"SMOKE Link" ® 5A Dual-Throttle Controller
"SMOKE Link" ® 5A Dual-Throttle Controller
“Ever Thought About Letting Your Co-Pilot Run the SMOKE?”
Have you ever considered giving your co-pilot the chance to call “Smoke On!” right alongside you?
The Combiner Box makes that possible — safely, cleanly, and without electrical cross-feed.
It allows both Pilot and Co-Pilot to command the same smoke pump from their throttle-mounted switches, using isolated circuits that merge through a protected dual-diode network.
Train your co-pilot to manage the show, time the passes, or handle the cues while you fly.
Put your co-pilot to work — and make formation, airshow, or practice flying more interactive, disciplined, and fun.
The Combiner Box is fully compatible with all 3D Stick & Rudder smoke-throttle overlays as well as with smoke-switch inputs from other common vendors.
What began as a custom solution for one RV-8 formation leader has become a compact, flight-tested module that brings dual-seat smoke control to any experimental aircraft.
The "SMOKE Link" ®
Made by a pilot for pilots, the “SMOKE Link®” Combiner Box is designed, printed, and assembled in the USA by Swearingen 3D Works of Marion, IA, and distributed directly by the designer. Each unit is individually printed, wired, and tested only after order—built with the same precision and reliability I design into the RV-8 smoke system throttles.
⚙️ PURPOSE
The Combiner Box merges both Pilot and Co-Pilot smoke-switch inputs into a single, protected pump output for smoke systems drawing 5 amps or less.
Inside its sealed enclosure, a solid-state network isolates each switch circuit while combining both into one output—preventing cross-feed and ensuring safe, independent control from either throttle.
🧰 DESCRIPTION
Each Combiner Box incorporates:
One solid-state circuit, thermally bonded to a series aluminum heat sink, rated for 5 A continuous and 10 A peak (10 seconds).
Three feed-through terminal blocks for Pilot and Co-Pilot inputs, feeding one the pump output.
3D-printed PLA+ silver enclosure, factory-sealed and non-serviceable.
Internal wiring: all 18 AWG TEFZEL, solder-terminated and continuity-checked before closure.
Included flat-bladed screwdriver precisely matched to the terminal screws for proper field wiring.
⚡ ELECTRICAL SPECIFICATIONS
Nominal System Voltage: 12 V DC
Continuous Current: 5 A (10 A peak for 10 s)
Intended Application: Smoke pumps drawing ≤ 5 A
Isolation: Independent Pilot / Co-Pilot inputs via dual solid state junctions
Output: Single +12 V feed to smoke pump
📏 MECHANICAL
Length: 102 mm (including mounting lands)
Width: 58 mm
Height: 28 mm
Weight: 1 ¾ oz (≈ 50 g)
Material: PLA+ printed silver
Finish: Natural print texture (no coating)
Mounting lands pre-configured for #8 hardware with nutplate support.
Drill template included for accurate hole placement during installation.
🧩 FUNCTION
When either throttle-mounted smoke switch is activated, current flows through one side of the solid-state package to the common output, energizing the pump.
The network prevents voltage back-feed between switch circuits, ensuring dual-seat safety and operational integrity.
✈️ FEATURES
Designed for smoke pump systems drawing 5 A or less
Combines dual switch inputs into one isolated power output
Compact, sealed enclosure for experimental installations
Factory-wired and continuity-tested
Includes matched terminal screwdriver
Designed and assembled in the USA by Swearingen 3D Works, Marion IA.
🧾 COMBINER BOX DISCUSSION
During a design review with an RV-8 builder and fellow EAA member, we evaluated installation practices and hardware options for this assembly.
We agreed that #8 panhead screws with washers and nutplate support provide the most secure mounting method.
The upper port side of the aft baggage compartment was identified as the ideal mounting location.
Signal wires from the pilot throttle quadrant originate from the 3D Stick & Rudder Throttle Overlays, while the installer fabricates the 18 AWG pump output leads to suit each aircraft installation. ( Shown in the attached photos, but not included in this article sale, are examples of the dual SMOKE throttle setups, those being the FORMATION lead throttles. All other 3D Stick and Rudder SMOKE throttles are also candidates for use with the SMOKE Link® Combiner.)
🚀 IN DEVELOPMENT — 15 A SYSTEM SMOKE CONTROL UNIT
A next-generation Smoke Control Unit (SCU) for smoke pumps rated above 5 A is currently being designed, manufactured, and tested.
This 15-amp version will extend the Combiner Box concept to higher-current systems, featuring integrated solid-state relay switching and thermal protection.
Flight testing is scheduled for early 2026, with customer release to follow successful evaluation.
📦 CONDITION
Mint, ready to install and function.
Wiring schematic, drill template, and terminal screwdriver included.
Non-smoker manufacturing facility.