Made an expansion chamber tonight!

Discussion in 'Performance Mods' started by Skyhawk66, Nov 5, 2014.

  1. Skyhawk66

    Skyhawk66 New Member

    I'm not quite done with it yet, I need to figure out my stinger. I'm not sure if I want a belly stinger, a rear stinger, or just put a lawnmower style muffler on the end.. What do you guys think would be the best stinger for the performance end, not so much aesthetics?

    I have a fear the header may be too long, and will kill my top end, but I guess we'll see once I ride it after my stinger is put on.

    What are your guys thoughts on it?? I have thick skin and can handle honest criticizim..
     

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  2. Skyhawk66

    Skyhawk66 New Member

    41 views and not one person can voice any advise??? I guess you need a screen name like jaguar, headsmess, or Fabian to get any advise here... I was hoping to this would be a decent forum, apparently not...
     
  3. Robot

    Robot New Member

    RE: OK,good start

    Not bad, could be closer to parallel on the line but not bad..
     

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  4. Robot

    Robot New Member

    Again work begins today ~1939 ZEP original, slow start will finish in a week or two likely..
     
  5. dirtwarrior

    dirtwarrior Member

    I like the design. I goes with the bike well
     
  6. Robot

    Robot New Member

    Setting the ZEP with 3 speed Nexus front an bake brake combo with stainless wheel set ,66 cc and CDI ,jack shaft performance ,carb small expansion chamber Trek fork suspension Continental Speed King .Again slow to start slow to finish..
     
  7. Robot

    Robot New Member

    Anyone knowing this bike frame maybe you can identify it better than I did.
     
  8. jaguar

    jaguar Well-Known Member

    yeah that long header will result in only low end power without the ability to rev out.
    the belly stinger actually gives best performance when low end power is important.
     
  9. Skyhawk66

    Skyhawk66 New Member

    Will the long header work ok with the extended offset intake manifold I have? Any way to make it rev with a long header?
     
  10. Robot

    Robot New Member

    Just started on this it's not really that interesting has not got off the ground yet but anyone looking into this bicycle frame will be well advised.
    I've got a slow start frame been out the closet only an hour or two for finish and rough hardware that had to be made by hand. It is one of the best 18'' steel bike frames around in my opinion and the original is extremely rare from what I've seen. Actually seen two or three only one I've seen with the 50mm bottom bracket is the one I feature but the frame can be found with the smaller bracket in the later Ward version of the 1940's I believe this one a 1939 or earlier. And no I'm not in need of advice the assembly is straight forward the parts on the jackshaft are aluminum and forged steel the aluminum must be greased fitted unfitted refitted before assembly.Those pieces are fine thread and are very difficult to assemble it must be done with the greatest of care hope to get a camera set up in a few days got one that will not format for some reason and I can't get it on line currently I'm looking into a fix. I'd mentioned two weeks to reach completion I'll get a video up sooner or later with some progress. When complete this bike should be competitive with most without turning a 1 piece crankshaft two piece connecting rod out of a pure platinum billet . But IF I'M Pushed it will go pure platinum end to end inside and out..
     
  11. Skyhawk66

    Skyhawk66 New Member

    Robot, what does any of that have to do with my exhaust question???
     
  12. jaguar

    jaguar Well-Known Member

    the longer the header, the more limited in rpm the engine is.
    you will just have to try it and see how it is. it may not be too bad.
    but without a belly stinger it will be LOUD.
    my advice is to cut the belly length in half, put a baffle on thats 50% longer (for a wider powerband), and insert the stinger till it starts at the end of the belly section.
     
  13. Skyhawk66

    Skyhawk66 New Member

    It is extremely LOUD! Too loud... The belly section is 3" diameter, and roughly 4" long. If I'm understanding you correctly I need to make the belly about 2" long??? And do I need to make the cone on the back of the belly 50% longer?? I'm trying to make sure I understand what you think will work best for it.

    I did test fire it, and besides being extremely loud, it definitely doesn't rev up like it used to... It's been raining like crazy here, so I haven't been able to test it out for torquiness. I'm hoping it'll pull hills better, since I only have a 32 tooth on it, but I don't want to lose my 35 mph either.
     
  14. jaguar

    jaguar Well-Known Member

    yes you understood me right.
    the sad fact about expansion chambers is that they only enhance power within their powerband (typically a 2000 rpm range) and will stop any rpm increase beyond a bit more than the top of their powerband. And when the baffle angle is steep (like yours) it robs power before you rev up into the powerband.
    For a single speed ride the baffle cone (the last one) should have a very slight angle for a wide powerband thast doesn't rob power below the powerband.
    2 or 2.5 inches is the normal max belly diameter for these engines.
    If you want to be precise in your design then just download my Excel file of Expansion Chamber Calculator (ECcalc) and make good use of it.
     
  15. Skyhawk66

    Skyhawk66 New Member

    Ok thank you very much! I will test it the way it is, and if it needs changed I'll drop the diameter of the belly, and lessen the angle on the baffle cone. Thanks again.
     
  16. Skyhawk66

    Skyhawk66 New Member

    Update. I installed the stinger, I used a lawnmower muffler, and added a belly stinger to it. I took some conduit and measured it so it would start at about the middle of the belly. Then welded that to the lawnmower muffler, then welded that mess to the expansion chamber. It is actually very reasonable with the sound level, it revs pretty decent, and HOLY $HIT did it give this thing some bottom end!!!! I can start off from a dead stop under engine power, without pedaling WITH A 32 TOOTH sprocket!! I love it! And I did it all myself, with the help of this forum! Thanks guys!
     

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  17. Zen builder

    Zen builder Member

    Skyhawk, I think it's a great forum . But, you have to remember, that not everyone that visits a post can give GOOD advice. We are all here because we enjoy building and riding. Some are old pro's, and some because we are new and what to read as much as we can, as some day we may need the references. Immersed with what I have seen of your build, not everyone has the tools and where-with-all that you do. Keep posting.
     
  18. Fly1

    Fly1 Member

    I think it is great you are trying.I have built a few pipes, but to make one right you do indeed to do
    the math.I remember in my kart racing days, a few guy making pipes that did work very well, but
    just looking at them I would think no way.

    As far as stingers, some thing I have not seen with these bike pipes.Our pipes used cans welded to
    the rear & closed except for a hole cut in the side to let presser out.It reduced noise, & worked very
    well.

    I,m going to build a pipe in the next few weeks, after I finish my bike & break the engine in.I will
    post a pic as to how I did it.

    Fly
     
  19. HeadSmess

    HeadSmess Well-Known Member

    bit like how i cut the end of the stock muffler and use the can here?

    yep. works a treat.:)
     

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