What Sjouke said is probably true but I believe there is Zener diode protection all over the place. If so, would it be a good idea to unplug the motor for this ? Maybe not. Let the Zeners conduct for a half a minute, should do no harm. On the other hand, disconneecting it might allow a highr voltage to be developed which could cause a breakdown of insulation in the wiring.

the other concern is the bearings. They are not quite Timkens. they are probably just brass wjhich means there is a functional limit to RPMs. It's a chemical metalurgical thing and I would have to ask my Father. Well, to do that we need to get some Gypsies and have a seance. (Timken bearing are the type used on non- drive car wheel's shafts. They are tapered and tightenable down to zero play and thrust, they are also used on better lathes and other machines)

Anyway, the regular brass bearings almost cannot be called bearings, they are more apty called busings and they wear with every revolution. What's more, the even minor friction in that system exacerbates the wear at at least an exponential rate because of the heat produced. you won;t be aware of it because it is localized right there. what can happen is that the life of the fan is greatly shortened. not that it will fail. but it will become noisy..

I never worried too much about noise until the fan in my laptop got noisy. you know the microphone picks that up ? I do now.

I would say if you can use two hands, use one for the air chuck and the other to limit the speed of the fan.

I was going to mention the 327 the olman built a long time ago that always wiped number one bearing at exactly 9,200 RPM. But that is a differenrt problem, they couldn't get enough oil to it. they did almost everytihng, graduated bearing clearances, high volume, cut the flow to the lifters and cam, and still it wiped out at about the same RPM every time. the problem was the mass of the oil trying to make it through the crank with the centrifugal forces acton on it. The ONLY way they could have reallt fixed it was to use two oil pumps, or a dual feed system. That was too much work.

So they got the crank machined a few thousandths under and had it hard chromed back to size. this way, the crank ws safe and all they had to do was to replace the bearings, and in some cases the connecting rod. And no, that did not unbalance the engine in any signifacant way.

But back to the topic, I THINK the major danger is to the bearings. You're an experimenter, experiment. (and of course post up the results)

Find a way to measure the RPMs when you blow that air through there.

Oh **** finding a way, you already know. It has a tach pulse. Just get the rated RPMs for a given fan, find what it is putting out, it is most likely one pulse per revolution. dunno, never had to check. But then blow that air and see what you get on the freak counter.

Hell maybe I'll do that just for fun. Just to learn something that day.

You know what you do shooting that air in ther ? YOu make a turbine engine. It is not quite as good as the stor boughten ones, but that is what it is.

Thanks for raising a new, interesting point that nobody ever thought of.