How about an inner tube that you never have to pump up? - Page 1
Forum section: electronics / projects

author: mazzic518
author_rank: Newbie
timestamp: December 20, 2015, 07:59:54 pm
content: I'll believe it when I see it...http://www.bikeradar.com/commuting/news/article/this-self-inflating-inner-tube-is-making-the-impossible-possible-apparently-45944/

author: ataradov
author_rank: Super Contributor
timestamp: December 20, 2015, 08:28:09 pm
content: The concept is OK on its surface. But I'm not sure how reliable it will be. But it seems like with enough effort and optimizations, it should be doable.

author: wblock
author_rank: Regular Contributor
timestamp: December 20, 2015, 09:01:32 pm
content: It can certainly be made to work. The biggest problem is that it gets its energy from the effort the rider has put into making the bike go forward. Well, that and the fact that the problem it solves is not really a problem.The pump will divert energy on each wheel rotation. They say the tire pressure is adjustable with the valve. Sounds like it does not adjust the pump to stop sucking energy at a certain pressure, it just throws away that energy by letting any extra pressure out the valve...One place it might be useful is when discovering a flat before a ride or after a stop. Except that when the tire is flat, you can't ride it to pump it up.If an automatic pump is necessary, why not just run it mechanically off the drivetrain? Almost certainly more efficient that squeezing stretchy things, and you could have a lever or something to disengage it the 99% of the time it is not needed.

author: ataradov
author_rank: Super Contributor
timestamp: December 20, 2015, 09:06:22 pm
content: Quote from: wblock on December 20, 2015, 09:01:32 pmThe article is not clear, but I would assume that it is a self-regulating system. Basically if tire is deflated and deformation is high, then it pumps. Once tire is inflated and deformation is low, it stops pumping. So when you do the adjustment, you are adjusting allowed deformation level, not the actual pressure.Some of the energy will be wasted, of course, but it would be minimal an I doubt anyone will ever notice it.Edit: This does create a problem of over-inflation. Small bumps on the road will create higher apparent deformation. So yeah, there is some thinking to do there.

author: wblock
author_rank: Regular Contributor
timestamp: December 20, 2015, 09:49:13 pm
content: Quote from: ataradov on December 20, 2015, 09:06:22 pmRolling resistance is already the holy grail of bike tires, and commuters already pay a price in that regard with tougher tires and generators for lights. It might not be as bad as solid foam no-flat inner tubes, but given that this system is probably not very efficient, I'd expect it to be easily noticeable. Hard to test, since I'm fairly sure neither of us will ever own one of these tubes.QuoteWell, like you suggested earlier, a sufficiently inflated tire would (in theory) not activate the pump at all. Below that pressure, the pump loses efficiency because the sidewalls are too floppy. Above that pressure, it also loses efficiency because the sidewalls are too stiff to flex. So it seems like if the pressure gets too low, you're going to need a pump. Too high, best case it just makes for extra dead weight in the wheel. Or it keeps pumping, but since it is unlikely to be at or beyond the highest pressure it can generate, the energy is just turned to heat in the pump.Let me revise my first statement: they can certainly pump some air from tire deformation in specific conditions. Making it keep a tire usefully inflated, maybe. Doing so without making serious compromises in rolling resistance, materials, weight, and cost? We'll see.