Steering cycles: bikes vs. trikes

[a_chap]

Why? What would happen if they didn't?

When cornering fast a trike has a tendency to tip over of you don't lean.

I've been fortunate enough to ride many hundreds of miles in the company of people like Jim Hopper and Pete Gifford - both renowned trikies - and I've witnessed their inside rear wheel lifting off the ground on corners.

 

[gentlegreen]

I routinely push heavily-loaded trolleys of kit around the site - often with dubious steering and I often visualise myself as a sidecar passenger when trying to direct them to where I want them to go ...

 

[Mation]

When cornering fast a trike has a tendency to tip over of you don't lean.

I've been fortunate enough to ride many hundreds of miles in the company of people like Jim Hopper and Pete Gifford - both renowned trikies - and I've witnessed their inside rear wheel lifting off the ground on corners.

Why does the inside rear wheel lift?

 

[a_chap]

Why does the inside rear wheel lift?

Weight-shift.

Exactly the same as a car cornering.

 

[Spymaster]

Why does the inside rear wheel lift?

When you’re turning your momentum wants you to go straight on and the centre of gravity on an upright rider is high, which increases the force throwing the rider and trike to the outside of the turn. Leaning over into the turn lowers the centre of gravity and increases the weight over the inside wheel pushing it down.

 

[Mation]

When you’re turning your momentum wants you to go straight on and the centre of gravity on an upright rider is high, which increases the force throwing the rider and trike to the outside of the turn. Leaning over into the turn lowers the centre of gravity and increases the weight over the inside wheel pushing it down.

Thank you!

So a trike with a rear brake will be less prone to tipping. (Most have front brakes only.)

 

[Mation]

Weight-shift.

Exactly the same as a car cornering.

Isn't that car going round to the right?

 

[teuchter]

Just picture a double decker bus, where the top of it keeps going in a straight line but the bottom of it is steered to the side by the front wheels. Then you can see why it ends up leaning over.

It's misleading to say there's a force throwing anything to the outside of the turn. All that's happening is that there's a force that is trying to effect the turn, but it's acting at one point on the object rather than acting on the whole object evenly. Just like if you push someone on their upper body, they don't just slide sideways, their feet stay where they are and the top of them leans over and then they fall on the ground. If you've done it right.

 

[Athos]

Thank you!

So a trike with a rear brake will be less prone to tipping. (Most have front brakes only.)

I suspect there's not enough weight over the rear wheels, such that they'd be prone to locking when lifted, making a tip more likely when they touch down again (which is probably why they don't usually have them).

 

[Spymaster]

Just picture a double decker bus, where the top of it keeps going in a straight line but the bottom of it is steered to the side by the front wheels. Then you can see why it ends up leaning over.

It's misleading to say there's a force throwing anything to the outside of the turn. All that's happening is that there's a force that is trying to effect the turn, but it's acting at one point on the object rather than acting on the whole object evenly. Just like if you push someone on their upper body, they don't just slide sideways, their feet stay where they are and the top of them leans over and then they fall on the ground. If you've done it right.

Yeah. That’s much clearer!

 

[mauvais]

No, weepiper is right, you can do it without touching the handlebars, by shifting the balance of the bike. Countersteering is just another method of doing that.

This is wrong - weight shifting induces countersteer, it is not an alternative.

 

[teuchter]

This is wrong - weight shifting induces countersteer, it is not an alternative.

Ok, then I am defining "countersteering" as using your hands to steer the handlebars as a direct action. You can steer the bike by shifting your weight, which Saul Goodman was claiming was untrue. Even if the bike does its own countersteering thing as part of what happens when you shift your weight, it remains the case that you can steer the bike by shifting your weight.

 

[nick]

A bicycle stays upright in motion through gyroscopic force.

Apparently not. There was lots of comment in 2016 that it was less gyroscopic force and more the magic bike pixies. If the gyroscopic effect is removed, they still stay upright

BBC
bike radar
Camridge uni

 

[beesonthewhatnow]

The Bicycle Is Still A Scientific Mystery: Here’s Why

Why does a bicycle stay upright while moving, even with no rider? <em>Scientific American</em> explains the long search for the answer.

www.fastcompany.com

The (Still) Mysterious Physics of Riding a Bike

A new study comes closer to cracking the code.

www.bloomberg.com

 

[beesonthewhatnow]

 

[nick]

Liked because I beat you by 3 minutes. My equivalent of KOM

 

[Cid]

Ok, then I am defining "countersteering" as using your hands to steer the handlebars as a direct action. You can steer the bike by shifting your weight, which Saul Goodman was claiming was untrue. Even if the bike does its own countersteering thing as part of what happens when you shift your weight, it remains the case that you can steer the bike by shifting your weight.

Sure, do feel free to define terms in any way you please. It doesn’t make things more confusing at all.

