Pocket Infinity

By Burning North on Sep 08, 2017

5 774  18 

With 4" quads becoming more popular over the past few months, I'd been keeping an eye out for a frame compact enough to run a 20x20mm stack, but with enough breathing room to keep the build relatively clean, and a top plate long enough to fit a top-mounted battery. So when I saw that GRVDIGR had begun selling the gorgeous Tombstone 4sX, I knew this was the perfect frame for me. Right after I ordered mine, I realized I'd forgotten to add spare parts and quickly placed a second order. Huge thanks to Corey at GRVDIGR for combining my orders and refunding the difference in shipping, a thoughtful gesture that I appreciated immensely. He's a standup guy. :)

This build is based on the XJB F428 stack from HGLRC, with the optional TX20 video transmitter mounted atop the flight controller. It's very similar to the VTX03, except it runs on lipo voltage instead of 5V, which made the wiring a hell of a lot simpler. The included antenna was a bit too short for this frame, but this one from Pyro-Drone fits perfectly. I put a small dab of solder on the U.FL connector to prevent it from working loose, and so far it seems pretty secure.

The frame has M3 mounting holes for the stack, but the XJB boards will only fit on M2 standoffs. Fortunately, GnarlyFPV makes a fantastic TPU adapter that fits snugly into the M3 holes on the frame and effectively reduces them to M2. The stack was a breeze to install, and the stretched-x layout left plenty of space to fit a 330µF capacitor on the ESC board with no risk of a prop strike.

I chose the new F20II 1408 3750Kv motors from T-Motor, for no reason other than being a sucker for marketing hype and a sexy color scheme. I matched them with HQ 4x4.3x3 V1S props and Rotorgeeks soft mounts. For a little extra bling -- and to match the color scheme of the videogame gun that gave this build its name -- I secured the standoffs with some gold screws I'd bought as spares for my in-progress 6" Alien.

The only challenging part of this build was securing the XT30 pigtail away from the props, as there's very little clearance from the rear standoffs. I wrapped the pigtail in heatshrink to protect it from the edge of the top plate, and used a pair of zipties that seem to be holding up well enough. As always, only more flights will tell me whether this works or not.

Pocket Infinity weighs in at 154g dry, and 208g with a Tattu 650mAh 3S pack. I did a few quick hover tests on Betaflight 3.2 RC4 today, and this thing jumps off the ground with far less throttle than anything else I've built. I have no idea if it could handle 4S without blowing itself apart, but it already feels like a monster on 3S.

Now all I have to do is become a halfway decent pilot...



Sign in to comment.
c.w.anderson   5 days ago  

A+ build! Very nicely done. I appreciate the detailed documentation, including how you solved certain problems. Great photos too.

Burning North   5 days ago 

Thank you! This hobby still involves a lot of winging it and figuring things out as you go, so I thought describing my various improvisations would be more helpful than just listing out the parts I used. I may actually retry this build with a slightly different part combination soon; I love the 4" ultralight category!

Mfost37   30 days ago  

Do you have any dvr footage? Im now considering a similar build :)

GRVDIGR   Sep 08, 2017  

Thank you for the kind words, amazing build man! Great work!

Burning North   Sep 08, 2017 

Thanks so much! This definitely won't be my last GRVDIGR quad. :D

Guides & Reviews

64 7,164  73
Jan 20, 2018

This is the 3rd revision in the "Wizard Killer" series of builds based on the Martian II frame. The original Wizard Killer was my response to the successful Eachine Wizard RTF quad. The Mark III supersedes the more budget oriented Wizard Killer Mark II and is the most featured packed, simple to build and powerful of the three. The base weight with props is about 326g and fully loaded with a battery..

Read more
7 2,129  3
Jan 10, 2018

At last, the Topsky F7X V2 is available. This is the updated V2 release which came 3 months after the failed V1 model from October, 2017. V1 had several issues and most reviewers declared it an utter failure. Did Topsky fix the issues and are these worth buying? Let's find out. On paper this sounded like a wonderful new goggle. Unfortunately we were let down. The displays exhibited ghosting, the..

Read more
Are you sure you want to unfollow this person?
Are you sure you want to delete this?
Click "Unsubscribe" to stop receiving notices pertaining to this post.
Click "Subscribe" to resume notices pertaining to this post.