Air Knife Tread Cleaner

Driving around in poor weather conditions can be hazardous. Perhaps the most challenging conditions are caused by the various forms of water that fall from the sky and contaminate the surface of the road. Water between a car tire and the road surface reduces friction in many ways from dissipating electrostatic interactions to forming a complete interface layer that lubricates your tangental path into a field.

Tire manufacturers have developed strategies to cope with this, largely by cutting/molding grooves into the surface. The raised blocks create a smaller contact patch, increasing pressure to channel flow between blocks. That's fine until water flow is insufficient, the car too fast, too much water or the water is a solid.

Snow is particularly tricky, watching city dwellers struggle in snow* will highlight the problem: snow compacts into the tire channels, lodges there and renders the tire smooth. The typical countermeasure to this is to make the channels bigger and the rubber compound softer. Softening the rubber is partly a countermeasure against the stiffening effect of low temperature, but also encourages flex during loading and unloading as the tire rotates. This movement helps shed compacted snow in the channels. On a larger scale, lowering tire pressure changes the whole profile of the tire carcass for a similar effect. Sadly, winter tires are dreadful in the wrong environment, cars move and weather changes rapidly. So an alternative solution might be helpful.

Most people have had the opportunity to use one of the Dyson air blade (TM) hand dryers. These use a wide, thin stream of ~400mph air to remove the layer of water on the skin and distribute it to the general environment. Like all products of the Dyson inventive process**, they work OK, certainly 80%+ of the water is quickly and effectively removed. Granted, the drying is less effective than paper towels, dangerously loud and a microbiology nightmare, but these drawbacks don't affect our application.

So, inside the wheel-well of the chosen vehicle, fitted to to the suspension upright to maintain a constant distance is an air-knife nozzle. The best position is not obvious, but the 4-5 o'clock zone is a good start. Here, the nozzle is positioned at an acute angle to the surface, blowing high- speed air will dislodge water and act to encourage the tangental separation naturally occurring because of the tire rotation. The nozzle position means water is separated on the rear side of the tire and won't trouble that tire again. Cooperation between car manufacturers and tire makers is routine, here, the tire pattern and nozzle configuration could be optimized to dislodge even the most recalcitrant crystalline water.

The source of air for each wheel will need to be fairly robust. A Dyson hand dryer is 1.6kW, and this will only be on in tricky conditions, this is easily doable with a 12V centrifugal blower. However, we already have powerful air pumps in cars. Exhaust bleed could be used, A tap from the compressor side of now-universal turbochargers or, a separate turbo re-purposed as a dedicated high-capacity blower.

An extension of the idea would be to focus a high- pressure air jet right in front of the tire. Removing a substantial percentage of the water would dramatically increase the apparent capacity of the tire itself. Combining both would be a big help to trucks, and a possible advantage in racing, it's not obviously prohibited in the F1 rules for example.

*is an excellent hobby, find a bar with a big window opposite a huge car park as a snowstorm rolls in on a Friday night and enjoy.

**Browse through an industrial catalog, spot cyclonic dust separator, add marketing, sell. Browse again, spot compressed air powered mine ventilator, add marketing, sell. Browse again, spot air-knife, add marketing, sell.