# Bicycle Mechanics - Helium filled tubes

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View Full Version : Helium filled tubes

john_dun
08-18-02, 06:32 PM
Is it possible to fill the tubes with helium to reduce weight?

08-18-02, 06:41 PM
Almost anything is possible, but since a standard cubic foot of air weighs something like 0.0745 pounds, this is probably not a very viable weight savings.

Editted to move decimal from .00745 to .0745

caloso
08-18-02, 06:58 PM
I'd guess that you'd have to pump them up more often too because He is such a small molecule compared to the N2 and O2 molecules that make up most of the volume of garden variety air.

Raiyn
08-18-02, 09:49 PM
Not with normal tubes as stated above a helium atom is much smaller than a CO2 molecule or other "air" molecule. Helium would (slowly) pass straight through your tube. It would be kind of like a helium balloon which eventually loses pressure and sinks back to earth. I understand where this i s coming from however, If you calculate the energy requirement to set a bike/wheel system in motion, you'll find that the wheels need more energy per unit mass than the frame and rider do. Exactly how much more depends on the mass and moments of inertia of the components. This effect leads to the cyclists' rule of thumb: "A pound off the wheels is worth two off the frame," which is calculated by analyzing the wheels as homogeneous disks. Using an approximate tube volume of about 690 cm3 and a pressure of 125 psig, I calculate a weight savings of about 7 grams. For typical performance road racing tire, tube, and hub/wheel weights of 250, 70, and 1200 g, respectively, using helium makes the wheel assembly about half a percent lighter. Lighter wheels, even slightly lighter wheels, can be significant but this isn't a good way to make them lighter.
:beer:

usnagent007
08-19-02, 12:12 AM
helium-filled aerodynamic bladders as an alternative? now there is a bizarre idea... helium-filled frames even? Imagine an injection port for helium... it's only green tea that I'm drinking

khuon
08-19-02, 12:47 AM
Originally posted by usnagent007
helium-filled aerodynamic bladders as an alternative? now there is a bizarre idea... helium-filled frames even? Imagine an injection port for helium... it's only green tea that I'm drinking

A company actually did a helium-filled frame. I remember reading about it in Mountain Bike Action in the early 90s. The thing is... just decreasing weight doesn't necessarily imply decreased mass. Helium would just make the bike more bouyant. I'm not sure it would make all that much a difference.

es_seattle
08-19-02, 01:26 PM
I used to ride a bit with a former pro BMX'er (what a pain in the butt to MTB with); and he said a few guys on the circuit put helium in their tires. He didn't, however, have any info on whether it actually helped.

Jeepbikerun
08-19-02, 03:38 PM
Originally posted by Raiyn
Not with normal tubes as stated above a helium atom is much smaller than a CO2 molecule or other "air" molecule. Helium would (slowly) pass straight through your tube. It would be kind of like a helium balloon which eventually loses pressure and sinks back to earth. I understand where this i s coming from however, If you calculate the energy requirement to set a bike/wheel system in motion, you'll find that the wheels need more energy per unit mass than the frame and rider do. Exactly how much more depends on the mass and moments of inertia of the components. This effect leads to the cyclists' rule of thumb: "A pound off the wheels is worth two off the frame," which is calculated by analyzing the wheels as homogeneous disks. Using an approximate tube volume of about 690 cm3 and a pressure of 125 psig, I calculate a weight savings of about 7 grams. For typical performance road racing tire, tube, and hub/wheel weights of 250, 70, and 1200 g, respectively, using helium makes the wheel assembly about half a percent lighter. Lighter wheels, even slightly lighter wheels, can be significant but this isn't a good way to make them lighter.
:beer:

caloso
08-19-02, 07:25 PM
What about the opposite? What if you filled your tires with a really heavy gas like xenon? Then you'd have a super stable gyroscope! (Oops. I think I've drifted into the wrong thread. ;) )

John E
08-19-02, 08:20 PM
An H2 molecule weighs half as much as an He atom/molecule. Let's go for another couple of grams and fill our tubes with hydrogen, to get a bang out of life.

