SmartMotion e20 Folding Electric Bike
Updated 26 May 2018
Désirée - electric bike distance = 6666 km. Total all bikes = 9600 km since mid March 2013
John - electric bike distance = 7266 km. Total all bikes = 12316 km since early January 2013
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We purchased two SmartMotion e20 electric folding bikes from Wellington Electric Bikes on the 14th of November 2014. This was the result of a long period of research using some of the links at right. The intention was to match our abilities on hills so we could do some more challenging rides together. These rides will be described in Dizzy's folding bike blog.
I first considered a conversion of our Giant Expressway 2 bikes but the cost was not too far away from that of new bikes. The sale of our old bikes would make up even more of the difference. I may return to a mid-drive conversion of my old Tarini Mountain bike in the near future. In the meantime I have completed several local routes which I previously found to be hard solo rides. Now we can do them together while still putting in a fair effort.
Some features of interest are shown in the photos. You can enlarge the photos by clicking on them. Use the back control < to return to the web page.
The bikes are similar to designs from Dahon or Tern except the wheel base has been lengthened. A detailed description can be found on the SmartMotion website. I weighed the bike at 24.5 kg which is similar to the weight of an average 7 to 8 year old child. Removing the 4.02 kg battery reduces the weight to that of a 6 year old child.
Many electric bikes are much the same weight, about 25 kg. If you find a lighter design this is because the battery capacity is less, the motor is low powered, the range is poor, the frame has an exotic design or materials, the tyres and wheels are lightweight or there are few added refinements such as mudguards, a carrier, a built-in lock, and lighting. Electric bikes need to be strong, which can also make them heavier. The forces on the frame and wheels are greater than normal. The extra weight on the rear wheel - battery, carrier and motor - is about 8 kg. This is less than the weight variation among a range of people, so there is not much to worry about.
A non electric Dutch style bike with a similar standard of equipment and accessories might weigh around 20 kg. For example the Gazelle Tour Populair weighs 22.6 kg.
The extended wheelbase now means I can use my old pannier bags without any heel contacts when pedalling.
Some weights are estimates.
The motor is a Japanese designed Dapu 36 volt, 300 watt unit. It weighs about 3 kg. The motor has the following codes placed in a hard to read location behind the cassette: Rated Voltage 36V Rated Power 300W 20 inch M155 CD3610 1LA 1312 A379. The motor is probably an OEM version of the Japanese designed Dapu M155 motor.
The maximum motor speed default setting is 30 km/h. Testing the bike on a nearly flat road, with a light following wind, achieved a maximum bike speed of about 28km/h. The controller keeps the maximum speed constant over a range of battery voltages. Hills, wind and weight also affect the maximum speed. So far on all my hill rides I have not detected any significant heating of the motor, so it must be reasonably efficient.
Electric Motor Properties
An electric motor can act as a generator. For a given voltage the motor will have a maximum speed where the generated voltage is nearly equal to the applied voltage. In this state little current is drawn and little power is available from the motor. The SmartMotion E20 has a maximum speed of about 35 km/h. The controller set maximum speed is 30 km/h. By loading the motor down to about 66% of the set maximum speed the power output is at a maximum. This is about 20 km/h in level 5.
Dapu M155 300 watt rear hub motor
By reducing the load so the motor runs at 75% of the set maximum speed the efficiency is maximised. This is about 23 km/h in level 5. At this speed most of the energy in the battery contributes to forward motion of the bike rather than heat. These speeds reduce in proportion at lower assist levels so at level 3 a speed of 15 km/h is economical. With a tail wind on the flat you may well go faster but the motor won't be helping much.
The table below is a rough guide to help with choosing assist levels for best performance. The numbers are at the lower end of a small range of suitable values. There is a power use bar on the top left of the display. It gets longer when the motor current increases. Keeping the length of this bar minimised will increase the range of the bike.
Power requirements for cycling
Cycling at 30 km/h, on the flat, under calm conditions on a normal upright bike, requires about 205 watts. A fit rider can supply this power, at least for a while.
If there is a 20 km/h headwind, the power required increases to about 480 watts. A normal cyclist will slow down under these conditions. The cyclist will need to provide an input power of 218 watts to maintain a speed of 20 km/h into a 20 km/h headwind.
If the slope increases to 5%, that is, a rise of 5 metres for every 100 metres of horizontal motion, the power requirement, at a speed of 20 km/h into a 20 km/h headwind, increases to 540 watts. The normal cyclist will slow down further, as this power cannot be provided.
At 10 km/h, on a 5% slope into a 20 km/h head wind, the cyclist will need to provide 230 watts of input to maintain that speed.
