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J.R

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My conveyor drive shaft is keeps on breaking on the middle.

Drive shaft with two gearbox attach to both end of shaft. 25hp motors with speed set to 30 but gear box speed is at 6. Shaft keeps on breaking on the center.

Any ideas why?

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The most likely reason is "fatigue" (high quality close-up images of the broken surface could confirm this).  If you bend a bit of metal back and fourth, it will snap...that's an extreme example of fatigue. 

Fatigue happens when an item is loaded and unloaded multiple times and can cause items to fail when there is very little actual use due to the cyclical nature...it is effectively crack propagation within the lattice structure of the metal's crystalline structure. [its not even "real" cracks, it is incomplete crystals shunting individual atoms across internally within the lattice...they multiply until they become significant.]

It is a little complex in reality, but a general rule of thumb is if the item subject to fatigue is designed to Load/0.3, it should significantly increase the lifespan....and use the yield point for the calcs, not the UTS.

Good luck 

Bruce

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On 4/17/2021 at 3:23 AM, J.R said:

My conveyor drive shaft is keeps on breaking on the middle.

Drive shaft with two gearbox attach to both end of shaft. 25hp motors with speed set to 30 but gear box speed is at 6. Shaft keeps on breaking on the center.

Any ideas why?

Is it possible that your shaft is a rigid shaft supported by more than two bearings so that small misalignment causes fluctuating stress in the shaft, leading to fatigue failure? 

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On 4/17/2021 at 3:23 AM, J.R said:

My conveyor drive shaft is keeps on breaking on the middle.

Drive shaft with two gearbox attach to both end of shaft. 25hp motors with speed set to 30 but gear box speed is at 6. Shaft keeps on breaking on the center.

Any ideas why?

Hi did you solve this problem? do you have any other drive details?

 

3 minutes ago, Sarah Walmsley said:

Hi did you solve this problem? do you have any other drive details?

Do you any images, if it is caused by vibration or misalignment do you have a coupling between the shafts?

https://bit.ly/PumpVibrationEliminated

 

 

3 minutes ago, Sarah Walmsley said:

 

 

 

 

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Without knowing the shaft dimensions, support geometry, shaft material, etc., there is very little that any reader can say other than to guess at your problem. It would help a lot if you would post proper drawing for the shaft and the entire system.

DrD

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