Formula 1 & NASCAR Driveshafts - Driveshaft 201

In our previous articles on the racing driveshaft, Driveshaft 101 (Dec. '07) we examined the environment that the driveshaft operates in and the materials and components from which a driveshaft is built. In Driveshaft 102 (Jan. '08), we discussed the basics of measuring the driveshaft and inspecting it for damage.

Now let's discuss the concept of driveshaft management and how we can apply Formula 1 and NASCAR team parts management techniques to your race car to prevent failures on a $5 budget. We'll look at why the racing driveshaft needs regular replacement, how NASCAR teams manage their driveshaft needs and how you can use their methods to improve the reliability of your race car and win more often on Saturday night.

The driveshaft in your pick-up truck is designed to give many years of dependable service on the street. The street driveshaft is constructed of robust thick tubing and is capable of handling occasional massive loads at low shaft speeds. But most of its life is spent with little stress just going to the grocery store. It's unlikely to ever need full replacement.

If it needs servicing, typically only after 100,000 miles of hard use over a period of 10 years, it will start making noises that will eventually get your attention. At worst, if it eventually fails, you will probably just have a long walk home.

The driveshaft in your race car is also built to give dependable service in its normal application, but its design criteria are entirely different. The racing driveshaft is constructed of thin wall tubing and each component is carefully selected for light weight. This combination of features is better for smooth and efficient high-speed operation.

The racing driveshaft requires regular inspection and routine replacement because it spends its life constantly at high loads and high speeds. Catastrophic failure of the racing driveshaft will result in a wrecked race car and possibly serious driver injury or death.

When most of these situations occur, the result is called a driveshaft emergency or 911. Regardless of the reason, the need for a replacement driveshaft is normally evident just before the team has to leave for the next session, race, test, or appearance and pandemonium ensues until the problem is resolved. If two or more of these situations occur in a week, even the best teams can be brought to their knees.

At its basic function, the driveshaft is a simple connector linking the transmission to the rearend. But without one in place, the car slows dramatically. The strongest engine or the trickest suspension setup will not overcome a driveshaft problem. Any vibration that the driver feels will sap his confidence and reduce him to just driving around, hoping he can stop before it blows up and he crashes. He becomes totally non-competitive and wimpy. So driveshaft management is an important part of driver management that every team must plan for.

At the professional level, a multi-car NASCAR team will compete each week with two to four transporters in the garage area at the track carrying primary and back-up cars for each car number. Each of those cars will arrive complete with a driveshaft installed. Additional driveshafts will be carried on each transporter as spare parts and there may be an extra shaft stowed on each team's pit crash cart for in-race emergencies. The total number of driveshafts on-site on race day numbers in the hundreds.

But most of those driveshafts will be of different lengths with specific slip yokes to suit each team's engineering combination. A team must plan to have enough of its specific shafts on-site to overcome any problems. The trackside parts truck or the local parts store will not have a suitable replacement. Missing a race because some one forgot to load enough spare driveshafts is not an option.