How does riding an Impulse bike compare with riding a bicycle with no electric assistance at all? And how does it compare with the Panasonic system?
Kalkhoff's Impulse system combines a pedal assist motor, battery pack and control panel mounted on the handlebars. Pressing the On button activates the electrics, presenting you with an indication of battery charge (up to three LEDs) and three assistance modes - Eco, Sport and Power. There's also a gear shifter by the right handlebar grip as well as brake handles and a bell.
Once switched on putting pressure on the pedal activates the motor as you move away and very soon you're cruising along, with very little effort, at a speed of up to about 15.5mph. Shifting between the gears and power modes determines how much effort you have to make and how fast you go. With the 36V 15Ah battery supplied with the 50cycles Impulse models in 2012, you can carry on like this for up to 180 kilometres (about 111 miles) in ideal conditions.
Compared to the Panasonic system there is a feeling of greater and more consistent assistance. Moving from a standstill is smoother, there is less of a need to find the right gear. Impulse almost seems to anticipate hills and get into its stride, making them easier to cycle up than flat sections. On test rides we've found that you can generally climb hills in a higher gear than is possible with the 26V Panasonic system.
The 36V Impulse motor operates up to 4300 rpm (compared to the Panasonic's 3000 rpm) with a 50:1 reduction to match the rider's cadence. The graph below boils it all down and shows how Impulse outstrips the Panasonic system in all power modes.
Comparison of the power available to the rider in each of three selectable assistance modes
Power assistance is now independent of your pedalling cadence
The Impulse drive system guarantees full power from the motor even when you're cycling at low speeds and using more energy, for example when cycling uphill. With the Panasonic system it was important to maintain the correct cadence (rate of pedalling) to get maximum assistance - Impulse is much more forgiving. The result is mile after mile of effortless, fun cycling, whatever the terrain.
This is very important for rideability. Impulse assists you over the entire speed range, however fast or slow you pedal. The 26V Panasonic drive dictates the best cadence for maximum assistance (71 rpm), whether that was your preferred cadence or not. In contrast, Impulse offers a range of peak cadences, from 87 down to 65. Each cyclist has a narrow range of preferred cadences, so Impulse does not demand that the rider sticks to 71rpm because it uses three sensors to detect what the rider is doing rather than the Panasonic's single torque sensor.
Comparison of the pedal cadence demands of the Panasonic and Impulse systems
A very nice side-effect of how the Impulse system is programmed is that you can fly along almost effortlessly at the top speed in 6th and 7th gear, but if you feel the need to give your legs a work out and cycle faster than the assisted limit, 8th gear is there to shift up to whenever you like. It's surprising how much distance you can cover in this way, without getting either bored or tired.
Other riding characteristics
The centre motor is not just the tried and tested pedelec drive system, it is also the most comfortable, the best. For the cyclist this means a bike that is easier to handle, especially on tight bends and in sudden changes in direction. The low centre of gravity and bike-like handling feels right.
The diagram below shows how centre motors offer peak efficiency whatever the gear or speed. This makes for more efficient hill climbing and load carrying. Hub motors, though nominally the same power rating of 250W, are prone to struggling on very steep hills which can both drain and even damage the battery. It can even mean the rider is unable to continue climbing when the motor stalls as it falls below the minimum speed to operate. Centre motors put the power through the gears and are so better able to help the rider climb even steep gradients. Next page: Extra Impulse features
Kalkhoff Impulse efficiency (blue lines) compared to hub motor efficiency (thicker red/green line). Hub motors are not able to put power through the gears so are less able to offer comparable efficiency at as wide a range of speeds.
Next page: Extra Impulse features