Quadcopter throttle problems

[RotateB4TheEnd]

Hey all,

I am having some difficulties with my quad. Here is my current setup: quad x-config on the anycopter frame, turnigy park 300 1380kv motors, multistar 15 amp escs, a 2200 3s 25c lipo, and a multiwii pro controller board running multiwii 2.2.

The issue I am having is that when the quad descends and I want to climb again, I will apply throttle and the quad will not climb. I have even eased it up to full power and the descent continues. However, I can land and then take off again with no problem.

I'm not sure if i'm overweight (38oz), the esc's are slow to respond, or the motors can't draw any more power, or something else.

Does anyone have any thoughts on this?

 

[FlyingMonkey]

What props are you using?

 

[RotateB4TheEnd]

8x4 Slow Fly's: http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=25817&aff=247441

 

[IBeHoey]

After running your setup in eCalc, and taking a guess on your prop size, I'm thinking you have a weight issue. With a 7x3.5 prop (anything larger and you'll be maxing out the motors maximum amp draw), max thrust for each motor is around 420g, and with multirotors, ideally, you're gonna want to have a 2:1 thrust:weight ratio. 420x4=1680g /2=840g or 29.6oz should be your target weight.

 

[RotateB4TheEnd]

Ya, I found eCalc and tried it for the first time and it said my max power was greater amps than the motor could handle. Does that mean that once I hit the 7amp limit i'm not gonna get more throttle out of the quad?

 

[IBeHoey]

Well, with those props it pushes the thrust up to 550g for each motor, and that would put you close to a 2:1 ratio, sooo, hmm.

Have you set the endpoints for each channel in MultiwiiConfig?

 

[IBeHoey]

Ya, I found eCalc and tried it for the first time and it said my max power was greater amps than the motor could handle. Does that mean that once I hit the 7amp limit i'm not gonna get more throttle out of the quad?

Eh, kind of. That limit is there to tell you that the motor can only safely draw that much power before you run the risk of burning it up. As you past that limit, the motor will continue to spin faster and faster, essentially giving you more throttle/power until it blows.

After looking over the product page again for your motor, I'm willing to bet that 8x3.8 prop recommendation is for running it on a 2S LiPo. So yeah, it is a weight issue you're having.

 

[RotateB4TheEnd]

I have not. I'm not sure how to do that. In the GUI the throttle throw appears to go the full length of the spectrum, but I don't know how accurate the endpoints are.

 

[IBeHoey]

Basically what you're gonna want to do is hook your board up to the PC and run the MultiwiiConfig tool (or WinGUI), and on the right you'll see the PPM values for each of your channels. The min/center/max for each channel should be 1000/1500/2000. Depending on what transmitter you're using, adjust the limits of each channel until you can get it within that range, or as close as you can. It's better to be within the range (ie 1010/1500/1990) than outside of it.

As per my post I edited above, I'm fairly certain it's a weight issue. You're gonna want to get your AUW/including battery down to about 30oz.