Building a large Thien baffle - Dust collection

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That looks about right Siggy. I have contemplated pulling the impeller out and making my own one slightly larger, but I'm aware that you can overload the motor if it pulls too many amps. Are you able to test the load using a multimeter do you know?
 
Most multi-meters are rated for very low currents. I would suggest using one of those power plug meters for monitoring energy consumption as the best way to test.

I have a spreadsheet somewhere for approximately calculating power requirements for impellers (downloaded from woodgears and tweaked) - if you PM me your e-mail address I'll send it on.
 
I've got one of those diverter bin lids on top of a 200 litre plastic drum and I then extract the dust outside - what little there is of it.

Works brillant
 
So I increased the width of the baffle slot from 30mm to about 50mm to help with the chip diversion for planer shavings. After putting it back together, I measured the airspeed from the same position as before.

30mm slot: 12.8m/s
50mm slot: 14.5m/s

Wow, what a difference! I'm shocked it's had that much effect to be honest, but I'm not complaining!

I also

Added a small triangular piece of wood to help deflect the airflow into the slot, which seems to be working well. I now get minimal shaving build up, and it clears pretty easily.
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How come you didn't make the outer edge of the drop slot level with the inner face of the baffle Matt? All the other threads I have seen show that it should be arranged thus to provide an unrestricted route for the chips/dust into the collection bucket. Have you noticed any build up of dust on the lip?

Maybe you could try adding a heavy chamfer to the underside of the chamber bottom plate. Apparently this will assist in the capture of material by reducing turbulence at the edge of the slot. I have done this with mine, chamfered enough to leave about 3mm of vertical material remaining. I made it this way from the start so have no before-after comparison.

Good news on the air flow increase but I cannot work out why this has risen by widening the channel. Have you observed any other improvements other than the airspeed increase?

Personally I think the Thien design can be tweaked for forever and a day and completely over engineered with negligible increase in performance. There is potential for disappearing down a Thien Baffle Rabbit Hole, therefore I believe the ultimate tests have to remain that "Is the air coming out cleaner than when it went in?" and "Is that air now clean enough to breath or be released outside without causing a nuisance to my neighbours?" I would be interested to hear your thought on that.
 
will1983":2iyji7it said:
How come you didn't make the outer edge of the drop slot level with the inner face of the baffle Matt? All the other threads I have seen show that it should be arranged thus to provide an unrestricted route for the chips/dust into the collection bucket. Have you noticed any build up of dust on the lip?

Maybe you could try adding a heavy chamfer to the underside of the chamber bottom plate. Apparently this will assist in the capture of material by reducing turbulence at the edge of the slot. I have done this with mine, chamfered enough to leave about 3mm of vertical material remaining. I made it this way from the start so have no before-after comparison.

Good news on the air flow increase but I cannot work out why this has risen by widening the channel. Have you observed any other improvements other than the airspeed increase?

Personally I think the Thien design can be tweaked for forever and a day and completely over engineered with negligible increase in performance. There is potential for disappearing down a Thien Baffle Rabbit Hole, therefore I believe the ultimate tests have to remain that "Is the air coming out cleaner than when it went in?" and "Is that air now clean enough to breath or be released outside without causing a nuisance to my neighbours?" I would be interested to hear your thought on that.

I wanted to maximise the diameter of the cylinder to ensure I had sufficient airflow. I had considered going no bigger than the internal diameter of the container, but decided to err on the side of caution - always easier to reduce the diameter of the baffle than increase it!

Before I put the deflector in, a small amount of dust would gather around the perimeter, but with the deflector in its down to hardly anything. I think it's a good solution for people to consider if their container isn't quite as big as they'd like.

I have no idea why increasing the channel width has increased airflow - I can only assume it's allowing a larger vortex to be created.

One other option is that the bin is about a third full now - I have seen a video from someone on YouTube who noted that the performance of their cyclone increased as the container filled up, so it could be that. I'll empty the bin and test for comparison.

I agree regarding finding a balance in performance - it is tempting to keep tweaking. I wish I had a design program that could stimulate fluid dynamics!

As for your two criteria - the thien eliminates every speck of chips and dust other than the very finest and any invisible particles, so the separation is outstanding. I wouldn't breathe it without some sort of filter that's able to capture the sub 5 micron particles though.

I'm more than happy to vent outside, without fear of neighbours complaining - they wouldn't be able to see anything visible coming from the vent.
 
It's just under 2mm thick flexible poly something. In reality, it's a bit too flimsy for this extractor and deforms slightly when switched on. I think I'll buy some 3mm in the future and upgrade it.

Fun to see the dust swishing around though! It goes nuts when I'm thicknessing!
 
MattRoberts":336k4wcj said:
Fun to see the dust swishing around though! It goes nuts when I'm thicknessing!

This is the only regret I have with my separator, the plywood walls prevent me from seeing the swirling in action.
I was being tight and just using what material I already had in the workshop.
 
MattRoberts":2yvkph4s said:
It's just under 2mm thick flexible poly something. In reality, it's a bit too flimsy for this extractor and deforms slightly when switched on. I think I'll buy some 3mm in the future and upgrade it.

Fun to see the dust swishing around though! It goes nuts when I'm thicknessing!

The only sheet I can see on eBay is acrylic and at 3mm I would have thought that would have been a bit hard to bend.

Regards

Phill
 
I bought mine from an online plastic specialist. Acrylic would be too stiff - I think mine is polystyrene or poly vinyl. The tops confuse me!
 

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