Thread: 2hp dust extractor mod - build

I am a big fan of Bob's optimised 2 HP dusty because it puts decent dust extraction within the reach of most woodies. Enclosing the dusty and venting to the outside is a big plus.

Please let us know how you go.

Thanks John. I'll be posting here as I go to get a bit of feedback along the way.

Trav

So I got to strip down the dust is weekend. This is her fully dressed

Removing the forked inlet you can see that it is actually less that 5" intake, further impeded by a metal guard to presumably stop big things hitting the impeller. In reality, I guess it just slows things down even more.



Finally, the impeller outlet, with an inside dimension of 156x105.

My first job was to remove the connecting hose and replace it with an mdf connector that will eventually be connected to the bag housing. I made a box with the same internal dimensions as the impeller outlet, and marked at cut the appropriate arc to match it with the bag housing. Trying to fit this on the bag housing is interesting, as the housing is not straight, so there are a few gaps. Nothing that a few screws and some silicon won't fix. My next job is to cut the appropriate hole in the housing, but I need to think through the placement first.



The second job is to remove the impeller/intake cover and replace it with a new, improved mdf cover. I've cut the disc from 12mm mdf but I need to get the 6" pipe to perfectly size the intake cutout. I'll do that next weekend.

Trav

Thought I'd seek some views on mounting the dusty.

The photo below shows the little alcove where it will be housed. It is 940 wide by 1200 deep. The door on the RHS is to the outside.

My plan is to mount the dusty directly to the back wall, with the bag housing directly in front of it. I will have the ducting coming out of the bottom, running along the floor around the edge of the room.

What's the best way to mount to the wall? It has 6 bolts holding it down at the moment, so I was simply going to dynabolt it to the wall. Do I need anything to minimise vibrations?

Eventually I will vent through the door to the outside, and block off the alcove with a removable panel. I was thinking of a sandwich of two sheets of mdf with insulation/foam between them. More on that later.

Trav

Originally Posted by Trav

What's the best way to mount to the wall? It has 6 bolts holding it down at the moment, so I was simply going to dynabolt it to the wall. Do I need anything to minimise vibrations?

It sounds like a brick wall - if so you need do nothing else.

Originally Posted by Trav

The second job is to remove the impeller/intake cover and replace it with a new, improved mdf cover. I've cut the disc from 12mm mdf but I need to get the 6" pipe to perfectly size the intake cutout. I'll do that next weekend.

Using an inverse Bell Mouth hood is really worth adding to the Impeller inlet - have a look at how I did mine.
If you don't have a lathe then use a router with as large a round over bit as you can get will be better than nothing.
Remember the rounding should come out flush with the inside of the impeller and not intrude into the impeller otherwise this will cause a problem.

Thanks bob. I was planing to add a couple of layers of mdf then using a big round over bit to shape the lip. No lathe.

In terms of a bell mouth, 6" pipe comes with one end expanded to allow it to join other pipe. Would using this end make any kind of difference or do you need a bigger bell mouth?

Trav

Originally Posted by Trav

Thanks bob. I was planing to add a couple of layers of mdf then using a big round over bit to shape the lip. No lathe.

In terms of a bell mouth, 6" pipe comes with one end expanded to allow it to join other pipe. Would using this end make any kind of difference or do you need a bigger bell mouth?

Yes you would just need a bigger bell mouth.

Normally it would be better to go bigger and use a bigger bell mount but its not advisable for the ducting entering a standard type impeller to be more than half the diameter of the impeller otherwise the impeller will not develop its proper pressure differential. '

So, if I had a 12" impeller, the mouth of the bell will be 9" and curving into a 6" inlet pipe?

Originally Posted by Evanism

So, if I had a 12" impeller, the mouth of the bell will be 9" and curving into a 6" inlet pipe?

Yep

Originally Posted by Evanism

So, if I had a 12" impeller, the mouth of the bell will be 9" and curving into a 6" inlet pipe?

Which explains the use of a modified flower pot to get the tapered reduction. I think I need to go plant hunting this weekend to find a 225mm plant. It's just about tomato time, right?😉

Originally Posted by Trav

Which explains the use of a modified flower pot to get the tapered reduction. I think I need to go plant hunting this weekend to find a 225mm plant. It's just about tomato time, right?

Although they serve the same purpose, tapered ducting is used in a different situation than where a bell mouth hood would be used.

A tapered duct is the recommended way of going from one size duct to another.

Bell mouths are used when going between open air and an open duct
OR
Between a duct and any larger chamber e.g. an impeller or even a machine.

If we wanted to get the very last CFM out of a system all the machine ports would use reverse bell mouths.

If 6" ducting is used and the impeller has an 8" inlet the ideal way to connect the two would be
- 6" ducting
- 6 to 8" taper across 1.5m
- 1.5m of 8"ducting with a bell mouth entry into the impeller.

Thanks bob. Will look at bell mouths to see what I can do. Can anyone recommend a simple place to buy something that would work as a bell mouth? I've seen a few pot plants around with that profile, but I'm not sure of the size.

It's not a bell mouth, nor is it cheap, but what about something like this?

$28 from masters.

https://www.masters.com.au/product/9...teel-150-200mm

Trav