Quad Rotor ver 2 - RC Groups
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Sep 14, 2012, 12:07 PM
The Engineer
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Quad Rotor ver 2

Its all starts from here.

The arrival of the CF parts in March 2012:

But only in Sept I started working on this.
100x300x1.5mm sheet cut into 100x100. That's how small I like it to be to keep weight down.

The usual, 4 corners with holes, act as pivot for the boom too. Make last minute change to include a swing-close design.. had to drill many holes and file them to shape.. not very nicely done.. had to oversize them to get a smooth swing.

Then the booms' holes are drilled too..

Now to the other end of the boom now, the motor mount design. I know we can buy something like that and get it fixed but that won't be fun anymore. Since I have an odd size CF sheet after cutting out 2 pc of 100x100, time to use it anyway. Of course it can fit only 3 here.. the 4th will have to use the new sheet.. And weirdly, the mounting is in triangle geometry.
I drawn it out using Autocad and printed out on paper before gluing it onto the CF sheet with latex glue. Easily remove by peeling off when dried. Leave no trace.

The motor to be used this time will be the AX4008

Drill and file.. And after that time to saw them apart.. Too bad don't have a band saw or swivel saw.. a lot of effort..

Mechanically, if the 'wrist' is squared to the palm holding a heavy motor that is continuously vibrating, the wrist will break given time. So time to make last minute changes before cutting. I decided, make it round, add a quadrant to strengthen the structure.

Final check, fit.

Finally cut out:

To be continued..
Last edited by prodriverex; Sep 16, 2012 at 08:02 AM.
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Sep 15, 2012, 10:36 AM
The Engineer
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Update 15/9/12

Completed all 4 mounts today..

Now getting to plan on the copper board to wire up the ESC and battery input..
Sep 16, 2012, 07:01 PM
but thats not soon enough
ahh, the time spend filing carbon sheets. fond memories :P
very nice build. looking forward to updates
Sep 17, 2012, 05:11 AM
The Engineer
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Saw this great tip about prop balancing especially if you are building one craft for AP.
Unbalanced prop causes the video to show waves literally..

Flite Test - Laser Balancing Props - FLITE TIP (7 min 11 sec)
Sep 17, 2012, 03:48 PM
Registered User

I just started a carbonfiber build today myself.. and i'm completely new to CF..

What did u use to cut the sheet?? a jigsaw??
And is that just paper wraped to minimize flushing the edge??

Sep 17, 2012, 08:21 PM
The Engineer
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I use masking tape so it is easy to see the marking. It's pretty fine even without and the edges will still be good, it won't cause chafing.

For longer edges, I use jigsaw. Short cuts, a junior hack saw is fine. For smoothering, I use various files, I have a tungsten carbide file bot from carbon mod UK for large filing. Fine edges I use a small very small file which looks like nail file and I dunno what make ot was, looks to me like tungsten carbide too. I realise the normal metal file doesn't cut much..

Surprisingly the CF sheet is pretty easy to cut thru like a acrylic plastic.. just that the powder from cutting is very fine. So take care to contain them, don't let it spread around. They can coz itch for some peep but I'm fine with them while working with or without glove.
Last edited by prodriverex; Sep 17, 2012 at 09:14 PM.
Sep 19, 2012, 08:18 AM
The Engineer
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Electrical Work

Now that the frame and motor mount and motor is done.. time to move up the base and think of how to mount the ESC.

My design believe in having a low CG and all components should concentrate to the middle as much as possible. Even my base plate is very small at 100x100mm for a 750mm Quad.

So to reduce wire and cable clutter, I want to formulate my own PCB to carry those power.

So the idea came from http://hackaday.com/2008/07/28/how-t...gle-sided-pcb/

Its interesting to learn that one can laser print onto practically any flat surface, literally.. But instead of meddling with pungent chemicals, i decided to adopt my own method..

Here's the PCb plan on drawing:

S that means, we can employ the same manner to transfer these lines onto a sheet of copper! Voila!

But which paper or foil to use? I suppose using the aluminum foil looks better as I can see how the print out will turn out.. But before I can do that, I think it may sense to reverse the color like this:

Reason is simple. the track should be clear of any printing so we do not need to clean it off later. The portion to be cut away will be printed instead.

Then off to print direct onto the aluminum foil.. I tried out both dull surface and shiny surface, the effect is the same..

