Here we go again

[shedfire]

I had a Zinn, with a super short head tube, & a 150mm stem

True. Though Zinn were doing some good fun things with short rake forks to increase trail and that.

 

[Cristian-T]

I had a Zinn, with a super short head tube, & a 150mm stem

True. Though Zinn were doing some good fun things with short rake forks to increase trail and that.

The forks were awesome. I remember fondly, glancing down & wittnessing the "twang" I wonder what Andy Thompsons doing today ?

I guess, for similar reasons to wearing hideous coloured lycra, i ruined it with the 150stem. !

The fork design has inspired me recently, leaving a cool idea i have been bouncing about for abit

 

[al]

I've just missed five minutes of Thunderbirds for that video!!


What a pile of hairy swingers. :roll:


al.

 

[one-eyed_jim]

The bike stays upright because of the gyroscopic effect of the wheels turning. The faster the wheels are rotating, the greater the gyroscopic effect. That's why it doesn't fall over when you're moving, but it does want to fall over when you stop. You can keep it upright when stationary using balance, but you only need to use balance when there is little or no gyroscopic effect.

I don't think that's quite right. There is a gyroscopic component, and it does increase with speed, but it's not the most important factor.

A cyclist in motion is constantly falling to one side or the other, and steering to correct his fall. It's this steering that keeps the bike upright.

From the cyclist's point of view, steering in a curve of radius r generates a centrifugal force* of magnitude mv²/r.

That means that the steering input required to correct a given lean decreases rapidly as v increases.

On the other hand, as v drops towards zero, the steering input required to correct that same lean increases rapidly until the steering angle required becomes too great, or r is less than the wheelbase of the bike.

It's as that point approaches that we have to come up with new strategies to balance, either shifting our weight around on the bike, or shifting the bike around underneath us.

* http://tinyurl.com/24rxbro

 

[paulwakinshaw]

Quite a good read this has turned out to be, it has passed my evening here in Hong Kong rather quickly!

I can from my quite limited experience see both sides of the coin. This guy is...

A: Making a living (on the right side of the PAYE rules I hope)
B: Trying to cash in on the retro scene (to an extent)
C: Offering a product you cant just pick up at any Halfrauds

and

D: Getting some sort of "buy in" from those involved in the scene some 25+ years ago.

It might not suit all tastes here, but it seems to be balanced, it won't suit all of us, but then what will...??

Wako.

 

[GeoffApps]

Wako ~

I presume you're talking about me? If so, it's interesting that you have come to those conclusions, so, I'll put the record straight, especially for you... personally (but anyone can read this if they want).

A: The Cleland project is entirely government sponsored; I am doing it on welfare benefits and a lot of hard work. If you think I'm a sponger, the government receives in excess of £35,000 every year from a product I designed, but for which I received no payment.

B: Read more carefully the Cleland website (www.clelandcycles.wordpress.com) and you'll then understand that the AventuraTT is an entirely up-to-date concept in terms of its componentry, and has no retro elements in the design, other than those which are co-incidental; for example, is a Brooks saddle retro?

C: You will probably never get a Cleland from Halfords, but who knows? In the future you may be able to get a Cleland look-alike! Halfords sell the product mentioned above. It's sold elsewhere, too.

D: You may well be quite right there. It tends to be more mature (physically and mentally) riders who appreciate the benefits and subtle elements of the Aventura design.

It is not intended to suit all tastes, by any means, but it does serve to question many preconceived notions about off-road bicycle design; challenging prejudices regarding componentry. However, more to the point, it provides a choice in design which doesn't currently exist.

 

[GeoffApps]

Spot ON!

I use my TT for the shops as well. I don't carry large loads, just a couple of 'front' panniers on a small seat-pin-mounted rear carrier. With careful packing, these are also sufficient for a long weekend at a B+B or hotel.
With the tyres pumped-up hard, it spins along, and the riding posture, combined with a high centre of gravity, allows for quick changes in direction, sometimes around moving cars which don't always do what you expect, or a sudden decision to mount the kerb to get round a jam, and things like that.
Rear suspension comes in the guise of a spring saddle AND a sprung seatpost. However, with ANY form of suspension, it is wise to ride your bike dynamically and not just plonk yourself on it like a sack of potatoes.
The Aventura concept has always been an all-rounder, hence lights etc, with the principal bias toward off-road performance, but still a capable urbanite. I daresay some purchasers may want that bias the other way round, and adapt their Aventuras accordingly.
The Range Rover vs Land Rover debate continues!
All British, yes, but with a significant nod in the direction of The Netherlands...

 

[paulwakinshaw]

No Geoff,

I was talking about the guy in the video on whom the thread was started.

Wako

 

[GeoffApps]

My mistake!

I hope what I said was of interest anyway?

 

[Neil]

The bike stays upright because of the gyroscopic effect of the wheels turning. The faster the wheels are rotating, the greater the gyroscopic effect. That's why it doesn't fall over when you're moving, but it does want to fall over when you stop. You can keep it upright when stationary using balance, but you only need to use balance when there is little or no gyroscopic effect.

I don't think that's quite right. There is a gyroscopic component, and it does increase with speed, but it's not the most important factor.

Depends on your view of most important?

Think about when we learn to ride a bike, or teach a child to ride a bike. One of the key things is them cycling at a good enough speed for the gyroscopic effect to make it all easy for them, rather than the whole struggling for balance and trying to correct with steering.

I think Anthony got it just about right in that paragraph, in terms of the reality of cycling. Largely, the gyroscopic effect is the most important factor - since when we're teaching kids to cycle, or learning, it's the major thing we try to exploit to make it all simple and work.

A cyclist in motion is constantly falling to one side or the other, and steering to correct his fall. It's this steering that keeps the bike upright.

I'm not fully buying that.

Sure, as you say in the bits I've snipped, gyroscopic effect increases with speed, but when cycling at a normal pace, there's not normally a concept of falling to one side or t'other. I accept and recognise there maybe some steering correction, and still some balance input from the cyclist, but some of that is due to changing direction. True enough, at low enough speed, without much in the way of gyroscopic effect, bikes do feel like their constantly falling to one or the other side - but that's merely because there's little gyroscopic effect going on.

Once there is sufficient speed, and a fair degree of gyroscopice effect going on, I'd actually contend the bike really wants to stay upright, and in "perfect" conditions, like the world of physics normally suggests to initially understand something, a bike at a certain speed would keep itself upright, without rider to correct (assuming no friction, perfectly flat surface... etc...etc)

People can cycle at a reasonable pace with no hands on the handlebars - now sure, I get you can still correct steering by leaning, and at lower speeds you'd need to - but at normal pace, any steering correction would be minimal - perhaps similar to minor steering correction when you're driving.

Don't get me wrong - I recognise your point that there is still a balance thing going on, even at speed. But the gyroscopic effect is significant. At a certain speed, a bike rolling along without a rider to correct would probably largely stay upright (given a reasonably flat surface and no other significant affecting factors) and carry on in it's current trajectory, until it's speed dropped below a point where steering correction to balance becomes more significant that the gyroscopic effect of the bike / wheels at speed.

That whole rider-less bike thing, at speed, plus consideration of, say, the higher speeds of motorcycles, does show the significance of the gyroscopic effect.