Benz Patent-Motorwagen

This model is driven by hand or by a rubber band. Ligroin and similar light petroleum spirits are highly flammable — nothing here is vaporised and nothing is ignited.

Power transmission, a brake that disengages the drive in one movement, cooling by condensation, and a fuel level indicator. The engine itself is not the new part.

Cut a baseboard and fit four wheels, the front pair rigid. Push the vehicle and try to drive it round a curve.

Mount the two front wheels on a single turntable board. In a curve the wheels scrub — the inner one ought to follow a tighter path than the outer.

Convert to a single, centrally steered front wheel. The scrubbing disappears. This is exactly why the Patent-Motorwagen has three wheels and not four.

Mount a crankshaft across the frame. It stands in for the horizontal single cylinder — what interests us is only what happens behind it.

Turn the drive through 90° with two bevel gears. This lets the engine lie across the frame while the wheels are driven along it.

Take a chain from the countershaft to each rear wheel. Chains allow distance between engine and axle — precisely what the claim means by keeping the vehicle steerable.

Both rear wheels turn at the same speed although they travel different distances. It judders. A differential is still missing, and that is the next step in the history.

Fit a lever that simultaneously presses a block against a wheel and pushes the drive belt off its pulley. One movement, two effects — as the patent states.

Disconnect the disengagement and brake alone. The drive works against the brake. That is exactly what Benz set out to prevent with a single movement.

Stand an open jar of hot water out and hold a cold sheet of metal above it. The vapour condenses and drips back — that is all the Motorwagen's cooling is.

Weigh the water before and after ten minutes of boiling. The loss is substantial — a vehicle like this must top up water on the road, not just fuel.

Fit a vertical glass tube to a vessel. The level in the tube shows the level in the tank — simple, and expressly claimed in the patent.

The patent. DE 37435, "Fahrzeug mit Gasmotorenbetrieb", filed 29 January 1886, published 2 November 1886. Two things are almost always reported wrongly. First, 29 January is the filing date, not the day of grant. Second, the applicant is "Benz & Co. in Mannheim" — the company. Carl Benz built the vehicle, but the document names a firm, which was the norm for company patents of the period.

Why three wheels. Not for economy, but because the steering problem was unsolved. In a curve the two front wheels describe circles of different radii and must therefore be turned through different angles. A common turntable cannot do that — step 4 shows the scrubbing immediately. The solution, Ackermann steering, was known from Lankensperger and Ackermann, but Benz only adopted it in 1893 with the Victoria. Until then a single steered wheel was simply the cleaner route.

The missing differential. Step 9 shows the second unsolved problem: two rear wheels driven rigidly at the same speed judder in a curve. Benz later patented the differential gear himself. The Motorwagen is therefore not a finished automobile but the first machine in which engine, drive, brake and steering were designed together for the purpose — and that is exactly what the claims are aimed at.

🔴 Bertha Benz belongs inside this story, not as an anecdote. In August 1888 she drove, without her husband's knowledge and with their two sons, from Mannheim to Pforzheim, about 106 km — the first long-distance journey by an automobile. She bought ligroin at a pharmacy in Wiesloch, because filling stations did not exist; she had a cobbler line the brake blocks on the way, thereby inventing the brake lining; she cleared a blocked fuel line with a hatpin and insulated a wire with her garter. Her feedback led to better brakes and an additional low gear for hills. She had also put her own money into the firm. Without that journey the vehicle would have remained a technically interesting one-off — she supplied the proof that it worked in everyday use.

What was missing was the infrastructure. No fuel network, no surfaced roads, and no tyre that could take it — the Motorwagen's solid rubber wheels are why Dunlop's pneumatic tyre of 1888 mattered so quickly. As so often in this programme the machine was finished before its surroundings were; unlike Nipkow or Poulsen, however, the surroundings here caught up within a few years.