so how do bicycles work ...

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Stradageek
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Re: so how do bicycles work ...

Post by Stradageek »

One of my favourite demonstrations of counter-steering comes from riding a recumbent for the first time and trying to execute a right hand turn on a road with a severe left hand camber. Without the help a a body-lean I couldn't persuade myself to counter-steer dramatically enough to make the turn and had to stop. A few minutes later I did it completely naturally.

On the other hand I struggled to control an upright trike ridden on a straight road with severe left hand camber. Possibly because I'm now so adapted to a recumbent level of counter-steering I had to fight to stop myself steering hard left to try and get the trike more upright.

I gave up on that one, my recumbent trike, fortunately, doesn't have the same problem. Probably because I'm lower down, and reclined between the wheels.
rogerzilla
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Re: so how do bicycles work ...

Post by rogerzilla »

531colin wrote: 1 Dec 2021, 10:55am
rogerzilla wrote: 1 Dec 2021, 7:05am A bike will ride itself*, at least in a straight line. It needs no help from you. As long as the steering moves freely enough, it self-corrects as it starts to topple. It's an astonishing invention, really.

*you can easily prove this by pushing it downhill, but it's best to do it with soneone else's bike
Its an interesting piece of trivia, but has nothing to do with how we actually balance a bike.
(a 30 pound bike can't possibly hold up a 15 stone rider)
You've never ridden no-hands?
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Mick F
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Re: so how do bicycles work ...

Post by Mick F »

rogerzilla wrote: 1 Dec 2021, 1:05pm You've never ridden no-hands?
This is what I suggested up thread.

My Mercian (for instance) is stable. You can walk with it holding only the saddle. Behaves perfectly.
Ride it?
Twitchy, is a good adjective.
No Hands?
Yes, I can do it, but it's not easy at all and I rarely even try.
73degrees parallel with not much fork trail either.

I can ride No Hands on a bike easily, but only providing that the frame geometry (especially the fork trail) allows it.
Mick F. Cornwall
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531colin
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Re: so how do bicycles work ...

Post by 531colin »

Whats "fork trail" please, Mick?
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531colin
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Re: so how do bicycles work ...

Post by 531colin »

rogerzilla wrote: 1 Dec 2021, 1:05pm
531colin wrote: 1 Dec 2021, 10:55am
rogerzilla wrote: 1 Dec 2021, 7:05am A bike will ride itself*, at least in a straight line. It needs no help from you. As long as the steering moves freely enough, it self-corrects as it starts to topple. It's an astonishing invention, really.

*you can easily prove this by pushing it downhill, but it's best to do it with soneone else's bike
Its an interesting piece of trivia, but has nothing to do with how we actually balance a bike.
(a 30 pound bike can't possibly hold up a 15 stone rider)
You've never ridden no-hands?
I certainly have ridden no hands.

Perhaps you might read what I wrote?
531colin wrote: 1 Dec 2021, 11:05am I find the whole business of countersteering interesting.
("countersteering" is, I think, the name given to how you turn the handlebars to the left in order to lean the bike to the right to initiate a right turn.)
I have no doubt that countersteering is how I initiate a turn on a motorbike which weighs more than I do.
On a bicycle, when I'm riding "hands on" I may do the same.
When I'm riding a bicycle "no hands" I don't think I can countersteer.
Riding no hands I think what happens is I lean the bike in the direction I want to steer; the handlebars turn in the right direction due to "wheel flop" https://en.wikipedia.org/wiki/Bicycle_a ... e_geometry
I can't think how you might do countersteering "no hands"......To initiate a right turn, I have to countersteer left; but in order to steer left I must lean left, which actually initiates a left turn.
tatanab
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Re: so how do bicycles work ...

Post by tatanab »

Trail Rake.jpg
Are you mixing trail with rake? Low trail usually means increased rake and gives lighter steering. Higher trail means the steering takes more effort to get it to deviate from straight ahead. Trail is also dependant upon the head angle where rake is not. (Don't know why picture appears at 90 degrees, I tried rotating original but it always ends up like this.)
Jdsk
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Re: so how do bicycles work ...

Post by Jdsk »

Trail Rake.jpg
Trail Rake.jpg (22.73 KiB) Viewed 440 times
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531colin
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Re: so how do bicycles work ...

Post by 531colin »

Perhaps it isn't "wheel flop" which turns the steering riding no hands. ....but whatever it is, the same happens if you push a bike by the saddle....to turn left, lean left.
slowster
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Re: so how do bicycles work ...

