Rotors & Rosin

Motors are one of those things that sounds simple until you start going down the rabbit hole. KV rating, stator size, stator height, magnet count, bell design ? it adds up fast and there's a lot of conflicting advice out there depending on who you ask. I spent probably four evenings just reading forum posts and watching teardown videos before I felt like I had a decent framework in my head.

What I Was Actually Building For

This is a 5-inch freestyle build, not a racer. I'm not trying to hit gate times or squeeze every millisecond out of a lap. What I care about is punch, smooth throttle response, and motors that won't cook themselves when I'm flying in August. I also run 4S because I've got a bunch of 4S packs that I'm not ready to retire yet, so that narrowed things down a bit.

The frame is a Diatone Roma F5 V2, which I picked up on sale. Five inch, roughly 225mm, pretty standard geometry. Nothing exotic. I figured with a solid budget frame I had more room to spend on motors without going completely over budget on the whole project.

Stator Size: The Part That Actually Matters Most

For a 5-inch freestyle quad on 4S, the general consensus is 2306 or 2207. Some people go 2306, some swear by 2207, and both camps have reasonable arguments. The first number is the stator diameter (23mm) and the second is the stator height. Taller stator means more copper, which generally means more torque and more heat dissipation area. On 4S freestyle, I landed on 2306 mostly because a few pilots I follow in the freestyle community use them and seem happy with the efficiency.

KV-wise, 2306 on 4S is typically in the 2400-2600 KV range if you're running 5-inch props. Lower KV with bigger props = more efficiency and less heat. Higher KV with smaller props = snappier response but runs hotter and eats packs faster. I went with 2450 KV as a middle ground. Didn't want to go too aggressive since I'm not doing race laps, just bashing around parks and open fields.

The Brands I Actually Looked At

I narrowed it down to three options. I'm not going to pretend I did some scientific comparison ? this was mostly reading reviews, checking build logs on Rotorbuilds, and asking in a couple Discord servers I'm in.

First was T-Motor F40 Pro IV. Well-regarded, smooth, lots of people use them. They're on the pricier end, like $22-24 per motor, and I'd need four obviously. For this build I was trying to keep motors under $80 total so that was already pushing it.

Second was XING2 2306 from iFlight. I've seen these in a ton of build logs and the price is better, usually around $16-18 each. The build quality on the ones I've seen in person looked solid ? good magnet retention, clean windings. A few people mentioned they're on the noisier side but that doesn't bother me at all.

Third option was some Brotherhobby motors that a guy in my local flying group runs. He raves about them constantly and his quad does sound pretty crisp. I looked them up and the Avenger 2306 model was in a reasonable price range. Less mainstream but not obscure.

I ended up going with the iFlight XING2 2306 2450KV. Mostly budget decision, partly because I found a good deal on a four-pack from an online retailer that brought them down to about $62 shipped. I'm not saying they're objectively the best, just the right call for where I'm at right now.

The Mounting and Wiring Part

Once everything arrived I spent a Saturday afternoon on the actual build. The Roma F5 V2 uses M3 screws for motor mounting, 16x16 and 30x30 stack mounting holes. Fairly standard. I did pre-tin the motor wires before I soldered them to the ESC pads, which I did NOT do on my first build and paid for it. Pre-tinning makes such a huge difference in getting clean joints without having to dwell the iron forever.

I use a TS80P iron with a fine chisel tip for most pad work. Temperature around 350?C for the motor wires, maybe up to 370?C for the thicker battery leads. I'm not a soldering expert by any stretch but I've gotten to where my joints look decent and don't fail ? which is really the only bar that matters.

One thing I messed up: I forgot to thread the motor wires through the arm channels before soldering them. Had to desolder one motor, thread the wire, and redo it. Annoying but not the end of the world. Write it on your hand if you have to ? thread wires first.

