Replies to This Discussion

3D RoboticsPermalink Reply by Chris Anderson on December 9, 2012 at 7:55pm

If all you want is a RC quad, there are many choices, but the DJI Naza with is easy to use and reliable and the Phantom is RTF. But if you think you will want to upgrade to autonomous missions (full UAV), our own ArduCopter is the best choice. 

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Permalink Reply by Stephen R Mann on December 9, 2012 at 10:10pm

I bought the 3DRobotics hex for aerial videography.  The hex gives me more lift for carrying a camera gimbal and possibly a small DSLR.  The Arduopilot flies better than me (but I am still learning).

Whatever you buy, get extra props, maybe a spare motor or two.  If you are new to multi rotor flight, you will crash while learning to fly.  The radio is something you do not want to trim the budget on.  

I haven't added the receipts, but so far I have about $1,000 into my hex including a lot of props, two motors and replacement arms.  Also budget for batteries and a balanced charger.  

My specs:
ArduCopter HEXA 3DR-A Frame
APM 2.0 Purple Full Kit Assembled
Motor AC2836-358, 880Kv
ArduCopter ESC 20 Amp
Propellers: 12X45 EPP Style
MB1200 XL-MaxSonar-EZ0
3DR GPS uBlox LEA-6
Firmware: 2.8.1
Mission Planner: 1.2.17
Radio: Spektrum DX7
Empty Weight: 1800gm

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Permalink Reply by Patowski on December 28, 2012 at 1:08pm

Hi Stephen, Chris, Lewis,

I was just starting a new topic and I found this one very helpful!

 

Im trying to start a project and Im trying to establish a budget and I have some questions:

• the 3DR ArduCopter Hexa-B Frame + Motors + Full Flight Electronics Kit costs about 520USD  the quad costs 420, so I understand perfectly the pros about going hexa.

 

• At udrones there are many options for the hexa kit, but I think I will include:

3DR GPS uBlox LEA-6

Motor AC2836-358, 880Kv

Propellers: 11X47 SFP

Suggestions?

 

Questions:

- which connector should I select for the power module?

- Telemetry electronics? is there any difference  or can I go for any of them, I am in central america… should I go 433 or 915Mhz?

- Sonar sensor: do I need it to start or may I add it latter?

- Radio Control: should I buy a 299USD one (spektrum DX7) or may I use for example a 60USD turnigy 9 ch control or some other in the middle? Reccomendations?

- If I dont include a OSD/FPV (340USD), I still need a Video TX/RX to get a gopro camera working ?,

I wonder about this because the gopro camera costs 200USD and a wireless video transmitter receiver 190USD and the GoPro seems better than the miniCCD camera offered…

- Batteries: minimum requirement cost vs best fit?

- What should I expect in terms of speed, payload, autonomy, range…?

Sorry to bother you with all these.. thank you all for your support but more important: I wish you all a happy new year! :)

Regards, Patowski 2013

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Permalink Reply by Stephen R Mann on December 28, 2012 at 11:30pm

I can only speak from my own experience with my 3DR hex.

I have the 2.0 APM, but added the external uBlox GPS and saw an increase in GPS accuracy.

Same motors, but instead of reaming out the clearance hole in the arm as directed, I use the motor mount that came with the motors as a spacer (first photo).  You need to buy M3x25mm screws for this, the M3x22 that come with the kit won't work.  This accomplished two things, it provided the clearance that the motor needed and it stiffened the mounting point, which I found to be weak.  (Second photo).  Also, M3x22mm screws are hard to find...  (Okay, three things)

Also in the first photo, notice the kink in the blue wire.  The assembly instructions say to snake the motor wires through the arms.  I have moved my wires to the outside of the motor arms (next photo) because a lawn-dart landing risks cutting the motor wires when the edge of the arm becomes a guillotine.  It also makes the wire length shorter and the barrel connections easier to secure and visually inspect during preflight.  Not that the hex is upside down in this photo.

Note also that I painted the forward arm with a bright orange - it helps with the copter orientation in flight.

The stock propellers are the ones that failed in flight.

 The grey props in the above photo are 12x3.8 composites from APC (http://www.apcprop.com)  Their website really sucks at orginazition, but here's the part numbers:  LP12038SF and LP12038SFP.  they are $3.95 and $5.92 each respectively.  You need three each - I recommend six.  (You will crash and break props).  I don't have much flight time with the new props to have an opinion, but the first things I noticed are that every one of them were perfectly balanced (the black plastic props all required serious balancing before installation) and the hex was noticeably quieter in flight.

I standardized on the XT-60's.  I bought mine from Hobby King (#XT60/9572 Nylon XT60 Connectors Male/Female (5 pairs)).  Only because my first batteries came with the XT60 connector (#T5000.3S.25/14842 Turnigy 5000mAh 3S 25C Lipo Pack).

A couple of other items came to mind as I was looking over my Hobby King orders.  Ont thing that you absolutely must buy is an audible battery alarm: (DL-Volt-Alarm/18987 On Board Lipoly Low Voltage Alarm).  It's less than two dollars and really a good thing to buy.  Second, neither the 3DR kit nor the Spektrum R/C kit came with servo cables to connect the receiver to the APM.  (#AM1043-60CM/9687 60CM Servo Lead Extention (JR) 26AWG).  A bit over $3 for 10 cables.

