Aluminum arms for dji flamewheel frames

Maymidroix

Maymidroix

Member
Hi everyone,

I'm a senior mechanical engineering student and I started flying multirotors early this year. I bought a DJI flamewheel 450 becuase it was very cheap and found that it was a good frame to start into multirotors. Something that I hated about it was that on every small crash that I had, the arms broke. Then I had to spend about 20 to 30 minutes replacing the plastic arms. Yes, the plastic arms a very cheap but spending that much time replacing the arm was a waste of time for me. So I thought about designing an aluminum arm that will not break or get damaged as easily as the stock arms. Having that in mind, I designed these aluminum arms. The are made using CNC machining and will have red and black anodized finish for orientation. They fit perfectly on the frame plates, they have the same thread size as the stock ones, so no modification is needed. They are 50mm longer to improve the flight stability. I added 3 holes on the motor side to have the option of adding a second motor mount for an X8 configuration.
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Luckily, I was living very close from the warehouse of ReadyMadeRC. I went there with my computer and showed my design to Tim (owner of readymaderc), and he like it, so he agreed to sell them.
Here are some pictures of the prototype arms on my quad:
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On the first flight with the arms I noticed the improvement in stability and control because of the extended length of the arms and because they are very stiff.

After about 2 months since I had the idea, they are now posted in www.readymaderc.com http://www.readymaderc.com/store/index.php?main_page=index&cPath=76_155 They'll be in stock in about 2 weeks so you can pre-order them now. I only made an small batch so they might sold out fast.

Please give me your feedback about this.

Thanks,
Michael Maymi
 

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Brainstorm

Member
Michael: I like the idea of machined aluminum replacement arms for the DJI FlameWheel frame! They look very nicely executed. And it's good to see that you found a way to produce them and offer them up for sale.

Do you have any plans to offer a smaller version of these arms? I am currently building an F330 frame, as a smallish fun flier. So the F450 and the extra length of these arms aren't for me right now.

Have you considered designing and offering aluminum center plates, in addition to the arms? While people are at it, they might as well go all-aluminum. :tennis:
 

OneStopRC

OneStopRC

Dirty Little Hucker
Did not see a weight comparison to the originals, weight is everything in this game!

$119 for 4 of them..... ouch. One thing I have learnt with the plastic ones, they do have some give in them and will spring back to shape, I know from experience aluminum will not do this.
 
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Maymidroix

Maymidroix

Member
EarthCopter said:
Michael: I like the idea of machined aluminum replacement arms for the DJI FlameWheel frame! They look very nicely executed. And it's good to see that you found a way to produce them and offer them up for sale.

Do you have any plans to offer a smaller version of these arms? I am currently building an F330 frame, as a smallish fun flier. So the F450 and the extra length of these arms aren't for me right now.

Have you considered designing and offering aluminum center plates, in addition to the arms? While people are at it, they might as well go all-aluminum. :tennis:
Click to expand...

I designed the arms for the 450s because there are a lot of them out there but I can easily adjust the design to be smaller to fit the 330. It depends on the market.
As far for the center plates, I have not considered using aluminum because I think that carbon fiber will be a better option and can be cut using the same process as aluminum. A one piece carbon fiber arm will be way more expensive than the machine aluminum arm but with the plates the only difference is the material cost.
 

Maymidroix

Maymidroix

Member
I know is not cheap but if you have been around in the RC hobby you'll should have seen aluminum CNC parts that are a lot smaller than the arms and they even cost a lot more. Just look for helicopter cnc aluminum parts. I worked hard to produce them at the lowest price possible in the United States and after quoting with different suppliers, I found one that made it possible. CNC parts are very expensive but the final product is great. Plastic might spring back if the stress was not enough to pass it's yield point and with my experience the yield point of nylon is very low compared to high quality aluminum.

View attachment 13418
I used a finite element analysis software to find the weak areas of the arm, I added material on those areas and remove some where it was not necessary. I used a 20 lb force and the results where pretty good so they will support more than that before yielding. I have not measure how much force it takes to break the plastic arms but I bet you can easily break them with your hands, my aluminum ones you can't. I crashed my multirotor already, ( too bad I was not recording) and basically everything broke but the arms. It was kind of funny because I really did not wanted to crash it but there was some failure with the controller. I was impressed myself that the arms where in perfect condition considering of how hard the crash was. Give them a try, you won't be disappointed.
 

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bruce365

Null
Hi I am impressed, a very good design. DJI originals weigh in at 55.3 grams (215mm long) if one were to add extra length, say another 50mm of polyamide that would probably add another 12 grams, TOTAL = Say 68 grams per leg Max.

How much do your arms weigh? Edit - SORRY just noticed at ReadyMade RC weight = 68 grams, comparable to DJI arms of same length.

I would agree that you would improve flight stability, not only because of extra length, but also arm rigidity, the polyamide arms are too flexible.

DJI arms cost me about $4.00 each, in a crash, a lot of the time the legs will break (1 or 2) and they are cheap and easy to replace.

With very strong aluminium they may bend or not, but the impact energy is then transferred to the plates, the plates will break and the work involved in changing them is considerable (especially the bottom plate).

Not trying to be negative just stating fact and I applaud your skill / determination to produce a better arm. I for one would like to try them on my Discovery.

Regards - bruce
 
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SMP

SMP

Member
Im in the same boat.. I break arms all the time and prefer it that way. What i DO like is the coax motor mount. Would that coax motor mount work with the regular arms and just hack away the plastic landing bits?
 

Maymidroix

Maymidroix

Member
SMP said:
Im in the same boat.. I break arms all the time and prefer it that way. What I DO like is the coax motor mount. Would that coax motor mount work with the regular arms and just hack away the plastic landing bits?
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The optional coax motor mount will be only available for the aluminum arms. You might have to do a lot of modification on the plastic arms but I'm not sure if it will work.
 


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brantdw

Member
I like the arms. How are they under verticle stresses. Also why are so many people crashing their F450s? Crashing should not be a normal every day thing. Im just wondering if Im missing something there.
 

Maymidroix

Maymidroix

Member
brantdw said:
I like the arms. How are they under verticle stresses. Also why are so many people crashing their F450s? Crashing should not be a normal every day thing. Im just wondering if Im missing something there.
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The picture provided on the description is under vertical stresses. Is not only about crashing, it's a good advantage that they are more stronger, but the biggest advantage is the increase in stiffness over the plastics arms. This makes your multirotor to fly more stable and you'll notice a big improvement flying on windy conditions.
 

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AboveAllAP

Member
Just ordered my set... i just crashed mine a couple of days ago and needed a few arms so good timing... lets hope this improve the flight handling
 


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bruce365

Null
Hi MAYMIDROIX, I would like to know how tough or hard these arms are. Which grade / series of aluminium did you decide to use, are you precipitation heat treating these arms to improve strength or is it just run of the mill aluminium that is purchased at ones local store?
regards - bruce
 


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RobertsUp

Member
I was previously aware that those arms existed and I want them for my F550 build. Will you continue to make them into the future? I'm not in a hurry to preorder. I had hoped that I could buy four in anodized black and two in anodized white. The extra length means that I won't have to buy more AMP arm extensions. Will any motor attach to your arms? I hope your endeavour will be successful.
 

maxwelltub

maxwelltub

Member
Hey highgain, on your 450 x8 can you elaborate on how you put the second motor mount on? Looks like its just two screws? any details would be great.
 



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