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Jun 14, 2014, 06:32 AM
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G10 Replacement Arms for iQ450/550 Kit Quad and Hex

G10 Replacement Arms for a iQ450/550 Kit Quad and Hex

This is not exactly a scratch build, it is more like a upgrade to stronger arms on a 450 class quad.

Last fall I got a iFlight RC iQ450 kit quad and I assembled it over the winter.

The kit can be seen here at iFlight's online store,

I had not ever flown a multi and don't fly around anyone that can fly them. But I do know how to fly planes so it was just going to be learn as you go proposition for me.

As I assembled the kit I was having some uncertainty about the controller I was using and sent the quad to a friend in Florida to check out. He set up the OpenPilot CC3D flight controller I was using, checked it all out, and maidened it for me. He reported it to be a nice and easy to fly quad and returned it to me.

When I got it back from Florida I didn't get much flying in over the winter months, we had a terrible cold and long winter in Maine last year. But in the first few brief flying sessions in sub-freezing Maine weather, I managed to break a couple of landing legs off of the arms, and then I broke an arm. I ordered some spare arms and continued to learn how to fly.

By May winter was pretty well over and I started getting more time with it. I made a You-Tube video of one of my early flying sessions with a hat cam, it is nothing special other than you can see the kind of abuse the quad was taking.

By the time I had 15-20 flights on it, three of the four landing legs had been replaced with cable tie loops and I eventually accumulated five broken arms. And all of them broke in the same place, at the thinnnest spot in the arm where it rounded out to form the motor platform. A typical break can be seen in the images.

I attribute the breakages to a combination of cold weather making the plastic brittle and to my beating it up pretty good in learning how to fly it. Most of the breaks were when it struck ground hard and out of control and an arm took the initial shock. But the broken arms were getting annoying.

I decided to make my own arms out of G10 fibreglas sheets. I made one pair of arms out of 1/16" thick material and it was too flexible. The arm would flutter under power. So I got some 0.09375" or 3/32" material and gave that a try. And that worked fine. No flutter and obviously not going to be an easy arm to break.

I cut the arms on a 25W Mercury II laser engraving/cutting machine. Which is another story all in itself...

But to cut to the chase, I eventually got two prototype G10 arms made, on the quad, and flew them a quite a few times. By this time I'm flying regularly and well enough that I can fly in the yard at home and the arms are working very well and taking the abuse I was dishing out.

So I made up a set of four new arms and replaced all the arms on the iQ450 with the G10 arms.

Last edited by jackerbes; Nov 29, 2014 at 12:21 PM.
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Jun 14, 2014, 06:57 AM
jackerbes's Avatar
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The numbering of the paragraphs below is keyed to the numbers of the images.

01 - The last arm I broke is seen in the image and that is where all of them broke. It is cracked all the way through where it is bent up and just hanging by a thread. Also seen are the new arms I cut from the 0.093" G10 material I bought on eBay.

The 3/32" G10 material only cost $4 for a 12" x 12" sheet or about $6 a sheet with shipping. That seller will ship up to ten 8-10 12" x 12" sheets for the shipping charge mentioned there (it is the cost for a Priority Mail Mediam Flat box). I made up a drawing for a plan and found I would be able to cut up to 8 arms from a sheet. So the economics of using the G10 material was very good.

The laser cutting process leaves a blackened heat affected zone (HAZ) where it cuts and that is seen as the darkened edges and around the holes. The edges were cleaned up by sanding and the holes (cut a little undersized) were drilled out to 1/8" (3.175mm) for the 3mm screws that would be used. Also seen are the frame plate spacers that were made by cutting the ends off of broken arms.

02 - As you can see from the two G10 arms that are on the frame, the new arms will be added atop the frame plates. In the image are the prototype arms, one original arm is still in pace, and one arm has been removed.

03 - A close up of the spacers and the new arms is seen and the old broken arm too. The pairs of holes along the length of the arm are for the cable ties that will hold the ESC to the arm and for fastening the motor leads and cable tie loop landing legs to the arms.

