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Cyclotracteur on Alcyon bicycle - 1918

My Cyclotracteur auxiliary engine on an Alcyon bicycle from 1918 clearly illustrates how the name motorcycle originated. It is clearly visible that this concerns a bicycle, that has been equipped with a loose engine. The driving is done with a roll, which is pressed onto the front tyre. Probably the Cyclotracteur was one of the first engines that used this principle, that has (much) later successfully been used for the Dutch Berini "Egg" and off course on the Solex. Apart from these many other manufacturers have used roll driving over the course of time, sometimes also for an engine that was mounted underneath the pedal axis. A well-known example of the latter one is the Lohmann diesel engine.
In contradiction to most other roll driving engines the Cyclotracteur does not use a 2-stroke engine but a 4-stroke. The displacement is 108cc. The exhaust valve is operated by a cam, but the inlet valve is a so-called automatic valve, also known as "sniffle valve". The ignition is done by a DĂȘesse magnet.
The force pressing the roll on the front tyre can be controlled by moving the complete engine a bit more or a bit less downwards. This is done by an ingenious mechanism with a turning handle above the handlebars. When the engine is moved down onto the tyre you must pull in the valve lifter handle (which opens the exhaust valve), make some speed by pedaling and then loosen the valve lifter. When the engine starts you will chug on at a speed around 35 km/hr.
Here some pictures:

Cyclotracteur op Alcyon fiets - 1918

Cyclotracteur op Alcyon fiets - 1918

Cyclotracteur aandrijfrol - 1918
The cast iron driving roll

Cyclotracteur aandrukmechanisme      Cyclotracteur aandrukmechanisme
The mechanism to push the engine down onto the front tyre by turning the handle

The Cyclotracteur was sold as a complete set, together with the whole linkage system to mount it on a bicycle and a fuel tank to be placed above the handlebars. The whole is made in such a way that it can be installed without adaptations to the bicycle, and can thus also be demounted without problems
A disadvantage of this construction is that it makes the bike top-heavy. Even though the engine weighs only 13 kilograms, you still feel it very clear. Because a large part of the weight is on the left side, the bike has also the tendency to fall to the left. I am curious to experience how that feels.
My intention is to once get it registered. As a moped (for Dutch law still a "bicycle with auxiliary engine") must have an engine with less than 50cc displacement it will probably be registered as motorcycle. And this while looking at its maximum speed only, it could probably even have been a "snorfiets" (Dutch type of light and slow moped which may be driven without safety helmet)....

Cyclotracteurs are often missing one or more of the parts that are necessary to install the engine on a bicycle. To facilitate copying these parts I have made a series of pictures of these parts with their dimensions written next to them.

That it is possible to come quite far with a Cyclotrateur, despite its moderate velocity, has been proven by these 3 Frenchmen, by riding in 2019 in the Netherlands both the Horsepowerrun (total ca. 87 km!) and the "Around Gees" run:

3 Cyclotracteurs aan de start van de Horsepowerrun
3 Frenchmen with their Cyclotracteurs ready for the start of the Horsepowerrun