11. The following procedure is to be observed when assembling wigwag mechanism:

a.   First assemble end castings, bearings and armature to base casting with bearings in perfect alignment.  Do not force or spring end castings into position to obtain alignment of holes for dowel pin (Ref. 6l).  In some mechanisms the existing dowel holes may not provide perfect alignment of bearings and it may be necessary to re-ream them and install oversize pin or to drill new dowel holes after the end castings have been tightened to the base casting.  The armature must move with perfect freedom.  Plug unused dowel holes.

b.  Install flag holder casting as follows:  Invert the mechanism on the testing table in an approx-imately vertical position and secure it in this position so that it will not move.  Attach the special protractor, which has been provided for this purpose, to the end casting by means of the striker hub pivot screw holes.  Attach the pointer to the armature shaft and set it to read zero on the protractor scale.  Move the armature by hand and allow it to return gradually to zero by gravity.  If bearings are perfectly free a zero reading will be obtained after movement in either direction.  Install the flag holder cast-ing and tighten screws just tight enough that casting can be twisted on the shaft.  Install taper pin (Ref. 96) and drive it just tight en-ough to bring the holes into alignment.  Install the “Test Banner” which has previously been per-fectly balanced.  If the flag holder casting is properly located the pointer on the protractor will read zero and the flag holder casting screws can be tightened securely and taper pin driven firmly.  If the reading obtained is not zero, remove the taper pin, locate the casting as re-quired and tighten screws (Ref. 59).  If the difference in the alignment of the taper pin holes is not too great, ream with taper pin reamer and install oversize pin.  If the banner is perfectly balanced a zero reading will also be obtained if the banner is rotated one-half turn in the flag holder casting.  Remove banner when above adjustments are complete