58 Chadwick-Helmuth Company, Inc.
Chapter 4 - Installation
NOTE: Generally, for helicopter main rotor installations, the user
may install a magnetic pickup assembly to provide the Vibrex unit
with a necessary azimuth signal. This signal provides a baseline for
taking vibration measurements, in the same way as the photocell
system does for propeller balance operations. Note that the Vibrex
unit uses only a single interrupter.
If the user does not have an applicable Vibrex unit checklist and require
one, contact Customer Support and order it (see Section 1.2 “Product
Support” on page 4).
Photocell Mounting -
The photocell’s distance from (gap between) the
target (interrupter) is anywhere from 7 in. to 7 ft. What they do not say is
the size target required to use it at 7 ft. In most aviation applications the
target tape would have to be so big you couldn't find anywhere to put it,
and it would throw the item out of balance a good amount.
Photocell Tape Width -
Try to stay in a range of between 5 in. to 18 in.
Also, since the photocell requires the target to be in the beam for a
specific time period, try to stay at a small radius. A target tape placed on
the back of the spinner at the 6-in. radius might be 0.5 in. long (width of
tape passing through the beam) for an RPM of 2400. The same target to
provide the same dwell (length of time) in the beam at the 30-in. station
would have to be approximately 2 in. long.
For details on calculating photocell tape length, see “Appendix: Photocell
Taping” on page 157.
To Next Page
Loading...