One for the boffins.... Suction and seperators

[rafezetter]

Part 1

I've got a rutlands 1100w extractor vac with a 100mm hose - rated at 50 litres per minute - no bar given. (capacity 50 litres)

I've also got an Lidl 1500w wet n dry with a 40mm hose - rated at 1.9 bar / 190 mbar / 19kPa - whichever works for you - no Litres pm given. (capacity 30 litres)

Both are cylindrical, motor is attached to the top - which separates leaving an "empty can".

Which has the higher suction, if I was using a 100mm hose?

Part 2

I've also got a 75 litre container (cost £5 delivered) - I had originally thought to just make a wooden lid and drop the rutlands motor onto it and add the 100mm hose, job done.

However now I've made my bench, by happy coincedence there's just enough room to house side by side either the Rutlands or the Lidl vac and use the 75 litre container as a separator, and hook up the 100mm hose for my tablesaw and planer thicknesser - which was the reason for buying the rutlands vac in the first place.

Seeing it all side by side today has only just twigged that maybe I could have used the Lidl vac and just bought a 100mm hose and saved about £75...

So the more powerful vac will be attached to the separator.

Anyone able to thunk this out? Coz it's well beyond me :?

 

[ED65]

My head hurts just trying to do the maths, could you find out which has the higher suction empirically instead? Probably the best method anyway, what are the chances that real-world performance on both matches the specs?!

 

[Trainee neophyte]

Connect the two fans together, add a ball delivery tube which can be closed (t-piece), and whoever collects the ball, wins?

 

[sunnybob]

i'm pretty sure you have your numbers mixed up. the rutlands would have a HOLDING CAPACITY of 50 litres agreed, but a LOT more than 50 litres per minute flow.
Same with the mbar, thats measure of pressure (or vacuum depending which way youre measuring it. Its NOT a measure of air flow.

EDIT.. the rutlands is 53 litres per SECOND air flow.

Second edit. I cant find the airflow for the lidl, but its a smaller container and will fill up faster regardless.
If the rutlands is the same as the SIP I had, then my advice is to go with that as I regret not replacing the motor on mine.

Make a cyclone and fit that on top of the spare bin, then youll only have to empty it every 100 litres.

 

[Sideways]

i'll offer you this train of thought.
Some fairly reputable sounding source on the web listed the minimum airflow needed to keep different sizes of hose "swept clean". The idea is simple enough, if you don't have a good enough flow, dust and lumps can settle out in your hose and make it more likely to block.
Small, high vacuum extractors can create a lot of suction but can't move that much air. Block the hose and you feel the vacuum, but use a big hose and the draught is pretty feeble.
I did some numbers for the well known NVD750 machine machine sold by axminster.
That has 2x 1200 watt motors and using it's numbers, it achieves the recommended minimum airflow for a 50mm hose.
The Axy has a 100m inlet as does one of your machines. This really isn't sensible. But it does look good and make it easy to connect it up to a machine that also has a 100mm port without any adapters.
I' forget the 100mm thing completely. Hook it all up in 50mm, use a cyclone or a second bin as you want, probably use the more powerful machine as chances are that will move more air than the smaller one. Any cyclone or second container adds a pressure drop (maybe 30%) and reduces airflow a bit but most of us seem to find them useful regardless.

 

[rafezetter]

TY for the replies - yeah it's a head scratcher innit?

I don't have the space for a cyclone on top of the separator, and although I could make up a smaller cart to do it that way - floorspace is a bit of a premium, hence using half of the space under the bench for that instead of drawers and storage, which isn't such a premium - has a shed attached to the work area but which is also full enough lugging a vac cart in and out isn't an option atm.

ok - scratch what I had written after reading sideways post - The reason I bought the rutlands 100mm machine is because the lidl vac just wasn't up to my planer in thicknessing mode, it blocked far too easily even with light passes.

My next question was could I hook up the lidle vac to the separator and have a 100mm hose from the separator, but with a pressure drop and what Sideways says that seems to be a non starter - literally.

Maybe at the time I could have got the separator, added a 100mm hose and put the lidl motor on top but it didn't occur to me.

Would reducing the hose diameter from 100mm to 65mm have a positive effect?

I think I might sit on this and ponder a while - and just use the rutlands machine while I do.

Feel free to throw more ideas my way - clearly innovation isn't my strong suit.