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# Compartment Innertubes

Have internal dividers
 (+2, -1) [vote for, against]

While riding along this morning, I noticed that the bottom of my tyre deforms due to the effects of my non-zero weight. Because of the rotation of the wheel, the deformation moves around the perimeter making the inner tube a sort of really-inefficient peristaltic pump <link> which squidges compressed air around in a futile loop.

Now. What if we built in compartments to the inner tube? Like bulkheads in a submarine, they could isolate sections in terms of pressure. In this way, air would not be pumped around in a circle. Also, the deformation at the bottom of a traditional tyre induces a small pressure increase in the whole tube. With compartments, the deformation would induce a much bigger relative volume change, causing larger relative pressure increase and proportionally less deformation. In effect, it would behave like it was inflated to a higher pressure.

To construct this tube, you could just have lots of little sections, each with their own valve. But having 32 valve holes in your wheel rim is undesirable, as is the tedious nature of inflating such a system*. So, construct a tube with bulkheads which are somewhat permeable to air. This would allow the compartments to equalize in terms of pressure with a slow** kinetic, but not fast enough to move the air around while riding. So, while riding along it would behave like the compartments were independent.

If there were 32 compartments, then the deformation in the lowermost compartment would be 32 fold higher*** relative to a traditional tube. This would lead to a... 5 ish? fold increase in compartment pressure and related reduced deformation. So while riding along you'd avoid pumping losses and it would feel like a harder tire. The faster you go, the more pronounced the effect.

Now, these compartments offer an additional opportunity. The bulkhead walls could contain small plastic pressure equalizing valves. These could be reed-valve based and be tuned to produce a musical note. Then, simply specify your inner tube in either "the birdy song" or "la cucaracha"****

*although the inherent puncture-resistance may pique the interest of cyclists deployed to tactical hot zones.

**as slow as possible to avoid pumping losses and to frustrate the person tasked with inflating it.

***sort of, I'd expect the bulkheads to bulge a bit.

****no other options.

 — bs0u0155, Jul 30 2014

Peristaltic Pump http://en.wikipedia...ki/Peristaltic_pump
[bs0u0155, Jul 30 2014]

tireballs - flat proof tire solution http://www.tireballs.com/pages/shop
[pashute, Jul 30 2014]

The whole point of a pneumatic tyre is that the entire tyre acts as the spring. Your solution would give a much harder ride.
 — pocmloc, Jul 30 2014

Harder ride for a given pressure. Just reduce the pressure a bit. Then you get to use thinner rubber, smaller valves and pump equipment.
 — bs0u0155, Jul 30 2014

 Even if the pressure is lower, you have massively shrunk the system that is giving your ‘spring’ from the whole wheel to the single section.

That's why a solid rubber tyre doesnt work so well, no matter how squidgy the rubber.
 — pocmloc, Jul 30 2014

Yeah, but imagine the fun of checking your tire pressure in twelve places !
 — normzone, Jul 30 2014

They make "solid" (tough foam rubber) inner-tubes for bicycle tires. Perhaps if the tires of a car were wider (more contact surface area with the ground for weight distribution), such could work for them, too.
 — Vernon, Jul 30 2014

 One of the biggest factors affecting riding effort is rotational mass of the wheels. You're suggesting putting additional valves, layers of inner tube, etc in there, which will increase that mass significantly. In that a hell of a lot of keen cyclers actually use tubeless tyres, I think you're going against trend here. Any gains in tyre work will be well lost by having heavier wheels (both in effort to get up to speed, and also sprung weight for suspension systems).

Also, I think you're vastly overestimating the "moving air around the tyre" peristaltic effect. This would only really come into play if the feformation of the tyre bottomed it out against the rim, causing some form of partial seal. I would contend that bike tyres usually deflect less than 30% into the rim, anyone wanting to have minimal drag will set pressure so deflection is much less than that. The actual drag effect comes from sidewall flex, that is flexing the sidewall rubber in and out is felt as rolling resistance, and of course higher tyre pressure reduces this.
 — Custardguts, Jul 30 2014

 It would be some entirely novel way to pump dairy products from one place to another.

 Not to mention the prime churning effect of all those sealed compartments.





Done! It's a Feta compli.
 — not_morrison_rm, Jul 30 2014

Ee, damn, you always get the best puns. Still, tons left.
 — pocmloc, Jul 31 2014

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