C-UAS Turret

Build Log/Pictures Below

I’m building a two-axis pan/tilt C-UAS turret designed to track and engage Class 1 drones in flight. This is the biggest build I’ve taken on so far. It’s purely a hobby project, not a to-market defense system.

Design Philosophy

The first constraint that shaped the whole project was bearings. There's a vast world of complex, expensive bearings out there. Slewing rings and crossed rollers only come in fixed catalog sizes and are insanely expensive with long lead times. I knew I'd need something beefy that could handle significant moment loading, especially on the rotational axis, so I actually found my big crossed roller slewing ring on eBay first and started designing everything else around it.

My default design philosophy is sheet metal first. It's cheap, fast to iterate on, and easy to design for manufacturing around, so it's usually the right call before reaching for anything more complex. But for this build I'm leaning on machined plate and brackets instead, because I've got access to a machine shop through my internship, along with a pile of scrap stock that would otherwise get tossed. For a one-off prototype like this, machining flat plate and brackets myself ends up cheaper for me.

Pan Axis

Once I had the main bearing picked out, I started designing from the ground up. I landed on a servo-driven timing belt design. The rotational axis, which I'm calling the C-axis, rotates on an RU145 crossed roller slewing ring, driven by a 1000W DC servo through a timing belt reduction, along with a neat little "omega drive" layout to hold a good wrap angle around the servo's drive pulley.

The driven ring is actually the stationary part; the servo and the rest of the assembly orbit around it instead. The reduction works out to roughly 8.3:1 (24T drive pulley to a 200T ring). Initially I pictured this ring as a machined aluminum disc, but I ended up switching it to a bolted sheet metal stack instead, mostly due to material constraints on the size I needed. RMFG cut it for me, and honestly they've been consistently beating out SendCutSend on both turnaround and price for these kinds of parts. 

The Tilt Axis

The tilt axis, which I'm calling the A-axis, is much harder and more complex than the C-axis. It's another timing belt driven design, this time with a 400W servo running a 15T to 88T reduction, about 5.9:1. I would have loved to run a servo with an integrated brake here, but sourcing constraints pushed me toward a brakeless unit instead, so I'll need to handle that with software shutdown routines for now. It's a prototype, so I can live with it.

Zooming in on the drive side, I machined the custom 88-tooth drive pulley for the HTD5M belt myself (turns out big timing pulleys aren't easy to source COTS). This part turned out great, and it's one of my favorite pieces on the whole turret so far. I think my ratio might be undersized here. Going to re-run calcs and potentially machine another. Process is proofed out though for easy iteration (same design just more teeth).

Electronics

The turret will run on a 48V bus feeding both servo drives, with an ESP32 handling real-time motion control over a step/direction interface. A separate RS485 channel handles diagnostics without touching the motion path, and a dedicated buck converter powers all the low-voltage electronics, so the turret's own control system is self-contained. There will be a laptop involved for running the vision system, just not for powering or driving the ESP32. Everything will live in a control cabinet I'm building out now, which is basically a Pelican case packed with electronics.

On the vision side, my buddy who does this professionally is designing the vision system. We're starting from a simple OAK-1 camera unit that, through his work, gets trained on drone models and will integrate with my hardware to actually track them.

Where It Stands

Right now I'm still working through the hardware: powering up the servos, confirming both axes actually move the way they're supposed to, and finalizing the A-axis design and payload mounting. There's a lot left to do, but I expect this thing to really start coming together over the next couple of weeks. Waiting on vendors for a lot of hardware!!

Payload/Tactics

Right now, I’m planning around an M4-style platform as the baseline. It’s a well-established, modular option with plenty of existing components and room to scale magazine capacity. Later on, I may experiment with a magazine-fed shotgun platform instead. That would introduce some interesting tradeoffs, particularly between shot spread, effective range, and capacity. I'm designing the payload to mount on picatinny rail, so dropping in a different platform should be relatively straightforward. That said, I have not yet built out the fire and control mechanism.

At the end of the day, the specific use case and tactics aren’t really the point. It’s a hobby project, and I’m much more interested in the engineering challenges and lessons learned along the way.