mech fan blade rpm limit?

For a short time I had an aluminum, name-brand , flex-fan. I put it on one spring to see if my 292/508 cammed engine would be any more powerful. Disaster! I made the mistake of bolting it on and heading out to a show, about an hour away. Everything was fine until I slowed down below 30mph.
It wasn't a total write-off day, cuz I had the earlier fan still in the trunk. A short while later,we were on our way again.Lesson learned.
Anybody need a fan?Nearly new,very low mileage, a little dusty; just pay shipping and handling.