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For a bending fatigue test for a bicycle fork, according to ISO 4210-1, The number of cycles should be 120,000 for stage one of the bending fatigue test and 100,000 cycles for stage 2 of the test.

How long would this test typically take based on the number of cycles? Do the number of cycles equal a certain amount of seconds?

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  • I suspect you know this, but for other readers: you have to pay to access the actual ISO standard. This is why Criggie's answer says "I suspect that it will be something like" rather than quoting from the actual standard.
    – Weiwen Ng
    Mar 12 at 0:32

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The ISO standard will have all the requirements documented.

I suspect that it will be something like

A random selection of 5 out of every 10,000 forks must be subjected to bends alternating in the fore AND aft direction at least 100,000 times with a displacement of 20.0 mm at a right-angle to the steerer tube centerline. There must be no sideways or rotational forces applied. Both fork tines/legs must be exercised in the same direction at the same time. A hub or other clamping structure must be used between dropouts.

Automated testing MUST keep an accurate count of the force required to deflect the fork every cycle. All forks will be serialised accurately, and batch information MUST be associated with fork production.
These records MUST be kept for 20 years for all test samples after the final date of manufacturing of this model.

(note these are not authentic words from the ISO standard - merely an example)

So you can test your fork as hard and fast as you like, but the test rig has to prove that you did at-least the minimum count, by the minimum deflection. And you have to keep those records for decades.

There are a bunch of videos showing bicycle test equipment at https://www.google.com/search?q=bicycle+fork+testing+machine+youtube

This shows a fork tester doing approximately 4 Hz.
120,000 cycles would take around 30,000 seconds or 8.4 hours plus setup time. You could set a test going at the end of a work day and come in the next morning to find it completed.
Or one machine could test two forks every 24 hours with turnaround time.

Here's a screenshot of a test controller showing 2Hz, of two tests a second, or ~500 ms per push/pull test.

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From

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