There are things I would like to know. And if I can't find the answers, I start looking for them, so to see how this light works I ended up buying one second handed. To help others interested I post here some findings.
Any pawning occuring in this report is undeliberate.
The X1-VB is a focusable dive-light made by MB-Sub, 3x AA with Cree XR-E. The lamp is mainly used for back-up light and signalling.
The same mechanical parts are used for the VB-50, as focusable canister divelight lamphead with a SST-50 led.
The maching and build quality is impressive. The mechanism is ingenious, simpe and not simple at the same time, ausgezeichnetes plan.
The fresnel lens is plastic, 2mm thick, the glass front lens is 6,5mm thick.
For maintenance you can and you should open the light now and then to clean from sand and check lubrication. The front bezel can be gently pulled to free the focusing assembly from the lamp. Two o-rings are to prevent water ingress, the third o-ring locks inside a groove, to prevent the focusing assmebly to fall out from the lamp.
By turning the ring on the front, the beam width changes. You can keep turning in any direction until you drop, changing the beam endlessly from narrow to wide and from wide to narrow etc.
The focusing system consist of a cylindrical slide that travels between lens and led.
The slide moves in axial direction, as it is the only way it is free to go. Its fixated in radial movement by two sliding rods that give guidance but prevent the slide to turn with the front bezel.
The slide has a curved groove on the full perimeter. It’s a faint curve with flat ends to keep friction low. By turning the front bezel, one set screw protruding this bezel on the inner side, pulls on the slide from the inside of the groove. The slide has no where to go; it can't turn because of the guide rods, it only can give in and follow the cam. And so it does.
03-MB-Sub-X1-VBNext-Size-17 by wk_cpf, on Flickr