REBUILD: lessons & learning to follow (PT2)

[SoCal Blur]

Thanks for being the guinea pig on the case. I might get one and then cast it and make a flexible urethane or silicone copy that would provide some vibration and impact protection. Of course, it would be nice if the 3D printed version was correct to start with. Will you be reporting back to the guy and letting him know where he needs to make some changes going forward?

 

[Motopreserve]

He is definitely open to any suggestions - and at one point said I could ship him my FC. I wasn't into doing that (time, not trust), so I just described the things I needed. He got all of them correct - except I never mentioned the SBUS header issue. I just assumed they were all the way mine is (header pins to the outside) - and he set it up for pins straight up. My fault. But even if he had left a space for them to exit - the placement of the mount hole of the multiwii Mega is too close to the header pins. That's something that couldn't be accounted for - or at least not off the top of my head.

Let me know if you ever make one out of softer material - I'd buy one of those in a heartbeat.

The beast is all back together now. I need to get out for some testing if the weather ever breaks, and I'm realizing that having the gimbal in the back of my mind would have just distracted me. Maybe it's fate that it went haywire. I was getting so ahead of myself I had even forgotten to rebuild my chopstick antenna mount. That's the thing that gave this build it's name!

 

[jbrumberg]

"Strange things" can happen during the rebuilding process if there is an extended time frame. I am glad you are back together on the rebuild. I am basically in the same boat, I may have to throw together another modified landing gear setup; watching weather maps.

Wish you the best.

 

[Motopreserve]

It's back!!!! I was feeling feisty so I put the antenna on a little off center. Force myself to not care about symmetry so much

 

[jbrumberg]

It's back!!!! I was feeling feisty so I put the antenna on a little off center. Force myself to not care about symmetry so much

Scott- quite the "Devil May Care Look" from you. Are you ok? :frog:

Looking good.

I hope you (and I) get a chance to get airborne soon. At least for testing purposes.

 

[Motopreserve]

I'm good! Really I just wanted to make sure the RX was more exposed to get to the pins in case the Sbus doesn't pan out to be kosher. That caused there to be even less room on the center area. So far so good though.

 

[SoCal Blur]

And if nothing else, you now have a nifty carrying handle.

 

[Motopreserve]

And if nothing else, you now have a nifty carrying handle.

I was talking more about the chop sticks antenna, but I actually LOVE the handle. Honestly, I found myself picking the quad up more by the GPS hood than anything - which was probably stupid. I did some research about the aluminum and I have high hopes that I might get away with it. Most reports of issues are with more solid aluminum casing when it cones to GPS interference. Video feed is a different matter.

Its clear as a bell here right now - I can see the stars, and that bodes well for a possible flight tomorrow??? Feels like it's been forever.

Baby by steps all over again through. While I'm confident in my soldering work on the new PDB, it's easy to be hesitant about how precarious all these components are as a whole...

Live and learn though, and hopefully I'll see more success with what Jay described as build V2

 

[Motopreserve]

Now that I have the whole quad buttoned back up and ready for flight (fingers crossed), I'm reminded that I should have cut the motor shafts to a better, shorter size. Once the props go on with these shafts it's very apparent that they are dangerously long. Should have done it while I had the time (more than enough time waiting on the replacement FC!). I also have the other motors from Witespy, which I may try out once I get this thing back in the air - and tested with the original Turnigy D2830-11.

The beauty of the Witespy motors is that they come with the bolt-on prop adapter. Feels like it will be more secure than the collet-style adapters. Soon enough...

THIS:


VS THIS:

 

[Motopreserve]

Weather is warm here today - and although the wind was quite calm early this morning, it's kicked up a bit.

I'm not sure in going to be able to hold off at least getting it hovering. I've been waiting FAR too long to get this beast back in the air...

Decided to go back to my aluminum cross braces on the landing gear. Earlier it seemed that maybe rigidity was working against me on hard landings. But I think with the snow, it might prevent easy tipping a little better than without it.



Loaded up the hot glue to see if it will hold a little better than the first attempt at securing it.

 

[SoCal Blur]

If you get out there and hover a bit, get some video so we can see the "easy carry quad" in action

 

[Motopreserve]

Definitely will. I have the gopro mounted already (lots of rubber bands!).



I'll try to set up the iPhone or some other camera to capture the view from the ground.

I guess it has morphed into the "easy-carry chopstick" quad

Need to at least get some basic tuning done (mag, acc etc). At least that will make me feel like I've done SOMETHING!!!!

 

[jbrumberg]

Winds are maddeningly squirrely so far today in our region. At least with the overcast there will be no additional heating to stir things up any further. The flurries are hit or miss and light. I wish for the best. I may need to throw together a super "quick and dirty" take off/landing pad due to my available surface terrain challenges.... The joys of Winter in New England (USA).

If you manage to get out Scott good luck.

Jay

 

[Motopreserve]

Finally the testing phase...

