Seek And Ye Shall Find...Frustration.
Probably too many questions for a beginner ...Not at all
1. How Safety Factor (SF) is defined and calculated for a conveyor shaft/pulley? Is it only based on strain/stress, yield, endurance? Safety Factors should not apply but you should add a 'limit of deflection' in your calculations.
2. What is CEMA standard on SF for a non-driving shaft/pulley? CEMA is not a standard but simply a worthy recommendation.
3. What is CEMA standard on shaft delection ( say for a 10"-12" dia shaft)? As1 & 2 above.
4. Is pulley/shaft SF value a comprehensive indicator of an adequate design? Or design analysis should evaluate combination of critical parameters? If so, which ones? This question vanishes somewhere between comprehensive and critical.
4. Should shaft-pulley locking mechanism design ( such as taper lock ) should be part of SF assessment? Yes, if you really need to go town.
5. Are there any provisions in a locking mechanism to prevent backing out of the capscrews during operation? None whatsoever.
6. What is the cause and machanism of capscrews backing out provided that correct torque was applied initially to the capscrews? There was extensive recent discussion on this very subject just last week. Bushes require correctly machined seatings, hardening is an unaffordable luxury in this business. Even with correct machining the seatings can wear down and loosen the fixing. So there is nothing you can do. Even with locking wire or tab washers the drum can still walk across the shaft when the seating gets sufficiently worn.
7. Could axial shift of a non-driving pulley after 3 year of operation be expained by a SF=1.3 ? See 6 above.
By the way, a beginner should not be asked to work on a 254mm diameter shaft. With apologies to CEMA please note the use of ISO units throughout the rest of the known world. ■
John Gateley johngateley@hotmail.com www.the-credible-bulk.com
Locking Bolt Loosening On Pulley Locking Device
The most common reason for bolt loosening is shaft deflection. There are other reasons, but, deal with manufacturing quality control. Sometimes the end disk stiffness is not compatible with the shaft size and deflection. You need to consult a pulley designer for a more indepth review and recommendation. ■
Pulley Spec
Hello David
Design your pulleys for 6 minutes deflection at the locking elements, and a maximum bending stress of 55MPa, and you will not have a problem.
You can ge higher than 55MPa in practice, but I would not recommend this for combined bending and torsion.
Cheers
LSL Tekpro ■
Definition of Safety Factor
I am new to conveyor business specifics, so please forgive my ignorance. I need a quick navigation on the following questions:
1. How Safety Factor (SF) is defined and calculated for a conveyor shaft/pulley? Is it only based on strain/stress, yield, endurance?
2. What is CEMA standard on SF for a non-driving shaft/pulley?
3. What is CEMA standard on shaft delection ( say for a 10"-12" dia shaft)?
4. Is pulley/shaft SF value a comprehensive indicator of an adequate design? Or design analysis should evaluate combination of critical parameters? If so, which ones?
4. Should shaft-pulley locking mechanism design ( such as taper lock ) should be part of SF asessment?
5. Are there any provisions in a locking mechanism to prevent backing out of the capscrews during operation?
6. What is the cause and machanism of capscrews backing out provided that correct torque was applied initially to the capscrews?
7. Could axial shift of a non-driving pulley after 3 year of operation be expained by a SF=1.3 ?
Probably too many questions for a beginner ...
I'll really appreciate your help.
Dave ■