Add REV ION Build System documentation

- MAXSpline, MAX Pattern, Grid Pattern explained
- MAXTube extrusion sizes table
- 1in extrusion details
- Connection to Team 2890's standard build system

sources/2890/ion-build-system.md

@@ -0,0 +1,97 @@
+---
+title: "REV ION Build System — Team 2890 Structure"
+tags:
+  - hardware
+  - structure
+  - extrusion
+  - REV
+  - 2890
+  - ion
+type: hardware-spec
+owner: 2890
+status: active
+sources:
+  - "https://docs.revrobotics.com/ion-build"
+  - "https://docs.revrobotics.com/ion-build/structure/extrusion"
+---
+
+# REV ION Build System — Structure & Extrusion
+
+## Overview
+
+Team 2890 uses the **REV ION Build System** as their primary mechanical structure system. ION is designed to enable rapid iteration and reconfiguration without large budgets or extensive manufacturing resources. The system is built around the **MAXSpline** — a unique spline shape that combines bearing support with torque transfer.
+
+## Core Concepts
+
+### MAXSpline
+
+The MAXSpline is the foundation of the ION system. It appears in:
+- MAX Hubs (for bearing and sprocket mounting)
+- Live axle applications
+- Motion components (linear slides, rotations)
+
+The shape allows bearing support and torque transfer to be combined in a single feature — making mechanisms more compact.
+
+### MAX Pattern
+
+The MAX Pattern combines:
+- **#10 clearance holes** in a 1/2" pitch grid
+- **MAXSpline bore** every 2" down the length
+
+This pattern enables:
+- Easy bearing mounting with correct center-to-center distances
+- 1:1 power transmission with #25 chain or RT25 belting
+- Rapid prototyping with standard #10 hardware
+
+### Grid Pattern
+
+Some MAXTube features **three rows of #10 holes** on a 1/2" pitch grid. This is ideal for rapidly building structures with 1in brackets.
+
+## MAXTube Extrusions
+
+MAXTube is aluminum 6061 extrusion. Available sizes:
+
+| Size | Pattern | Length | Nut Groove |
+|------|---------|--------|------------|
+| 1/2 × 1/2 in | Grid | 47in | No |
+| 1 × 1 in | Grid | 47in | Yes |
+| 1 × 1 in (1/16" wall) | Grid | 47in | No |
+| 1 × 1 in (1/8" wall) | Grid | 47in | No |
+| 2 × 1 in Light | No Pattern / Grid | 47in | Yes |
+| 2 × 1 in | No Pattern / Grid / MAX | 3–47in | Yes |
+| 2 × 2 in | Grid / MAX / MAX+Grid | 47in | No |
+
+**Nut groove note:** On 1in sides, the nut groove holds #10 nuts in place where a wrench can't reach. Use **2×1 Standard** for secure bearing fit; **2×1 Light** where weight is critical.
+
+## 1in Extrusion (REV-21-1000)
+
+4-sided slot extrusion accepting standard #10 hardware including low-profile nylock nuts. No T-nut needed — slide #10 hex head through slot, adjust as needed. Can be tapped 10-32 for permanent mounting.
+
+Good for builds that don't fit the standard pitch patterns.
+
+## MAXSpline Bore Spacing
+
+For proper chain alignment: center-to-center distances are set for simple 1:1 #25 chain transmission. The MAX Pattern bore spacing every 2in makes this straightforward.
+
+## Connection to Training
+
+**For students:** The ION system replaces custom machining. Understanding:
+- **Why standardized patterns matter** — interchangeable parts, no custom drilling
+- **MAXSpline as a system** — one spline shape across multiple components (hubs, bearings, motion)
+- **Nut grooves eliminate blind assembly problems** — you can hold the nut while fastening
+- **Pitch grid = predictable spacing** — 1/2in pitch means you always know where holes line up
+
+**Related training modules:**
+- [[swerving-modules]] — MK4i mounts to this structure
+- [[motor-basics]] — how motors mount to structural extrusions
+- [[frc-mechanical-basics]] — understanding structural systems
+
+## Source Links
+
+- ION Build overview: https://docs.revrobotics.com/ion-build
+- Extrusion guide: https://docs.revrobotics.com/ion-build/structure/extrusion
+- Product catalog: https://www.revrobotics.com/ion-system/
+
+## Notes
+
+Chris and team use this as their standard build system. The compatibility between ION mechanical and ION electrical (SPARK Flex, NEO Vortex) means the whole robot — structure, drivetrain, and motor control — uses one integrated system.