29. November 2017

Lutz Scheffer about the eMTBs of the future

Since spring 2017, industrial designer Lutz Scheffer has been heading the ADP Concept Design Center in Garmisch-Partenkirchen. As one of the most progressive designers in the bike industry, he develops innovative product ideas here for the ROTWILD bikes of the future. In this interview he gives insights into his development work, talks about the eBike trends of the future and explains his visions of the perfect eMountainbike.

You have been managing the ADP Concept Design Center in Garmisch-Partenkirchen since March 2017. What exactly is your job here?

I think about about future and current Rotwild bikes, in particular E-MTBs. For classic mountain bikes, the major development steps have essentially been taken. Here, only detail work is still required. I develop initial ideas quite freely by drawing pencil on paper and in the further course by means of computer sketches and renderings. Subsequently, the best designs go into 3-D construction. A model of the bike is constructed on the computer using CAD design software. It is important that the practical component is not neglected. Here in Garmisch-Partenkirchen, a number of first-class trails start directly at the ADP Concept Design Center. The alpine environment is both playground and inspiration.

How does the cooperation with the team at the ROTWILD headquarters in Dieburg work on a day-to-day basis?

Each work step takes place in teamwork with the engineers and product managers at headquarters. We see and meet regularly at both locations for this purpose. Designs and constructions are discussed together from the very first step and modified again and again. From an early stage of CAD development, we do a lot of FEM calculations, which in turn significantly influence the design and construction. Bike design is a highly iterative process, which means that many optimization loops are already running in the design phase.

How long does it take to implement a design idea until the first test drive of the prototype?

Before the prototype, which already looks very close to series production, we test the geometry and kinematics with so-called road test carriers. This allows us to gain our first practical experience just six months after the first drawing. It takes at least one and a half to two years until the production bike with all its details is actually ready.

How exactly does this development process work?

There are seven steps: Idea, design, construction, road test carrier, prototype, pilot series, series. Between all points, two to three loops are necessary for fine-tuning. Each milestone takes about three months. But that's only a rough guide, because each project has its own specific pitfalls to solve. Building E-MTBs is significantly more complex than simply developing an MTB, as the battery, motor and controller all have to be taken into account. In the case of Brose motors, we have an influence on the design of the motor controller. We develop the battery completely independently.

How many and which people are involved in such a development process?

Five people are involved in this process at ROTWILD. The team consists of specialists for geometry, kinematics, CAD, FEM and electronics. In addition, there are external employees who develop and manufacture special components at suppliers according to our specifications.

When did you try your first eMTB and what was your experience?

To be honest, I was not very convinced of eMTBs until 2015. At the time, I thought mountain biking was the true sport exclusively in its motor-free form. Bike shuttles and cable cars have been the second choice to get up a mountain all my life. That changed abruptly when I embarked on a large-scale self-experiment in 2016. My stated goal was to ride exclusively E-MTB and to collect as many vertical meters as possible. At the end of the year, there were no less than 250,000 vertical meters on the speedometer, and I was completely infected by the E-MTB virus.

In which areas did you see the greatest need for improvement at that time?

The answer to this question would go beyond the scope of this article. Roughly speaking, the greatest problem is the altitude in alpine terrain. To manage 250,000 meters of altitude per year, I took a second battery with me on practically every tour. My average battery consumption was 750 Wh for just under 1500 to 2000 vertical meters per tour. The 2.6 kg battery in the backpack was a nuisance, since I rode for the most part on alpine trails that required full body effort uphill as well as downhill. Short cranks because of the risk of falling on exposed trails came quite quickly on my bike. In addition, always grobstolligere tires and suspension travel not less than 160 millimeters.

The heavy wear of brake pads was a real nuisance. A brake pad change was necessary once a week after about ten hours of operation and around 20,000 altitude meters. The chain lasted much longer and only had to be replaced every two months. General defects I had during this endurance test only once by a torn speed sensor cable and a defective derailleur hanger. At the end of the year, the motor (Bosch CX) had to be replaced under warranty. He still ran perfectly, just the internal reduction gear sounded like my old coffee grinder and would have in the foreseeable future tooth failure. Forks, shocks and sprocket cassettes I have changed several times, but for testing purposes and not because of acute wear.

How many meters of altitude testing do you do per year?

Ideally, I'll get to 250,000 meters of altitude as in 2016, but at least 100,000 to 150,000 meters of altitude are for sure. A single test bike should have ridden quite a few 10,000 meters in altitude and not just seen the test bench laboratory before it goes into production. With some bikes that I ride for analysis reasons, I think: Have these bikes ever been ridden in the mountains? On all test rides, I like to combine the use of the E-MTB with other sports: In winter with ski touring and in summer with climbing and mountaineering. An E-MTB is an all-season sports device and must function in all weather conditions: In 30 degree sweltering heat on a 1000 meter non-stop rock climb just as in winter at over minus 10 degrees on ice and snow with ski touring equipment on the back.

Where do you currently see the greatest potential for innovation in eMTBs?

Essentially, I see four areas here:

Range increase through adapted battery sizes
Adaptive battery solutions from 750 Wh to 1000 Wh without backpack storage
Better control of the man-machine interface through more ergonomic operation in conjunction with new types of functions on the handlebars
Better integration of the motors into the frame

The transition from mounting to riding and vice versa plays an essential role, especially in difficult terrain. Sliding passages, even if they are only a few meters long, must be easier and more elegant to master.