46 degrees and semi-sunny. Wind is a factor, but so is impatience...

I've mentioned it before - but I have to admit again that I was a bit gun shy from the last 2 crashes - which were my last experiences before rebuilding this quad. But you need to get back on the horse, so after procrastinating for a bit - it was time for action... Grabbed the cameras and the Android tablet for calibration, and headed out to the driveway. Although it's tight out there - it's better than sitting and staring at the damn quad in my office!



The video is not exciting (boring footage & 10 minute edit) - I really just concentrated on keeping the bird in the air, and somewhat stable. The wind was a challenge - and there were a few scary moments when the wind seemed to push the quad directly back at my location. But she handled fairly well considering. Lots of jello on the GoPro - which almost seems worse than it was on my very first flights - before I had gotten decent at balancing props - and the motor balance had been untouched. I need to go back to the drawing board for balancing the motors.

Also, the aluminum landing gear braces with only gobs of hot glue for support fell off almost immediately. I think I have finally decided that the landing gear is fine the way it is - and I will stop obsessing over it.

A few concerns I have at this point:

1. High throttle needed to hover. I was up around 60-70%. Not ideal for sure - but obviously the GoPro adds weight to this beast. I am itching to swap the motors for the RTFQ versions I have.
2. PID tuning. I know I need to wait for messing with these until the wind is gone - but there seems to be some real need for tuning. Sadly, the info on the web for multiwii PD tuning is all over the place and a bit difficult to wrap my head around. I think I know where to start - and will do this next time I have some wind-free weather, and some more open space...
3. Trying out various flight modes is NOT going to happen in the driveway. Horizon (stable) mode was fine, but flipping on the GPS hold would have been terrifying since I was a few feet from our cars. I need a field!

 

[SoCal Blur]

Not to too bad all things considered. Thanks for sharing the video.

I'm curious as to why you felt you need to add those cross braces to the landing gear. Did it collapse on you on a previous flight?

 

[Motopreserve]

It didn't collapse - but they are very loose and flexible. When I first flew the quad - it came down hard, the bounce created a tip over several times.

What at I finally decided was to learn how to let it down a little softer

 

[Motopreserve]

With the snow and cold moving back into the Northeast, I haven't made much progress on the testing. But I did want to mention a cool gadget I grabbed recently - which makes testing motor direction a bit easier. Technically it's made as a servo tester - but works fine with ESCs. It allows you to spin up 3 motors at a time (you need to do the last motor separately) without having to hook up the transmitter and receiver.



Power the ESCs from your PDB, plug in the 3 ESC servo wires to the output side of this little gem (which will provide power), and use the on-board pot to spin up the motors to test direction - all before you seal them into an enclosed, hard to get to location on your build. At only $4 shipped, its a nice addition to the small gadgets/tools to have on the bench.

I'm thinking of rigging up some sort of bench testing station for motors - and since I have some extra ESCs it should be easy. The fact that I could bench test motors without needing the Tx/Rx would be nice.

You can find them on eBay HERE: USA located for super fast shipping too.

 

[mbowser]

It didn't collapse - but they are very loose and flexible. When I first flew the quad - it came down hard, the bounce created a tip over several times.

What at I finally decided was to learn how to let it down a little softer

Scott, I have the same frame and was planning on installing some struts for the same reasons, but never got around to it. Now that we have flown and crashed it hard on several occasions,
I've found that keeping those legs free has mitigated a lot of the damage from our crashes if it had been made rigid with struts. It can definately be a bouncy landing if you come in too hot, but on all of our bad crashes (20 feet up in a tree, telephone poll, side of brick school), the landing gear has simply 'popped; out of where it is mounted on the camera rails and lessened the impact greatly. I wouldn't call it a crumple zone, and I don't know that it was actually figured into the design (probably not), but it is effective. Ultimately, they will probably break at the camera rail mounting point on one of our crashes, but to date, we have only had to pop the gear back onto the rail.

 

[Motopreserve]

Sounds like we have had the same experience. At first it was nerve wracking to see the quad sitting off-kilter after it pops out. But eventually I realized (like yourself) that it was actually working in my favor - until I can feather it down gently (never going to happen!).

Id love to fab some other type of lighter boom-mounted landing gear. Just not sure if it would handle the weight of the quad.

What at is your AUW right now? I just measured mine and I'm coming in at about 1900+ grams with the gopro (hard mounted - no gimbal).

 

[mbowser]

Ha, the first time it happened I thought the same thing "Oh Sh**, I've completely ruined it!". After inspecting it though, it was a relief to find that it just popped off the rails.
It's been while since I weighed it, but I believe that I came in at 1370g without a camera. I'm surprised at the difference; the goPro can't weigh much more than 100g. I am using a 4000mAh battery. I'm going to reweigh to be sure, but we now have 900mHz fpv camera and tx mounted. The tx/antenna is fairly bulky.