Author: Eliott Wertheimer

The FX is sold out for delivery in May and 10 days left for 25% DISCOUNT

Taking our bikes from paper directly to you and making them your new favorite way of commuting, cycling or just having fun has truly been a formidable adventure and keeps getting better!

The FURO community is growing day after day and we have officially just sold out our batch of FX for delivery in May. The SIERRA is almost gone as well with only 2 left in stock.

As most of you are aware, our 25% discount is also ending very soon. You can rest assured that it still applies to all purchases made through our website until it expires. This means that our next batch of SIERRA and FX is still covered by the discount until the 15/05. It is currently planned for delivery in September, although it will most likely come earlier than this as we are working very hard to accelerate our production rate and optimise our supply chain.

If you are thinking about getting a FX or a SIERRA, we strongly advise to make the most of the discount, particularly as our next batch will also have a limited stock.

We are always available and very happy to help you, so if you have any questions or requests please don’t hesitate to contact us.

The Physics Behind Electric Cycling Through Numbers

Our stock of FX and SIERRA for delivery in May has almost run out, and that is a lot earlier than we anticipated. You guys are loving it and to celebrate that, we are going to give you a short but complete article on the physics governing your ebikes rides.

Let’s start with the protagonist itself, the ebike, here we will have a look at the SIERRA in particular. The SIERRA is made of a full carbon frame which has to be structurally strong enough to support the sum of your weight, the ebike’s weight with all its components, and the weight multiplication and shocks due to bumps and other obstacles on the road. In addition to all the typical bicycle equipment (disk brakes, gears, chain pedals, wheels, etc) the SIERRA’s frame also has to carry a motor, a battery, an electronic controller and a computer. These components are all relatively heavy with respect to the frame of the bike but remain light once you add your weight to the equation, even for the skinniest of you.

SIERRA Configuration

The SIERRA is equipped with a torque sensor which measures how much pressure you are exerting on the pedals. In turn, it sends a message to the controller which calculates how much power from the motor is immediately required. At the same time, the computer scales the controller’s calculations with respect to the assist level you are set on. Eventually, the controller which is connected to the battery, opens a channel between the battery and the motor and allows high power currents to flow in a certain pattern so as to activate the motor and power your ride.

This then makes you go forward and pick-up speed. We will now focus on what is happening once you have reached a speed of 20km/h and are accelerating by 1km/h per second or reaching 25km/h after 5 seconds on a flat asphalt road. According to the second law of Newton, all the forces acting on the bike and yourself while you move forward are equal to your total mass multiplied by your acceleration. This can be written:

with F the sum of the forces in Newtons, m the total mass in kgs and a your acceleration in m/s².

Sir Isaac Newton

The forces acting on the bike and yourself while you are moving are:

  • Your own, applied through the back wheel of the SIERRA: we will call it Fy and it is measured in Newton
  • The motor’s, applied through the backwheel and the chain of the SIERRA: we will call it Fm and it is in Newton
  • The aerodynamic drag, due to your movement through the air of the atmosphere, which can be calculated in Newton using the following equation:
    with Cd the coefficient of drag, p the density of the air, V your velocity and A your frontal area.
  • The rolling resistance of the tyres on the road which can be calculated in Newton using:
    with Cf the rolling resistance coefficient of the tyres on the road, m your mass in kg and g the gravitational constant g=9.81m/s², m*g is essentially the force in Newton exerted downwards by your weight on the bike.

FuroSystems SIERRA Sum of Forces

First of all, we can calculate the drag. In a standard relaxed cycling position on the SIERRA, your frontal area is likely to be 0.6m² and your coefficient of drag: 1.15. The density of the air at sea level is 1.225 kg/m3 and your velocity is 20km/h which is equivalent to 5.6 m/s.

So we get: D = 0.5 * 1.15 * 1.225 * 5.6² * 0.6 = 13 N.

The rolling resistance coefficient of bicycle tyres on asphalt is equal to 0.004, assuming you are 75kgs, the weight of the SIERRA being 20kgs, your total weight becomes 95kgs.

Hence, your rolling resistance is Fr = 0.004*95 = 0.38 N.

So the sum of the forces can now be written:

Fy + Fm – D – Fr = m*a

with m your total weight (95kgs) and a your accelerations in m/s².

