzilla-5


 

Posts: 82
Joined: 9/28/2002
From: Chetwynd, BC, CANADA
Status: offline 		sounds good - I have not yet tried motocalc but I don't think I can put it off much longer. In the mean time, I'm going to try the 1:8:1 as soon as I can. Thanks for your input!
Mark

(in reply to dadzilla-5)
       Post #: 9

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