Timber Framing Journal #71 (March 2004) has an article dedicated to historic queen post trusses. Here's a drawing from that article:
And the introductory paragraph:
A Queenpost Truss typically comprises two posts spread apart by a straining beam joined near their heads and supporting a tie beam (bottom chord) at their feet, and substantially braced by members rising from the outer ends of the tie beam to the heads of the queenposts. These main braces and the straining beam form the top chord of the truss. In service, the queenposts are in axial tension, although they are also compressed transversely between rafter and straining beam at their heads. The straining beam and main braces are in compression. The tie beam is in tension but, because of it's length and any loads imposed upon it, it is also subject to bending. It's common for the queenposts to have top tenons carrying principal purlins or principal rafters in the plane of the roof, but these members are part of the load on the truss rather than essential to its operation.
