Damper calculations 2

[Darkone]

Can anyone help ? I need to calculate minimum wall thickness for pressurised a mono tube damper. What is the equation? This needs to include the max redound force and any couple.

 

[mburgess]

Don't know if this is simplifyingtoo much but if you know your internal pressures it should become a simple hoop stress calculation. Easily found in most basic solid mechanics text's. Off the top of my head is another story.
Hope this helps,
MB

 

[GregLocock]

I think that might be oversimplifying the situation. You'll also get bending loads due to the torsional rates of the mounting bushes, and some rather nasty loads due to the ends.

Admittedly a mono shock is a lot easier to work out than a MacPherson strut.



Cheers

Greg Locock

 

[SusTestEng]

We use high pressure monotubes that are pressurized to 300 psi. How high does the actual pressure get to inside during operation, I have no idea, but I am sure someone here should know.

 

[TravWood]

You will also need to take into account any grooves/threads for seal packs! Bilsteins/DMS/Proflex and many other monotubes have 2mm wall for both shock absorbers and Inserts/cartridges/struts. For some rally inserts they used 2.5mm. Are you using steel or aluminium would be a good first question, all above is for steel.

Travers

 

[Dysus]

You need to establish the spec of the materiali.e. the tube itself is it cds or erw? The mill that supplies the material should able to supply the necessary information at a glance for what you are asking.

 

[Fabrico]

Re: "This needs to include the max redound force and any couple."

Rebound force is never greater than simple spring force.

Wall thickness should address the greatest mechanical loads.

 

[harrisj]

It's possible to design a damper to operate at any pressure you want. The higher the pressure, the smaller the diameter. However, sealing, safety and ease of manufacture probably mean you don't want to go over 25 bar for a car (trucks and military vehicles can run at very substantially higher pressures).
The wall thickness is a function of pressure and diameter, but also needs to consider corrosion, safety factor, and impact from stones and rocks etc (especially for an off-roader). You may calculate that you only need 0.3 mm of wall thickness, but that's way too low for easy manufacture and vulnerability.