Narrow-Track Traverse

Documented route segments where passable width drops below standard platform width (1,800 mm). Measurements taken at narrowest point of each segment. Multiple passes confirm consistency.

Route	Segment (km)	Min. Width (mm)	Length (km)	Surface	Notes
Western Coast	60–100	1,400	40	Packed dirt, encroached	Coastal sage vegetation closure. Two-wheel platforms suitable.
Western Coast	240–265	1,350	25	Dirt track	Cliff-side narrowing. Sustained overhead clearance 2,100 mm. Standard platforms possible with care.
Divide Transit	18–42	950	24	Fire track, compacted	Historical fire suppression access. Overgrown with low shrub. Narrow and reduced-width platforms only.
Divide Transit	108–131	1,200	23	Loose rock, scree	High-altitude pass traverse. Unstable substrate. Reduced-width platforms strongly preferred.
Eastern Seaboard	77–94	1,100	17	Overgrown dirt	Deciduous canopy overhead 1,800 mm. Wet clay substrate in rainy season. Two-wheel platforms optimal.
Eastern Seaboard	156–181	1,350	25	Gravel, maintained	Historic rail line conversion. Ballast substrate. Standard and reduced-width platforms both feasible.
High Desert Corridor	94–115	1,050	21	Rocky two-track	Erosional arroyos. High rollover risk on camber. Narrow-width platforms only.
Grassland Loop	42–68	1,500	26	Grazed grass, rutted	Riparian boundary, fence-line passage. Mud substrate potential. Reduced-width platforms required for passage.
Broken Ridge	31–51	1,100	20	Rocky scree, loose	Technical single-track sections. Multiple hairpins. Two-wheel platforms strongly preferred.
Basin Complex	203–228	1,250	25	Caliche, compacted	Dry playa margin. Low vegetation. Narrow and reduced-width platforms feasible.

Standardized width classifications enable rapid feasibility assessment. Classifications based on contemporary unit specifications.

Width Class	Width Range (mm)	Typical Axle Config.	Load Capacity (kg)	Stability on Camber
Standard	>1,600	Four-wheel, dual-track	800–2,400	Excellent. High rollover threshold. Stable on moderate camber (>15°).
Reduced	1,200–1,600	Four-wheel, single-track or dual narrow-track	400–1,200	Good. Moderate rollover threshold. Marginal on steep camber (12–15°).
Narrow	800–1,200	Two-wheel or four-wheel narrow stance	150–600	Moderate. Low rollover threshold. Poor on steep camber (<12°). Requires active stabilization and speed modulation.
Ultra-narrow	<800	Two-wheel	60–250	Dependent on speed and gyroscopic dynamics. Unstable at low speed on camber. Stable when moving. Unsuitable for sustained high-camber terrain.

Two-wheeled platforms enable passage through segments inaccessible to wider configurations. Specifications compiled from active units in service.

Geometry and Mass

• Wheelbase: 1,200–1,600 mm. Longer wheelbase increases stability on loose substrate; reduces maneuverability in tight terrain.
• Ground clearance: 200–450 mm. Higher clearance required for rocky, root-obstacled, or washed terrain.
• Platform mass (empty): 80–180 kg. Lower mass increases maneuverability but reduces stability on side slopes.
• Tire width: 35–60 mm. Wider tires distribute load on soft substrate; narrower tires penetrate loose material less.
• Tire pressure sensitivity: Platform behavior highly responsive to tire pressure. Low pressure (<40 kPa) improves traction on loose substrate but increases rolling resistance; high pressure (>80 kPa) reduces rolling resistance but increases rollover risk on camber.

Load Capacity and Distribution

• Payload capacity: 100–250 kg depending on frame design and tire specification.
• Load mounting: Pannier configurations (low, symmetrical) provide best stability. Roof or high-center-of-gravity mounting dramatically reduces rollover threshold.
• Asymmetric load limits: Maximum safe asymmetric (single-side) load before loss of tracking stability is 15–25 kg. Loads exceeding 30 kg asymmetrically require immediate corrective steering input.
• Load-induced camber sensitivity: Loaded platform tip-over threshold decreases proportionally to load mass. Empty platform tip-over angle on level terrain: 55–65°. Fully loaded: 35–45°.

Gyroscopic Stability

• Speed threshold: Below 8–12 km/h, gyroscopic stabilization minimal. Platform requires active steering input to maintain upright position on slopes. Constant course correction required.
• Stable speed range: 15–40 km/h provides predictable gyroscopic stability on most terrain. Speed modulation is primary control mechanism for camber traversal.
• High-speed behavior: Above 40 km/h, gyroscopic stiffness increases. Platform becomes less responsive to steering input. Useful for stable-ground traverse but problematic on technical terrain.
• Implications for loose substrate: Loose gravel or scree requires speed selection within 12–25 km/h range to balance gyroscopic stability with traction control.