Bench Test Results

I did a brief bench test with props off before I buttoned everything up. Motors spin up clean, all four spinning the right direction (I'd set motor direction in BLHeli_32 beforehand, which is just a good habit). No weird oscillation, no cogging, temps felt fine after a 30-second high-throttle burst.

Full maiden is planned for this weekend if the weather cooperates. We've had a lot of rain lately and my usual flying spot turns into a mud situation that I'd rather not deal with. I'll do a follow-up post once I've actually put some packs through it and can give a real feel for how the motors perform in the air, not just on a bench.

What I'd Tell Someone Else Doing This

If you're picking motors for a similar build, just nail down your priorities first. Racing vs. freestyle matters. Battery voltage matters. How much you care about efficiency vs. raw punch matters. Once you know those things, the stator size and KV almost pick themselves. Don't let anyone tell you there's one perfect motor ? there are like fifteen motors that would work fine for a 5-inch freestyle build and the differences between them are way smaller than forums make it seem.

Also, buy from a reputable source and check that your motor shafts are actually straight before you mount them. I've gotten a bent shaft motor before (not on this order, thankfully) and it's a headache to catch after you've already soldered everything up.

More to come once I get some air time. Fingers crossed for a dry Saturday.

If you read my first build post, you already know I have a complicated relationship with electronics. That quad I built ? the one I was so proud of ? flew great for about three weeks before I managed to fry one of the ESCs during what I can only describe as an "aggressive test session" in my backyard. I hit a fence post, killed a motor, and apparently the brief stall was enough to push the ESC over the edge. White smoke, burning smell, and a very sudden end to the afternoon.

Here's what I learned about fixing it, because honestly the whole process taught me more than the original build did.

What Actually Happened (Probably)

My original build used a 30x30 AIO (all-in-one) stack ? a combined FC and 4-in-1 ESC board. It was a budget one, I'll be honest. I think I paid around $38 for it. The ESC side was rated for 35A continuous, which should have been more than enough for my 2306 motors, but after the motor stall the magic smoke came out of the rear-left ESC corner of the board. Under a magnifying glass I could see a scorched FET ? that small component that controls power delivery to the motor. Dead.

I looked into just replacing the FET. There are videos on YouTube of people doing this with a hot air station, and honestly the soldering didn't look impossible. But the part itself ? a NTMFS5C628NL or something similar depending on the board ? is like 40 cents, which is fine, but I had to buy 10 of them minimum, and I wasn't confident I could pull the old one cleanly without lifting a pad. I've already lost one pad on this build and it was not a fun evening.

So I decided to just replace the whole stack.

Picking a Replacement

This time I actually spent a week reading before buying anything. I'd originally grabbed the cheapest thing that fit my frame (a 30x30 mount, 20mm hole spacing, standard for most 5-inch builds). This time I wanted something with a little better reputation.

I ended up going with a separate FC and ESC rather than another AIO. Not because AIOs are bad ? plenty of people run them fine ? but because if one part dies again I only have to replace that one part. A 4-in-1 ESC on its own is cheaper than a full AIO stack, so it actually made sense financially too.

I went with a Speedybee F405 V3 for the flight controller. I'd seen it recommended a few times in the build threads I follow, and it has good Betaflight support, a USB-C port (huge upgrade from micro-USB, I hate micro-USB with my whole soul), and onboard barometer and OSD. For the ESC I paired it with a 45A 4-in-1 that uses BLHeli_32 firmware, which gives me more tuning options down the road when I actually know what I'm doing.

Total cost was around $85 for both, which stings a little, but it's genuinely better hardware than what I had before.

The Actual Replacement Process

This is the part where I want to be really specific because I made some mistakes and I want to document them.

Getting the old stack out was not as simple as I expected. On my build the stack is sandwiched under the top plate with M3 nylon standoffs, and two of the wires ? the motor wires on the rear left arm ? were routed kind of awkwardly and were short enough that I couldn't fully remove the board without either desoldering them at the motor or at the ESC. I chose to desolder at the ESC side. This meant I was working with free wires in a tight space, which was annoying but manageable.

