GOKISO Aerospace Hub for bicycles aims to give bearings a break
If you've ever watched the Tour de France and winced as all those skinny-wheeled racing bikes bounced over the cobblestone roads ... well, you were right to do so. Not only are such hard, rough surfaces capable of bending rims, but they're also hard on hub bearings - as the axle shaft flexes ever-so-slightly in response to hitting bumps, the ball bearings that encircle it are pressed against the hub's bearing races, both causing friction and potentially damaging the bearings. Japan's Kondo Machine Corporation, however, has created a product that is claimed to minimize this problem. It's the "jet-engine-inspired" GOKISO Aerospace Hub, and we spied it last week at the 49th Paris Air Show.
The big secret to the GOKISO hub is its ability to spring under pressure. In a traditional hub, the axle shaft is unyieldingly connected to the rest of the hub. This means that any time the shaft flexes, it immediately presses against the inside of the hub. At either end of the GOKISO, however, there's a half-millimeter of space between the shaft and the hub body. While that might not sound like much, it's reportedly enough to allow the shaft to deform under pressure, without coming into contact with the inside of the hub.
The Aerospace Hub also features two sets of deep-groove bearings at either end of the shaft (for a total of four per hub), whereas most hubs just utilize one shallow-groove bearing per end. Although deep-groove bearings are able to handle heavier loads, they are also less tolerant of misalignment. The springing action helps keep such misalignment to a minimum, but so do the hub's unique spherical nut and washer.
With a regular hub, there is absolutely no play between the axle and the bicycle's frame. According to Kondo, this means that the hub can be deformed when the wheel is mounted on the bicycle, as the axle bends to accommodate the inside angle of the dropouts. The Aerospace Hub's spherical nut and washer, however, are able to slide up and down against one another, instead of simply locking up face-to-face. This means that even if the front fork dropouts are splayed into a V-shaped orientation, the axle will still run straight between them, instead of bowing.
All of this innovation does come with a slight weight trade-off ... depending on what you're comparing it to. The front Aerospace Hub weighs 240 grams (8.5 ounces), with the rear tipping the scales at 455 (16 oz). By comparison, a Shimano Dura-Ace front hub weighs 125 grams (4.4 oz), while the rear sits at 254 (9 oz).
If you're interested in becoming a cycling pioneer, Kondo is currently selling a test batch of the GOKISO hubs on the company website. A front and rear hub together will set you back 150,000 yen, or about US$1,849.
The video below explains how the hubs work, in more detail.
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Also, designing in some freeplay in order to reduce bearing loading is admirable, but using a better bearing and race which can cope with the loading in the first place is a better solution. Leave the \'suspension\' up to the tyre/spokes/fork. Hubs should be rigid.
Personally, I love my durace hubs on my roadbike, but I also admire Chris King products; http://bertiebuck.co.uk/files/2011/05/Chris_King_rear_hub_cutaway.jpg
A real aerospace solution would be to use a fluid film bearing, if that could be done...
Cute idea but bad business decision. And what a waste of resource and money.