We started our ride, and i gave him some instruction on shifting gears while we were down on level ground near home. We then rode up to this park. there is about 250 feet of elevation rise which is delivered in about a half mile of riding, so by quick math, that's about 250 feet of rise spread over about a 2500 feet run, or about a 10% grade. The early part of this is steeper, and it was here that the real adventure began.
We were climbing up, and i found myself breathing quite hard. The weather was warm, and I felt that stopping was appropriate. I should know better than to stop activity abruptly, and shortly after stopping, I was feeling a bit light-headed. I sat and had M give me my water bottle. I sprayed myself and took a drink, trying to cool off. My breathing was coming under control, but I was still feeling off. Deciding that judgement was the better part of valor, I swallowed my pride and called my wife to come pick us up. She was unsure if she could fit both bikes in the car.
A few moments later, a guy in a pickup stopped and asked if we were OK. I responded, not really, but help was on the way, and sent him away. A few moments later, another cyclist passed, barreling down the hill. He stopped, turned, checked in on us, and departed when we told him we were OK. My wife arrived a couple of minutes later, and I loaded M's bicycle into the back. I was, by then, feeling well enough to ride home.
I began the downhill ride by shifting to a higher gear. It was then that I suffered the blowout. Unlike the more common versions where a tire fails, I had a catastophic failure of a shift cable. I had never learned to reliably install indexed shift cables, so I had to take my "antique" mountain bike into the shop.