Electric bikes – First Ride

I have been a bit slow blogging about these bikes, mainly due to the frustrating build, but last night I got my first ride on my electric bike under its own power! It’s not a perfect build yet, but it is mobile.

After the success with the batteries I started piecing together the puzzle, and finding the problems. My existing wheels have 7 speed Shimano gearsets on, and I ordered what I thought were identical gear sets to put on the new wheels, 7 speed cassette type gears. Unfortunately when they came they were 7 speed screw on cassettes, not the sort that uses splines! Not to worry, they were only $10 each. So, off came the gears from the original wheels, and slid them onto the new wheels, but the wheels are for 8 or 9 speed gears not 7. It felt like the end of the world at the time, but a bit of research on the net, and I found that all you need are 4.5mm spacers between the gears and the hubs for everything to be sweet again. I managed to find some spacers that will work temporarily for one set, and a local bicycle mechanic put some on the second wheel.

I put the wheels into the frames, and rather stupidly decided that the thick washers with “torque tabs” on went outside the frames not inside, so the wheels did not sit central, and I thought that the wheels had been badly built with the wrong amount of dishing. So I took them to the local bike mechanic, who asked if there were any spacers, because the wheels were not going to work without them. So convinced was I that the washers went on the outside, I said no! A few days later, I came to my senses, realised they were indeed spacers, and if I had used them the spacing and dishing probably would have been adequate. By this time the mechanic had started dishing the wheels, well one of them, so when I took the spacers in to him, and a frame to make things easier, I thought it was worth getting him to true, round and dish the wheels correctly anyway. The wheels did need some dishing, but not as much as I thought!

One wheel was put in the frame by the mechanic, I had to put the other in. As the axle profiles are different (10mm circular (old) versus 12 mm diameter with two flats 10mm apart (new)), I felt some frame modification was necessary on my bike, as the torque needed to pull my 98 kgs may be too much for a badly fitted axle. So I got to work with my micrometer and a couple of files, removed a millimeter out of the bottom of the drop out, and straightened the sides by another 3.3 millimetres and reprofiled the curve to fit the new axle. All this was carefully calculated and measured out the previous night, and after an hour so of filing, trying and measuring, the wheel dropped into the drop out with a near perfect fit, with the axle on exactly the same centre as before!


This means I am now committed to this being an electric bike! When I do Lynn’s, I will reprofile it, but not change the depth, meaning the wheel will be seated properly, but the axle centre will be 1 millimetre away from the original line.

Next I tried to fit the PAS (Pedal assist System)sensor. A sensor fits onto the bottom bracket, located on a ring which is held in place by the bottom bracket lock ring. A disk with magnets on it fits onto the crank shaft, and pedaling moves the magnets past the hall sensor in the sensor, letting the controller know that the cranks are being used. It’s very simple, elegant and efficient, but it doesn’t work on a modern bike with a small gap between the crank and the bottom bracket. The magnet ring sits hard up against the sensor and the crank. Looking on the web reveals that there are much better quality PAS sensors out there than the two I bought (US$1.50 each!) and I have ordered two more with 12 magnets instead of 5, and a sensor on a stepped ring that will give room for the ring to turn. These cost the princely sum of US$3.50 each!

So without the PAS sensor, the only way of using the bike is with the throttle. Fair enough – that will do me for now.

Normal kits come with brake levers with motor cut out switches built into them, that connect to the controller and cut the power to the motor when either brake is used. As our brake levers and gear change levers are combined units, I did not want to go down this path, so my original order included some hidden wire brake sensors. These go anywhere on your brake cable, I put them between the last part of the outer brake cable and the curved tube which is aprt of the V-brakes. The inner cable is a tight fit through the middle, probably so that when the cable moves a switch or magnetic sensor detects the movement. I removed the first brake cable to thread it through the switch, and the first thing that happens is the cable frays where it was cut! The cable is now useless, and I look at the other three cables and realise the same thing is going to happen to them too. Off to the bike shop to buy 4 new inner cables with very nicely cut and welded cable ends that are not going to fray until I cut them to length. These went through the new brake sensors very nicely, and the brakes all adjusted up nicely. I have very long lengths of cable looped up at each brake, as I don’t want to cut the cable until I am sure!

The standard brake switches are exactly that, just switches that join two wires together, but these devices have three wires, a +ve, a ground and a sensor wire, and these did not fit the sockets on the controller, so some wire splicing and some new plugs and sockets are needed. Bullet connectors have been used for now, these will be replaced with suitable 3 pin connectors eventually.

By now I was raring to go, so I put a bolt through a hole on the controller to attach it to a bottle mount lug on the frame and started plugging in all the various components and devices, which all went very smoothly, very carefully checking the rather bizarre “wiring diagrams” provided (mostly photographs of components on a bench joined together, but cropped so that you can’t easily identify what the component is). There are one or two hand drawn diagrams which mostly need to be “interpreted”. Finally I plugged in the battery, and nothing went bang! Pressed the switch on the throttle, and three coloured lights appeared showing the battery had a full charge. I lifted up the back wheel, pushed the thumb throttle and the wheel spun quietly, smoothly, and in the right direction.

I made sure the battery was tied down, that loose cables were mostly tied back out of the way, brake cables were not going to uncoil and take my eye out and other simple things. Time for the big moment. I started out of the garage and got the bike into a good gear for tackling the hill outside our house, and then pressed the throttle. All of a sudden, the normal low gear was too low, it was like using bottom gear along a flat road. Up a few gears, and I sailed to the top of the hill! Some motor noise was apparent, but that eased off as I got to the turn around at the top of the road, and the power started to kick in on the flat. In my excitement I forgot to take my thumb of the throttle, so the start of the turn was quite exciting, until I braked, and the brake sensors kicked in, and the motor cut out. When I let go the brakes, power came back on very quickly!

I didn’t want to go too far, or mess around too much as too much is unfinished, but I did a few hundred metres up and down the hill, tried both batteries, showed off to my wife, met a neighbour I had never talked to before who saw me out on the bike, and generally got a bit of a feel for what a 300W geared hub motor is going to be like for a 100kg rider on a comfort bike! More on that later.


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