|Jan 27, 2013, 06:11 PM|
Captain 3D Presents...Folding quad build
After a few questions regarding a scratch built quad I was selling I promised to do a build log for the next one. So here it is.
My Quad requirements are quite specific to shooting with 3D Gopros (two Gopro cameras side by side). This makes the body a little wider than you may need but hopefully there is still a lot for you to enjoy from my build.
My ideal Quad:
Carry 3D GoPros
10 min flight time
Jello Free video1080 at 30 fps
No props in view for Medium 127º FOV
Minimal Props in view at Wide 179º FOV
50% throttle to hover
Folding to fit in carry on luggage
Good separation between FPV antenna, Rx antenna and GoPros
This build addresses all of these points. It is a heavy quad at about 2.2 KG with all the gear on but it works. Here is the result...
(watch in 2D or 3D using the 3D button when playing)
|Jan 27, 2013, 06:44 PM|
The power system:
I spent many many hours playing with...http://www.ecalc.ch/xcoptercalc_e.htm
...trying to find the best combination of parts for my quad. Along the way I learned a lot about balancing motor size with battery weight with props etc. As I knew my final weight would be around 2.2KG that was my target. I came up with this list of parts...
AUW - 2.2 KG
Flight Time - 10 mins
Motors: Tiger AT-2216-6 1250kv (or the cheaper SunnySky x2216 1250kv)
For some strange reason the Tigers are impossible to find in the US so I order from...
The SunnySkys can be found here...
Props: APC 10 x 4.7 Slowfly
Great, medium priced props. They never break in flight. They give a lot of thrust for the diameter. You would need an 11" Graupner to match the thrust.
Buy in bulk here...
ESC: 30A are need for this load. I like the Simonk flashed version available at RCTimer...
Battery: 2200 mAh 3s 20C x 3 in parallel
This may seem like an odd way to do it but if I don't have the GoPros on the Quad I fly with two batteries to get the balance right. Also the 2200 mAh are the best value at $10 each...
Flight controller: Many choices here. I am currently using a CopterControl 3D and a (Guai GU-INS for GPS features). What you choose is not critical to the build.
Lets add that up...
4 x Tiger motors = $160 ($80 for the SunnySky's)
4 x Props = $12
4 x ESC = $50
3 x Battery = $30
Wires, Distribution board and connectors = $10
Flight Controller = $100 ($25 - $500 really, depending on what you buy)
$362 so far
|Jan 27, 2013, 08:31 PM|
I wanted a stiff, light folding frame. big enough for the gear I need to carry but small enough to fit in carry on luggage.
I worked out the over all dimensions and pivot points in a 3D modeling program (Maya) using simple shapes (Pic 1).
Edit: The pic shows 580mm motor to motor but I made my arms a little longer and ended up with 590mm just to give a little more prop clearance.
I animated the components in software to make sure the pivot points would work. Here is a video example of what I mean. This video is of an old design but demonstrates the idea of animation checking...
I then took the wire frame image into photoshop and created the rough body plates as an overlay (pic 2 & 3)
I also needed a spacer layer that would double as the leg lock position as well as provide the stiffness when bolted together (pic 4).
Once I was getting close with the design I took it in to illustrator to finalize the shape and create lines as paths incase I wanted to have it laser cut (turned out to be too expensive). I have inclosed all the final drawings in the zip file below. Also see pics 5, 6 and 7
Pic 8 gives the over all dimensions of the plates.
Coming soon: Cutting the Ply
|Jan 28, 2013, 06:39 AM|
United States, MI, Haslett
Joined Mar 2010
Great stuff! I was wondering what the trade-offs are for using straight arms in a true H configuration. It seems like the advantage is that you could make the center section lighter and simpler because the load is carried in the arm from one side to the other rather than in the center section and it is simpler to build although not foldable. What are the other disadvantages.
|Jan 28, 2013, 12:45 PM|
you could save 17 grams a pack straight off with these batts for an extra $1.25 each pack
51 grams off, gotta add up to some more time in the air?
|Jan 28, 2013, 12:57 PM|
|Jan 28, 2013, 12:58 PM|
|Jan 29, 2013, 12:08 AM|
Great. Happy to hear how it goes. I cut some wood tonight...
