How to measure suction ?

[CraftNav]

Today I got given not one but two working vacuum cleaners for free

Already having two other workshop vacs I wanted to know which ones 'sucked' the best if you get my meaning :lol:

I have a plug in power meter but this only measures the current used not the suction, so after a quick cuppa I came up with the following....

Its basically a small 12v DC fan out of a computer (you can get them in Maplin) superglued to the end part of a vacuum attachment

The output of the motor is connected to a cheapy volt meter set to read millivolts.

Now I don't know what the unit of measurement is for suction but all I wanted to do was compare vacuum's.

I found out some interesting results...

My Hoover Aquamaster with a brand new fabric filter and bag gave a reading of 70, without the bag I got a result of 77 (thats 10% reduction in suction even when using a brand new bag !)

My Henry (getting on a bit now) gave reading of 54
so I stripped it completely and cleaned all the internal bits of filter, blasted it out with compressed air, cleaned the com with an eraser, and oiled the bearing, fitted a new dust bag and the resulting reading was 62

I also notice that if the hose is out straight (as opposed to in a coil) the reading increases by about 3.

I tried doubling the length of the hose this only reduced a reading by 1 (not as much as I would have thought)

Anyway this has got my little brain thinking now that I have two spare vacuum motors (one that gave a reading of 104)

has anyone on the forum ever built there own twin motor shop vac!

Any comments or refinements greatly appreciated

John (AKA johnny 4 Vacs)

 

[Dave S]

I used to have a magazine article in which they built a twin unit vac. Not sure if I still have it, but I'll have a look.

Dave

 

[Pecker]

See thats the problem with you Caulkheads on "The Island", nothing better to do :lol: :lol:

don't tell the wife.. she'll be wanting every last crumb sucked up now!

woody

 

[CraftNav]

Dave, thanks for the post - it rang a bell ! and at 3.30AM I woke up and thought 'I knew I'd seen that before' so down the garden to the workshop (security light coming on) :roll:
A quick rumage through past copies of Good Woodworking and hey presto ! FYI Feb 1999 issue 79

Woody - call me a 'caulkhead' :evil: "how very dare you !!!!!" :lol:

I'm not but SHMBO is . I'm from Manchester (if that any better) :wink:

john

 

[Anonymous]

Are you not measuring flow (in centre of the pipe) rather than suction?

 

[Pecker]

:

I'm not but SHMBO is . I'm from Manchester (if that any better) :wink:

john

No, it's worse :twisted:

(Honary caulkhead me, Mother comes from island, both brothers born there, parents retired back there....)

Woody

 

[9fingers]

Hi Sawdust Johnny,

You should find all you want to know about suction measurement (and arguably more than you ever wanted to know!!)
on Bill Pentz's website here.
http://www.billpentz.com/

Look under cyclones/Tests & Faqs/measurement


best wishes from the mainland nearby!

Bob

 

[CraftNav]

Hi Bob

Thanks for the tip. but your too late :roll: I'm already on the infamous " I have nothing to stress me out in life so I think I'll build a cyclone !"

For the last two weeks I have read most of Bills site (& I mean most of it) I have join the Australian Ubuet BB and read loads on there, and I have been through most of yours and the late Barry Burgess posts.

So far I have started on a small 6" mini cyclone, I have the body made and am now about to start tackling the funnel :?

I will be taking lots of pics so will keep you posted

john

 

[Dave S]

A quick rumage through past copies of Good Woodworking and hey presto ! FYI Feb 1999 issue 79
john

Was it really? I had a look but don't have the article. Funny - I was convinced in my own mind that it was one of the router magazines.

Feb 1999 - that would have been one of the first woodworking magazines I ever bought - the first being the Jan 1999 issue of F&C.

Dave

 

[Anonymous]

John

To get any meaningful readings about airflow (not suction), you need to take readings all over the open area of the pipe, not just a single flow reading in the centre

 

[tombo]

if you want to measure actual suckage then you need to make a manometer
you just need some clear hose and some coulored liquid. Low tech but visual and can be very sensitive depending on the bore of the tube.

 

[Lee Brubaker]

Tombo has it right but neglected to tell how the tube with fluid is used. If the tube is clear plastic, plain water will do. Set the vacuum close to a wall, position one end of the tube close to the center of the vacuum outlet. The tube should be long enough to form a "U" with the water in the bottom of the "U". Turn on the vacuum & measure how high the vacuum pulls the water up the tube. The vacuum that pulls the water up the highest has the greatest amount of suction.

Lee

 

[CraftNav]

Thanks Lee & Tombo, I will build myself one of these

My main reason for building my 'gadget' was not to measure but just to compare.

I use to 'dabble' with two strokes and I know little tweaks / porting etc make a huge difference to gas flow and indeed Bill Pentz mentions some on his modifications page.

My overall aim is to make a shop vac as efficient as possible and then attach it to a mini cyclone to make the ultimate fine dust extractor for my hand held power tools.

oh ye and one day I'm gonna do some woodwork :wink:

will keep you posted

john