Reducing deflections on a double cantilevered tube 1

[cyberohm]

I need to reduce the deflections on both ends of a 10" diameter by 10 foot long tube. I was wondering if I were to place a rod in tension on the inside of the tube that reacts on each end of the tube would I accomplih my goal of stiffening the tube. I cannot place any stiffening elements on the outside of the tube since it rotates about its center axis.

 

[Ron]

Using a rod to put the tube in compression will not reduce the end deflections.

Consider using a different material to reduce the self-weight, increase the moment of inertia, or provide linear stiffeners on the inside face of the tube.

 

[msquared48]

Put a smaller tube or pipe inside, and weld the two together.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[RFreund]

Fill it with concrete?

EIT

http://www.HowToEngineer.com

 

[MiketheEngineer]

Use a bigger/thicker tube??

 

[msquared48]

Skycrane?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[rb1957]

a thicker wall ?

an interference fit inner sleeve ?

but how is the end of a cantilever deflecting ? ... if it's cantilevered slope is zero ??

 

[BAretired]

A thicker wall as suggested by rb1957 is probably the best answer.

A tensioned rod will actually increase deflections if it is centered on the tube at each end because it operates at a variable eccentricity in the central region.

A tensioned rod located above the c.g. of the hollow section will tend to cause more compression in the top fibres than the bottom fibres. In the absence of external load, such a beam would deflect upward. When external load is applied, the combined deflection would be less than a similar beam without the rod.

BA

 

[BAretired]

If the beam is a simple span instead of a cantilever, the tensioned rod should be below the c.g. of the section. The eccentric moment would offset part or all of the deflection dur to external load.

BA