Quad Troubleshooting

I actually still haven’t fixed my toothpick quad yet. Originally I wasn’t in any hurry to get it replaced and I was hoping to try that antenna fix as well, but I haven’t made the time to do it. Between the holidays and wrapping up a lot of work tasks before going on my end of the year vacation, I really didn’t have the motivation to sit down at my hobby table and take it apart even though once I did I’d probably have it all done in under an hour. But for now I wanted to talk about the most frustrating part of the hobby for me, and that’s when things just stop working or at least start having problems.

About two months months into flying my HX100 toothpick daily for about 30 minutes using six batteries, I suddenly started having an issue with my video signal going to static and then cutting out when I’d take off. Doing a visual inspection didn’t show anything. I tried taking off a few more times and then just holding the quad and moving it around by hand and noticed that any kind of vibration would cause it to go out again. It sucks when a flight session is cut short by a technical problem like this, but that’s one advantage of being able to fly at home so easily, at least I hadn’t had to drive somewhere or hike out to a remote spot only to have to leave early.

So I took the quad to my hobby table to open it up. The last time I had a problem with it the answer was pretty obvious as the receiver antenna literally fell of when I took the canopy off. Which was nice because I immediately knew what the problem was and just had to order a replacement. This time unfortunately there was no such obvious sign of what was wrong. The VTX antenna didn’t look loose at all, it was securely soldered to the board. All of the solder connections for the wires connecting the VTX to the flight controller looked solid. The wiring harness looked okay, there was some damage to it that I had noticed and fixed with electrical tape a few weeks prior when I replaced the carbon fiber frame, but there was no new damage. I tried wiggling the wires when the battery was plugged in and didn’t see any issues in my goggles from the VTX signal.

There’s another difficulty when troubleshooting problems from the bench. VTX’s general a lot of heat as in they can burn you as well as just fry themselves if left on for too long on a high power setting. This isn’t normally an issue since the expectation that they’re on a quad flying through the air so there’s a lot of cooling from air flow. When inside on a table though that’s not the case. So every time I tested it out even when I had it cranked down to 25 mW which is the lowest setting, I had a limited window if I didn’t want to ruin the VTX.

So at this point I was unsure what to do. There was nothing obviously wrong with it that I could try to fix with solder or tape. I’ve learned that this is the point where I have to start swapping components, so I ordered a replacement VTX. They’re not super expensive at $15 from online vendors like RaceDayQuads or Amazon, but still not something I wanted to be replacing often.

While I waited I decided to try to cut out the damaged sections of the wiring harness that connected the VTX to the FC and solder the wires together. Which unfortunately didn’t make any difference but it was at least some good soldering practice. It also confirmed that it wasn’t the wiring. That left either the antenna or the board which amounted to the same thing since they were soldered together.

I even ended up cutting away the heatshrink protecting the antenna and didn’t see any damage to the wire itself. So my guess at this stage was something on the board itself had gone bad. Maybe a surface mounted component was loose or some component was damaged internally.

Thankfully when the new VTX showed up in the mail a few days later, I had no problems getting the new wiring harness soldered to the flight controller and getting the quad back in good working order. Or at least I didn’t think I had any problems until I noticed that I couldn’t adjust the VTX band and channel using my radio. It wasn’t enough to keep me from flying thankfully, but it is annoying knowing that the quad wasn’t in 100% working order.

It’s actually a problem I still haven’t fixed. I even have another VTX and a replacement flight controller as well, since the issue might be on either end, and given the FC had quite a few hours of flight time on it, it’s probably that end where the issues is. It’s what happens when I know I can just fly something instead of being forced to take it apart an troubleshoot it again. I think that’s part of the reason why I’ve put off fixing the motor, since I have to take it apart enough to do that, that I might as well work on fixing the VTX issue as well.

Crashes and Quad Repair

In quad versus pole, the pole always wins.

