# Box fan saga 2.0



## NCjeeper (Jun 12, 2017)

So a little back story. I got this "free" box fan from a buddy that was closing his welding shop. He said it worked but would shut off then come back on. So I had it on the bottom of my to do list "fix fan". Well recently I received a catalog from Surplus Center. In it was a large selection of motors. I thought now would be a good time to fix the fan. So I go out and check the tag on the fan motor to see what I have and need to order. Well the tag says 230 volts. The fan has a 110 plug on it. No wonder it did not want to run. So I ordered a 110 motor.
Well it arrives and the body of it is larger than the one I am replacing and also the external cap hump is in a different place. So the mounting system wont work with my new motor. No problem I will just fab something up.



So I machine a face plate for the new motor to mount against and a bottom support. Get everything welded up and painted. Install new motor and fan blade and it works great. Well only for like 5 minutes and it shuts off. I feel the motor and its extremely hot. Hmm what gives? I remove the motor once it cools and double check my wiring. I then plug it in and let it run on the bench. It runs for 15 minutes just fine and the motor is bearly over room temp. So after some contemplating I think the fan blade is too much for the motor shaft and is stressing it to the point that the temp raises and then the thermo protector kicks it off.
So Lets try this again. So I figured mount the fan on a shaft driven by a pulley and belt set up. That way the stress on the shaft motor is reduced and should spin fine. So I grabbed a chunk of mystery steel and made a collar sleeve. Pressed in bearings at both ends and pressed a shaft through. Before I pressed in the shaft
 I milled screw flats on both ends. So here is where I am at now.



I need to fab an adjustable mount for either the motor or sleeve. I haven't decided yet.
So this "free" has cost me over 100 bucks so far. Not to mention all the time I have in it.


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## brino (Jun 12, 2017)

Yep, I occasionally get "free" stuff like that too. It can be tough to know how much effort and cost to put into it.

-brino


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## kd4gij (Jun 12, 2017)

I would of went with 220 for a fan that size.


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## silence dogood (Jun 12, 2017)

On the old motor did you check the motor speed, it might not have been 1750rpm but half that.  Oh well, I've had some pretty expensive "free" stuff myself.


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## ELHEAD (Jun 13, 2017)

Now who in his right mind would want to spend $200 on a new fan when he can work 30 hrs. and spend  $100 on a free fan?
Dave


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## NCjeeper (Jun 13, 2017)

ELHEAD said:


> Now who in his right mind would want to spend $200 on a new fan when he can work 30 hrs. and spend  $100 on a free fan?
> Dave


Me me pick me.


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## Forty Niner (Jun 13, 2017)

After getting it set up with the belt drive, measure the amperage draw on that motor (while running the fan of course) and compare to the nameplate.   If amperage draw higher, then the motor is too small.  To use it anyway, change the pulleys to slow down the fan.  Use a bigger pulley on the fan and/or a smaller one on the motor.


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## jim18655 (Jun 13, 2017)

ELHEAD said:


> Now who in his right mind would want to spend $200 on a new fan when he can work 30 hrs. and spend  $100 on a free fan?
> Dave


There's a recent thread about the definition of 'hobbyist' and this would fit.


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## Silverbullet (Jun 14, 2017)

That's a real fan , by the thickness of the blades and mounts it should last forever. Most like that have at least a ten " pulley on fan and 2" or 3" on motor. I don't doubt the motor overheated with weight and size when direct mounting.


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## NCjeeper (Jun 14, 2017)

Silverbullet said:


> That's a real fan , by the thickness of the blades and mounts it should last forever. Most like that have at least a ten " pulley on fan and 2" or 3" on motor. I don't doubt the motor overheated with weight and size when direct mounting.


I have a 6" fan pulley and a 3" motor pulley to try this time.


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## Dave Paine (Jun 14, 2017)

I have a house fan mounted on the end of the house in the attic.  I think 36in fan.  Installed by previous owner when the house was built.  A 1/2HP motor, 120V and about 1750 rpm.  The fan pulley may be 9 - 10in.  The motor pulley is perhaps 3in.  Too hot to go up in the attic to check.

I run the fan when the temperatures get around 90+ deg F.  Helps the central air to keep the house cool since the indoor unit and flex ducts are in the attic.  A retrofit many years ago.


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