A Technical & Operational History of the Liberty Engine

by Robert J. Neal

Specialty Press

Reviewed by Rob Baumgartner

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The extremely long production run and myriad of uses will ensure that the Liberty engine takes its rightful place in history.

It was “state of the art” when first introduced and its aim was to standardize the design of aircraft engines. The engineers wanted a design that could be built in several sizes so that it could power a variety of aircraft types. The difference in horsepower was to be obtained by changing the number of cylinders. The only other requirement would be the commonality of a large number of other parts for the series to be successful.

This would result in a high volume, low cost manufacturing structure where the interchangeability of parts between models would also allow each type to be maintained by the same mechanic.

Thus was born the Liberty engine. There were many uses for this motor as it ended up powering machines that travelled by land, sea and air with its military service spanning 43 years. There was a civilian role for the Liberty as well and even to this day, the Liberty is still providing a service.

Robert J. Neal is not a newcomer to the field of writing. In the past he has written three books and had various articles published. His passion is in the field of automotive, aeronautical and marine history.

The work is clearly a labour of love and this hardcover tome consists of 616 pages. It’s all laid out in a logical order which chronologically traces the history of the famous Liberty engine.

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With over 1000 photos, drawings, charts, and diagrams, the book is divided into 14 chapters and a healthy 125 page Appendix. This in itself comprises 8 sections and with a comprehensive bibliography and index, this publication promises much for the reader.

Technical publications such as these can easily fall into the trap of being difficult to read. That’s not the case here. The author conveys his information in a way that doesn’t bog you down. That’s not to say he omits any of the complexities of the subject, it’s just that it’s all explained on a level that doesn’t overwhelm the reader.

For example one learns of the “problem of plug fouling caused by excess oil pressure at low engine speeds…it was controlled by drilling holes in the head of the pressure relief valve and the use of a groove and oil drain holes in the piston skirt”…now that wasn’t too bad was it.

The contents come under the following headings.

• Before the Liberty

The author gives the reader an overview of aeronautical engine design and production. This covers the period 1903 to early 1917 but emphasis is placed upon the wartime years from 1914 to 1917. This is important at it gives some perspective as to the state of engine development, especially at the time when the 1917 Liberty engine was introduced.

• The Birth of the Liberty

It is against the above backdrop that the Liberty was born. We meet the people behind the project, as well as their financial and political agendas. The prototypes are considered along with the hurdles each had to overcome, with all this culminating in the type’s first successful “flight”.

• Early Contracts and the Aircraft Investigations

It is one thing to have a viable product for distribution but you still have to sell it to your chosen market. A group of experts were sent to Europe to gather information for this very task and the results are discussed here which includes the aircraft involved and the early production contracts attained.

• Liberty Production and Late Contracts

Production was now assured with the Packard Motor Car Company being the first producer. Naturally changes were made along the way and these are fully disclosed, along with the one “design change” which related to the oil system. The numerous manufacturers are discussed with many issues coming to light, including the problems with labour. More insight is gained when one reads how the different engine parts are manufactured.

• Wartime Development and Use of the Liberty

This is where the author covers all the later production changes made to the engine. It includes a discussion of the various problems encountered, and the modifications made to fix them. New engine designs are covered and not only are their current usages explained but also those proposed for future Liberty models.

• The Liberty in Colour

There are eight pages of colour that show off everything from data plates to surviving museum examples. Pages are also devoted to sectional and exploded views of the Liberty 12, which come from the first official manual dating from late 1917.

• United States Tank Use From 1917 – 1939

Limited use of the Liberty was made for powering the tanks of the United States and this is covered here. Although not wide spread, it did lead to other countries producing the engine for their vehicles. These Russian and British uses are detailed in a later chapter.

• Post-War Engineering Developments and New Designs

After World War One there were many engineering changes as well as the introduction of new designs. The U.S. Government initiated most of them and this was mainly done under Army Air Service control. The Navy also used the engine and naturally organized modifications for their own needs. Private individuals and companies also had their say and this section relays all those endeavors.

• Allison and the Liberty

This chapter reveals how Allison went from an auto racing enterprise to a manufacturer of precision machinery.  It continues with the relationship set up between the two companies and the engines that resulted.

• Supercharging the Liberty

Not long after the aircraft was first used in combat, it became evident that an advantage in altitude was a highly desirable thing. Naturally an increase in engine power is a logical step towards achieving this aim. Thus the supercharger was introduced to the Liberty and that is the topic for this section.

• Post-War Aero Use of the Liberty – Worldwide

There was always going to be a large surplus of engines at the end of the war and the Liberty was no exception. The Liberty therefore found its way into civilian use with a wide range of countries and aircraft types. We see these applications discussed as well as the various feats that resulted with the numerous aircraft/engine combinations.

• The Russian and British built Liberties

The Russian and British built Liberties are an interesting story as are the aircraft they were fitted to. Not only does the narrative delve into the respective aviation industries of these countries but also their military departments; this being due to the engine’s use in tanks.

• Marine Conversions of the Liberty

The Liberty gained a reputation on water as well, with one of the first commercially built marine units being completed by the C. C. Smith Boat & Engine Company located in Michigan in 1919. It was fitted to a racing boat that same year and won the 1919 Gold Cup race. This is just one of many uses the Liberty performed on the water and these are conveyed in chapter 12.

• Other Uses of the Liberty

There were many unusual jobs that the Liberty performed and these are outlined under this heading. It saw service as a Hollywood wind machine, movie studio site generator, and was even installed in land speed racers.

• Epilogue

A summing up of the career of this famous engine is found in this two page epilogue and the further 125 pages of appendices below round out this colossal piece of work.

Appendix A: Liberty Contracts
Appendix B: Liberty Production
Appendix C: Documented Tests July 1917 through June 1925
Appendix D: Specifications of the Liberty 12, 8, and 6
Appendix E: The Military Life of the Liberty Worldwide
Appendix F: Aircraft that used Liberty Power
Appendix G: The Liberty Engine Illustrated

The above only scratches the surface regarding the information published in this reference book.

The layout is such that each chapter can be devoured in isolation which greatly adds to the readability of a book of this size.

Robert Neal has admirably kept to his aim of documenting the inception, design, production and major uses of the Liberty engine. His collection of statistics is monumental to say the least, and this will be of immense value for any student who wishes to continue this study.

Thanks to Specialty Press for the review sample