It was decent weather over the weekend for Indiana in December, meaning that it wasn’t completely overcast, windy, and miserable. It was still cold, somewhere in the mid 30’s, but I didn’t want to pass up no wind and a little bit of sun for getting some outside flying in. I charged up half a dozen 2S batteries for my toothpick quad, and a couple of batteries for my boys’ RC cars, and we headed over to their elementary school which is only five minutes away.

I got the boys’ cars setup and they went off to do donuts and ramp off of the playground equipment, while I fired up my radio and goggles and put the first battery in.

It was a little rough getting started. I’m going to blame it on adjusting to the cold. I don’t wear gloves when I fly. I’ve tried it a couple of times and it just messes with my muscle memory too much, even with a thin pair. I had a couple of near misses with trees and playground equipment at first, but by the end of the first battery I was feeling pretty good.

Flying at the school is nice for a couple of reasons. There’s the obvious one that it’s a bigger space with a nice large parking lot so I can keep the throttle more open and really get some speed up as I fly around. There’s also a lot more stuff to play with too. There’s light poles, trees, and playground equipment to fly around and over and through. So it makes it a lot more fun to do proximity flying than what I can do when I go down to the field near my home to fly where I do more loops, flips, and rolls since there aren’t many obstacles.

The second battery started out much better than the first as I was getting familiarized with the space. I made a couple of passes through the playground. I played around with following Thing One’s RC truck as he drove around a couple of trees, and then I took off to make a big looping pass through the playground. I misjudged my line through the obstacles though and pinged of a metal pole. It was a hard hit too as it was enough to cause the flight controller to reboot. I wasn’t worried though, I’ve had hard crashes before with my HX100 and it’s rarely had a problem.

Once the FC came back up, I armed it and tried to take off, but the quad just spun a bit and wouldn’t take off. I disarmed again and took off my goggles and put my radio down to head over. I figured there was some mulch from the playground stuck in a motor or maybe on of the receiver antennas got twisted and was blocking a prop. Both of those things have happened before in a crash, which usually takes a couple of seconds to fix and then I’m back in the air again. This time it was a bit more severe.

This is actually the second time I’ve broken a motor. The last time was in October, so I’m averaging one motor every two months. The October break was some a head-on crash into a heavy tree branch that broke the front right motor. Somehow this time I broke the right rear one. I can’t tell from the video playback, but I must have yawed a little as I hit the pole. It was a pretty hard hit too. I noticed when I got home and inspected the damage that I bent the motor bell and damaged some of the magnets.

I’m not sure if it was just a hard hit against a metal pole, or if the cold had anything to do with it. I feel like I’ve had some equally hard crashes flying my yard, but those collisions usually involve tree branches or wooden fences and not heavy duty playground equipment.

So that put an early end to my flying for the day. It was cold enough out though that my boys didn’t last much longer than that anyway, so I probably wouldn’t have gotten more than another battery in anyway. Just now I have to replace the motor.

It’s not hard to do since I’m using plugs and not direct soldering the motors to the flight controller, it just requires more disassembly than I want to do. I do have to take the canopy off and take the flight controller out because of the tight space that the motor wires and plug run through. I think the last time I did it, it took me a bit more than 20 minutes to do. At least I already have the parts, since these 1103 motors come in sets of four instead of being sold individually, and they’re interchangeable so I don’t need a specific motor at each position.

To be honest, I need to take it apart and do some work on it anyway. The antenna has had a couple of prop strikes on it, and I need to either switch back to some shorter tri-blade props that can’t reach the antenna, or make a change to the canopy so that the antenna stays above the props. I have an idea to drill a small hole through the back of the canopy a few millimeters above where the antenna currently sits so I can feed the antenna out at an angle. That way the canopy itself will keep the antenna from getting down into where the props can hit it.

Finding a Lost Quad

It was the first trip to the in-law’s farm after getting my HX100, and I was looking forward to trying it out where I had lots of open space. I’d already had a good set of flights with my Acrobrat flying all of the packs I had, before switching over to my HX100 and having fun with that one.

