How Can Gearbox Friction Be Engineered to Fail at Specific Load Weights?

• beattie_03
In summary, the conversation discusses a project to design a balsa wood crane that can lift 1kg but fail at 1.5kg. One idea is to utilize friction in the gearbox to hold the 1kg load when the motor is not running, but allow it to slip into reverse and drop the load when there is a 1.5kg load. The conversation also mentions the use of a DC motor and calculating stall torque, but it is suggested to use a worm drive for better control. Finally, there is a suggestion to use a power screw to find the equation for all components and the ratio between the motor and gearbox.
beattie_03
Hey,

I have an engineering project where I need to be a able to lift a 1kg load with a balsa wood crane, but have it fail at 1.5kg so as to be not over engineered.

Various components need to fail (eg truss, which is easy) but I am trying to work out how to get the electro-mechanical component to fail.

One of my ideas was to utilise the friction in the gearbox to hold the weight of the 1kg load when the motor is not running, but when there is a 1.5kg load and the motor stops running, the friction in the gears will not be strong enough and the gears will slip into reverse and drop the load.

I have gauged that this is possible, but am getting a bit confused with Holding/Stall torque and if I should be calculating this for the motor or gearbox or both.

Any guidance?

Cheers! Sean.

A gearbox is a mechanical torque transformer.
If you use a DC motor then the torque on the stalled output shaft will be proportional to the motor current.

Sorry could you explain further. Essentially (I Think) I want the friction in the gearbox to resist a certain load when the motor is not running. I am trying to work out how to calculate this?

There is no way to accurately predict the friction through a normal gearbox. It is an exponential problem highly dependent on temperature and lubrication. Only with a worm drive could friction lock the gearbox when without motor power.

If you limit the stall current to a DC motor it will fail to lift 1.5kg, but it will still be able to lift 1.0kg. That can be very accurately controlled.

If you can get a small wiper motor out of an old 12V vehicle. They often have a 12V motor with a worm driving an external crank. Consider removing the crank and replacing it with a drum.

the only thing you can take Is a power screw. you can find the equation for all

1. What is the purpose of motor/gearbox calculation?

The purpose of motor/gearbox calculation is to determine the appropriate motor and gearbox specifications for a specific application. This involves calculating the necessary torque, speed, and power requirements to ensure optimal performance and efficiency of the system.

2. How do you calculate the torque and speed requirements for a motor/gearbox system?

To calculate the torque requirement, you need to know the load or force that the motor/gearbox needs to move and the distance or radius at which the force is applied. The speed requirement can be determined by considering the desired operating speed of the system and the gear ratio of the gearbox.

3. What factors should be considered when selecting a motor and gearbox?

The key factors to consider when selecting a motor and gearbox include the required torque and speed, the load and operating conditions of the system, and the size and weight limitations. It is also important to consider the efficiency, reliability, and cost of the components.

4. How can I ensure the motor/gearbox system will perform as expected?

To ensure the motor/gearbox system will perform as expected, it is important to conduct thorough testing and validation using the calculated specifications. The system should also be regularly monitored and maintained to prevent any potential issues.

5. Are there any software tools available to assist with motor/gearbox calculations?

Yes, there are various software programs and online calculators available that can assist with motor/gearbox calculations. These tools use mathematical formulas and algorithms to quickly and accurately determine the necessary specifications for a motor/gearbox system.

• Mechanical Engineering
Replies
1
Views
1K
• Mechanical Engineering
Replies
3
Views
2K
• Mechanical Engineering
Replies
6
Views
1K
• Mechanical Engineering
Replies
5
Views
14K
• Engineering and Comp Sci Homework Help
Replies
2
Views
1K
• Mechanical Engineering
Replies
3
Views
9K
• Mechanical Engineering
Replies
2
Views
6K
• Mechanical Engineering
Replies
7
Views
2K
• DIY Projects
Replies
3
Views
2K
• Mechanical Engineering
Replies
1
Views
2K