Talk:Hub-center steering

Diagram
This is really hard to visualize. Is there any way we could get some diagrams in here? Bsirvine (talk) 16:50, 19 November 2007 (UTC)

I was looking through the US and European patent database, but didn't find any patent (which is really odd). I think someone is going to have to draw a picture.--Davidwiz (talk) 02:21, 27 May 2008 (UTC)

For diagrams, Tony Foale (www.tonyfoale.com) has many pictures, diagrams and articles about what he calls "Funny Front Ends". He designed and built several, including leading link, girder and a type of hub center system that uses an upright to steer and a swingarm to carry the axle and take suspension loads. Very cool stuff. Thank you, Mr. Foale! As for the description of "stiction" in the text of this article, it is incorrect when it says that steering loads cause it. Stiction is the name used to describe the friction and the sticking that fork seals undergo when hitting a bump. Imagine that you've just hit a pothole, a rather serious one. While the steering head, and thus the upper fork tubes, are trying to continue at the speed of travel.the wheel, axle and hence the lower frok tubes are being pushed backwards by the bump. They are therefore no longer trying to slide parallel to the upper forks, but rather are trying to slide at a much steeper angle. Hence,the upper fork seals are loaded at the front, the lower at the rear, and the fork tubes are momentarily held in place, unable to compress to absorb the shock caused by the pothole. They stick together under this uneven friction. Hence the word coined for this condition - stiction. Ths is the reason that sportbikes have both gone to such huge fork tube diameters and using the "Upside Down" design where the slider is held in the triple clamp rather than carrying the axle as is traditional. With the larger tubes on top, unsprung weight is lowered, stiction is reduced because the lower seal is much closer to the axle and the entire structure is much stiffer because the stiffness of any structure varies by the square of thickness if using the same materials. Put simply, a 50% larger tube diamter yields a 125% increase in stiffness. But it's heavier, so there comes a point of negative return in this approach. So, off we go with alterntive front ends, trying to invent the Next Great Leap in motorcycle design. Gentlemen, start your engines. 67.150.17.80 (talk) 00:39, 15 December 2008 (UTC)John Gregory, GregoryDesigns...

HCS Turn Limit?
What is the turn limit of the front wheel in HCS? I read a bike may need +-15° for normal operations. But by the images here it seems to be less. -- Portolanero (talk) 10:05, 2 November 2012 (UTC)

Johammer 1
The Johammer 1, a production electric motorcycle, uses HCS. See "The Johammer 1, Austria's Wild One," BBC, April 15, 2014 -- Chris — Preceding unsigned comment added by 71.255.211.171 (talk) 11:36, 15 April 2014 (UTC)

HCS Definition
"Hub-Center Steering" is a precise sounding term and some of the examples given in this article do not seem to be covered by it. HCS implies that the components that define the steering axis are contained within the wheel hub and wheel bearings. The Ner-a-car seems to fit the description and as a result the rake angle must vary as the suspension moves through its travel. The Bimota Tesi and Difazio front ends have bearings within the hub that define a steering axis, but the component on which those bearings are carried (king pin?) is (unlike the ner-a-car) free to rotate about the same axis as the wheel, and additional components are needed outside of the hub to control the motion. The arrangement allows the rake angle to remain substantially constant and independent of suspension travel. I think the Tesi and Difazio should be considered HCS because the steering axis is defined by the bearings within the hub even if an external mechanism is provided to compensate for suspension motion. The Yamaha GTS 1000 is not HCS. It is possible to imagine a GTS-like front suspension where the lower steering bearing is located within the hub while the upper bearing remains in its current location above the wheel, it would be similar in principle to the Tesi and the Difazio, but I don't think it would be HCS because the spherical bearing within the hub would not, on it's own, define a steering axis. In the absence(?) of an established definition of HCS I propose the following: "A steering system where the steering axis is defined by components contained within the notional cylinder(s) containing the wheel bearings; notwithstanding any additional components provided to adjust the rake angle of the steering axis, to compensate for the the motion of the suspension system, which may be located outside of those cylinder(s)." Urleigh (talk) 05:26, 21 August 2020 (UTC)