Thread: Mini Cyclone still clogs the filter

In the upper section of a cyclone it's all about air speed, radius (diameter) and particle size (mass), to separate the smallest particles out of the (turbulent) air dust mix and keep them against (or close to) the wall of the cyclone there must be sufficient air speed to do so, (given that the radius of the upper doesn't change and the mass of the particle stays the same) what you don't want is the small particles not being separated out and remaining in the airstream and going out the outlet, at this point you have lost the game (for the small bits at least) and it wont really matter what size the outlet is, although an outlet that is on the larger side would probably have less turbulance at the inlet to the outlet (which is desirable) which might be where Graeme is pointing

I think BP says the area of inlet should equal the area of the outlet, been a while since I looked at his site.

Without really knowing what happens inside a cone this is what I reckon....the conical section provides a rotating mass of (hopefully) clean air at the center where the inlet to the outlet should be, the roating mass of air helps to maintain the speed of the particles out against the cone wall, also the shape helps to and possibly increases the speed of the particles before then dropping into the collection bin, the collection bin being another area where hopefully there is no air flow (but probably air movement)

The inlet should extend thru to the centerline of the upper cylinder but if it does this then it should also be pointed down at the appropriate angle because if it is level the air/dust mix will be crashing into the inlet every turn and causing massive turbulence, the end result possibly being worse than if the inlet was level and left flush with the upper cylinder, the minimum I would suggest for John to do is point the inlet down 10ish°


Pete

Originally Posted by pjt

I think BP says the area of inlet should equal the area of the outlet, been a while since I looked at his site.

I could not find where Bill Pentz discusses inlet/outlet sizing, but in his drawings for an 18 inch cyclone:

* Circular outlet diameter = half cyclone diameter = 9'

* Rectangular Inlet height = half cyclone diameter = outlet diameter = 9"

* Inlet width = half inlet height = 4.5"

Thus:

* Outlet Area = Pi * (9/2)^2 = 63.6 square inches

* Inlet Area = 4.5 * 9 = 40.5 square inches

* Outlet Area/inlet area = 63.6 / 40.5 = 1.57

Thus the area of the outlet is almost 60% larger than the inlet.

Bill's Cyclone & Dust Collection Research - Cyclone Plans

I have seen other sources advocating even larger outlet diameters - up to 70% of the cyclone diameter - than the 50% ratio apparently advocated by Bill. But I am unsure of the science, there.

Fair Winds

Graeme

Good to see you are on the ball Graeme, 60% is quite a significant difference,
I have made a large and small cyclone and made them both with equal inlet outlet areas, seems to work OK certainly wouldn't go smaller on the outlet


Pete

Originally Posted by pjt

Good to see you are on the ball Graeme, 60% is quite a significant difference,
I have made a large and small cyclone and made them both with equal inlet outlet areas, seems to work OK certainly wouldn't go smaller on the outlet


Pete

Good Morning Pete

Interesting; were your large and small cyclones used on the same system? If so, how did they compare?

Fair Winds

Graeme

HI Graeme,
The small cyclone's home is on the drop saw, it also gets used elsewhere depending on the job, I did a WIP https://www.woodworkforums.com/f200/v...ne-wip-129797/

The large is the main system that all my other machines are hooked up to
dust collector.jpg

This one is a bit interesting, it's looking up the cone to the impellor, you can see the clean tracks around the inside of the top cylinder, also looks like some polishing of the weld at the junction of the cylinder and cone, the chips/dust do about 3 turns that can be seen before dissappearing, it also shows the importance of angling the inlet duct down so that the air/dust mix that has done 1 turn doesn't crash into the incoming air/dust
looking up the cone.jpg


Pete

Thanks, Pete. As ever a picture says more than a thousand words....

Looks like an effective set-up.

Fair Winds

Graeme

BTW, I went to the Melb Woodwork show today, and carbatec was selling the mini dust deputies for $170. Most had gone by the time I saw them.

I didn't get one as I hope to make an updated/better version of mine.

I can recommend the dust deputy. Carbatec now has the DIY version of the dust deputy for $69-... but you have to supply all your own fittings. It works well. Better than I expected and probably better than 99%. I tested it with some chalk from the kids blackboard and it collected all of it.

I have it siliconed and bolted to a large metal Paint tin and driven by 2 old household vacuums. It does not block up the vaccums paper bags. I use it on the CSMS, Sml contractors table saw and the router and to vacuum the floor.

I was trying to build my own cyclone from sheet metal and other bits on and off over 18 months. Needless to say my metal and soldering skills were not up to the task. The DIY Dust Deputy was a very quick fix and at $69- plus some fittings I consider it a cheap fix too.

I imported one of the DIY dust deputys from America. This was only possible because I have family in the USA who received and posted the box to Australia on my behalf. The cost was $USD 39- and postage about $USD 20-25.

This week Carbatec has them available at $69-. I saw them 2 weeks ago when I visited carbatec and they are exactly the same as what I organised.

Hope this helps


Andy T

$69? Dammit, I just spent a half-day working out plans to make my own!!!!! No excuse not to buy one now!

Originally Posted by Master Splinter

No excuse not to buy one now!

It's not as much fun as making your own!

Since my original posts I've slowly worked on it every second weekend or so. Progress is slow, lots of trial and error, but I'm getting close now. I'll post a set of photos once it's done.