Also note that the sign of the forces in the sum depends on the direction these forces are acting. If they act in the direction of the movement, then they are positive, if they act in the opposite direction, they are negative. We can replace the variable with the values we calculated knowing that an acceleration of 1km/h/s is equivalent to 0.28 m/s²:

Fy + Fm – 13 – 0.38 = 95 * 0.28 which is equivalent to Fy + Fm = 40 N

We know that the wheels of the SIERRA measure about 0.70m in diameter and therefore 0.35m in radius. We also know that torque is a force multiplied by a distance. Hence, the torque generated by the combined efforts of your legs and the SIERRA’s motor is 40*0.35=14 Nm. We can even get the total power by multiplying this by the angular velocity of the wheel, or the speed at which it rotates. We know that its perimeter is 2 * PI * Radius = 2.2m. As we are going at 5.6m/s, this gives 2.5 rotations of the wheels per second or an angular velocity of 15 rad/s (multiply by 2 * PI).

Hence, on a flat asphalt road, in order to maintain an acceleration of 1 km/h per second while being at a velocity of 20km/h, the total power needed from you and the SIERRA together is 15*14= 210W.

As the BOFEILI mid-motor of the SIERRA produces 350W of continuous power and more than 600W of peak power, at this cadence you will only be exploiting a third of the power of the beast. Depending on your assist level, you can either fully provide the 210W through your legs or entirely rely on the SIERRA, it’s your choice and that is the magic of electric cycling!

Do not hesitate to ask questions in the comments, we will be happy to answer them if anything needs to be made clearer!

First batch shipment and end of preorders

It’s official! Our first production batch is currently at sea and will reach our European warehouse around the 15th of May. We will then unload our containers and ship your bikes to you at lightning speeds, you will receive them within 2-3 days.

It’s been a great adventure getting our bikes from paper right to your home and we are pretty sure that you won’t be disappointed! This also marks the end of pre-orders for the FX and the SIERRA. On the 15th of May, all 25% pre-order discounts will be discontinued. Our stock is also limited, so for those of you thinking about getting one of our great ebikes, now is the time 😉

Our mission to get commuters and cyclists beautiful, affordable, high performance ebikes is going better than ever, and we will keep working to get you the best, always!
Thank you all for your support!

3D printing and prototyping

Nowadays, more or less everyone has heard about 3D printing to some extent. It’s used all over the world by individuals or big companies to transform computer models to real life objects. For a bike R&D and manufacturing company like FuroSystems, 3D printing is vital in order to be able to iterate fast between designs while keeping prototyping costs low. It was essential in bringing the FX, the SIERRA and the L1 to life. But how does it work exactly?

When designing a new part or component, engineers use CAD (Computer Aided Design) software such as Solidworks or Autodesk Inventor. These allow to create shapes and patterns which aggregate to solid 3 dimensional objects. The CAD software then allows to save this object in the form of a STL file which basically maps the surface of the object with triangles. This file is then uploaded to the 3d printer which reads it and proceeds to create the object vertically layer by layer following different processes described below.

Extrusion deposition is the method employed by most desktop 3D printers and consequently the most widely used in 3d printing. Here, a filament of thermoplastic (most common) or metal is passed through a heated nozzle to melt, deposit on a surface and harden instantly. The nozzle turns the flow of material on and off while motors displace it according to the 3d coordinates contained in the STL file.

Another process consists in the binding of granular materials. Powders of materials such as metals or plastics are deposited on a bed. Powerful lasers or binding agents are then applied to it according to the model’s coordinates to fuse and harden the beads layer by layer, starting from the bottom and progressing upwards. Technologies using this process are Selective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM) or Electron Beam Melting (EBM).

Photopolymerisation is also an interesting 3D printing technique. Processes such as Stereolithography (SLA) are based on the hardening of liquid materials into solid shapes. Here, baths of liquid polymers with photosensitive additives are exposed to controlled lighting which leads them to harden. Again, this process is applied from bottom to top through little increments where the shape being built is slowly displaced downwards as new material is solidified. This technique allows to obtain smoother plastic surfaces and therefore reduce the need for part post processing (smoothening, etc).

In the end, 3D printing is a real revolution in hardware development. It allows to materialise designs at record speeds and with similar aesthetic properties to finished products. Of course, engineering characteristics such as strength cannot be similar to those in a properly manufactured products but they are sufficient to test shapes, details and configurations before moving to the factory machinery. In turn, 3D printing saves designers considerable amounts of time and money and enables smaller entities to come up with great products and compete with the big guys, often less inclined to innovate from their comfortable leading position.

