Equalizer Hitch Question

2012Oudoorsman wrote:
---Either way it works good but I feel that an increase in the surface area could make it function great now and during the windy/nasty days.

Based on all I've read, I feel that an increase in the contact area would not result in any significant increase in friction force between bar and L-bracket.

I've done a lot of searching for reports of steel-on-steel coefficients of friction which are dependent on contact area. I've found none. I'm aware that absence of evidence is not evidence of absence, but there should be data available for a friction/area dependency if it does exist.

I did find the following which, IMO, gives a good explanation of why there should be no significant dependency:

Because surfaces aren't smooth on the atomic scale, when you touch two surfaces together only the high points (asperities) on the surfaces make contact so the real area of contact is much smaller than the apparent area of contact.

The reason why the force is approximately independent of area is that as you increase the force you get elastic deformation of the asperities and the real area of contact per asperity increases. If you increase the area you increase the number of points of contact but you also decrease the force per point of contact so the asperities deform less and the real area of contact per asperity goes down.

The real area per asperity is roughly proportional to pressure, i.e. F/A , and the number of asperties in contact is proportional to area A . So when you multiply these together you find the real area of contact, and hence the friction, is just proportional to the applied force.

For relatively soft materials like rubber the approximation doesn't hold, and their frictional behaviour is a lot more complex.

Ron