Cutting the Plywood plates:
Plywood comes in many forms. The stuff down at Home Depot or Lowes is pretty rough and only good for the center spacer layer. The spacer layer is 12mm (1/2 inch) birch ply. It is slightly thinner than the 13mm aluminum legs which is important because this difference is used to tighten the plates together pinching the legs and making them stick in place.
The top and bottom plate should be cut from the best quality birch ply you can find. You can get reasonable 3.1mm/1/8 inch ply at 'Michaels' crafts store. Or have a search for Revel Birch plywood on ebay etc. Or you can go upmarket and by aircraft grade birch ply from places like Aircraft Spruce...
I am using the 3mm Finish Birch from Koskisen. It has six layers of birch in that 3mm thickness which is almost twice the amount of the Revell ply with three layers. This makes it very stable in all directions. It costs about $32 for a 2' x 4' board that would give you three sets of quad plates.
I print out my template and glue it to the plywood with a some spray adhesive, roughly jigsaw out the pieces then do the fine cutting on my newly acquired second hand scroll saw (Dewalt DW788). I love this saw. Of course you could cnc it or laser cut them for even better results.
My scroll saw skills are improving but far from perfect...
It took me about two hours to cut the three pieces and they weigh 310g together.
(Legs and assembly next)
|Jan 30, 2013, 12:18 AM|
United States, WA, Marysville
Joined Nov 2003
Looks killer! Thanks for sharing. I really like the design. I run a cad program all day so I can appreciate the elegant work. I especially like the space plate.
Keep the info coming!
|Jan 30, 2013, 12:26 AM|
Another night another quad frame. First I made a small jig for cutting and drilling all the aluminum arms. I am using 13mm square tube like this...
My legs are about 220mm long but you could probably get away with 200mm which divides better into the available stock. You would just have a shorter length inside the plates.
Next I took the top and bottom plate and drilled two holes in each and temporarily bolted them together while I drilled all the other holes so alignment will be perfect. I like to drill the whole slightly under sized for the bolt so that they will 'screw' into the wood as it all tightens down later. This guarantees stiffness as the pieces can not slide around the bolt.
Two holes were then drilled through the spacer layer so I could hold all three together with bolts before drilling out the remaining holes in the spacer layer. I drilled half way into the spacer layer from each side to make sure alignment stayed true.
Once all holes are drilled I put bolts through each one without any nuts but even that makes the frame stiff.
The arm pivot bolts are slightly larger and I add a block of ply top and bottom for extra pivot strength. I glue the blocks down with wood glue as I tighten these pivot bolts in place. With all four arms in place with the pivot bolts you can check everything pivots correctly.
Now add washers and lock nuts to all the other frame bolts and tighten the whole thing down. Now it is rock solid and super stiff. The bolt between the two pivot bolts can be tightened until the legs feel just right for a friction fit.
The frame is complete and ready for all the other hardware. It is not the lightest at 445g but this is a quad that will carry a lot of gear. It could easily be trimmed down for single GoPro use and shed some grams.
See the final pics for its folding legs...
Does anyone want to see any more? Not sure if anyone is reading. If no one replies I am editing this last line out :-)
|Jan 30, 2013, 12:27 AM|
|Jan 30, 2013, 03:18 PM|
Awsome ! Thanks for Posting your Creation
Didn't mean to just Lurk, but Thank's for sharing your ideas and confirming my suspicion that Multiply Finnish Birch Ply can do just as good as G10 & CC at less $, and easier to work.
|Jan 30, 2013, 03:45 PM|
United States, MI, Haslett
Joined Mar 2010
I am having trouble finding a source for good plywood. I bought some square towel rack replacements at Home Depot that look strong enough for arms and they are just slightly bigger than the width of 3 sheets stacked of cheap Home Depot luan plywood . On the top and bottom plate the best I could find was some Baltic birch 1/8 inch from michaels for 3.99 for 12x24. The plywood is a little warpy. I guess I will use 4-40 bolts. I think for my first run I will just use this cheaper stuff and see how it turns out.
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