The can-am look

It is already well known, that Gary Robison was the hands-on designer of the first generation can-am, but he needed an experienced person to design/style the overall appearance of the motorcycle. Sam Lapointe was the then head of design at Bombardier, and handed the responsibility of determining the overall look of the bike  to young design graduate form Alberta, Ron Poneche, who had only recently graduated in industrial design from the Art Centre College, in Pasadena California. Sam himself was head of design at Bombardier for over 30 years, having started with them in the 1960's,  with his son Denys taking over the mantle and is now Director of Design for all of BRP's products.

Ron 's responsibility was the gas tank, both fenders, side panels and seat profile, along with the overall off-white colour, the yellow and red accent colours and the bold can-am font. All of this work, was done pre 3D computer design and used hand drawings and clay modelling. It was started in 1971 and completed and approved by Gary Robison in 1972.

Having agreed the concept design , it was on to the next step, to design these items for mass production. The side panels over the high mounted exhaust system was made of metal and the other side panel and fenders were made of high-density polyethylene. This material was chosen as Bombardier had a subsidiary company, Roski who had expertise in rotation moulding of polyethylene.  and the gas tank of high-density cross linked polyethylene. This material is ideal for a dirt motorcycle, it is very flexible - see an early can-am brochure with the front fender twisted like a pretzel - dent proof and no corrosion. The fenders had flat sides, to which replaceable decals were applied.

The gas tank also had flat sides with the plan was to apply durable replaceable decals. The polyethylene was designed to let virtually no gasoline vapours pass through the walls of a gas tank, however, enough vapours did pass to cause bubbles under a decal. This was obviously an issue as lining the interior with a liquid sealer would be far too costly for production.  The solution came by a silk-screening process of applying vapour resistant paint to the tank sides. The thin porous coating allowed the vapours to pass through. The down side is that a rider's knees would wear through this thin coating, and if it was a muddy event that could happen in a day. For a supposed quality designed and expensive motorcycle, this was disappointing. Eventually Bombardier returned to decals as the could be easily replaced, restoring the original appearance of the bike.  The other downside of using polyethylene is that  flexibility decreases with age becoming brittle and yellowing.

And what happened to Ron Ponech? After his time at Bombardier, he moved back to Alberta and became an industrial design teacher at the Alberta University of the Arts, becoming Emeritus Professor in 2006.

Rotax motors

All can-ams make use of Rotax motors, be it 2 stroke disc vale, 2 stroke reed valve or 4 stroke.

The 2 stroke disc valve motor was designed specifically for the can-am. It is an innovative design and the extract below from the Military Operations Manual explains its basic working:

Basically, the rotary valve engine performs the same operation as an ordinary two-stroke engine. The only difference is in the location and operation of the intake.

The process begins with the piston starting its upward stroke the air/fuel mixture is drawn into the crankcase form the carburettor via the intake port (the rotary valve uncovers the intake port). At the same time the piston blocks the exhaust and transfer ports and compresses the air/fuel mixture in the combustion chamber (secondary compression).

As the piston nears the top of the cylinder (TDC) the compressed air/fuel mixture is ignited by the spark plug. The burning gases expand and push the piston downward, creating the power stroke. With the piston now descending the intake port is blocked by the rotary valve and pressure begins to build up inside the crankcase (primary compression). The exhaust port is uncovered as the piston continues its downward stroke and burnt gases are allowed to escape.

Near the bottom of the downward stroke the transfer ports are uncovered by the piston and the compressed air/fuel mixture in the crankcase rushes into the combustion chamber. The piston dome combustion chamber configuration and exhaust back pressure prevent the fresh charge escaping through the exhaust port. This also assists in cleaning the combustion chamber of burnt gases.

The advantage of the rotary valve is gained through the short inlet track. The design introduces the mixture in a very suitable position without obstruction to the gas flow that would impair the volumetric efficiency. This intake position also enhances the lubrication of the lower connecting rod bearings. The rotary valves, the opening duration of the intake port is specifically controlled by the disc. Therefore it is possible to determine the maximum possible intake resulting in better crankcase filling.