no suck

[Rknott2007]

Is there anyway to create a bit more suck from an extractor, other than buying a bigger one? mine is an axminster fine filter extractor, with a 4in hose connected to a small 2 1/2 in ducted system, it works well near the extractor but 4meters away and two 90degree bends there is a considerable lack of air flow, any thoughts or suggestion?

 

[Mailman14]

Only a suggestion - have the 90 degree sections got plates in them? sort of at 45 degrees (like a periscope has mirrors).

Can you change the port in the housing to 2 1/2"? There may be a void area where the 2 1/2 enlarges to 4" - which will reduce flow.

Can you put a hoover type 'flat nozzle' on the open end - this will reduce the cross section for suck, but should in theory improve the speed.

Have you checked the filters? BOTH in and out?

HTH

 

[Mailman14]

RE:90 degree bends - can you change to a large radius bend instead - that would help - also is it 'straight' tube, or the 'spiral' type? Spiral works better (like rifling a bore in a gun).

 

[Doctor]

also is it 'straight' tube, or the 'spiral' type? Spiral works better (like rifling a bore in a gun).

Are you sure? :shock:

 

[Niki]

To get the best airflow from a given motor power/impeller design;

Use the shortest possible hose...

Use a smooth inner wall hose...

Try NOT to use "elbows" and avoid "bends"...if you must, use a 30° elbow (or less)...

Do not reduce the hose diameter - the total airflow will decrease...If you want, you can make an experiment;
Turn the DC "ON" with full open hose and listen to the motor noise level...
Now, close the hose partially and listen to the motor...the motor RPM will increase...because, there is less airflow and it's easier for the motor/impeller to turn (and the Amperes will decrease)...

All the above will reduce the "Boundary layer" effect and the "Duct losses" and will give you the best airflow from your set...

Regards
niki

 

[bluezephyr]

I was led to believe that vacuum type extractors increase suction when reduced whereas the larger extractors dont benefit from being reduced.
When you put the crevice tool on a household hoover, more suction


when i used the smaller clear pipe the dust would spiral down it even though it was straight pipe.

 

[woodbloke]

If it's a HVLP extractor, ie a conventional double bag unit (ie Ax2200) then these are not suited to a form the basis of an extraction system where the hose dia reduces. What's needed is a LVHP sucker...in other words a decent powerful vacuum system such as the Camvac 386 - Rob

 

[TinBox]

A fan type extractor, which I think you are referring to is designed to move large amounts of air "gently", the vacuum effect is very low. Reducing the diameter of the pipe - anywhere along it's length - vastly reduces its ability to move that air. There is no getting round it unfortunately.

To get more "suck" (vacuum pressure) you need a vacuum type system. Again these can be thwarted by reducing pipe diameter but as they work at much higher levels of vacuum their capabilities appear less diminished. One downside of reducing the airflow on these is over-heating as they are invariably cooled by the air flow.

Best flow will always be achieved using matched pipe diameters with as few bends as possible.

It's a shame that sucking and blowing don't work in the same way. You can compress air to 10bar easily (with a race bike pump for example, by hand) but only vacuum it down from 1bar to 0 with ridiculous amounts of precision engineered equipment.

edit: woodbloke hit it on the head in simple terms, that's what happens when you answer the phone in the middle of responding. HVLP systems are for chip removal from a single machine, LVHP are for extraction systems. Camvac are belters, if a little bright green

 

[Mailman14]

also is it 'straight' tube, or the 'spiral' type? Spiral works better (like rifling a bore in a gun).

Are you sure? :shock:

Am I wrong? During employment at an air filtration sytem manufacturer, that is all we used...

I am NOT saying use flexible tube (like clothes driers have) - that would be silly :shock: , as the air is taken into the ridges - I'm talking about a long piece of metal twisted into a spiral, with ONE long seam down the length. :lol: That's what I meant to say, above, sorry if it didn't seem like it

 

[ivan]

It takes several times more HP to deliver (or remove) the same amount of air through a 2" pipe than a 4" pipe. the 2" pipe has a lot of flow resistance, even with a vacuum cleaner style extractor. Bends, especially of small radius like those sold in kits etc. (2" waste pipe sweep bends are almost OK) add a lot more resistance too. Your vac will thus shift the most cuft/min with a 4" pipe.

However....to carry off dust and shavings requires a minimum speed in the pipe, about 4000 ft/minute; almost certainly your vac will not be able to move enough cu ft /min to generate 4000 ft/min flow rate in a 4" pipe. The manufacturer should specify the max volume air flow, so you can calulate the maximum diameter pipe that will give the 4000 ft.min. Because this will be a small diameter, the flow resistence will be high, and performance will drop off rapidly as pipe length increases. No free lunch, I'm afraid.

 

[Jake]

almost certainly your vac will not be able to move enough cu ft /min to generate 4000 ft/min flow rate in a 4" pipe.

That's interesting, I didn't know that stat. That suggests only the 3 motor Camvac is up to 4" pipe - just about, 3815 fpm by my calcs.

 

[Rknott2007]

Would the axminster ade2200 make a good extractor for a 4in ducted system if fitted with the fine filter cartridge, i see its on offer

 

[RogerS]

Ah..you're back. Did you get the copy of the spreadsheet that you asked me for in January and which I sent to you by return to your aol email address?

 

[Rknott2007]

cant recall receiving one? yeah getting back in the workshop after a family crisis