Trains are going full steam ahead to blast leaves off railways with microwaves

As we welcome autumn with pumpkin-flavored beverages and stylish attire, train operators see the season as a cause of disruption. This is all thanks to leaves fluttering down onto the railways and turning into a wet mulch as trains speed over them. The slippery coating requires train drivers to brake earlier when approaching stations and signals, and then accelerate cautiously to avoid wheel-spin. 

Because the situation is so common, annual timetable adjustments are made, and the London-based Imagination Factory hopes to alleviate the issue with bursts of microwave energy to dry out sections of the tracks. In 2014 the company was awarded funding by the Rail Safety and Standards Board (RSSB) to take forward its solution as part of the “Predictable and Optimized Braking Challenge.”

The company’s solution, which has completed an early proof of concept feasibility study, would see microwave energy directed at railway tracks during braking. According to engineering lead and co-founder of Imagination Factory, Julian Swan, the idea is to dry the contact patch between the rail and wheel interface, which is 12 mm wide.

“ We are not intending to dry the full track width,” Swan told The Engineer. “Our design vision is to have a modular approach to enable us to treat the tracks individually and progressively down the length of the train.”

When it comes to the microwave element, Swan said the initial Proof of Concept rig operated at 6 kW using an 896 MHz source, but that in the next phase of development, the company will look into 2.3 GHz as this can improve energy density and component compactness. It’s also proposing separating the power electronics from the microwave generation by the use of coax cabling.

“This will enable us to locate some of the larger more sensitive pieces of equipment on the sprung chassis of the carriage and the more robust solid state elements of the microwave antenna can be located near the wheel,” said Swan. “This flexible modular build principle should enable the final design to be retrofitted as well as incorporated in new build.”

As of now, scale tests have been completed at 1 MPH, but the company’s mathematical model suggests a linear relationship enabling full effect at up to 50 MPH. Swan and  team plan to demonstrate this during the next phase of funded development through the RSSB. Additionally, the energy used for the system during braking could also be created by regenerative braking. Since regen brakes aren’t able to return the energy to the grid due to the quality of what’s created, the new system could easily utilize that energy.

According to the company, if all goes according to plan, the system could be introduced within two years. Currently it’s in discussion with rail operators and train building companies including Bombardier and Hitachi, which could fit the system on new carriages.