Hex Frame Build Log

[jihlein]

Getting ready to extend the esc wires to the motors.

On my quad, I used 0.0625" ID copper tubing cut into 0.25" lengths as couplers between the esc wires and the extensions. I was planning on doing the same here, but now I'm considering removing the shrink sleeving from the escs and directly attaching longer wires there. Don't think I'd ruin an esc in the process, but one never knows....

Decisions, decisions....

[kevo]

Nice build .. Looking forward to hearing how this works out for you..

I have always avoided changing the wires on the esc's. An old time electrical engener type once told me that changing the length of the the motor wires could throw off the timing of the emf back signals and cause reduced efficiency. ( this was the guy at work that if he says do it his way , there is usually a very good reason for it ) So I am really curious as to if it actually does so in practice.

I was actually thinking of using wider bars/tubes for my next frame , and getting them inside the arms for a clean arm finish.

In regards to the landing gear .. I also have a large spot under the quad and a very low battery tray. In place of installing the gear to the lowest part of the tray , I placed the gear in the middle.


KevoCopter 2.0 Airframe done by Kevo500, on Flickr

I was going to use the bottom plate as gear , however I like the added stability of the wide gear. In the future , I plan to add another plate near the level the gear attached now for mounting of FPV gear. Perhaps even lowering the level of the botom plate to the same level as the skids.

In regards to motor mounting. I also used the "cut holes in the bars" method on my first copter. But I elected to go with clamping the motors to the bars with a second motor mount ( You can likely fashion something like a X out of scrap alu using a motor mount as a template ) .. Its too late for this version of your copter , but it may be something to consider for your next one.

I LOVE the look of the red socket head screws .. Where did you get them ?? By chance was it http://www.fastener-express.com/ ?? I have been eyeing that site for a while , but just have not ordered from them yet.

[jihlein]

Got the screws at McMasterCarr. Expensive, but I wanted aluminum for a few different reasons.

I've heard it's worse to extend the battery leads on ESCs. This was from Castle Creations. Who to believe?? I didn't have any issues extending the motor leads on my quad, we'll see ehat happens here.

Still playing with landing gear idea. I like what you have done, for the same reason, wider stance on the ground.

Well there is a reason it's called a prototype, isn't there?

[jaguar]

Extending the batteries doesn't seem like it could possible matter as long as you use thick enough wire. I could see extending the motor leads screwing up the timing but I cant imagine that relativly short distance is going to matter much. I doubt the tolerances are that tight that a few extra inches will matter.

[jihlein]

I know that castle Creations recommends putting extra input capacitance on the battry wires if the wire get too long, Can't remember what too long is though.

[aadamson]

I added 6" to my ESC's with no negative result.. used a similar approach as you did, but I went to walmart bought pack of 25 14ga butt connectors and then took a dremel and cut off the plastic... then I just used my trusty crimper and crimped and heat shrunk them. A gas tight crimp is better than a solder joint anyway ... and I have a good Amp crimper from my airplane building project

Alan

[krat]

I use 12 gauge wires. Maybe overkill you would say, but it's safe.

Be carefull when soldering a connector, it's very easy to make a cold solder if your don't heat up the connector.

[jihlein]

Well finally clear off the bench to continue this project after being sidetracked over the summer. Not too much more to go, add main power leads for battery, power to Mega 2560, receiver, and telemetry radio. Hopefully chip away at it over the next few days before I return to work next week....

[bryanpearson]

Wow... that's a clean build. Nice!

[jihlein]

It flies!

A little bit about the stange hardware. The sensors are a freeIMU035. The gyros and accels are read at 1 kHz, the baro at 100 Hz, and the compass at 50 Hz. The timing is controlled via an interrupt. These are all processed by one Arduino ProMini. The data is sent to the Mega2560 via the SPI interface. The receiver pulses are decoded by another Arduino ProMini, and converted to a serial PWM stream. The pulses are read by timer2, which has been extended to a 16 bit timer, giving 0.5 uSec resolution. The serial PWM stream is decoded by an input capture interrupt on the Mega2560. The PWMs to the ESCs also maintain the 0.5 uSec resolution. I doubt the current ESCs can effectively deal with that resolution, but that's a future experiment.

For the attitude estimation, I'm using a modified version of MARG. It's got a new accel cutoff algorithm that I hope will help solve the leans.

Now that I know it flies, I need to hook up the telem radios and GPS.

Gains need some serious tuning, but that will have to wait until I get a bigger battery. Need to get some good video.