Bronze or polyamide bush of the rear beam

Material of the plain bearing of the Peugeot and Citroen rear beam

A plain bearing is considered while replacing the rear beam needle bearing. The plain bearing is often made of plastic or nonferrous metal.

One kind of plastic, used for this purpose, is polyamide. There are a lot of modifications of this material, which are more or less suitable for the plain bearing. More information about this modern and perspective material you can find ion the article polyamide.

polyamide bush

Pulleys and plain bearings for some mechanisms, wheels and rollers for bogies, conveyors are made of polyamide. It is an antifriction material, successfully substituting other materials in the units with higher friction. This material has low friction coefficient and wear resistance.

Accept of polyamide, fluoroplastic can be used in some cases. This material has low friction coefficient too and is well machined on the traditional cutting equipment.

The friction coefficient of the fluoroplastic for steel is 0.04, which is a very low and good factor, but it remains so under the following conditions only:

  • cleanness, sliding surface roughness
  • speed of the surface movement
  • cooling

Under condition, that the sliding speed is not more than 0.66 mpm, the friction coefficient is 0.04. But if the sliding speeds up, the friction coefficient will become twice or thrice higher and won't go down with slowing. It happens for the reason that while speeding up sliding and insufficient cooling the surfaces get warm and some irreversible changes occur. The other reason is the fact, that the fluoroplastic is poor heat conducting material. After 100 passes with extremely high sliding speed the surface may change its characteristics.

So the obstacles for using fluoroplastic for the plain bearings are its deformation under the influence of the outer load, low hardness and poor heat conducting. With the help of adding powdery fillers (molybdenum disulfide, coke, carbonaceous fibre, fibreglass) some inconvenient characteristics can be reduced in a way.

The other material, suitable for the plain bearings, used instead of the rear beam needle bearings, is bronze. Different sorts of bronze are suitable for the plain bearings in a different way.

bronze bush

Although bronze is widely used for the plain bearings, there is a tendency in the past 30 years, to use polyamide instead of it. In spite of its low strength factor, the polyamide is more suitable because of its lower friction coefficient.

You can compare the characteristics of bronze and polyamide with the help of the table.

The comparative table of properties: caprolon, bronze, Fluoroplastic
index *** Polyamide Bronze Fluoroplastic
Density g/cm3 1,15-1,16 7,5-8,9 2,2
Brinell hardness МPа 13-15 65-95 3-6
The tensile strength kgs/sm2 900-950 1500-2800 200-380
Crushing stress kgs/sm2 1000-1100 1500-2800 120-150
Elongation at break % 6-20 3-8 3-4
The coefficient of linear expansion coeff 6,6-9,8хЕ-5 1,8хЕ-5 8-25хЕ-5
The coefficient of friction against steel solzheniya lubrication coeff 0,06-0,08 0,1-0,15 0,02
coefficient of friction on steel without lubrication coeff 0,1-0,2 0,2-0,3 0,04

While comparing fluoroplastic, polyamide and bronze as the rear beam plain bearing material, one may notice that the fluoroplastic and polyamide bearings are more convenient while mounting because of being less subject to wrap and jamming. Besides in case of the bearing's turning inside of the arm, the arm mounting surface will be damaged less.

The bronze bearings can stand higher load, which is especially important for the rear beams of Peugeot Partner and Citroen Berlingo, which transport traffic.

The rear beam plain bearing in the torsion suspension of Peugeot Partner and Citroen Berlingo can be used as a substitute to the needle bearing and prolong the life of the rear beam.