bell fittings

[alan m]

hi there.
i have been researching bell inlet designs.
i am finding info that specs it at for a 6" pipe there should be a 2" raidiused section and then a flat  horizontal section.
so the over all measurment of the outside would be 12" for a 6" pipe.

does this sound right. 



i am finding the info on having the bell at the start of the outlet . do you think that there would be any point putting another on the exit end of the outlet.
from what i know about dust colection ,it is all about reducing pipe lengths and turbulence on both sides of the impeller .
so if it works on one side it should work on the other.


what do you think.

[retired2]

hi there.
i have been researching bell inlet designs.
i am finding info that specs it at for a 6" pipe there should be a 2" raidiused section and then a flat  horizontal section.
so the over all measurment of the outside would be 12" for a 6" pipe.

does this sound right. 
Yes, it matches Spiral Manufacturing's dimensions for their commercial bell mouth fittings.


i am finding the info on having the bell at the start of the outlet . do you think that there would be any point putting another on the exit end of the outlet. Only if you are building a musical instrument.
from what i know about dust colection ,it is all about reducing pipe lengths and turbulence on both sides of the impeller .
so if it works on one side it should work on the other.    Very unlikely.  The aerodynamics of the bell mouth eliminates turbulence of air rushing into the mouth of the inlet.  The dynamics are very different for exiting air.

what do you think.

http://www.jpthien.com/smf/index.php?topic=550.0

[alan m]

i am having trouble finding bellmouth fittings in the uk (im in ireland). there are loads in the us but shiping such a delicate and bulky item is risky.
i am awaiting a price from a uk company but it will probably be astrinomial.

i am thinking of making one (i need 4, one for each seperater and one for the seperater in the dc unit, and one spare for a second dc unit that i havent bought yet but might need)

i am thinking of either spining it on my wood lathe (dangerous  with no experience like i have ) or using fiberglass and carbon fiber etc to mould it over a formaer i would turn on the lathe.

what do you think . will it work. are there any side affects to having a fiberglass etc part inside the seperater like this

any other ideas on making  (or scourcing) these.


thanks alan

[phil (admin)]

Where there is a will, there is a way.

I'd imagine there would be a way to form one.

I wonder if there are any products, like those spun aluminum lamp shades, that could be modified.

[retired2]

i am having trouble finding bellmouth fittings in the uk (im in ireland). there are loads in the us but shiping such a delicate and bulky item is risky.
i am awaiting a price from a uk company but it will probably be astrinomial.

i am thinking of making one (i need 4, one for each seperater and one for the seperater in the dc unit, and one spare for a second dc unit that i havent bought yet but might need)

i am thinking of either spining it on my wood lathe (dangerous  with no experience like i have ) or using fiberglass and carbon fiber etc to mould it over a formaer i would turn on the lathe.

what do you think . will it work. are there any side affects to having a fiberglass etc part inside the seperater like this

any other ideas on making  (or scourcing) these.


thanks alan

It's the inside curve of the bell that makes it work, not the outside.  So, if you want to shape one by hand, I'd glue up some progressively larger donuts of mdf or some other material that can be worked with a file.  Once, you've got enough material to shape, take a coarse wood rasp and start rounding the inside curve.  Don't bother with the outside curve, it won't effect performance.  The finished product won't be pretty, and it will be a lot of work, but as you can see from one of the articles I posted almost any shape is much better than a stub end of straight pipe.  And I would think, even a crude bell mouth is better than most of the other shapes offered in the article.

Also, my thread on bell mouths has a link to some internet sites with some clever methods for making your own bellmouth.

[Contemporarycraft]

I have been reading the forum concerning the bell ends and air straightners.  Interesting work.  One post indicated that there may be more flo thru of fines with the bell end.   In addition to the current draw and CFM measurements, has anyone done anything to see what sort of fine separation these setups are capable of?  I recently built a setup that is essentially the top half of a cyclone (rectangle inlet and air ramp) but use the thien baffle where the cone would attach.  The blower is a 5hp grizzly with 13" impeller i got on craigs list. 9" inlet to the blower extending to within about 4" of the baffle.  The setup seems to work fairly well.  But i have no reference to judge separation quality.  Currently doesnt matter too much since im exhausting outside but id like to see how other systems work.  I know it gets table sugar quite well but whole wheat flour goes thru as I expected.  Im thinking to add the straightners but am sorta skeptical on the bell end if it hurts separation. 