Why are ebikes so good for you, and everyone else?

This is going to sound cliché, but FuroSystems was genuinely started from the following thought: what are some of the biggest problems in our society right now? And can the latest technologies combined to clever engineering solve them?

Global population is growing which with urbanisation is causing population densities around cities to increase. In addition, personal transportation systems such as cars, vans and motorcycles are bulky and noisy. Add to that the fact that about a century ago, we chose fossil fuels over electricity (rightly so at the time), we now have a nice combo of polluting, traffic stimulating and impractical vehicles. As this has even become deadly, we urgently need something better.

Traffic Jam

At FuroSystems, we really think that the clear solution is electric bicycles. They are now powerful enough and offer sufficient autonomy to take a rider anywhere, around any city in the world, for multiple days. They are compact, fast, quiet and clean. This is why we decided to use our expertise to help accelerate our society’s transition to this amazing and fun mode of transportation. How? By making them better, more practical, more attractive and more affordable.

As with any great innovation, electric bikes have their sceptics, the main argument is that it’s essentially a way to cheat cycling, something for the lazy.

According to Steve Garidis, the UK’s Bicycle Association’s operations director : “It’s quite difficult to explain what [an ebike] feels like: you’re still cycling but it’s like being an Olympic athlete; you can go faster and longer; hills are less effort. The acceleration is quite fun, even for the most sceptical grown up.”

Happy FuroSystems Electric Bikes Customers

So yes, ebikes do make it easier. They allow older or handicapped people to go places they can’t anymore or never could, and ride with their loved ones. It makes commuting and cycling more manageable. However, they also allow everyone else to experience a new level of acceleration, speed and performance. They don’t remove the effort if you still want it, they just make everything better, more intense, it’s an enhancement of your physical capacities whether you are fit or not. For example, our bikes the SIERRA and the FX give you the option of riding them unpowered making them feel exactly like normal bikes, but they also allow you to multiply your acceleration, uphill capacity and speed, whenever you feel like it. To make it even simpler, they are a 250 W to 600W power add on to your body which you can choose to activate on demand.

Deciding to use an ebike for your commute instead of your car, scooter or moped is probably the best thing you could do today. No more pollution, no more noise, no more fuel, no more insurance and a healthier lifestyle. Folding bikes like the FX are also incredibly more practical, particularly when they are that light, while staying very powerful and offering great range, not far off from that of a 50cc petrol scooter.

Electric bicycles are the mode of transportation of the future, they literally solve every single problem you could think of in modern transportation and greatly enhance cycling. In addition, battery technology is close to making significant leaps forward with technologies such as solid state chemistry, super capacitors or 2D materials such as graphene. You can trust that we will be here to implement each of these advances in your FuroSystems ebikes as soon they are out!

A little eye candy for those of you that stayed with us to the end 🙂

Carbon Fiber, the wonder material: what and why?

Most of you will have heard about it. Carbon fiber, the wonder material that makes everything lighter and stronger. It’s used in supercars, aerospace machinery and the FuroSystems SIERRA and FX (could we call them superbikes?).

FuroSystems FX Full Carbon Fiber Folding Ebike

So what is it? Its basic element is carbon, it’s made of 6 electrons, 6 protons and 6 neutrons and without it you wouldn’t exist, nor would any life on Earth. When you overcook your food or burn some wood, the residual ash is mainly carbon. Carbon fibers consist in these atoms being assembled in crystals and bonded in a direction that is approximately parallel to the fiber’s long axis. Each fiber is between 5 and 10 micrometers (millionths of a meter) wide, or 2 to 20 times narrower than a human hair. This configuration gives them a strong strength to volume ratio. Individual fibers are obviously relatively weak on their own but once woven together they lead to a very strong cloth.

Carbon Fiber Cloth

At this point, carbon fiber is just a fabric similar to the ones made of cotton for your tshirts, only much stronger and much more expansive. To transform it into a useful and solid engineering material, the cloth is mixed with a plastic resin such as epoxy to form a composite also called carbon fiber reinforced composite. The manufacturing process usually consists in a technician laying the fibers on a mould, painting them with the chosen resin and then baking the assembly to obtain a part with the desired shape. The result is an extremely rigid and very high strength to weight ratio component.

