Electric motor advice/sourcing help needed.

[Sam Cogley]

Originally Posted by 69427

I like that! Thanks.

No problem. It's a good way to upgrade band saws, drill presses, and other power tools to PWM-controlled DC power as well. Those things are rated to have humans running pushing against the bearings, they'll drill through things just fine. They usually have a speed controller board buried somewhere inside, usually near the motor. The units with push-button controls are harder to adapt, and there are a few old treadmills out there with AC motors and mechanical speed-change mechanisms.

[phantomjock]

Originally Posted by 69427

I agree, but it just seems to me that a turning mechanical fan is going to block less air than a non-turning electric fan. (I can't easily prove it at the moment though.)

As I understand 12 fans - unless you lock it mechanically/electrically - it will free wheel (spin) without being "on". Minor - nearly immeasurable drag there I'd think.



Cheers - Jim (aka - Jimmy)

[69427]

Originally Posted by phantomjock

As I understand 12 fans - unless you lock it mechanically/electrically - it will free wheel (spin) without being "on". Minor - nearly immeasurable drag there I'd think.



Cheers - Jim (aka - Jimmy)

I hand spun one of my spare electric fans (for my street rod), and there's noticeable magnetic drag on it. I was somewhat curious if there was some way to get some "free" recharge energy out of it while cruising down the road, but between the magnetic drag and the inefficient pitch when used as a "turbine", instead of a prop, I'm not convinced that these things freewheel that well.

[Sam Cogley]

I haven't felt much in the way of drag on my Mk. VIII fans when they're freewheeling.

[69427]

Pulled a motor out of a junked treadmill the other day. Two and a half horse DC motor. Hooked it up, and damn, the thing works.

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I still need to figure out the belt drive setup yet. The treadmill had a flat multi-groove belt on it, while I'd like to just be able to use a Vee belt and some of the spare pulleys I have laying around to get the fan speed I want.

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Looks like a threaded 7/16 shaft that the flywheel/pulley assembly is threaded onto. I'm trying to decide what's the easiest/cheapest way to put a regular vee pulley on it. I got a few ideas, but I just gotta take a closer look at some available pulleys to see what makes the most sense.

I've got the circuit board that controlled the motor speed (the control panel was digital, but I don't know yet if the signal to the motor board was analog or digital), and now I just gotta decide how much of it I want to use, and how much I want to bypass. I also need to decide the best/cheapest/decent-accuracy way to measure the fan RPM and the motor power consumption.

[Sam Cogley]

I'd just plug in the motor control board and find a place to mount the speed control pot. That way you have PWM-controlled motor capable of anything from 0 rpm to the maximum rated rpm.