The past couple of weeks have been pretty busy, between finishing up on Cars 2 and getting things together for a trip to Bolivia, and I haven’t been flying as much as I’d like to. However, Mark and I started building our first quadcopter, dubbed the Arcticopter I, yesterday, and it’s pretty neat!

I have to say this whole project seems to be about timing–timing because it’s just really becoming feasible to use a multicopter (a newer type of device) to lift cameras, only recently has first-person view flying become really reasonable, and only in the past few months did Mark start to get into RC aircraft. I think I would’ve ripped my hair out, trying to figure out all the pieces and connectors without Mark’s help. Fortunately, we’re documenting our build process carefully so that you can benefit from Mark’s brain, too. He’s posting everything on his blog under the “arcticopter” label.

Yesterday, we started to actually build the copter. Mark walked me through the various parts, explaining what everything does. Given there are so many parts, let me share briefly what I learned to help you decipher hobby websites, should you decide to build your own copter!

There are two types of props, APC Slowfly (these words are used interchangeably) and direct drive. Slowfly blades push more air than the smaller direct drive props, and they spin at a lower rate than direct drive because they’re doing more work. They draw more power, though, to spin the blades.

The props attach directly to a motor. We’re using a Hacker Style motor (Hacker’s a brand, but ours is a knock-off), which looks like an inrunner motor, where the shell of the motor doesn’t move at all, but it’s an outrunner, meaning the shell does move. There are rubber bands you can put around the prop to protect them and the motor in a crash if you choose, but they can break off and become a projectile, especially in a cold environment, so we may or may not use them.

There are three wires that come out of the motor, and an ESC (electronic speed controller) with three wires will connect to the motor’s wires. The ESC applies power to different combinations of the wires, which causes the magnets inside the motor to cause the wire core of the motor to spin.

Two wires from the ESC connect to the power source. Because we have multiple motors, rather than soldering a connector for the battery to the ESC, we’re connecting the ESC to WAGO connectors and wiring the battery to a pair of WAGO connectors.

The last wire from the ESC connects to the control board (in our case, a KK board).

For our power supply, we’re trying two initially, a Turnigy 2200 mAh 3S 25C and a 3000 mAh 3S 20c. Bigger batteries (like a 6S brick) can power larger motors, but they won’t get you longer flight times. 3S means that there are 3 LiPo cells inside and 6S means that there are 6. Each is separate from the other, an important fact to remember while working with them.

For instance, every 5 charges or so, you need to do a balance charge, which will charge each set of cells but also drain them as-needed so that all the cells have the same charge in them.

What’s a bit funky to me is that unlike your laptop or field LiPo battery, which is calibrated for a particular battery type and has calibrated its display accordingly, everything with these RC batteries is in pure voltage. For example, if the voltage in the Lipo drops below a floor, about 2/3 of its max voltage, the battery stops being as effective, and if it drops to 0V, it’s dead and unchangeable. But obviously if you drain your laptop’s LiPo battery to 0%, it’s not dead.

It’s also possible to overcharge a battery, causing it to puff up and start spewing fire and destruction. We’re putting extra long wires onto our charging cable so that we can keep the battery in a fireproof LiPo bag while charging, and never leave the batteries unattended while charging.

We ended up getting a big charger, a Turnigy 4×6S, which can charge 4 batteries at once. As a tip, once you’ve selected the voltage and current (look for something called the charge rate, which is typically 2 * the battery’s milliamps) to use to put into the battery, press and hold return on the charger to start the program. And if you’re going to let the batteries sit for a while, don’t store them full. Use the storage program to drain the batteries to a safe storage level.

We also purchased a 25 amp power supply for the Turnigy, which is a big beast. This combo is great because it can charge 4 batteries in about 30 minutes, but it might not be portable enough for some remote locations. I also think the power draw would be a bit high, should I need to run it off my portable power pack and solar cells, but we’ll figure that out later.

Next up will be balancing the props (making sure they’re evenly weighted on both sides) and really putting everything together!

This entry was posted on Sunday, February 6th, 2011 at 3:12pm and is filed under RC Aerial Photography. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.