Intermeshing Helicopter

I have built the gearbox and rota heads of an intermeshing helicopter. It is made from Technic LEGO and at this point it is just the working gearbox and no body work. The 2 rotary heads work from the same gearbox and turning via a crank handle. One rota head rotates clockwise with the other rotating counterclockwise. The 2 heads sit with a 90 degree difference in angle of approach. Unlike a chinook, the rota heads sit side by side and at an angle of 45 degrees from vertical. The gearbox is made up from a mixture of new and old technic LEGO.