I also had to desolder the battery lead. I've got an XT30 on this build ? it's a 3-inch-ish 4S setup, not a full 5-inch ? and the positive and negative wires are 12AWG silicone wire. Getting those old solder joints off cleanly took longer than expected. I need to buy better flux. The stuff I've been using is fine but I've seen videos of people using Amtech flux and the difference looks ridiculous.

One thing I did right this time: I took photos before disconnecting anything. I know everyone says this and I actually skipped this step on my first build and paid for it. This time I photographed every wire, every connector, every routing path before touching anything. Saved me probably an hour of second-guessing later.

The Re-Wire

Soldering the new stack went pretty well, mostly. The motor wires went on clean. I've gotten more comfortable with tinning wire ends first and then flowing solder onto the pad, rather than trying to do both at the same time. The battery lead was the hardest part ? thick wire, big pad, I had to hold the iron on there longer than felt comfortable, but the joints look okay. I'll do a proper pull test before I fly.

The FC to ESC interconnect on this stack is a 10-pin board-to-board connector which just clicks together, which is genuinely nice. No soldering there at all. The main signals I had to wire manually were the VTX and camera, which I'd already done before so that felt familiar.

Betaflight recognized the board immediately when I plugged in USB. That was satisfying in a way that's hard to explain if you haven't spent two hours troubleshooting a board that wouldn't show up in the configurator.

Where I Am Now

I've done bench tests and motor direction checks. Everything spins the right way. I had to re-do my rates and PID settings because the new FC wiped them obviously, but I'd actually saved my diff all from the old setup so it was mostly copy-paste with a few adjustments for the different gyro.

I haven't flown it yet as of writing this. Weather's been bad and also I want to do a few more checks first. I'm going to do a prop-off arm test, then a very slow props-on hover test in the garage, and then I'll take it outside. I'm trying to be more methodical than I was before, because I think some of my first-build issues came from going too fast.

Things I'm going to do differently going forward: keep a small log of every session, what I changed, what the conditions were, how it flew. I keep thinking I'll remember things and then I don't. Also I'm going to put ferrite beads on my VTX power leads because I've been getting some video noise that I think is ESC interference and I've been putting off dealing with it forever.

Anyway. Replacing a stack is not that scary. It's annoying, and it costs money, and desoldering 12AWG wire from a tiny board in bad lighting is not fun. But it's doable and I feel like I understand my own build better now than I did before I broke it. There's probably a metaphor in there somewhere but I'll leave that alone.

I'll post a follow-up once I've actually flown it. Fingers crossed for no smoke.

Quick background on me ? I'm Lisa, I picked up a little Eachine tiny whoop about a year ago and immediately got obsessed. I fly Betaflight, I've done some basic tuning, but I've always just flown stuff that came pre-built or bind-and-fly. Building from scratch is a whole different world and I want to document this project because I wish I'd found posts like this when I was starting out.

What I Ordered

I did probably way too much research before pulling the trigger. Here's what I ended up going with for this build:

• Frame: iFlight Nazgul5 V3 ? went with this because it's a true X layout, parts are easy to find, and the price wasn't insane
• FC/ESC Stack: SpeedyBee F405 V3 with their 50A 4-in-1 ESC ? a lot of people recommended this combo for beginners because the SpeedyBee app makes configuration less intimidating
• Motors: Xing2 2507 1800kv ? honestly maybe overkill for a first build but I got them on sale
• VTX: Rush Tank Solo
• Camera: Foxeer Razer Micro
• Receiver: ExpressLRS EP2 (running a Radiomaster Boxer so this made sense)
• Props: HQProp 5x4.3x3 ? blue ones because I wanted it to look cool, obviously

Total came out to around $280 shipped across a few different orders. I definitely paid a bit more than I needed to because I didn't consolidate my orders well, but live and learn.

