Cycling UK Forum

snibgo wrote:Yes, that's a neat explanation.

Above, I managed to type "centrigugal force" when I meant "centrifugal force".

Ah, that rare, or perhaps not so, beast Centrigugal Force (alt sp Centrigoogle), defined as that strange force that directs you towards websites selling an item you only wanted to research...

Edit

Just out of interest, I noticed from my first ride on one that a tandem requires a far greater level of steering input when compared to a solo bike. Any thoughts? is it purely to do with the greater wheelbase? If so, what is the ideal wheelbase to allow minimum steering input?

hatless wrote:Does the gyroscopic effect of rotating wheels make a difference? If a wheel is rotating on its axle, like the front wheel on your bike, and you turn it left by using the handlebars, then it will also try to lean - I'm not sure which way, but I think a bicycle wheel will want to lean against the turn. This ought to exert a twisting effect on the frame, but it may not be strong enough to notice.

Take your front wheel out, hold it in front of you, upright, by the QR or axle ends, get some one to spin it, and try changing the angle that it's pointing in - it's surprising just how much force is needed! Anyway, you'll soon work out whether steering also leans the wheel.

Motorcycle speedway riders corner with their front wheel pointing in the opposite direction to the bend. I assume that if there is sufficient power through the back wheel attempting to push a leaning bike into a corner, especially on a soft surface, the front wheel has to counter the effect. Experience suggests that the ability to successfully negotiate a series of bends on cycle or motorcycle is largely due to frame stiffness.

Deckie wrote:Just out of interest, I noticed from my first ride on one that a tandem requires a far greater level of steering input when compared to a solo bike. Any thoughts? is it purely to do with the greater wheelbase? If so, what is the ideal wheelbase to allow minimum steering input?

It shouldn't require more force if the castor and trail is appropriate. The head and rake angles for tandems had been worked out pre-WW2.

It doesn't require more force per se.

On my solo bike I merely lean into a corner, barely altering the angle of steer, and make my way round. Obviously the angle of the lean alters the shape of the tyre's contact area with the road as the bike leans over thus causing the turn. This can be demonstrated with any disc. If it has a stable enough shape it will roll straight and true if vertical. Once tilted to either side it will turn in that direction.

On the tandem it feels as though we don't lean so much an so there is a perceptable steering input. Perhaps it is purely to do with this lack of leaning, or maybe we do lean, it just feels different? I don't really know.

Having a longer wheel base, there will need to be a more extreme steering input to achieve the same turning circle. The angle of lean relative to the velocity will not be much different to with a solo bike travelling with the same velocity - as has been discussed previously that is governed by the relative positions of the centres of motion, gravity and contact points of the tyres with the road. To balance they must all be in line. So given the longer wheel base a greater steering input is required.

Leaning on a ASS 'bent bike is the only way to go round corners at any speed above walking pace - of course you have the other advantage that there is no danger of grounding a pedal so pedalling through them is an option, heel-strike on the front of the front wheel allowing of course.

B.

Deckie wrote:It doesn't require more force per se...

Tony Oliver's book Touring Bikes gives a good explanation of the difference between tandem and solo front geometry,