DIY expansion chamber?

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by jjvsb, Jan 19, 2014.

  1. jjvsb

    jjvsb New Member

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    has anyone built or had any success building an expansion chamber from scratch?? I've made several attempts. After doing some research and using Gordon Jennings quick formula I managed to have created a pipe that works (without a doubt ) but havnt had any luck recreating it.
    would luv to hear from anyone who has attempted this.
    [​IMG]
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    Using a computer to print cone patterns makes the process MUCH easier. Simply trace the paper pattern onto your sheet metal and cut. I'm lazy though, I prefer using existing cones and fabricating the rest of the pipe to fit.
     
  3. Theon

    Theon New Member

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    I've made a couple of pipes that work quite well using 3" exhaust pipe and slotting Vee's into the length of the pipe squeezing it up and then welding, will have to get some photo's up, I plan to start a new one soon, and will have to take a few photos as I go.
    I'm new here and havn't worked out how to put images up yet.
     
  4. Toadmund

    Toadmund New Member

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    Sounds like a good idea!
    Since I am a man without a welder, my thoughts in the past were sheet metal and rivets.
    God! I need a (good, cheap) welder!
     
  5. Theon

    Theon New Member

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    [​IMG]
    [​IMG]
     

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    #5 Theon, Jan 20, 2014
    Last edited: Jan 21, 2014
  6. Theon

    Theon New Member

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    The purple bike will do about 70 Kph.
    The old Raleigh just hits 80 Kph at 9500 rpm on a 36 t.
     
  7. Theon

    Theon New Member

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    [​IMG]
    still having a few 'issues' with posting photos?
     
    #7 Theon, Jan 20, 2014
    Last edited: Jan 21, 2014
  8. Theon

    Theon New Member

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    I've got both the pipes off the bikes for finishing off.
    So here's a couple of photos.
    [​IMG]
    [​IMG]
     

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  9. jjvsb

    jjvsb New Member

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    wow all great advice.thanks!
    i hadn't thought of getting patterns..

    I went for the mathematical formula at first ,then realized how hard that would be..
    I work w/ sheet metal so getting the metal is easy.
    used 18g.. I have a forming smooth curves with it though.
     
  10. Theon

    Theon New Member

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    I made my own 'patterns', although not all that accurate.
    Just to get the shape.
    Then worked out the 'Trig' on the angles I wanted.
    measured the pipe, divided it into six, then cut Vee's of appropriate length to get 30mm to 76mm over that length. Simple really, then squeezed it all up, with a bit of a tap here and there.
    and welded with an inverter stick welder.
    The pipe with the stinger exiting the belly is noticeably quieter,
    but I can't comment on it's performance difference as both pipes are totally different.
    As is the exhaust port timming on the motors.
     
  11. ken murphy

    ken murphy New Member

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    I make all my pipes, I use the stock pipe or pit bit pipe seems to work.
     

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  12. Powertool

    Powertool Member

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  13. Theon

    Theon New Member

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    [​IMG]
    [​IMG]
    I gave my pipes a bit of a tidy up today, but something died in my Shipping container/ welding Shed.
    And I have a few slag intrusions that should be fixed before painting, there's better light and less fumes outside though.
    My 'Over the top' pipe needs a heat shield for the knee, it's burnt my mate also.
    The header pipe for that one is salvaged from an old scooter and has a nice divergent angle. It was really a total experiment, with little math's and a bit of research, but again mostly about making something that fitted nicely.
    I am however Quite happy with it's performance, although not really experienced enough to say that it is ideal.
    For most engines/bikes/riders, a bit more header pipe?
    That bike/motor (The Old Raleigh) has had a recent pull down/ upgrage also,
    But does not have adequate brakes for 50MPH!
    So Is possibly going to get parted out, and the remains hung on the wall?
    Otherwise It needs Twin Discs!
     

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