Has Anybody Tried Changing The Drop Slot's Width and Length?

[Kelly Bellis]

Portion of Hector's sketch (thanks Hector!) with drop slot shown highlighted in red. (Sorry about having used the attachment feature - I'm unclear on how to get images to display inline on this forum)

I've read that the the width of the drop slot (wds) is best suited at 1.125" and that an ideal diameter of the Thien Separator (labeled with an uppercase D in the sketch above) is equal to or larger than 20". I haven't read (yet) any discussion that mentions the wds being a ratio with D, while implicit in other readings, wds is always fixed at 1.125" irrespective of D.

Similarly, I have yet to read any discussion as to why the length of the drop slot (lds) is 240 degrees of arc. Phil Thien's original presentation; i.e., a separator lid, not the more popular so-called top hat, seemed to have been predicated on a shop vac, and a 2.5" round waste port inlet injecting from the top of the separator.

What miserable failure(s) has been discovered?; for example, using a continuous drop slot (full 360 degrees) and using a drop slot width of (D/2 * 0.1125)?

Phil Thien mentioned that he had gone through nearly fifty designs/variations during the course of approximately two years. Such persistence is inspiring with the results being most informative and very much appreciated! Equally informative have been other's experiments which have contributed to the validation of: rectangular section for the waste port inlet, elliptical bellmouths, and air straighteners. There's most likely more that I haven't learned yet as the posts here are numerous!

[alan m]

i think that width is a sweet spot for general use. too narrow and shavings will catch , too wide and you allow more air to spin in the barrel bellow . if i was building a dedicated seperator just for shavings i would widen out a bit  and if it was just for fine sanding dust i would narrow it a bit.
i dont think enough testing was done to really see the data on it. i wish i had a month spare with nothig else to do only try out all thee variables to see what happenes.

as for the 240 degrees. the same aplies, just a sweet spot. if the slot was longer then more air will spin below the baffle and create problems. too short and not enough dust will drop down

[Kelly Bellis]

Very good then, Alan. I'll stick with the 240 degrees, but the width of the drop slot I will make proportional with the diameter of the barrel that I'm planning on using for my first ever build of a Thien Separator using the wds:Diameter ratio for the stated general use sweet spot; i.e., 1.125":20"