The battery situation looks like it's going to dictate four motors after all as we move ever onward, and accordingly I look at what is lying around the workshop. Here we've a couple of 22000mAh six-cell LiPo packs that we can consider. Firstly a word about the chemistry. Electric cars (beside flying taxis and aircraft) use lithium-ion cells generally as they're good at endurance. These here tho' are more suitable for over-sized drones in view of the power they can deliver for short periods: known as the 'C' rating.
Looking at where they might be located, if they are to be fitted to the phone-box then it would have to be either side of Monty's head, around the base or midriff, or behind his back in a pack. Of these the option at foot-level is undoubtedly the neatest as it effectively hides the packs from view: few people would prefer a Porsche with battery fitted atop the roof.
It would tho' render the aircraft unduly pendulous and difficult for the drone to handle because cars and aircraft are ideally designed with a 'low polar moment of inertia' for such reasons. Albeit in a lateral plane instead of vertical, a want of it in old Porsches is what killed James Dean.
Altogether better from the handling side of things is to mount these up top. A reason I liked the idea of batteries in the 'box' is that you can then duck beneath the propellers whilst connecting the batteries, instead of leaning over them were they on the 'drone. Beggars however cannot be choosers and so it is looking like we shall be sticking with a pair of batts wired in series up top.
One problem is that we've now insufficient room above the head of the mannekin to mount a flight-controller inverted on the underside of the drone. In turn it means that its topside is a little crowded, and a way that we can address this is to halve the size of the packs with a 10,000mAh type. It would also halve their weight.
Turning back to the U11 performance figures, everything is about the figure six: at 60% thrust they deliver 6kg of thrust apiece, for a total of 24kg. Together they are drawing 60A of power at this setting and ~ 10,000mAh being 10Ah ~ it means that the packs are six times smaller than they need be to power for an hour. In turn it means they should run for ten minutes, or a little less as they cannot be run flat.
The phone-box, mannekin, motors, drone and 22,000 packs currently tip the scales at 16kg or 35lb, inside the CAA anal-clenching trigger and with a 50% margin of power over weight.
Get in that box, Tom Cruise!
