Quadcopter: Is this carbon fibre, or some cheap rip off?

johnp

I built a quad from a kit. The product description says carbon fibre.
First day I took it out I got a lot of oscillation on a hover and it hit the ground from about 10 foot. One of the arms snapped so I replaced that and got flying again.
Everything was fine for a few weeks, until it hit the deck again. This time maybe 20 foot up, it was running away from me so I killed it. It hit the ground and humbled a couple of times. This time one of the frame spacers (there is an upper and lower frame) shifted and basically ripped part of the upper frame.

I've attached two pics of the damage. But that's 2 falls and two breaks. Quad are going to hit the deck at some point and I've been lucky with just two since I've had it, but surely the carbon fibre is supposed to be more robust than that?

This image isn't great, I can do another later if it helps.
http://imgur.com/a/3KtcY

You can see the screw has shifted and basically ripped through the frame.
http://imgur.com/a/WjzcZ

civdef

Carbon fibre isn't magic - weak points in a design will be vulnerable to breakage no matter what material used. What frame is it?


One way to test if it's real carbon fibre is to see if it's electrically conductive with a multimeter - real CF is.

johnp

civdef wrote: »

Carbon fibre isn't magic - weak points in a design will be vulnerable to breakage no matter what material used. What frame is it?


One way to test if it's real carbon fibre is to see if it's electrically conductive with a multimeter - real CF is.

Yeah, I'm with you that they're not indestrucible, I was just a little unsure as to it being real CF or not. I'll get the multimeter out and check to see if it's conductive.

It's a RJX CAOS330 bought from Hobby King.

Thanks for the reply.

civdef

The other thing you'll see with quads especially is the bigger they are, the easier they break. Most racers are 250 size or smaller, a 330 is going to bringing a lot more weight to the scene of the crash, usually with bad results.

johnp

civdef wrote: »

The other thing you'll see with quads especially is the bigger they are, the easier they break. Most racers are 250 size or smaller, a 330 is going to bringing a lot more weight to the scene of the crash, usually with bad results.

Well that makes sense too!

I have been browsing about since (in the 250/280 range), so will bear in mind the size and weight.

Thanks.

civdef

I've a few ZMR250s that have got a lot of crashing. Easily the most robust is the cheapest glassfibre "CF knockoff" one. It's a bit heavier than the CF frame, but very very tough.

johnp

ZMR250 is one on my list. It was between that and the EMAX Nighthawk 280. A friend has the EMAX and that's defo taken some falls without a bother.
Looks like the ZMR can only take up to 5" props though and I have a bunch of 6". Props aren't too expensive though, so may bite the bullet.

Cheers

JonoinGurteen

RE: Carbon Fibre. Although I have not made anything from CF in models I used to use it in small sailing dinghys. The cheap part is the carbon, the expensive part is the various resins you can use, and the very very expensive part is (if you can even afford one) is running the autoclave (Oven) correctly. Yes, CF conducts electricity through the carbon, which should not be exposed, but almost always is. CF is extremely strong when used correctly, and the design is for CF. Sometimes you can take a design and just substitute various things for CF, no problem, sometimes you can not.

Like I said, i do not know from models, but drilling CF is BAD news unless done very carefully. The resins are usually of a brittle type and tiny fractures around the hole weaken it. When a hole is moulded into a part, the strand (CF strands) orientation can affect the strength of the hole and surrounding structure.

IN conclusion, the part you have could very well be CF, but not the strongest type of CF / resin, or maybe not the right CF weave for the application..... just my thoughts ..