Bombas

Eaton

®

No. 3-409 January 1998

Heavy Duty Hydrostatic Transmissions

Pump and Motor Sizing Guide

Heavy Duty Hydrostatic Transmissions

Heavy Duty Hydrostatic Transmission

2

Heavy Duty Hydrostatic Transmission

Introduction
3

Heavy Duty Hydrostatic Transmission

4

Heavy Duty Hydrostatic Transmission

Introduction:
Selection of the proper size pump andmotor(s) for your transmission application may require one of two methods. The first method is to calculate the “Power Range” of your vehicle or machine. This method is used when the final gear reduction between the motor and load is unknown or the customer wants assistance to select the final drive ratio (see section I). The second method is used when the final drive ratio is specified by the customer(see section II,2). The following is a list of the commonly encountered vehicle and machine performance requirements that are specified: 1) Tractive effort and vehicle speed in the normal working gear range. Some vehicles may have 2, 3, or more operating gear ranges. 2) Drawbar pull and vehicle speed in the normal working gear range. 3) Gradeability and vehicle speed in the normal working gearrange. 4) Line pull and line speed for a winch. 5) Shaft torque and shaft speed at the output shaft of a gearbox. The above factors must all be maximum in value and taken at maximum applied input power.

ρ = Coefficient or rolling resistance GVW = Gross vehicle weight (lbs or Newtons) Note: Values of r can be found in universally accepted tables of coefficients of rolling resistance for variousground contacting apparatus and ground conditions, such as rubber tires or crawler tracks . See Table 7, page 11 for representative values. 3. If the maximum vehicle gradeability and maximum vehicle speed in the working range are specified, the vehicle Power Range can be computed from the following formula: (See Fig. 2b) PRv = (TE)(Vs)/(C1)(Er), where: TE = (GVW)(sin q)+(RR)(cos q) q = Tan-1(G/100)or = Arctan (G/100) TE = Vehicle tractive effort required to ascend the grade q = Grade Angle (degrees) G = Gradeability (percent) 4. If tractive effort, drawbar pull, or gradeability cannot be provided, the Power Range must be found from knowledge of the vehicle operation. Eaton recommends that all vehicle propel applications be sized such that wheel or track slip be attainable (exceptions mayinclude an asphalt compactor or certain personnel carriers). (See Fig.2a) PRV = (TE)(Vs)/C1(Er), where: TE = (Wda)(µ) TE = Vehicle tractive effort to slip the drive wheels (or track) Wda = Maximum weight on drive wheels (or track) µ = Coefficient of traction (friction or adhesion) between wheels (or track) and ground (use the maximum value for vehicle operating conditions) Note: Values for µ can befound from universally accepted tables of coefficients of traction for various types of ground contacting apparatus and ground conditions. See Table 8, page 11 for representative values. 5. If output shaft torque and output shaft speed are known, the Power Range for a machine can be found by the following formula: (See Fig. 1) PRm = (Ts)(Ns)/C2(Er), where: PRm = Machine Power Range Ts = Maximumshaft torque (lb-in or N-m) Ns = Maximum shaft speed (RPM) C2 = A constant to convert to units of power. C2 = 63025 to convert to HP and 9549,3 to convert to Kw.

I. Power Range Calculations
1. When maximum vehicle tractive effort and maximum vehicle speed in the normal working range are specified, the vehicle power range can be calculated using the following formula: (See Fig. 2a) PRv =(TE)(Vs)/(C1)(Er), where: PRv = Vehicle Power Range TE = Maximum vehicle tractive effort in the normal working range (lbs or Newtons) Vs = Maximum vehicle speed in mph or kph C1 = A constant to convert to units of horsepower or Kilowatts C1=375 to convert to hp and C1=3600 to convert to Kw Er = Final drive ratio efficiency 2. When maximum vehicle drawbar pull and maximum vehicle speed in the working...