Hello everyone, in this blog post, I will be documenting some of the key steps for repairing the old quad copter drone we have here in UWC ISAK Japan.
So what’s the deal here? Well, wastefulness. In Robotics club last year, I noticed we had a drone in stock that nobody was using. I wish I took a photo but to describe briefly, it was in such a destitute state, it was begging for use and repair. The dirty props, dusty motors, crumbling cushion foam, and a weird yellow powder released as a I press on the rusty screws holding undone connections on a Pixhawk. the LiPo bloating as if it were to burst at any moment, and the spare parts sorted only but well enough to abandon.
And if that Allan Poe-style description doesn’t bother you, I had recently learned that the last time it was used was in 2016. 3 years ago! What a shame that our club leader didn’t let us touch it, let alone repair it. He said it was done for, well now he can speak for himself…
Another reason I wanted to do this was kind of to redeem myself from a kind of failed/kind of successful drone project I did in my old school. It was both a fun and painful experience that ended with heartbreak as I had to leave for UWC. I think this time, repairing an “abandoned dream” was a backbiting but ultimately rewarding means of redemption.
After small deliberation with an interested team, we decided to move ahead with this seemingly gargantuan task. For a month, we’d meet every weekend to work on the thing. Quite a labor of love for an old geezer!
This having been said, enough drama! let’s go on to the fun part. Well… you’ll see why the first part wasn’t really that fun.
The first thing I had to do was to dig deep to find a relatively scarce resource in Japan – LiPo batteries, which in fact, are illegal under regular circumstances, to import. Scrolling through a short catalog populated with unrelated items, I had to find a battery that precisely matched the old one. However, 5500 mAh batteries are hard to come by especially ones with 40C ratings. In the end, I had to settle with 5000 mAh at 20C.
Yeah, 40C to 20C is a big jump, and in my last project, the battery was rated at 30C. I did some research and found at that with this rating, I could draw up to 100A continuously without damaging the battery, which is much greater than the 60A I predict four motors will draw at maximum.
To my surprise, the package came with a bad adapter. The first day our team spent on repairing this drone was mostly spent on improvising for an adapter. The result, a good-enough connection with so much glue insulating the terminals, it doesn’t look too safe (yet it is, looks are often misleading, aren’t they?).
Props are easy to come by. I simply looked into the spare parts box for any trace of a brand, and Voila! I found a pair of 1045 Gemfans, the same brand they used. They’re not really carbon-fibre and they look very much like cheap plastics. Would I care to know? For my purpose, robust props are more of a luxury, and these ones don’t really look like scam plastic.
10 inches are a good match for my drone. Stability is the priority after all. Savvy advice from a nice Filipino hobby store owner: 10 inches also tend to spin slower thereby reducing heat build up, necessary consideration for cheap motors that came with the old thing.
Any replacement the team would make would virtually be some wires, foam, and zip ties. However, we did dramatically change the wiring layout, as the old one was just pure chaos. The new layout, on the other hand was clean and clutter free.
Everything you’ll ever need is on the top, and all the power wires and ESC connections run through the side and the inside. Battery (not shown) is attached at the bottom, as custom, and the GPS and remote antenna on opposite vertical ends.
Besides the drone being relatively intact when I found it, I would also be thankful for a nice solution for the wobbly GPS.
The yellow stand shown is a 3D-printed element that I found with the box. I guess these people really knew what they were doing. Unlike the standard stick stands that come with GPS packages, this one had the advantage of a wide based of support, seemingly designed to be put where it currently is. Talk about fit and function! The team really didn’t have to do anything besides hot glue the GPS in the right orientation.
With everything seemingly ready, we held our breaths in anticipation of the final revelation. Trekking down the long stairs felt like an eternity of moments, ones of fleeting feelings of energy and excitement. As we traverse the seemingly long tracts of ground that separate the lab and the gym, high-pitched voices broke the deafening silence of a cold November’s day. Yet a voice kept saying, “it never flies the first time…” Like a ghost appearing in midday, the thought lingered and haunted even the most passionate soul.
The beeps came to being, and the lights flashed yellow, then green, in a seemingly slow sequence of flashes like a sailor lost at sea at night, devoid of all hope, awaiting only his impending doom. Then there were strong whizzes of the wind, breaking at the slashes and whirls of plastic swords spinning. Then there was the count: “Three, two, one…”
(I got tired of describing the experience poetically at this point. Judge the results for yourself)