Model A & B

Ford Garage

Rotating Engine Mass

The intent of this page is to compare and contrast the dynamic characteristics and rotating engine masses of different configurations of popular Model A and B engine, flywheel, and clutch combinations.

The Mass Moment of Inertia (MMI) of an object about a given axis is its inherent resistance to rotational acceleration about that axis. An object with a higher MMI will have a lower rotational acceleration than a body with a lower MMI for the same application of torque.

The weight of the individual engine components in the table below is given in pounds.

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Engine Configuration Crankshaft

(lbs)
Crankshaft
Gear
Flywheel Flywheel
Starter
Ring Gear
Clutch
Driven
Disc(s)
Clutch
Pressure
Plate
Combined
Rotating
Mass
(lbs)
Rotational
Mass Moment
of Inertia
1928 'Beavertail' A crankshaft
Multi-disc flywheel
Multi-disc clutch
28.3 0.9 58 3.1 11 101.3 tbd
1929-31 Standard A crankshaft
Multi-disc flywheel
Multi-disc clutch
28 101 tbd
1929-31 Standard A crankshaft
Standard A flywheel
Standard single plate clutch
63 2.5 15 111.5 tbd
1929-31 Standard A crankshaft
Lightened A flywheel (26 lbs)
Standard single plate clutch
26 75.5 tbd
Burlington (counterweighted) A crankshaft
Standard A flywheel
Standard single plate clutch
37.8 63 122.3 tbd
Burlington (counterweighted) A crankshaft
Lightened A/B flywheel (Stipe 37 lbs)
V8 flyweighted clutch
37 11.2 92.5 tbd
1932 Standard B crankshaft
Standard B flywheel
Standard single plate clutch
38 53 15 112.5 tbd
1933 Integral counterweighted B crankshaft
Standard B flywheel
Standard single plate clutch
45.6 120.1 tbd
1934 Pinned counterweighted B crankshaft
Standard B flywheel
Standard single plate clutch
56.8 131.3 tbd
1942 Ford-Köln G28T German B engine
G28T Integral counterweighted B crankshaft
G28T Flywheel
Single plate clutch
needed 40 tbd tbd

The dynamic response of the rotating engine masses is measured by the rotational mass moment of inertia (MMI) of all the components summed together. The calculated contribution of each component is the integration of its mass distribution and the distances from the axis of rotation.

A mass located 'farther' from the axis of rotation has a greater contribution to MMI than the same mass located 'closer' to the axis.

Summary:
As a general statement, the lower the MMI, the less rotational energy the system can store, and the faster the engine will be able to change its rotational speed. In other words, the faster it can spool up and down in speed.

The higher the MMI, the more rotational energy the system can store, and the slower it will be able to change rotational speed (spool up and down).


More related web pages on Ford Garage:

  1. Model A Burlington Forged Counterweighted Model A Crankshaft
  2. Model B & G28T German G28T Crankshaft  
  3. Model A & B Engine Vibration & Crankshaft Balancing
  4. Model A & B Flywheel Variations
  5. Model A & B Flywheel Ring Gear
  6. Model A, B, & V8 Pressure Plates and Clutches

December 2012