- This topic has 7 replies, 4 voices, and was last updated 2 years, 4 months ago by
.
-
Posts
-
interesting article – I will leave it to the engineers to comment
https://www.fastcompany.com/3062239/the-bicycle-is-still-a-scientific-mystery-heres-whyGarryD
Interesting. I looked at bike dynamics a while ago, and my understanding is the non linear equations of motion for a riderless bike are quite well known. Solving the requirrs s bit of computing power, but nothing hard these days.
Basically, because of caster, when you turn the handle bars, the front of the bike drops down, maybe 1cm. This is why the handle bars have a tendency to turn by themselves once any small movement occurs: gravity wants to pull the bike closer to the ground.
When a rider less bike rolling along leans to one side and starts to fall over, the handle bars turn into the fall because of the caster. There’s a forward speed at which the turning handle bars turn fast enough to stop the lean. Because that’s exactly how a bike is balanced, by steering into the fall. If the bike is going faster, the handle bars don’t turn fast enough, and the bike just rolls over. If the bike is going very slowly, the handle bars turn to fast, and over correct. Basically, the bike falls over on the other side to it’s initial lean.
But a bike with a rider is very complex, because the rider can shift the centre of gravity, turn the handle bars, and resist the bikes natural desire for the bars to turn. I don’t think anyone has found it possible to write the equations of motion for a bike with a rider.
There were some great discussions at the last hand made bike show on bike dynamics, and what makes a bike pleasant to ride. Custom bike builder Bastion have basically put the equations of motion for a riderless bike into a spread sheet, and can plot on a graph where any bike falls compared to a desirable square region.
Did you know, that in order to turn left, you must first turn right? Its all in the physics…
regards
Rob
Dear MacO’Dowd,
could not read the article without committing to the site. so… never going to happen.
however, the above responses suggest this is about, “Counter Steering”.
a good overview is at https://www.tunedtrends.com/what-is-countersteering/
talks about how Honda did research into motorcycle dynamics etc.Simply put, to turn left on a two wheel vehicle (at at not fall over pace), we lean left and the bars tend to turn right, ie counter steering. When understood it is an effective method of high performance turning, ie you push the left bar away from yourself and we turn left aggressively, we push the right bar and we turn right.
Adrian will be able to explain how aggressive counter steering on a motorcycle can help you turn faster; he was a classy motorcycle racer.
It is something to be done to achieve low lap times when racing or to simply go fast on a bendy road.
I believe it was Eddie Lawson (30 years ago) came in after a Superbike race, having not crashed but his bars were bent, that is how hard he pushed on the bars to counter steer.The phenomena if understood and practiced, can make you a much faster descender and give you the ability to avoid danger on the road aggressively without falling over.
You need to link this with weighting the outside leg of course and not over working the tire grip. Is a lot to it, buy it is the correct physics as the acticle should explain.I hope you find the article interesting.
Ray of Sunshine…
Everybody counter steers a bicycle, because it’s simply physics in action, and the same physics applies to everyone. You don’t need to learn it. Also, it only occurs on entry to a corner, not through the entire corner. Although counter steering a bike, and oversteer both involve steering in the opposite direction of the corner, they are done for very different reasons, and shouldn’t be confused. Oversteering is done when the back tyres are sliding and is common in motorsport (especially non tarmac). On a bike, it’s very easy to fall off (high side or low side) if you try it, a car, not so bad. When oversteering is required, it’s usually not on the entry to the corner, but at least the exit. So, it’s kind of the opposite to counter steering. One is a way to turn in, the other is a way to control the line on exit.
- You must be logged in to reply to this topic.