45 or 90 degree el on a Shopvac Separator Lid/Baffle??

[Dave]

I've wandered (searched) the archives and haven't (yet) gotten my question directly answered.  I'm about to build up a "classic" Thien Cyclone Separator Lid w/ the Thien Cyclone Separator for a 2.5" shopvac. 

My question is has anyone determined if either a 45 or 90 degree el is better on the input side below the lid and above the baffle,  all things being the same as shown on Phil's site?

Or am I (yet again) picking nits?

Thanks,
Dave

[Joes Username]

In any sort of flow (air, water, etc.) the more or a radios the more residence which slows down the flow.
If you search for "dust collectors ductwork layout's" you will find using 90's is considered a no-no any where.
If you 'have' to use a 90 it normally performed to use two 45's with a strait pipe between.

Do an experiment and see what you find out for yourself.


_

[Dave]

Actually I was toying with the idea of using another of the same vacuum hose fitting (as Phil used on top of his unit where you attach the hose), and mirroring it (or rather rotating 180 in the X axis and rotating again in the Z axis 180 deg) underneath in place of the white PVC 90 degree el he has shown in his example.  

I'm suspecting it would keep the flow of debris relatively straight till it ultimately gets to the baffle at bottom of the lower fitting.  Much less drastic flow change than a single sharp 90 el to my way of thinking.  That's why I was asking.  I'd rather build on proven designs instead of re-inventing the wheel yet again. I doubt I'm the first to at least think about this, yet again ask about it.

-Dave

[phil (admin)]

Absolutely use a 90.

You need the dust to ROTATE, not hit the baffle and splatter.

If you try two of the hose fittings, you'll be disappointed.  I know I was.  :)

[Dave]

Absolutely use a 90.

You need the dust to ROTATE, not hit the baffle and splatter.

If you try two of the hose fittings, you'll be disappointed.  I know I was.  :)

Thanks for the answer Phil.  From a layperson's perspective I'm a bit surprised.  But since you have already tested it  I'll go with the PVC 90 el.  Like I said. Why reinvent the wheel.

Thanks for this blog & letting me know the right path to take.


OK.  My break's over. Back out to cutting MDF out in the shop.


-Dave

[dbhost]

Or do a side inlet...

[Dave]

Day Two Questions:

Two things popped up that I need further clarification on. (I can't wait for 3D web pictures!)

First one is Phil's original 2.5" example mentions how the relationship between the back of the 90 is compared to the start of the 120 degree section.  In the pictures it seems to show a "sharp" 90 deg el.  I took up Chuck's idea of a long sweep 90.  

My question is the long 90 end point is quite a ways farther towards the middle of the 120 degree section than is pictured with Phil's short 90.  Should I leave it as shown,  or rotate the baffle a few degrees to better line up the end of the 90 in relation its location on the 120 deg section of the baffle?

Second question is Phil you mentioned that you set back the 90 elbow .75" from the edge.  And the picture seems to show it about that distance -as it comes out of the lid.  My question is how the 90 is rotated horizontally.  Is it so that the lower end of the 90 is touching the inside edge of the can, or is it also turned away from the edge of the can a bit?  I can't tell from the 2D pictures.

I've got everything dry fitted into the can and on the bench.  Once I find out these two questioned answered I'll glue the piping. in place.

Thanks for your answers.

-Dave

[phil (admin)]

(1) Rotate the baffle a little so the long 90 ends about the same place a short ell would end.

(2) You want the 90's exit to be tangential to the side of the can.  That is impossible, of course, but try to get it as close as possible.