On my last pack for the HX100, I decided to see how far it could go given the lower power VTX, and flew it out to the edge of the empty field I was using.

You can see the line of darker green between the treeline to the right and the stand of trees left of center.

I got all of the way out to the stand of trees and backed to fly along the edge of the corn field next to the empty field I’d been flying over. The video signal was having a little bit of an issue but so bad that I couldn’t fly it. Still I didn’t want to push my luck further and possibly lose it in the corn field, so I turned back towards where I was flying from.

Looking back towards where I was standing, along the edge of the green field towards the right quarter of the picture.

Only a few seconds after turning back it failsafed and crashed. The impact tilted the camera up so the top half of the view was the inside of the canopy and the rest was some plants.

Totally not realizing some of the limitations of the receiver on the HX100 versus the one on my Acrobrat, I headed out into the field with the range check on my radio turned on so I could find it by playing a little game of hot and cold. I’d done that before when crashing my Acrobrat in a different spot and it had worked great. There was a big problem with my plan though that I didn’t realize until later. The FrSky receiver that came on the HX100 quad did not support telemetry, which is important because telemetry is how the radio displays a range strength value. So I was wandering around in this field looking at a zero number that wasn’t changing, and assuming it was because I just was too far away and not that it would never not be zero even if I was right on top of the quad. It wasn’t until I got to the edge of the corn field which I knew was well past where the quad had crashed that I finally realized my mistake.

I turned of my radio at this point and instead tried studying the video feed in my goggles to see if I could tell where the quad was. There wasn’t much to go on though, unless I got very lucky and saw myself walking by.

After a couple of minutes though the video feed cut out, and the battery had been totally drained. This was the point when I first thought I might not be getting the quad back. I was standing in the middle of a large farm field with no idea how to locate a nearly brand new microquad.

At this point I had two issues to deal with. First, I was well overdue to be back at my in-law’s house for lunch after which we were supposed to be heading home. Second, I had no idea how I was going to locate the quad. This was bad as beyond just losing an expensive piece of electronics, I was sure my father-in-law wasn’t going to want to have that sitting out in his field and then getting tilled under at some point and leaching into the soil. There’s a lot of stuff used in electronics that you don’t want in a soybean or corn field.

I drove back to the house and first let my wife know I wasn’t going to be able to leave just yet. Then I grabbed my tablet and an SD Card reader so I could more easily review the DVR recorded from the quad than I could from my goggles. I was hoping something in the video would help me locate it. Lastly I drafted my sons to come out and help me search.

I drove back out to the field I’d been flying with my search party. I watched the tail end of the flight video several times and thought I knew generally where it should be, so we started to hunt around in that park of the field but had no luck after several minutes. After looking at the video again, I finally realized I was misreading the tree line in the DVR video from right before the crash. It wasn’t the stand of trees at the east end of the field, but a gap in the treeline along the south part of the field where a gas line was buried. I had been looking in the wrong place all along and taken my search party back to the same spot and continued to look in the wrong spot. My oldest had actually been asking me about that other treeline after watching the video over my shoulder. He was very excited to be right.

The actual useful frame from the DVR before the crash with the gap in the treeline.

Once we started looking in the right part of the field, we found it pretty quickly. That actually surprised me, as I figured it would take some luck to see it among the ground cover that had been planted, but the black canopy and blue props stuck out pretty well from the brown and green.

I made a lot of mistakes trying to find my quad. I should have realized that I didn’t actually have telemetry on the quad. I should have had the tablet out with me from the start in case I needed to review the DVR. I also had made a mistake the week before when configuring the quad. I had turned off the setting in Betaflight that would cause the motors to beep when the receiver loses connection to the radio. I hadn’t ever needed it before since I’d rarely lost the receiver connection and could use the radio to turn on the beeping manually if I needed help finding it in the grass. I turned it off though because it was beeping whenever I plugged in a battery while it was connected to USB in order to make a VTX change without having my radio on as well. So one of the first things I did when I got home was turn that option back on.

