Comment by Jerry Rodberg on March 28, 2011 at 1:21pm

While you want to save the copter, your REAL concern is the DLSR. So, considering the issues with whole copter recovery, why don't you look at the other end? Build an impact resistant (plastic and styrofoam) shell around your DSLR. Mount that into your gimbal cradle. If something goes wrong, eject the whole module. Attach the parachute to the rear or whatever puts the most foam between the camera and its impact. A spring ejection would clear the camera from the chopper, provide velocity to inflate a parachute, and keep you clear of the rotors in one fell swoop. If the chopper is in flight, this may destabilize it, but the ejecting capsule could clear a second chute out of the frame. Flight gains could be adjusted to correct flight, too, if need be, to adapt to the change in center of gravity and weight. It'd also be actually testable without risking copter or DSLR.

Comment by ARHEXA on March 28, 2011 at 1:38pm

mmm, this might be a bit too far...

the camera mount and landing gear around it will be made of thick aluminum tubes, i think it's a good protection, even if they bent a little, there still will be room before hitting the camera. and yes i can add foam....

anyways, i'm not aiming to save only the copter,

why not saving BOTH at once with a single parachute...?

after all the copter costs like 1/2 the DSLR....

 

what i've got to keep is an option to disable it totally - even if it's 100% manual.

if i'm flying near the sea or a lake, i'd prefer it smashed on the ground rather than drown in the water....

Comment by Jay Bryon on March 29, 2011 at 11:55am

Chutes used in High Power rocketry might be an option, I'd also look at a mesh parachute (mesh on the bottom instead of lines), just to avoid tangling issues with all the rotors.  As for deployment speed, without a forceful deployment you will have drop before it opens, you could use a power deployment with a cardboard tube (which then helps clear props too) ala HP Rocketry (usually a small BP charge).  But I wouldn't do that without looking at the potential regulartory issues.  A spring/piston might be a better choice.... 

Perhaps you can also reduce reaction time with a deadman switch stick that you just drop if things go bad.  Probably faster than fumbling for a toggle anyway.  You'd need to enable aggressive and active breaking on your ESC's to stop the props in time, not sure that's worth it. 

Comment by Martin Seven on March 29, 2011 at 2:59pm

Regarding ESC brakes, do they have an effect on the actual spinning (increased consumption etc.) or are they applied just for braking, when throttle command = 0?

Comment by Jay Bryon on March 29, 2011 at 6:45pm

The latter, basically it just energizes the coil or coils statically, with no commutation, so rotation is inhibited.  It will consume some current while doing so, but you can adjust it with many ESC's that allow programming.  Obviously this only happens when throttle is considered 0, since normal operation requires appropriate commutation.  (Which the ESC provides for brushless motors, which I'm assuming here).

Comment by ARHEXA on March 29, 2011 at 11:28pm

I see,

breaking is an option. i hope it won't affect with very high torque resulting in yaw or flip over... (remember one motor is probably gonna be dead)

 

Yesterday i tested what happens when you disconnect the ESC while motor is running:

it was a generic ESC (not arducopter), when i disconnected the signal it started to jump between 0 throttle and the throttle it was left on, randomly.

though maybe connecting the signal line directly to ground might tell the ESC to stop also - have to check.

 

so for active breaking i have to put relays on the ESC's signal lines that will take the signal away from the APM, and connect all together to a servo tester outputting "0" throttle.

that's not too hard.

 

Comment by Martin Seven on March 30, 2011 at 12:55am

It might be acting like that because the open signal wire is picking up noise. Try pulling the ESC signal line low (grounding it) with a 4k7 resistor. That should take care of the noise without affecting normal communication.

My Turnigy Plush, when disconnected, revs up to full throttle for about a second, then shuts down. It almost ended ugly when I first tried it.

Comment by ARHEXA on March 30, 2011 at 12:57am

i can understand that,

just tested a 80A 100mm EDF yesterday !

Comment by Chris Card on April 1, 2011 at 8:03pm

I've been thinking about how to deploy the chute deployment without pyrotechnics or stored air pressure..
An umbrella comes to mind, and ....
..I'm wondering if small graphite rods could be fastened in the same manner, if they could be somehow curled up when packing the chute. And they would force or at least encourage the canopy to open quickly.
Perhaps a light weight plastic with lots of 'memory' could be used. Music wire might work.
Next time I'm at the hobby shop I will see if there is anything that I can find to do a simple test.
A spring, as Gary mentioned, for ejecting the parachute may be the simplest way to get clear of the copter.
The toys (guns) that shoot those darts with suction cups can get some range....they also have a trigger mechanism that may also be useful.

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