Gentlemen,

I need a bit of vaccum for a one-off experiment so it's not worth
ordering a bespoke vaccum pump for. I have an upright vaccum cleaner
that puts out (according to the back panel) 1800W at 220V and 2000W at
240V. I get just the perfect amount of mild suction I need when I hook
it up to a variac and set it to 80V. I will need to leave this running
for about 40 minutes at this lower power. I don't think there's any
danger to the cleaner in doing this but thought it sensible to run the
idea past the Panel just in case I've overlooked anything.

Thanks.

On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Oh - I forgot to mention that the airflow through the system will be
almost totally blocked, so the same effect as sticking your thumb over
the end of the hose as it were.

If you are running it stalled (air stalled that is) then no cooling air
will be passing through the motor.

Cursitor Doom wrote:

I get just the perfect amount of mild suction I need when I hook
it up to a variac and set it to 80V. I will need to leave this running
for about 40 minutes at this lower power.

motor might overheat with low airflow, or stall?

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

--
When plunder becomes a way of life for a group of men in a society, over
the course of time they create for themselves a legal system that
authorizes it and a moral code that glorifies it.

Frédéric Bastiat

On 19/06/2020 17:13, The Natural Philosopher wrote:
On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?


The stuff between your ears.

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum for a one-off experiment so it's not worth
ordering a bespoke vaccum pump for. I have an upright vaccum cleaner
that puts out (according to the back panel) 1800W at 220V and 2000W at
240V. I get just the perfect amount of mild suction I need when I hook
it up to a variac and set it to 80V. I will need to leave this running
for about 40 minutes at this lower power. I don't think there's any
danger to the cleaner in doing this but thought it sensible to run the
idea past the Panel just in case I've overlooked anything.


If that 80V is with the airflow restricted, I make that about 220W. Say
200W as pure heat.

12v fan from a PC power supply would see most of that off.

What temperature would a x Kg lump of motor steel get to above
ambient,over 40 minutes, if 220 Joules per second of energy is passed
in, and would it burn off the insulation or other scary stuff?

I can't do school physics anymore ...

--
Adrian C

On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!

On Fri, 19 Jun 2020 17:54:49 +0100, Adrian Caspersz
wrote:

If that 80V is with the airflow restricted, I make that about 220W. Say
200W as pure heat.

12v fan from a PC power supply would see most of that off.

What temperature would a x Kg lump of motor steel get to above
ambient,over 40 minutes, if 220 Joules per second of energy is passed
in, and would it burn off the insulation or other scary stuff?

I can't do school physics anymore ...

A valiant attempt, Adrian. OK, so let's say I up the voltage to
(plucking a figure out of my arse here) 125V and 'bleed' a certain
amount of air through the system, whilst monitoring the motor case
temp with a thermistor?

On 19/06/2020 18:15, Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:54:49 +0100, Adrian Caspersz
wrote:

If that 80V is with the airflow restricted, I make that about 220W. Say
200W as pure heat.

12v fan from a PC power supply would see most of that off.

What temperature would a x Kg lump of motor steel get to above
ambient,over 40 minutes, if 220 Joules per second of energy is passed
in, and would it burn off the insulation or other scary stuff?

I can't do school physics anymore ...

A valiant attempt, Adrian. OK, so let's say I up the voltage to
(plucking a figure out of my arse here) 125V and 'bleed' a certain
amount of air through the system, whilst monitoring the motor case
temp with a thermistor?

Nah, I'm not really in the "Tune the system for minimum smoke" game.

I do my DIY by the habit of real overkill. No real calculations, but
just loads of planks of wood deployed where just one would admirably
support a floating seed from a dandelion .

Bodging with conscience ...

--
Adrian C

Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


I think our legend of typographical excellence was referring to €œvaccum€� as
opposed to €œvacuum€�. Pot, kettle, black situation. ;-)

Tim

--
Please don't feed the trolls

Cursitor Doom explained :
A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!

No, there's loads of it up there /!\

Cursitor Doom explained :
On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Oh - I forgot to mention that the airflow through the system will be
almost totally blocked, so the same effect as sticking your thumb over
the end of the hose as it were.

Almost no airflow = rapid over heating of the motor.

You need a separate motor with vacuum pump, even then it will need some
extra cooling airflow - not dependent on the motor speed.

On 19/06/2020 16:15, Cursitor Doom wrote:
On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Oh - I forgot to mention that the airflow through the system will be
almost totally blocked, so the same effect as sticking your thumb over
the end of the hose as it were.


A sebo cylinder vac has variable speed. So does my elderly
Morphy Richards Bulldog vac (like a Henry).

On 19/06/2020 17:32, Andy Bennet wrote:
On 19/06/2020 17:13, The Natural Philosopher wrote:
On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?


The stuff between your ears.
Whoosh....


--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 19/06/2020 18:12, Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


but what is a 'vaccum'

It's not in the dictionary


--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 19/06/2020 18:37, Tim+ wrote:
Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


I think our legend of typographical excellence was referring to €œvaccum€� as
opposed to €œvacuum€�. Pot, kettle, black situation. ;-)

Tim

The staggering thing is you and I are the only people who noticed...


--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 19/06/2020 18:59:38, Harry Bloomfield wrote:
Cursitor Doom explained :
On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Oh - I forgot to mention that the airflow through the system will be
almost totally blocked, so the same effect as sticking your thumb over
the end of the hose as it were.

Almost no airflow = rapid over heating of the motor.

