Thread Tools
Jul 22, 2012, 11:07 PM
Too Many Thread Subscriptions
TheFernMan's Avatar
Discussion

Multirotor Arms: Round vs Square?


I have a question.

Do you prefer round or square arms?
What have your experience been with either? Advantages and disadvantages of both?

My experience has lead been that round arms have a tendency to twist and hard to level. Carbon fiber is strong for arms and wont bend at the ends like square arms can.
Sign up now
to remove ads between posts
Jul 22, 2012, 11:47 PM
manual flying apologist
Adidas4275's Avatar
Round:
Pro:
Easy to source
Easy to add thrust angle to improve yaw performance on static yawing rigs
Boom Clamps are more durable
They will allow the motor mount to rotate in a crash absorbing some of the impact
Light Weight

Con:
Harder to keep motor thrust angle perfect
Bend fairly easily


Square
Pro:
Motor mount is 90 degrees on top and wont rotate
very sturdy and dont usually bend
can be easy to source in Al

Con
Boom clamps can be more prone to failure at the 90 degree joint
harder to find in CF
Snap rather then bending
Heavier


I have flown and built 3 rigs with round and 2 with square....

I dont know if i have a preference
Jul 23, 2012, 10:21 AM
Registered User
vineet_p's Avatar
That's a good analysis, I used only square twice and was happy, now I am using U-shaped dual-channel aluminium that's ultra-strong. They're usually used as rails in sliding glass panes in olden-style showcases.
Jul 23, 2012, 11:53 AM
Registered User
Mortimer's Avatar
Square arms are strong (I can prove it...) and easy to install.
Jul 23, 2012, 12:21 PM
recep
recep's Avatar
Boom clamps add weight. On my carbon boom y6 they add 120 grams in case of a hexa this number goes up to 240. 40 grams per arm. I dont even count the landing skids. With a square aluminum you just mount them.
Jul 23, 2012, 05:21 PM
Registered User
TheKnightFerrin's Avatar
Quote:
Originally Posted by vineet_p
That's a good analysis, I used only square twice and was happy, now I am using U-shaped dual-channel aluminium that's ultra-strong. They're usually used as rails in sliding glass panes in olden-style showcases.
What kind of material are your center plates composed of?
Jul 25, 2012, 08:41 PM
Registered User
Square arms are better for a simpler build. If youre out of the frequent crashing stage i would recommend using 10mm x 750mm carbon square tube and you can strengthen them by inserting 8mm carbon rods. You can get this cheap from HK. Surprisingly strong.
Jul 25, 2012, 09:10 PM
Too Many Thread Subscriptions
TheFernMan's Avatar
Quote:
Originally Posted by Stunt Double
Square arms are better for a simpler build. If youre out of the frequent crashing stage i would recommend using 10mm x 750mm carbon square tube and you can strengthen them by inserting 8mm carbon rods. You can get this cheap from HK. Surprisingly strong.
I found the square tube. It says 750x10.5. I don't see the carbon rod
http://www.hobbyking.com/hobbyking/s...idProduct=9012

Is that the correct one in the link?
Jul 25, 2012, 10:57 PM
Registered User
Yes thats the correct link for the carbon tube. Here is the link for the 8mm rod:

http://www.hobbyking.com/hobbyking/s...w_8x750mm.html

Ive been using this setup for tricopters and so far its worked really well. I was a bit concerned about it being too weak but no. The carbon tube can split in a crash but you can fix it up easy with CA. Compared to the wood ive used in the past this stuff is much more rigid and lighter and also you can hide your motor wires inside the tubes too.
Jul 26, 2012, 04:17 AM
Too Many Thread Subscriptions
TheFernMan's Avatar
Thanks for the link, I've add it to my wish list
Jul 26, 2012, 05:26 AM
Registered User
vineet_p's Avatar
Quote:
Originally Posted by TheKnightFerrin
What kind of material are your center plates composed of?
I don't know aht it exactly is, but it's a sort of thermosetting fiber. I cut it out of a student's examination board/pad.

Vineet
Jul 26, 2012, 08:19 AM
Registered User
mamba max1's Avatar
How's the torsional strength for the carbon set up? I'm finally out of the frequent crashing stage.
Oct 28, 2012, 02:53 PM
Too Many Thread Subscriptions
TheFernMan's Avatar
I'm revisiting this.

Most of the higher end multirotors use round carbon tubes.

Anyone know why versus using some square aluminum tubes?
Oct 28, 2012, 03:16 PM
Registered User
malcr001's Avatar
This thread got me wondering, why arent we using square carbon fibre tubing?

I can agree that getting motors level with round tubing is a pain. Especially with the motor mounts I have. The way its designed means that as you tighten it, it slowly rotates around the arm. This makes it harder to level the more you tighten it.
Oct 28, 2012, 03:25 PM
Too Many Thread Subscriptions
TheFernMan's Avatar
Quote:
Originally Posted by malcr001
This thread got me wondering, why arent we using square carbon fibre tubing?

I can agree that getting motors level with round tubing is a pain. Especially with the motor mounts I have. The way its designed means that as you tighten it, it slowly rotates around the arm. This makes it harder to level the more you tighten it.
i have a Talon V2 frame and thats where this started. After i ordered replacement motor mounts, i installed them yesterday and i saw something i didn't see the first time around a few months ago.

when using a bubble level on the motor mount itself and laying the arm with the bracket flat on the floor, i could turn the motor mount till it was level. seem easy but it took a few minutes each arm. something that i didn't have to worry about with square arms.

you could use square carbon fiber arms, but i assume you'll still need arm blocks to mount to center plate and mount the motors.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Brass vs Copper stock/round for ballast Twyl Slope 7 May 25, 2012 10:29 PM
Discussion Square vs. round carbon tubes? Also, how much does brand matter? Cheesehead Composites Fabrication 8 Jan 04, 2012 02:50 PM
Discussion Round Vs Square Fuselage ? RWCLOUD Sailplane Talk 22 Oct 19, 2011 04:56 PM
Discussion Multirotor Construction Question - Arm Attachment Method... bob4432 Multirotor Drone Talk 6 Jul 20, 2010 09:31 AM
Discussion Round vs. Square section JCaste Modeling Science 2 Aug 25, 2006 01:47 AM