Robust joint and plain bearings in the
heavy-duty e-cargo bike

Problem

E-cargo bikes form an extremely competitive growth market that more and more start-ups are jumping into. "We can only survive in this strong competition if we continuously work out innovative solutions," says Wolfgang Hindel, Sales Director e-mobility at b&p. A high payload alone is not enough. To deliver as efficiently as possible, logistics operators want e-cargo bikes that are manoeuvrable yet highly reliable and low-maintenance. "We therefore designed our vehicle to be easy to manoeuvre and steer, and to withstand around 6,000 kilometres between service intervals. That is above average in our industry." To achieve this, the designers have thought along new lines. Many parts do not originate from classic bicycle construction, but are borrowed from the e-scooter sector and the motorcycle sector - including brakes, wheels and chains.
It was also necessary to rethink the steering rod bearing and find an alternative to classic rolling or plain bearings made of metal. These were out of the question for several reasons: first, due to edge loads there would be a constant risk of premature failure. Second, installation would be comparatively complicated: "We would have had to use additional encapsulation and sealing of the metal bearings to protect them from corrosion due to wind and weather," says Vincent Okroy, the vehicle's designer. And third, retrofits and readjustments would be necessary to compensate for misalignments - an expense that they wanted to avoid. At the same time, b&p was fundamentally committed to saving as much weight as possible in 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 bearing of the series EGLM-30-LC. In it, the steering rod can move linearly and move down and up at the same time, and the front cross member can thus pivot around the frame. For example, a bike can ride on the curb without the frame twisting. Exact alignment of the bearing housing is not necessary because the bearing automatically compensates for misalignments and edge loads. It operates reliably at temperatures from -30°C to +80°C and is resistant to moisture, UV light and salt. It doesn't need packaging and seals that protect it from corrosion.
The spherical ball made of iglidur W300 material operates completely lubrication-free at lowest coefficients of friction. The bearing housing, made of igumid G polymer, is extremely robust: it withstands a static axial load of 4,000N for a short time and a radial load of 17,000N. "A good plastic bearing can withstand what a steel bearing can," Okroy says. This is not only proven by tests in the igus test laboratory. "The bearings are strong and up to all everyday biking situations, even with a full load of 250 kilograms. This has also been proven by our trial tests, in which the vehicle covered 80,000km with a full load." Last but not least, the igubal bearing scores with its low weight of only 26 grams. Comparable metal spherical plain bearings including enclosures and sealing, on the other hand, weigh around 120 grams.

The weight advantage is also used by b&p on the rotatable head of the attachable trailer coupling: iglidur X bushings with very high compressive strength are used here. 

Dry-operating igubal spherical bearings in the steering contribute to a higher durability of the e-cargo bike and reduce the maintenance.

Innovative: Many components come from the e-scooter and motorcycle sector.

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