Improve my dust extractor

[mindthatwhatouch]

Hi,
After some advice on the best course of action for improving this cyclone that came with my table saw, I’ve added the plastic waste drum and filter box. I have been using it with a couple of lengths of flexible duct, on the table saw and bandsaw, now I’ve added a lathe it’s time for a tidy up and a more efficient system. So some ducting (100 mm waste pipe) and possibly moving the huge thing outside, to its own little shed. If it goes outside I’ll lose the hepa filters.

Whilst I’m happy with the performance from a filtering point of view, just feel for the size of thing it should have a bit more oomph. Collection from the table saw is not brilliant, filter box contains two pleated air filters followed by two hepa filters. Very little dust on the filters when I change them.
As the cyclone is steel, no makers mark but very well made, changes to it are not easy, so I need some guidance, as to the best course way to go, I don’t mind putting in the time and effort but don’t want to get into experimenting. I’ve read Siggy’s excellent dust extraction tutorial and spent a fair amount of time on bill pentz site.

So my thoughts are:
1, The impeller seems quite small for the size of the cyclone, also the gap between the scroll and the impeller seems too large, 50mm at its least increasing to 80mm, is there a rough and ready rule of thumb for Gore point gap and Volute sizing, lots of very technical info online that’s beyond me. Do I build a new impeller Matthias Wandell style.

2, the central tube, no idea what it’s called visible through the small door, in the photo, which is 170mm diameter should this extend up towards the impellor? I must measure the gap.

3, fitting a neutral vane, or a spiral ramp, how much will these improve things, I guess an increase in inlet size will help either way.

4. when I removed motor housing for a look, see and photographs it was coated with a very fine layer of dust. If I stick with this impeller will polishing it help?

5. how do I test my improvements? Will a Manometer for pressure drop suffice.
Sizes and photos attached, thoughts please

3, fitting a neutral vane, or a spiral ramp, how much will these improve things, I guess an increase in inlet size will help either way.

4. when I removed motor housing for a look, see and photographs it was coated with a very fine layer of dust. If I stick with this impeller will polishing it help?

5. how do I test my improvements? Will a Manometer for pressure drop suffice.
Sizes and photos attached, thoughts please.

 

[Inspector]

The choke point is the 4"/100mm duct in the system because no matter what dust collector you use you can't pull much more than 400CFM/680 cubic metres per hour (if my conversion is correct). A 6" duct can move 1,200CFM/2,040 cubic metres per hour.

The impeller is too small and I doubt you can coax more out of it. The cyclone itself has resistance like the ducting to overcome and is probably more than the impeller can draw. In the Pentz site he recommends 3hp as a minimum with a 13" or 14"/330mm or 355mm impeller. That being with a short duct to the machine. His cyclone design spreadsheet if I recall correctly for 3hp has a diameter of 24"/610mm. The 5hp and 15"/380mm impeller is 20"/510mm because it has the power to spin the dust faster. Lower powered cyclone has to be bigger to separate the dust without incurring too much resistance.

If you have the skills to make and weld in a neutral vane then you have the skills to make a properly sized cyclone using Bill's spreadsheet in the Projects area and put it outside. You would have to get the motor and impeller but he has the information on making the housing, also in the Projects area. Do it right and you'll be able to capture virtually everything from your lathe.

Pete

 

[mindthatwhatouch]

Thanks Pete,
Yes I’ve read (several times) bill pentz website. unfortunately impellors, filters and the like seem to be a bit harder to come by in this part of the world, certainly not keen to build something even larger.
Just trying to get more bang for my buck from this cyclone, was hoping that someone with more experience of such things would point me in the right direction of the best way to go.
@siggi_7 ?