Polyurethane has replaced both rubber and metal in several components used in the modern car. The properties attractive to the design engineer have again been the general wear and tear characteristics coupled with oil and fuel resistance. The remote control gear change mechanism on many car are subject to considerable vibration and can be the source of irritating noise. Wear on the ball joint can also lead to a less positive action. Both these effects can be minimized by the covering of the balls with polyurethane or by the use of polyurethane housings. A further advantage in the case of the ball joint is that no accurate machining of special mating surfaces is required. If the socket and ball are both metal they require accurate machining. The polyurethane housing eliminates one surface completely and the elastic nature of the material overcomes the necessity of the machining the ball itself to highly accurate dimensions. The gear change mechanism shown is for floor-mounted levers. Gear change mounted on the steering column generally involve a highly articulated machanism, and the use of polyurethane housings in all the ball joint can reduce metallic clatter to a minimum and provide a cushioning effect on the system.
Thursday, April 28, 2011
Monday, April 25, 2011
Polyurethane tires are used on rotary screen plant
Polyurethane tires are used on rotary screen plant. Rotary screen plant is used extensively in the washing and grading of gravel and sand and also for heat drying of road stones. Other user include the preparation of natural and artificial fertilizers. Where the drum loading and temperature are such that the natural rubber can be used the substitution of polyurethane gives the expected advantages of higher load capacity and longer life. In many case however steel rollers have been in the past used in place of natural rubber due to the high loading required. In these case because of the highly abrasive environment, severe wear can take place both on the steel roller and the steel track on the drum itself. This wear leads to increased vibration in the plant which in turn can result in fractures of welds and rivets. To avoid serious damage the drum tracks have to be remachined at intervals during which the plant is inoperable. More recently these steel rollers have been successfully replaced by polyurethane tires in a number of cases. Taking a typical plant, for example, having an output of 50 to 60 tons per hour of washed gravel the weekly output is equivalent in value to ten times the cost of a set of polyurethane tires to replace the steel tires. The use of polyurethane tires reduces the vibration considerably and substantially reduces the maintenance time required. It also considerably reduces the noise level. In certain case the rotation of the drum can be carried out using polyurethane tires, with a further reduction in vibration.
Polyurethane tires : Overhead cranes
Polyurethane tires are being successfully used on overhead cranes. In these instances the conventional flanged wheel and rail can be replaced by a polyurethane tires which runs directly on the top girder or structure to which the rail would previously be fixed. A polyurethane side rollers is used at the same time to prevent undue sideways movement. The crane is driven by power transmitted througth the tires and the overall result is a noticeable reduction in noise and vibration. Noise elimination is an important factor in modern workshop, and reduction of vibration result in saving on maintenance cost.
A similar use for polyurethane tires is on sewang plant settling tanks. The conventional method is the use of steel wheels running on the circular track, both wheels being driven by a fairly complicate drive mechanism. The substitution of polyurethane tires for the steel tires gives greatly increased traction and allows the replacement of the normal drive mechanism by a single motor on one wheel. This still gives better traction than by driving the two steel wheels separately, especially when the plant is operating in wet condition.