Australian/New Zealand Luthiers Forum

Hi All - I'd like to build a deflection jig like the one Trevor Gore uses to measure soundboard deflection under a load. I've attended Trevor's modal tuning workshop and watched him balance his 1kg shot bags on top of the jig and always felt that looked a bit precarious. So I'm wondering if I can build a jig using one of the many depth gauges out there, and simply set the weight directly on top of the soundboard? Seems I would be accomplishing the same thing - getting the soundboard to deflect downward in response to the added load, and then measuring the displacement.

Any advice?

Tony R

Hi Tony, I am not aware of Trevor’s flex jig, but I thought mine, as basic as it is, may give you some ideas. I have used it for many years now.
The beam that supports the weight and the dial gauge is movable back and forward and the weight and dial gauge can be moved side to side this enables any size or shape of plate to be tested.
The weight has a lock ring that holds it off of the plate until needed, it is then lowered onto the plate for reading of the dial indicator. Weight amounts can be varied if required.
I also use it to test the flex in braces. As shown, it is hinged to the wall to create a safe space. Cheers Taff

Many thanks Taff - that's an impressive setup indeed:-) - probably more ambitious than I'm looking for. I know one of Trevor's criteria is portability, so he can take his jig on the road to his many workshops. It's simple, light and easy to pack. Thanks for the reply.

Tony

Hi again Tony. Ok you want simple, I can do simple too. This was an early model. It all folds down to a flat pack type looking thing thing. Cheer Taff

Stewmac......TaffMac