Electric bikes in education

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Introduction

Electronic bikes (ebikes) most often refer to some kind pedal-assisted bicycles.

Ebikes offer interesting opportunities for education:

  • Technical design and STEM principles: An ebike as learning object can be used to study mechanics, physics and electronics.
  • Technical design (advanced): At least one of the better designs was made in collaboration with an engineering school
  • Technical design and fabrication (DYI): E-bikes can be hand-crafted, i.e. be used as ambitious object in a design and fabrication class
  • Teaching evaluation methodology: Evaluation of e-bikes is relatively easy, and could be conducted as a class project

Ebikes in education examples

(this list needes completion)

Collaboration with engineering schools

A good example is the Swiss Stromer developed in partnership with Bern University of Applied Sciences (Engineering and Information Technology), Lucerne University of Applied Sciences and arts and a Swedish Designer.

Ebikes in fabrication classes

This is related to fab labs and other digital design and fabrication initiatives. For starters, one can upgrade a normal bike to an ebike using one of the many commercial kits.

A good example is the annual e-Kart competition (in french), e.g. Vierzon International and Educational Meeting of Electrical Gokart e-Kart 2013 in France

Ebikes for STEM teaching

Understanding the electrical and electronics parts of an e-bike could be an interesting activity for a vocational school training electricians and related professions. We know, for example, one example of a french school who acquired a ebike for that purpose.

As you can see below, there is quite a large combination of features in current ebikes.

Ebikes in other classes

Since E-bikes are fairly simple "products" as compared others they are ideally suited for evaluation studies, marketing classes, etc.

A good example of report is the report (in German/French) in the ATE/VCS VeloJournal made in collaboration with an engineering school.


Designs

Types of designs

We could distinguis roughly types of e-bikes

  • So-called Pedelecs, i.e. the motor only turns when the user pedals. In most systems (see legal restrictions below), the motor will fade out and cut assistance at 25km/h or 45km/h (s-pedelects).
  • So-called Power-on demand. The user will turn a throttle and can either pedal or not. Such designs are illegal in most countries, although some models like the Ezee were modified to require the user to pedal and therefore become legal. Others will cut assistance at 20Km/s when not pedalling.

One also can classify designs according to usage. E.g. the German site distinguishes between 11 types:

  • Urban-easy: Light and easy to use, small range
  • Urban-business: Fairly speedy and good range
  • Urban-folding: Take it in your car or public transportation
  • Comfort - City comfort: Confortable, includes full equipment (e.g. lights)
  • Comfort - Classic: Like the above but comfortable position and highly reliable
  • Comfort - Reha: For rehabilitation patients
  • Leisure - Tour: High range, good climbing, full equipment, carry lots of stuff
  • Leisure - Sport: Speed, power, off road capbable, and range
  • Leisure - Wellness: As above, but easier to use
  • Transport - Family: Strong (bring a kid along)
  • Transport - Business: Carry lots of weight, e.g. Pizza boxes

We would add to this:

  • Commuting: High speed, high range and full equipment, easy to use in city traffic.

Power system

Motors

Motors can be front or rear wheel hub motors or in the middle. All decent motors are brushless, i.e. there is not friction that would reduce its lifetime.

  • Front wheel: cheapest solution since it doesn't need to interact with the gears, a bit dangerous when breaking on wet roads
  • Rear wheel: Most possible raw power, some 500W moters do have overheading problems. Until recently, this design required crank shifts. The only exception is the Grace easy that has 3 gears.
  • In the middle near the bottom bracket: The motor typically interacts with the bracket and then indirectly the chain.

Power output

  • Pedelecs: 250-350W (in some countries only 200-250W are allowed and the output is electronically locked)
  • S-Pedelecs: 350-500W
  • Other: Up to anything ....

Horse power is not everything. Torque also counts. Loosely speaking, torque defines how much force is applied for turning the wheel. Typically, you get:

  • 20Nm for Pedelects
  • 30-40Nm for the faster S-Pedelecs

More torque means better acceleration. Typically, rear wheel motors have higher torque.

Main makers: Panasonic, Bosch, Bionix, Acron. Many makers have their own motor, though often (most of time ?) it's just a custom version of some known brand. E.g. Stromer uses a special Bionix line. Stöckli seems to have its own "go-swiss-drive".

Batteries:

Battery position is most often somewhere in the middle. Some high-end models integrate the battery in the frame. Others on top of the rear wheel. Many models offer a choice of batteries, i.e. smaller/bigger and also with respect to quality.

Currently, most batteries are either NiMH or the lighter Ion-lithium batteries.

  • Energy: between 250Wh and 500Wh
  • Voltage: typically 36V
  • Capacity: typically between 8 and 20Ah.

