If you are a regular visitor to the website you will be aware that Stirling purchased, by proxy, a Porsche RS 61 from the Gooding auction that took place in March of this year at Amelia Island. Stirling’s first outing in his newly acquired car took place and ended rather abruptly at the Monterey Historic races at Laguna Seca in August. The RS 61 span off at slow speed on the warm up lap and ended up facing the wrong way just off the circuit only for it to be hit by a Lotus that came off at the same corner causing substantial damage to the front end of the Porsche.

The car was subsequently shipped to United Kingdom to be repaired by Porsche specialists Maxted-Page & Prill. The aim is to have the car repaired in time for Stirling to race with Ian Nuthall at the 2011 Le Mans support race being run by Motor Racing Legends. We will follow the repair process that the RS 61 will be undergoing over the next few months with regular updates as we head towards next year’s Le Mans.

This first feature uncovers the reason the car went off the circuit, causing Stirling a great deal of concern at the time as it was not immediately apparent as to why the car should spin off the circuit at such slow speed. Andy Prill, of Maxted-Page & Prill, discovered the cause when he stripped the gear box to change the gearing for the Le Man Legend race.

When the oil was drained out they found a single ball bearing in the gear box casing. Once the gearbox had been taken apart they could see that one of the main bearings in the intermediate plate had lost one of its ball bearings. Further assessment of the fully stripped gearbox revealed damage to the first gear. Andy Prill kept going back over in his mind what Stirling had said to him about how quick the incident had occurred. This led him to go back to the gearbox and put the ball bearing they had discovered under a magnifying glass.

This revealed a mark that exactly matched the edge of a gear tooth. Ball bearings are 'glass hard' so to be marked in this manner implied that it must have come under extreme pressure. Andy then had a closer look at the chip they had noted on one of the first gear teeth which revealed the feint outline of the ball bearing. A look at the bearing retaining plate confirmed his rapidly expanding theory as there was also a clear witness mark on it caused by the helical cut gears trying to throw the ball bearing out before it jammed against the teeth. It was then a simple job to put the parts together and replicate exactly what had happened – see images above.

It was just a matter of luck that this incidence happened on the warm up lap, had the car had been going faster the accident and damage could have been far worse. The effect of the ball bearing leaving the bearing retaining plate was immediate, and would have been even more sudden than an engine seizure, causing the back wheel to lock solid and spin Stirling around and off the circuit. When the car came to a halt and was put into neutral, so that it could be moved by the marshals, the pressure came off of the gears and allowed the ball bearing to drop innocently into the bottom of the gearbox case. As nothing obvious was wrong, everybody, including Stirling, thought that it was a case of cold tyres on a damp track.

In a way the fact that the Lotus hit Stirling, causing the substantial front end damage and preventing the car from being used further, was a good thing. If he had simply spun and carried on it would not have been long before the bearing collapsed completely, the consequences of a similar incident at higher speed could have been far worse for the car and Stirling.

Next month we look at the body repair, which requires substantial work, and look at the engine as its striped and rebuilt.

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