Friday, 22 December 2017

Electric Bike

The Build

The goal of the Electric Bike Project was to provide a relatively inexpensive way to get to the ferry from where I live so I can get to the city for work. I live in a fairly hilly area and the idea was that the electric motor would handle the uphills (so I wouldn't be sweaty mess by the time I got to work) and I would handle the downhills. :)

The specification of the kit:
Model (year)RAKLO A-Kit (2016) FWD
DesignationStreet Legal
Main UseRecreation, commuting
Nominal Power250W
Cruise Speed25km/h
Max Speed25km/h assisted, further speed can be achieved from pedalling
Max Range50km
Average Range30km
Throttle TypeTwist Throttle with grips
Pedal Assist Levels3
Handlebar DisplayLED 880
Weight10kg total
Battery36V 8.8Ah Rack

The target bike, generously donated by Brendon, the mighty Norco Kokanee. The bike is a relatively inexpensive entry level mountain bike, with a few miles on the clock. In perfect working order, (give or take), the current gearing is 3x9, the front chainwheels are tiny.
…and the AKLO conversion kit. The kit is a rack style kit which suited me as I take a bag to work. You can see the wheel (no tyre or tube but does have rim tape), the rack which houses the battery and two boxes. The boxes contain the controller, the wires, some keys to lock the removable battery in the rack, the monitor, the charger and a bunch of other bits and pieces.

The only thing missing was the instructions... I couldn't find them anywhere on the net so I just got on with it.

Step 1: Put a tyre and tube on the rim.
Nothing too difficult there..

 

Step 2: Attach the wheel to the forks.
The axle was too large for the forks so I
had to file the drop outs back a fraction...

Step 3: The axle washers were also too
large so they had to be ground back too...

The wheel locked into the forks. For the professionals among you, you may notice the wheel is the wrong way around, creating a bike that only goes in reverse. What can I say, I had no instructions and on a 50:50, Murphy always wins.

I fixed that later.
Step 4: Put the rack together. This involved adding the extension legs to the rack frame to attach the rack to the bike just above the rear axle and to position the lugs that hold the rails that attach the rack to the seat post.

The lugs didn't sit flush in the channel which
meant the attachment bolt was too short.
So I ground the edges off the lugs.
Problem solved
This picture shows the lugs holding the bolt that holds the seat post rails. Seems unnecessarily complicated...
And finally the attachment to the seat post. I removed the seat post quick release and just used a standard bolt because with the addition of the rack rails the quick release was no longer long enough. The bolt is better security anyway.
Booyah, the rack is on.
Step 5: Attach the controller. The kit comes with a particularly flimsy bracket to hold the controller to the frame and the controller only has one tab for the attachment to the bracket. The bracket was supposed to attach to the down tube but I couldn't see a sturdy way to achieve that, particularly with everything else that is already crowding out the down tube.
So I created a small carriage that sits under the battery to hold the controller. Very sturdy, but I'm not sure how hot the controller gets under use. I may have to revisit this once the bike has been tested on the road.
Suddenly a huge wasp flew into the workshop. Probably to get out of the thunderstorm which brought hail. Work had to stop for a short time while the car was moved into the garage... Sadly, the wasp overstayed his welcome.
Another view of the rack and controller.

Step 6: Attach the cadence disc for the
electronic assist. That was no trouble....




...but the sensor wouldn't fit due to the
low lying derailleur. So I just left that
off. May revisit that with another chainwheel/derailleur, but that hardly
makes sense on this bike.
Step 7: Connect all the wiring. This was straightforward, all the wiring is colour coded and marked with arrows.

Step 8: Tidy up the cables..


... and the job is done. You can see the throttle attached on the right...
These are the leftovers. From left, the cadence disc sensor, the controller bracket(?), the handgrips, these didn't fit the handlebars, even though the handlebars are a standard small diameter. Note that the throttle wouldn't fit on large diameter handlebars. Finally, the brake sensors wires. These aren't really required if the cadence sensor is not on.

Assessment

The kit is relatively easy to install, although there are a number of minor issues that required adjustment, at least on the bike I used.

I'm a reasonably big bloke, (6'3" 85kg) but I have to say I was disappointed with the hill climbing power of the kit. On a fairly modest incline the bike struggled on it's own but when assisted with some pedal power, was more than happy to climb the hill. Under pedal power, it was noticeably easier to climb the hill with the throttle also on full. I expect the kit would need to be more powerful to achieve the hill climbing power I was hoping for, however that would probably cause the speed on the flat to significantly exceed the 25km/hr speed limit for bikes with these kits. That speed limit doesn't make much sense, 25km/hr is a reasonable, average speed for an unassisted, good rider, including uphills and downhills so the average human powered downhill speed would easily exceed the theoretical speed limit of an electric bike anyway.

I think I may have been overly optimistic regarding the power of these kits. They are fine under assistance but struggle on their own on fairly modest hills. It's great to move along without having to pedal, but ultimately, the kit didn't satisfy my requirement. I gotta get a bigger motor...

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