Pacejka

Articles, guides, and products tagged "Pacejka" — a combined view of every catalogue resource on this topic.

User guide

Aerodynamics of an electric scooter as an engineering discipline: F_drag = ½·ρ·v²·CdA, decomposition into pressure/friction/induced/interference, Reynolds regimes (rider Re ≈ 10⁶, wheel Re ≈ 6×10⁴), CdA breakdown (rider 60-75% + frame 10-15% + wheels 5-10% + bag 0-15%), measurement methods (wind tunnel + coastdown ISO 10521 + power-meter Martin 1998), yaw-angle dependence Cy, why wheel aero on 8-10" differs from bike/moto, body-position tradeoffs vs stability, P_drag > P_roll crossover ≈ 19 km/h, fairings engineering and EU L1e, vehicle-class CdA table

Why a standing upright rider posture on an e-scooter is the worst CdA configuration among all personal vehicles (typical 0.55-0.70 m²), and why that means drag power begins to dominate rolling resistance from just 18-22 km/h — whereas a tucked motorcyclist only reaches that crossover at ~50 km/h. This article does not repeat the user-facing wind protocol from [Riding in windy weather](@/guide/riding-in-wind.md) and is not the same as the [energy-budget model](@/guide/real-world-range-energy-budget.md) — it is the **engineering foundation under both**: the formal drag equation F_drag = ½·ρ·v²·CdA with decomposition into pressure/friction/induced/interference, Reynolds regimes for the rider (L ≈ 1.7 m → Re ≈ 10⁶ at 25 km/h: turbulent boundary layer) and wheel (R ≈ 0.1 m → Re ≈ 6×10⁴: subcritical regime, drag crisis Re ≈ 3×10⁵ unreachable); CdA breakdown by component (rider 60-75% of frontal silhouette 0.4-0.55 m² + frame/deck 10-15% + wheels 5-10% + bag/cargo 0-15%), extrapolated from Crouch et al. 2017 J. Fluids and Structures 74:153-176 cycling aerodynamics state-of-the-art review and Bert Blocken et al. (TU/e + KU Leuven) bicycle-pose CFD studies; three measurement methods (wind tunnel low-speed automotive Eppler-section; coastdown ISO 10521-1:2015 + SAE J1263/J2263; power-meter regression Martin et al. 1998 J. Applied Biomechanics 14(3):276-291) with accuracy bands; yaw-angle dependence — Cy reaches 0.6-0.8 at 15-20° yaw, explaining catastrophic crosswind behaviour; wheel aerodynamics on small 8-10" wheels — why disc-vs-spoke difference is <2% drag (vs ~5% on 700c bike wheels) because of small frontal area; body-position tradeoffs — tucked posture possible but constrained by deck length and vibration absorption; power crossover P_drag > P_roll for CdA 0.55 + Crr 0.012 + m_total 105 kg at v ≈ 19 km/h (below it P_roll dominates, above it cubic P_drag dominates); fairings engineering — CdA reduction potential 25-40%, but crashworthiness penalty + EU L1e enclosure rules; vehicle-class CdA table for context (cyclist tucked 0.20-0.25; cyclist upright 0.45-0.55; e-scooter rider 0.55-0.70; motorcyclist tucked 0.30; auto 0.6-0.8). ENG-first sources (0 RU): Wilson «Bicycling Science» 4th ed. MIT Press 2020; Martin et al. 1998 J. Applied Biomechanics 14(3):276-291; Crouch et al. 2017 J. Fluids and Structures 74:153-176; Blocken et al. TU/e + KU Leuven cycling CFD; Hoerner «Fluid-Dynamic Drag» 1965; ISO 10521-1:2015; Anderson «Fundamentals of Aerodynamics» 6th ed. McGraw-Hill 2017; Schlichting & Gersten «Boundary-Layer Theory» 9th ed. Springer 2017; SAE J1263 and SAE J2263.

