Lab Report - Axle Friction Engineering Dynamics, Lab Reports of Dynamics

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National University of Sciences and Technology (NUST)

SMME

Lab Report

AXLE FRICTION

COURSE : Mechanics Lab

SUBMITTED B Y : Altaf Ahmad (250282)

SECTION : ME-10 A

Axle Friction

Objective:

The purpose of this experiment is to calculate the friction torque of plain bearings manufactured from different materials and also to compare these values with those obtained from rolling element or ball bearings. We will use four types of different bearings made up nylon, brass and steel plain bearings and one rolling element bearing.

It actually consists of two experiments.

1. Calculation of Static coefficient of friction
2. Calculation of Kinetic coefficient of friction

Apparatus:

Axle is a solid wheel fixed on an axle. The axle is supported by simply plain or ball bearings. The plain bearings are made up of polymer, bronze or ball. An accelerated mass acts with the help of a cord wound around the axel acts under gravity.

Theory:

The shafts are supported by bearings of different types. These bearings can play a very important role in the machine’s performance. As efficiency of a machine and the cots of the bearings are always inversely proportional, a plain bearing can be easily made and require low cost and technology but it provides a very high friction thus comprising on the power of the machine. On the other hand, ball bearings have very low friction and perform really good but their installation and manufacturing requires high standards of technology and they have far less tolerance. So, they require a proper clean environment to avoid dust or dirt.

Formulas and Notations:

Mass of Flywheel and axle combined = M = 30 kg

Diameter of flywheel = D = 30 cm

Diameter of spindle = d = 2.4 cm

Mass which produces rotation = m (^1)

Flywheel and spindle’s moment of Inertia = I

Rotation producing mass’s linear acceleration = a (^) m

For Kinetic Friction:

4. Measure the specific distance ‘s’ and the time ‘t’ required for the mass to reach the floor. Repeat calculation for t 3 or 4 times for m 1 and take its average.

Here:

𝑭𝑭 (^) 𝒕𝒕𝒕𝒕𝒕𝒕𝒕𝒕𝒕𝒕𝒕𝒕 =

𝒕𝒕 𝟐𝟐^

And:

𝑴𝑴(𝑫𝑫𝟐𝟐^ + 𝒈𝒈𝟐𝟐)

Parts Illustration:

Calculations and Observations:

For Static Friction For Kinetic Friction

Bearing Type m 1 𝒕𝒕𝒔𝒔 m 1 t 𝒕𝒕𝒌𝒌 Nylon 5.41 0.255 5.41 12.4 0. Brass 3.16 0.164 3.67 10.6 0. Steel 3.16 0.164 3.6697 14.8 0. Ball Bearings 0.203 0.012 0.234 22.6 0.

Results:

The results proved that in case of plain bearings, the coefficient of friction was higher varying slightly with the type of material but when a ball bearing was used, the friction reduced a great amount.

Conclusion:

It is concluded that if better performance and wear and tear of machine is to be avoided, rolling element bearings should be used as they have much lower coefficient of kinetic and static friction.