I can be wrong on this, but hasn’t a prototype not a thin oring between the tubes on the head side?
Thougt I read about it on the Taschenlampen-Forum. Would be a cheap elegant solution to keep them in place.
That could work. But I’d think you’d need 2 o-rings. One at each end of the battery tube to insure that the inner tube floats away from the outer tube at all points. You would also need slots in preferably the inner tube to keep the o-rings in place. I’m not sure the inner tube is thick enough for o-ring slots.
There are o-rings plenty thin enough. And for such a thin o-ring, not much of an indent in the tube should be needed to hold it in place. But, I still think it’s not the best solution. Then again, I’m not an engineer by trade, nor a machinist.
Edit: it has been pointed out to me that some may not get that “The English are best” is sharp irony, first published 1963. Please don’t take it literally.
Reminds me a bit of the Thorens turntable I bought with money from my first real job. Replaced the original head with a light-weight version. And drilled a lot of vent-holes in it. All in the name of losing weight. The downside was that you needed to stay away when playing a record. Slip-stream, you know. The Thorens was not IP8, of course. But that did not matter, because it was not bought to be an EDC.