Here you go Dennis,
Not exactly discussing your specific case but talks about the o-ring anyway.
Re: How Many Can Twist their (RA) Twisty one Handed?
Abarth_1200,
The Twisty was never intended to allow single-handed operation. Although the human hand is very dexterous, holding on to the light with the pinky, ring and middle fingers curled around the battery compartment while rotating the head with the thumb and index finger cannot easily generate a lot of torque.
There are two cases to consider. The first case is immediately following any operation of the light - i.e., twisting to change levels. In this case, the O-ring is well lubricated and there is relatively low stiction. This case requires the lowest torque to rotate the parts.
The second case is after you have allowed the light to sit for an extended period of say 12 hours or longer. The grease is squeezed out from under the O-ring and thus there is very little lubrication under the O-ring. The stiction is very high - many times higher than in the first case. Once the parts have been exercised, the O-ring becomes well lubricated again and you return to the first case.
Given the above, what can be done to reduce the torque? There are several things. O-rings, like everything else, have tolerances. Swapping O-rings may help. Or going to one or two sizes smaller ID will stretch the O-ring slightly, making it smaller in diameter. The normal size is 1.5 by 20.5mm. A 5% stretch is acceptable. So going down to a 1.5 by 19.5 is allowable.
We cannot recommend removing the O-ring because it removes the water seal. However, if you do remove the O-ring and use plenty of grease on the threads, the grease will seal the threads and make the light rain resistant. And you may find the light works nicely with one hand.
We have also tested Krytox. In testing it reduced the stiction with the O-ring dramatically - especially after the 12 hour no movement test. But at $20/oz, it is a bit on the expensive side.
Henry.