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.

[john rogers]

Why not a "sucker car" like the one that was at the Grassroots Motorsports annual gathering a year or two ago? I think it was a Corvette with a snowmobile engine in the passenger seat location and they had a picture showing the dust plume coming out the top of the car.

On a more serious note, I don't think the strain gauge would work between the rear lid and the body unless there is a way to record the amount of downforce over time. I believe that the down force from the spoiler to the lid will go up as speed does and then force between the lid and body will go up but once the body gets pushed down the force difference will go to zero in that area. That is why race cars record the amount of force on some sort of data logger so it can be read over time.

Small spoilers/wings either front and/or rear are hard to measure but huge ones like the A-Mod cars run are easy to gauge as you can see the suspension squat as spped goes up. At a race a few years ago in Mexicali MX there was a VW Golf with a huge multi level rear wing at at the end of the front straight the nose was pointed up probably 20 degrees or more but the car sat level when stopped. I remember thinking it must be a real handful to drive like that but the guy loved it!