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Don't D-I-Y

Posted on 8. Oct. 2012 - 01:44

There is a wealth of information within these forums and you could also download the Rulmeca handbook, eventually.

Then you will realise that shaft deflection is just a tip of the iceberg.

While it might be gratiying to design a pulley(shaft) from scratch there are time, trouble and costs involved.

Read the literature and then buy out. ■

Re: Shaft Deflection

Posted on 10. Oct. 2012 - 09:35
Quote Originally Posted by louispanjangView Post
There is a wealth of information within these forums and you could also download the Rulmeca handbook, eventually.

Then you will realise that shaft deflection is just a tip of the iceberg.

While it might be gratiying to design a pulley(shaft) from scratch there are time, trouble and costs involved.

Read the literature and then buy out.

I'm usually working on the design of small and simple conveyor belts in order to process minerals or any bulk material (max: 120 tn/h capacity). I know this is a complex issue, however I haven't enough time and resources to study every single conveyor, so when I'm designing a pulley shaft I use a deflection criteria of 0,0016 to 0,0025 rad. I would to know if this method is a good practice when designing simple conveyors.

thanks for your response ■

Re: Shaft Deflection

Posted on 11. Apr. 2013 - 10:02

Hello Monti,

For conveyor pulley shaft, there are two type of deflection: A) Linear deflection i.e. like beam freely resting at ends. This arises due to radial loads. B) Torsional deflection (polar deflection). This arises due to torque being transmitted, if drive pulley shaft.

The pulley designer generally means linear deflection, and so I consider your query is for the same. The linear deflection is talked about in two situations as below:

1) Pulley body is applying radial load on shaft, but it is not resisting the shaft deflection. This is hypothetical situation and so it is called hypothetical deflection. It is very easy to calculate.

2) The pulley body and shaft are single assembly and it deflects as a composite body (structure). This is difficult to calculate, it is big issue and is a subject itself.

It seems you are referring to deflection sr. no. 1). People follow varied norms and practices and consider this value ranging from 4 minute to 10 minute. Its usable value depends upon pulley type, pulley rotational speed, shaft pulley constructional aspect and application (required reliability of the item like power station, or installation of secondary nature, etc.). Mentioning the numerical value here is like touching hornet nest, but possibly you can think of following values for hypothetical deflection:

7 minute for keyed type pulleys for application of limited importance.

5 to 6 minute for keyed type pulleys for higher speed and application of importance.

About 4 to 4.5 minute for pulleys having Ring-feder type locking assembly (of the type generally used for conveyor pulleys). Refer locking assembly manufacturer / supplier for specific case.

The above shaft deflections are at hub centerline, from horizontal. Please note that shaft deflection at ends are not governing in nature. The shaft ends are in double row self aligning spherical roller bearings which have permissible deflection in degree.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science And Application Design For Belt Conveyors (print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■