Originally Posted by
squirtdad
Big Big is simple: Size your chain so that you can run Big Big, even though you never plan too. Otherwise, if you shift into that combo (even if you don't ever plan to, Murphy's law applies) combo, crash is likely (chain and pedal just stop moving, in my case wheel stopped also) how much it hurts is the speed you are going
I think the best solution to OP's need is simple, is the most classic, is a virtual bike law and has not been mentioned yet N+1...... add a bike for hauling the dog trailer around.
FWIW over time I have moved to small small chain sizing but don't think it will fork for OP unless he goes to derailer that can handle the entire range.
https://www.youtube.com/watch?v=QuhHn7HaZcQ
The last time I left my bike in a bicycle shop to have some work done on it was a number of years ago. Due to events after that I now do all of the mechanical work on my bikes.
What happened was the mechanic put too short a chain on the bicycle and never informed me of that. I was getting ready to cross a busy highway and shifted into a lower gear forgetting that I was in the big chainring. It turned out that the lower gear was the largest rear sprocket. When i went to pedal the entire drivetrain locked up and I tipped over to the right. Fortunately there were no cars or transport trucks coming at the time. Accidently shifting into a big big combo can have nasty consequences.
Also, if a chain is too slack in the small small combo, I think there's a risk of pulling the derailleur around and up into the sprockets which will also lead to unpleasant things happening.
When I run a triple crankset I use a proper triple capacity rear derailleur.
Cheers