Technically, the trend is moving from the adaptive to the integrative; in the past, the batteries became a true unit with the frame. Next it will be the turn of the engine: Away from the purely bolt-on motor to the true integral motor built into the frame. This could save even more weight in the future.

In general, the frames and components of eMTBs must become lighter in the future. Every weight reduction counts, even if it is only a few hundred grams! It is by no means so that beyond the 20 kilos everything would not matter.

At the same time, the forks must become stiffer. Because the low center of gravity and the generally greater mass of an eMTB place new demands on the fork. Integrated gearboxes would be desirable, but I only see these in the very distant future. With today's materials, the lower weights and traction-free shifting as well as the enormous bandwidth of a derailleur simply can't be beaten. Wear and tear on a derailleur is far less dramatic than generally thought: With regular oiling and cleaning, there is no significantly increased wear on E-MTBs compared to a normal MTB. Every 50,000 to 100,000 meters of altitude a chain change is necessary, which for the normal user means that he replaces the chain once a year.

Let's take a look into the future: What can we expect in terms of battery power on E-MTBs?

With the current standard of the 500 Wh battery, you are quickly at the end especially in alpine terrain. The frame standard battery will settle between 600 Wh and 750 Wh. Only then are "real" 1500 to 2000 meters of altitude on a full-day tour possible without changing the battery. Saving power is with E-MTBs a fun brake of the first order and also on challenging trails and in the mountains often not possible. Here, from my experience, a support level of 200 percent is the average.

What about improving traction in the future?

Uphill traction is a combination of riding technique, good suspension tuning and frame geometry. Stable, chunky tires are crucial here. In practice, rolling resistance only plays a real role on the flat and on well-paved gravel roads. The pure thickness (volume) of the tire is secondary, because everything depends heavily on the area of use and riding style. My very personal conclusion on alpine trails: here it shows that tends to have medium-sized tires (2.6 ") in difficult conditions the nose in front. Also a mix of rear minimally thicker (2.6- 2.8") and front minimally thinner (2.4"- 2.5") is promising, because you combine both advantages: exact steering precision with healthy air pressure (1.5-1.7 bar) and maximum traction on the front wheel and volume with low air pressure (1.4-1.6 bar) on the rear wheel. I prefer a 29 "front wheel with less volume and chunky tires to a 27.5 "with plus tires.

And what can we expect in terms of geometry, kinematics and weight in the future?

A bike that enables all these combinations by means of variable geometry and variable dropouts is the ideal case. Kinematically, eMTBs have to take into account the three times higher drive forces. An antisquat, as on classic mountain bikes, is no longer necessary, since an e-motor in conjunction with the human generates an almost smoothed drive torque. The spectre of "bobbing" is passé. In turn, it is much more important that the chain hoist is not used to suppress bobbing, as it is on classic bikes without a motor, but that it behaves as suspension-neutrally as possible. The chain hoist must harden the suspension as little as possible, since you also need the suspension as a traction-promoting means on an eMTB uphill.

The weight must clearly become lighter for eMTBs, whereby one must consider the battery separately. An eMTB with too small a battery makes no sense. You have to remain realistic here. Powerbikes with motors that deliver more than 600 watts at peak power and still guarantee an operating time of more than two hours on trails will hardly be produced under 20 kilograms. Lightweight eMTBs with reduced peak power and smaller batteries have potential. Here, however, a significantly larger pedaling own share is to be applied.

What is your vision of the eMTB of the future?

My vision would be an eMTB with 16 to 18 kilos, a 170-mm suspension travel and two kilos of fuel cell with range height for 3000 to 4000 meters of altitude at a stretch. With such a bike, even a "bike park day" without lift support could be completed with one charge. This bike would also have an upsidedown/variotravel suspension fork from 140 to 170 mm and a 200 mm dropper post with tilt compensation.

If that doesn't work out with the fuel cell or it's still a while off, I'd like to see a 1000 Wh battery under four kilos in conjunction with an optional small auxiliary battery that offers another 500 Wh reserve.

Beyond these power bikes, weaker motorized eMTBs will gain in importance. These bikes are significantly slimmer and lighter and are more similar to classic mountain bikes. But here, too, optimum efficiency of the e-drive is the secret to a small, lightweight battery-motor unit with a large reach height. Bottom brackets, angular gears and other power redirections are efficiency killers in the drivetrain: Here we will have better technical solutions in our quiver in the future.

My personal concern is to ensure a growing acceptance of the eMTB in the round of nature sports. Free open access to trails and paths is a basic requirement for practicing eMTB sports. Tuning eMTBs destroys any legitimacy to legally equate to mountain biking as cycling. Anyone who tunes their eMTB is acting highly irresponsibly towards other bikers and the eMTB movement as a whole.

The 25 km/h cutoff for the engine is definitely not a problem off-road, especially uphill, on the usual MTB trails. Other motor systems that are difficult to pedal beyond 25 km/h should not tempt you to tune despite everything. The smooth transition when the motor support runs out and the loss-free pedaling when the motor is switched off, as the Brose motor can do, are of crucial importance here. This means that even beyond 25 km/h you can enjoy biking to the full.

Lutz Scheffer provides more insights in the presentation of the ROTWILD Big Mountain R.X750 and in our podcast ROTWILD meets ... Lutz Scheffer, Off-road fan, bike philosopher & EMTB product designer.