Howo Mining Overlord ZZ5707S Max Gradeability 42%

Model: Howo Mining Overlord ZZ5707S Series 6×4 Wide-body Mining TruckRated maximum loaded gradeability: 42% (≈22.8°)Models: ZZ5707S3640AJ / ZZ5707S3840AJ (mainstream Howo wide-body mining trucks for open-pit mines)

1. Parameter Definition & Test Conditions (Critical)

1. Fully loaded (total mass 75t, curb weight 23t + payload 52t)

2. Dry, hard and flat paved/rock surface

3. Lowest gear (1st gear), low constant speed (≤10km/h), short-duration climbing

4. Air resistance neglected; only overcoming grade resistance and rolling resistance

5. Formula for grade percentage:Grade (%) = Vertical Rise ÷ Horizontal Distance ×100%

42% → tanθ=0.42 → θ≈22.8°. NOT 42 degrees!

✅ Distinguish two concepts:

• Ultimate maximum gradeability: short slope, hard ground, 1st gear, 42%;

• Engineering continuous design grade: recommended ≤30% (≈16.7°) for long-time heavy-load continuous uphill, with safety margin reserved.

2. Powertrain supporting 42% gradeability

• Engine: WD615.47, 371 hp, peak torque 1500 N·m @1100–1600 rpm. High torque at low speed, ideal for heavy-load climbing

• Transmission: HW19710 10-speed (or HW19712 12-speed) with auxiliary reduction box. High reduction ratio in 1st gear

• Axle: AC26 wheel-reduction axle. Wheel-end reduction further amplifies wheel torque; equipped with inter-axle and cross-axle differential locks to prevent slipping and improve traction

• Tires: 14.00-25 mining deep-tread wide-base tires for enhanced grip

3. Summary of gradeability for full Howo mining truck range

Customization note: Replacing wheel-reduction axles with higher gear ratios can achieve a modified ultimate gradeability of 45%~50%. Tradeoff: reduced maximum travel speed. Only suitable for short slopes, not long-distance haulage.

4. Key factors affecting actual on-site climbing performance

1. Road surface

   1. Dry hard rock: close to rated value

   2. Slippery, muddy or loose crushed stone: tire grip drops, practical usable grade falls directly to 25%~32%, slip risk increases

2. Slope length

   1. Short slopes (tens of meters): can approach the 42% limit

   2. Long continuous uphill (hundreds of meters): engine temperature rise and thermal derating; cannot sustain the ultimate grade continuously

3. Altitude

   1. Above 2000m elevation: diesel engine intake shortage causes power loss. Gradeability derates. For high-altitude mines, use original value ×0.7~0.8 for estimation

4. Overloading

   1. Payload exceeding rated capacity significantly reduces climbing ability

5. Tire wearWorn tread reduces traction and increases wheel slip on steep slopes.

5. Mine road design recommendations for engineering practice

1. Main continuous uphill haulage road: ≤30% (16.7°) recommended, upper limit for sustained safe climbing

2. Temporary short steep slopes at working face: maximum ≤35% (19.3°), slope length preferably ＜50m

3. Continuous operation on slopes over 40% is strictly prohibited. It causes overheating of transmission and braking system, damages gearbox and wheel reduction axles. Downhill braking risk also rises sharply.

6. Grade conversion table for feasibility study & road design