How to Check Energy per Hour for Shock Absorber Selection
Why the same absorber can pass single-impact energy but fail under high cycle frequency.
Direct answer
Energy per hour is the calculated energy per cycle multiplied by the number of impacts per hour. The selected model must satisfy both energy per cycle and energy per hour ratings, because repeated impacts create heat and duty-cycle limits.
Questions this page answers
- How do I calculate energy per hour for a shock absorber?
- Why does cycle rate matter for shock absorber selection?
- Can a shock absorber pass energy per cycle but fail in continuous operation?
Required inputs
Formula logic
Energy per hour
E is absorbed energy per cycle. ETC is the hourly energy load that must stay within the catalog rating.
ETC = E x (impacts per hour)Unit: N m/h
Calculation steps
- 1
Recognize the problem and its limits
After a speed or throughput increase, the absorber becomes hot, loses damping or bottoms out. Check energy per impact AND energy per hour, return time, alignment and cooling. Temperature alone does not establish the cause; compare measured conditions with model limits.
- 2
Collect the operating data
Weigh the complete moving assembly. Obtain speed at first contact from a trace or a safely recorded movement, rather than using the machine’s nominal speed. Count impacts at this individual stop during peak production. Measure usable travel and record whether a belt, queued pallets or an actuator keep pushing. Mark estimates and unknowns; send photos or a drawing when measurements are unavailable.
- 3
Worked engineering example — not a customer case
Assume one absorber stops a horizontal 50 kg load at 1 m/s, with no drive force during compression and 30 impacts/minute. Energy per impact = 0.5 × 50 × 1² = 25 J. Cycle rate = 30 × 60 = 1,800/h. Hourly energy = 25 × 1,800 = 45,000 J/h. These are assumed demonstration inputs, not your machine’s results.
- 4
Why one model is excluded
EK20x12 is listed at 31 J/cycle and 35,200 J/h. The 25 J impact is below its single-impact rating, but 45,000 J/h exceeds its hourly rating, so exclude it for this assumed continuous duty. A passing single-impact check cannot cancel a failed thermal-duty check.
- 5
What may enter the shortlist
EK25x25 is listed at 81 J/cycle, 77,000 J/h and 25 mm stroke. It passes only the two energy checks in this example and can enter further review if the mechanism accommodates its working stroke and mounting dimensions. This is not approval for installation.
- 6
Validate before ordering
Confirm effective mass and velocity range, peak transmitted force, allowable structural load, adjustment, full return before the next impact, alignment and thermal conditions. Record initial and stabilized temperature, cycle rate, stroke use and observed rebound during a controlled trial. Define acceptance limits with the machine designer; missing model limits require engineering confirmation.
Common mistakes
- Selecting only by maximum energy per impact.
- Using ideal cycle rate instead of maximum production cycle rate.
- Ignoring hot environments that reduce thermal margin.
Catalog source notes
- Illustrative calculation; EK20x12 and EK25x25 ratings checked against published EKD model records on 4 October 2026. J and Nm are equivalent energy units. Catalog ratings do not establish service life or application suitability.
Move from answer to model shortlist.
Use the sizing tool when you have the inputs, or send the application data for engineering review.