Thanks KenB and Chris M. for you suggestions about the Arc flashlight!
Ken suggested using gold plated terminals for the battery and S-rank LEDs from Nichia.
Chris said his Arc prototype did not flicker if it was screwed down tight. He said that maybe some oil made it onto the contacts.
I will try to respond to these suggestions and ideas to the best of my ability:
We originally asked our PCB manufacturer to use gold on the battery side of the PCB. They said that it would be expensive and we would not be happy with the wear results because gold is soft (just look at how the gold-plate wears off of cheap jewelry).
You'll notice that pretty much all lights do *not* use gold where there is a friction surface. Just because everyone is doing it doesn't make it right, but there probably is a good reason behind this particular example.
We decided to use an alloy of tin and silver for the contact. It's stronger, fairly conductive, minimally reactive with other metals and most importantly, thick (so it will wear well). This is similar material to what you'll find at the base of most flashlight bulbs.
If oil gets on the contact, you can simply wipe it off. Our early prototypes used a high friction O-ring, so copious amounts of oil was used. I doubt the oil was the problem though.
About S-rank Nichias:
As you know, they are about 35 percent extra in cost and they take over a month to get in.
I think they would make an excellent part of a future model. However, I really cannot comment on future designs.
One really good suggestion we have been getting emailed to us so far is requests for some sort of clip. Because of the volume of requests, we have decided to move the time table up for that accessory.
Thanks for the input!
Peter Gransee
President, Arc Flashlight, LLC.