[retired2]

I have been reading the forum concerning the bell ends and air straightners.  Interesting work.  One post indicated that there may be more flo thru of fines with the bell end.   In addition to the current draw and CFM measurements, has anyone done anything to see what sort of fine separation these setups are capable of?  I recently built a setup that is essentially the top half of a cyclone (rectangle inlet and air ramp) but use the thien baffle where the cone would attach.  The blower is a 5hp grizzly with 13" impeller i got on craigs list. 9" inlet to the blower extending to within about 4" of the baffle.  The setup seems to work fairly well.  But i have no reference to judge separation quality.  Currently doesnt matter too much since im exhausting outside but id like to see how other systems work.  I know it gets table sugar quite well but whole wheat flour goes thru as I expected.  Im thinking to add the straightners but am sorta skeptical on the bell end if it hurts separation.

I don't remember seeing the post you are referring to, but it might have just been speculation.  I haven't run a lot of fines through mine, but I haven't seen any indication that the bell mouth hurts or improves separation.

I'm not sure how many units have been built with bell mouths, but I don't think there are many. Maybe some one else who has built one can comment on the fines concern.

[Contemporarycraft]

Retired

Do you consider anything from a table saw as "fine"?  For instance i ripped some white oak as a test and did see some pass thru.  However in the trashcan, i did capture alot and scooped up some and dropped it back into the can to get a feel for how much of the capture would tend to want to stay airborne.  On the drop there was significant material that would float for a while.  Not very scientific I know. 

By the way I like your work.

[alan m]

welcome to the forum.
i  understand what you are saying  but im not sure. having a bellmouth should reduce turbulence and increase air speed (might suck more of the dust out of the stream). i remember phil stating that the more cfm throught the seperater the better the seperation  and lower bypass. i am going to try it and see what happens

[retired2]

Retired

Do you consider anything from a table saw as "fine"?  For instance i ripped some white oak as a test and did see some pass thru.  However in the trashcan, i did capture alot and scooped up some and dropped it back into the can to get a feel for how much of the capture would tend to want to stay airborne.  On the drop there was significant material that would float for a while.  Not very scientific I know. 

By the way I like your work.

I still don't have my radial arm saw hooked up to my DC, but I do have my bandsaw connected which is probably finer than the radial arm.  Not much of the band saw waste bypasses.  I think saw waste  can be granular or powdery depending on what you are cutting.  Oak should be granular, and should not bypass much.  MDF on the other hand is likely to be a real problem.

I haven't done enought testing to prove it, but I don't think the bell mouth has much bearing on separation other than it should improve CFM slightly, and that might in turn improve separation by a small anount.  In any case, all of these tweaks only make small improvements over the original design. 

[alan m]

i am thinking of making these by getting a 6" pipe and cutting along it up 1"+1/4 the diameter or a 2"circle
then cut a 12"circle from sheet metal and cut radiating lines out from the the center  leaving an 1" around the outside.

then make a former with a 6" hole in the middle and a 2"radius on the inside  edge. then bend the two pieces to the shave of the former.
isopon(car body filler, bondo i think its called in the us) the inside and outside (just for show) to smooth out the gaps between the bent pieces.

what do you think , will this work.

[retired2]

i am thinking of making these by getting a 6" pipe and cutting along it up 1"+1/4 the diameter or a 2"circle
then cut a 12"circle from sheet metal and cut radiating lines out from the the center  leaving an 1" around the outside.

then make a former with a 6" hole in the middle and a 2"radius on the inside  edge. then bend the two pieces to the shave of the former.
isopon(car body filler, bondo i think its called in the us) the inside and outside (just for show) to smooth out the gaps between the bent pieces.

what do you think , will this work.

It should work, the bell mouth is not subjected to any heavy stresses, and as I said earlier even a very crude one wii provide most of the benefits of a commercial one.

[Lake Lover]

I have been reading away at this site.  The bell mouth idea is interesting.  Do you have any pics to help me out ?

Thanks

[alan m]

if you search for retired2  build you will see his bell mouth

[retired2]

I have been reading away at this site.  The bell mouth idea is interesting.  Do you have any pics to help me out ?

Thanks

I'll save you the trouble of searching.  Here's two threads containing bell mouth info:

http://www.jpthien.com/smf/index.php?topic=563.0

http://www.jpthien.com/smf/index.php?topic=550.0