On broken derailleur cables that occur while riding
In the last week I came across two instances of broken derailleur cables while on a club ride. Mine was the second one. Here I hope to detail 3 things I learned and where club members can find the videotaped technique to use in general.
I wasn't totally pleased with the zip tie method I used on our ride, though it worked well enough. Thankfully, though, the ride was fairly flat so I was lucky in that respect. When I got home, though, I practiced doing it and discovered a much faster and easier way to handle on-the-road broken derailleur cables. The link showing the technique is detailed at the end of my spiel here.
Using a zip tie to keep the derailleur on the 4th smallest cog which I determined would be the best cog for the expected riding conditions for the bicycle I used (I have an 11 speed cassette), the method suggestions here are probably good for most other bicycles.
I determined that the zip tie method requires flipping the bike upside down in order to gain easier access to the derailleur parts needed. This isn't true for all bicycles but it is for mine. I also determined that having a heavy duty zip tie (about 1/8th inch wide) is better than a thinner zip tie. And finally, having someone to help tighten the derailleur/cable bolt at the critical moment is (for me) absolutely essential if one's goal is to have the derailleur holding on the 3rd cog (or higher) from the smallest due to the pressure of the derailleur spring and the fact that the zip tie easily slips out if it isn't held while tightening the bolt.
Though there are many types of derailleurs the principles of the basic method can be found at the following link (at 6 minutes and 46 seconds which can be obtained by clicking on the appropriate point on the YouTube time line for that video). I think this video would convince anyone to carry at least one zip tie while riding.