Hi guys, it's been a long time since my last post here, i've been making frames for the last few months, and i've been learning and having so much fun that i needed to share it with you.
For some time i was obsessed with the idea of a tricopter with folding arms, one which i could carry around in my back pack, and just grab my bike and go for a ride with it. but i kept having the same problem, every time i crashed (believe me I crash a lot) the frame suffered a fair amount of damage in the arm joints, mainly due to the arms being hollow carbon tubes and the hole drilled to join them to the frame crated a very weak point. Then was the issue of weight, having two plates that clamped the arms in place, plus all the nuts and bolts, really effects the weight of the entire setup. A completed frame, without any electronics weighs how much? around 350 400 grams?… too much for my taste, and of course, cuting the wires when folding it...
Then it was the issue of complexity (I'll give it to you, you break an arm or a motor mount, you replace it and go flying again) having all those moving parts and weak points, is a big deal breaker for me. So i said to myself "How about if i loose the folding arms? well i would loose the ability to just put it in my backpack… but it is really that important to have folding arms? What if i make it smaller? well i could loose some stability… could i? after all no one have done a small tricopter they just heard that small tricopters were unstable, no one have actually proved it, after all, today Flight controllers have better gyros and electronics… nahh, what the hell, let's do it!! To the drawing board!!! i said (or in my language "A la mierda! A la mesa de dibujo!) and that is how the Unibody tricopter was born!
3mm thick 310mm carbon fiber body
560 grams total weight with electronics (without the battery)
my setup is as follows:
Sunnysky 980KV x3
Afro 30A x3
kk2 board 1.6fw
hitech servo
10x5 e-props
generic hitech receiver (prety good for a 20dollar knock off)
2200mah 20C battery
It is still an ongoing design, i have a couple of modifications to make it even stronger. Although as it is, takes crashes like a champ, and looks darn cool :)
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What do you do in the case of a crash? One of the advantages of the other more modular designs is the easy replacement of broken arms. Have you done any testing yet to see if this design is more crash-resistant than a standard modular setup? I'd be curious to see.
I'm betting it is more resistant to breakage, but that there is a practical size limit to this design beyond which the breakage resistance falls off due to greater shearing forces during impact overcoming the material strength.
Of course, none of that is a knock on the design. Its gorgeous and for small to mid-size tricopters I'm betting it works amazing.
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So far, the only broken parts, have been some propellers and a cheap servo, the frame itself is super rigid, so takes the beating very good. i have not done a proper crash test, well because parts are very expensive and scarce here in my country, and to be waiting for replacements it is something i hate. but mainly because i'm not rich :p
one of the improvements, is an upper plate to protect the electronics, reinforcements for the frame and some minor adjustments.
Wearyman you are absolutely right, modular designs can be easily fixed, but they are more prone to get damaged in a crash, i'm not saying this frame is unbreakable, but it is very unlikely to get destroyed in a crash, i've crashed it very hard, and it is still flying :) but if it gets broken in a crash, well you're toasted, you will have to replace the entire frame.
for size limit, i found that the 300mm size is the perfect balance between weight, strength and rigidity. a bigger frame would be more heavy and would be more vulnerable in case of a crash, it flex too much.
To cut the CF i used a dremel, a cutting disc and lots of patience ;)
i'm working on a cnc machine to get better cuts though :D
I'll upload the revised plans once i finish the modifications, or if you want i can cut it for you ;)
Cheers
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Can't wait to see what you do with a CNC machine!
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Carbon fiber always looks so sexy. What thickness did you use?
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I found the carbon fiber on ebay, just do a quick search for "Carbon fiber sheet" and you'll get a lot of results ;) i'm using 3mm thickness.
the plans are coming, i'm waiting on my Naze32 to get here to make the final changes.
Cheers
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https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/p526x296/10156010_10152399431058746_7382853278865488289_n.jpg
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