Hand held shear vane troubles 1

[soileater]

Hi there guys,
I have acquired a hand held shear vane made by "Controls" but dont have an instruction manual and all attempts to get this from the manufacturer have failed. I have seen one in operation before and understand the basic theory but maybe one of you have experience with these devices and could explain how it works. It has three different size vanes that one can attach and a dial with 0 to 9.9 N/cm2. Thanks for your input. Iain

 

[mahisub]

Three different sizes are for different levels of shear stresses. This means that for softer clays, you would better to use the bigger vanes to have higher precision. Keep in mind that there are different readings on the handle for different vanes.
I am not sure about the twisting speed, but you can find it in Google. But don't twist it VERY quickly.

 

[mahisub]

Oops,,sorry, the first line is:
Three different sizes are for different levels of shear STRENGHTS.

 

[oldestguy]

Without a manual it is eady to figure how to use it. Some means of measuring torque is needed. If not with the device, use a torque wrench from a machancs suply place.

Then, using the radius to the surface as well as integrating the top and bottom surface areas, you can convert the torque to shear strength.

For a vane with the diameter as half the height,
S= 3T/28*pi*r^3 where T is inch=pounds, r is inches and S is in pounds/sq. in. You can convert to your units please.

This formula is for one end effective. For both ends effective, S = 1.94 * 10^-3 * T

Turn slowly and measure the torque. Then give it two full turns and measure again to get residual strength.