×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Force Plate options?

Force Plate options?

Force Plate options?

(OP)
Hello everyone, my I have a Pasco Force Platform (http://www.pasco.com/prodCatalog/PS/PS-2141_paspor...) that i'm using in my research where I drop an 8kg ball on on the plate from about 1.5m. my problem is that the plate surface caved in from the force. does anyone know/use a force platform that is able to stand the force so the surface doesn't break and is able to record 1kHz at least? any suggestions would be great. thank you.

RE: Force Plate options?

have you tried talking to Pasco ?

I noticed that their example was an airfilled ball ... I suspect you're Way overloading it.

another day in paradise, or is paradise one day closer ?

RE: Force Plate options?

(OP)
Looking at their product website, that's the only single axis force platform they have, so I know already it'll have to be from another company. my fix now is that i placed a steel plate over the platform and then i drop the ball on that, but i'm sure you can imagine how much that messes with the data.

RE: Force Plate options?

When you say "cave in from the force" do you mean that the platform dented into the shape of the ball or creased the platform somewhere in between the platform support?

RE: Force Plate options?

It seems like the force plate is a large contributor to the dynamics of the impact. You need a different method to measure acceleration, such as an accelerometer on the ball or a laser Doppler system or high speed camera.

RE: Force Plate options?

I'm unclear what you're trying to achieve. Perhaps you should describe what your actual problem is. For example, if you are actually interested in getting the impact acceleration of the ball against, say, a solid surface, then the force platform might not even get you what you actually want. Why not attach an accelerometer to the your ball? This would directly measure the acceleration.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers


Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com: http://www.engineering.com/AskForum/aff/32.aspx

RE: Force Plate options?

(OP)
Chicopee- when i say "cave in" i mean that the surface of the platform cracked and thee is literally a hole in the center.

3DDave and IRstuff - it's a lot simpler than that, the essence of the test is that I place helmet padding on the force plate, and then I drop the ball on the pads. Using the force VS time graph for the ball hitting the plate without a sample and then the force VS time graph for the ball hitting the plate with sample, I get a force loss % for that pad.

so, now that my research is more of a priority, I need to get a new force plate, preferably one with a stronger surface, and has a sample rate greater than 1000Hz.

RE: Force Plate options?

why not a accelerometer on the ball ? I'd go with the top surface, but you would drill down to the CG.

another day in paradise, or is paradise one day closer ?

RE: Force Plate options?

Does what you are modeling actually behave like that? Aren't helmet impacts from the outside, i.e., the helmet w/head hits something, as opposed to the helmet staying still and the head hitting it? I don't see how the conservation of momentum and energy equations would be identical.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers


Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com: http://www.engineering.com/AskForum/aff/32.aspx

RE: Force Plate options?

(OP)
The accelerator might be an option, but i would really much rather just stick with the force plate for the sake of not changing the test procedure.

The way it's seen is that the force plate if the head, the pad is, well, the helmet, and the ball is the ball. sure, sometimes both the head/helmet are also moving towards the ball, but i'm just trying to see the Force Loss % if the player wearing the pads wasn't moving, and a ball/puck/object hit the head/helmet.

RE: Force Plate options?

Seems to me that you're neglecting the hard shell of the helmet, which is a part and parcel of the protection scheme. The second thing that would seem to be missing is the fact that neither the head nor the helmet are actually flat; it's unclear to me whether your experiment is really equivalent.

I suggest you visit:
http://www.smf.org/testing
http://www.smf.org/stds

or:
http://www.hecc.net/prodtest.html
http://www.soimpact.com/Hockey_Headgear___ASTM.pdf
http://nocsae.org/standards/general/

Your experiment does not appear to conform to the accepted standards for testing helmets for projectile impacts.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers


Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com: http://www.engineering.com/AskForum/aff/32.aspx

RE: Force Plate options?

I'd look at Kistler. Their force sensors are piezoelectric (stiff and capable of high frequency measurement).

RE: Force Plate options?

Agreed. Or PCB.

je suis charlie

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!


Resources