|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Centerpoint steering
Hello,
I have started reading http://www.eland.org.uk/steer_intro.html and I have a question regarding this: Also, if just one of the front wheels is braked, or the two front wheels are braked unevenly, the forces should again all pass through the kingpin axes and not affect the steering. How is this possible? The wheel can turn around the kingpin , and it's axel is not exactly on the kingpin, so any force on the wheel axle (which would be created by breaking) would turn the wheel and affect the steering. right? -Leav |
Ads |
#3
|
|||
|
|||
Leav wrote:
[A tadpole's front] axle is not exactly on the kingpin, so any force on the wheel axle (which would be created by braking) would turn the wheel and affect the steering. To which Jeff (very astutely IMHO) replied: ... the kingpin's axis should intersect the ground on the same line as the centerline of the tire. This will prevent the tire from being steered right or left by off-center braking... But having been officially notified now in another thread that: ... experts are welcome here too provided they do not go on and on at too great a length. Perhaps, I too (a modest non-expert) can expand a bit: It may help to think of braking force applied to the hub carrier assembly (kingpin) at the tire's contact patch. If a line through the rotational axis of the kingpin hits the center of that patch, almost no matter what kind of other parts are in the assembly or their 'internal' geometry, then the braking force will ultimately have almost no 'lever arm' to cause the kingpin to turn and steer the trike. FWIW: There's a bit of highly technical design and jargon in the science (and art) of steering with a two-wheeled 'axle', most of which is of almost no relevance to most tadpole riders. E.g., the tire's contact patch is really usually slightly behind the kingpin's ground reference point, (which most folks think of as 'trail') to enhance high speed stability. Most newer tadpole designs also have the tread contact patch located just inboard of the kingpin's ground reference point, so that single-sided braking actually applies a small intentional force toward rotating the kingpin away from the braking side. For example, if you apply only the right side brake, this force would try to steer the trike to the left. But braking on one wheel to the right of the trike's center of gravity also creates a couple (or moment) on the trike as a whole ('body' or mass) that tries to make it turn to the right. If this steering design (called ABC for Asymmetrical Brake Compensation on the LoGo trikes) is done well, the end result will be that the two forces almost exactly balance, and the trike shows almost no tendency to pull to the side, even under very heavy one-sided braking. The design tradeoffs for ABC are relatively trivial, and most trikeys who've ridden a tadpole with this design love its added safety and convenience. Regards, Wayne |
#4
|
|||
|
|||
From what I've read, zero-scrub IS center point steering. The contact patch
and king in axis intersect at the same point, and produce zero scrub. Positive and negative scrub radius are not "center point steering" however, and while I've heard that positive scrub radius is called asymmetrical braking compensating (or something like that) I haven't heard of another term for negative scrub radius. No, the kingpin's axis is not vertical. It is angled so that the bottom of the kingpin is farther out than the top. In order to design zero-scrub-radius steering (which is what you're describing and *not* centerpoint steering), the kingpin's axis should intersect the ground on the same line as the centerline of the tire. This will prevent the tire from being steered right or left by off-center braking (not "breaking") forces. Jeff |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Question: Cutting a carbon steering tube? | The Eye | Techniques | 7 | April 10th 05 04:33 AM |
Welding a CroMo Steering Tube | Thomas Reynolds | Techniques | 4 | May 12th 04 05:33 PM |
Below Steering | TheMilligans | Recumbent Biking | 23 | May 5th 04 10:49 AM |
Alterning steering behaviour | NC | UK | 4 | September 14th 03 02:13 PM |
Threadless Steering Tube Extensions? | Bruni | Techniques | 3 | August 28th 03 12:53 AM |