Robust joint and plain bearings in the<br />heavy-duty e-cargo bike

Lightweight and durable even when fully loaded

In order to improve air quality in cities and avoid gridlock, more and more logistics companies are using electric cargo bikes to deliver parcels to people's front doors. However, in order to be a useful addition to lorries in the long term, electric cargo bikes must be one thing above all: robust and low-maintenance. The designers at b&p engineering therefore rely on plastic bearings from igus® in their heavy-duty model.

Profile

What was needed: Alternative for metallic bearing in the steering and trailer coupling
Requirements: Durability, corrosion-free, resistance to UV radiation, dirt and temperature fluctuations, self-adjusting, lubrication and maintenance-free, low weight
Area of application: Bicycle industry

With the boom in online trade, more and more vehicles are travelling through cities, causing congested roads and poor air quality. CEP service providers are therefore looking for cleaner transport solutions such as emission-free lorries or electric cargo bikes. One of the manufacturers of such e-cargobikes is b&p engineering mobility GmbH from Scheßlitz near Bamberg. Its innovative, four-wheeled heavy-duty model is a true Hercules among cargo bikes. It enables logistics specialists to transport parcels with a total weight of up to 250 kilograms to people's front doors. Hermes is currently trialling the bikes in Stuttgart and GLS is already using them in Nuremberg.

Problem

E-cargobikes are a hotly contested growth market that more and more start-ups are entering. "We can only survive in this highly competitive market if we are constantly developing new and innovative solutions", says Wolfgang Hindel, Sales Director e-mobility at b&p. A high payload alone is not enough. To be able to deliver as efficiently as possible, logistics companies want e-cargobikes that are manoeuvrable and at the same time highly reliable and low-maintenance. "We have therefore designed our vehicle so that it is easy to manoeuvre and steer and can withstand around 6,000 kilometres between service intervals. That is an above-average figure in our industry." To achieve this, the designers have thought in new directions. Many components do not originate from classic bicycle construction, but are borrowed from the e-scooter and motorbike sector - including brakes, wheels and chains.
It was also necessary to rethink the handlebar bearings and find an alternative to classic roller or plain bearings made of metal. These were out of the question for several reasons: firstly, there was a constant risk of premature failure due to edge loads. Secondly, the installation would have been comparatively complicated: "We would have had to use additional encapsulations and seals to protectthe metal bearings from corrosion in wind and weather", says Vincent Okroy, the vehicle's designer. And thirdly, modifications and readjustments would have been necessary to compensate for misalignments - an expense that was to be avoided. At the same time, b&p always endeavoured to save as much weight as possible on all components.

Solution

With components from igus®, several birds could be killed with one stone. The engineers chose a hard-anodised, coated igus® aluminium hollow shaft as the steering rod, which is actually used for linear guides in mechanical engineering. It is mounted on an igubal® spherical plain bearing from the EGLM-30-LC series. This allows the steering rod to move linearly and simultaneously up and down, allowing the front cross member to swivel around the frame. This allows, for example, a wheel to drive on the kerb without the frame twisting. Precise alignment of the bearing housing is not necessary, as the bearing automatically compensates for misalignment and edge loads. It works reliably at temperatures from -30 °C to +80 °C and is resistant to moisture, UV light and salt. It does not need capsules or seals to protect it from corrosion.
The spherical ball made of iglidur® W300 material runs completely lubrication-free with the lowest friction values. The bearing housing, made of igumid® G-polymer, is extremely robust: It can withstand a static axial load of short-term 4,000 N and a radial load of 17,000 N trade show. "A good plastic bearing can withstand what a steel bearing can," says Okroy. This is not only proven by tests in the igus® test laboratory. "The bearings are stable enough to cope with all everyday driving situations, even with a full payload of 250 kilograms. This has also been proven by our tests, in which the vehicle travelled 80,000 km with a full load." Last but not least, the igubal® bearing scores with its low weight of just 26 grams. Comparable metal spherical plain bearings, including encapsulation and sealing, weigh around 120 grams.

b&p also utilises the weight advantage on the swivel head of the attachable trailer coupling: iglidur® X bushings with particularly high compressive strength are used here.

The polymer bearings from igus® are inconspicuous at first glance. "But they have helped us save weight, reduce assembly time and increase the robustness of the vehicle while reducing maintenance.