More output means more weight and more money. A high-end battery costs at lot. E.g. the big Swiss Stöckli 23.2Ah costs 1800 CHF (1400 Euros). The small 11Ah is 990 CHF.

Main makers: Panasonic, Bosch, Samsung

Electronics and motor control:

All pedal-assisted ebikes offer to control the degree of assistance (from none to high), usually about 3-5 levels. Support ranges from 30% extra power to 300%.

  • Little = 30 to 50% (little support, e.g. for exercising, slow driving and large range)
  • Normal = 100% (good support)
  • High = 200 to 250% (very little effort on your part)
  • Boost = 300% (in this mode you can easily climb steep roads)

The motors can be controlled in various ways

According to Wikipedia (March 2013):

For switching or control of the motor, there are several possibilities:

  • Measuring the force or torque on the signal of a force sensors on the pedals, the pedal crank, the chain or at the wheel
  • Measurement of treading on the signal from a revolution counter or threshold switchs on the crank, or at another suitable location
  • Measurement of both force and the speed
  • Measurement of acceleration or drawbar force at the push trailer
  • Measuring electrical values in the serial hybrid (pedal generator)

In addition, the speed of the vehicle are measured on the wheel, in particular, for example, to drive the motor from 25 km/h off. The measurement can be further processed mechanically or electronically and is used to control the motor on and off or to regulate a control function based on continuously.

The fed power is based on the sensor data (force sensor, crank speed, ground speed) is calculated based on the chosen level of support from the motor controller. The so-called support levels, that is, how much the motor supported in addition to the driver's performance lie in horizontal drive 5-400 percent.

Examples:

  • Stöckli E.T. Urban: Force and speed sensor
  • TDS Impuls Trekking XT: Force, Speed, Pedal rotation frequency, inclination
  • Flyer R-Series: Force, Speed, Pedal rotation frequency
  • Stromer: Force and speed sensor
  • Dolphin Express: Pedal rotation frequency

It is very important that sensors are tuned for good usability. Although ebikes do need some adjustment, some do much better then others, e.g. most testers seem to prefer the TDS Implus over the Stöckli E.T. over the Stromer (which model?) with respect to reactivity. In addition, various combinations need different behavior. E.g. on some bikes like the KTM Amparo, you would have to pedal fast (effortlessly though) in order to get more support.

Controllers:

A decent controller should offer at the least the following

  • Energy display: charge level
  • Speedometer
  • Selection of output: Should offer at least 4 degrees of assistance (none to high)

Optional:

  • Boost mode and push assistance
  • Regenerative breaking, current comsumption, kms to go, etc.
  • Trip data

Bicycle part

Frame

Frames are usually made from aluminum since both the motor and the battery will add weight.

Gears

Gears are either in rear hub (typically for models with a motor in the middle) or derailleurs (for models with a rear hub motor). Nearly all models require manual shifting, but some models exist that will select a gear to match your cadence, e.g. the NuVinci Harmony.

  • Hub gears usually have something like the 7 gears Shimano Nexus or the 8 gears Shimano Alfine. Just 3 are not enough for hilly places, even if you can compensate with high assistance.
  • Derailleurs: Usually between 10 and 30 gears. Most better models use a Shimano SLX or XT.

Brakes:

Ebikes should have strong brakes, either disc brakes (preferably hydraulic) or hydraulic rim-brakes (e.g. a Magura HS 11). Some models offer regenerative braking, i.e. an interface with the motor and the battery to generate energy when you break.

Suspension

Some argue, that an ebike should have some kind of front suspension, i.e. be able to cope with potholes at higher speed. However, in countries with flat roads (e.g. Switzerland, Germany or Holland) you don't need that extra weight for extra price if you stay on roads and/or drive slowly in difficult terrain. Some makes (like the Stromer) let you choose.

Price

  • Lowest: Around 500 Euros in mass retailers like the German Aldi. Probably a good quality/price relation, although makers of pricier bikes claim that these are dangerous. They are not more dangerous than the models these guys sold only a few years ago ...
  • Lower mid-end: 1000-1500 Euros (best buy for city usage if your budget is low)
  • Higher mid-end (best buy for city usage): 2500 to 3500 Euros
  • High end (best buy for commuting and trekking): 3500 to 5000 Euros. E.g. a simple Stromer ST with the larger Battery plus accessories (light, fenders and luggage) would cost about 4000 Euros in Germany.
  • Very high end: Up to anything, i.e. custom bikes

Of course, you always can get nice bargains for older "last year's" models.

