The left side crank bolt on my bicycle keeps coming off. When that comes off, my crank and pedal comes off; a real disappointment when I'm miles from home. So, I had it tig welded in place. The bolt no longer came off but the crank still began to wiggle some and squeak a lot. So, I had the tig spots ground off so I could replace and tighten the bolt again. The bolt has continued to come loose and fall off. Yesterday, I tried using some plumbing tape to secure the bolt; it came off again.
I'm at a total loss as to how to fix my problem. I'm willing to spend money but I'm stationed in Afghanistan; there are no bicycle shops here. I can buy parts online but I'm not smart on bicycle maintenance either. I'm not sure what I need to buy, if anything. I have access to tools so I could probably replace my crank, bottom bracket, and front chain ring assembly if needed.
Any suggestions on things I should try? If parts are recommended, what do I need to measure on my current bike to ensure I get the right replacement parts?
Bagram Air Field