vibrations in bicycle frame
 

Hello

Is there vibrations in bicycle frame due to irregular surface of road? and it affects performance of rider? In which material vibrations are less in steel or aluminium? If natural frequencies values is high it means there is more vibrations? Is there relation between natural frequency and stiffness?

The natural frequency of a frame is extrememy high, and road vibrations are a very low frequency. They don't have any significant harmonics. Vibrations do affect performance in two ways. One is where forward momentum energy is converted to vibration and dissipated in the riders flesh, causing discomfort. Second, this discomfort fatigues the rider, decreasing endurance. Both steel and aluminum can ride smooth or harsh, depending on design. But tire size, construction and pressure make a bigger difference. This is where the trend toward larger tires and lower pressures comes from.
:popcorn

The Commuting Forum isn't the best place to ask these questions. At best you'll be getting anecdotal answers or interpretations of things someone has heard elsewhere. At worst, you'll be getting personal prejudices and opinions dressed up as fact.

(Hence catgita's popcorn graphic. Enjoy the show!)

For definitive answers you should be asking actual framebuilders. Velocipede Salon is a forum founded and run by framebuilders and their fans.

You'll also find good information at Metallurgy for Cyclists by framebuilding company Isis.

If you're not that ambitious, the short answer is that in contemporary metal frames, builders select tubing of varying diameters, tapers, wall thicknesses, and butting in order to tune out harmonics and ride noise, and balance flex with stiffness. Some go as far as to use different tubing brands and models in different frame areas.

If you look at contemporary designs and builds, you'll never see the same tube twice, no matter which metal is used. Most actual frambuilders agree that the material is far less relevant than tubing selection. (That's an interpretation of things someone has heard elsewhere.)

My own experience with steel, aluminum and titanium bikes bears this out. In terms of frame vibration and harmonics, the worst bike I ever owned was steel, built in the old-school way where all three tubes of the main triangle were identical. The best-riding bike I own is titanium, and you can see the tapers in the tubes that are meant to reduce harmonics. My two aluminum bikes, with double-butted tubes of differing diameters, rival my titanium one in the harmonics department. (That's an anecdotal answer.)

There is a persistent myth that steel bikes magically remove (or 'damp') vibrations. But this is not true. Steel (as with all metal bike frames, including Aluminum) has practically zero damping in the material. The only damping in a rigid bike will be from the tires and your body. The natural frequency of the frame is dependant on the stiffness of the frame, which is something determined more by the design and construction of the frame than by the material.

you need a Moulton , they made suspension for both small wheels for pavement ..

or a Fat Bike their 4"+ tires are like big balloons softening the ride.

Just about anything that runs wider than 30mm tires can feel like a pillow with the right tires at the right pressure.

How many sock puppets can one individual get away with on these boards?

A first post asking for opinions on steel vs. aluminum does seem fishy, doesn't it?

There are numerous factors that affect the harshness/softness of the ride of a bike: frame material, alloy and frame design.

Some people stay away from aluminum because they believe that it produces a harsher feel. I don't have enough knowledge or experience to justify a response to that. Generally, the less expensive road bikes are made of aluminum because it is a relatively inexpensive material. I think that I am correct in saying, all things being equal, aluminum is less flexible and more brittle than some other materials but you also have to take into account the alloy of the metal as well, some are softer than others (as well as many other properties of different alloys).

Given that aluminum is common in less expensive frames and aluminum tends to be more brittle than some other frame materials, consider this. The Salsa Warbird frame is aluminum, not an inexpensive bike and the seatstays, despite being made of aluminum, are designed to flex and thereby produce a softer ride.

There are many factors that affect the ride of a bike, design, alloy and material are only three and all three can be played with to produce different types of rides.

Reeks!

You are mistaken about the general nature of the materials and their different alloys. Aluminum is more flexible than steel, but the construction of aluminum frames generally takes this into account so they aren’t wet noodles. There used to be aluminum frames with the same 1” tubing diameters of their contemporary steel frames and they were extremely flexy. Oversized tubes are the main strategy used to make aluminum tubes suitable for today’s bicycle frame. More expensive frames generally have butted and tapers and shaped tubes to tune the ride, but less expensive frames are usually made from plain gauge tubes welded together. Steel frames generally follow the same rule – the ‘gas pipe’ steel used for BSOs has no more flex in it than their cheap aluminum cousins, but people still repeat the ‘compliant feel’ nonsense.
As for different alloys, all alloys of aluminum have very nearly identical stiffness. The same goes for different steel alloys. The difference in stiffness of the finished frame will come from the geometry of the tubes, and the fancier alloys are usually stronger so lighter tubes can be used, and lighter tubes will generally allow more flex. This is correct.

Thank you for the correction

But he started out with "Hello"... :lol: