I believe that OAC means "Ontario Agricultural College" where the design for
this particular pollen trap was developed.  I did a search today on the Web
and discovered some plans for the OAC Pollen Trap at the following address:
http://www.ag.uiuc.edu/~vista/html_pubs/BEEKEEP/CHAPT2/2-20.gif

There is also text in Chapter 2 which explain the construction and operation.
This information is helpful, as are the plans in Jan Tempelman's web site
which he referred to yesterday.  Andy Nachbaur's web site has an "online
publication" called "Golden Harvest" that explains all about how pollen traps
can be constructed and used, but has no plans per se.  After having made my own
pollen trap based on my readings and on plans I found in one of Eva Crane's
books (the big one, I forget the title), and used it for a year (and it worked
O.K.), I ordered a trap from Stauffer's Beehives and Pollen Traps that was
recommended to me as the best pollen trap available on the market.  Having
received that trap and examined it closely, I concur that it is probably the
best designed pollen trap I have ever seen and I look forward to using it this
coming season.  You can get the address to Stauffer's by doing a search in the
BEE-L archives.  I understand, though that Paul Martin (I believe is the
proprietor's name) does not have a telephone and turnaround time can be slow.
I hope this information is helpful.  I didn't list all the web sites to which
I referred above, but they can be easily found by searching the BEE-L archives
at http://listserv.albany.edu:8080/cgi-bin/wa?S1=bee-l

Layne Westover
College Station, Texas, U.S.A.
(Stauffer's is in Pennsylvania, Port Trevorton, I believe)
p.s. there was sure a dearth of information available on the web the last time
I looked, and there's more now, but even more would be helpful if beekeepers
are willing to share their ideas and plans in this area.