In general, more expensive bikes are better. However, this is just a trend. E.g. the "Kassensturz" Consumer program from our state TV found in a 2012 study confined to an engineering school, that "Supermarket" bikes, e.g. the 1400 CHF (1200 Euro) "Leopard" bike from COOP did very well. Evaluation is "good" (almost the same as the three times more expensive 25km/h Stromer). They also pointed out a very bad model from a discounter. In other words, you can find good cheap models, but read the tests first.

Legal restrictions

Most countries put restrictions on specifications of e-bikes:

  • Switzerland defines two categories of so-called Pedelecs: 25km/h (16mph) and 45km/h. Both require that the user pedals. Limited non-pedaling assistance is allow for the second category (S-Pedelecs) that is assimilated with mopeds and require a vehicle permit and wearing a helmet. Germany has a similar solution.
  • France, Australia and the UK only allow 25km/h bikes.
  • In the USA, each state has a different regulation. For faster models, a driving licence, helmet, etc. can be required.

Standards:

  • EU: EN15194 (EPAC – Electrically Power Assisted Cycles) defines the use pedal-assisted less than 25k/h bikes: "Cycles with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of 0.25 kW, of which the output is progressively reduced and finally cut off as the vehicle reaches a speed of 25 km/h or if the cyclist stops pedaling.”

Hacking

  • Most 25km/h bikes can be easily hacked to go a bit faster. This can be very easy, e.g. it takes a few seconds for the Panasonic middle drive and some hours for others. In the latter case, e.g. Bosch motors, you may have to bridge a chip that will drastically reduce power above 25km/h. On YouTube, you can find videos that teach you how. Else, search the forums. If you use the bike for commuting and you got a model with good brakes, there is nor reason for going at 25km/h if you can get 30 to 35...
  • Some 25km/h bikes (pedelecs) can be made to go a lot faster, i.e. the ones that have 350W motors can support up to 45km/h. In order to reduce production costs, the same motor can be used both for pedelec and s-pedelec versions of the same model. However, the s-pedelec version may have better brakes, a different frame, etc.

Some interesting designs

(As of spring 2013, i.e. it maybe be totally outdated sometimes in the near future)

High-end commuter bikes

Below a list of good well-looking designs for 45km/h bikes that are suitable for both city traffic and commuting and that are legal in some countries in specific versions. Currently, I am thinking of getting one of these - Daniel K. Schneider (talk) 01:08, 27 April 2013 (CEST)

More traditional
  • Kalkhoff Endeavour BS10, made in Germany: Has a new Bosch 400Wh/11.1Ah battery and a Bosch 350W motor
  • Triton 45. This bike won some German tests in this category. Same motor and battery as above ?, 22.6kg.
  • Bulls Green Mover E-45, 735 Wh/20.4 Ah large battery, full accessories, 29.3kg

Both Swiss bikes (the Stromer and the Stoeckli) are very nice designs and - it seems - easy to handle. Reliability for both does not seem to be up to Swiss standards. I don't know about the BH Neo Nitro. Given its relatively low price, it may be the best buy in this category, and Spain's industry does need some help ;) Both the Kalhoff and the Stevens may be more reliable and easier to use than the more sexy Stromer/Stöckli/BH emotion designs. But they got less power and less "punch".

Good city bikes

There are dozens of good 25Km/h pedelecs. Our advice is to go the nearest good e-bike store and get it from there, because e-bikes may need good support. Only if you like servicing a bike yourself is buying from the Internet a good option. As of Spring 2013, a good benchmark to compare with is the Austrian KTM Amparo also called KTM Severo 8M or the German Kalkhoff Impuls or Agattu series. It has a reliable Panasonic middle motor and a good battery. If you want a more sexy design, try the SMART from the urban car maker of the same name.

High end sports bikes

  • Both the Stromer and the Stöckli above have configurations without accessories (fenders, light, luggage carrier, etc.)
  • Grace easy, made in Germany: 350W rear wheel Bionix motor, rear wheel motor, 3 (only) hub gears, carbon drive (no chain), 19kg without equipment. You can add fenders, luggage carriers, lights and suspension fork. Both pedelec and s-pedelec version.
  • Specialized Turbo, similar design as the Stromer, 21.5kg without any equipment. Very expensive ($6000). Don't know if standard accessories exist.

Near future

Even bigger players now move in, e.g. the BWM Cruise is a very traditional build. SMART has a more original model. Others just go for cool prototypes, e.g. Audio and Toyota. In the future you may get one of these for reduced price if you get a new car ...

Do it yourself

Bibliography and links

Overviews

User communities and websites

All in German (sorry, but Germany is the Pedelec country together with Switzerland)
In English

Some tests

(2012/13)

Do it yourself

Other

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