Long storey... I was butchering one to go into one of those powered Peltier cool boxes. The original fan motors are bush ones with thin sprung metel brushes, which give a few month's continous use only. OK for taking on holday a couple of weeks a year, but useless for continuous use.
I took a good quality Papst fan, snapped off all of the frame, leaving just the impeller mounted on the flat motor base, which was fixed to where the original motor went. Trouble was it turned the wrong way. The original fan was more centrifugal than axial, and by reversing the direction of the new fan, and having removed the frame, it too works well as a centrifugal fan (probably better than it did as an axial fan). It's done about 12 years continuous service, mostly as a small fridge for keeping the team's milk fresh in a number of offices I've worked in. It still works, but isn't in use now.