A lawnmower that paints subway tracks

White paint prevents the Frankfurt subway tracks from being damaged by the sun. With the invention of a locksmith, it no longer has to be applied by hand.

The whiteners: VGF employees Dieter Lach, Nicola Heimbücher and Kurt Landau (from left) have built a lightweight painting machine for rails.

Se locksmith Kurt Landau has been working for the Frankfurt Transport Company (VGF) for more than thirty years. When he didn’t have much to do during the Christmas season, he thought about a problem that had been preoccupying the subway and tram operating company for a long time: hot sun rays can heat the tracks in some places so that they expand too much.

Actually, there is already a solution for this: employees simply paint the tracks white at the endangered points. But Kurt Landau was bothered by the fact that his colleagues always had to bend down when painting. So he decided to build a machine that would make painting easier.

White color protects against overheating

In strong sunlight, the rails expand and the tracks begin to undulate, says Tim Schwartz, engineer in the technical service of VGF. Some track sections can reach temperatures of up to 60 degrees. There are tensions on the tracks, which experts refer to as “track displacement”. In the worst case, these can lead to derailments. To avoid overheating, the white paint is applied, says Schwartz. The paint causes the rails to reflect sunlight. Tests have shown that the white paint cools the tracks four to five degrees, says Schwartz.

Protective layer: white acrylic paint is poured into the sprayer.
Protective layer: white acrylic paint is poured into the sprayer.: Image: Aders, Hannah

So far, he has only developed a lid lifter and repaired a few areas at work, says the 54-year-old Landau. In the Christmas season last year, however, he started to draw up the sketches for the painting machine. Landau presented the drawings to his superiors, who approved his project. The development then took a few months, says Landau. But when he finally finished the drafts, he and his colleagues assembled the machine within just two weeks.

Climate-friendly, quiet and light machine

The Deutsche Bahn and the Austrian Federal Railways already machine their tracks with white paint in midsummer. The special feature of Landau’s machine, however, is its weight: It only weighs around twenty kilograms. This means that the device can be pushed over the rails by one person like a lawn mower. Landau says that the machine can simply be lifted off the tracks for two. Other painting machines also require a power cord while his is running on a battery. That makes the machine more climate-friendly and quieter.

Landau’s construction consists of a self-welded metal frame. A sprayer is built into it that sprays the white acrylic paint onto one side of the rail. The rail head, i.e. the upper side of the rail, remains free, as the trains would smear the white paint when they pass through. Around one liter of paint fits into the spraying machine, which means that around 50 to 60 meters of track section can be sprayed. Landau and his colleagues will find out how long the color will last over the course of the summer.

The machine is to be used in the entire network

The machine is currently being tested in the VGF depot east. A company spokeswoman emphasizes that the machine is still a prototype. The focus now is on improving the machine. Soon it will be used for track sections that are particularly exposed to the heat. The long-term goal is to use the machine in the entire network.

Landau does not regard his machine as an invention. He said he didn’t invent the spray gun or paint, but simply combined both things. He still sees many “teething troubles” that need to be corrected. He wanted to replace the painting machine with an aluminum frame, which previously consisted of steel tubes. This makes the machine lighter, he says. Another hope is that the machine will drive by itself. But he is still a long way from autonomous painting.