Run a hole vertically through C and the baseboard
for the pivot, which should be 4-1/2 inches long, so as to project 1 inch
when driven right home. Take some trouble over getting the holes in L and C
quite square to the baseboard, as any inaccuracy will make the lever twist
as it moves. To prevent the pivot cutting into the wood, screw to the top
of C a brass plate bored to fit the pivot accurately. The strain will then
be shared by the screws.
The horns of A should be long enough to allow the outside of the fixed grip
to be 2-1/4 inches from the inside of the handle.
The balance is secured first to the lever by a pin driven through the eye
of the hook, and then to B by a 3-inch screw passed through the ring. The
balance should just not be in tension.
When the apparatus is so far complete, test it by means of a second balance
applied to D. Set the scale-marker at zero, and pull on the D balance till,
say, 35 lbs. is attained. If the fixed balance shows 7 lbs. on what is
meant to be a 5 to 1 ratio, the setting of R relatively to P and Q is
correct. If, however, there is a serious discrepancy, it would be worth
while making tests with a very strong balance, and establishing a corrected
gradation on a paper dial pasted to the face of E.
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