<div class="htmlview paragraph">A new mechanism, combining the Trammel motion with a planetary gear and an epicyclical roller bearing, which will eliminate the side loads and directly transfer the inertia forces to the block, is being presented here.</div> <div class="htmlview paragraph">The obvious advantages of this Trammel engine are its ability to be fully balanced in any configuration with two cylinders or more, its short crank and therefore low mass/stiffness ratio, few bearings resulting in less frictional loss as well as its compactness due to the filling in of utilized structural material around the piston journals. Furthermore the engine take advantage of well developed combustion chamber sealing with minimal seal length/displacement ratio.</div> <div class="htmlview paragraph">This paper will describe this relatively simple mechanism, analyze some of the bearing and gear forces and show the development status of the first prototype.</div>