Tractive Effort & Power

(of Steam locomotives)

The Tractive Effort of a steam locomotive can be calculated from the formula:-
(Normal locomotives only. Not appliable to compound locomotives.)

Tractive effort equation
where:-
K = Factor for losses ($)
P = Boiler pressure
D = Cylinder bore
 
S = Piston stroke
W = Driving wheel diameter
C = Number of cylinders

 

The Power output of a steam locomotive can be calculated from the formula:-

Power equation
where:-
K = Factor for losses ($)
P = Boiler pressure (PSI)
A = Area of piston (sq.ins)
 
S = Piston stroke (ft)
N = No. of power strokes per minute (#)
 
($) Loss factor for cutoff, pressure drop in steam pipe, heat losses etc
(approx 0.75 at 50% cutoff, 0.80 at 78% cutoff, 0.85 at 90% cutoff)
(#) 2 per cylinder (for double acting pistons) x driving wheel RPM

 

Tractive Effort and Power Calculator
Enter input values in boxes below and click 'Calculate'
Select English or Metric units for each input parameter
The equivalent converted unit is shown in the other (grey) box

  English Units Metric Units
Pressure P: PSI kPa
Bore D: ins m
Stroke S: ins m
Wheel dia W: ins m
No.of cyl C:
Loss factor K:
Speed: mph kmph
Tractive Effort: 0 lbs 0 kg
Wheel RPM: 0 RPM  
Power output: 0 HP 0 kW
Note: Simple formulas using +-*/() may be entered if desired,
not just straight plain numbers.
1kg = 2.2046 Pounds
1 HP = 0.7457 kW
100 kPa = 14.5038 PSI
1m = 39.370 ins = 3.2808 ft
1 km = 0.6214 miles

Typically use K=0.80 for saturated engines, K=0.85 for superheated engines.

Note the accuracy of these calculations is not necessarily exact, and figures calculated here may vary from results published elswhere. They are calculated here from the formulas above to 3 or 4 significant digits only.

Disclaimer: Results to be used at your own risk. Calculator provided for your personal use only.