14 min read

User guide

Anti-lock braking system (ABS) engineering for e-scooters: longitudinal dynamics, slip ratio λ, modulator architecture, wheel-speed sensors, ECU control loop, and why 8-10-inch wheels require different calibration than motorcycle ABS (Bosch eBike ABS 2018 → Blubrake → Niu KQi 4 Pro 2023 → NAMI Burn-E 2 2024)

Anti-lock braking system (ABS) is a closed-loop service that keeps wheel slip λ = (v − ωR)/v within the peak-friction window (10-20% per Pacejka «Tire and Vehicle Dynamics» 3rd ed. 2012, Butterworth-Heinemann), instead of letting it slide into 100% lockup. The canonical [«Brake system engineering»](@/guide/brake-system-engineering.md) article covers hydraulics, friction materials, and DOT fluids; §8 there mentions eABS in three paragraphs — this deep-dive expands that section into a full 11-section discipline. Why e-scooter ABS is harder than motorcycle: a wheel of radius R=0.1 m vs R=0.3 m for a motorcycle has roughly `(0.1/0.3)² ≈ 11×` less polar inertia `I_w = ½·m·R²`, which means **lockup in <100 ms** from peak-μ instead of ~300 ms on a motorcycle. The modulator needs a higher ECU sample rate and a faster actuator (solenoid valve dump time <15 ms). A wheel-speed sensor (tone ring + Hall-effect) with the same pole count delivers 3× lower absolute frequency at the same linear speed — resolution at 5 km/h requires proportionally more teeth. Control-loop architecture: slip-ratio estimator with reference vehicle speed via select-high (because an e-scooter has no GPS or auxiliary sensor), target slip 10-20% through a PI loop with anti-windup. Industrial implementations: Bosch eBike ABS (launched 2018-08-30, Magura-supplied hydraulic, initially Performance Line CX, now extended across most Bosch motors); Blubrake (Italian startup since 2017, single-channel front-only); Continental Engineering Services CSC-100; **Niu KQi 4 Pro 2023 — the first mass-market e-scooter with factory-fitted ABS** (Bosch supplier, front-wheel single-channel); NAMI Burn-E 2 2024 with ABS option. Test methodology — ECE R78 (UN ECE motorcycle Type Approval), FMVSS 122 (49 CFR 571.122 USA motorcycle), EN 15194 (e-bike type approval, ABS not required), EN 17128 (PLEV — also not required). EU Regulation 168/2013 for the L3e-A1+ motorcycle category >125 cc requires ABS, but PLEV / e-scooter fall outside that category. Cost-benefit: BOM adds 200-400 USD to scooter MSRP. Stopping-distance improvement per Bosch field data: dry tarmac 5-12%, wet tarmac 15-30%. Sources ENG-first (0 RU): Bosch eBike Systems press release 2018-08-30 + product pages; Blubrake whitepapers; Continental Engineering Services portfolio; Niu KQi 4 Pro 2023 launch coverage (Electrek, The Verge); UNECE R78; 49 CFR 571.122; EN 15194; EN 17128; Pacejka «Tire and Vehicle Dynamics» 3rd ed. 2012; Limebeer & Sharp «Bicycles, motorcycles, and models» IEEE Control Systems Magazine 26(5):34-61 (2006); Cossalter «Motorcycle Dynamics» 2nd ed. 2006.

15 min read

User guide

Mass distribution, center of gravity and longitudinal load-transfer engineering on an e-scooter: static F_z,f / F_z,r, dynamic ΔN = m·a·h/L, wheelie / stoppie thresholds, anti-squat / anti-dive geometry and optimal brake bias

