LeTuB
Member
I bypass the background physics theory (refer to wikipedia ) : Simply supported beam with central load
In the standard spine testers, a known load is applied to the shaft and the displacement directly gives the spine
we can use the same principle the other way : a known displacement is applied to the shaft and the measured weight gives the spine :
Result :
Plans :
I used scrap plywood, a 5/16 carbon shaft, 2 inserts, 2 field point cut to make screws, and a wood screw to tune the distance between the arrow to measure and the head of the screws to exactly 10mm
some pieces of aluminium to make the arrow support :
support on scale side shall be able to slide (use thread glue to block the screw with a little play)
Calibration table :
Instruction :
turn on the scale
place the shaft to be measures between the 2 supports
zero the scale
push with the finger in the middle of the shaft until it contact the tuning screw
don't move(!!)
read the corresponding weight on the scale
convert it to spine with the table
In the standard spine testers, a known load is applied to the shaft and the displacement directly gives the spine
we can use the same principle the other way : a known displacement is applied to the shaft and the measured weight gives the spine :
Result :
Plans :
I used scrap plywood, a 5/16 carbon shaft, 2 inserts, 2 field point cut to make screws, and a wood screw to tune the distance between the arrow to measure and the head of the screws to exactly 10mm
some pieces of aluminium to make the arrow support :
support on scale side shall be able to slide (use thread glue to block the screw with a little play)
Calibration table :
Instruction :
turn on the scale
place the shaft to be measures between the 2 supports
zero the scale
push with the finger in the middle of the shaft until it contact the tuning screw
don't move(!!)
read the corresponding weight on the scale
convert it to spine with the table