Ease

Goal / Challenge

The ease bicycle electrification kit is the latest development of TUM CREATE, which is a research collaboration between TUM (Technische Universität München) and NTU (Nanyang Technological University, Singapore) fully funded by the National Research Foundation (NRF) in Singapore. While in general TUM CREATE researchers are targeting future mobility concepts, in this side project the electric drive unit called ease was developed to tap into existing good quality bicycles and offer an easy way of turning them into electric bicycles.

Approach / Methodology

There is a huge trend in the market obvious for increasing sales of e-bikes in the last years. Big developments in the battery technology and powertrain possibilities, but also changes of the public perception about these vehicles, enabled a big gain. Yet, the big majority of sold bikes are still conventional and also due to the rather long lifespan of bicycles there is a big amount of common bikes existing. When people are asked, why they don’t buy a pedelec, an often given answer is that they still own a yet sufficient bike.

Here the idea of conversion kits starts. This idea is not the newest, there are already several models on the market or at least introduced. But they are not very successful due to different reasons. A lot are difficult to get mounted on the frame and have to be ordered very specific to a special bicycle without any attachments. Furthermore most countries require a pedalling detection by law and this is solved most of the time by an additional sensor that has to be installed and wired up separately.

Results / Solutions / Outcomes or Expected Outcomes

Ease is equipped with a friction wheel. Thus, it can accommodate most frames while not getting in contact with the dirty chain drivetrain. The friction wheel itself should be located at the rearmost part of the rear wheel, just under the end of a possible mud guard. The only mounting point on the frame then is intended to be at the middle of the seat stay tube. This gives a geometry that will cause the propelled friction wheel to “bite” into the tire and pressing itself against it without the need of a heavy weight (“Wedging effect”). So a slipping can be prevented without a rough surface that would wear itself and the tire off over the time.

A sensor at the front of ease measures the distance to the leg of the cyclist in order to detect pedalling movements triggering the assisting motor. As the permanent motor power is limited to 250 W and equipped with a speed sensor cut-off at 25 km/h, it ensures the compliance with EN 15194 regulations for pedelecs in the EU and many other countries. Therefore, ease can be legally driven on public roads without helmet, driving license or number plate.

Mounting the drive unit is very easy and done within seconds. No tools are required. The cyclist just has to hold ease with one hand while hooking a wire loop around the seat stay to the unit with the other hand. Turning a knob on the front tightens the rubber sleeved wire and therefore fixes the unit to the frame. Removing ease from the bike is just as simple and doesn’t leave any marks on the bike. Integrated sensors sense the side on which ease is mounted, so in case one seat stay is not available due to Bowden cables etc. it can just be mounted on the other side.

Unique Features / Benefits / Specifications

The whole unit is foldable in the middle to make it more compact for transportation. In the front part there is the mounting, the distance sensor and one battery pack. In the rear there is another battery, the motor with attached friction roller and all the required electronics. The whole case is made out of aluminium to ensure required stiffness but also to allow the batteries to cool down over the surface. On the front it is covered with a plastic insert, which is sealed to have the inside waterproofed.

On the rear part in the middle of the plastic surface there is another aluminium part in an oblong shape with several functions. Firstly, it is a design part with the ease logo written on it that can be read no matter on which side the unit is mounted. Also it includes two buttons (on/off and power level) with status LEDs and a battery level indicator. Finally, it is also a heat sink as the power electronics are mounted behind. So it is thermally decoupled from the case and can avoid that the electronics heat up housing and therefore the battery, which would accelerate its aging.

The motor is actively air cooled with the intake through the notch for the mounting when folded and the outlet on the rear. To increase safety, there is a LED rear light next to the air outlet, which functions also as a break light with higher brightness, as deceleration can be measured with the speed sensor. The friction roller shape is specially designed to avoid the roller jumping off the wheel and also to minimise wear and tear of the tire. Jumping is also prevented with a rotary damper in the mounting so that it is safe to cycle down a curb or similar.

The whole unit weights around 3.5 kg and therefore is very easy to handle when folded. The weight comes mainly from the 220 Wh battery, which is sufficient for a range of up to 50 km. With that, the targeted customer group of commuters and leisure cyclists should easily cover their journeys.