Evacuated Frame Tubes: Stronger and Lighter

[Mark Hickey]

Benjamin Weiner <[email protected]> wrote:

>David L. Johnson <[email protected]> wrote:

>> Hydrogen comes as a molecule, two atoms stuck together with something akin to tubular glue.
>
>Indeed - like tubular glue, it certainly leaves quite a mess when you try to separate it.

Sure does, though it makes for some awesome film clips.

>On the subject of evacuated frame tubes, the traditional
>r.b.t. response for efficient weight savings is to suggest evacuating before a ride.

It strikes me that it's pure folly to try to pump the air out of a bike frame. Why, there's at least
2-3 times as much air in your lungs as in your bike frame, so I think a more sensible solution would
be to learn to ride taking quick, shallow breaths. After all, the air in your lungs weighs just as
much per liter as the air in your bike frame
- the less air in your lungs, the faster you'll ride - right?

In fact, if my calculations are correct, I should be able to take 32 seconds off my TT by totally
exhaling before the race and then not breathing in for the duration of the event. I figure not only
will this make me significantly lighter, but it will reduce my cross-sectional area and aerodynamic
drag as a result.

I've had a few problems testing this technique, but hope to perfect it before the AZ state
championships. I'm working out some odd geometry problem with the bike - it seems it won't stay on
the course for more than a minute or two without getting all wobbly and falling over.

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame

 

[Andy Dingley]

On 23 Apr 2003 14:18:04 -0700, [email protected] (Matt J) wrote:

>I've always wondered why they fill the tire cartrages with CO2. It's more dense than air, so it
>adds weight to your expensive lightweight wheels where it counts most - the outside.

CO2 dissolves in water to form soda water, so there's a long history of making small disposable
cylinders of it. Those flashy new tyre cartridges are just the same old Sparklets bulbs.

There's also the question of "triple point". Although I don't think any tyre inflater cylinders use
this, it's possible to liquify CO2 at room temperature, just by compressing it (For many gases, its
impossible to do this, no matter how hard you compress it). This lets you store a large volume
(liquids are much denser) in a small volume and a relatively simple storage cylinder.

 

[David L. Johnso]

On Tue, 29 Apr 2003 11:42:12 +0100, Andy Dingley wrote:

> On 23 Apr 2003 14:18:04 -0700, [email protected] (Matt J) wrote:
>
>>I've always wondered why they fill the tire cartrages with CO2. It's more dense than air, so it
>>adds weight to your expensive lightweight wheels where it counts most - the outside.

1) It's a fraction of a gram

2) Those cartreidges were meant for shooting b-b guns. They had to be cheap. It is very easy to get
compressed CO2, since it liquifies at a moderate pressure.

--

David L. Johnson

__o | What is objectionable, and what is dangerous about extremists is _`\(,_ | not that they are
extreme, but that they are intolerant. (_)/ (_) | --Robert F. Kennedy