Motor selection: 1512 vs. 1515

[fliir]

I am planning a 15-17 pound, scale project (20% T-34C). I want a 125w/lb power system for takeoff/emergency with a typical (scale) maneuvering power of 80w/lb.

I have found two good contenders: the 1512/2Y and the 1515/3D, both on 9 serial and 5.3 gearboxes, turning a 16x12 3 blade. This gives me 2200w max, a 1200w - 1300w maneuvering load with good pitch speed.

How conservative is the 1512 rating of 1200 continuous? Should I be worried if the aircraft spends 2-3 minutes at 1200w - 1300w? Or would you go to the 1515? Another option - a finned 1512 versus a plain case 1515.

Any input would be appreciated.

David

[Larry3215]

Im flying a 15 lb Great Planes Ultamate 160 on a 1515 2Y, 6.7/1 22x12 2 blade prop 10S1P 5000 packs.

My peak power is in the 2300 watt range, but my average usage is about 800 watts over the course of an 8 minute flight with some mild aerobatics and minor 3D. The motor comes down at around 95 - 100 deg on an 80 deg day. Thats the way I like it.

Your bird is going to be heavier it sounds like to me.

I personally would go with the larger 1515 finned motor. That way you know your not pushing the limits. Its not that much heavier or more expensive for the peace of mind. Plus it give you head room if the project ends up heavier than anticipated or if you go to a larger or faster or more aerobatic model down the road.

Larry

[fliir]

Sounds like you are running a little more voltage and a bit lower amps to get the same power level.

I tend towards your suggestion, but I have been building electrics since motors had names like 450 Race and batterys were 1300SCRs so I instinctively want to take all extra weight out of my projects. It was my real consideration with the 1512. The money isn't the deciding factor (although I do keep all that they give me ;) )

Any input by others would be appreciated (Steve?).

David

[Larry3215]

I know what you mean about weight. Its a constant tug of war between performance and weight.

With this size project its easy to say a few extra ounces wont matter. To some degree thats true, but they do tend to add up.

Good luck!

Larry

[fliir]

I received some feedback from FlyDMA that I shouldn't consider anything LESS than the 1515, with a possible upgrade to a 1521. I guess that tends to eliminate the 1512 from consideration...

[fliir]

The motor is purchased, so the question is now moot (no negative feedback is permitted ;) )

[Larry3215]

Good luck!

(cant give any negative feedback since I dont know WHICH motor you ended up with :) )

Larry

P.S. build thread???