754 
aie 
In the next row, immediately in front of the row of bodies and pistons, 
place the corresponding top caps cf the gauges. 
Now distribute one copper pellet, one rubber centering washer, two pins 
and a spring to each gauge, making three rows of materials. 
Each pellet should have inscribed upon it the number of the gauge in 
which the pellet is to be put. Slip the rubber centering washer over the 
pellet and insert both in the cavity so that the pellet is correctly posi- 
tioned. 
Next, insert the pins into the piston, and slip the retaining cylinder 
over the piston. Remove the piston from the body of the gauge, invert the 
gauge body, and slide the piston into the gauge body. Do not drop the pis-— 
ton. hiake sure that the piston is properly seated, and the pellet is in 
place. 
Screw on the cap, and the gauge is assembled. (A thin layer of grease 
may be applied to the surfaces which rub, if desired.) - 
h. It is necessary to waterproof the gauges when they have been 
assembled. To accomplish this the following procedure should be carried 
OU. 
(a) Sealing the top part of the gauge. Clean off any grease that 
may be present on the outside of the gauge. Wrap one layer of scotch tape 
around the gauge so the join between the body and the cap is covered. Paint 
over with waterproofing (Tygon primer and 2 coats of Tygon black). 
(>) Sealing the bottom part of the gauge. Place one strip of scotch 
tape over the opening at the bottom. Paint with waterproofing. 
(c) After the gauge is waterproofed every precaution should be taken 
to avoid puncture of the watertight seal, When it is necessary to unscrew 
the gauge from its mounting before it is used (which is the case when dif- 
ficulty is encountered in screwing the gauge into the mounting and the gauge 
must be removed to permit cleaning, lubricating, and/or chasing of the 
threads) the body may rotate with respect to the cap and thus destroy the 
seal, Gauges must not be set on their faces; since this may puncture the 
waterproofing over the piston. 
Cleaning the gauge: All parts of the gauge should be carefully cleaned 
after each use. A slight coat of oil should be used to prevent corosion 
of the steel parts. Keep oil off the rubber washer. Remove all oil before 
assembling the gauge for re-use. 
Precautions: When the momentum gauge fails to function, it is nearly al- 
ways due to water leaking into the gauge. If leaks occur, any information 
obtained is unreliable. The instruction found herein is designed not only 
to assist in the proper asscombling of the gauge, but also to assure that 
the gauge after assombly will be and remain watertight until subjected to 
a shock wave.» 
