×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

How to calculate shock absorber constants from known c and k values

How to calculate shock absorber constants from known c and k values

How to calculate shock absorber constants from known c and k values

(OP)
We are trying to put a spring-damper system on a drone to act as landing gear (very small scale, only about 300 grams total). We created a MATLAB simulation to describe spring and damper constants, taking into account drone weight, free fall height, and stroke length of the spring-damper. The simulation tells us k constants, c constants, damping ratios, and compression lengths for an input maximum acceleration, stroke length, mass, and fall height. Those are the constants we then need to find a spring damper (aka shock absorbers) for. The issue is, the datasheets associated with commercially available shock absorbers don't have these constants. I have linked two datasheets for reference.

One datasheet we have found uses constants of: Max in.-lbs/cycle (Nm/cycle), Max in.-lbs/hour (Nm/hour), Max Velocity in/sec (m/sec), and max reaction force lbf (N). In this case, what is the meaning of these variables? i.e. is Max Velocity an impact velocity? That would be perfect for our free fall application. Or is it velocity of the stroke of the shock absorber? How do we take c, k, and damping ratios and calculate these values? Datasheet found here: https://www.toolots.com/ea-non-adjustable-hydrauli...

Another datasheet uses different variables: Load (kg), Max absorption energy J (kgf * m), Speed Range (m/s), and extension force N (kgf). In this case, is the Load a continuous load? Is the speed Range the speed of the physical stroke? Is the extension force a direct F = k*x relationship? Datasheet attached.

Hopefully you can either give me some advice on how to approach these variables or some equations on how to calculate them. Any help is appreciated. Thanks!

RE: How to calculate shock absorber constants from known c and k values

Your first one says 100N at 2 m/s, therefore c is 50 N/m/s

It may not be linear but it'll be sufficiently in the ballpark. Frankly these little ones rely on friction as much as damping.

Personally I think you'd be better off with a bit of foam wrapped around your spring.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close