Strain gage for, measuring downforce Options

[Randal]

Anyone know of a strain gage that measures in lbs or kg's that I can use to measure the downforce of my new rear spoiler. I plan on mounting it underneath the truck lid between the lid and the fiberglass frame. Like where the arrows are pointing:



I figure if I can find something that reads the downward force I can just set it up with a video camera pointing at the gage, drive down the freeway. with the car on the trailer and get some readings.

[type11969]

I would think that in order to get decent readings, you would have to put the load cells in series with the uprights . . . in other words the uprights would have to be cut. Otherwise the only load you would read in the load cell was if the spoiler was deflecting locally in the region of the load cell . . . and that would still be a bunk reading because the load would be shared with the uprights. Now you could potentially epoxy some strain gauges on the uprights and come up with a load based off of the output, the cross sectional area of the upright, and the geometry of the spoiler/uprights, but because the loading probably isn't purely compressive on the uprights, you are not going to get a true reading unless you go to some effort. Like multiple strain gauges around the periphery of both uprights to resolve the force and a datalogger. I guess it all depends on how accurate you want the result to be.