In the previous installment of balsa wood quadcopter, I described our initial design thoughts and got as far as building the frame. However, we decided that the design as it stood, although lighter than the target of 34g, was just too spindly to survive more than a couple of flights and since I’d neglected to provide battery stowage space we cut our losses and decided to not even bother wiring it up and to move straight onto MkII and a new frame design.
Balsa quad MkII
And here it is. As you can see this is altogether a more robust (looking) affair and all up weight is still a respectable 36g. It’s basically the same construction as MkI but with a much deeper section. It also includes a slot to house the battery.
The next step is to wire this baby up!
Wiring a quadcopter isn’t that hard if you know what you’re doing but hilarity ensues if you don’t. The basic theory is to ensure that the rotation of your motors is correct (two rotating clockwise and two anti-clockwise in an alternating pattern). It’s also important to make sure that the correct orientation prop is fitted to the correct motor – otherwise your quad will attempt to fly into the ground as the props generate negative lift – or at the very least make the thing completely uncontrollable.
Here’s how not to do it.
After a couple of false starts, we got everything right. Successful flight video to follow!
Well, first we need a better way of securing the motors. These small motors don’t include a mounting bracket and in such a soft material as balsa, friction isn’t enough to hold them in place. If you’re not careful the motors escape which risks snapping the fine motor wires. For now they’re held in place with rapstraps which is a bodge but works quite well. Unfortunately, rapstraps only come in one size and are really too big and heavy for our needs. Small tie-wraps might be a better bet.
We haven’t secured the FSB properly. Part of the problem is that the 939 FSB is small so any mechanism for fixing to our balsa frame is going to be fiddly. Spacers and self tappers is probably the best bet.
Next time we’ll post a flight video and any other refinements. Looks like a MkIII is in the offing.