Bokkie
08-20-02, 01:45 AM
Forget the Xenon, Helium thing. Go for oxygen. That way, if you get a flat and can get to the tube quick enough before it all vents, you can at least get a quick oxygen boost in your lungs. That'll mean you be able to change the tube faster, and have enough spare capacity in your lungs to blow it back in. If you eat something 'volatile' the night before, you can probably top up with some methane. On the second flat, repeat the exercise and light a match when you exhale. That'll impress everyone.:rolleyes:

khuon
08-20-02, 03:16 AM
Originally posted by Bokkie
Forget the Xenon, Helium thing. Go for oxygen.

Taking a queue from the 4x4ing crowd, why not seal off and tap the frame with a valve to allow you to store compressed gas in the frame (yes, I know this will make it heavier) so you can use it to refill tyres in emergencies? No longer will you need to carry a mini-pump or CO2 inflator. They sell special bumpers for Jeeps that double as compressed gas canisters for airing up tyres after finishing a trail run.

Bokkie
08-20-02, 03:21 AM
Taking a queue from the 4x4ing crowd, why not seal off...

I'm going to be serious here! What you mention about 4x4 vehicles got me thinking about those vehicles that have tire pressures you can adjust from the cab. I've always wanted to know, just how do you adjust your tire pressure without getting out of the vehicle and messing around with the valve? Can someone explain how it works mechanically? I think the US HumVee was one of the first to use it?

khuon
08-20-02, 03:32 AM
Originally posted by Bokkie

I'm going to be serious here! What you mention about 4x4 vehicles got me thinking about those vehicles that have tire pressures you can adjust from the cab. I've always wanted to know, just how do you adjust your tire pressure without getting out of the vehicle and messing around with the valve? Can someone explain how it works mechanically? I think the US HumVee was one of the first to use it?

Center Tyre Inflation System (CTIS) uses hoses connected up to each rim which are specially equipped with rotating seals and whatnots. Ask any Hummer/HMMWV owner/mechanic and they'll tell you these are very expensive rims and also extremely heavy. The tyres are also run-flat so luckily you don't have to change the tyres out in the field.... or if you do, better hope for some mechanical assistance. Of course the entire wheel area of a Hummer is expensive and complex... with hose dropped hubs and all. They're one of the very few truly ofroad vehicles to make independent suspension work effectively and reliably (well... that may be questionable).

poululla
08-20-02, 03:48 AM
The 1984 US Olympic track team filled their pursuit bikes wheels with helium.

Bokkie
08-20-02, 06:43 AM
The 1984 US Olympic track team filled their pursuit bikes wheels with helium.

From what we've seen previously, it does not look like He offers any noticeable weight saving, unless maybe I missed something else?

If the weight saving is negligible, does this not put it in the same league as those riders who wear those tapes across the bridge of the nose, supposedly to facilitate breathing. I mean, there is no better way to breathe in quantity than through the mouth. Through the nose is fine if you are fairly quiscient, but under normal riding stress I don't think you could breathe fast enough through the nose?

Does Helium=Nose tape=DiddleySquat benefit?

poululla
08-20-02, 06:48 AM
I wondered about your forum name...Bokkie....and then I saw "lekker jol" Your nationality is now known.... ha ha ha!!! :D :D

Zog
08-29-02, 09:00 AM
Yes.
But then you'd have to keep your bike tethered to the ground!

Buddha Knuckle
08-30-02, 12:26 PM
Nose tape=DiddleySquat benefit?

"Breath in through your nose, out through your mouth" - That's the mantra all high-school track and cross-country athletes learn. Breathing through your nose improves ventilation...somehow. No point in looking it up because it is common knowledge. The breathe right strips have a dramatic effect on some folks, but not on others - it all depends on the anatomy of your naso-pharynx. The strips are often a first line treatment for obstructive sleep apnea (yes, it's true, snoring can kill).

BK

khuon
08-30-02, 12:29 PM
Originally posted by Buddha Knuckle

The breathe right strips have a dramatic effect on some folks, but not on others - it all depends on the anatomy of your naso-pharynx.

What if I adjust the nosepads of my sunglasses just right... :fun:

MisterJ
08-30-02, 12:43 PM
I know that snoring can kill the snorer. My wife has threatened to strangle me many times.

:)

RainmanP
08-30-02, 01:26 PM
Oh, man, and if you wear the nose strips while cycling you just more than offset all the weight savings from filling your tubes with helium. Is there not end to the choices we must make?

pat5319
08-31-02, 01:54 AM
Helium? Pfffft!!

Ride Simply
Pat