Under each scenario the cyclist will be fairly hot and sweaty at the destination. An electric bike can make these riding conditions much more enjoyable. A legal motor can provide up to 300 watts of assistance, which can make a long trip a pleasant experience for a less able rider. For physical fitness, the motor input can be dialled down so that it is only assisting on the more difficult riding sections. In this case the range will be greatly increased.
A cyclist climbing a hill, with a 12% slope, needs 240 watts of power input to go up it at just 6 km/h. With the aid of a 300 watt electric motor, and 100 watts of input from the cyclist, the speed up the same 12% hill would now be in excess of 10 km/h. At the destination the cyclist would be in a much better condition to socialise and to enjoy the view. Recently we joined two group rides, which included some steep Wellington hills. The electric cyclists on the trip each took almost the same time to climb the hills.
The bike has a 36 volt 15.6 amp hour lithium polymer battery. The battery can be removed from the carrier with a key. There is no start key, only a button on the back of the battery pack. Power is turned on in two steps: pressing the button at the back of the battery, and then turning the controller LCD display on. The LED bike lights run directly off the battery. There is also an included USB phone charging port.
It is possible to estimate the remaining battery capacity from the unloaded battery voltage.
The received engineering wisdom is that it is meaningless to measure the unloaded voltage to determine the remaining battery capacity. Most discharge-graphs in battery specification sheets relate to batteries under load. In this case the load is highly variable making a measurement of capacity, under the applied loads, meaningless. There is a reasonable and convenient relationship between unloaded voltage and capacity for lithium batteries.
A Lithium polymer battery with 100% remaining capacity reads about 41.7 volts unloaded. At 0% remaining capacity the unloaded reading is about 36 volts. A plot of unloaded voltage vs remaining capacity is linear up to about 40.5 volts or 85% remaining capacity. There is little added capacity from 41 volts to 41.7 volts.
When the motor load is applied to the battery at 36 volts the voltage may drop to around 31 volts. This should cause the controller to disconnect the battery to protect it from damage.
The graph below was derived from user experiences with lithium-polymer batteries in radio controlled aircraft, where unloaded measurements were made after the flight. The curve becomes seriously non-linear above 41 volts which indicates that, in addition to simple charging, other electrode reactions are occurring. There is a chemical reaction of the negative electrode with the electrolyte. Insulating reaction products are slowly deposited on the negative electrode surface, which reduces the available current and shortens the battery life. Electrolyte additives are used to limit this process. How to Make a Lithium Battery Last is a good scientific article and video on these processes.
Unloaded battery voltage vs remaining capacity
The battery chargers get warm in use, so I place them on an aluminium plate to help dissipate heat. The lifetime of electronics is usually shortened at higher temperatures. On carpet, I would suggest supporting the charger on two pens to provide some air circulation underneath.
The stored energy in the battery, in watt hours, is a most important specification as it determines, potentially, how far the bike can go. A way to compare bike ranges is to calculate the battery voltage times the battery amp hour capacity and divide the result by 10 watt hours per km. The result is a nominal range in kilometres.
For my bike the battery energy content is 36 volts x 15.6 amp hours = 562 watt hours. Dividing 562 watt hours by 10 watt hours per km = 56 km which is the range for an energy use of 10 watt hours per km. A 12 amp hour battery therefore has a range of 43 km. For our riding style, these distances are an underestimation.
We get a very long range at our riding speeds. One long ride, in Hawke's Bay, was 62 kilometres which still left us with a lot of battery capacity remaining. Some hill rides in the Picton and Nelson areas were a little longer.
I have no idea of the full range of these bikes. This depends on the individual riding styles, speed, terrain and wind velocity.
An interesting web based calculator estimates the power required to produce a given bike speed.
2 amp chargers are provided which, under normal use, can charge the battery to 41.7 volts. In my case I have designed a diode splitter cable which allows the two batteries to be charged to about 40.7 volts at a 1 amp rate. This lower voltage reduces the range slightly but can have a profound effect on the battery lifetime. Detrimental chemistry occurs at low and high voltages. In the middle range of voltages the battery lifetime is very long. One charger can top up two batteries overnight. The lower 1 amp charging rate is probably beneficial. Occasionally the splitter is removed to ensure the battery balancing circuits are properly activated. As long as the batteries are not fully discharged all cells should have the same voltage.
Wellington is known for its steep hills and strong winds. Typically, we ride around Wellington at 15 to 25 km/h on level 2 or 3 assist. Above 20 km/h no power is taken from the battery on level 3 assist. This extends the range.
On gentler hills, and into moderate head winds, 17 km/h is a common speed. On steep hills our speed may reduce to 10 km/h which is still reasonably efficient at these assist levels. I use the throttle occasionally to help at intersections and to start on hills.
