REPAIR OF SPRING DRUM COVER
Older model timers(*) are susceptible to the cover on the spring drum suddenly popping off. When this happens, the timer will stop immediately. Normally it will happen either as a result of a hard crash, but it can just happen anytime. Usually it occurs when the spring is partially unwound, such as during the glide phase of the flight. As the spring unwinds, it can "push" against the cover, and if the cover fit has been weakened, it can push it off, and the spring will jump out of the drum. When you look at it, the spring will be a knotted up mess that looks impossible to fix. In reality, you can easily uncurl it.
If it is just a cover that came off, you can fix it yourself. Noting the correct direction of wind and the curl in the spring, take the end of the spring that has a slot in it, and fit this over the shaft post with a little hook on it. You may need to use some needle nose pliers to form this end so it will catch on the hook on the shaft. Holding the spring in place on the shaft, carefully pull the spring away form the shaft, and slip it in the slot in the can. Then, still holding the spring in place, start winding it up. Keep holding or it will pop out. Wind until it is tight. Then it will not come out. Finally snap the cover on the can, and use JB Weld or DP 460 epoxy in four or five places to stick it down good. Just use a toothpick to put little dabs on. I let the adhesive flow over the side to increase surface area of bonding. Be sure you have cleaned the metal with acetone or something so there is no oil or film on them. Let the adhesive harden, and put a couple drops of spring oil, (otters gun oil) and not any crummy 3 in One or WD40 in the little slot in the cover.
* Older models means timers made before about the mid 90s. After that the design of the spring drum was changed to allow the cover to actually be crimped onto the case. This makes it near impossible to remove without damage to the case, but there is no reason why one would need to remove the cover, anyway in normal use.
We sent out a mail notice to all customers who had bought these from us directly (not from a dealer), but sometimes timers change hands and not all may have seen the notice or taken the corrective action (add adhesive) to avoid a problem.