Mass distribution is the invariant through which all longitudinal forces pass: what the motor creates, the brake dissipates, and the tire transfers to the road **fundamentally depends on the static F_z,f and F_z,r at the wheels and on the dynamic ΔN = m·a·h/L under acceleration or braking**. The canonical [«Brake system engineering» article](@/guide/brake-system-engineering.md) unpacks caliper hydraulics; [«ABS engineering»](@/guide/anti-lock-braking-system-engineering.md) — the control loop that keeps slip ratio λ in the peak-friction window; [«Smooth acceleration and throttle control»](@/guide/acceleration-and-throttle-control.md) — rider technique for launch with weight-transfer control. This deep-dive is a distinct engineering-axis that consolidates these three rider-side contexts into a single mass-distribution design discipline: where to mount the battery (deck vs stem), what wheelbase to target (1000 mm vs 1150 mm), what optimal brake bias looks like (≈70/30 vs 50/50), why an e-scooter with short wheelbase L=1000 mm and high CG h=1.2 m has **2-3× the load-transfer sensitivity of a motorcycle** with L=1400 mm and h=0.7 m. Newton's framework: a rigid body has F = m·a and ΣM = I·α; static normal forces F_z,f = mg·b/L and F_z,r = mg·a/L (where a, b are distances from CG to the front / rear axle); dynamic transfer ΔN = m·a·h/L under longitudinal acceleration. Canonical engineering sources ENG-first: Gillespie «Fundamentals of Vehicle Dynamics» SAE 1992 ISBN 978-1-56091-199-9 §1.5 (axle loads), §3 (acceleration performance), §4 (braking performance); Cossalter «Motorcycle Dynamics» 2nd ed. 2006 ISBN 978-1-4303-0861-4 §6 longitudinal dynamics; Foale «Motorcycle Handling and Chassis Design» 2nd ed. 2006 ISBN 978-84-933286-3-4; Pacejka «Tire and Vehicle Dynamics» 3rd ed. 2012 Butterworth-Heinemann ISBN 978-0-08-097016-5 §1; Wong «Theory of Ground Vehicles» 4th ed. 2008 Wiley ISBN 978-0-470-17038-0; Genta & Morello «The Automotive Chassis» Vol 1 2nd ed. 2020 Springer ISBN 978-3-030-35634-0; ISO 8855:2011 axis convention; EN 17128:2020 PLEV; ECE R78 motorcycle reference.

15 min read

User guide

Speed wobble and weave instability on e-scooters: two eigenmodes of two-wheeled vehicle dynamics, eigenvalue analysis of the 4-DOF linearized model (Whipple → Sharp → Meijaard 2007 Proc. R. Soc. A), why 8-10-inch wheels and a high h/L mass-center ratio produce 6-10 Hz wobble at 35-45 km/h, three damping mechanisms (tire side-slip + headset preload + steering damper), diagnostics and rider recovery protocol

Stability at speed is not a question of grip strength but a question of the eigenmode spectrum. A two-wheeled vehicle (bicycle, motorcycle, e-scooter) under forward motion has a linearized 4-DOF model from Whipple (1899) → Sharp (1971) → Meijaard, Papadopoulos, Ruina, Schwab (2007) Proc. R. Soc. A 463:1955-1982 whose eigenvalues yield **two oscillatory modes**: weave (2-4 Hz, lateral inverted-pendulum oscillation of the entire frame with steering in phase) and wobble (6-10 Hz, pure steering-only oscillation with the frame nearly stationary). Depending on forward speed `v`, the real part of one or both eigenmodes passes through zero — a bifurcation where the mode flips from damped to undamped, and any small disturbance (road irregularity, gust crosswind, rider input) excites self-sustained oscillation. Why e-scooter parameters (wheel radius R≈100 mm vs motorcycle 300 mm → 9× lower gyroscopic stabilization; h/L≈0.55 vs 0.35 → higher mass-center normalized to wheelbase → lower critical speed; m_rider/m_vehicle≈4-6 vs ~1 → rider dominates dynamics; headset preload often poorly maintained) shift wobble frequency into the 6-10 Hz range, where rider neuromuscular reflex (80-150 ms latency per Sharp 1971 and Cossalter 'Motorcycle Dynamics' 2nd ed. 2006) cannot stabilize phase and often makes wobble worse through positive-feedback transfer function. Three damping mechanisms — tire side-slip relaxation (Pacejka 'Tire and Vehicle Dynamics' 3rd ed. 2012), headset bearing rotational friction (preload-dependent, ISO 12240 angular contact specs), and external steering damper (hydraulic as in MX/motorcycles, OEM on Dualtron X2 + Wolf King). Diagnostic weekly 3-point play-check (headset move-test, fork twist-test, wheel-bearing rock-test). Rider recovery protocol at speed is counterintuitive and opposite to instinct: **do not grip tight (gripping tighter couples rider-as-amplifier into transfer function and worsens wobble — Sharp 1971); relax hands gently, shift weight rearward onto heels on the rear third of the deck (reduces front-wheel load and thus trail-dependent wobble torque), clamp the stem with knees (couples rider mass to frame, raises effective damping ratio), apply rear brake only (front brake at speed worsens wobble through geometric + gyroscopic coupling per Cossalter 2006 §8.6), and ease speed down to ~20 km/h where the mode naturally decays**. Manufacturer responses: Bird One geometry update 2019 (more conservative head angle after reports of high-speed wobble per IIHS micromobility data); Lime Gen 4 longer wheelbase; hyperscooter class (Dualtron X2, Wolf King GT Pro) ship with hydraulic steering dampers as standard. ENG-first sources: Meijaard et al. 2007 Proc. R. Soc. A 463:1955-1982 DOI 10.1098/rspa.2007.1857; Sharp 1971 JMES 13(5):316-329; Cossalter 'Motorcycle Dynamics' 2nd ed. 2006; Schwab & Meijaard 2013 Vehicle System Dynamics 51(7):1059-1090; TU Delft Bicycle Lab; Pacejka 'Tire and Vehicle Dynamics' 3rd ed. 2012; NHTSA HS-810-844; IIHS Status Report 2022.

