# Shaft Deflection querey

1. Jun 21, 2008

### Analysis

Dear all

I have been given task of to reduce the deflection of overhanging shaft.
shaft geometry is stepped one.If we increase the load acting diameter cross section immediately we can reduce the deflection but our constraint is we cannot change that one.So what i have done ,i have changed the support diameter then the deflection got reduced.My querey is, in general beam deflection equation we are not at all input the support diameter cross section,then how makes the deflection got reduced ?I want to know the theoretical backround for the reduced beam deflection in my case.

Prakash

2. Jun 21, 2008

### FredGarvin

Look at basic beam theory. The deflection of a cantilevered beam is inversely proportional to the area moment of inertia and the stiffness of the material.

If I understand your question correctly, in the general beam equations in classical beam theory, you do influence the support diameter by changing the area moment of inertia.

3. Jun 22, 2008

### Analysis

Thanks you exactly understand my querey
What i was thought so far is if cantilever beam has stepped one and one end supported by bearings and other end is load acting ,the load acting diameter cros section area moment of inertia is included not the whole area moment of inertia while calculating area moment of inertia, now i concluded that we should include section wise all diameter cross section areas moment,and the summation of all these results to be taken.

Prakash