Worm gear CAN NOT selft locking

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In summary, the conversation discusses the use of a pump and motor to lift a heavy boom and load in a hydraulic crawler crane. The worm gear is initially believed to be self-locking due to its lead angle, but after removing the motor, it is observed that the worm gear is not self-locking as the boom causes it to rotate. This could be due to wear over time, leading to a change in the coefficient of friction between the worm and gear. The person asking for help is unsure if this is possible and is seeking assistance.
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tendem
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worm gear CAN NOT selft locking !

Good day Sir,
In the 150 tonne hydraulic crawler crane, to lifting the boom and load, they use pump to drive motor. As motor rotated, it make the worm gear rotate together. and the spur gear rotate too. So the winch rotate and the boom is lifted. I know that the worm gear can be Self Locking as the lead angle of the worm is less than the friction angle. But when I remove the motor out of system,heavy boom make the spur gear rotate, and incrediblly the worm gear rotate too. I mean the worm gear CAN NOT Self Locking. So please help me to solve this probem, I think,after long time in service. The worm gear loss ability of self locking due to wear.SO the coefficient friction between the worm and the gear be changed.Is it possible ? Thanks a lot
 
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Welcome to PF, Tandem.
You are way out of my league with this question... as in several orders of magnitude regarding scale. I have never been able to make a worm gear back up, but on the other hand I have never dealt with a load of more than 20 kg. Sorry that I can't help you.
 

1. Why can't a worm gear self-lock?

Worm gears are designed with a helical thread that wraps around a cylindrical gear. This design allows for smooth and efficient power transmission, but also creates a constant force that pushes the worm gear away from the gear it is driving. This force prevents the worm gear from self-locking.

2. Can a worm gear be modified to self-lock?

No, the design of a worm gear cannot be modified to self-lock. The helical thread and constant force are essential for the function of a worm gear and altering them would affect its performance and efficiency.

3. What are the consequences of a worm gear not self-locking?

If a worm gear is not self-locking, it can lead to back driving, which is when the gear it is driving can rotate in the opposite direction. This can cause instability, inaccuracy, and potential damage to the system.

4. Are there any benefits to a worm gear not self-locking?

Yes, the lack of self-locking in a worm gear allows for the gear to be easily disengaged and re-engaged, making it useful for applications that require frequent changes in direction or quick adjustments.

5. Is there a way to prevent back driving in a worm gear?

Yes, there are several ways to prevent back driving in a worm gear. One way is to use a brake or locking mechanism to hold the gear in place. Another method is to use a double-enveloping worm gear, which has two sets of teeth that provide a higher transmission ratio and greater resistance to back driving.

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