Note that here I express the steepness or grade of a hill as a percentage defined as 100 times the tangent of the slope measured in degrees. The tangent is the vertical rise divided by the horizontal distance. An 8 degree slope is a 14% grade with a tangent of 0.14. A 7 degree slope is a 12% grade with a tangent of 0.12.
Our steepest local hill - a 14% grade
For serious hill climbing, it is better to reduce the assist setting to 2 or 3, change down the bike gearing and to go uphill more slowly. This is counter-intuitive, but it is more efficient, producing much less wasted heat in the motor, controller and battery. Pedalling in a suitable low gear will help to maintain the optimum speed. Going too fast or too slow uphill is inefficient.
Using lower assist settings on hills shifts the motor's maximum-efficiency speed downwards. This means that the motor and controller won't overheat when under load. The tradeoff is that less power is available, so some extra pedalling effort is needed.
You can roughly calculate that the optimum speed on hills at level 3 should be 0.75 x 20 = 15 km/h for efficiency and 0.66 x 20 = 13 km/h for maximum power. There is a wide tolerance on these figures so a speed several km/h slower is still efficient.
The battery current is displayed at the top left of the display as a series of bars. Keeping the displayed bar length short greatly improves the range.
Waverton Terrace, Churton Park, Wellington - a 12% grade
In Wellington I have ridden the Johnsonville - Makara Village - Karori - Johnsonville loop several times without any problems. I also rode this loop on my unpowered Jamis Allegro bike, with a bit more effort.
Another good ride was from home, in Churton Park, to Wadestown. I walked the bike up the extremely steep Weld Street, using the 6 km/h walking-assist function. This was followed by an easier ride over the top of Tinakori Hill to Northland.
I turned down the narrow Orangi Kaupapa Road to Garden Road, Glenmore Street, Tinakori Road, Hutt Road and finally up the Ngauranga Gorge back home. This was a pleasant ride with some work required on the steeper bits.
Although I was tempted to ride up the 18% grade of Weld street I felt it would stress the bike, and me.
Tinakori Hill - Wellington
Listening to the motor helps to run the bike more efficiently. The motor makes more noise when it is running slow, under load. In this state the motor is wasting a lot of battery power as heat.
Controller design and programming helps to get the best performance out of the motor. The controller pulses the motor on and off at a high frequency to enable the motor to run slower at 36 volts. Depending on the duty cycle of the pulses this is an efficient way to reduce the net voltage and speed. The reduced speeds are achieved with little wasted heat in the controller or the motor. In addition a programmed initial acceleration increases the motor efficiency during start up.
A disk, located behind the chainwheel, contains 5 cubic pedelec magnets. It rotates with the chainwheel. The magnets pass a single Hall sensor which sends a signal to the controller to start the motor. The magnets are orientated sideways which means that the motor will not start when back-pedalling.
When pedalling forwards the magnetic poles, N = North, S = South, pass the sensor as NS......NS......NS......NS......NS. Pedalling backwards produces SN......SN......SN......SN.......SN. The controller is programmed to tell the difference so the motor assist is only produced if the pedalling direction is forward. The magnet polarities can be measured with a small compass.
The blunt south end of a simple compass needle points to the south magnetic pole of the earth. The Earth's south magnetic pole is actually the north pole of the Earth's natural magnetic field.
The sharp north pole of the compass needle points to the Earth's north magnetic pole. The Earth's north magnetic pole is the south pole of the Earth's natural magnetic field.
The north pole of a magnet is the one which tends to point north. This can be somewhat confusing. If a compass encounters the north pole of a magnet the south pole of the compass needle will point towards it.
There are other pedelec systems with two hall sensors. In this case the magnets have their poles facing outwards. The magnetic disks from one system will not run on the other.
There are 10 holes in the SmartMotion Pedelec disk and only 5 are filled with a magnet. At present it takes 3/4 of a crank revolution before the motor starts. With 10 magnets it will take only 3/8 of a crank revolution before the motor starts.
Reducing the motor start-up delay should make the bike more natural and responsive to ride. The motor and controller is capable of an instant start using the throttle, so a delayed start of 3/8 of a crank revolution should do no harm.
The magnets play no role in measuring the bike speed so the display contents should be the same as before. The speed of the bike should also be the same. There may be some additional control issues when stationary but the brake cutout switches should manage that.
10 Magnet Pedelec Disk Upgrade
I was kindly given a spare pedelec disk by Cliff Randall at Wellington Electric Bikes. I was able to press the magnets out of this disk using a wooden chopstick. I pressed the 5 magnets into the disk from my bike, after using a compass to test the correct orientation of the magnets. The poles lie sideways with the north pole arriving at the sensor first. The north pole of a magnet attracts the south pole of a compass needle. A small screwdriver can be used to test that the magnets are indeed lying sideways. It will only be attracted to the leading and trailing edges of the magnet and not the middle,
First, I had to remove the disk from my bike by removing the chain-wheel. I used some BluTac to immobilise a single magnet on a desktop in the correct orientation. I then pressed the disk over the immobilised magnet. I used a soft-faced instrument vice to complete the pressing operation. The magnets are brittle so the pressure should be even.
