Frame weak-points?

Discussion in 'Cycling Equipment' started by Trentus, Jan 23, 2003.

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  1. Trentus

    Trentus Guest

    I have a Merida bike with "Shotgun technology" frame. The cross bar, and the diagonal bar down to
    the pedals (downtube?) have been built around an alloy "double barrel shotgun" type of tubing for
    extra strengthening. In other words two tubes side-by-side are in the middle of the cross bar,
    and downtube.

    http://www.merida-bikes.com/mou-19.htm

    What intriques me about this, is the triangle of tubes comprising the tube from the seat post down
    to the pedals, and the tubes from the pedals back to the actual wheel, and from the wheel back up to
    near the seat, are all very thin normal tubes without this "double barrel shotgun" reinforcing
    within the tubes.

    Yet my totally ignorant impression would be that in almost any stressed situation such as a landing
    from even a small jump, would put the forces on this rear "triangle" rather than on the crossbar,
    and downtube.

    It seems to me that the wrong tubes are reinforced

    What parts of a frame fail most often, and where should they be reinforced.

    TIA

    Trentus
     
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  2. Gizmomaker

    Gizmomaker Guest

    Trentus wrote:

    > I have a Merida bike with "Shotgun technology" frame. The cross bar, and the diagonal bar down to
    > the pedals (downtube?) have been built around an alloy "double barrel shotgun" type of tubing for
    > extra strengthening. In other words two tubes side-by-side are in the middle of the cross bar, and
    > downtube.

    Yes it seems the strengthening is in the wrong place. I saw a courier screaming down a city street
    on a nice new one of these yesterday. He did a right angle turn in front of a fast approaching bus
    with just metres to spare. Before he could straighten up he was heading right at the high/sharp
    curb. My heart sank. Without any sign of lifting the front, or moving his body or the bike in anyway
    at all, he rode over it as if it was just flat pavement. Should I try this at home?
     
  3. Randomchris

    Randomchris Guest

    I thought that the rear triangle was a tetrahedron (??), which is one of the strongest structures
    known to man! That's why you can get away with narrower tubes. The main triangle is just that - a
    triangle - and is typically much longer than the rear triangle and is more likely to twist and flex.

    Trentus <[email protected]> wrote in message
    news:eek:[email protected]...
    > I have a Merida bike with "Shotgun technology" frame. The cross bar, and the diagonal bar down to
    > the pedals (downtube?) have
    been
    > built around an alloy "double barrel shotgun" type of tubing for extra strengthening. In other
    > words two tubes side-by-side are in the middle of the cross bar, and downtube.
    >
    > http://www.merida-bikes.com/mou-19.htm
    >
    > What intriques me about this, is the triangle of tubes comprising the tube from the seat post down
    > to the pedals, and the tubes from the pedals back
    to
    > the actual wheel, and from the wheel back up to near the seat, are all
    very
    > thin normal tubes without this "double barrel shotgun" reinforcing within the tubes.
    >
    > Yet my totally ignorant impression would be that in almost any stressed situation such as a
    > landing from even a small jump, would put the forces
    on
    > this rear "triangle" rather than on the crossbar, and downtube.
    >
    > It seems to me that the wrong tubes are reinforced
    >
    > What parts of a frame fail most often, and where should they be
    reinforced.
    >
    > TIA
    >
    > Trentus
     
  4. Trentus

    Trentus Guest

    "Phil Holman" <[email protected]> wrote in message
    news:[email protected]... <snip>
    > > What parts of a frame fail most often, and where should they be
    reinforced.
    >
    > 1. The chainstay to dropout attachment on the drive side.
    > 2. Chain stay to BB shell.
    > 4. Seat tube to BB shell
    > 3. Headtube attachment to downtube.

    Anyone know a URL, or other easily found source, that names all the parts of a bike? As you may have
    noted from my "descriptions" rather than technical terms for the various tubes on a bike, I don't
    know much more than the obvious "seat", "wheel", "handlebars" etc. What's a chainstay, and where is
    it.? What's a "dropout" a "dropout attachment" and where are they? What's a BB shell? (I can assume
    a BB is a Ball Bearing) The seat tube, I assume is the tube down from seat to pedals. Headtube? (I
    assume this is the tube that the steering goes through from handlebars to front forks.)

    I'd love to know the technical terms for a lot more of the parts on my bike, if only so I can ask a
    question and know I'm not causing confusion, or getting a wrong answer, because my description was
    misunderstood.

    TIA Trentus
     
  5. Almost Fast

    Almost Fast Guest

    http://www.sheldonbrown.com/glossary.html

    "Trentus" <[email protected]> wrote in message
    news:<[email protected]>...
    > "Phil Holman" <[email protected]> wrote in message
    > news:[email protected]... <snip>
    > > > What parts of a frame fail most often, and where should they be
    > reinforced.
    > >
    > > 1. The chainstay to dropout attachment on the drive side.
    > > 2. Chain stay to BB shell.
    > > 4. Seat tube to BB shell
    > > 3. Headtube attachment to downtube.
    >
    > Anyone know a URL, or other easily found source, that names all the parts of a bike? As you may
    > have noted from my "descriptions" rather than technical terms for the various tubes on a bike, I
    > don't know much more than the obvious "seat", "wheel", "handlebars" etc. What's a chainstay, and
    > where is it.? What's a "dropout" a "dropout attachment" and where are they? What's a BB shell?
    > (I can assume a BB is a Ball Bearing) The seat tube, I assume is the tube down from seat to
    > pedals. Headtube? (I assume this is the tube that the steering goes through from handlebars to
    > front forks.)
    >
    > I'd love to know the technical terms for a lot more of the parts on my bike, if only so I can ask
    > a question and know I'm not causing confusion, or getting a wrong answer, because my description
    > was misunderstood.
    >
    > TIA Trentus
     
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