The BMW 3/20 PS was the first BMW automobile designed entirely by BMW. It was manufactured from 1932 to 1934, replacing the 3/15 model that was initially an

Austin 7 The Austin 7 is an economy car that was produced from 1923 until 1939 in the United Kingdom by Austin. It was nicknamed the "Baby Austin" and was at that time one of the most popular cars produced for the British market and sold well abroad. ...

manufactured under licence from the Austin Motor Company. BMW AM4 03

The engine used in the 3/20 was based on the Austin Seven engine used in the 3/15, but its crankshaft ran in plain bearings instead of roller bearings and had an stroke, generating a displacement of . Norbye, p.30 The new engine design also had a water pump and an

overhead valve An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located b ...

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ...

. These design changes caused the engine to generate 20 hp, but did not change the taxable horsepower rating of 3 PS, thus giving the model designation 3/20. The 3/20 was larger than the 3/15, with an wheelbase and a body lower than the 3/15. Unixnerd: BMW's Early History The 3/20 used a backbone frame unrelated to the 3/15's Austin Seven "A" frame. Noakes, p.24 Robson, p.36 It inherited the 3/15 DA-4's

independent front suspension Independent suspension is any automobile suspension system that allows each wheel on the same axle to move vertically (i.e. reacting to a bump on the road) independently of the others. This is contrasted with a beam axle or deDion axle system in ...

and added a

swing axle A swing axle is a simple type of independent (rear wheel) suspension designed and patented by Edmund Rumpler in 1903. This was a revolutionary invention in automotive suspension, allowing driven (powered) wheels to follow uneven road surfaces ...

independent rear suspension, using a transverse leaf spring similar to that used at the front. The standard bodies for the car were built by

Daimler-Benz The Mercedes-Benz Group AG (previously named Daimler-Benz, DaimlerChrysler and Daimler) is a German multinational automotive corporation headquartered in Stuttgart, Baden-Württemberg, Germany. It is one of the world's leading car manufactur ...

Sindelfingen Sindelfingen (Swabian: ''Sendlfenga'') is a city in Baden-Württemberg in south Germany. It lies near Stuttgart at the headwaters of the Schwippe (a tributary of the river Würm), and is home to a Mercedes-Benz assembly plant. History * 1155 � ...

. Journalist and engineer

Josef Ganz Josef Ganz (1 July 1898 – 26 July 1967) was a Jewish-German car designer born in Budapest, Austro-Hungarian Empire (now Hungary). Early years Josef Ganz was born on 1 July 1898 into a Jewish family living in Budapest, then the second-largest ...

, who had criticized the 3/15 DA-4's suspension system in the magazine ''

Motor-Kritik ''Motor-Kritik'' was the title of a progressive automotive magazine, published by the H.Bechhold Verlagsbuchhandlung in Germany from 1929 to 1945. It originated from the earlier ''Klein-Motor-Sport'' magazine. History ''Klein-Motor-Sport'' was th ...

'',Article ‘''Die Schwingachse des Kleinen'',’ ''Motor-Kritik'' magazine, issue 3, early February 1931 was contracted in July 1931 as a consultant in the design of the 3/20 AM-1. Four versions of the 3/20 were built: AM 1, AM 2, AM 3 and AM 4, where AM denoted ''Automobil München''.

References

;Citations ;Sources * * * * * 3 20 Rear-wheel-drive vehicles Cars introduced in 1932 1930s cars Automobiles with backbone chassis {{Vintage-auto-stub