Some plastic may be expelled from the hole during the pressing operation. Remove this with a knife and repeat the pressing operation. If the magnets are loose in the holes, use some superglue to secure them. Wipe off the excess glue immediately using a cloth dampened with methylated spirits.
The magnets are attracted to nearby steel items and to the other magnets, which can be a little frustrating. A simpler method might be to place one disk over the other and then to press or tap the magnets through from one disk to the other.
The magnets facing the sensor should be flush with the disc otherwise they may catch on the sensor. If teeth are missing from the middle of the disk the likely cause is projecting magnets. The disk can be set in place on the bottom hub shaft by using a temporary paper or thin plastic shim to ensure the disk does not touch the sensor or wobble. Nail polish can be used to set the disk in place on the shaft.
4 mm cubic N35 magnets are available on Ebay.
After about 1000 km of testing, the new Pedelec disk performs exactly as expected. The bike is now much more responsive. The motor now starts helping after the cranks have rotated just 3/8 of a turn. The bike feels safer when getting underway at intersections. This is probably easier on the motor and controller than relying on the throttle for that purpose.
The motor start-up acceleration rate depends on the speed at which pedelec magnets pass the sensor. This means that pedalling fast in a low gear will produce an increased motor acceleration rate. The new 10 magnet pedelec disc doubles that acceleration rate.
The latest model of this bike has a different type of sensor/magnet arrangement built as a single component.
The LCD display is a Bigstone BST-C30036 unit. It shows power use levels, speed, power assist settings, remaining battery capacity, error codes and distance statistics. The controls are close to hand when riding. The maximum speed reading is reset when the display is turned off.
The throttle and display are conveniently placed on the left side of the handlebar. The throttle overrides any assist settings. The assist settings go from 1 to 5 in order of increasing available power output from the motor. The maximum speeds, with assistance, are approximately 12, 16, 20, 25 and 30 km/h respectively.
The remaining battery capacity bar display shows:
There is a tolerance of +/- 0.3 volts on these readings. A 3 bar reading with the motor stopped indicates that there is little remaining battery range. This will be confirmed as soon as the motor is started, as the the display may now show only 1 or 2 bars. The battery display will flash at lower voltages.
During a ride 6 bars may be shown on the LCD display for quite a while. The freshly charged battery starts at about 41 volts and the voltage must fall below 38.5 volts before 5 bars are seen.
As we gain more experience riding the bikes, the more we adjust to them and any minor control issues reduce in importance. We simply enjoy the ride.
Wellington from Mount Victoria
The Velo-Plush saddle is large, comfortable and is mounted on a suspension seat-post. For me this is somewhat unnecessary given the saddle is soft and the tyres are wide. The seat-post is painted black but it marks easily, exposing the bright aluminium underneath. I have since removed the paint, with the added benefit of improved clamping. The saddle weighs 605 g and the seat-post weighs 609 g. I may replace it with a lighter saddle and an anodised aluminium seat-post which should halve the total weight and feel similar to my other bikes. The current seat-post is 30.3 mm in diameter and 400 mm long, so any replacement should be of a similar size and length.
The bike has a very nice built-in Dutch style frame lock which, for extra security, can be used with a separate end-looped cable to secure the bike to an object. It weighs 407 g. It is unbranded, but it looks to be similar in style to an AXA Defender RL frame/wheel lock.
The key does not have to stay in when it is unlocked, which means it can remain on a key-ring.
The stem and frame clamps use a simple over-centre design which is easily adjustable. Safety locks are provided.
The chainwheel has 52 teeth and it has twin aluminium chain guards which protect trousers and also prevents any chain drops over rough ground.
In the rear there is a Shimano HG41, 8 speed, 11-34 tooth cassette and a Shimano Altus derailleur. This is gives a range of 30.7 to 94.9 gear-inches, 2.45 to 7.57 metres-development and a gain-ratio from 2.29 to 7.09. These terms are defined here.
The wheels have 36 stainless steel 13 gauge (2.3mm) spokes which are thicker and therefore stronger than usual. The Alex 303 aluminium rims are also quite substantial.
The front wheel, plus the tyre, weighs about 1.8 kg. The rear wheel should have a similar weight, not including the motor weight, the cassette and free-wheel mechanism at 4 to 5 kg.
