Another failed part I ran into with my Bolens 1250 restore was the hydro cooling fan (1719006). This fan had failed in several places and had been welded poorly by the PO. The fan was a formed sheet metal part about 3/16” thick. I believe it was initially designed as a press fit on the 1.5” diameter u-joint yoke. In trying to find a replacement, I came up empty. So I built a replacement assembly using an thin appliance fan and a split shaft collar.
First, the fan center was machined out to match the 1.5” yoke. Then I drilled five holes for 10-32 allen head machine screws in the fan and the split collar. The assembly is shown in the attached pictures.
My major concern is the amount of vibration that the u-joint will impart to the thin fan. There would be two theories on that:
1. One would be to make it out of heavy material like the original fan. Obviously, there are a lot of failures of this design. The fan may have been so rigid that the vibrations and rotation speed just caused it to fatigue to death. This is the theory the Bolens engineer used, probably because he needed enough material to press fit the fan on the u-joint.
2. Two would be to make the fan thin enough to flex with the vibrations of the shaft. This is the “airplane wing” theory -- the part is designed to flex so it won't fail. This is the route I went, mostly because I could find the parts.
Time will tell if this works. At least for a time the hydro will be cooler than before.