De Dion-Bouton steam tractor

In 1893 De Dion-Bouton introduced steam tractors designed to tow horse-drawn carriages for passengers or freight, sometimes called steam drags. They followed the firm's steam tricycles, which had their boilers between the front wheels and two-cylinder engines and were built in small numbers. The tractor used an innovative axle that became known as the De Dion tube, in which the location and the drive of the axle are separated: a beam carried the weight of the vehicle while the driveshafts or chains were articulated alongside it. On 22 July 1894, in the Paris to Rouen race, a tractor averaged 18.7 km/h over the 126 km route but was disqualified because it needed both a driver and a stoker. The company went on making steam buses and trucks until 1904.