DJI 450 with Naza lite does weight make a difference in stability

[bensid54]

As the title says I have a DJI450 with a Naza lite controller and I was wondering if my battery setup can affect the stability of my quad. I have two 2200mha 3 cell lipo batteries on the top deck of the flame wheel on either side of the GPS antennae, will a battery setup like this be too much weight and affect my stability, or do I need them put in a different location such as below the centre of gravity?

 

[Motopreserve]

Weight can definitely effect stability. But the thrust specs of the motors/props as well as weight of batteries (and AUW) will be the most useful info to help determine if you're suffering from overweight issues.

Center of gravity is key here too - on each axis.

 

[bensid54]

I don't think it's over weight, the batteries sit so that the tops of them are level with the tops of the motors. I'll take a picture of my setup and post it later.

 

[bensid54]

Here are the pictures of my battery locations along with pictures of my chopstick landing gear.

 

[Motopreserve]

Have you tried to determine how the center of gravity is with a string? You have some things off the front and back which may cause unease.

You might try the batteries below as a test. See how it handles.

 

[bensid54]

I was thinking of hanging them below maybe create sort of a pendulum effect, it will be worth a try.

 

[Motopreserve]

It is definitely worth a shot.

Also, Try to do some calculations for the motors you have, the props you're running - and what type of thrust that's producing. Then weigh the MR with everything on board (including batteries). If you're overweight - you'll be at a value that requires more than 50% throttle to hover.

 

[bensid54]

It's all DJI motors and 18 amp ESC the only thing non DJI is the batteries, receiver, props and chopsticks. I did weigh it in the past and it was under maximum weight the props are 9 inch fairly flexible ones and it will hover at 50% throttle it won't hover at 50% with the stock eight inch props.

 

[SleepyC]

With a NAZA it will always hover at 50% throttle stick. What Moto means is 50% of the motor's power.
What you need to do is weigh your rig.
The MAX weight a 450 can handle with the stock DJI motors and ESC's is Take off Weight: 1,600g (3.5274 lbs)

So if your rig is over 3.5 lbs AUW it's too heavy.

 

[Motopreserve]

Sorry. That is what I meant. Thanks Sleepy.

It's worth checking to rule out.

 

[bensid54]

Thanks I'll go weigh the quad now.

 

[bensid54]

It weighs 2lbs 16oz and I slung the batteries underneath it even feels steadier to carry, I'll get out and fly it on the weekend and let you know how it went.

 

[SleepyC]

Ok, next suggestion would be to try and get the center go gravity to the center of the rig. Meaning if you hang the quad from the center by a string it would hang level. This will greatly help stability. Also balance props.

 

[bensid54]

Props are balanced, as far as hanging it from centre the GPS puck is there and that may be a little tricky. I could however place my scale under each leg and weigh them to see which one weighs more. Worth a try that may work.

 

[Motopreserve]

It weighs 2lbs 16oz

So 3lbs??? That should still be in the safe zone for the motors. That's WITH batteries, correct?

The center of gravity is more about seeing if the weight distribution is correct. So the single leg method might not tell you much.

If you put a string under the frame and center it - hold it out so it doesn't hit the GPS and see if it tips forward or back, or if it stays level. You can the move the string 45* and do the same - that will tell you left to right balance.

 

[bensid54]

Funny I didn't notice But 2lbs 16oz is three pounds unless the scale is reading in tenths in metric it was 1.11kg which to me translates to a little over 2.2 pounds. Regardless the weight is fully loaded and I think CG may play the biggest part I'll check that out today. I see you point about the single leg weighing idea that won't work, maybe I can remove the puck to try out the string idea I'll try that today.

 

[bensid54]

I'm going to have a good look at that made in China scale hopefully the problem is just me.

 

[Motopreserve]

. Chinese made....hot or miss.

If you're under the 1600g with batteries, you should be good. Seems like center of gravity (CoG) is the most likely culprit. Remove the puck, it'll give you a more accurate reading on how it's laid out - and it's not that much of a pain to put back.

 

[JoeBob]

54, I wouldn't worry about your batteries being on top of the frame, because they're still below your props, which is where the center of thrust is located.

Search 'Pendulum fallacy' and multirotor. There are 2 discussion on this forum and another on DIY about matching the center of gravity with the center of thrust.

Having weight below the CoThrust may feel more stable; but it actually makes the motors work harder to turn or move through the air because they have to lift that off-center weight against the leveraged displacement from center.

 

[bensid54]

I'll check those things out, thanks.