Cycling Without that Pesky Peddling

Category: Others/ Misc

Presentation Description

For now it appears there is a simple solution to cycling’s biggest flaw – use electricity to turn the pedals. Table of Contents Some brief history of the electric bike. The science behind the e-bike. The batteries. Hub motors. The frame. Wheels and brakes. Different types of electric bicycles. Full power. Power assist. Legal status. Electric scooters


Presentation Transcript

Cycling Without that Pesky Peddling:

Cycling Without that Pesky Peddling


Introduction Bicycles are a very cheap, healthy and a simple form of transport available to everyone. Unfortunately bicycles are best suited to flat terrain, which is why they are so popular in holland and the like where there isn’t a hill in sight. However for most of us who live in undulating or worse hilly terrain or countryside cycling soon becomes far more trouble than it’s worth. Peddling up long shallow gradients let alone a hill can drain you of energy and leave you demoralized, panting for breath, and with quivering thighs that no longer seem capable of turning the pedals. Most of the time it is easier to get off and walk, pushing the thing. But it doesn’t need to be this difficult. For now it appears there is a simple solution to cycling’s biggest flaw – use electricity to turn the pedals.

Table of Contents:

Table of Contents Some brief history of the electric bike . The science behind the e-bike . The batteries . Hub motors . The frame . Wheels and brakes . Different types of electric bicycles . Full power . Power assist . Legal status . Electric scooters .

Some Brief History of the Electric Bike :

Some Brief History of the Electric Bike If like me you have never seen an electric bike before you problem imagine that they are some modern invention. However like the electric car, scooters and mobility\golf buggies they have been around for some time. Indeed a flourish of patents for electric bicycles designs first appeared back in the 1890s. These early designs using battery powered DC motors to drive either one of the front wheel, back wheel or crankshaft were re-invented in the 1990s and briefly went into production. An example of this was the zike which was built upon early design principles by adding torque sensors and power controls. Despite this sales were slow and few other electric bicycles were in production but by the late 2000s the technology had improved to the extent that they had a range of between 25-30 miles at a top speed of 20 miles per hour. These e-bikes then began to become more popular in europe and the US.

The Science behind the e-Bike :

The Science behind the e-Bike The basic concepts behind the electric bicycle have not changed much since the early patents back in 1890. There are only four key components to an electric bike, 1) a sturdy frame, 2) a battery, 3) a DC electric motor, 4) wheels and brakes. The batteries are the power source that will drive the wheels so that you won’t have to, so let’s start there.

The Batteries:

The Batteries In early designs the electric motor needed to be powered by a large heavy battery but that was self-defeating as you used half of the power just to drive the battery along. However, recent advancements in battery technology has allowed for smaller and lighter batteries of similar power ratings – typical 350 -500W (35 -50V at 10 amps). These newer lithium-ion batteries, which are also used in mobile phones and computer technology, have replaced the older, heavier, but cheaper rechargeable nicad battery. Powered by this new breed of battery a modern electric bicycle will have a range of 10 – 30 miles depending of the terrain and at a top speed of 10-20 mph.

Hub Motors:

Hub Motors There is nothing fancy about the motor technology used in most electric bicycles as they are standard DC brushless motors. These motors are built into the hub of the rear or front wheel, the center of the wheel where all the spokes meet. By sending power to the motors the brushes inside the motor are energized in sequence which makes a permanent magnet attached to the wheel spin around and the bike to move. Whether to place the motor on the front or rear wheel depends on what sort of experience you wish the rider to have. Motorizing the front wheel will effectively pull the rider along which can feel strange to begin with. On the other hand motorizing the rear wheel pushes the rider along, which is a much more natural feeling as this is how a traditional bicycle works. An alternative is to place the motor at the crankshaft and this has the effect of spinning the large gear wheel where the pedal cranks attach assisting the rider with the peddling.

The Frame:

The Frame The design of the frame must also differ from a traditional bicycle as it needs to accommodate the battery but also be extremely lightweight. This is simply because just like with the older designs and batteries we don’t want to be using up precious power moving the bike itself. After-all the goal is to propel the rider sitting on the bike so the lighter we can make the bike the further it can travel before you need to recharge the batteries. To get the strongest and lightest weight for the frame the material most designs tend to use is lightweight aluminum alloy. This material provides a sturdy and lightweight frame commonly used for those same properties and well proven in racing bicycles.

