Force Plate options?

[flyramz]

Hello everyone, my I have a Pasco Force Platform (

http://www.pasco.com/prodCatalog/PS/PS-2141_pasport-force-platform/index.cfm#specificationsTab)

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.

 

[rb1957]

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 ?

 

[flyramz]

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.

 

[chicopee]

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?

 

[3DDave]

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.

 

[IRstuff]

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
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[flyramz]

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.

 

[rb1957]

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 ?

 

[IRstuff]

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
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[flyramz]

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.

 

[IRstuff]

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
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Need help writing a question or understanding a reply? forum1529


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

 

[BrianE22]

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

 

[gruntguru]

Agreed. Or PCB.

je suis charlie

 

[tbuelna]

This document might be of help with your testing.

http://www.astm.org/Standards/F1045.htm