Now cut away those tape that held the foil to the paper and remove slowly taking care not to crisp the foil. I realise to print it very nice, always use a super nice and flat foil without any lines.. try.. The foil i had in hand was a lousy one, it was thinner than usual..

Now slowly flip it over and lay the foil with the printed side, down to the copper sheet. You can see the print did almost an embossing on the foil.. this is before ironing..

Tips. Now, you gonna move that iron around so better tape down the foil too. But do not use plastic tape. I happen to have aluminum film tape so it came in useful..

Then I place the sheet on a flat surface like an acrylic sheet top with a thick but firm cardboard.. I lay a smooth cloth like a shirt over it so that my iron can slide smoothly..

Turn the iron to the hottest and lets do it!

After 3-4 minutes of moving the iron around making sure it covers all the area..
Remove the hot iron.. remember to turn it off.. wait for the copper sheet to cool.. you can put it in front of a running fan to cool it faster..

And once cool enough to work on, peel the foil away slowly.
Here's are the results:
This is with less than idea flat foil without lines..

This is from a nicer foil, almost perfect without lines.

You can see the importance..

I will cut the bull short, than i just trim the printed portion with a big strong pen knife..

To be continue..
Sep 20, 2012, 08:04 AM
The Engineer
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Did some electrical work today..
Manage to solder extension wire from the motor to the end of the boom.
I don't have any 20AWG cable in hand but manage to find something thicker like 17 or 18 AWG.. (no marking).. but they are tinned strands cable which is good.

I hope the tunneling of these cable (3 of them) through the boom tunnel would be easy but it was not.

In order to keep all cable diameter as thin as possible even at the joint for the extension cable, I did not use overlapping wire soldering. Instead, I line them end to end like a water pipe extending to another of the same size. Using my skill to flow the solder over both and cover it equally. it should be strong and with heat shrink protecting them, they should be good.

Now the trouble is to pull all 3 cables through the 10mm square rod with round hollow. Don't forget I have M3 screws punch through at various point in the centre.

Edit: I include the picture herein for your viewing:

I tried first to pull 2 cables through, then make sure all the screws goes through with both being squeeze to one side of the screw. i have to pick the cables from the other end of the screw hole to make sure they fall at the right place before pushing the screws in all the way.

Then i thought how do I pull the third cable through? I tried pushing in from the motor side alone.. It crumble by the time it reaches the middle of the boom. Next I tried pushing a small size shrink tube through to the other end so that I can pick up the cable after shrinking it, and pull it through. With one side I push. The other end with the heat shrink tube I pulled. It was risky.. There are 2 screws in the middle meant to secure the landing skis by now already screwed in all the way and locked in place by nuts. I have to unscrew these and loosen a little so that i give some space for the 3rd cable to pass through, though on the other side of the screw. Phew, i saw the end of the shrink tube and the cable after some tussle.. just when it protrude out a little like 3mm, the shrink tube snapped..

Oops, lucky i got some 5mm already out, and I just use a plier to pull the rest out.. not so nice.

I tried the 2nd boom these time with 2 cables pushed through the rod at the same time.. That of course is easy.. The challenge is now to make sure they do not criss cross each other while inside.. I have to straighten the cable a few times to get them as perfect as possible. As I look through the hole from one end with light shining through the other, I can make it out that these 2 cable laid flat on one side of the tube. Holding them tightly in place, I push the 3rd one through, this time without the screws.

Once all 3 are through, I slowly use a pick/micro round file to go through the hole that I'm about to put the screw through. i separate the cables so as to create space in the middle for my screw to go through.

Edit: picture added:

Each time the screw pass till halfway point, the last cable often get push so that it covers the hole a the other end. Now I use a small hex-head driver (M2.5) and push the blocking cable to the side, flattening the cable but that's fine, they are elastic.. Finally I got the screw through.. then I follow through this method with the remaining screws.. they work fine.

After this, I check for short circuits but there were none! Alright, I shall do this then.. i decide to take a break and do the end of the cable..

Edit: I tried another method to keep the cable pair flat and straight using masking tape... This works like A charm:

I remember having suitable size nylon sleeve.. so I tried using them to protect the edge where it turns upward through the baseplate.. The hole is a 12mm..

Alas, after I did all these, and pushing both cable through, I realise how tight around the 12mm hole they were:

Look how tight the cables are within the hole!
Now, make the hole bigger? Or make 2 more smaller hole nearby? Remember the booms are movable for transportation..