Post by slowster »

531colin wrote: 1 Dec 2021, 2:20pm Perhaps it isn't "wheel flop" which turns the steering riding no hands
I think it is. When I ride no hands I stay upright by keeping my centre of gravity over the contact patches of the wheels (or probably more correctly, above a line drawn between the contact patches of front and rear wheels). To achieve that I make constant tiny adjustments in my position by exerting sideways pressure against the saddle with my body.

To initiate a turn when riding no handed, I continue to keep my upper body upright/vertical, and using that sideways pressure against the saddle I tilt the bike beneath me slightly in the direction of the required turn, causing the wheel to begin to 'flop'.
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Mick F
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Re: so how do bicycles work ...

Post by Mick F »

531colin wrote: 1 Dec 2021, 2:13pm Whats "fork trail" please, Mick?
You have a good explanation on many a thread.
Have I used the wrong expression?

Head angle down to the road, with the forks giving the front axle behind so the front wheel trails and castors.
Have I got that right?
Mick F. Cornwall
Jdsk
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Re: so how do bicycles work ...

Post by Jdsk »

Mick F wrote: 1 Dec 2021, 3:24pm
531colin wrote: 1 Dec 2021, 2:13pm Whats "fork trail" please, Mick?
You have a good explanation on many a thread.
Have I used the wrong expression?
"Bicycle and motorcycle geometry":
https://en.wikipedia.org/wiki/Bicycle_a ... e_geometry

Jonathan
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Re: so how do bicycles work ...

Post by mattheus »

tatanab wrote: 1 Dec 2021, 2:16pm (Don't know why picture appears at 90 degrees, I tried rotating original but it always ends up like this.)
Plenty of caster then - it's self-centring! Boom-boom.
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531colin
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Re: so how do bicycles work ...

Post by 531colin »

slowster wrote: 1 Dec 2021, 3:18pm
531colin wrote: 1 Dec 2021, 2:20pm Perhaps it isn't "wheel flop" which turns the steering riding no hands
I think it is. When I ride no hands I stay upright by keeping my centre of gravity over the contact patches of the wheels (or probably more correctly, above a line drawn between the contact patches of front and rear wheels). To achieve that I make constant tiny adjustments in my position by exerting sideways pressure against the saddle with my body.

To initiate a turn when riding no handed, I continue to keep my upper body upright/vertical, and using that sideways pressure against the saddle I tilt the bike beneath me slightly in the direction of the required turn, causing the wheel to begin to 'flop'.
Yeah, OK....
"Wheel flop" has a specific meaning in the context of cycle steering, as in the Wiki. article i linked the first time I mentioned wheel flop.
Essentially, as the steering rotates away from "straight ahead" the head tube lowers; so gravity tends to keep the steering turning once it has turned away from straight ahead.
I don't think that is what is at work either riding no hands or pushing the bike by the saddle; but I agree that tilting the bike away from vertical either riding no hands or pushing by the saddle causes the wheel to turn in the direction of lean.
And incidentally, that explains the observed phenomenon where a bike pushed off on its own is "stable"...if it leans (say) left, then the steering turns left and restores stability....what is remarkable is that the leaning and steering are perfectly balanced
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531colin
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Re: so how do bicycles work ...

Post by 531colin »

Mick F wrote: 1 Dec 2021, 3:24pm
531colin wrote: 1 Dec 2021, 2:13pm Whats "fork trail" please, Mick?
You have a good explanation on many a thread.
Have I used the wrong expression?

Head angle down to the road, with the forks giving the front axle behind so the front wheel trails and castors.
Have I got that right?
Thats trail. Your Mercian is a short trail design....twitchy/lively, etc.
I was trying to stop us getting mired in some of the usual ambiguities....fork rake, fork offset.......the old myth that a big fork offset produces a stable bike, when the opposite is true.....
rogerzilla
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Re: so how do bicycles work ...

Post by rogerzilla »

The bike needs the rider to steer it around a corner no-hands by leaning, but it doesn't need the rider to travel in a straight line.

There are bikes that can't be lean-steered: good tandems, expedition tourers, some folders, and anything where a fork with too much offset has been fitted. These bikes won't stay upright when pushed, either. The front wheel needs to naturally steer into the lean, correcting it. Then the bike leans the other way and self-corrects again. It follows a sinuous path but the movements are sufficiently slight that it is close to a straight line.

Countersteer is just a way to initiate lean quickly, and not possible when riding no-hands. Few riders will do it consciously - it's just how we turn tightly.

A 2-wheel drift with "opposite lock" steering..now, that's more interesting. And yes, I can, and have. But I don't like to; it means I've really messed up a corner. These guys are doing it deliberately:

https://youtu.be/R5AZ8yYHNts

Most other videos of bike "drifting" involve putting a foot down, but that's not the real thing.
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