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Thien Baffle on the fly project #3: day 3

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Blog entry by Holbs posted 151 days ago 853 reads 0 times favorited 7 comments Add to Favorites Watch
« Part 2: day 2 Part 3 of Thien Baffle on the fly project series Part 4: day 4 »

I purchased the 1/16” lexan poly-carbonate with dimensions of 16” x 60” for $32. Routed a 1/4” groove for the lexan to sit in, top and bottom. Cut all the support pieces and slapped it all together for a dry fit run. Here is the result:

So far… it does not look like I’ll win a beauty contest with it, but it will fit my utilitarian funtion. I made alot of mistakes and errors which have given me much needed experience in working on MDF, using Microfence jig, first time really using my bosch 1617 router, etc.
Next will be cutting a 13” diameter thru the top of the baffle for the 7” bellmouth outlet, assembling inlet 6” (well, actually 8” x 4.5”) port, and doing a function test. Who knows, might not have to silicone or caulk or whatever to seal up the chamber as everything was a good tight fit.
And notice.. the baffle cut out arc has been changed from my previous error: the opening now starts much later and the end stops right before the inlet.



7 comments so far

View scoobydooo9r's profile

scoobydooo9r

135 posts in 2380 days


#1 posted 151 days ago

That looks great! I always find that with enough caulking, I never make mistakes! Can’t wait to see it up and running.

-- I don't make mistakes, I make design challenges!

View WoodES's profile

WoodES

20 posts in 295 days


#2 posted 149 days ago

Looks like a winner to me.

I used clear duct tape on mine and I have no glued parts. This allows me to access the interioror replace the poly-carb should it be necessary.

My slot starts closer to the inlet and stops earlier. I have observed that the chips drop out of the air flow and the beginning of the slot and less so at the end.

View Holbs's profile

Holbs

513 posts in 634 days


#3 posted 149 days ago

ES… with my dry run, I took strong notice to see if there was any flex in the lexan. Right now, the 1/16” lexan sits in a 1/16” groove top and bottom with 6 outer structure supports. It didnt flex at all. With the lexan being bent like it is, I do not think any fasteners or glue or tape is needed. Yet :)

View WoodES's profile

WoodES

20 posts in 295 days


#4 posted 148 days ago

Good, remember now you have very little restriction on the inlet side. Should you ever have a clog, or heavy chip load the weakest point will give. It could be the lexan.

View Holbs's profile

Holbs

513 posts in 634 days


#5 posted 148 days ago

ahh..good point that i did not consider. somewhere along the way, i was going to look into what Bert did with a auxiliary emergency valve that opens at a certain pressure. might have to look into that pretty soon.

View WoodES's profile

WoodES

20 posts in 295 days


#6 posted 148 days ago

I am not sure what pressure setting would be used for relief. I suspect it would be rather low. As you have a large lexan surface area, even a low pressure on a large surface generates a large force that you would have to support with the grooves.

Example: 20” dia baffle x pi (3.14 not cherry) gives you ~60” circumference x 16” height, resulting with an inner surface area of 960 sq in. You multiply that by your assumed psi and you get the force that must be resisted by the lexan. 1 psi provides 960 lbs, 10 psi 9600 lbs. etc.. All of this is suction and the vertical supports contribute nothing to support the lexan for this suction pressure.

As there are many examples of thin gauge metal duct collapsing under the suction pressure of a dust collector, one can envision a similar situation with a large separator.

View Holbs's profile

Holbs

513 posts in 634 days


#7 posted 148 days ago

good point.
someone else used some screws to afix their lexan to the supports with no down sides.
good thing i made that auxiliary 14” cut out uptop for future things like this.

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