How to build a simple wind tunnel force balance?

[foxkilo]

I have constructed a wind tunnel with approximately 15 x 15 in. cross-sectional area test section.

Where can i get some ideas/plans to build a simple force balance that can measure lift and drag forces simultaneously?

Currently I'm using a single-axis button load-cell setup to measure drag. How to design a mounting solution for another load cell to measure the lift force? Or there are much better ways of doing this, e.g. using strain gauges? :confused:

Need not be too accurate; this tunnel is intended for educational purposes only. Any help is appreciated, thanks.

[ank_gl]

Need not be too accurate; this tunnel is intended for educational purposes only. Any help is appreciated, thanks.

:rolleyes:
hang the model from a spring scale

[foxkilo]

OK, I need enough accuracy to run experiments such as plotting CL and CD vs. angle of attack. :biggrin:

I'm trying to use load cells or strain gauges that can be hooked up to digital readouts.

Need some mechanical contraption that can isolate the lift and drag forces as much as possible...??

Like for example, I'm currently using an L-bar pivoting at the intersection of the L, model mounted on the tip of the longer end of the "L", and load cell placed under the short end. Drag forces pull the model back, the L-bar pivots and applies a load to the load cell... But this method only measures DRAG... so I have a one-trick pony here...

[ank_gl]

Obviously, you ll be putting this L section somewhere, just put a weighing scale below it, difference in weight gives u the lift.

Again if size of the weighing scale is an issue, you can use a platform & use load cells below it(at least three, & of course a bit of calibration), to see the vertical force.

hey, may I know what does the model look like?