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| awemawson:
I'm puzzled :scratch: In my chuck gripping force gauge there resides a load cell in a cylindrical format. It's connections are a conventional bridge with two power connections and a pair of differential outputs, so nothing fancy there. What puzzles me is how you place the necessary strain gauges on something suitably shaped to deform in a controlled manner that it gives readings when gripped in either a three jaw or two jaw chuck, so has either three or two point contact with the outer surface of the cylinder. The load cell incorporated in the gripping force meter is externally just a plain cylinder giving no clue as to it's internal construction. Pictures of the device in this thread : http://madmodder.net/index.php/topic,10608.0.html |
| sparky961:
You can't just use your finger to see how hard it's gripping? :poke: (Sorry, couldn't resist) |
| DMIOM:
Andrew - it isn't effectively just acting as a pressure gauge is it? Dave |
| awemawson:
Dave that's possible I suppose. It would have to be a relatively thin walled tube with a diaphragm on which the strain gauge sits, all filled with a fluid, but there is absolutely no sign of a means of filling. I did wonder if it is a series of concentric flextures each with a strain gauge and the strain gauges wired in series but no amount of googling for radial load cells comes up with anything similar |
| DMIOM:
The outer cylindrical skin must be cable of accepting/transmitting the deformation, and if there are no specific 'target' zones then, if not pressure based, then I could envisage a couple of other concepts: One method might be to have a length of spring steel sheet, like those used for lead-screw guards, one end anchored to the skin and the other, monitored, end to an arbor - as the cylinder is squeezed the spiral will try to wind up? Alternatively, I wonder what results you would get if you wound a lap of strain gauge wire on a compressible cylinder, just like a single-layer-winding solenoid; you would then face the challenge of slipping that inside a compressible outer sleeve and filling the annular void with a medium that ensured the pressure was transmitted to the inner cylinder & coil.... Or maybe there's no coil -might it be an air-spaced cylindrical capacitor - one plate = fixed inner arbor, other plate = deformable skin? However, I've just been back to look at the pictures in the original thread - and there are specific two-jaw and three-jaw adapters with pads for the jaws to bear on. The adapters' purpose could be to avoid marking the head but they look to have sprung fingers with "pips" to engage in specific dimples on the measuring head; hence pressure will always be at the same specific points on the circumference - so maybe a set of six strain gauges and appropriate adapters could accept 2/3/4/6 jaw chucks? So, maybe it isn't a generic "any point on the circumference" cylindrical strain gauge at all! Dave |
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