Edit: I have make the centre hole bigger, to 16mm now.. enough room.
Last edited by prodriverex; Sep 20, 2012 at 10:53 PM. Reason: added new pictures
Sep 20, 2012, 10:24 AM
The Engineer
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More pictures from today..

Love the cleanliness of the cable management this time.

Probably more aero dynamic too..

If there's a lesson learned here, is that the motor mount screw shouldn't be so near the edge of the end of boom. I need to cater clearance for wire entry while split between the first set of screw.

Last edited by prodriverex; Sep 20, 2012 at 10:55 PM.
Sep 20, 2012, 11:26 PM
still cant figure out how people use those HK square tubes for quad arms w/o cracking them
Sep 21, 2012, 12:16 AM
The Engineer
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Now that you got me concern.. maybe I should patch them with some carbon fabric to strengthen them.
Sep 21, 2012, 12:24 AM
not hating on your design (looks very nice ), but CF tube is the best with boom clamps on the fc plate. mine always cracked at the center plate but never the motors mounts.

yeah that might help or maybe a aluminum square tube that fits snugly over the CF sq tube for just around the center plate part of the arm then drill the holes through that too. and finally bolt all that like you have above to the cf plate.
Sep 21, 2012, 01:48 AM
The Engineer
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If you look at the rod you will find a straight line running down the entire length of the rod on opposite side.. that must be the forming edge. Could that be the weak link? Was kind of surprise when it first came in, it does not appear as weaved CF fabric like those round tube. Only realised its just I don't know what you call it, linear laid fibre, after some strands starts to pull apart from the drilling. Too much pressure I guessed. So I took my time to drill them..
Sep 21, 2012, 04:29 AM
The Engineer
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Assembled the frames with motors and cables finally. Weighs 577gm with each motor at 79gm, CF baseplate and booms at 160gm. Rest of it goes to cable, screws, nuts and washers.. wait, the ski is not up yet..

Sep 22, 2012, 10:56 AM
The Engineer
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Hole puncher came in useful for this work, exactly at 5mm.

You will know the use later.

Getting down to mixing the epoxy.. I got these from Carbon Mod UK as a kit set. Been useful.. You can get any other one of course.. After few mixes as it keeps drying up, I got the hang.. 2:1 as it is clearly written, one is a hardener.. surely you dun need 2 parts of hardener.. So its the other way around.

The acrylic sheet (2mm for this one) is usually wrapped with proper sticky paper on both side. So I peel off one side first without touching the other side. Gonna glue this +ve and -ve plate to the acrylic first as they are larger in contact area and so easier to work with.

Once the ratio is correct and stirred, make sure the bubbles are gotten rid of as much as possible. I use ice cream stick to stir and to get rid of the bubbles, simply keep pressing the mixture against the side of the cup..

Started pouring onto the acrylic now and get enough to work on.. more is ok.. just overflow the sheet.. sweep it down the side.

few minutes and its done. not too thick.

Then just place the copper sheet down. With the slippery epoxy, the sheet can be move around for sometime..

One tip, after cutting the copper sheet to shape, put it another a flat surface like a concrete floor, place piles of newspaper on it to flatten it.
If you have a glove on, just push the sheet everywhere to make sure it is flat on the acrylic. Mine was not totally flat.. so i have to find ways to keep the sheet pushed down.. until it is tacky enough then remove the weight.

After placing the sheet down, dip the brush with more epoxy and go through the top of the copper sheet again to get a layer on top of it. This will act as protection again short circuit.

Next come the use of the punched holes.. these will be used as contact surface to the other side of the PCB.

Tip: Just use a tweezer to move it around. I have the dimension and placing of the whole PCB design printed out in transparency. so use the transparency as out lay and shift the 'dots'. Accuracy is not all too important here as long as the bullet connectors touches a part of the copper, solder will stay onto the copper area to secure both top and bottom side.

Once it is dry enough, use a sharp wire cutter to snipe off withholding joints which is there for the purpose of making sure both stripes of copper stay in same gap through out.

Here's how it look after sniped off.

Don't worry about the unevenness. Have to 'paint' over another layer later.. Also, the portion sniped off will be ugly. Have a tin or a cup or a bowl of lacquer thinner ready on hand for washing of application brush and that stirring ice cream stick.. dip that ice cream stick into the thinner and lightly thrown a few time to make sure it is not dripping. tap the stick onto the surface that was sniped. Let the thinner melt away part of the the epoxy and let it set together. The pox surface will be smooth again..

Here's the dried progress.

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