I'm not sure whether this belongs here or in the vintage forum, but since it looks like it was originally a ducted fan I'm hoping some of you know something about it.

http://cgi.ebay.com/os-61v-gear-redu...#ht_500wt_1182

This is not my engine, I am not promoting it, I do not know the seller and have no stake in the auction I linked to. I'm wondering if any of you have ever seen one of these before or know what OS was trying to do with it?

As I recall, the .61VF was a ducted fan engine, and I'm guessing the reduction gearbox was a way to turn a bigger prop at a lower speed, but why? It seems to me like it was a really complicated and expensive solution to a simple problem. And I can just imagine the complications it brought, like cooling the gearbox and shearing teeth in the event of a prop strike.

On the other hand, I bet it would sound really cool in a Mustang on a low pass at high RPM screaming through a tuned pipe and a whining gearbox...