Bicycles with auxiliary Motor

After Daimler built a scaled-down Otto engine into a wooden frame and fitted it with a front and rear wheel, the "motorcycle" was a reality.

Soon after this, many blacksmiths, bicycle repairers and others began to build engines into bicycle frames. Hildebrand & Wolfmüller brought the first motorcycle in 1894 to market. By 1897 several hundred had been built.

Motorcycle reliability improved in the following decades. The first major serial manufacturer of motorcycles was the American company Indian. It was founded in 1901 and quickly developed into the largest motorcycle manufacturer in the world. Production rose to 60000 machines by 1914.

Stamps in a Canadian stamp booklet, showing CCM (1908) and Indian (1914)

Front side of Canadian stamp booklet above - showing Indian (1914)

What is less known is the development of auxiliary engines that could be attached to the handlebars of a bicycle, driving the front wheel. An example of this is the Austro-Motorette of the cooperating companies Werke Arsenal of Vienna, which built the actual motor, and Steierische Fahrzeugwerke G.W.A. of Graz-Puntigam which produced the rest of the parts.

Advertisement for Austro-Motorette

Busta Lettera Postale (BLP) - card sold at discounted rates by advertising
The additional earnings from advertising benefited WW1 invalids.

It was a simple air-cooled two-stroke engine that produced 1 hp at 3000 rpm. It had a special ignition system, a magneto ignition where the contact points sat in the cylinder instead of a spark plug. The closing of the contact points was controlled by a screw in the piston. It was built into the front wheel. This wheel, along with a curved front fork that also included a fender and the fuel tank, formed a complete drive unit that could be mounted to any bicycle.

Austro-Motorette's drive unit

But Austro-Motorette was not the only one to produce this kind of separate auxiliary motors. To my great surprise, a card was recently offered with an advertisement for an Auto-Phoenix "Rijwiel-Inzet-Motor" on it.

Front of the card offered

Reverse side of the card offered

After searching the worldwide library that is the Internet, it turned out to be a DKW top-mounted motor. In retrospect, the answer was much simpler and closer to home: In my exhibition-collection for years has been a card letter from Germany with an advertising image of the motorcycle I searched for (compare RE24683).

The motorcycle history of DKW, in 1929 the largest motorcycle manufacturer in the world, begins in 1919 with a 118 ccm clip-on bicycle motor. This bicycle motor was mounted above the rear wheel of any normal bicycle and drives the rear wheel with a V-belt.

The pulley in the rear wheel is smaller than those of competing contemporaries because the engine pulley is not mounted on the crankshaft but is driven with a 1:3 gear ratio. A floatless carburetor is used. DKW has used several brands of carburetors over the years, such as Tuto, Variat and Adria. The contact points are located outside the flywheel, under a cover at the rear of the engine. The contact points are controlled via a pushrod and a camshaft with three cams. Bore and stroke are 60x50 mm² and the engine weighs 14 kilograms. Because of the shape of the tank, with logo in relief, the engine was nicknamed “Bettflasche,” which translated means “hot water bottle.” Another nickname, due to the position of the engine, is “Arschwärmer” (literally “butt warmer”), neatly translated as “steak warmer” in the Netherlands.

The bicycle on which this DKW auxiliary is mounted is a beautiful Gazelle, a Dutch quality bicycle.
The original leather “Gazelle” saddle is still on it, as is most of the celluloid covering of the handlebars.

DKW claimed a top speed of 40 km/h and the ability to climb a 10% slope without pedal assistance. This was advertised with the phrase: „DKW, das kleine Wunder, läuft bergauf wie andre runter!“, which can be translated as "DKW, the little wonder, runs uphill like others down!". The DKW bicycle motor was an immediate success: on June 17th 1922 the 20000th rolled off the assembly line at Zschopauer Motorenwerke and on February 15th 1924 the 50000th.

Now the question to the real technicians in our association (Motor Filatelisten Nederland - MFN): is the Vélosolex a representative of the above "bicycle set-up motor" or is this a "normal" bicycle with auxiliary motor?

Author: Nico Helling   -   contact: This email address is being protected from spambots. You need JavaScript enabled to view it.

This article was originally published in the newsletter no. 152 of The Dutch Motorcycle Philatelists Club MFN (Motor Filatelisten Nederland) in June 2025: DKW 118cc tweetakt eencilinder gemonteerd op een fiets  (the original title "DKW 118cc two-stroke single-cylinder mounted on a bicycle" has been slightly adapted for this website.)

The subject areas of bicycle stamp collectors and motorbike stamp collectors overlap when it comes to early bicycles with auxiliary drive. This has resulted in a friendly relationship with the members of the MFL. I would like to take this opportunity to thank Nico Helling, who gave me permission to publish his article here.

 References/External links:

    Bicycle Auxiliary-Motor Club Netherlands RHC: Rijwiel Hulpmotor Club Nederland - RHC

There are two more DKW card letters listed in the online catalog of this website:

RE24681

RE24956

In the online catalog, each entry is arbitrarily assigned a category. Bicycles with supported drive can often be found in category “1.1.11”:

The search function returns the following entries via this category number. You will find that a whole range of e-bikes have now also found their way into philately.