flamewheel 550 CG and Balance
- Thread starter eagle1703
- Start date
OneStopRC
Dirty Little Hucker
Center of gravity for an 550 is in the center of the craft, most of us picked the 550 up by the legs, rotating to find out where it was heavy and shifting the battery around to cope with the weight difference. It is trial and error, you will have to find it and move your battery to offset extra loads.
Thanks, as I understand it you have to insert X Y and Z mesurments when configuring the NAZA that is what I am having trouble understanding. I get how to do the balance in the horizontal plane thanks to you. Am I overcomplicating this? have built RC models for over 45 years but this is my first hexcopter so trying to get it 100% correct before trying to fly it. Thanks for the help its all gratefully received, cheers from a freezing UK.
eagle1703:
Where is your GPS mounted on the frame? Are you using the little pole? Can you post an image?
Here's an example: My GPS is mounted on the frame/arm screws on the right arm of the hexa frame on about half the little pole height, call it 8cm tall. I fly the F550 as an "X".
The calculated horizontal CG is the center of the top frame plate, using the battery to balance everything out.
So imagine a left/right line from the arms through the center of the top plate. Any mount location forward of that line is a positive X value. Behind, negative.
Imagine a line through the center of the plate, front to rear. Any location to the right of that line, where I am, is positive. Left, negative.
The vertical, "Z", measurement is a bit more guess work because you'll need the "vertical CG" and it's probably the hardest to figure. But say right now, all you have on board is a battery, secured on the top frame plate. If you held the hexa up by the front 2 arms, so the nose points upward, it would probably want to tilt a little like it wants to fall over on its back because of the motors and battery positions. This means your vertical CG is toward the top plate, instead of centered between them. Let's call that CG position about 1cm under the top frame plate.
So add the height of the GPS puck above the top frame plate to the 1cm and what do you get? Using the little pole, probably something like 8-10cm. Since any Z value above the CG is negative, the number you enter for the Z axis in Assistant is "minus" 8-10cm.
My numbers are:
X=0 because I'm on the lateral line
Y= +8 because I'm 8cm right of the centerline
Z= -8 because I'm above the CG on a shortened pole
Ron
Where is your GPS mounted on the frame? Are you using the little pole? Can you post an image?
Here's an example: My GPS is mounted on the frame/arm screws on the right arm of the hexa frame on about half the little pole height, call it 8cm tall. I fly the F550 as an "X".
The calculated horizontal CG is the center of the top frame plate, using the battery to balance everything out.
So imagine a left/right line from the arms through the center of the top plate. Any mount location forward of that line is a positive X value. Behind, negative.
Imagine a line through the center of the plate, front to rear. Any location to the right of that line, where I am, is positive. Left, negative.
The vertical, "Z", measurement is a bit more guess work because you'll need the "vertical CG" and it's probably the hardest to figure. But say right now, all you have on board is a battery, secured on the top frame plate. If you held the hexa up by the front 2 arms, so the nose points upward, it would probably want to tilt a little like it wants to fall over on its back because of the motors and battery positions. This means your vertical CG is toward the top plate, instead of centered between them. Let's call that CG position about 1cm under the top frame plate.
So add the height of the GPS puck above the top frame plate to the 1cm and what do you get? Using the little pole, probably something like 8-10cm. Since any Z value above the CG is negative, the number you enter for the Z axis in Assistant is "minus" 8-10cm.
My numbers are:
X=0 because I'm on the lateral line
Y= +8 because I'm 8cm right of the centerline
Z= -8 because I'm above the CG on a shortened pole
Ron
Hi Ron that is a very comprehensive answer and I am getting close to understand what I have to do. I will send you a picture when I get on my laptop. But what I have done so far is NAZA mounted dead centre of bottom plate Rx zenmuse GCU and NAZA GCU round it keeping weight as central as positive.LED is on bottom to rear. GPS Antanae mounted using pole on the 5 o'clock position Arm with plate mounted were top plate sits ie using the 4 screw holes to coincidently mount gps plate. Battery will be on top plate going accross ie in line with the 9 & 3 o'clock arms. Of course the zenmuse camera gimbal mount will be on the bottom and in the centre of the wheel. Do you need any more info? Can't send picture from phone so will try again from home.
Cheers
Greg
Cheers
Greg
View attachment 14986 View attachment 14987Hi Ron here is the picture showing location of GPS antanae and a shot with top deck off giving electronics layout.
Cheers
Greg
Cheers
Greg
Attachments
Hi Greg:
OK, so knowing what you know now, what do you think your numbers will be?
Battery and Zenmuse centered both laterally and for/aft. Minor weight to the right side accounting for the GPS and that module labeled "zenmuse". GPS on the pole at the #5 arm mount area.
Again with the lines........... How far behind the lateral centerline, in centimeters, is the pole? That's a negative "X". How far to the right of the fore/aft line is the pole? That's a positive "Y".
