In cranes, conveyors, winches, and bulk-handling machines, “brake shock” is rarely just a comfort problem. Hard braking can create measurable consequences: gearbox backlash impact, couplings tearing, rail wear, belt slip, structural vibration, and higher peak temperatures at the friction interface. If you’re seeing repeated lining glazing, cracked brake wheels/discs, or “mysterious” fastener loosening, the stop profile is often part of the root cause.
This article explains how to design cushioned (soft) braking in a way that is still safe and repeatable. We’ll focus on methods you can implement with real industrial brakes—especially electro-hydraulic drum brakes like YWZ13 and fail-safe disc brakes like SH—plus system-level measures (VFD coordination, staged braking, hydraulic damping, and mechanical compliance).
[Image Placeholder] Example stop profiles: “step braking” vs “two-stage braking” vs “S-curve braking” (deceleration vs time).
1) First, define what “shock” means in braking (deceleration and jerk)
Most shock complaints come from two things:
- High deceleration (stopping too quickly for the system stiffness and backlash)
- High jerk (deceleration changes too suddenly—torque goes from “zero” to “full” almost instantly)
Two simple definitions help you quantify the problem:
a=\frac{\Delta v}{\Delta t} j=\frac{\Delta a}{\Delta t}Where a is deceleration and j is jerk. Even if your average deceleration is acceptable, a very high jerk at the start of braking is what creates the “bang” felt in gearboxes and structures.
Quick reality check (numbers you can use in meetings): If a trolley travels at 0.8 m/s and stops in 0.2 s, the average deceleration is 4 m/s². If you stop in 1.0 s instead, it becomes 0.8 m/s². That change is often the difference between repeated mechanical impact and stable operation.
2) Convert “stop behavior” into torque demand (why braking time changes everything)
For rotational systems, braking torque is tied to inertia and angular deceleration:
T \approx J \cdot \alpha = J\cdot\frac{\Delta \omega}{\Delta t}So if you double stopping time, you roughly halve average torque demand—and you usually reduce peak shock as well (assuming your brake engagement is controlled).
Example (typical for conveyors and travel drives)
Assume equivalent inertia at the brake shaft is J = 80 kg·m². Brake engages at 500 rpm (ω ≈ 52.36 rad/s).
If you stop in 1.0 s:
\alpha \approx \frac{52.36}{1.0}=52.36\ \text{rad/s}^2,\quad T \approx 80\times 52.36 \approx 4189\ \text{N·m}
If you stop in 4.0 s:
\alpha \approx \frac{52.36}{4.0}=13.09\ \text{rad/s}^2,\quad T \approx 80\times 13.09 \approx 1047\ \text{N·m}
Same system. Same speed. A 4× stopping time reduces average torque demand by about 4×. That’s why cushioning is often a system design choice, not a brake size choice.
3) Identify where the shock is created (before you change hardware)
In field troubleshooting, shock usually comes from one of these patterns:
- Brake applies at high speed (no electrical pre-braking; brake is doing all the deceleration)
- Brake torque is “step-like” (no torque ramp, no staging, no control of engagement)
- Gearbox backlash impact (torque reversal / slack take-up right when brake clamps)
- Brake applies unevenly (alignment/runout issues causing a “grab” feeling)
- Control timing is wrong (VFD removes torque too early/too late relative to brake set)
[Image Placeholder] Torque vs time plot highlighting: (A) brake delay, (B) torque step, (C) backlash spike, (D) stabilized decel zone.
4) Cushioning method #1 (most effective): coordinate VFD deceleration + brake set at near-zero speed
If your mechanism has a VFD, the cleanest “soft braking” strategy is usually: let the drive handle most deceleration, then set the mechanical brake only when speed is very low (or zero). This minimizes heat at the brake and reduces shock because the brake is not trying to absorb the full kinetic energy.
Practical commissioning parameters to define:
- Deceleration ramp time (seconds)
- Brake set speed threshold (e.g., < 3–10% rated speed, application dependent)
- Brake set delay (ms) and confirmation (brake-open/brake-closed switch if available)
- Torque proving: keep a small holding torque until brake-closed is confirmed (common for hoists)
For fail-safe brakes like SH hydraulic fail-safe disc brakes, this approach keeps the brake in its “best role”: safe holding and emergency stopping, while routine decel happens electrically.
[Internal Link Placeholder] Link to your fail-safe brake article or SH product application notes.
