On 2007-08-21, verb <
[email protected]> wrote:
>
> "20cents" <[email protected]> wrote in message
> news:[email protected]...
>> In article <[email protected]>,
>> "verb" <[email protected]> wrote:
>>
>>> Has anyone ever heard about a monocoque bicycle and
>>> why they are not mass produced?
>>>
>>> ie two halves of pressed metal mig or tig welded
^^^^^^^^^^^^^^^
>>> together by a robot.
>>>
>>>
>>> Wouldn't this be cheaper than handbuilt bikes?
>>
>> I thought that CF time trial bikes were monocoque. Yes, no?
>>
>> cheers,
>> Darryl
>
> Some are, that's true.
>
> CF bikes are still expensive to make though.
> I was wondering why metal monocoque bikes are not made,
> since it would appear to be a cheap way of making bikes.
Pressed metal is a **** structual material, pop into your local bicycle
reuse/recycle centre and have a look at a set of pressed metal canti's
from a cheap MTB or a kiddies bike.
The side of the canti which holds the solid cable end on most of the
will be distorted out of shape. I once squeezed a brake lever on one of
these hard enough to straigten the hook and pop out the cable.
Even given some unobtainium stuctual grade pressed metal, unless the
join was perfect across the entire length of the bike, particularly the
corners the frame would seperate quite quickly. Have a look at a cheap
pressed and rolled mop handle or curtain rod for an example of this.
For a 56cm frame you would need approximately 7 meters of perfect joins.
Including a lot of very tight corners with poor clearances. I don't know
of any machine which could do this. (there is probably a reason why a
good welder can get employment making high presure vessels)
I think its not done 'cause its not possible to make a cheap and
reliable frame this way
--
Human Powered Cycles | High quality servicing and repairs
[email protected] | Affordable second hand bikes
(03) 9029 6504 | Bicycle reuse centre
www.humanpowered.com.au | Mechanical and on-road training and instruction