Battery on top, Zenmuse on the bottom, both centered. Guessing, I'd say you're pretty much dead center vertically. So from the top of NAZA (about center between the 2 frame plates) to the centerline of the GPS puck. About 12cm? Then your "Z" value is a negative 12.
EDIT: are you mounting the gimbal? If not, then the Z number is less because you shift "upward".
EDIT #2: are you flying red arms forward? If you are, the GPS puck is backwards.
EDIT #3: by the direction your NAZA is facing, your GPS is definitely backwards.
OK, so knowing what you know now, what do you think your numbers will be?
Battery and Zenmuse centered both laterally and for/aft. Minor weight to the right side accounting for the GPS and that module labeled "zenmuse". GPS on the pole at the #5 arm mount area.
Again with the lines........... How far behind the lateral centerline, in centimeters, is the pole? That's a negative "X". How far to the right of the fore/aft line is the pole? That's a positive "Y".
Battery on top, Zenmuse on the bottom, both centered. Guessing, I'd say you're pretty much dead center vertically. So from the top of NAZA (about center between the 2 frame plates) to the centerline of the GPS puck. About 12cm? Then your "Z" value is a negative 12.
EDIT: are you mounting the gimbal? If not, then the Z number is less because you shift "upward".
EDIT #2: are you flying red arms forward? If you are, the GPS puck is backwards.
EDIT #3: by the direction your NAZA is facing, your GPS is definitely backwards.
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Hi Ron
I put the GPS puck on arm 5 as sujested by BOYD, and yes my two red arms are in the forward direction, I think I now see what you mean about the GPS Puk, I did not realise it has that tick on its surface indicating the direction it should face I will rotate it, ruddy small print!
I have been advised not fly with Gimbal attached for first flight, so will need the x y and z for that and of course another set to reprogramme once I feel safe enough to gamble the camera.
You are very helpful and I appreciate it.
So I guess my x would equal 0, my y approx +8 (antanae to right of centre line on arm 5) and Z approx -12 (Gimbal fitted) and approx -6 (Gimbal not fitted)
Greg
I put the GPS puck on arm 5 as sujested by BOYD, and yes my two red arms are in the forward direction, I think I now see what you mean about the GPS Puk, I did not realise it has that tick on its surface indicating the direction it should face I will rotate it, ruddy small print!
I have been advised not fly with Gimbal attached for first flight, so will need the x y and z for that and of course another set to reprogramme once I feel safe enough to gamble the camera.
You are very helpful and I appreciate it.
So I guess my x would equal 0, my y approx +8 (antanae to right of centre line on arm 5) and Z approx -12 (Gimbal fitted) and approx -6 (Gimbal not fitted)
Greg
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Greg:
Move the GPS as necessary. Using the #2 arm will put you +X, -Y and a -Z for numbers. Concur with leaving the gimbal off until you get the hexa flying well.
Once you're flying well, when you mount the gimbal in the frame center, it will just be a matter of changing the Z number.
Ron
Double check everything before that first flight.
Move the GPS as necessary. Using the #2 arm will put you +X, -Y and a -Z for numbers. Concur with leaving the gimbal off until you get the hexa flying well.
Once you're flying well, when you mount the gimbal in the frame center, it will just be a matter of changing the Z number.
Ron
Double check everything before that first flight.
Hi Ron
Thanks I will move the PUK to the No 2 arm ans ensure it indicates forward as you have suggested. Am away working for a week or so but once done I will do the mesurements and calculations once done will contact post another picture to you just in case you spot something I have missed. In the meantime many many thanks.
Greg
PS perhaps you might post a picture of your flamewheel it might help me visualise better, cheers
Thanks I will move the PUK to the No 2 arm ans ensure it indicates forward as you have suggested. Am away working for a week or so but once done I will do the mesurements and calculations once done will contact post another picture to you just in case you spot something I have missed. In the meantime many many thanks.
Greg
PS perhaps you might post a picture of your flamewheel it might help me visualise better, cheers
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Greg:
>So I guess my x would equal 0, my y approx +8 (antanae to right of centre line on arm 5) and Z approx -12 (Gimbal fitted) and approx -6 (Gimbal not fitted)
Nope.
Draw a line from arm #3 to #6, across the center of the frame. Is the GPS in front of that line or behind it?
The screws on arm #5 are behind that line, so your X number is negative. The rest looks good.
View attachment 14994
>So I guess my x would equal 0, my y approx +8 (antanae to right of centre line on arm 5) and Z approx -12 (Gimbal fitted) and approx -6 (Gimbal not fitted)
Nope.
Draw a line from arm #3 to #6, across the center of the frame. Is the GPS in front of that line or behind it?
The screws on arm #5 are behind that line, so your X number is negative. The rest looks good.
View attachment 14994
Attachments
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