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Thread: Carburetor Bell Mouth Design

  1. #11
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    You'll never get a pic of the process in action as it was snuck in at my local engineering co....I was told that if I injured myself doing it on their press, I'd be slung out on the road and they'd call it in as a road accident...Bloody OSH, spoiling all the fun.

  2. #12
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    Press forms for 2 sizes of bellmouth and a couple of samples. Forms are just turned up from scrap mild steel. The shape and form of the taper can be whatever you prefer.
    It would in theory be possible to actually do a roll on the outer edge of the bell, I've made a form for that on steel silencer ends way back. As what i'm using is 6061 in T6 condition, I'd doubt if it would form that much without annealing - which i've not found necessary yet.
    The disadvantage of using tube for the raw material is of course finding the correct size...The last lot was particularly hard as i could have bought a 5m stick but not the small quantity I wanted. Solution - ask the wholesalers who they last supplied and go beg an offcut.
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  3. #13
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    That's awesome, and damn they come out nice.

    One thing that article I posted at the beginning mentions is that a considerable portion of the air coming into the opening is from the surrounding atmosphere - not so much that directly in front of the opening. Which is why bell mouths have flairs, but it advises that the edge of the opening be folded right back on itself 180 deg. Having said that, I've hardly ever seen proper racing carbs with full 180 deg of flaring on the openings, material and space constraints I guess...

    Next thing I want to look into is a Velocity Stack to get a bit of Ram effect happening. Might try sticking the opening I've got onto the end on a tapered bit of tube and see how that goes. Not much point 'till I get the cams re-profiled tho...

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    Brendan (24-09-2016)

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