Bicycles

Bicycle inner tube pumps itself up as you ride

Bicycle inner tube pumps itsel...
The PumpTube is claimed to use wheel motion to draw air into itself
The PumpTube is claimed to use wheel motion to draw air into itself
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The PumpTube is claimed to use wheel motion to draw air into itself
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The PumpTube is claimed to use wheel motion to draw air into itself
A cut-away diagram of the system, in which the beige element represents the pumping mechanism
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A cut-away diagram of the system, in which the beige element represents the pumping mechanism

It was three years ago that we first heard about inventor Benjamin Krempel's PumpTire – it was a prototype bicycle tire that used wheel motion to keep itself inflated. While it was an interesting idea, it would require users to give up their existing tires, plus the peristaltic pumping mechanism would be compromised once the tread wore away. Well, he has now come up what sounds like a better alternative: the PumpTube.

Here's the general idea regarding how it works …

Air is drawn in from the atmosphere through a one-way valve, which sits in the valve stem. Instead of going directly into the inner tube, however, the air goes into one end of the tube-like pumping mechanism, which runs along the outside perimeter of the main inner tube. As the tire rolls against the ground, the pumping mechanism is compressed, forcing air into the inner tube. The resulting absence of air in the pumping mechanism creates a vacuum effect, drawing more air in through the valve.

That said, if the inner tube is already at its desired pressure (which can be set on a dial on the valve stem), no additional air is pulled in.

A cut-away diagram of the system, in which the beige element represents the pumping mechanism
A cut-away diagram of the system, in which the beige element represents the pumping mechanism

The idea behind the technology is that riders will no longer need to pump up their tires in order to compensate for seepage or pinhole leaks. While larger punctures may not have as much of an effect as they would otherwise, they'll still ultimately need to be patched.

Plans call for the first PumpTubes to be compatible with third-party 700c and 26-inch tires, and to retail for US$30 to $55 per unit. Krempel tells us that he hopes to launch a Kickstarter campaign sometime next year, once the design has been perfected.

Source: PumpTire

9 comments
Bob Stuart
I can't imagine much pressure differential being generated by the seal produced by the flexing of the contact patch. Tires support rims not through the air, but by the angle at which the sidewall meets the rim near the bottom.
Donald Vitez
A very interesting and useful invention worth perfecting. Benjamin, I encourage you to follow your dreams. Take all the criticism you receive and use it to refine your design.
Mirmillion
This reminds me of the possibility of using air pressure differentials to recover energy in hybrid and pure electric vehicles equipped with either tire pressure sensors or inflation/deflation systems. Like electric shock absorbers (proven to be able to add 5% to the range of electric vehicles), tires absorb lots of bumps and road variations as well as the deflection in shape (and, therefore, pressure) as they roll. I think this idea is a complete winner.
fb36
Nice idea but I think real solution is to invent a practical way to convert any kind of tire to airless tire. Maybe by replacing the air with Aerogel?
Paul Gracey
I've been waiting to see this idea refined to work with the tube inside. As Bob Stuart alludes, there is more flex to be had at the sidewalls. Relocate the mechanism and perhaps double it. Both schemes will have the diminishing returns problem as the flex is reduced upon reaching proper inflation and may never get there. I think this scheme's strength is in improving the abysmal rolling resistance of under inflated children's bikes making them less likely to abandon cycling.
Don Duncan
It might be practical, real life use, customers, will decide if it is worth the cost. I wouldn't invest, but I'm not emotionally invested as the inventor is.
The use of air as a shock absorber has been around for a long time, with leaking/loss of pressure a constant problem. I just bought an air pump/gauge that runs off my 12V to keep the tires at the correct pressure because it has been a headache every year when we take a long trip.
fb36: Astute observation. The need for a tire that doesn't rely on a gas as cushion is so obvious I wonder why no one has solved this problem.
Douglas Bennett Rogers
90% of my bicycle maintenance is pumping up tires! Was hoping to see a hollow fiberglass tire, even tried to make one! BMW had one in this magazine a while back. If this tube works, it may be just as good.
BG59
Great idea, but wouldn't it also work to just rig a small air pump with a cut out pressure switch to the chain or sprocket?
Hahaha! Never mind, I just looked down below.
xs400
Same as this: http://www.gizmag.com/goodyear-air-maintenance-technology-tires/24229/
But great idea!