You need a separate motor with vacuum pump, even then it will need some
extra cooling airflow - not dependent on the motor speed.

I'd wager air flow is proportional to voltage but power loss is a square
function.

Half voltage = half flow = 1/4 power loss.

I would be surprised if the exhaust air was hotter at reduced voltage.

BICBW

On Fri, 19 Jun 2020 18:31:34 +0100, Adrian Caspersz
wrote:

I do my DIY by the habit of real overkill. No real calculations, but
just loads of planks of wood deployed where just one would admirably
support a floating seed from a dandelion .

Bodging with conscience ...

OK, well having given it further thought, I only need a fairly small
amount of suction, so I may as well run the cleaner at full power
voltage with no air blockage and just cream-off a small amount of the
airflow via a fabricated 'tee' piece inserted into the hose. Can't go
wrong!

On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Gentlemen,

I need a bit of vaccum for a one-off experiment so it's not worth
ordering a bespoke vaccum pump for.


Go hunt up a discarded fridge or freezer compressor - make ideal
vacuum pumps.

I have an upright vaccum cleaner
that puts out (according to the back panel) 1800W at 220V and 2000W at
240V. I get just the perfect amount of mild suction I need when I hook
it up to a variac and set it to 80V. I will need to leave this running
for about 40 minutes at this lower power. I don't think there's any
danger to the cleaner in doing this but thought it sensible to run the
idea past the Panel just in case I've overlooked anything.

Vacuum cleaner motors rely totally upon a huge airflow over the motor
for cooling. Without this they rapidly overheat.

The Natural Philosopher Wrote in message:
On 19/06/2020 18:12, Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


but what is a 'vaccum'

It's not in the dictionary


--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14



Single c, double u. "vacwm".
--

%Profound_observation%

Why not use the vacuum as is and bleed air in through a branch pipe to reduce the effective suction? Henry vacuum cleaners have a port on the handset to regulate the pull on the carpet.
(Most folks tape them closed)

Well more likely to have issues with the variac than anything else, I'd
suspect, however do remember that the airflow inside the cleanner cools the
motor.
If it overheated, then there is usually a thermal cut out in any case.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Cursitor Doom" wrote in message
...
Gentlemen,

I need a bit of vaccum for a one-off experiment so it's not worth
ordering a bespoke vaccum pump for. I have an upright vaccum cleaner
that puts out (according to the back panel) 1800W at 220V and 2000W at
240V. I get just the perfect amount of mild suction I need when I hook
it up to a variac and set it to 80V. I will need to leave this running
for about 40 minutes at this lower power. I don't think there's any
danger to the cleaner in doing this but thought it sensible to run the
idea past the Panel just in case I've overlooked anything.

Thanks.

That will almost certainly trip the thermal overload, probably in about 10
minutes or less. I have a Basch and what that seems to do if there is a
blockage is throttle the motor right back and stay that way till it is cool
enough.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Cursitor Doom" wrote in message
...
On Fri, 19 Jun 2020 15:21:59 +0100, Cursitor Doom
wrote:

Oh - I forgot to mention that the airflow through the system will be
almost totally blocked, so the same effect as sticking your thumb over
the end of the hose as it were.

Yes he would be better of fitting a tube with two inlets, so the air coming
in through one tube will be at the pressure desired then he can do away with
the variac.
Brian

--
----- --
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The Sofa of Brian Gaff...

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Note this Signature is meaningless.!
"John" wrote in message
2...


If you are running it stalled (air stalled that is) then no cooling air
will be passing through the motor.

Before we get bogged down in who invented the vacuum, let me say just this.
When we used to use thermionic valves. Tubes to our American readers,
getting the pure vacuum was eventually done by burning the last part of the
oxygen and effectively locking it up in the resulting solid which coated
the inside of the glass, a silvery black colour in a vacuum. Even in the ISS
when they depressurise the air lock saving the air as much as possible they
cannot get it to a vacuum, since its got nothing to suck against if the bits
that are left are not near the pump intake. Suction in a vacuum is not much
use!

Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Tim+" wrote in message
...
Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


I think our legend of typographical excellence was referring to "vaccum"
as
opposed to "vacuum". Pot, kettle, black situation. ;-)

Tim

--
Please don't feed the trolls

On Sat, 20 Jun 2020 04:32:05 +0100 (GMT+01:00), Graham. wrote:

The Natural Philosopher Wrote in message:
On 19/06/2020 18:12, Cursitor Doom wrote:
On Fri, 19 Jun 2020 17:13:30 +0100, The Natural Philosopher
wrote:

On 19/06/2020 15:21, Cursitor Doom wrote:
Gentlemen,

I need a bit of vaccum

wots that then?

A *partial vaccum* if you prefer. It's a seriously big deal to
generate a pure vaccum!


but what is a 'vaccum'

It's not in the dictionary

--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14


Single c, double u. "vacwm".

That's Welsh, shirley.
--
Peter.
The gods will stay away
whilst religions hold sway

On Sat, 20 Jun 2020 08:32:33 +0100, "Brian Gaff \(Sofa\)"
wrote:

Well more likely to have issues with the variac than anything else, I'd
suspect, however do remember that the airflow inside the cleanner cools the
motor.

The (3A) fuse in the variac did blow first time I tried the idea. I
hadn't done any sums and hadn't twigged that 1800W would overload it!
However, replacing it with a slow-blow type of the same rating enabled
me to run it at 80V for an hour no problem. I just had to wind 'er up
to 220V at the beginning to overcome the motor's inertia, then
quickly backed off to 80V once it was running.