Failsafe Crash Clip
Full Flight

Not a Yard Flyer

At this stage in my FPV journey it’s May and I’ve finally gotten my 3″ build back together on a new frame with all of the broken components replaced. Now the primary reason why I went for a build with 3″ props was because I’d heard that anything smaller than that didn’t really fly as well as a regular 5″ quad, but I didn’t really have the perspective at the time to understand what that meant for what I was actually looking for.

My yard is about two tenths of an acre, or just over 800 square meters, in size, and while not tiny it turns out is too small to fly a 3″ build in. Or at least too small for someone who’s just stepped up from flying whoops with brushed motors to a much larger quad with brushless motors. To illustrate what I mean, my AcroBee whoop weighs 30 grams with a battery, and my Acrobrat clocks in at 260 grams with battery, which is about half a pound. I can’t quantify the difference in speed involved between the two but it was very significant. So just like I started out the hard way by learning to fly indoors, I misjudged the amount of quad I needed for yard flying as well.

I tried addressing this by adding a throttle cut in my transmitter. This is a way of reducing the throttle by a percentage so that giving the maximum throttle on the stick would only have the quad go at say 90% of it’s real maximum. I gave 75% a shot first, then 60% and then 50% before I started to feel more comfortable. Even then, with the louder motors and the heavier weight, I just wasn’t comfortable flying the yard when my kids were out playing or there were neighbors outside. Hitting someone with a whoop won’t normally hurt given the light weight and prop guards, but hitting someone with a half pound inertia and 3″ spinning plastic blades would cause some damage.

Fortunately my kids’ elementary school is nearby and the grounds are open on the weekend. So I as able to make a few trips over there to fly the parking lot when it was empty. But that was just enough of a taste of getting to fly a bigger and faster quad, that it made flying the whoops around the yard on weeknights not as fun. So I started researching again to see about some of the smaller options for 2.5″ and 2″ quads to see what there was that would work better for me to be able to fly in the evenings after work where I wouldn’t have to drive anywhere.

This summer a new class of micro quadcopter known as a Toothpick designed by YouTuber KababFPV became very popular (he’s a dentist which is where the name came from). These were small quads with very light, usually about 70 grams, carbon fiber frames with 2″ or 2.5″ props. As this type of build started to take off, it seemed like it fit what I was looking for pretty well, but I struggled to find a good frame I liked and figure out what motors and other parts I needed.

Then in late August Is saw a review for BetaFPV’s HX100 and thought maybe that was worth giving a shot. It’s not a perfect build. I don’t like the way the VTX antenna in the back comes out even with the props, but the weight and size looked good so I thought I’d try it out.

Flying a toothpick-style quad in my yard was a completely different experience from my Acrobrat right from the start. It’s about 72 grams with a 500 mAh 2S battery, so about twice as heavy as a whoop instead of 8 times as heavy. It would still hurt if I hit someone with it but I don’t think it would cause any injuries, and hopefully I never have occasion to find out. With 2″ props on it and 1103 motors, it’s not nearly as loud either, so I don’t worry about flying it when my kids are out playing or there’s a lot of traffic in the neighborhood.

So the HX100 has been the perfect yard flyer for me. From August on I started keeping half a dozen 2S batteries charged so I could go outside after dinner and get in about half and hour of flying around the house whenever the weather permitted.

In hindsight it makes sense that what I was looking for in a yard flyer isn’t really what most people were talking about online when they were talking about smaller quads. I think I was just a few months ahead of the curve as the whole microclass of quads personified by the toothpick design has really exploded in the last few months. I just didn’t know then what kinds of questions I should be asking and I didn’t have any frame of reference to evaluate the information I was finding. Which is part of the fun of the hobby for me, it’s a constant learning experience.