A pneumatic tire uses all of the air in the whole tube as a shock absorber, while foam-type “airless” tires/tubes only use the air in the immediate area of impact.
This makes no sense to me. All that matters is how much the tire deforms from an impact, and at what speed. Using “all the air” isn’t some magical benefit. Ultimately it’s the rubber of the tire that has to deform to absorb the shock. It’s good that there is air behind it because solid rubber wouldn’t deform properly and the fact that air compresses means the rubber will deform deeply. There’s nothing saying a properly engineered foam wouldn’t behave exactly as well.
The cells of the foam are all touching each other. Shock will propogate from the are of impact and travel through the entire tire. That’s true no matter what material is used.
This guy is a cyclist, not a physicist or materials engineer. I would take anything he says with a grain of salt.
His website looks like it was made in 1990. Not that that’s a criticism of his person. But damn.
There’s nothing saying a properly engineered foam wouldn’t behave exactly as well.
I posit to you that a pneumatic tire is exactly the “properly engineered foam” you describe: a closed, single cell foam with a substantial enclosed volume, leveraging the high tensile strength and toughness of its steel or Kevlar threads for the cell walls.
I’m also no physicist, but minimalist engineering would tend toward reduction of mass and surface area. Multi cellular foams need to expend material for the inter-cell walls. A single cell of equal volume and similar material has only its single, outer cell wall. Plus, just because a cell encloses a smaller volume doesn’t make it any stronger than a larger cell, so no advantage is gained nor lost by having a single cell.
Can a multicell foam be used as a tire? Of course we can press it into that use. Humanity has made concrete float, after all. But will foam be superior in cost, strength efficiency, weight, rotational intertia, roadside repairability, or in-field tunability by changing the air pressure? No. Instead, as the renowned cyclist described in the earlier link, an airless tire would have to compete on its strength of damage resistance:
They might make sense is if you commute a short distance to catch a train, and a flat tire would mean missing the train and being very late to work.
This type of scenario is no different for an acoustic or electric bike, and so there’s no apparent reason that ebikes should necessarily prefer airless tires. The pneumatic tire’s speed and range benefit still make it the preferred wheel technology for most automobile, bicycles, and airplanes. In space, that’s a different question altogether.
Eventough you are getting downvoted I’m going to have to agree with you.
Not to say air tires aren’t currently better than foam because they probably are. But like you say, there is probably some foam that can be better than air. Air isn’t magic, but it is good at its job.
This makes no sense to me. All that matters is how much the tire deforms from an impact, and at what speed. Using “all the air” isn’t some magical benefit. Ultimately it’s the rubber of the tire that has to deform to absorb the shock. It’s good that there is air behind it because solid rubber wouldn’t deform properly and the fact that air compresses means the rubber will deform deeply. There’s nothing saying a properly engineered foam wouldn’t behave exactly as well.
The cells of the foam are all touching each other. Shock will propogate from the are of impact and travel through the entire tire. That’s true no matter what material is used.
This guy is a cyclist, not a physicist or materials engineer. I would take anything he says with a grain of salt.
His website looks like it was made in 1990. Not that that’s a criticism of his person. But damn.
I posit to you that a pneumatic tire is exactly the “properly engineered foam” you describe: a closed, single cell foam with a substantial enclosed volume, leveraging the high tensile strength and toughness of its steel or Kevlar threads for the cell walls.
I’m also no physicist, but minimalist engineering would tend toward reduction of mass and surface area. Multi cellular foams need to expend material for the inter-cell walls. A single cell of equal volume and similar material has only its single, outer cell wall. Plus, just because a cell encloses a smaller volume doesn’t make it any stronger than a larger cell, so no advantage is gained nor lost by having a single cell.
Can a multicell foam be used as a tire? Of course we can press it into that use. Humanity has made concrete float, after all. But will foam be superior in cost, strength efficiency, weight, rotational intertia, roadside repairability, or in-field tunability by changing the air pressure? No. Instead, as the renowned cyclist described in the earlier link, an airless tire would have to compete on its strength of damage resistance:
This type of scenario is no different for an acoustic or electric bike, and so there’s no apparent reason that ebikes should necessarily prefer airless tires. The pneumatic tire’s speed and range benefit still make it the preferred wheel technology for most automobile, bicycles, and airplanes. In space, that’s a different question altogether.
Eventough you are getting downvoted I’m going to have to agree with you.
Not to say air tires aren’t currently better than foam because they probably are. But like you say, there is probably some foam that can be better than air. Air isn’t magic, but it is good at its job.