Telemetry is one of those really nice to have items.  You can fly without it, but after flying with it, I can't imagine not having telemetry.  I use the 3DRadio, 900MHz kit.  I have NO experience with the xBee.

Sonar is not essential, but altitude hold is a bit more accurate at less than 10 ft.  

R/C kit - this is NOT the place to save money.  You want to put a $600 hex carrying a $500 camera at altitude with a $60 radio to control it?  When I bought mine at the local hobby shop, I asked the owner what was the difference from the cheap models and the Spektrum DX7.  His reply was "About 6-months".  What??  He said that he would happily sell me a cheap model, but that I would be back in about six months to get something more well built and reliable.  I bought the DX7, but in hindsight I should have purchased the DX8 to get another channel for camera control.

Cameras - The latest GoPro camera has WiFi built in, so you can set up the camera from your phone.  I have the older HD Hero and the LCD backpack.  Sony has an answer to the GoPro.  The Model HDR-AS15/B weighs 65g.  The Sony price is $269, but B&H has deep discounted it to $268.  It shoots up to 120p for nice smooth slow-motion. Here's a link to the Sony announcement.

I bought a bunch of 2200mAh (3s) batteries when they were on sale for $8.  I got about 7-minutes from those, 10 to 12-minutes with two in parallel.  I also bought a pair of 5000mAh (3s) batteries and I get about 10-12 minutes before the alarm goes off.  I haven't timed the two 5000's in parallel yet.  If you parallel batteries, they should be identical.

Speed, payload and range are all related.  They all need fuel (battery capacity).  And it's a never-ending arms race.  You want more range, you need more fuel (battery), which adds to the gross weight, reducing your payload, so you get even larger batteries - lather, rinse, repeat.  At some point your gross weight is too heavy to lift.

I have lifted 3 pounds with my hex, but only as a demonstration.

Oh, in the last photo, notice that I added sonar mounts between all six motor arms.  Through multiple hard landings, two arms were able to shift position and I had two props overlapping.  I don't know how many times I flew with this problem - a prop strike would have been catastrophic.  I added the sonar mounts as stiffeners to keep the motor arms properly positioned.

Wow, this is a long post.

Hope it helps.

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Permalink Reply by Patowski on December 31, 2012 at 9:30am

Thank you very much stephen, endeed a great post, I have a lot of material to study now. Thanks again and have a happy new year!

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Permalink Reply by Joe B on January 2, 2013 at 3:08pm

Great post!  Very helpful.  

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Permalink Reply by Joe B on January 2, 2013 at 3:48pm

Stephen, 

I've integrated your feedback into a little spreadsheet I am putting together for a rig I am planning to build. (One that is very similar to your own.)  Could I ask you to look over it and provide feedback?

http://goo.gl/h9svS

Also, could you elaborate on your battery choices - as a beginner to RC I find the number of options overwhelming.  Alternatively, if there is a good resource for me to read, that would be much appreciated.

Thanks again,

Joe

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Permalink Reply by Stephen R Mann on January 2, 2013 at 4:11pm

First, I am far from an expert or authority.

I was also confused with the huge array of batteries available  but I bought six Turnigy 3s 2200mAh batteries and two Turnigy 3s 5000mAh batteries.  The 2200 batteries were on sale a few months ago for, if I recall, $8 each at Hobby King.  I have read that for heavy lifting I should be using 4s batteries, but I haven't tried any.

I would hesitate to do the FPV yet.  Learn to fly first.  No sense in risking a camera and gimbal to the inevitable learning crashes.  But, telemetry is strongly recommended - if for no other reason to possibly assist in determining a reason for a crash.  Without telemetry, you're flying blind.  Literally.

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Permalink Reply by Darrell Burkey on January 2, 2013 at 4:37pm

Wow, that's very useful info. Thank you. I'm about to move up to a 3DR hexa from my quad so great timing for me. I do have a question. In your first photo I don't understand how the motors are attached. Or is that a 'before' mounting photo.

It's interesting that there is no side hole to run the cables through the arm like there is on a 3DR quad as I totally agree that you wouldn't want to run them through the end opening for the exact reasons you mention. BTW, I use plastic plugs on the end of my arms. I just don't like those sharp ends and in the few crashes I've had it keeps the dirt from going in the arms as well. You can get them at any hardware store. They are designed for the bottom of chairs and furniture and just slide right in. I did have to cut on side so it doesn't hit the screws internally but it still works great. Just a little detail that I think finishes it off nicely.

Anyway, that's a great looking hex. Are your videos online? I'll go have a search now.

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Permalink Reply by Stephen R Mann on January 2, 2013 at 5:04pm

I tried putting them into a YouTube playlist.  Let me know if you can see them.

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Permalink Reply by Darrell Burkey on January 4, 2013 at 2:58pm

Thanks, I've watched a couple. You would laugh at me here as when I watched the first one I was yelling, 'watch out for the tree'. Anyway, thanks for those. 

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Permalink Reply by Joe B on January 2, 2013 at 4:40pm

Thanks again - I agree completely with regard to learning to fly first.  That spreadsheet I linked to is divided into two categories such that I can get the thing built and flying before I spend any money on the FPV side of the project.

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