TR4/4A Deal or dud? TR4 on eBay

[KVH]

Re: Fan Mounting on "Deal or dud? TR4 on eBay"

And the fan is on backwards! Wonder if he had a heating problem?

I was thinking about this. As long as the fan spins clockwise, and the blade bend is also clockwise (looking from the side), shouldn't the air be sent backwards, in puller fashion, through the radiator and toward the engine--correctly? regardless of how you mount the fan?

I think I'd better learn more about when a fan is backward? What must you look for, because I wouldn't have noticed from this pic. What is the tell tale sign that it's backward? Distance from the radiator?

I'll read your responses and then rush out to check my fan.

 

[TR3driver]

Normally, you are exactly right. The fan moves air the same direction, even if you flip the fan blades front to back, as long as the shaft turns the same way. The analogy I like to use is flipping a nut front to back, it still threads on the same.

But, the blades can be shaped to be more efficient turning one direction. The fan in question has a tapered side (which should be the leading edge) and also is cupped (blades are not flat). The concave side should go in the direction of airflow. So it is mounted backwards. How much difference that really makes, I don't know. Probably just some extra noise and power loss, would be my guess.