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Strain Gauge Data Acquisition

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CobraCommander View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CobraCommander Quote  Post ReplyReply Direct Link To This Post Topic: Strain Gauge Data Acquisition
    Posted: Apr/23/2010 at 4:04pm
Anybody already do it? I know some FSAE teams have used it.

I'm trying to get something together for mobile testing on the frame but am not terribly skilled with electronics. My basic plan is to make your run of the mill data logger with a 3-axis accelerometer for estimating the current loading of the frame. Then using a series of strain gauges to test the frame hopefully get some data that can then be used for future optimization.

The largest hurdle I've encountered is how to get a useful signal from the strain gauge without the bulky equipment that the college uses. I've found some useful links via google but have yet to try them out. Mostly I'm worried I'll amplify the signal noise as much as the signal itself...

Anyone got any thoughts on the subject?
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Waffles View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2010 at 5:02pm
I would instrument the car with accels, load cells on the shocks, and strain gages on the frame in a controlled environment like a lab.  Do simple dynamic tests or static load tests to validate your FEM strains to strain gages.  Then go out on the track minus the strain gages and apply those conditions to your model to determine strains/stresses.

It's not that you can't use strain gages running outdoors on a track, but its going to be very hard to get good data.  Strain gages are notorious for drifting and being noisy to the point of uselessness, whereas accels and loadcells are proven.
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CLReedy21 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/23/2010 at 5:32pm
Waffles has the right idea.

We did what he suggested with an older car to prove the FE model.  We applied strain gages to the frame and suspension members and did drop tests from a hoist in the lab.
-Chris Reedy
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"Quick with the hammer, slow with the brain."
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collinskl1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/24/2010 at 12:11am
^^^  That's exactly what we do.  We have a wireless unit that we use for very short mobile tests as well, but not for running laps... mainly like a short run over a jump.  It makes for good validation of our FEA.
Kyle Collins
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Nexteer Automotive
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p.lewis View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote p.lewis Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2010 at 4:35pm
SAE paper 2006-01-3626: Structural Considerations of a Baja SAE Frame
 
That may be an interesting read for you.
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mkim44 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mkim44 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2015 at 4:26pm
Hi, I was wondering what model of load cell you used on your shocks collinskl1 and CLReedy21.
Also, I was going to use strain gauges on the rear suspension arms to do some static load testing, but I am worried the displacement will be so small that even the best wheatstone bridge won't do it. Did you need amplification for the strain gauges? If so what did you use?

Thanks
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cozierad View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cozierad Quote  Post ReplyReply Direct Link To This Post Posted: Feb/17/2015 at 8:38pm
We did this in testing a couple of years back after a nasty rear end frame break at Wisconsin in 2012.  

https://www.youtube.com/watch?v=PtBiS_oW1tU#t=52


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