CheekyChopper,
Download the following pdf file:
http://chinook-helicopter.com/Public...-240-23P-3.pdf
and go to Page 126 of 511 (or Figure 392 (Sheet 1 of 5))
for a picture of what the Chinny Mixing Unit looks like.
If you can pick out the lower assembly (to the Left of the words "Detail A") that is what a 'normal' Mixing Unit may look like!
If you can find manuals for a Whirlwind (S-55) or Wessex (S-58) they have really simple examples.