The Kenda tyres are marked as 20 x 1.96 inches and 406 x 50 mm in size which is wide and comfortable for a folding bike. The actual diameter when inflated on the wheel is about 510 mm. I do not understand tyre markings, which only roughly approximate the actual sizes. Here "406" refers to the rim size, which only adds to the confusion. I have seen 20 inch tyres which range from 18 to 21 inches in diameter A kevlar band inside helps to protect the tyre from punctures. The pressure range is 40 to 66 psi or 2.8 to 4.5 bar.
The correct tyre pressure depends on the load it carries. Tyre drop is how far the wheel moves towards the road when it is loaded. It is expressed as a percentage of the tyre width.
A common figure for an ideal tyre drop is 15%. This may require lower pressures than normal, but the bike will be no slower, or difficult to handle. A useful reprint on this subject is here.
In order to allow some time between checking tyres I have adopted a 10% figure. For my 50 mm wide tyres this corresponds to a tyre drop of about 5 mm when loaded, by sitting on the bike. For me the approximate corresponding pressures are:
These pressures should allow riders with a range of different weights to have a comfortable ride. To get these values I had to sit on the stationary bike while using a vernier calliper to measure the wheel rim drop. This was easier than it sounds.
Potholes and Wheel Size
It is often claimed that smaller wheels are much worse on bumpy roads. In fact, the response of different wheel sizes is fairly similar. With a 510 mm diameter wheel a 230 mm diameter pothole, when bridged, will cause a 25 mm drop of the wheel. With a 660 mm diameter wheel the drop is 23.5 mm, which is 1.5 mm less. With a 690 mm diameter wheel the drop is 21.6 mm, which is 3.4 mm less. This is experimental data. These differences may be greater for larger potholes, but the tyre will now likely roll across the bottom, still producing a similar response. The tyre width, tyre pressure, balance and the sudden diversion of the steering is more important. On any bike a pothole can cause trouble.
The Tektro brake levers and Shimano gear shift levers are shown at right. There is a Hall sensor located on the underside of each brake lever which cuts power to the motor when a brake is applied. The left-hand brake lever has a very nice built-in bell. A specified 180 mm disk brake is not fitted to the front wheel. V brakes are perfectly fine, and lighter, for this class of bike.
A CatEye bar-end mirror was fitted to each bike. This addition is probably the most important as it contributes to safety. You can see the line that traffic is taking behind you, whether any indicators are flashing, and the approach of other cyclists. I have used a bar-end mirror on my mountain bike since the late 1980s. When riding on busy roads it helped me assess the space that wide vehicles, such as trucks, would leave me. I filed some plastic off the inside of the end-cap so the mirror tilted out further. This prevented it being knocked by my hand, during rides.If you are a motorist, motorcyclist or an inexperienced cyclist, a mirror will be a great aid to safety. It also assists with improving my balance issues. When choosing a mirror, make sure that the field of view is sufficiently wide, so the mirror position does not need frequent adjustment.
I have added a Phillips handlebar bag to each bike. It is a versatile removable bag which still allows the bike to fold properly. We used this bag, along with a carry-all sports bag on the carrier, for light touring in the Nelson area.
There is a single bolt underneath the saddle which, when loosened, allows the saddle to be tilted and slid forwards and backwards. The saddle should usually be level and the horizontal adjustment should be in the middle of the range as a starting point. Small adjustments to the saddle height, tilt and horizontal position can be made in small increments over a periond of time until a comfortable setting is obtained. When the bolt is tightened wiggle the saddle and tighten again. This ensures everything has slipped into position and is firm. This is a good reference - Sheldon Brown - Saddle Adjustment.
I found a minor problem with the kick-stand. When closed, the stand foot touched the rotating motor body which produced a ringing sound. Some paint was also scraped off the motor. The cure was to shorten the lower leg, by adjustment, or to add a shim under the frame mounting point. The shim would also cure the small clearance of the upper part of the leg from the tyre. Another option is to change the kick-stand brand.
I ended up shimming the mounting plate at the back with a 40 mm length of an old 14 gauge spoke. This allowed an increased motor clearance of 10 mm and a longer leg adjustment for a more upright stance of the bike, when parked. The parked bike was much more stable when loaded for touring.
The downside of most kick stands is that nearly level ground is needed for stability, particularly when the rear carrier is loaded. Leaning the bike against an object is another option. A rear mounted kickstand, attached near the rear wheel hub, might be better.
I had to adjust the front mudguard upwards on my bike as it was lightly touching the tyre. I also had to add an extra washer to the bolt holding the right-rear mudguard stay onto the drop-out. The bolt was just slightly too long. On Désirée's bike the chain occasionally touched the end of this bolt producing a clicking sound.
