Ramp gear loads
There may be some confusion about what the nose wheel (and indeed the main gear) needs to cope with on a ramp takeoff.
It is not so much the high value of the load as the length of time the modest load is present.
On a VL at the max sink rate the vertical loads that the leg has to accept are obvious and designed in from the off.
What is different on a ramp is that the significantly lower load than that above is applied for a serious length of time. This means that the lower load can still close the oleo. If this happens shock loading will occur which is not acceptable. At high rates of closure of the oleo (heavy VL say) the damper does not have time to do other than act as a simple locked strut. (Imagine holding a car shock absorber in your hand – if you try and close it quickly it will appear rigid. If you apply a small load throughout the TV prog you are watching you can close (bottom) the thing no sweat).
With the Harrier the gear had never been designed for a ramp of course but we soon realised that it was not high loads but the time the loads were applied that affected how close we got to closure and shock loading. In the end luck was on our side and a small change in the SHAR nose damper characteristic was all that was needed. Funnily enough this was to avoid shock loading after leaving the ramp when the leg suddeny extended from nearly shut to free. To ease this effect the last few feet of the ramp have a reducing angle.
Out of interest the backup plan B was to pop a disposable, crushable collar round the leg to avoid bottoming shocks.
Happy days.