Wheels and Brakes:

Wheels and Brakes The wheels used in electric cycles are not the same as a standard wheel used in a tradition bicycle. This is because if you are powering the wheel using a motorized hub the spokes will need to be stronger to prevent them buckling under the higher torque – the turning force -supplied by the motor. To support this higher drive torque requires that the wheel – whether the front or back – being motorized will need special reinforced spokes and a different configuration, i.E. Bigger, thicker, and fewer spokes. The brakes also differ from a standard bicycle as they too have to deal with not only the additional torque from the motor but also the higher speeds. Some electric bicycles claimed to use a technique called regenerative braking which is highly effective in electric trains and cars. The principle behind regenerative braking is that starting say an electric car for example requires a huge amount of energy to overcome inertia and get the vehicle moving however that energy is then wasted when you have to brake as it is dissipated as heat through the brake pads. The idea is that it would be good if we could store that energy rather than waste it so we could reuse it later and that is the concept of the regenerative brake. The way it works is that all the kinetic energy that would have been wasted as heat loss through the brake pads can now be used to recharge the battery. In addition during periods of downhill travel when the wheels are rotating faster that the motor this additional kinetic energy can also be harvested to recharge the battery. This is a solid and proven technology in electric trains and cars but it unfortunately seems to be less effective in electric bicycles as they have far less mass and so far less energy loss when braking.

Different Types of Electric Bicycles:

Different Types of Electric Bicycles As we have already seen there are three basic configurations determined by where the motor is placed so we could have the powered hub on the front or back wheel or driving the crank-wheel. However there are also different types of electric bicycles which are determined by the method of propulsion. For example there are two basic categories; 1) full power, 2) power assist.

Full Power:

Full Power Bikes that are designed for full-power mode of use are designed to have large batteries driving powerful large motors that provide the torque to the drive wheel. The design purpose is to provide all the force required to drive the wheels so that you don’t need to pedal at all. As a result they have lower range 10-30 miles as the battery needs to provide all the power and top speeds of around 20 mph. This is a common type of electric bicycle as it requires no effort on the part of the rider and that is often why people go to the effort and expense of buying an electric bicycle. However there is another type of electric bike where the rider does contribute to the effort.

Power Assist:

Power Assist The idea behind this mode is that the rider will do the pedaling as they do on a traditional bike but can call upon assistance when they get tired or are struggling up a hill. This type of electric bicycle is quite different from the standard full-power version we have discussed so far. Power assisted bicycles do not have hub motors fixed to the wheels instead they have a different type of motor that sits beside and drives the rear gear sprocket or in some cases it drives a fly-wheel that rubs against the tyre providing the additional propulsion. The difference is that this type of electric motor has very low resistance to being spun without any power applied for example when pedaled. This is unlike a full power hub motor that is near impossible to turn manually without any applied power as you are effectively changing it from a motor into a generator. This means that as you are only applying power as needed to assist your efforts the range increases dramatically to around 50 -100 miles dependent on use. Also because they do not use fixed motor hubs there are kits available that can convert a traditional bicycle in a power assisted electric bicycle. Typically a basic conversion kit comprises of a bolt-on DC electric motor which goes just above the back wheel, which presses against the tyre driving it forward by friction alone. The motor gets its power from a compact battery that clips onto the frame. This kit may add quite bit of weight to the bike as the motor is around 3kg and the battery maybe as much as 6kg, but it does give you extra range and speed when required.

Slide 13:

Full powered or power assisted are the two general categories of electric bicycles but things begin to get more complicated when we up the power as they then may fall into the electric motorcycle category and this is where we have to consider the legal status of what is and isn’t an electric bicycle.

Legal Status:

Legal Status The legal status of what determines an electric bicycle varies from country to country so you need to check your own local laws. In general electric bicycles that are power assisted are termed pedelecs making them distinct from the more powerful electric mopeds and motorcycles. Because of this pedelecs are treated just like bicycles and do not come under the more stringent laws aimed at electric motorcycles. However full-power electric bicycles with large motors for example 500W with a throttle control may well be considered under local laws to be an electric, moped or electric motorcycle. If in doubt you might want to consider an electric scooter instead.

Electric Scooters:

Electric Scooters These electric powered scooters are just like the traditional push along version but they take out all the leg work and effort. Importantly, as they are compact and highly manoeuvrable they can be used on pavements or walkways which might be a benefit is you are nervous cycling in fast moving traffic. However they also are lower powered and have lower top speeds – although some do still managed 20 mph – so often have less local restrictions on their legal use.

Slide 16:

Whatever you decide to go for whether it is a full powered or power assisted bicycle or an electric scooter you will want to buy a good brand from a reputable dealer. Although electric bicycles are low maintenance as they have a DC electric motor and a solid state battery to worry about having a local support and servicing center in your locality is advisable as you don’t want to be shipping the bike or scooter back for warranty repairs. For example in canada there is a company called epic cycles that have an online ecommerce website where you can buy and have shipped free of charge a wide range of electric bicycles, electric scooters and accessories. But importantly they have also a wide dealer network with support and service options available. However, if you are a more DIY type of person they also have extensive FAQ and support service advice on how to perform all the maintenance tasks. This is an example of the type of extensive after sales support and services you should be looking for when buying an electric bicycle or scooter.

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