The Soldering Situation

This is where I need to be really honest. I had never soldered anything before this. I watched a bunch of videos, I practiced on some old wire from a broken desk lamp, and I thought I was ready. I was not ready.

My first attempt at soldering the motor wires to the ESC pads looked like gray lumpy blobs. Cold joints everywhere. I actually posted a photo in a Discord server and someone very kindly told me my iron probably wasn't hot enough and I was taking too long on each joint, which causes the solder to just sit there instead of flowing properly. They suggested bumping up to around 380?C and moving faster with a small amount of flux paste on the pads first.

That advice changed everything. My joints on the second attempt looked genuinely shiny and smooth. I'm using a cheap TS100 clone iron I got off Amazon for like $35, and it actually works fine once I figured out the temperature issue. If you're building your first quad and you don't have a good iron ? don't buy the cheapest fixed-temperature garbage. The TS100 style pencil irons are worth the extra few dollars.

I also burned a small hole in my silicone mat because I set the iron down wrong. Minute one of the build. Great start.

Wiring Everything Up

The SpeedyBee stack actually made the FC wiring less terrible than I expected. There's a plug-in connector for the ESC to FC connection so I didn't have to solder those pins by hand. The VTX wiring was the most annoying part ? I had to solder four wires to a pretty small pad cluster on the FC and I definitely bridged two of them on my first attempt. Continuity check with my multimeter caught it, flux and wick cleaned it up.

Pro tip that I didn't know until an hour into this: check for shorts between your positive and negative battery leads BEFORE you plug anything in. I used my multimeter set to continuity mode and probed the XT60 before connecting the battery for the first time. It beeped. That was bad. Traced it back to a solder blob on the ESC I had missed. Fixed it, checked again, no continuity ? good to go.

I know this probably sounds obvious to experienced builders but nobody in the beginner guides I read made it sound as important as it actually is. Please check for shorts. Please.

First Power-On

I plugged in through a smoke stopper (a little inline fuse thing ? highly recommend, about $10, will save your components if something is wired wrong) and everything came on. No magic smoke. The FC showed up in Betaflight Configurator on my laptop, motors spun up when I tested them in the motors tab, and the camera had picture. I actually said "oh my god" out loud in my kitchen to nobody.

ELRS binding took me longer than it should have. I had the packet rate set wrong on the transmitter end and couldn't figure out why it wasn't linking up. Ended up being a mismatch between the firmware version on the EP2 receiver and my TX module ? updated both through the ELRS Configurator tool and it linked immediately after that. Firmware stuff is annoying but it's part of the deal.

Where It Stands Now

So the quad is currently in a "mostly done" state. I've got the basic Betaflight configuration done ? rates are set, switches are mapped, arm switch works, failsafe is configured to disarm. I haven't flown it yet because I'm waiting on a new set of motor screws. One of the ones that came with the Nazgul frame stripped out when I was mounting a motor (my fault, I over-torqued it) and I want all four motors secured properly before I take it outside.

I also still need to do the maiden flight tuning. I've watched a lot of Joshua Bardwell's Betaflight tuning content and I understand the theory of what D-term and P-term do, but I've never actually adjusted them on something I built myself with no idea what to expect. That's going to be its own post once I actually get it in the air.

What I'd Tell Myself Before Starting

If you're thinking about doing your first build, here's what I actually learned:

• Buy flux paste. Not just flux in solder, actual flux paste in a little jar. It makes a real difference.
• Get a smoke stopper. Seriously.
• Your multimeter is your best friend. Learn continuity mode.
• Join a Discord or forum before you start so you have somewhere to ask dumb questions without feeling judged. Most people are genuinely helpful.
• Budget extra time. I thought this would take a Saturday afternoon. It took parts of four evenings.

I'm really proud of this little pile of carbon fiber and solder even if it hasn't left the ground yet. More updates coming once I get those motor screws and actually maiden it. Fingers crossed I don't immediately fly it into a tree.