stealth bike

Discussion in 'Photos & Bicycle Builds' started by rockbass, Feb 13, 2011.

  1. rockbass

    rockbass New Member

    motor in a plastic milkcrate, shag carpet for sound adsorption, added off the shelf muffler

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  2. Dave C

    Dave C Member

    That's a scream, very clever idea. Does it overheat?
  3. jaguar

    jaguar Well-Known Member

    Too too cool!
    Can you hear it 20 ft away?
  4. rockbass

    rockbass New Member

    just went around the block -seems okay. added muffler - takes out sharpness of the exhaust sound but still can hear it. not sure how much the carpet helps. attached picture shows milkcrate is open top & bottom, also partially open front & back, think this should be enough for adequate air flow. used existing carburator inlet, turned 180 deg. & epoxyied on a 45 deg 5/8" copper street elbow. exhaust has 90 deg 3/4" copper elbow brazed at exit flange. motor is rubber mounted on rack but my test run showed serious vibration at mid range speed. added dual brake lever - work great.

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  5. professor

    professor Active Member

    I think there is a post somewhere here about quietiing the HT.
    Adding deadening material to the clutch cover, a sound extension /box? to the intake, rubber bits between the fins.
    I have found the more mufflers and legnth -the quieter the sound.

    See if you can bolt the engind down solid, this should help lower the vibes.

    You may be able to delete the carpet material for cross cooling when the snow goes away, after all, the black engine will be difficult to see.
  6. lowracer

    lowracer Member

    I like it!
    I may need to do something like this to avoid getting pulled over.
    Thanks for sharing
  7. rockbass

    rockbass New Member

    appearance is everything,
    plan to add a rear view mirror for smokey detector.
    always where a helmut, stay under 30 kph and should not attract attention.
  8. Htown

    Htown Member

    Killer. I was thinking you might be able to use some of the negative noise technology that is employed in loud offices. I think it would work for noise with a constant pitch.
    Last edited: Feb 14, 2011
  9. motorpsycho

    motorpsycho Active Member

    ha ha, let the engine get good & hot, and i bet that carpet goes up in smoke.
    the exhaust is actually touching the carpet, and that pipe can and will get up to 250 degrees F. if not more.
    I don't think you will have enough air flow to keep the engine cool because these things get pretty darn hot, and with the gas tank being right on top of the engine, I would not be surprised if the engine gets vapor lock from the heat.
  10. Htown

    Htown Member

    I am pretty sure the milk crate is perforated enough so as to get enough airflow, I would think using a hood liner material might be better choice of sound deadening materials.
  11. motorpsycho

    motorpsycho Active Member

    Maybe, but the perforations are mostly blocked by the carpet. The fins on the cylinder and the head are where the air flow needs to be concentrated.
    In the pics. it appears that the fins are not exposed enough for adequate cooling. Even if you have the top and bottom of the crate open, air will not be directed towards the fins on the head and the cylinder.
    Just my opinion, but I wouldn't have done it this way.

    You shouldn't block air flow from getting to the head and the cylinder fins.
    This is why these engines are called air cooled.

    With the gas tank sitting right on top of the cylinder, 100% of the heat from the head will be transferred to the gas tank. This will heat up the gas and cause it to turn into a vapor before it gets into the carb.
    This is known as vapor lock, and an engine will stop running when this happens.
    even with a fully exposed engine, if you sit still and let it idle for a ferw minutes, it gets hot really fast.
    You need as much air flow across the cylinder and head fins as possible.
    I'm not saying that this will cause your engine to explode, but it might shorten it's life span.
    heat is the # 1 enemy on an air cooled engine.
    Last edited: Feb 15, 2011
  12. namefail

    namefail New Member

    Great idea. I have similar plans for a trike project I'm working on. Maybe throw some exhaust wrap around it if it gets to hot? I wouldnt really worry about it tho. youll be able to judge for yourself.