On odd occasions we have both nearly lost control of the bike while standing and inadvertently moving the throttle. As the bike moves forward the throttle setting naturally increases. The held bike then rears up, reducing the throttle setting only slightly. A tilt switch might help to prevent a total loss of control. Reactivation would then require the throttle to be returned to its zero setting. Using either brake lever will instantly stop the motor.
The walking-assist function was very helpful, but the "+" button was difficult to keep reliably pressed for a long time. The pressure required is too high, particularly for people with painful joints. A better tactile switch is needed for this function. Alternatively the walking-assist function could be reprogrammed.
Using Walking Assist
Holding down the "+" button for two seconds would engage the 6 km/h setting. The throttle would be used as a 6 km/h start and stop control. Touching the "+" button again would return the bike to normal operation. Normal operation should also be restored with a timeout function, or a link to the pedelec system. This would ensure safety at intersections, where the throttle may be required for a fast start.
A permanent 6 km/h walking assist option in the setup could allow the throttle to activate just this feature.
Eventually some items will wear out. The most likely items are the tyres, chain, rear cassette, brake cables, derailleur cable and brake pads. Some bearings may need adjustment or replacement.
The rims will eventually wear out from braking. There are wear marks engraved into the rims. These should always be visible.
Note that with a mid-drive bike the chain and sprocket wear can be higher if the tasks demanded from the bike are harder than previously. Extreme hill climbing comes to mind.
With a hub drive the wear may be lower because some of the motive force is directly applied by the motor to the wheel. The personal input via the chain and sprockets can therefore be somewhat lower.
It is interesting that with our drivetrain we are only just considering chain replacements at nearly 3000 km of service. A measurement with a chain gauge showed that the wear rate is low.
The life of a chain is maximised if it is lightly oiled with a low viscosity oil, similar to sewing machine oil or automatic transmission oil for cars. First the chain should be wiped clean with a few rags or paper towels. Use a few drops of oil on the rag to help remove any black wear deposits. Try to clean the cassette, deraileur idlers and the chain wheel as well. An old dish brush is good for this. Oil the chain by rotating the chainwheel backwards and letting the oil drop onto the lower inside part of the chain. Oil the deraileur idler bearings as well. After a delay, to let the oil penetrate, wipe as much oil as possible off using a clean rag. The idea is to have sufficient oil inside the chain, where it is needed, but almost none on the outside where it can attract abrasive dust. Dispose of any oily rags to prevent future fires.
The longer chain life compared with our other bikes is due to the rear hub motor reducing the chain loading, especially on hills.
The wear rate can be high if the chain isn't clean. In an abrasive environment when the chain load is doubled the wear rate can increase by as much as 8 times. Under clean conditions the wear rate is usually proportional to the loading. This is why mountain bikes need so much maintenance when ridden hard, especially under dirty conditions.
The spokes may need re-tensioning as the wheels settle with use. Most 20 inch rims are quite accurately made so all the front wheel spokes should produce a similar tone when tapped. The rear wheel spokes should produce two tones depending on which side of the wheel the spoke is on. The cassette side should produce the highest tone.
As a group, the tones on a particular side should be the similar. The odd sounding spokes should be adjusted to sound the same as the others. A minor amount of additional trimming should then produce a true wheel.
My front wheel has an average spoke frequency or pitch of 600 Hz (just under a D sharp). The rear wheel average pitch is 1000 Hz (just above a B) on the cassette side and 800 Hz (just under a G sharp) on the other. These notes are found, on the piano, in the octave above middle C.
The higher pitch, or tension, on the rear wheel is because it carries a higher load than the front wheel. If the rim is not inherently true then the tones will differ as extra tension will be needed on some spokes to apply corrections. More information can be found here.
The spokes are 13 gauge so a 3.7 mm spoke-wrench is needed. Professionals measure spoke tension instead of tone.
Specific Folding Bike Adjustments.
Some items specific to the folding mechanism may need attention.
Hinge Clamp Adjustment
When a hinge clamp is closed it applies a force onto the head of an adjustable bolt. This transmits a compressive force to the hinge which prevents it from moving. An Allan key can be used to adjust this bolt. The steerer clamp is shown at right
The clamp moves through a 90 degree arc. A resisting force should be felt when the clamp is within about 20 degrees of closing. The tip of the clamp then has about 30 mm further to move before it is fully closed.
The clamps have plastic safety latches which should be rotated into place.
The steerer hinge uses a pin, like in an ordinary door hinge, which is kept in place with a set-screw. This set-screw should be reasonably tight and checked periodically. Some Loctite 243 can be applied to the thread of the tightened set-screw to ensure that it does not drift outwards, releasing the pin. This might happen on long car trips where the bike is folded and the hinges are free of any tension. The clamp pin is retained in place by a Circlip.
