Vac motor failed in first 20 minutes?

[tim_mcknight]

I built a vacuum hold down system for my Buddy table. It was working great and 20 minutes later I smelled something hot, you know, like the odor of motor insulation frying, then the vacuum motor slows down over the next minute and finally dies. I built a box similar to this one:

file:///C:/DOCUME%7E1/mcknitl/LOCALS%7E1/Temp/moz-screenshot.jpghttp://www.talkshopbot.com/forum/attachment.php?attachmentid=595&d=1184216114

I allowed about 1/4" clearance around the exhaust side tube thinking this would be plenty of air space to allow the heat to escape. Should there have been more clearance around the exhaust tube opening or did the heat build up too high inside the motor side enclosure and fry the motor? The one pictured above does not show any clearance around it's exhaust tube so I thought it strange this happened. Any ideas would be greatly appreciated.

[erik_f]

I use two of the same motors and used rubber couplings for plumbing to hold the pvc to the exhaust. The rubber couplings have deformed from heat. So these babies run pretty hot when being used the way we use them. They are not really designed to be dead ended...I'm sure they rely on air coming through them for part of their cooling. My motors are not enclosed they are mounted on a simple piece of 3/4 oak ply with a could feet holding it up. I think you have to do everything you can do to maximize air flow out of and around these motors. I don't like the enclosed motor design for these motors.

[erik_f]

This design was based of Ed Langs simple set up.

[ed_lang]

Tim,

Did you have a top on the box so it was enclosed?

If you did, then you did burn it up. The motors have to have a good amount of air flow to allow them to keep cool.

Post a picture of your box and maybe some of us can make suggestions on how to keep it cool.

[tim_mcknight]

Yes, the box is totally enclosed. So I guess I chalk that DUH blond moment up to a lesson well desrved. Oh, I wish I were still blond too ;)

[Brady Watson]

The box shown is designed to be sealed...On the inlet side. The motor cooling fan should be ported to the outside to suck in fresh clean air & the exhaust in that box design was extended with an automotive type galvanized steel exhaust tip.

If the cooling fan is not ported to fresh air, then you'll cook the motor.

Note how the cooling fan is ported:

http://www.talkshopbot.com/forum/attachment.php?attachmentid=596&d=1184216114

-B

[Gary Campbell]

Tim...
2 items to add to what Ed says. On the right end of your box, you need to have an intake, vented outside the box, to allow the cooling air to enter the fan at the "top" or end as pictured. You also need to have port(s) for this cooling air to escape.

Here is how I did this: http://www.talkshopbot.com/forum/showthread.php?t=11813

You dont have to go thru all that I did, but you do need to take care of the basics.

[curtiss]

The good news would be that it did not catch on fire...

There was a shop near here a few years back that burned due to an air compressor locking up and catching the wooden stairway above it on fire in the middle of the night.

Always good to shut those down at the end of the day.

[tim_mcknight]

Ward (from Lighthouse Ent.) called the manufacturer of these motors. They, the OEM, recommends a minimum of 2" air inlet AND a 2" air outlet for the motor cooling fan. I only allowed a 1/4" larger hole around the vac's exhaust for the cooling air to escape. That probably ended up being the demise of the fried motor. I was lucky that this did not catch fire so future builder's of the this system take heed.