Silent running

A revolutionary gearhead system from Maxon Motor is offering exceptionally low noise levels while minimising the normal trade off with torque. The 32mm, 6Nm, Koaxdrive KD32 combines a worm formed motor pinion with multiple planetary gearing stages. The idea was born out of the Black Forest in Germany by a furniture maker. He wanted to use motors to allow adjustment of office desks and seats, but needed a near silent motor to avoid the constant whirring. "He essentially brought the idea to Maxon to patent," says Ian Bell, a senior sales engineer at Maxon Motor UK. "But we see the market as being much bigger with great potential in the medical sector." Examples of potential applications range from surgical instruments, bedside equipment in hospitals to life support systems and blood pumps. Medical applications usually require low noise generation to minimise patient distress. But the motor is also being used in cinematic camera mounts, where audio is involved, and in the 1st class section of Virgin Atlantic aircraft to allow the seats to fold out into beds. The two types of gear mechanisms come together in the first stage. This is where the highest peripheral motor speeds occur; the primary cause of noise. A helical worm pinion drives three offset planetary gear wheels made from plastic. This drastically reduces normal noise. "In the motor housing you have got three offset shafts in the circumference," says Bell. "On these shafts are the gears. These gears run in an annulus ring around the outside like an ordinary planetary gearbox. But on top of this cylinder is the sun gear for the next stage of the gearbox, which, after the first stage is an ordinary planetary gearbox. "Three of these angled wheels are driven by one worm gear, which is enclosed in the first stage. We don't just put a pinion on the motor, we actually have a motor shaft that goes into the worm gear. This is attached by a collar arrangement to clamp it on." As the worm turns, the three wheel gears rotate and interface with the annulus gear, which drives the whole cylinder around. Additionally, it uses a sliding mechanism to take axial load off the motor shaft, which also reduces contact sound and allows the gearhead to operate at low volume, even at 8000rpm. The efficiency is quite high for such a compact arrangement, about 60%, with torque output actually the same as its standard 32mm gearbox. Formula One puts motors on front wing Formula One cars will use Maxon motors this season as new rules allow the pitch of the front wing to be adjusted. Six-degrees of movement to adjust flaps on the car front wing, up to twice per lap, allow changes to aerodynamic behavior; increasing downforce into a tight bend, or reducing drag for higher straight line speed. Maxon's Neodymium magnet-equipped motors are capable of performing the precise movements and are also small and light enough to avoid compromising weight. The miniature motor delivers immense low-speed torque for its weight and size. Angelo Guttoriello, chief executive of Maxon Motor UK, said: "It's always gratifying when the world's top engineers depend on Maxon for their most challenging and important applications. Formula One is no exception. The teams invest tens of millions of pounds in getting their cars absolutely right, and they all trust our drives to play their part, perfectly, every time."