Calculating Ballast for Optimum Performance

  Tractor weight and ballasting requirements vary depending on tractor equipment, tire inflation, and operating conditions.
  Follow these instructions to determine ballasting requirements
   
Step 1 Determine recommended total working weight and weight split for application ballast.
  Total tractor weight requirement is found by multiplying the tractor horsepower times the appropriate pound per horsepower. Pounds per horsepower requirements vary according to soil and load operating conditions.
   
    Soil Type:   Light   Medium   Heavy    
    lb/hp   120   130   145    
   
  The total tractor weight necessary to maintain the recommended wheel slip range is influenced by soil type and travel speed. The ballast levels are based upon the following speeds (km/h).
   
    Soil Type:   Light   Medium   Heavy    
    Travel Speed:   8.7 km/h   7.7 km/h   7.2 km/h    
   
  If different travel speeds are to be utilized, more or less weight will be needed. Higher speeds will not require as much weight.
   
  In most cases, 130 lb/PTO horsepower will be enough weight to pull heavy loads. Example using an 8320 tractor:
   
      Model 8120 8220 8320 8420 8520      
      PTO hp 170 190 215 235 255      
   
        PTO hp 215 x 130 = 27950 lb (12676 kg)        
   
  27950 lb (12676 kg) is the total tractor working weight that would be needed at 130 lb/horsepower.
  Next, determine how much of the 27950 lb (12676 kg) weight needs to go on the front and how much on the rear of the tractor. Factory recommended weight splits are:
   
    MFWD/Independent Link Suspension   Towed   Semi-Integral   Integral    
    (Front and Rear)   35/65   35/65   35/65 *    
   
    * Front weight requirements are determined by the weight of the hitch-mounted implement. Enough front weight needs to be added to maintain steering control.    
   
  In this example, the 8320 MFWD tractor will be pulling a towed implement. The recommended 35 percent of the total weight should be on the front and 65 percent should be on the rear of the tractor.
   
        Total Front Weight Total Rear Weight        
        27950 lb (12676 kg) 27950 lb (12676 kg)        
        x 0.35 = 9782 lb (4436 kg) x 0.65 = 18168 lb (8240 kg)        
   
  To determine how much weight needs to be added to the front and rear, go to Steps 2 and 3.
   
Step 2 Determine current tractor weight by using the "Tractor Weight Guide" charts by using a scale. Find the chart with the correct tractor model and tire size.
   
  The 8320 with standard MFWD in the example is equipped with 620/70R42 rear tires and has no front weights. The weight guide lists:
   
        Total Front Weight Total Rear Weight        
        9075 lb (4116 kg) 12175 lb (5523 kg)        

 

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Step 3 Subtract current tractor weight (determined in Step 2) from the recommended total weight and weight split (determined in Step 1) and add ballast as required.
        Front Rear        
        9782 lb (4436 kg) 18168 lb (8240 kg)        
        -9075 lb (4116 kg) -12175 lb (5523 kg)        
        707 lb (320 kg) 5993 lb (2717 kg)        
   
IMPORTANT: There is a weight transfer effect when adding front weights. This weight transfer effect is 143 to 151% depending on configuration. For every 100 lb (45 kg) weight added to front axle, approximately 151 lb (68 KG) is added to the front axle and approximately 51 (23 KG) is reduced from the rear axle. (See Installing Quik-Tatch Weights in this section.) Rear weight is added directly to the axle with no transfer effect.
   
Step 4 Adjust tire inflation pressures for optimum performance. (See Tire Inflation Pressure Guidelines in the Wheels, Tires, and Treads Section.) To get optimum performance from the tractor, inflation pressures must be correctly adjusted to gain maximum traction and minimum soil compaction. Ground pressure "soil compaction" is equal to 1 to 2 psi higher than tire inflation pressure.
   
Step 5 The final determining factor of correct ballast is a wheel slip measurement in the field. Under normal conditions wheel slip should be 8 to 12%.
   
  Radar is needed to calculate average wheel slip. When tractor is equipped with radar, wheel slip will be displayed in the vehicle monitor window. Checking wheel slip manually is possible but will only show slip in one area of the field. (See Measuring Wheel Slip-Manually in this section.) Field conditions vary from one area to another. Maintain the correct average wheel slip to maintain optimum traction performance.
   
Step 6 Add more weight to drive wheels if slip is excessive. If there is less then minimum slip, weight should be removed.
   
  NOTE: To extend drivetrain life, never add ballast that results in continuous full power loads below (6.6 km/h (4.1 mph).

 

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