The frame hinge has two pins, one for the clamp and one for the hinge itself. They are each retained with a set-screw. The set-screws should be tightened and held in place with Loctite 243.
When the bikes are ridden, there is an oscillating force present at the base of the set-screws which might cause them to loosen. This needs to be prevented. The set-screw for the frame hinge fits below the hinge pin, so it would have to loosen a lot for the hinge pin to be released. The remaining two pins have their sides recessed to accommodate a set-screw. This means that a set-screw needs to rotate several turns anticlockwise before a pin is released.
In aircraft engineering, screws were often retained by lock-wires. The wires were threaded through a hole in the head of a screw and through similar holes in adjacent screws. Often the wires were twisted in pairs with a specific threading pattern between screws. One wire would go through a hole in the screw head while the other wire would run over the top. Here, Loctite 243 is almost as good.
Steerer and frame set-screws
To Kaiteriteri 11 - 18 March 2015
We completed a March 2015 trip from Wellington to Kaiteriteri at the top of the South Island. This involved cycling to Johnsonville early on a dark morning using our built-in lighting system.
A commuter train took us into Wellington where we caught the Bluebridge Ferry to Picton. We rode from there to Pelorus Bridge via Queen Charlotte Drive and Havelock.
On our second day we rode over the Rai Saddle and the Whangamoa Saddle to Nelson.
On the third day we rode to Mapua via Rabbit Island and the Mapua Ferry.
On the fourth day we rode on to Motueka and did a 20 km battery-less return ride along the estuary and waterfront.
Our ride to Kaiteriteri and back the next day was scenic and interesting. We rode the road and trail route towards Kaiteriteri and the Mountain bike trail on the return.
The return to Wellington ride was from Motueka, Mapua to Nelson. From Nelson we folded our bikes into our Giant Expressway bike bags and presented them as luggage for a bus trip to Picton. We rode the bikes around Picton and Waikawa Bay because the Ferry was delayed. During this ride my display showed that I had ridden 1000 km since purchasing my electric bike.
In Wellington we waited for 30 minutes, caught the train to Johnsonville and then rode home in the dark. In total we rode about 340 km over some substantial hills and unsealed trails.
Cyclone weather - Mapua Wharf
We had few problems with the bikes. A pedal loosened on Désirée's bike and started to lock up. This was a ball bearing failure which can be easily fixed at home. We purchased some lightweight 150 g replacement pedals, which worked well. The old pedals weighed 240 g each. They seem to have quality issues as well, since all four pedal shafts were slightly bent, which probably contributed to the bearing failure.
A rough indentation test showed that the folding pedal shaft hardness was about a quarter that of a more expensive plain pedal shaft. Using my X-ray spectrometer I found that the pedal shafts were made from a tempered chrome-manganese steel. This is iron with a fraction of a percent of chromium and manganese added to increase strength. The differences in hardness reflects the care taken in the thermal tempering process. I have since replaced all the pedals as we rarely folded them.
Metal hardness needs to be specified for a particular application. Too low hardness may cause items to loosen or bend while too high hardness can cause them to break. Even bolts and washers need to be correctly hardened. It is common to see washers seriously deformed by the simple act of tightening a bolt. Pedal anti-rotation washers are a good example. They tend to perform well, only once.
The bike kickstands need careful adjustment if the bike is carrying luggage. With our loaded bikes we had to be careful about bike stability and the optimum length of the strut. Our luggage was about 6 kg in the rear bag and 3kg in the front bag, including the bag weights. I had the same kickstand problem with my old Tarini mountain bike when I did some touring around Nelson and Takaka. With care, the problem is not too serious. Using a stand designed to be mounted closer to the rear axle may help.
I recently had a problem with one of our batteries. I keep a check of the battery voltages with a small digital multimeter. This is to make sure that the charge and discharge voltages are OK and within a safe range, and that the chargers are not doing anything unsafe. To do this I have a special adaptor so I can plug the meter into the charging port. Unfortunately the adaptor plug developed a minor short which produce a brief arc inside the plug. The plug and wiring was undamaged. The net result was that I was no longer able to charge the battery because of some electronic failure inside. Everything else was OK. The battery management board inside the battery may need to be reset or replaced.
I now have a replacement battery. Thank you Daryl.
The bikes were able to cope with hilly rides in excess of 60 km with around half of the displayed battery capacity remaining in each case. I suspect the remaining capacity of the battery would be depleted faster than the first half, since the voltage is lower and the demand on the battery increases to compensate. Note that the range obtained depends on the rider input. I have still not been able to flatten my battery within one day's riding.
Back in Wellington, on a weekend ride, we did a fast 7 km ride in cold and driving rain without any problems. We were caught out, so we made a 30 km/h, level 5, dash to get to our car.
