Muscle Group Assembly — Full Arm Build

Overview

A muscle group is a bundle of multiple fascicles working together to actuate one joint movement (e.g., biceps for elbow flexion). All fascicles in a group share a mechanical termination but have independent or grouped electrical control.

This document covers the full arm + forearm assembly with 2 control variants for comparison.

Arm Muscle Groups

Location Muscle Group Action Fascicles
Upper arm (front) Biceps Elbow flexion 3
Upper arm (back) Triceps Elbow extension 3
Forearm (palm side) Flexors Wrist/finger flexion 3
Forearm (back) Extensors Wrist/finger extension 3

Total: 4 muscle groups, 12 fascicles

Mechanical Assembly

Bundling Multiple Fascicles

Each muscle group contains N fascicles that:

  1. Stay separate along their length — individual PET sleeves maintain independence
  2. Interweave cores at the LOAD END — mechanical merging for shared pull point
  3. Share one ferrule — single termination point for the entire bundle
SIDE VIEW (muscle group):
                    
Fascicle 1 ──┐
Fascicle 2 ──┼──► [INTERWEAVE ZONE] ──► [SHARED FERRULE] ──► LOAD
Fascicle 3 ──┘

FRONT VIEW (bundle cross-section):
┌─────┬─────┬─────┐
│ F1  │ F2  │ F3  │  ← 3 separate fascicle tubes
│  ○  │  ○  │  ○  │  ← cross-section of cores inside
└─────┴─────┴─────┘
     ↓         ↓
  (interweave at load end)
     └────┬────┘
       FERRULE

Ferrule Application

  1. Interweave the nylon+kevlar cores at the load end (overlap ~20-30mm)
  2. Slide ferrule (0.8/1.8 round aluminum) over the interweaved cores
  3. Crimp with pliers — firm, even pressure