Carbon Fiber Airplane Wing

Carbon fiber reinforced composites (CFRP) are about ten times stronger and 5 times lighter than steel and eight times stronger while 2 times lighter than aluminium. In addition, their very manufacturing removes the need for welds and allows for sleeker and smoother shapes. It is true that CFRP tend to be more brittle and crack slightly more easily than aluminium or steel. However, this is easily compensated through design by ensuring that the load necessary to lead to a crack will always be much larger (MUCH LARGER) than the greatest load your bike will ever experience during its use.

Also, the fact that carbon frames cannot be fixed once broken is a myth, they absolutely can, in a very rapid and discreet way as well. After all, if it’s trusted to make the wings of giant machines that fly hundreds of kms in the sky, costing hundreds of millions of dollars and carrying hundreds of people (that’s a lot of hundreds), then it can most likely be used to enhance your biking experience, and that’s exactly what we’ve done. Aerospace engineering at the service of happy riders!

This video details well the frame manufacturing process used by KOENIGSEGG and FuroSystems:

How do electric motors in ebikes work?

To continue our educational series on the physical principles behind electric bicycles, we would now like to talk about the brushless DC motors that equip your bikes. Without those, there would be no sleek and smooth ebikes like the FX and the SIERRA.

First of all, an electric motor is an electrical to mechanical or electro-mechanical energy convertor. It converts electrical energy to mechanical movement (rotational or translational). They were first invented by William Sturgeon in 1832, 44 years before Nikolas August Otto created the first practical petrol engine. Our society went the petrol direction because of the wide availability and the greater energy density of fossil fuels as described in our previous article.

first practical electric dc motor

Today, there exists multiple types of electric motors: brushed, brushless, uncommutated, permanent magnet stators and wound stators. Most of these exploit the forces created by magnetic fields and possess some kind of internal mechanism.

Let’s look into the simplest DC motor possible as shown in the picture above. It is made of a stator and a rotor. The stator does not move and is equipped with magnets. The rotor is a coil or armature placed within the stator through which a current passes. This current generates an electromagnetic field aligned with the center of the coil. The direction and intensity (or magnitude) of this current determines the direction and intensity of the magnetic field produced by the coil. The following picture represents this phenomenon, with I the current. This is also called an electromagnet as it creates a magnetic field when electricity passes through it.

Magnetic field produced by current running through a coil

The magnetic field created in the rotor attracts and repels the magnets placed in the stator (positive pole attracts negative pole and negative pole attracts positive pole). If everything is kept equal the rotor will consequently turn a maximum of 180 degrees before stopping. To keep this rotational motion the poles of the electromagnet that is the rotor have to be switched, guess how? … By switching the direction of the current passing through it as shown in the following animation:

DC motor rotating

The question is, how do you switch the current’s direction when your battery is always connected in the same way? Well, in brushed motors, actual conducting brushes make contact with the rotor as it spins and sequentially reverse the current going through it, in turn switching its polarity. However, the obvious problems with using brushing contacts to switch the current are that the whole thing heats up faster and therefore needs a bigger cooling system, it creates sparks, it wears out and consequently limits the speed of the motor.

This is where modern computers and electronics come in. They allowed us to get rid of those brushes to create Brushless DC (BLDC) Motors, the wonderful components that make your favorite electric bicycles possible! Essentially, a BLDC motor is a brushed DC motor turned inside out. The rotor is made with permanent magnets placed in the center of the motor while electromagnets are placed around it in the stator. A computer, using powerful transistors, then switches the polarity of these electromagnets which leads the rotor to turn. This enhances how well the energy stored in your battery is converted to movement, reduces the need for maintenance and removes the cap on speed as the only limit is now the power available in your system and the speed at which your computer can switch the electromagnets.

Brushless DC motor in electric bicycles

More specifically, the computer in your ebike is called a controller and extracts current from your battery in order to switch the electromagnets in the stator of your motor.

Hopefully, this is all kind of clear, if you have any questions, do not hesitate to ask in the comments!

How do Lithium-ion electric bicycle batteries work?

As we just made the preorders for the the bigger battery version of the SIERRA, the SIERRA MAX available, today appeared as a great opportunity to thoroughly explain the fundamental principles and physics behind Lithium-ion batteries and why they currently are the state-of-the-art in electric bikes.When looking at batteries, you basically want to maximise stored energy while minimising volume, weight, and price. As a society, we have been primarily using fossil fuels for personal transportation. This is because this type of of power source is really good at storing a lot of energy in a small volume and with a low weight while remaining affordable. Now that these chemicals are slowly but surely running out, and we witness how impairing they are to our sustainable development, cleaner options such as rechargeable electric batteries are progressively becoming the norm.

