David Cox, an expert in thermodynamic was put in charge of doing all the calculations in regards to the speed of the turbine and finding the right materials for produce all the components.
“The fan assembly was initially from a tank engine cooling assembly although in the end we built our own cast magnesium blades running in a fully machined split aluminium hub,” said Murray.
“However, the fan installation was an enormous challenge and the two biggest problems were the mobile skirt system and the strength of the fan blades themselves. We went through four iterations of fan blade material and two iterations of fan hub material to avoid the fan assembly exploding.”
Sealing the underneath of the car also proved to be a challenge.
“The skirts on the fan car were very complex, all skirt material was made from polythene plastic with a PTFE (polytetrafluoroethylene, known as Teflon) sacrificial ribbing strip,” Murray told us.
“The side and rear skirts had stainless steel adjustable leaf spring assemblies for adjusting the skirt to ground pressure to compensate for the suction increase with the rising fan RPM.”
“The front transverse skirt was more complicated as the forces acting upon it were generated by two diverse equations. That is at high engine RPM in any gear the fan exerted a high suction on the rear face of the skirt blade but also at high car speeds the ram pressure on the front face increased independently. To compensate for this compound effect a dual bag system made from tough sail cloth was designed to sit behind the front transverse skirt were designed to be misaligned slightly with the holes in the first bag and the exit holes in this bag were again misaligned in the second bag so that as the car speed forced the blade upwards and rearwards the holes in the bags aligned and the pressure was exerted on the skirt.”
“The fan assembly was initially from a tank engine cooling assembly although in the end we built our own cast magnesium blades running in a fully machined split aluminium hub,” said Murray.
 |
| Water radiator located on top of the engine. |
“However, the fan installation was an enormous challenge and the two biggest problems were the mobile skirt system and the strength of the fan blades themselves. We went through four iterations of fan blade material and two iterations of fan hub material to avoid the fan assembly exploding.”
Sealing the underneath of the car also proved to be a challenge.
“The skirts on the fan car were very complex, all skirt material was made from polythene plastic with a PTFE (polytetrafluoroethylene, known as Teflon) sacrificial ribbing strip,” Murray told us.
“The side and rear skirts had stainless steel adjustable leaf spring assemblies for adjusting the skirt to ground pressure to compensate for the suction increase with the rising fan RPM.”
“The front transverse skirt was more complicated as the forces acting upon it were generated by two diverse equations. That is at high engine RPM in any gear the fan exerted a high suction on the rear face of the skirt blade but also at high car speeds the ram pressure on the front face increased independently. To compensate for this compound effect a dual bag system made from tough sail cloth was designed to sit behind the front transverse skirt were designed to be misaligned slightly with the holes in the first bag and the exit holes in this bag were again misaligned in the second bag so that as the car speed forced the blade upwards and rearwards the holes in the bags aligned and the pressure was exerted on the skirt.”
 |
| John Watson, Lauda's teammate, driving the second Brabham. |