Converting my Dawes Sonoran to an E-Bike Part 4 - Battery, Controller, wiring and LCD Display

Now it's just a matter of fitting the battery, the controller, the display and connecting it all together.

It's a bottle battery so 2 screws and we're done - on the down tube rather than the seat tube. As I wrote in part 1, I sent back the original round bottle battery for the "upgraded" USB version. Although the USB port is of little use to me, this battery simply slots in and out where the "normal" version has a screw in plug which is significantly less useful. The upgraded battery is also 10Ah rather than 8Ah. 

The controller is another matter. The box fits neatly enough on the seat tube and the controller itself fits easily inside. However, Panda's wiring is generous in length so I tried to get as much of it inside the controller box as I could. This was a little fiddly and it then became difficult to hold it all in place before screwing the  two halves of the box together. The fit of the lid once it was crammed with controller and wires became a little less tight and I covered the seam with insulating tape - neat and hopefully weather proof.
  

The wiring from the battery to the controller does not have neat pugs but a pair of bullet connectors so I used heat-shrink tubing to protect the connection.  Unfortunately, Maplins colour code their heat-shrink by size so the most suitable tubing was bright blue - at some point I'll wrap that in insulating tape to neaten the job.

The other connections have (very) tight plugs but I've taped some of them as well - and combined with a selection of cable ties the overall installation is neat enough.

The LCD controller fits neatly on the handlebars and the rest of the wiring s just a matter of plugging it in.Unlike some, the LCD display can be configured to display in MPH and the instructions are not too "Chinglish" for an intelligent person to understand. 

I still need to find a neat solution to seal the ends of the three "spare wires" (thumb throttle and 2x brake cut-out) that you can see in the picture below.

Here's the complete installation - ready for the road. A quick test on a known and previously timed route of 6 and a half miles revealed that I was a full 5 minutes quicker than when I was 5 years younger, over a stone lighter and considerably fitter.

Converting my Dawes Sonoran to an E-Bike Part 3 - the Pedal Sensor

In order to know when to provide assistance, the motor needs a signal from the controller to tell it when to apply the power.

As an aside, thumb (or twist) throttles are also available although this is a subject all on it's own as legislation has recently changed. Pre-2016 UK E-Bikes would often have a thumb throttle but as I understand it, a hand throttle of any type is only now permitted as a "walk assist" when pushing the bike. In any event, I did not specify a hand throttle with my kit. 

To power up the motor therefore we need some form of pedal sensor. More expensive E-Bikes have a "Torque Sensor" which tells the controller to apply power proportional to the effort put in by the rider. This provides a very natural ride and almost feels like you have "bionic legs". This type of sensor is generally found on bikes with "crank drive" motors rather than hub motors although the Wisper 905 Torque, my preferred choice when I get round to buying a complete e-bike is a (rear) hub motored and torque sensed bike.

Having ridden bikes with this system I can absolutely say I prefer it - but it does require effort from the rider and is less suited to people who need to be able to use a bike but want the bike to do (almost) all of the work.

The alternative is the significantly cheaper (and less complex) rotation or cadence sensor. This simply triggers the motor via a magnetic sensor fitted at the crank.

Panda's sensors are "easy fit" and come in two parts that clip around the crank without the need to remove the crank arm. The sensor disc is secured by a metal ring and the complete disc is a simple friction fit around the crank. Time will tell if this is sufficient to stop it spinning freely. The sensor itself fits to the frame and has slots for cable ties as well as a sticky pad. This allows the location
to be tested before sticking it down firmly. There is a pivot which is adjustable to ensure the correct 1-3mm clearance between the sensor magnet and the sensor disc.

Converting my Dawes Sonoran to an E Bike Part 2 - more about torque arms

I mentioned the need for a torque arm in the last post. Here's a bit more info and pictures.

The "drop out" into which the axle/spindle of a bicycle wheel fits is simply an inverted "U".  If the nuts holding the wheel in place become loose, the wheel will simply fall out.  Clearly this is not a good thing. Although the weight of the bike will hold it in place when stationery (and theoretically the weight of the bike and rider will hold it in place while moving - but only if you cycle on billiard tables !)

With a hub motored wheel, a new dimension arises. On an unpowered bicycle, the wheel simply rotates around the axle. No rotational force is applied to the axle. With a hub motor, the axle must be held firmly as the wheel is powered around the fixed centre.

This applies a considerable amount of rotational force (torque) and increases the chances that the nuts could work loose. As a result we need to ensure that the fixed centre of the hub cannot rotate in the dropout.

This is achieved initially by the fact that rather than the axle being round, it is larger than on a conventional bicycle and the sides are flattened to fix the axle into the slot of the drop out - is essence, the axle fits the dropout slot like a spanner fits a nut. As a result, the torque from the motor can even open up the drop out making this problem even worse - especially if the nuts themselves work loose.

This brings us neatly to the torque arm. A plate, fitted to the flattened off axle with an arm which is either jubilee clipped to the fork (an aesthetically awful solution) or bolted to a mudguard stay mount. The ones supplied by Panda are made by www.torque-reaction.co.uk and are magnificent pieces of machined stainless steel.

I selected a "multi-angle" torque arm for my Dawes Sonoran s the standard "eyelet style" did not reach the mudguard stay mount. An additional issue for my bike is that the stay mount and fork are in the same plane so one or the other needed to be packed out with washers to allow for the thickness of the steel plate. The official fitting videos show the "arm" fitted behind the "eyelet" but this means that the axle has to be packed with washers and I felt that this was an inelegant solution as well as leaving insufficient thread for the nut.

The alternative, placing the "arm" in front of the "eyelet" is a far neater solution although it does mean packing out the smaller M5 bolt with washers - and any force applied in the event of a loosened main nut will be applied to this weaker bolt.


I'll be keeping a close eye on the security of all nuts and bolts.

Converting my Dawes Sonoran to an E-bike. Part 1

With the box of bits ready to go, and the bike indoors to make work easier through the winter I started the conversion.

The first thing was to take the opportunity to replace the tyres with a set of new Continental Town Ride Reflexes with reflective sidewalls (to go nicely with my Provis Reflect 360+ Jacket !) and at the same time fit new rim tape and tubes.

With its new tyre fitted, the replacement front motor wheel drops neatly into the dropouts. The axle is flattened to ensure it cannot rotate (so that the hub motor "drives" the wheel) and there is a "tabbed" washer to support this. It is important that this "tab" goes into the dropout last as the wheel does not sit neatly in the dropout if it is inserted first.

The torque from the rotation of the hub motor means that the axle can spin out of the drop outs - or even "spread" the dropouts over time especially with aluminium forks. On way to prevent this is with the fitting of a torque arm but the supplied version did not suit my forks so I will need to order a different version to suit my aging RST Forks.

I have also decided to replace the standard "bottle" battery for an upgraded version. As well as a slightly higher capacity,  this battery has the advantage of a "clip in" fitment where the standard version has a screw in connector. Panda e-Bikes have continued to be highly responsive to email queries and the new battery should be with me in the week to allow me to continue the conversion next weekend.

In the meantime, here's the hub motor wheel loosely installed in the front forks awaiting the arrival of the new torque arm.