Rexnord Tracks + RaptorX Onboard Mount

Goal

The biggest visual and functional upgrade. This is precision mechanical work — track alignment must be within 1-2mm or the chains bind. You’re ready for this after 8 weeks of fabrication.

Day-by-Day Tasks

Day	Task	Method	Notes
1	Order Rexnord chain + BaneBots	Bearing HQ, BaneBots	Rexnord D821K7-1/2G chain (20ft, $540), BaneBots BB-150 gearboxes x2 ($144), RS-775 motors x4 ($70), Sabertooth 2x25 ($125). Total: ~$980
1-2	CNC custom sprockets on Colex	6061 aluminum plate, end mill	Design in Fusion 360. CNC route on Colex. Most precise CNC work of the project — tooth spacing must be exact for Rexnord chain pitch.
2-3	Laser cut track pod frame plates	Laguna EX, 3/16” aluminum	Side plates for track pod housings. Include motor mount holes, axle holes, chain tensioner slots.
3-4	Assemble track pod frames	Weld steel internal structure + bolt aluminum side plates	Weld steel gussets for rigidity. Bolt aluminum sides for serviceability.
4-5	Install BaneBots gearboxes + motors	Bolt to welded mounts	2 motors per gearbox (dual-input). Test each gearbox before installing in pods.
5-6	Install Rexnord chain on sprockets	Thread chain, tension, align	ALIGNMENT IS CRITICAL. Chain must run straight. Use straightedge to verify sprocket alignment. Adjust tensioners until chain runs smooth with no binding.
6	Wire Sabertooth motor controller	Replace BTS7960 for track motors	Sabertooth gives smoother control + built-in current limiting. Wire to Arduino.
6-7	Bolt track pods to chassis (using Tier 3-ready mounting holes from Week 3)	SS bolts through pre-drilled holes	The holes you drilled in Week 3 pay off now — no re-machining.
7	Build RaptorX quick-release dovetail mount	CF-Nylon print, kinematic coupling	Print dovetail plate for J5 (head or chest mount). Matching plate for RaptorX. Thumbscrew lock. 5-second swap.
7	Test track drive	Sabertooth + RC	Run tracks on flat ground. Test skid steering. Verify track tension under load. Listen for chain noise — grinding = misalignment.

Skills Practiced

Precision CNC (sprocket teeth), chain drive assembly, Sabertooth motor controller wiring, mechanical alignment.

Print Queue

RaptorX dovetail mount (CF-Nylon) + ad-hoc replacement parts