A closer look at some very trick driveshafts
When you consider how much time and money goes into building a rig, you can't help but wonder what part (if any) will fail on the trail. Some say the best way to prevent breakage is to over-build it so it simply cannot fail. This overzealous approach to building works well ... to a point. Let's say you've beefed up each and every part of your drivetrain. Wouldn't the weak link eventually move closer and closer to the source of torque? The answer is yes, and the results wouldn't be good. We believe the worst-case scenario would be a snapped crankshaft. Though we haven't actually seen this happen in real life, we have seen numerous transmission input shafts, intermediate shafts, and output shafts grenade under severe use. During competition, this type of complex failure is totally intolerable, especially when you're under the gun at an event such as Top Truck Challenge. The fast-paced roll-out at TTC leaves little time for repairs between events. Experience a complex failure during, say, the Frame Twister, and it's pretty much game over. That's why we had the experts at Pat's Driveline install a "weak link" into our Mega-Titan's drivetrain.
PowerTrainSavers are a patented over-torque protection device built of high-quality steel. The unit installs right into your new or existing driveshaft, and works on a system of three shear pins, which are called Torque-Fuses. These Torque-Fuses have a specific shear value rated in lb-ft of torque. When an over-torque event occurs, the Torque-Fuses shear just prior to pretzeling the driveshaft or snapping the axles, gears, or differentials.
Here you can see the Mega-Titan's entire rear driveshaft assembly. Notice how the PowerTrainSaver is mounted up high near the transfer-case output shaft (arrow). This is an ideal mounting location because it's well above the bottom of the framerails, and in most scenarios still out of the mud and muck. This shaft features a Bigelow/Cornay 40-degree CV joint rated for 2,000 lb-ft of continuous torque. Unlike a conventional double-cardan joint, the Bigelow/Cornay joint uses a roller-bearing centering assembly instead of a ball/socket friction-type assembly. Most other manufacturers' CV joints flex to about 35 degrees prior to binding. This setup will flex up to 40 degrees before binding and delivers a true constant velocity through its entire range of motion. This enables a much smoother-running driveshaft as well as allowing for extreme angles. The double-cardan-type centering device found in most CV applications is actually too small to handle high torque loads at high angles. A Bigelow/Cornay joint provides superior strength, concentrating the torque load inward towards the center of the joint, a much better setup for extreme-angle and high-power applications. These joints are also said to last much longer than traditional double-cardan-type joints.
As you can see, we were able to shear our first set of fuses in the Mega-Titan. These fuses were rated for 2,000 lb-ft of torque. We replaced these with 2,500-lb-ft fuses. This represents a 25 percent increase in strength.
After shearing the fuses, the unit freewheels on an internal support bushing and pin, which keeps the driveshaft in place rather than falling on the ground and causing further damage. Repair is just a matter of backing off the nuts, removing the broken Torque-Fuse halves, and replacing them with a new set of Torque-Fuses. Each set of Torque-Fuses costs about $100. In about 15 minutes you are up and running again, eliminating downtime and increasing your chances of winning a competition.
The front driveshaft for our Mega-Titan, like the rear, features a Bigelow/Cornay 40-degree CV joint. This shaft was built with some of the most innovative driveline products in the automotive industry. Its design sports a 1350 "Lube for Life" Life Quality Gear brand U-joint and a 5-inch-travel Elbe roll-formed slip spline for high load capacity and reduced stress risers. Additionally, it features a nylon-coated splined sleeve for reduced sliding friction force and longer life. The spline cover is also sealed to protect the slip spline, retain lubrication, and prevent contamination.
This is the lower portion of the Mega-Titan's rear driveshaft. It features 4 inches of spline travel with a tubular steel dust cover that extends three-quarters of the way up the slip. This enables the use of two individual slip seals--much better for keeping grease in and contamination out.
Here is the rear shaft cut in half. Notice how Pat's Driveline used seamless 0.120-wall tubing for the main portion of the shaft. This is roughly twice the wall thickness of most OE driveshafts. Thicker wall material equals higher overall strength. However, the thicker material also requires greater welder heat to achieve adequate penetration. Luckily, Pat's Driveline has a whole team of experienced welders to ensure product quality. Because Pat's is located in Canada, be sure to give an accurate tax ID number when you place an order with them--believe us, UPS will not deliver to the U.S. without one.