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# Friction in a steel ring

## Friction in a steel ring

(OP)
Hello, Colleagues

I would like to ask you some question, which I am currently working on. We have a column and around this column is attached metal ring (locked with bolts of course), which are going to carry lamps(attached to the cylinder, look the atached file). I would like to ask you if there is a way to calculte the friction force which this ring exerts on the column, if it stars to fall down and mostly is there a way to calculate to the total force or stress acting on the column if the bolts ae pretension and the locked for the ring around the column. WHat is gonna be the total force? Because if you imagine the bolts are maximum tensioned and the ring somehow "squeez" and shrink, then this will cause stress on the column?

I would like to hear your engineering brains ;)

Thank you very much in advance!

Have a nice day!

### RE: Friction in a steel ring

Yes, there is a way.

### RE: Friction in a steel ring

Look up this post in the Structural other room.

Coefficient of friction for steel base plate to concrete

### RE: Friction in a steel ring

(OP)
jgKRI Thank you, but if you have a reasonable solution, then juat share it, otherwise, please do not comment!

### RE: Friction in a steel ring

I'll take a stab (rather than a jab).

We have a ring tensioned around a circular column.  If the ring has a tension T then the radial line load that it exerts on the column around a circumference line is T/r (where r is the column's external radius).  This is a force per unit length.  So the total radial force between the ring and the tower is (T/r)*(2πr) = 2πT.  To move the ring smoothly down the tower, keeping it perfectly horizontal at all times, would therefore require a force of 2πμT where μ is the coefficient of friction.

This requirement for the ring to be perfectly horizontal at all times is near enough to impossible to meet.  When it is violated the ring will tend to "bind".  I believe that any binding will increase the force required to keep the ring moving downwards, and so the formula above (used with an appropriately low value for μ) is a lower estimate of the force required to slide the ring downwards.

You also ask about the stresses circle of radial force will induce in the column.  This is a fairly standard problem, covered in many text books.  Roark gives comprehensive answers, but as is appropriate in a book like his he does not cover the derivation of the formulae he presents.  (The behaviour of a thin walled cylinder under axisymmetric radial loading is mathematically analogous to that of a beam on an elastic foundation.)

### RE: Friction in a steel ring

https://repository.lib.ncsu.edu/bitstream/handle/1... Take a look at this article. While the article is basing the pressure exerted by the clamp radially on a pipe, with a little forethought you should be able to determine whether or not there is enough pressure to prevent the steel ring from sliding along the pole. Equations 1 thru 15 should be the area to study carefully. From equations 16 thru the end of this article there will be no relevance to your project for obvious reason.

### RE: Friction in a steel ring

Check this article "Force exerted by a band clamp;Dr. Lindsay Robert Wilson ;http://imajeenyus.co". The band clamp has only one screw for tighteness unlike yours which has three screws. The analysis shown in the proposed article can be modified to include three tightening connections and once you have come up for a value of the clamping force(F)you should be able to develop a resistive force to slippage which should exceed the total weights imposed on your clamp. Coefficient of friction of .3 for steel on steel is an accepted value.

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