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Old Jun 09, 2012, 01:18 AM
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India, Telangana, Hyderabad
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Question
Carbon-fibre Vs. Aluminium for quadcopter frame

I've made my first quad using Aluminium beams and a central plate... It was pretty strong but was terribly heavy... The frame+bolts+nuts was around 450g!

So this time, I am thinking about using carbon-fibre square pipes (10mmx10mm) as the beams and will use a fiber-glass central plate.

1. How strong is Carbon fibre to use as arms/beams
2. I've heard cutting carbon-fibre is tricky... is it so? Can it be cut just the way aluminium is cut? And how about drilling?
3. I've read that CF is dangerous to health.. is it enough if I wear masks to cover my face while cutting and drilling it or is additional safety required?

Also, is there any advantage in using CF instead of Aluminium? Is it significantly lighter than aluminium?

Thanks,
Vineet
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Old Jun 09, 2012, 04:03 AM
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Sweden Link÷ping
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Hi! I cut and sand carbon in the kitchen-sink filled with water.What I can understand the dust can't get in the air doing so.Maybe I i'm wrong correct me then.

Drilling carbon I use a jar with water and insert a alu pipe or square pipe that have the same measurements as the inside of the carbon pipe or square pipe.Then the carbon pipe doesn't split inside.
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Old Jun 09, 2012, 05:15 AM
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Thanks sjak.
Anymore replies??
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Old Jun 09, 2012, 05:32 AM
recep
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Ankara, TURKEY
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Carbon is lighter than aluminum. But with round carbon tubes mounting clamps add weight actually on my 16 mm boom y6 just mounting clamps add 120 grams if I build a hexa it will be 240 gr And this is just for the frame not legs and camera mount etc. With square aluminum tube you dont need that clamps you can mount motors directly on the arms and centerplates likewise so for a bigger frame carbon is better and more rigid but for a smaller frame aluminium has its advantages. You can use carbon for the center though.
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Old Jun 09, 2012, 05:41 AM
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Thanks recep.

I'll make a 550mm frame.
I've mounted my motors presently on Aluminium beams DIRECTLY.
I'll be using CF square tubes, not round, so I can mount motors directly, as I did on Aluminium.
Thanks,

Vineet
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Old Jun 09, 2012, 05:54 AM
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Hi,

Carbon and aluminium are VERY different materials.

carbon advantages: very light, very stiff
carbon problem: the major problem of the carbon is that it transmit ALL the vibrations. As it's a nonsense to make holes evrywhere in carbon (loosing the stiffness, the vibrations is transmited along the structure with no dampening).

Aluminium advantages: the stiffness of aluminium isn't destroyed by holes you can make along the structure. ALuminium 7075 is having impressive stiffness.
aluminium problem: it's heavier than carbon. In case of shock it will absorb the energy of the impact and will bend. As an aluminium structure is generaly more complicated than standard carbon boom, the replaement part cost generaly more than a simple carbon pipe.

About cutting carbon you can have a look at my youtube channel (catlord21) you will see several videos aout milling carbon fibers.
Cutting carbon is effectivey dangerous for the health. The Áparticules of carbon goes inside your lungs and can provoke cancer on long term range.
The carbon particules are VERY thin and will go thru your mask even with higly filltering EPA14.

The solution to this problem I have found is to force the nanoparticules to go thru water where it will be "glued" in.


Another problem with carbon particules: it's conductive. If you cut it near an electronic device, you can have eletricla problems due to shortcuts.

Cutting carbon isn't just a piece of cake if you want to take care of your health.
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Old Jun 09, 2012, 08:12 AM
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the usually pultruded and shinny chinese look-a-like wooven cfk tubes aren't that stiff related to their weight. You need pure wooven with different direction fibre with a high cfk percentage. They are really hard to find - and expensive. Actually I know only one smart construction, that is light, stiff and uses wooven cfk of good quality. Only negative point is, that it issn't available at the moment but expected for the next month.

Alu Square booms with light CFK centerplates and directly mounted motors are the way best bread today.

EDIT: cfk has two backdrafts. One is the chance of cancer if you breath the particles and second is that they can not carried out from your lungs via breathing out. You need class 3 breath protection and special vaccume cleaner that are able to fiter cfk particles. If you work with cfk under water you have no trouble with the paticles in your environment.
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Old Jun 09, 2012, 08:17 AM
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hmmm... thanks for the replies... i will go with aluminium at a penalty of extra weight..

Thanks.
Vineet
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Old Jun 09, 2012, 08:18 AM
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Use aluminium 7075 or AU4G only
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Old Jun 09, 2012, 08:25 AM
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As catlord point it out, there are different types of aluminum available. Here in Germany, I've found two types at my homedepot. one 10x10 type with 1 mm walls and a 7.5x7.5 with 1.5 mm walls and not so stiff aluminum that is compared to the bigger tubes significant less stiff and have almost the same weight.
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Old Jun 09, 2012, 09:09 AM
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I've found 10mmx10mm square pipes of thickness 1mm. It's pretty hard and four 30cm beams weigh 70g..

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Old Jun 09, 2012, 10:45 AM
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So you just need a really good Centerplate like those from here: http://ng.uavp.ch/moin/Shop. They are made of Aircraft CFK with a very high percentage of cfk and less resin.
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Old Jun 09, 2012, 12:26 PM
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@zerosight

Thanks for the help, but you gave the wrong link.. it takes me to some "freeTibet"
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Old Jun 09, 2012, 03:33 PM
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United States, FL, Melbourne
Joined Mar 2012
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carbon

Quote:
Originally Posted by catlord View Post
Hi,

Carbon and aluminium are VERY different materials.

carbon advantages: very light, very stiff
carbon problem: the major problem of the carbon is that it transmit ALL the vibrations. As it's a nonsense to make holes evrywhere in carbon (loosing the stiffness, the vibrations is transmited along the structure with no dampening).

Aluminium advantages: the stiffness of aluminium isn't destroyed by holes you can make along the structure. ALuminium 7075 is having impressive stiffness.
aluminium problem: it's heavier than carbon. In case of shock it will absorb the energy of the impact and will bend. As an aluminium structure is generaly more complicated than standard carbon boom, the replaement part cost generaly more than a simple carbon pipe.

About cutting carbon you can have a look at my youtube channel (catlord21) you will see several videos aout milling carbon fibers.
Cutting carbon is effectivey dangerous for the health. The Áparticules of carbon goes inside your lungs and can provoke cancer on long term range.
The carbon particules are VERY thin and will go thru your mask even with higly filltering EPA14.

The solution to this problem I have found is to force the nanoparticules to go thru water where it will be "glued" in.


Another problem with carbon particules: it's conductive. If you cut it near an electronic device, you can have eletricla problems due to shortcuts.

Cutting carbon isn't just a piece of cake if you want to take care of your health.
Carbon absorbs more vibration than aluminum. At least in cycling it does. It's one of the major selling points of carbon frames. Can't imagine physics changes that much between cycling and flying.
http://www.livestrong.com/article/86...-carbon-bikes/
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Old Jun 09, 2012, 04:16 PM
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Joined Jul 2009
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Alll of our frames are made with round aluminum tubes for two reasons... aluminum bends instead of breaking and aluminum round tubes are 2-3 times stronger than square tubes. Carbon may be lighter, but its failure mode is to basically disintegrate.

We've had crashes from 50m with no damage to the tubes which only required re-alignment of the base plate (also aluminum) to be back flying again. If the same frame was all carbon or with square arms it would have required a base plate and at least 3 booms to be replaced.

FWIW, one of our quads and our small Y6 design mount the motors directly on the round arms. The bolts maintain the angles just find for small aircraft loads. Requires precision drilling of the arms but that isn't a problem with the right jigs and a drill press.

For higher loads we use plastic PVC clips to attach the motors. Works quite well.

See my blog for details.
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