Dust extraction - airflow requirements?

[Monkey Mark]

I'm still consider building my own extractor system. I have a "snail" type blower lying around. Does anyone know what sort of airflow would be needed for a 3 or 4 inch system?
I'm not sure if my blower is up to the job and no point wasting time building an enclosure if it's not.

 

[CHJ]

If you look at the flow rates quoted for machines from most sources they start at 850 m³/h (single machine/small shop) and go up to some 2000 m³/h (multiple machine/bigger shop)

 

[wallace]

Them snail fans are good for air cleaners but I doubt they would be any good as extraction. You need something with an impellar that's going to move a decent amount of air. Also when you look at the bumph that comes with bought extractors I would disregard the quoted air flow. They don't move the quoted air in the real world

 

[Monkey Mark]

I thought the snail ones were impeller a?

Mine looks similar to this oneone URL: [url=http://pages.ebay.com/lin...ges.ebay.com/link/?nav=item.vi ... 20&alt=web[/url]

There's a few that look the same but with very different airflow. I'll check see if mine lists it but doubt it as it was from an air handling unit.

 

[CHJ]

That type of fan will only be suitable for clean air ventilation or at worst very fine dust movement, it will clog up rapidly if any chippings get as far as the fan ring.

Even a six bladed impeller fan can block all to readily with shavings from a lathe or hand plane for instance.

 

[PAC1]

Look on Bill Penz website. It is all there

 

[Monkey Mark]

That type of fan will only be suitable for clean air ventilation or at worst very fine dust movement, it will clog up rapidly if any chippings get as far as the fan ring.

Even a six bladed impeller fan can block all to readily with shavings from a lathe or hand plane for instance.

I intend to use it with a cyclone separator. Space is limited in my garage but it has a pitched roof so I'm thinking of putting the unit in the roof space. With a filter on inlet and exhaust or inlet and exhausted directly outside.

 

[Monkey Mark]

Look on Bill Penz website. It is all there

Will do, thanks for the suggestion.

 

[Myfordman]

A few key features of my set up

I use 3hp motor 2850 rpm with 14" blower, a home brew cyclone and that serves 8 drops (1 at a time) with 110mm soil pipe total pipe run is about 25m. Copes with 8" jointer at the furthest point and all that a 13" thicknesser can throw at it.

 

[Monkey Mark]

Look on Bill Penz website. It is all there

Whoah there, I information overload! Plenty on there if you had the time to waid through it but a bit too much for me.

 

[Monkey Mark]

A few key features of my set up

I use 3hp motor 2850 rpm with 14" blower, a home brew cyclone and that serves 8 drops (1 at a time) with 110mm soil pipe total pipe run is about 25m. Copes with 8" jointer at the furthest point and all that a 13" thicknesser can throw at it.

I don't think mine will be powerful e ough. It's at work so can't check but think it would only be about 0.5hp. I may have a second and go twin.

However, I think I may just look for something more substantial.

Doing a rip out at work soon, maybe something appropriate to find.

 

[Monkey Mark]

I keep seeing bouncy castle inflators going cheap. Hmmmm, I wonder.

Or even 12v fan from an engine bay. Easy to add extras should it be needed.

I hate being on such a tight budget but as they say, necessity is the mother of all invention.

 

[Monkey Mark]

I keep seeing bouncy castle inflators going cheap. Hmmmm, I wonder.

Or even 12v fan from an engine bay. Easy to add extras should it be needed.

I hate being on such a tight budget but as they say, necessity is the mother of all invention.

After some reading it would appear car fans are a no no. They can move air but are not good at creating suction, so if placed into an enclosure would be rubbish.

Bouncy castle blower may still be an option.

 

[CHJ]

Unless you really know what you are doing and can produce a design that avoids multiple fans fighting each other for adequate airflow resulting in fan blade starvation (cavitation) then forget trying to use more than one close coupled unit.

 

[Myfordman]

For the lowest budget solution I'd concentrate on getting a decent induction 2 pole motor 2-3hp. You can make an impeller and snail housing fairly easily and there a numerous approximations to a cyclone out there or the Pentz "perfection" version. Blast gates can be home made too.
Pipework is possibly cheapest from toolstation and free delivery.

 

[nicguthrie]

Just my tuppence worth, but I'd suspect that while using old, second hand motors to make home made extractors, you'd want to be especially careful to avoid any chance of the fine wood dust "leaking" through to being in contact with any part of the motor or electrical contacts.

It may seem perfectly obvious on paper like that, but you'd be surprised how many folks don't realise that a good suspension of wood dust in air + electrical spark = full on explosion of the potentially terminal kind. There's been a fair number of accidents over the years caused by it.

Be safe fellas.

Also, My dual motor Numatic extractor is 750m3/h and it's pitifully under powered when using its 100mm hose. Something I wish I'd known earlier - it can't handle careful cuts on my bandsaw without using the smaller vacuum cleaner sized nozzle mounted directly under the table insert. A P/T trying to use that thing would choke in seconds.

Nic.