Diesel Engine Indicator, De Juhasz Design – ca 1938


This diesel engine indicator was based on U.S. Patent Number 2,040,082 issued to Kalman John De Juhasz of State College, Pennsylvania on May 12, 1936. An engine indicator is an instrument for graphically recording the pressure versus piston displacement through an engine stroke cycle. Engineers use the resulting diagram to check the design and performance of the engine. Engine indicators were originally developed for use on steam engines, and Mr. De Juhasz's design is one of many adaptations of steam engine indicator designs for use on diesel engines.

The device consists of a piston within a cylinder as shown on the right in the image. This cylinder is connected to a port in a cylinder of the engine under test, and the indicator's piston rises and falls as the pressure within the engine changes. A spring at the top of the cylinder provides a return force when the pressure in the engine decreases. A stylus is connected via a linkage to the moving piston so that it also rises and falls with pressure changes and records the pressure on a revolving drum with a paper card wrapped around it. This drum is seen to the left of the image. A cord is wrapped around the base of the drum and led via the pulley on the left to be attached to the engine under test so that it causes the drum to turn one revolution each stroke of the engine. A spring on the inside of the drum returns the recording paper to its starting point as the cord is relaxed. The result is a pressure-volume diagram of the engine while in operation, and engineers can measure and adjust the engine's properties under real time varying load conditions.

De Juhasz claimed his design improved over others due to his addition of cooling fins to the piston cylinder, reduction of mass of the piston and stylus, the use of light weight materials such as Bakelite, and a built in lubricator. He was an Assistant Professor of Engineering at Pennsylvania State College and Chief Engineer of a company manufacturing engine indicators.

The indicator is constructed of steel and Bakelite. Diagrams showing the complete design of the patent that it is based upon can be found in the patent document online at the United States Patent and Trademark Office website, www.uspto.gov.

Date Made: ca 1938

Place Made: United States: Pennsylvania

Subject: ModelEngines


See more items in: Work and Industry: Mechanical and Civil Engineering, Engineering, Building, and Architecture

Exhibition: Power Machinery

Exhibition Location: National Museum of American History

Credit Line: Gift from Kalman J. Dejuhasz, State College, PA

Data Source: National Museum of American History

Id Number: MC.311621Catalog Number: 311621Accession Number: 151188Patent Number: 2040082

Object Name: Indicatorindicator, diesel engine

Guid: http://n2t.net/ark:/65665/ng49ca746a6-6931-704b-e053-15f76fa0b4fa

Record Id: nmah_846147

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