I have now completed more than 2091 km. Désirée has ridden over 1859 km. For the first time, I have adjusted the derailleur cable, on my bike, half a turn anti-clockwise for smoother gear changing. The brake pads are still fine. The chain is not worn. The battery capacity is still very good. The motor sounds the same. The tyres have plenty of tread left. Our tyres remain unpunctured in nearly 4000 km of riding. There are still no issues with either bike.
Our longest ride so far was from Paeroa to Thames and return - a total distance of 72 km on gravel, on a cold day and in a moderate cross wind. There were some detours for food. The indicated battery capacity was a bit below half at the end of the ride. Mostly we used level 3 but we did use level 4 for the last few km. Obviously we did a fair amount of pedalling as well.
Rest stop, Paeroa - Thames - Paeroa
My bike has reached 3135 km with no major issues. I did change the chain recently as there was some minor wear. An early $20 replacement can extend the life of the rear cassette. The battery is still fine with a good range. The 10 magnet pedelec disk is working well and makes the bike much smoother to ride. The electric motor now assists just at the right time. Both our bikes now have this upgrade fitted.
We did a recent ride near Masterton of 72 km. The ride was a loop through rolling countryside via Gladstone with only one wrong turn included. We arrived back with 4 to 5 bars out of 6 left on the display. Again, we had put some effort into our riding so the motors assisted mostly on hills and into the wind.
My bike distance is now 4014 km, again with no major issues. The battery is still producing a good range, in excess of 70km.
We still have not had any punctures and there is plenty of tread left on the tyres. The brake blocks are original, which is surprising since we often ride on steep hills. Both bikes still ride silently. I do a chain clean and lubrication, every few weeks and I also check the frame, wheels, bearings and various other components.
Nothing to report. No punctures, but plenty of off road riding. The brake blocks are still fine. A recent ride was 52 kilometers with plenty of battery range left. Basic maintenance is keeping the tyres at a suitable pressure and lightly oiling the chain and deraileur. Excess oil is always wiped off to discourage dust accumulation. The chain is checked for wear and the brake cables are checked for any strand breakages.
Still little to report. No punctures, with plenty of off road riding. I have done several rides longer than 50 kilometers still with plenty of battery range left. The brake blocks are original and in good condition. The brake adjustments have been minor. I adjusted the headset to remove some very slight play. I resoldered an electrical lug on the front light which was intermittent. Routine maintenance, described above, was carried out. I may fit new locking hand grips soon as the old ones rotate a bit with use.
LCD display error at 6553.9 km
I have noticed that my LCD display resets to 6553.9 km when powered up. It can advance normally beyond this point during a ride, but it always resets to 6553.9 km when powered up again. I am waiting for Désirée to reach the same distance so I can determine if this a general programming error, or just with my display. So sadly, I may never reach 10000 km on the e20. Note that 65536 is the binary number 216 which may be the source of the error. The programmer got the last digit right but the remaining digits only got to binary 1's - i.e 6533.9. Also the trip counter now zeros to 44.7 km after power on which is harder to explain. Holding UP, DOWN And SET resets the display, so I can now start again.
On a ride in Paekakariki I experienced a slow puncture in my rear tyre, at the end of the ride. At home I extracted a 2 mm glass fragment, which had gradually worked its way through to penetrate the tube. This fragment is likely to be from a larger shard of glass which has broken and worn down as the tyre rotated. The remaining fragment irritated the tube over some time, until a slow leak occurred. The repair involved removing one side of the tyre from the rim using tyre levers, extracting the tube and patching it. I removed the glass fragment from the tyre by pushing it outwards, from the inside, with a sharp probe. The rear wheel did not need to be removed but the brake cable was released to make room.
2 mm Glass Fragment
No major issues to report. I repaired another slow leak in the rear tyre from a glass fragment.
As with the Giant Expressway 2 folding bikes, we will gradually customise these bikes to our needs. We hope to do a range of interesting new rides. On several recent rides we found that we could keep pace with each other on hills and in strong head-winds. This makes for much more sociable riding, and more opportunities for riding.
My advice when choosing an electric bike is to keep things simple. The electric motor can compliment a basic gearing system such as a 3 speed hub. The best test of an electric bike is to first ride it unpowered. Then ride it on terrains similar to your intended routes. Find a good local bike shop.
Our bikes are accepted on local trains, usually in an unfolded state. On busy trains or buses they may need to be folded. I may also use a bike bag.
I have added some links under the heading "Innovation" as folding, or lightweight, bikes, lightweight motors and low cost, 36 volt, power tool batteries may be used in the future for assisted bike riding. The ideal electric bike has yet to be designed.
Cyclone weather - Ruby Bay
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After a steep hill climb
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