Update on burning smell ....

John Shott shott at stanford.edu
Mon Mar 31 20:11:12 PDT 2008


Fans of thermcopoly2:

As you recall, several days ago we experienced a smell near 
thermcopoly2.  At that time, because I could smell it at the intake of 
"Blower 1", I shutdown power to blower 1 and the smell dissipated over a 
period of a couple of hours.

This afternoon, I disassembled blower 1 and have a somewhat better 
understanding of what went wrong.
Basically, there is nothing in the box but a squirrel cage fan.  I found 
2 things wrong when I opened the box: it is supposed to be supported by 
4 things that I'll call vibration dampers (until I can find exactly what 
it is in the Grainger catalog).  This is a 1/2 diameter, 1/2 inch long 
length of rubber that has a threaded section attached to each end with 
probably either 10-24 or 12-24 threads, I think.  In any event, all 4 of 
these have sheared off either due to age or excessive vibration.  
Moreover, when they sheared off, it allowed one of the electrical 
contacts (albeit the neutral) to come in contact with the frame and 
there is clear signs of arcing.  This may have been some or all of the 
smell.  I also noticed that the squirrel case is hard to spin ... 
certainly any other squirrel cage fan has been easy to spin when no 
power is applied.  This leads me to believe that at some point the 
bearings got toasted.

Tomorrow, I will see if I can extract the motor from the housing .... 
I'm hopeful that I can find a replacement motor because the body of the 
squirrel case has a somewhat customized flexible-rubber input adapter 
that looks like it might be a bit tricky to remount to a new squirrel 
cage housing.

In any event, when I order replacement vibration dampers, I'll likely 
try to order a total of 16 so that we would have them on hand and could, 
at our leisure, replace them in the other 3 blower units when the 
occasion allowed.

That's what I know about this at the moment but am confident that we can 
resolve the smell problem if we can find replacement vibration dampers 
to properly mount the squirrel cage and can also find a replacement 
motor without bearing problems.

Thanks,

John







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