Wheel Configuration and Substrate Suitability

• Spoke wheels: Lower mass, higher vibration damping. Suitable for technical rocky terrain. Maintenance-intensive in wet conditions (rust, spoke breakage). Better surface feedback.
• Solid wheels: Higher mass, reduced vibration feedback. Minimal maintenance. Better performance on sustained high-speed traverse. Poor feedback on technical terrain. Increased mechanical stress on uneven routes.
• Hybrid configurations (partial spoke, reinforced rim): Compromise between mass and maintenance burden. Suitable for mixed-condition routes.

Matrix indicates platform accessibility by route and width class. Assessment based on measured segments and documented constraints.

Route	Standard (>1,600 mm)	Reduced (1,200–1,600 mm)	Narrow (800–1,200 mm)	Ultra-narrow (<800 mm)
Western Coast	All segments except km 60–100	Full route	Full route	Full route
Divide Transit	All segments except km 18–42, 108–131	All segments except km 18–42	Full route	Full route with speed constraints
Eastern Seaboard	All segments except km 77–94	Full route	Full route	Full route
High Desert Corridor	All segments except km 94–115	All segments except km 94–115	Full route	Full route with extreme speed modulation
Grassland Loop	Full route	Full route	Full route	Not feasible (km 42–68 substrate conditions)
Broken Ridge	All segments except km 31–51	All segments except km 31–51	Full route	Full route (km 31–51 narrow-track required)
Basin Complex	Full route	Full route	Full route	All segments except km 203–228

Lateral Stability and Rollover Threshold

Track width (distance between wheel contact points) is the primary determinant of rollover resistance on slopes. Narrower platforms have proportionally lower tip-over thresholds.

Width Class	Typical Track Width (mm)	Rollover Threshold (level ground, unloaded)	Rollover Threshold (15° camber)	Rollover Threshold (25° camber)
Standard	1,500–1,800	60–65°	45–50°	25–30°
Reduced	1,100–1,400	50–58°	35–42°	15–20°
Narrow	700–1,000	40–48°	25–32°	8–12°
Ultra-narrow	400–700	30–38°	15–22°	Below terrain-typical angles

Loose Substrate Performance

Behavior on loose material varies by platform width and speed:

• Gravel (30–50 mm aggregate): Standard and reduced-width platforms maintain tracking within 1–2 cm lateral deviation at 20–30 km/h. Narrow platforms require slower speed (10–20 km/h) for predictable tracking. Ultra-narrow platforms experience continuous corrective input requirement below 15 km/h.
• Scree and talus: Material shifts under platform. Narrower platforms penetrate deeper; wider platforms distribute load. Narrow platforms suitable where loose material depth <150 mm. Material depth >200 mm favors wider platforms. Two-wheel platforms excel on compacted scree talus where narrow path pre-exists.
• Wet clay: Adhesion loss is primary hazard. Platform width has minimal effect on adhesion stability; speed reduction is primary control. Low-pressure tires improve adhesion by 15–25%. Wide platforms less likely to sink on extended wet clay exposure.
• Sandy terrain: Sinking depth proportional to unit mass divided by contact area. Wider platforms with lower tire pressure (35–45 kPa) preferred. Narrow platforms acceptable on firm sand (salt flats, coastal); unsuitable on soft erg dunes.

Speed, Width, and Substrate Interaction

Platform stability on slopes and loose substrate is a function of three interdependent variables. No single variable can be optimized in isolation:

• High speed + narrow width + steep camber: Rapid loss of control. Gyroscopic stabilization provides false confidence. Rollover likely on material shifts.
• Moderate speed + narrow width + moderate camber: Active steering correction required continuously. Manageable on familiar terrain with known surface conditions.
• Low speed + narrow width + moderate camber: Gyroscopic stabilization absent. Constant steering input required. Steering correction demand increases rapidly. Feasible for short segments only.
• Moderate speed + wide width + steep camber: Most stable configuration for sustained traverse of high-camber loose terrain.

Practical constraint: narrow platforms must traverse steep loose terrain at speeds where gyroscopic stabilization is minimal. This creates a conflict. Resolution requires either platform width increase, terrain avoidance, or acceptance of heightened rollover risk with compensatory active stabilization.

Width constraints measured at documented segments using standardized procedure (narrowest point, perpendicular to traverse direction). Platform specifications compiled from units currently in service across all six routes. Performance characteristics derived from operational data and direct observation. Feasibility assessments based on direct traverse where possible; extrapolated from measured terrain conditions where complete traverse has not been conducted. Assessments do not account for seasonal variation (mud depth, vegetation growth, snow cover). Current data reflects post-precipitation substrate conditions.