 

[A380]

Apparently not. There was lots of comment in 2016 that it was less gyroscopic force and more the magic bike pixies. If the gyroscopic effect is removed, they still stay upright

BBC
bike radar
Camridge uni

If you ride a Brompton or any other small wheeled bike you know that any gyroscopic effect is minimal. It’s pixies all the way. Taken to as absurd extent those little folding scooters with single skate board wheels can have almost no gyroscopic effect and yet the kind of idiot who would ride one can ride one.

 

[Cid]

Mation why are you actually asking by the way? Just out of interest or because it might affect a purchase choice or something? Honestly it’s something I doubt any cyclist really thinks about.

 

[teuchter]

If you ride a Brompton or any other small wheeled bike you know that any gyroscopic effect is minimal. It’s pixies all the way. Taken to as absurd extent those little folding scooters with single skate board wheels can have almost no gyroscopic effect and yet the kind of idiot who would ride one can ride one.

Is a Brompton more difficult to push along holding the saddle, than a normal bike?

When I imagine I notice the gyroscopic effect is when I'm pushing my bike along by the saddle (I mean when I'm not on it). When you are walking slowly it doesn't really work - the front wheel flops around - but when you speed up a bit that stops happening.

 

[DownwardDog]

Why does the inside rear wheel lift?

Centrifugal force acts through the CoM of the trike/rider combination. This is opposed in the opposite direction by the contact patch of the tyres which, being at ground level, is lower than the CoM. This sets up a moment in the roll axis.

 

[teuchter]

Sure, do feel free to define terms in any way you please. It doesn’t make things more confusing at all.

Thought I'd see what the Sheldon Brown definition was.

The second paragraph seems relevant to this thread.

Countersteering

When a bicycle turns, it must lean into the direction of the turn so that the tilt of the bicycle and rider counterbalances the "centrifugal force" created by the act of turning.
In order to turn left, you start by turning the handlebars to the right for a moment. This moves the front wheel out to the right of the center of gravity, so the bike will start to fall to the left. This is immediately followed by turning the handlebars to the left to cause the bike to remain in balance, which also creates the desired left turn. "Countersteering" refers to the momentary motion of the handlebars in the opposite direction of the desired turn. usually, this is accomplished through the normal slight weave of the bicycle to maintain balance.


Some people, particularly motorcyclists, make a big deal out of this as if countersteering is some special advanced riding technique that you must learn to become an expert bike handler. It isn't. It's just a fancy sounding name for the normal process by which any two-wheeler (or even a unicycle) is controlled.


However, to be ready to swerve quickly out of danger, it is useful to practice quick, forced countersteering so as to initiate a turn as quickly as possible. The amount of countersteering needed decreases as speed increases, and practice will teach you how to approach the limit of traction without exceeding it and skidding out.

 

[A380]

Is a Brompton more difficult push along holding the saddle, than a normal bike?

When I imagine I notice the gyroscopic effect is when I'm pushing my bike along by the saddle (I mean when I'm not on it). When you are walking slowly it doesn't really work - the front wheel flops around - but when you speed up a bit that stops happening.

No it’s easier in fact. Just one of the brilliant things about its design is that you can push it one handed by the saddle and steer it by ‘balance’ leaving your other hand free to carry a bag or use a ticket gate. I can’t believe that’s accidental.

 

[Cid]

Thought I'd see what the Sheldon Brown definition was.

The second paragraph seems relevant to this thread.

Yes, exactly.

To be fair probably somewhat crossed wires on this since, as sheldon says, some bikers do bang on about as a specific technique rather than just an element of how bikes turn.

 

[a_chap]

Isn't that car going round to the right?

Yes, and its inside rear wheel is lifting off the ground.

 

[klang]

A bicycle stays upright in motion through gyroscopic force. If you just turn the bars without shifting your weight you'll crash. A trike stays upright without gyroscopic force so if you just lean without turning the bars it doesn't steer. I find a normal trike (one wheel at the front) almost impossible to ride because it doesn't steer with your weight.

Last time I rode one I got a terrible backache

 

[beesonthewhatnow]

Traditional trikes are horrible to ride because by design they want to tip over when cornering. The solution is to have two wheels at the front, like the old Morgan sports cars.

 

[DownwardDog]

Traditional trikes are horrible to ride because by design they want to tip over when cornering. The solution is to have two wheels at the front, like the old Morgan sports cars.

You can get those pieces of shit on two wheels very easily. I saw a bloke roll one at Oulton. He was able to take the remaining bits home in a Tesco bag.

 

[maomao]

Do the two back wheels on a trike have separate freehubs?

 

[teuchter]

Yes, exactly.

To be fair probably somewhat crossed wires on this since, as sheldon says, some bikers do bang on about as a specific technique rather than just an element of how bikes turn.

Motorcyclists always seem quite keen to think that they have some kind of special skills. They don't. They just sit on a very heavy version of a bicycle, and are too lazy to pedal.