SPIDER & BEARING GP 1712080 - Caterpillar

Illustration 9 g03727461
Illustration 9 shows the power train performance curves with same MTU 12V4000 engine, but with the TH55-E90 close-ratio transmission. The gaps are reduced or eliminated with tighter gear coverage.Another consideration in transmission selection often involves ensuring the power train can operate at a specific range of the driven equipment. Take the following example. Both power trains have the same engine but with a different transmission.Power train 1: C15 Tier 3 595 hp ("C" rated) engine + CX31-P600 transmissionPower train 2: C15 Tier 3 595 hp ("C" rated) engine + CX35-P800 transmission
Illustration 10 g03727503
In Illustration 10, the performance curves for both power trains are plotted. For better illustration, only the third and fourth gears are plotted for CX31-P600 (power train 1), and only fifth gear is plotted for CX35-P800 (power train 2). As you can see, the fifth gear in CX35-P800 is in-between the third gear and fourth gear in CX31-P600.
Illustration 11 g03727529
In this example, lets assume operation is desirable for the driven equipment at 1400 rpm transmission output speed at full engine power. After accounting for various parasitic losses in the power train, further assume that this power equates to 2711 N m (2000 lb ft) of output torque. From Illustration 11, this operating point is located just to the right of the CX31-P600 third gear curve and above fourth gear curve. This means that this operating point is out of reach with power train 1. On the other hand, this operating point is below the CX35-P800 fifth gear curve. Power train 2 can produce sufficient output speed and torque to achieve the desirable operating point.Ultimately, gear ratio selection is application-specific and is often driven by customer preference. Below is a list of questions that may help determine which transmission is more ideal for the application:
What is the allowable speed range of the driven equipment?
What is the maximum torque rating of the driven equipment?
Is there a specific first gear ratio and overdrive ratio (gear ratio less than 1) requirement?
What is the operating range of the engine?
What gear ratios will be primarily used during operation?
Can the selected power train provide sufficient output speed and torque to get to a specific desirable operating point of the driven equipment?Torsional Vibration Analysis
All rotating machinery systems experience torsional oscillations during operations. The severity of the torsional oscillations is governed by operating speed and excitation frequency of the system. As a result, a system level torsional vibration analysis (TVA) is recommended to evaluate and analyze system reliability. Caterpillar recommends the OEM to review the Application and Installation Guide, LEBW4972, "Vibration" for further details.TH48, CX48-P2300, and TH55 Transmissions: Over the years, Caterpillar has gained considerable amount of TVA experience and knowledge, and has engineered a torsional damper specific for frac application. This damper has demonstrated it can work well to mitigate torsional oscillations seen in typical frac application and installations, and is included with the TH48, CX48, and TH55 Transmissions.CX31-P600 and CX35-P800 Transmissions: The OEM, as the system integrator, is responsible to determine if a TVA