5) Cushioning method #2: two-stage (two-step) braking torque
Two-stage braking applies torque in phases: a lower initial torque to remove speed smoothly, then higher torque to secure/hold. This reduces jerk and limits the backlash “bang.” It is widely used on bulk handling and some crane travel duties.
There are two practical ways to implement it:
- Dedicated two-stage brake design (mechanical/hydraulic staging built into the brake).
- Sequential actuation of two brakes (apply Brake A first, then Brake B after a defined delay).
In our catalog, an example concept is the YW-E two-step electro-hydraulic drum brake, often selected where “soft stop” is required to protect belts, gearboxes, and structures.
[Internal Link Placeholder] YW-E Two-Step Electro-Hydraulic Drum Brake (product page)
Starting settings (field-tunable, not universal):
- Stage 1 torque: ~30–60% of full brake torque
- Stage 1 duration: ~0.3–2.0 s (longer for higher inertia travel/conveyors)
- Stage 2: full torque to stop/hold
The correct values depend on inertia, speed, and allowable stopping distance. Validate with speed-time data and temperature checks (a “soft stop” that drags for too long can increase heat).
6) Cushioning method #3: hydraulic damping (use carefully in fail-safe systems)
Hydraulic damping can smooth movement of brake linkages or release cylinders, but you must respect a critical rule: do not compromise emergency apply performance. For fail-safe brakes, slowing the apply event too much can reduce safety.
When hydraulic damping is used safely, it is usually configured as one-direction control using a flow control valve with a check-valve bypass:
- Restrict flow in the direction you want to slow (often “release/open” to reduce shock at start-up)
- Allow free flow in the opposite direction (“apply/close”) to keep fail-safe response fast
If you restrict the discharge path (oil returning during apply), you may create back pressure and slow brake application—this is a common field mistake in hydraulic brake piping.
[Internal Link Placeholder] Link to your hydraulic piping layout article (return flow/back pressure/throttling).
7) Cushioning method #4: mechanical compliance (couplings, torsional elements) to manage backlash impact
Sometimes shock is not mainly about brake torque—it’s about drivetrain stiffness and backlash. When torque reverses or the brake clamps, clearance in gear teeth and couplings “closes” suddenly, creating an impact spike. Adding controlled compliance can absorb part of that impact.
One practical component used in industrial drivetrains is an elastic jaw coupling (for example, our LMZ-I elastic jaw coupling), which introduces torsional elasticity and reduces peak impact. This can be especially helpful in travel and conveyor applications where repeated stops create cyclic shock.
[Internal Link Placeholder] LMZ-I Elastic Jaw Coupling (product page)
Important caution: compliance can improve shock behavior, but it can also increase angular displacement before torque builds. For precision positioning or safety holding, verify that added elasticity does not create drift, overshoot, or control instability.
8) Cushioning method #5: friction pairing and surface condition (often ignored, but very real)
Two brakes with the same rated torque can feel very different in shock behavior because friction characteristics are different. Practical factors include:
- Friction material grade (organic vs semi-metallic vs sintered) and how μ changes with temperature
- Disc/drum surface finish (too rough can “grab”; too smooth can glaze then suddenly bite)
- Alignment/runout (uneven contact creates a “pulse” during engagement)
If you’re chasing shock reduction, confirm the mechanical basics first: correct air gap/clearance, correct surface finish, and no dragging. Cushioning can’t fix a brake that is misaligned or contaminated.
9) How to verify you actually reduced shock (measure, don’t guess)
Soft braking should be verified with data. A simple field measurement package is:
- Speed vs time (encoder or VFD feedback): confirm deceleration shape
- Brake command timing vs speed: confirm brake is not clamping at high speed unexpectedly
- Acceleration (optional) using a small accelerometer on gearbox housing or structure: peak g is a useful shock indicator
- Temperature trend after repeated stops: verify you did not trade shock for heat
Practical acceptance language many teams use internally: “No audible impact, no visible coupling backlash snap, peak acceleration reduced compared to baseline, and stabilized brake temperature does not increase.” Translate that into your own measurable thresholds during commissioning.
[Image Placeholder] Data example: baseline vs improved stop curve (speed-time) + corresponding temperature rise comparison.
Need a cushioning plan for your crane or conveyor brake system?
If you share your application (crane hoist / travel / conveyor), operating speed, estimated inertia, stops per hour, and your brake model (e.g., YWZ13 or SH), we can recommend a practical approach: VFD timing, whether two-stage braking is justified, how to configure hydraulic throttling safely, and which measurements to record to prove improvement.
[Internal Link Placeholder] Contact our engineering team for braking shock reduction and system tuning support.
