Archive - November 2010
Off the shelf 4D flying
15th November 2010 -
Yesterday I finally got around to trying out the new Axi 2203/40 VPP motor in my latest 4D model. The results can be seen in the video below, but first a few details. The motor is mated to the popular Mamo Upside-down VPP unit running 9" blades, with a Logic RC LSX-65H servo direct mounted on pitch (see picture below). Please note the mount I've used is custom made, and the LSX pitch servo is packed off the mount by about 6mm so that everything lines up ok, the bearing that runs inside the Mamo unit is mounted directly to the servo arm. For those of you interested in running the Axi/Mamo setup, or maybe you already have it and are having difficulty setting it up, I'm going to point out some of what I've learnt thus far, but first a video:
The correct mechanical setup of the unit is key, you want a free running, smooth system without any binding. Don't tighten the retaining bolts in the base of the propeller blades too tight. I nip mine up so that the bearings are just supported without any play, but can still spin freely. Also make sure your neutral point (where the blades are at zero pitch) is truly zero pitch, you can sometimes have a little residual thrust one way or the other (see the vid below for how I the neutral point). For the AXI 2203/40VPP + Mamo combination, there is no need to limit the throttle. And change the propeller retinaing bolts after every crash! They WILL bend, and even if the blades are ok you will lose power even if the bolts are fractionally bent. They are 2mm x 12mm in size so it helps to keep a bag handy. The rough values I use for pitch are (measured on the unit), 1mm forward and 1.5mm reverse, this is a starting point only. The only way to correctly setup a 4D unit is to use a wattmeter and monitor amp/watt values, so you know you're not going to blow anything up and also so you can see how your pitch changes affect amp draw. A good rule of thumb is aim for equal amp draw in positive and negative pitch, without bogging the motor down and losing revs (revs are key!), the wattmeter I use is about £27 (GT Power meter from Robotbirds). So far my Axi/Mamo setup draws no more than about 10.5 amps.
The motor, 4D unit and pitch servo I've sourced from www.electricwingman.com. It's crucial to keep the weight under 155 grams for best results, 160 is a max.
A more thorough study of the Axi/Mamo setup will be coming in the next few months in my column in RCM&E magazine, until then check out the video below! The milling on the model that I pointed out in the video isn't all that clear, so I've stuck a photo on here of the rather cool milling (thanks Simon!)
Remarkable flying manta ray
7th November 2010 -
I saw this on the telly the other day and had to share, the ray is made up from a specially engineered structure that mimics that of the real animal. The "wings" are driven by servos, no automatic flapping here either, the operator has to move the transmitter sticks in the right way to get the desired effect. The whole thing is filled with helium for bouyancy, and is even capable of basic aeros such as loops, albiet very slowly. The company who have come up with the ray, Festo, have a host of other flying objects too.
