Hubless eBikes, AI Integration, & More - The MTB-Adjacent Tech From the CES Show is... Interesting? - Pinkbike
Hubless eBikes, AI Integration, & More - The MTB-Adjacent Tech From the CES Show is... Interesting? - Pinkbike
The intersection of consumer electronics and mountain bikes is a dark, scary place.
I like that the author hit it right on the head, with regards to the "hubless ebike":
The futuristic-looking eBike doesn't save any weight by not having hubs with it hitting the scales at a claimed 26kg/58lb.
For those not familiar with the design of conventional (read: acoustic) bicycle wheels, they're not really any different than ebike wheels; the physics are mostly the same. Save for maybe that ebikes draw more from fat-tire and MTB wheels than road bike wheels, they all draw from 200 years of converging innovation. To that end, today's spoked wheels and rubber pneumatic tires are highly optimized for the application. The late Sheldon Brown wrote this about the bicycle wheel:
A tire, then, supports its load by reduction of downward pull, very much the same way that spoking of the wheel supports its load. The tension-spoked wheel and the pneumatic tire are two examples of what are called preloaded tensile structures, brilliant, counterintuitive designs working together remarkably to support as much as 100 times their own weight.
On airless tires, he harbors justified misgivings:
Airless tires have been obsolete for over a century, but crackpot "inventors" keep trying to bring them back. They are heavy, slow and give a harsh ride. They are also likely to cause wheel damage, due to their poor cushioning ability. 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. They also corner poorly.
Adding ebike technology does not overcome the problems of hubless and airless wheels, and barring some sort of specific need for the wheel centers to remain clear, this is pure gimmick.
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.
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.
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.
Stop trying to make hubless wheels work. A normal bicycle wheel is stronger, lighter, simpler, and the bearings only have to handle the lower speed at the center of the wheel, instead of the speed found closer to the rim.
"...bu-bu-but they look neat!"
What advantage does a hubless bike bring to the table?
No way for street toughs to shove rebar through your spokes and send you flying over the handlebars so they can steal your baguettes and celery.
Same as folding phones I guess; novelty.
Folding phones does bring a practical use to the table, you get a phone that you can fold out into a tablet that fits in your pocket.
To be fair, flip phones prevent unwanted user input and protect the screen.
Looking neat?
Thst is a design advantage, I'll grant you that, but it seems way less practical than a normal wheel.
I don't know if it's an advantage, but I've seen one lately, and it was fucking loud.
Like eeeeeeeEEEEEEEEEEEEEEEEeeeeee loud.
Rub we need a remake of pee wees big adventure now
Electric mountain bikes aren't allowed on mountain in Colorado but keeping those asshats out is kind of a pain. They bought the expensive toy, now it's everybody else's problem because the money spent justifies that.
I'm guessing this is mostly about what are effectively electric motorbikes. In Finland you're not allowed to drive motor vehicles on other people's land without their permission but pedal assist eBikes with 250W motor and limited to 25kph (15mph) are considered bicycles by law and those you are allowed to ride anywhere.
Vehicle culture is just generally different here in the United States. Even if sane, rational rules for ebikes were to be established they'd be ignored out of spite. For any idea of the quality of individuals I'm talking about, yesterday I saw two separate vehicles enter the bus station by passing the "DO NOT ENTER" sign, realize that the road they were on wasn't going to their fucking hotel or wherever they were heading, drive up onto the pedestrian portion of the bus station, turn around, and leave the wrong direction on a one way street. Speaking specifically for bicycles I've been doing trail maintenance and had a mountain biker come at me screaming because we were out there working and were in his way after he passed a sign telling him the trail was closed and climbed a fence we put up just after the sign as a result of previous and similar incidents.
Edit: I should probably clarify what I meant by 'on mountain' that's just kind of shorthand slang for the property controlled by the local ski resort. Though the feds have similar rules, so buying an electric mountain bike around here is stupid since all you've done is spent at least another $2,000 on a bicycle you can't legally use outside of your private property.