Tehllama Neutron-R Budget Racer

By tehllama on Feb 01, 2020

17  749  4

For anybody interested in achieving a $199 top level racing build, this is what I have for you.
Admittedly, budget can be a bit of a misnomer, especially among racing quads, but I'm genuinely amazed at how good a racing quad I can build using various Black Friday sales.

This takes my ultimate dream build, but makes it work on a budget.

The genesis of these race builds is that I'm looking to be able to run multiple identical quads, and get extremely comfortable with their performance at the limit. Running higher quality parts is intended mostly to get maximally consistent performance more than trying to extract more from the quad in race conditions... but in the process I've learned where I can save a bit of cash, and end up at that same performance limit, which is awesome.

Frame - This frame is one of the best out there, the FPV-FlightClub Neutron-R. Dedicated 20x20 stack mounting, available in my preferred Hybrid layout (5" Stretch-X front, 6" True-X rear), which is a really outstanding handling setup. I do get to claim hipster status on being one of the first racers running hybrid geometry frames and suggesting to faster pilots to give it a shot, but this is one of the best implementations of that frame geometry.
The canopy on offer from FlightClub is a TPU unit, which looks pretty stunning with the sharkfin - and is arguably superior in the V2 flip-stick configuration. In tall grass the shark fin is less useful, but the flip-stick setups allows combining the aethetics of a MayDayFPV design with the better aero and turtle-mode capability of a flip-stick.
This one breaks the budget slightly - but you can very easily move to a FLightOne ARC-1 frame with the same build and save half the price - or move to a FlyFive33 Switchback and save a little bit of cash and weight.

FC - The flight controller stack bears mentioning, because despite it being a budget setup, the FC is remarkably good. The iFlight Succex-E FC is actually a great layout, offering a set of inverted UARTs with one TX and one RX for use with FrSky telemetry radios (XSR/R-XSR), which is extremely nice. MPU6000 performance is brilliant, and the overall form factor is solid... just wish it had M3 bolt mounting. While it lacks pit switch functionality, slapping a TinysLEDs pit switch onto the build is a breeze, and those happily mount to an AKK Race VTX and fit brilliantly. Only real complaint is the size of the blackbox storage - 8MB is really only enough for a minute of optimal logging, and really only one pack of sub-optimal (1K Gyro_Scaled) logging.

ESC - the Succex-E ESC is rated as a 6S ESC, and 35A burst for that. In practice, I'm not pushing these as hard, because running the cheaper 2650KV motors means that 5S is really the limit, and most of the time 4S actually works better. Upgraded to JESC on 48kHz, the smoothness is absolutely excellent.

Motors - In order to make the budget, I cleaned GetFPV out of their 3BH-2207 motors in the purple 2650KV configuration. These are remarkably light motors, come with awesome Titanium Nitride gold finished graded hardware, and produce savage amounts of power on 4S (5S is loopy, but I ran heavy throttle limits there). The lack of grippy bell tops are actually the only reason I don't consider these fully premium motors, as the multi-strand wiring means good copper density, they weigh even less than the BH R6 motors they run alongside, and produce massive power. About the only downsides are the bearing size, and that power draw from these high KV monsters can be excessive.

Propellers - Anymore, I've become a sucker for the Gemfan Hurricane props - 51499, 51466, and 51433 props have been brilliant on all my stuff. Because of the high KV of these motors (and because they come in purple), I'm absolutely loving the 51433 props - even though you wouldn't think they're the best high speed prop, this setup actually takes them right to the flutter point unloaded on 4S, and with throttle limiting 5S goes to that same spot, but the control, grip, and precision is amazing. I also run the 51466 props, and this setup is crazy fast - ditto with DAL T5145C. I'm still partial to DAL Cyclones, still liking the T5046C the best for when durability is a factor.

Radio Control - Me personally, I like running FrSky XM+ receivers, since they aren't generating potential EMI with telemetry. I only care about RSSI, which just requires a quick reflash, running the RSSI Aux Channel in Betaflight, and toss that in the OSD. The biggest upgrade to this, for those flying a Taranis, is actually updating the OpenTX firmware onboard - the latest build seems to have fixed the inconsistent and excessive latency on everything due to heartbeat mismatches - seems to have fixed that bug, and cleaned up the Betaflight channel response smoothing quite a bit.

Video I went with fairly cheap VTX hardware - AKK Race VTX, and Foxeer Lollipops spray painted purple. I'm beginning to think that running VTXs off 5V regulators is probably the real key to longevity, but for that level of effort I've been extremely impressed with the $10 VTXs. The real budget rescue item is moving to the Foxeer Razer camera - on 4:3 ratio (even with 16:9 goggles), these work brilliantly. For half the price of my preferred Predator cameras, it's easy to forget which quads have which, because the image quality is so good.

Firmware & Tuning: Betaflight 4.1 has been the answer, and is worth moving past 3.5.7 to me. Adding JESC for Bidirectional DSHOT capability (RPM Telemetry with each packet), that enables RPM filtering has worked extremely well for me - absolutely dialed. The tuning window is a bit different - I've used the sliders to set ratios that are, to me, very high P/D values and DBoost from DMin. The biggest change is actually reducing the I term gains, and Antigravity strength, which I never imagined I'd have to do, but it seems to have sorted the last little bit of seeing 'bumps' under high-G loading. High FF values just make it track setpoint even better, so that produces the closest feeling I've ever felt to the quad being an extension of my neurons. Really insanely good.

Budget : I was able to get these four built for under $200 each

These have exceeded my performance expectations - I'm pushing harder than I ever have thanks to these builds. I did not expect to actually improve as a pilot just because of these, but the confidence I have flying these above 9/10ths is the best I've ever experienced from a race quad. The most shocking part is that my budget target quads have basically been folded in alongside my unlimited budget quads for performance - just make a small throttle limit adjustment to account for the KV difference, and they are pretty much indistinguishable... which is an amazing thing.



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killerkoala   Feb 21, 2020  

hey this is the first project im planning to do. do you need a fpv goggles to fly this? and if it is better to get the goggles wich one should i get?

tehllama   Feb 21, 2020 

They fly LOS fine, but there are much lighter (and cheaper) builds that are better for that.
The second question is a bit toughter - I'm still using really cheap goggles (with expensive Clearview ground station, and a fleet of quads that dwarfs that cost), but I'd honestly say used HD3's, HDO(1)'s, Skyzone030-OLED, or going to DJI goggles and doing the analog module are probably the best answer.

kwadkenstine   Feb 01, 2020  

DA Fleet. If my eyes wernt already , they would be green with envy

tehllama   Feb 05, 2020 

Ha, thanks. Even Mike, the owner of FPV-FlightClub was amazed at how many of these I had.

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