13 min read

User guide

E-scooter tire engineering: contact patch, rolling resistance Crr, Kamm circle, rubber compound, and ETRTO / ISO 5775 / DOT FMVSS 119 / EN 17128 / UTQG standards

Engineering deep-dive into the e-scooter tire subsystem — parallel to the introductory «Suspension, wheels and IP-protection» reference: contact-patch physics (p_infl · A_contact ≈ W_load — hydrostatic balance), rolling resistance (Crr = F_rr / N — 80–90 % from hysteretic loss in viscoelastic rubber, 10–20 % from aero and bearings), Kamm/friction circle (F_lat² + F_long² ≤ (μ · N)² — fundamental simultaneous-grip limit), slip ratio and slip angle plus Pacejka Magic Formula (cornering stiffness Cα with 3–6° peak), hydroplaning physics (Vp = 10,35 · √p — NASA TN D-2056 1963 for aviation tires, ~ 0,5 × NASA-formula realistic for scooter pad geometry), polymer compound composition (NR natural rubber from Hevea brasiliensis, SBR styrene-butadiene 23–40 %, BR butadiene, halogenated butyl IIR/CIIR for tubeless airtight; silica vs carbon black filler with BET surface area + Si69 coupling agent; sulfur vulcanization vs peroxide; Shore A hardness 50–80 + Tg glass transition; magic triangle wet grip ↔ rolling resistance ↔ wear), casing construction (bias-ply 45–60° crossed vs radial 90° + circumferential belt — 30 % bigger contact patch in radial at 22 psi per Schwalbe testing; TPI 60/120/240+, aramid/nylon belt, hookless TSS vs UST), tread patterns (slick / semi-slick / multi-block off-road, evacuation grooves), tubeless sealant chemistry (NR latex + 1,3-propanediol + viscous polymer in Schwalbe DocBlue / Slime / Stan's NoTubes — temperature range −20…+60 °C), and full comparison matrix of ≥8 safety standards (ETRTO Standards Manual 2024 + ISO 5775-1:2023 Part 1 dimensions + DOT FMVSS 119 49 CFR § 571.119 endurance test + UTQG 49 CFR § 575.104 treadwear/traction/temperature + EN ISO 4210-7:2014 bicycle rims/tires test methods + EN 14781:2005 racing bicycle + EN 17128:2020 PLEV § tire pressure marking + ECE R75 Rev 2 motorcycle/L-category + SAE J1100); engineering ↔ symptoms diagnostic matrix; 8-point recap.

18 min read