Airbox - Making from aluminium

I spent the day making the airbox I modeled out of cardboard from aluminium.  I chose 1.2mm sheet as this was strong enough but also easy to bend into shape. 

The box was bend to shape using MDF as a guide and G clamps to hold.  The aluminium was then bent by hand.

I marked out the 4no holes for the trumpets (55mm holes at 80mm centres) and filed the edges smooth.  I installed the trumpets and put the box on the engine to check the bonnet clearance.  The first few attempts didn’t fit and I ended up cutting off the 20mm lip I left for attaching the lid.  I also had to bend the box more than planned so as to ensure the bonnet didn’t catch.

I decided against sealing the airbox against the bonnet so decided to make a lid for it, again using 1.2mm aluminium sheet.  This is a tight fitting lid that will be held in place with screws and clips.  I will use some adhesive foam to form an airtight seal.  With the bonnet in position the airbox just catches but I couldn’t reduce the height any more or it would restrict airflow in the trumpets.  I can fix some foam to the top of the box to cushion it against the bonnet at a later date.

I have designed this airbox to use the original bike air filter.  I will also install an intake hose from the side and position it somewhere where it will get cold air from (possible infront of the radiator or a vent in the side of the nose cone.

Bend to shape

Sides cut to shape

Lid bent to shape