Duesenberg Model A

The Duesenberg Model A was the first automobile in series production to have hydraulic brakes and the first automobile in series production in the United States with a straight-eight engine. Officially known as the Duesenberg Straight Eight, the Model A was first shown in late 1920 in New York City. Production was delayed by substantial changes to the design of the car, including a change in the engine valvetrain from horizontal overhead valves to an overhead camshaft; also during this time, the company had moved its headquarters and factory from New Jersey to Indiana. The Model A was manufactured in Indianapolis, Indiana, from 1921 to 1925 by the Duesenberg Automobiles and Motors Company and from 1925 to 1926 at the same factory by the restructured Duesenberg Motor Company. The successors to the company began referring to the car as the Model A when the Model J was introduced.

Background

Fred and August Duesenberg built aircraft and marine engines during World War I and used this expertise to design and build racing engines and to design a car. The Duesenberg Automobiles and Motors Company was incorporated in Delaware and founded to manufacture and market the production car while Duesenberg Brothers, a separate organization, built racing cars and engines.

Introduction and delay

Design and engineering

Drivetrain

The Straight Eight was the first car in series production in the United States with a straight-eight engine. The engine had a cast iron block, a detachable cast iron cylinder head, and an aluminum lower crankcase and oil pan. The crankshaft ran in three main bearings. While the prototype Straight Eight shown at the model's introduction had horizontal valves of the type used in earlier Duesenberg-designed marine and racing engines, the model that entered production had a shaft-driven single overhead camshaft which used rockers to operate two valves per cylinder in a hemispheric combustion chamber.

The engine used a single updraft carburetor; early versions used a Stromberg unit, which was replaced by a Schebler unit. The carburetor was on the right side of the engine, the mixture went into a passage through the engine block to the intake manifold on the left side of the engine. Ignition was by Delco coil and breaker points, with the distributor at the end of the generator/starter unit.

With a 2.875 in bore and a 5 in stroke, the engine had a displacement of 260 cuin. The standard compression ratio of five to one yielded 88 hp at 3600 rpm and 170 lbft of torque at 1500 rpm. This gave the Model A a top speed of 71 mph.

A single dry-plate clutch and an unsynchronized three-speed gearbox were bolted to the engine. The gearbox was operated directly with a central shift lever. The drive shaft was enclosed in a torque tube and drove the live rear axle through a spiral bevel drive.

Chassis

The chassis was based on a pressed steel ladder frame with channel-section side members and fabricated and tubular cross members. Suspension was by semi-elliptic leaf springs and Watson Stabilator dampers front and rear, with a tubular beam axle at the front and a live axle and radius rods at the rear. The standard wheelbase was 134 in, with a wheelbase of 141 in available for seven-passenger bodies. The front and rear tracks were both 56 in wide. Center-locking wire wheels with 5" x 33" tires were used front and rear.

The Duesenberg Straight Eight was the first production automobile to use Lockheed Corporation Hydraulic brakes on all four wheels. The brakes on the front wheels were 16 in in diameter and were finned to dissipate heat. The fluid used in the system was a mixture of glycerine and water.

manufacturer	Duesenberg
production	1921–1926
successor	Duesenberg Model X
configuration	straight-eight engine
displacement	260 cuin
bore	2.875 in
stroke	5.0 in
block	cast iron, 3 bearings
head	cast iron, detachable
valvetrain	Shaft-driven SOHC, 2 valves/cyl.
compression	5:1
fuelsystem	Single updraft Schebler 1 1/2 in carburetor
management	Delco coil and points, distributor mounted at end of starter/generator unit
fueltype	Gasoline
oilsystem	Wet sump, full pressure lubrication
coolingsystem	water cooled
power	88 bhp @ 3600 rpm
torque	170 lbft at 1500 rpm

Background

Introduction and delay

Design and engineering

Drivetrain

Chassis

Reception

Legacy

Notes

References