[AT] Old shop lathe motor-- motor questions for you "experts"

[Greg Hass]

List traffic is a little slow, so I thought I'd put out a few comments on 
this subject.  What I am going to say is based on both experience and 
things I have read.

In the past I had both beef cattle and hogs.  My feeding setup for cattle 
required 10 motors ranging from 1/4-hp to a couple of 5-hp on the silo 
unloaders.  My grinding setup for hogs used 9 different motors ranging from 
1/4-hp to 5-hp in various sizes.  I believe it is true that the old big 
motors were that way because they were American-built and were true 
horsepower/horsepower.  On one auger conveyor I installed a 1-hp motor that 
my dad had purchased for a different use some 50 years ago.  Unfortunately, 
about 15 years ago the shaft spun in the ball bearing race and ruined the 
motor shaft beyond repair.  I replaced it with a 1-hp Dayton 
motor.  However, if the conveyor became heavily loaded it would stop, 
whereas the old motor had carried it through.  After enough aggravation I 
started studying the problem and found on the nameplate two 
letters.......S.F.    I found that that means "service factor", or the 
percentage of the motor's rated horsepower that it could put out 
continuously without overheating.  I found the new motor had a service 
factor of 1.0, and the old motor (which I still had lying around) had a 
service factor of 1.35, which meant the old motor had a lot of reserve 
power that the old one didn't.  I talked to a local dairy equipment dealer 
who said he had run into the same problem on milking machine pumps.  He 
would replace a bad motor with one of equivalent hp, only to have it keep 
overheating and stopping.  Then he'd have to go back a week later and 
replace it with the next bigger hp.  I then had to buy a 1-1/2 hp motor for 
the conveyor and it ran almost as well as the old 1-hp.

As a side job, I also repair appliances and found about 10 years ago that 
the newer motors would start smoking right away when overloaded, whereas 30 
years ago when I first started in the business they would hum but not 
smoke.  I could not figure out the difference until a neighbor (who takes 
motors apart to sell for scrap) showed me the difference.  It turns out 95% 
of the appliance motors in the last 15 years have aluminum windings, not 
copper, and cannot tolerate being run hot.  We have three of those Baldor 
motors that someone was commenting on - two 5-hp on silo unloaders, and a 
2-hp on a gutter cleaner.   Although we no longer use them, they are still 
good and after years of use were never repaired.  They could be slowed down 
to where they were barely moving but they would never stop, and would 
always slide the belt but not trip the circuit breaker.  It maybe true that 
they are no longer available, but a few years ago when they still were made 
an electrical contractor told me that a new 5-hp was around $2000.

I was in Tractor Supply the other day and noticed that Ingersoll Rand 
compressors are now listing 2-hp on the tank.  For example, it will say 
"running 5-hp, peak 11.5-hp."  HINT: If the nameplate on a motor does not 
list the HP, or after HP says "spl" (meaning special duty),  you can be 
assured the actual motor hp is nowhere near the hp listed on the tank of 
the compressor.

Just a few random thoughts for the evening.

Greg Hass
Bad Axe
from Michigan's snowy and getting snowier Thumb