Aluminum or Nylon & Mechanics of a spacer.

In summary: Moderator]In summary, the individual is seeking advice on modifying their front suspension system by adding a spacer made of Acetal Nylon. The spacer will experience both compressional and shear stresses, and the fasteners will also experience shear stresses. More information and calculations may be needed to ensure that the components can withstand the expected loads.
  • #1
an1mal_69
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Moderator's note: thread moved from Homework Help forums to Mechanical Engineering forum. Welcome to PF an1mal_69 :smile:

Apologies, this is not homework, but a real world problem.

Homework Statement


Front suspension system, consisting of 2 wishbones supporting a wheel hub via (x2) ball joints at the top and bottom. Other connections are apparent, for steering etc, but not relevant in this instance. The ball joints are secured to the arms with 4 bolts.

The proposal is to template the top ball joint and insert a spacer of around 30mm between the arm and ball joint using extended and uprated fasteners.

I had intended to make the spacer from Acetal Nylon having compressional properties equal to or greater than Aluminum. Certain individuals have questioned the material citing the spacer will be subject to shear stress, I argued the fasteners would be taking the shear loads.?


balljointmock.jpg



If you take the rough diagram into consideration..assume the bottom plate as fixed, and there are (x4) fasteners clamping the spacer in place. If a force is applied to the bar on the upper plate (in any direction) what are the effects/loads on the spacer.?

Many thanks in advance, Nik..
 
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  • #2
Ideally, shear forces should be absorbed by friction in the joint and the fasteners should only see tension due to their initial preload. If the joint slides (thus applying shear to the fasteners) it could be considered a joint failure.

Unfortunately, the coefficient of friction between nylon and aluminum is probably pretty low, especially when compared to bare aluminum on aluminum (which is around 1.0-1.1 I think). This means if you use a nylon spacer, you will need to apply more preload on the bolts to prevent a joint failure (shear sliding).
 
  • #3


Hello Nik,

Thank you for sharing your real world problem with us. It sounds like you are trying to modify your front suspension system and are considering using a spacer made of Acetal Nylon. It's great that you have already considered the material properties and have consulted with others about it.

To answer your question about the effects/loads on the spacer, it would depend on the direction and magnitude of the force applied to the upper plate. The spacer will experience both compressional and shear stresses, as it is sandwiched between the arm and the ball joint. The fasteners will also experience shear stresses as they hold the spacer in place.

To accurately determine the effects/loads on the spacer, it would be helpful to have more specific information about the force being applied and the dimensions of the spacer and fasteners. You may also want to consult with a mechanical engineer or conduct some calculations to ensure that the spacer and fasteners can withstand the expected loads.

I hope this helps, and good luck with your suspension modification!

 

1. What is the difference between aluminum and nylon spacers?

Aluminum spacers are made of the metal aluminum, while nylon spacers are made of a durable plastic material. Aluminum spacers tend to be stronger and more rigid, while nylon spacers are more flexible and can absorb shock and vibrations.

2. What are the advantages of using aluminum spacers?

Aluminum spacers are lightweight and have a high strength-to-weight ratio, making them ideal for applications where weight is a concern. They also have good corrosion resistance and can withstand high temperatures, making them suitable for use in a variety of environments.

3. How does the mechanics of a spacer work?

The main purpose of a spacer is to create a gap or distance between two components to prevent them from coming into contact with each other. This helps to reduce friction, wear, and noise, and also allows for thermal expansion and contraction of the components. The properties of the spacer material, such as rigidity and flexibility, also play a role in the mechanics of a spacer.

4. What factors should be considered when choosing between aluminum and nylon spacers?

Some factors to consider when choosing between aluminum and nylon spacers include the required strength and rigidity, the environment in which the spacer will be used (e.g. temperature, moisture, chemicals), and the weight and cost constraints of the application. It is also important to consider the compatibility of the spacer material with the other components in the system.

5. Can aluminum and nylon spacers be used interchangeably?

While aluminum and nylon spacers can serve a similar purpose, they have different properties and may not be interchangeable in all applications. It is important to carefully consider the specific needs and requirements of the application to determine which type of spacer is most suitable.

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