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Permalink Reply by Scallopking on June 24, 2012 at 8:17am

Hey, thought I would answer one of your questions, because I have had a bad experience with it.

On my first and only quad, still flying it by the way, I started with two packs. They were wired to two separate motors each. Now I remember my first flight, the quad, when I made it turn, it would wobble when I stopped the turn, and when rising in height, it would also wobble.

After draining the batteries, and a couple of dissatisfying flights under my belt, the light bulb came on. I checked the battery volts of each pack and sure enough the voltage wasn’t the same. This will affect the rpm of the motor set.

I assume that the two motors per pack use different demands of voltage, when turning the quad because of the different rpms need for that to be accomplished. This voltage fluctuation my make it hard for the APM to balance the frame, nice and stable.

I put a jumper wire between the two packs, and went for another flight; the stability was the difference between night and day. I checked the packs after the flight; it should be obvious that they now had the same voltage.

I still use two packs with the jumper wire between the too. I can only imagine the ease of plugging in, balancing and placement of one pack on any airframe.   

Prop section, like any airframe is trial and performance. In my experience, if your props have you flying with a low throttle input, then there is very little stick movement, one to two clicks, between up and down flight. A smaller less thrusting prop will give you more slack, if you will, between stick movements, making the airframe less sensitive, and easier to fly.

My quad on fresh batteries, does not like to hover without constant stick movement. As the packs deplete, the voltage drop decreases the rpms, making the quad less sensitive, needing three to five clicks on the throttle to change from hovering to ascent, much better.

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Permalink Reply by MC on June 24, 2012 at 7:32pm

Yes, that is precisely the symptom I had in a later flight with two packs. After the flight I checked the voltages and there was a enormous difference in voltage, likely caused by the fact that it was windy and I had to keep pitching forward (one battery powered the front engines and one the aft ones).

I had stable flight and then when I decided to yaw, it wobbled pretty bad, I actually lost control and crashed from (a rather controlled crash, at 30 feet from the ground I had leveled but the sideways inertia had already built up and I figured that if I throttled any further engines could stall and make it worse so I cut power, it feel straight to the ground, no propeller or body damage).

I am going for a single battery now. As for the engines, I will try a smaller ones, and keep these towerpro monsters in case I ever want to build a hybrid honda civic... lol.

Thanks for the response, together with the voltage I mentioned earlier, the crash made perfect sense.

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