There are many types of those: Nickel-Cadmium, Lead-acid, Silver-Zinc, Lithium-Ion, etc. The following graph produced by NASA shows that Lithium-Ion chemistry has the highest energy density and is consequently the best choice to store electrical energy in small volumes and low weights.

Electric bike Lithium-Ion battery energy density comparison

While still 60 times less energy dense than gasoline, Lithium-ion cells are the best available alternative to store electric power safely and economically in personal vehicles.

The following diagram simplifies the discharge mechanism in a Lithium-ion battery, which is tantamount to the motor pulling power from it. Positive Lithium-ions travel across an electrolyte and a separator from an anode towards a cathode, which are two dissimilar conducting materials. The cathode then becomes more positively electrically charged than the anode. This creates a voltage between the anode and the cathode, which is essentially a driving force that pushes electrons between two points. The higher the voltage, the higher the force. This can be visualised as a waterfall. The taller the waterfall, the greater the force driving the water from its top to its bottom.

Electric bicycle Lithium-ion battery discharge mechanism

This voltage drives electrons across the electromechanical systems of your ebike. They leave the anode to go through the controller, followed by the motor and back to the cathode. As electrons move across the system, the voltage of the battery goes down. The charging process is the exact opposite. A voltage is applied across the cathode and the anode which forces electrons to move in the opposite direction and the Lithium-ions to go back towards the anode. This restores the driving voltage between the anode and the cathode for later discharge.

Electric bicycle Lithium-ion battery charge mechanism

These chemical processes are contained within cells. Today most cells, whether in laptops, cars or ebikes, are cylindrical pieces of metal. This allows to contain pressure better and increase batteries’ safety and resilience to their environment. These cells usually provide a nominal voltage of 3.6V. This means that they reach 4.2V when fully charged and progressively go down to a safe minimum of 2.5V during discharge after which a battery management system shuts your battery down to preserve its capacity and health.

Lithium-ion cells have to be connected and assembled to build a battery with a total voltage that is enough to drive its target electro-mechanical systems; the controller, motor and screen in our case. Individual cells are packed and connected in Series to increase the total battery voltage to the required value (for example, 36V). Once this value is reached, these series of cells are packed in parallel to reach the total battery capacity, the value usually quoted in Ah. An average cell packs 3.6V and 2.5Ah, hence a battery producing 10Ah at 36V most likely consists of 4 groups of ten cells connected in series, which are then connected in parallel. I know that this is tough to get your head around but the following diagrams, courtesy of Cadex, should help you understand:

Electric bicycle Lithium-ion battery series assembly

Group of cells assembled in Series to increase total voltage.
Electric bicycle Lithium-ion battery parallel assembly

Group of cells assembled in Parallel to increase total capacity once the desired voltage is reached.
Hopefully, you now have a better idea of the internal workings of your ebike or more generally your laptop, phone or car.

If you have any questions, do not hesitate to ask in the comments!

Exclusive Pre-orders on our First Production Batch Now Available

We are proud to announce that after years of development, hours of testing and tens of iterations, our innovative full carbon high performance folding and mountain electric bikes are finally in production!

Our inspection team will make sure that throughout each step of the fabrication process, from frame moulding to assembly, the highest standards of manufacturing are exerted. This is particularly important to us as our bikes are not only truly revolutionary in design and practicality but also carry our vow to provide you with only the best quality at the most competitive prices achievable by technology today! There will always be cheaper bikes, but those offering similar performance, aesthetics and build quality will also always be significantly more expansive.

We have made the FX and SIERRA available for pre-order at a significant 25% discount until they arrive in our European warehouse. This is to thank you for your trust and being one of the pioneers of our community. Once our ebikes are in stock, first backers will be delivered and pre-orders will be discontinued to allow for direct orders with shipment within 2 weeks at retail price.

We are always available to answer your questions and talk with with you. You can contact us here.

Let’s change cycling and modern transportation together!

Thank you for your trust!

You can obtain more info and access FX  pre-orders for here, and here for the SIERRA.

Eliott Wertheimer


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