04 - The arms have been cleaned up, the edges sanded, the holes drilled out to 1/8" and chamfered to take the sharp edges off, and the arms are ready to mount. The arms can be turned over to changed the position of the motor leads relative to the arm. I tried them both ways, found the side up that would get the leads most direct and atop the arms, numbered the arms to get them in the right places on the plates.

05 - When the arms were cut I used the laser to make motor mounting holes on 16mm, 19mm, and 25mm centers so as to allow for the most versatility in using other motors. The iPower iBM2212Q 1000kv motors I am using have the standard 16mm x 19mm pattern for mounting screws. The larger 8mm center hole allows for clearance on the shaft end and also for lubricating the bottom bearing.

06, 07 - The ends of the arm were cut off with a hack saw and sanded to be even with the edges of the frame plates.

08 - The spacers were put in place, and the new arms mounted with two screws. The iPeaka 30A SimonK ESCs were located on the arms. The arm at the lower left is one of the prototype arms and it will be replaced with one of the new arms.

09 - The frame was turned over and the screws that hold the frame spacers (end cut from broken arms) put in place with blue Loctite on them. As a friendly warning, never use red Loctite unless blue has failed to work. And if you want to lose screws in flight or find them loosening frequently, you can skip the Loctite.

11 - At this point the motors are all in place, held with four screws in the 16 x 19mm holes, the screws got blue Loctite, the extra length of the motor leads is formed into an "S" bend and held in place with another small cable tie. The ESCs are held in place with a single small cable tie around the ESC and though the pair of holes that is beneath the ESC.

12 - A close up of the top frame plate with the four arms mounted. The screws used were 3mm M3-0,50x10mm hex socket button head screws from the local hardware store.

13 - The frame spacers are in place between the frame plates.

14 - Landing leg loops are made from large cable ties and held in place by the cable tie holding the motor leads down and a nother pair of cable ties through the 25mm center to center motor mounting screw holes. It is not seen in the photos but also made a pad from from a piece of pool noodle foam tube that is attached to the bottom of the lower frame plate. When the quad is resting on the cable ties, the pool noodle material is just clear of the ground and will also help distribute and absorb landing shocks.

There are some very small spots on the bottom of the lower frame plate that are electrically conductive and have the battery voltage on them from the power distribution system built into the lower frame plate. So the pool noodle also provide some protection against accidental shorts in the power distribution. The frame plates are actually pretty well designed and have worked very well.

I try to fly off of grass as much as possible for the more gentle landings but the cable tie landing loops do a nice job as far as absorbing shocks and keeping the quad up out of the grass and weed a little.

15 - And that's it! It is ready to fly! When the rain stops and the winds die down...

Jun 14, 2014, 07:02 AM
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This image is the dimensions for the arms I made. The hole spacing is for the iFlight RC frame plates and arms, I don't know if it will work for any other quad kits or frame plates.

As I mentioned earlier, cutting the arms with a laser cutting machine can make a nice looking and serviceable arm. But there was quite a learning curve for me in getting the arms cut. It takes a fair amount of time and numerous cutting passes at varying power levels and cutting speeds to get an arm cut out. And some time is needed to clean up the edges of the cuts and the soot that accumulates in the process. I thought the owner of the laser cutting machine might be interested marketing the arms but the labor and machine time needed to cut them is such that the selling price would have to be too high.

The arms could be cut with a CNC router or simply by hand and eye with power tools or even a manual saw. The G10 material is tough and light, that is what made it the choice here. These arms are are a little lighter than the arms they replaced, it saves a total of about 2 oz. or 57g on this quad (it flies right at 1000g as seen in the ready to fly image).

So now I have myself a nice "industrial strength" quad to play with!

Nov 29, 2014, 12:30 PM
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And the arms work well on a hex too!

I have also converted a hex to use the G10 arms now and it is working as well as it did on the quad.

I have yet to break or even damage a G10 arm and there is no weight penalty on these arms. They work out to almost exactly the same weight as a stock arm.

The cable tie loops did not work out well for landing legs as winter arrived here in Maine. The became brittle in the cold and were easily broken. I have since worked out a different style of landing leg that is proving much less fragile.


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