Spokes on Wheel

Like this?

Exactly. Why don't bikes have these kind of spokes?

Thats the point of the pic, they do!

http://www.cyclestore.co.uk/productDetails.asp?productID=6940#

Looks to me as though the back wheel has spokes arranged the conventional way and the front wheel has the "radial" spokes. And, this might be a big clue! If you applied a large torque to the front axle (like the one applied to the back one by pedalling) you would create a huge tension in the spokes.

As it was said, it´s a matter of torque, in the other hand it has nothing to do with side charges which by the way are not present on bikes.

Unless, of course one considers sidecars ("chair") which do generate significant side-loading.

You are right!, but that´s the an exception.

As are vintage sportscars, & wheelchairs.

i didn't read all the links,, but the crossing of spokes on same side to wheel, is for hub stability,, not cross bracing, or support,, if the spokes went straight to the wheel,, it would work fine till you pressed on the pedal to rotate the hub,, then it would turn without the wheel and change the distance between,, so by crossing them,, creating a angle.. and not straight out,, you can apply torque to hub and not twist it,, making sense? trying to type fast here,, so little time and so many things to do,,

have a great day and make it fun,!

A straight spoke will have no sideways force and will therefore twist under any tension.

The tension vectors should be drawn to see why.

I believe that Hendrik has it about right- in order to assure stiffness and prevent lateral buckling.

milo

I'll concur.

Take this to an extreme & look at early, load carrying sportscar wheels.

More torque, side loading = higher angularity of spoking.

Quite.

It is not unusual to have a three-cross spoke arrangement on heavy-duty [HD] hubs, especially for the heavier rider, and four-cross + HD hub + heavier wire gauge for tandems. A skilled technician can build a wheel to the customer's bespoke (ouch!) requirements in a relatively short time.

I'm glad I read this - One of my brothers is a real big guy (a la WWF size) who likes cycling , but has trashed loads of wheels. It never crossed my mind to get bespoke wheels (!). That could be him sorted next Birthday . When you say skilled technician , I take it mean somebody who works in that field . The only custom builders I know of off-hand are Claude Butler . I shall investigate further . Kris

Imagine the spokes are straight. The inside hub is a circle with the spoke at the highest point. When a torque is applied to the hub as with riding or braking, the hub could twist some amount before the spoke elongated enough to provide a restoring force. If the spokes attach instead to an offset part of the circle, they have a much better mechanical advantage in transmitting torque from the hub to the outer wheel.

Cross Bracing.

Essential

To resist all tendency to take the rim out of a stable plane.

At some point in history a 'three-part-wheel' evolved . Not three planks , but three similar sections. I forget the design/advantage - anybody know ?

Also , does anybody know a use for a cycloid wheel (like a UK 50p bit) . Not like the rotor of a Wankel engine , one used as a wheel ? Competition cycling has seen the use of solid wheels - perhaps there is a good engineering point here. Maybe a motive vehicle could use a cycloid wheel - crazy (no axle point) but wow , how could you design it /would it work/does it have an application ?

Bike front wheels are generally radial.

Back whells are 'crossed` because they are required

to handle the torque of pedaling, (and sometimes

braking - on old 'coaster` hubs).

The set up ensures no spoke is directly aligned between ground and rotation point. Direct axial stress on the length of a spoke would cause it to buckle catastrophically. They paired arrangement ensures that a spoke is always subject to bending , which it will tolerate within limits.

Squash a straw between your hands and it will suddenly collapse . Angle the force and the straw survives the bending.

Wheel building is part science and part art, I should know, I build all my own wheels.

Basicly some of the posts above are correct: Radial spokes are poor at transfering torque from the hub to the rim and so are only normally found on the front wheels of bikes with rim brakes. Their sole advantage is a slightly shorter spoke and so a tiny weight saving. One other issue not mentioned though is the hub flange strength, radial spoking stresses the hub more AND it applies that stress on a thinner bit of metal.

99% of wheels are a 3 cross design. But there are loads of ways to build wheels like.

Radial

1 cross

2 cross

3 cross

4 cross

snowflake

You can even mix and match eg 3 cross on the drive side and radial on the non drive side.

Don't get me started on the diferent spoke design, or rims or...........

Please expand on the advantages and disadvantages of the different spoke patterns. CR4 is one of those places where we are interested in those things that wives and even friends find boring and/or unintelligible.

I am all for BlueAussieBoy's appeal to#15 -' Let us have it'!