Hi All,  For the last three years I have been repairing vacuums out of
my house.  My best friend also has a vacuum repair store.

Some older vacuum models have larger motors with what we call dual fans.
Look for an old Eureka or Sears: they use a powerful Lamb two-stage
motor.  Newer vacuums only have one-stage motors.  Older vacuums have
more suction but the cloth style hoses become porous with time so there
goes your suction.

When you block the hose with your hand the motor speeds up and it draws
less current but it immediately starts to overheat.  Air needs to flow
through the vacuum to keep the motor cool.  Some motors have a cooling
fan on the armature to help the motor stay cool, just in case a clog
forms.

If you want to add on any sort of small tool to the hose, start the
vacuum first then add the tool.  Limit the time on to 45 seconds, then
remove the tool.  Let the vacuum run a bit with the tool off to cool the
motor.  Then shut the vacuum off.

Shop vacs are able to lift water because they spin at a higher rate than
normal vacuums.  Any messing with the flow of air through these vacuums
and you will be looking for a new one.  Shop vacs have the shortest
life span of any vacuum because they are more likely to be used to pick
up fine dust.  Fine dust like fireplace soot, drywall dust or flour
clogs the pores of the vacuum bag causing the vac to overheat.

John Conrad Kleinbauer