Ludwig you've survived what I'm seeing as a dangerous inherent design flaw of the articulated spring girder I'm working with. There is the problem of uncontrolled rebound in any simple spring suspension not utilizing a shock to control the violent return of the fork assembly after spring compression and this can be dangerous, causing loss of control, but in most cases it's just very wearing to the ride of both bike and rider.
The significant danger of over compressing the springs and causing the forks steering crown down onto the tire is quite real using this fork when running a 26" wheel assembly. This particular design will allow this and as I've cautiously tested and you've violently experienced, the result of tire to fork lockup is rider ejection.
My thoughts for correction are to provide a positive "bump stop" to limit suspension travel well before tire to fork contact can possibly occur & also provide a certain degree of suspension rebound control as well.
The rake and trail of this fork and frame setup is rather straight up and down, much less fork angle compared to Pete's setup and I know this adversely effects the forks length of allowed travel cycle with the installed factory spring and design loads. A 24" wheel and tire combination would probably be a fool proof option for safe operation on this bike and fork setup.
I used a girder fork and leaf spring on my Simplex and that design simply won't allow enough spring compression to allow a tire to fork "strike" the top leaf is just to stiff for the relatively light weight placed on it to compress, thus the top leaf is the bump stop and taking this example to the coil spring isn't a great stretch either. A stronger spring coil of the same length could replace the existing spring it's true, though it might kick like a mule on rebound and absolutely require a shock be added.
I'm working on it, just a problem to solve.
Rick C.
