Acceptable deflection of a 25mm solid steel shaft

[Lehane]

I've calculated the deflection of a 25mm shaft to be 2.2mm. Is this too much or is it acceptable?

Fairly basic question I know but it's been a long day!

 

[KENAT]

Shaft of what?

In what context?

How long of a shaft?

What cross section?

...

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Lehane]

Told you it's been a long day!

Circular cross section, solid, and made of stainless steel, with a length 1161.2mm.

It's supporting a bowl of liquid that will be filled up and then emptied a dozen times a day.

 

[desertfox]

Hi Lehane

I would look at the stress in the shaft and then consider the fatigue as the shaft is loaded and unloaded.
Try to get the stres i the shaft below half its tensile strength if possible,then fatigue might not be such a problem.

desertfox

 

[drawoh]

Lehane,

Why does deflection matter to you?

[ol]
[li]Your shaft ought to not break, hence desertfox's remarks, above.[/li]
[li]You have an alignment issue with your bowl of liquid. This will dictate what your acceptable deflection is. You don't need to ask us.[/li]
[li]Your liquid and container have a mass. Your bar has a spring rate. [ω]=sqrt(k/m). Your container full of liquid will bounce up and down and rotate at resonant frequency when it is bumped, or emptied and filled.[/li]
[li]???[/li]
[/ol]

Do you really need to cantilever the thing? I crudely figure that tension/compression structures are around three orders of magnitude stiffer than cantilevers.

JHG

 

[flash3780]

I don't know. How much deflection is acceptable in your device? Deflection only equals failure if it causes something to function improperly.
Stress, on the other hand, is how you determine whether your part will break. For parts under a static load, permanent deflection (yielding) is often the criteria for failure. For parts under a repeated load, the maximum stress is determined by the endurance limit of the material or a fatigue life analysis (cycles to failure).