Measuring the vacuum at the hose nozzle on the kitchen floor may require
something a bit more sophisticated than just taking a reading at the nozzle,
since there needs to be a significant flow, but partial blockage, for the
vacuum to lift any dirt. (the gap of the nozzle at the floor relates to how
effectively the appliance pulls in dirt). With the nozzle elevated to 3"
above a floor/hard surface, would create a dramatic difference in
efficiency.

Something similar to a leakdown tester comparison may be helpful, indicating
readings of the actual vacuum at the appliance inlet, and simultaneous
reading at the nozzle on the floor with some percentage of restriction to
flow.

Partial blockage of the flow generally results in the turbine motor speeding
up (powered with a brushed universal motor), so that's another factor, I
'spose.

Vacuuming dirt from a horizontal screen surface would be a horse of a
different flavor.

--
WB
..........


"Ed Huntress" wrote in message
...

The vacuum-forming rigs I've seen have to pull full vauum within
seconds, or the plastic would be too far from the heating element for
the thing to work. So I have some trouble relating to your example.

However, it looks like we're all saying much the same thing in
different ways. The effect of hose length on any vacuum system depends
on how much air you're pulling through it. If the flow rate is very
low -- for example, if you're just dealing with the slow leak in a
good vacuum-cure composite bag -- then hose length matters little. If
you're trying to vacuum the dirt off of your kitchen floor, which
requires a very high flow rate, the longer hose presents more friction
to the air flow and reduces the vacuum reading you would get, if you
measured it, at the terminal end of the hose.

--
Ed Huntress