another surprise






did you see it . . . ?

Innova pub 1953








also of interest:
Innova pub 1950 (one of the earliest advertisement of a Curta)

Wow, more prototypes. But I guess if you look at, say, modern flip cellphones, there is a huge variety even though they all have very similar internals...engineers and designers do like to tinker with the basic example, sixty years ago it was no different!

With respect to the utility, I think this particular change would have been a bad idea, personally. My (older) pin-sliders and (newer, or at least over SN5000) block-sliders alike bear the large part of the force I apply to them on their top and bottom surfaces, which allows the setting-shaft to remain unstressed - the slider is spinning the shaft without unduly pressing into it on one side.

In this prototype, I feel one would have to press down on the bump-slider rather hard in order to get enough grip to set the number; this would IMO put a bending stress on the setting shaft, and interfere with the action between setting-shaft and setting-number, causing friction.

Anyway, very interesting, thanks Murff.

... but it's a cool design!
And I don't think that the force is too much in this design, not more than with the rectangular setting knobs (and they have the teeth at the front - not top or down side of the knob).

SO I WANT THIS ONE

I have to agree that it looks very cool over the rectangular knobs.

I'd think that it might reduce the tendency to apply pressure perpendicular to the shaft when adjusting the knob due to the shape alone. The curved surface would transfer the force at a shallow angle since you'd be wanting to slide the knob up or down.

That unless you are a gorilla or the first tool you always reach for is a hammer...