casuprock
10+ Year Contributor
- 320
- 3
- Apr 13, 2010
-
Exeter,
New Hampshire
I did a quick search and didn't find the answer, so I am posting this information. The weight of the stock 2G drive shaft, including all three sections, couplings, and yokes, is 36 lb with an average diameter of 2.56 inches.
Here's a discussion of rotating mass:
The approximate mass moment of inertia (in si units) of the stock drive shaft is 0.0172 kg*m^2. Revving this shaft from 1000 to 7000 RPM gives a difference of 6000 RPM/60 sec * 2pi rad = 628.32 rad/sec. Let's say this takes 1.5 seconds... (632.32 rad/sec) /1.5 sec gives an average angular acceleration of 418.88 rad/sec^2 . Torque = 0.0172 kg*m^2 * 418.88 rad/sec^2 = 7.2 N*m, or 5.31 ft*lb.
Replacing the stock shaft with a light weight shaft has merit if you're trying to eek out a few extra ft*lb of torque under acceleration. In addition to rotating mass, you can also drop a few dead weight pounds by replacing the stock drive shaft. (The above calculations only consider the effect of rotating mass). Not to mention, by reducing the number of U joints, friction is reduced. In this way, it's a three for one deal, though it is an expensive deal. Engineering materials like carbon fiber are optimal but costly. I'll defer to other posts on drive shaft replacement for this information.
I'm having a carbon fiber 1 piece shaft made by ACPT through Vivid Racing. When you have this done, you send them the stock yokes from your drive shaft and they clean them up and bond them into the filament wound shaft they create to the proper length.
Replacing the stock shaft with a carbon shaft has other benefits like reduction of shock on the transfer case and transmission, better launching, etc due to the torsional stiffness of the carbon shaft. Other benefits include damping properties of the carbon reducing torsional vibration. In conclusion, replacing the stock shaft with a light weight alternative has a number of benefits for torque and endurance of the vehicle. To seek the highest gains, a carbon fiber shaft is required.
Here's a discussion of rotating mass:
The approximate mass moment of inertia (in si units) of the stock drive shaft is 0.0172 kg*m^2. Revving this shaft from 1000 to 7000 RPM gives a difference of 6000 RPM/60 sec * 2pi rad = 628.32 rad/sec. Let's say this takes 1.5 seconds... (632.32 rad/sec) /1.5 sec gives an average angular acceleration of 418.88 rad/sec^2 . Torque = 0.0172 kg*m^2 * 418.88 rad/sec^2 = 7.2 N*m, or 5.31 ft*lb.
Replacing the stock shaft with a light weight shaft has merit if you're trying to eek out a few extra ft*lb of torque under acceleration. In addition to rotating mass, you can also drop a few dead weight pounds by replacing the stock drive shaft. (The above calculations only consider the effect of rotating mass). Not to mention, by reducing the number of U joints, friction is reduced. In this way, it's a three for one deal, though it is an expensive deal. Engineering materials like carbon fiber are optimal but costly. I'll defer to other posts on drive shaft replacement for this information.
I'm having a carbon fiber 1 piece shaft made by ACPT through Vivid Racing. When you have this done, you send them the stock yokes from your drive shaft and they clean them up and bond them into the filament wound shaft they create to the proper length.
Replacing the stock shaft with a carbon shaft has other benefits like reduction of shock on the transfer case and transmission, better launching, etc due to the torsional stiffness of the carbon shaft. Other benefits include damping properties of the carbon reducing torsional vibration. In conclusion, replacing the stock shaft with a light weight alternative has a number of benefits for torque and endurance of the vehicle. To seek the highest gains, a carbon fiber shaft is required.
