Building an ebike – My experience (Guest Blog contributor : Peter Sharpe)

Given the previous post, if you’re delving into this one too, you’re either thinking ‘hrm I wonder if my wife will let be buy one’ and/or ‘hrm I reckon I could build one’

Read this next bit – then we’ll revisit the options…

I set about converting my 2006 Trek 1000 road bike into an ebike in order to reduce the severity of some steep hills on my commute. And to overtake cyclists who are fitter than me.

I researched the options and ultimately settled on an ebay rear-wheel hub motor kit (with cassette style freehub) branded as ‘Yose Power’. I then had to buy the battery separately – you have to study the specs quite closely to make sure you get the right voltage and amp-hours for your motor, and make sure that the power adapter cable will fit etc.

The kit and battery were both shipped from a warehouse distributor in Germany, but had obviously come from much further afield judging by the Chinese characters on the box.

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I was presented with;

  • The wheel and integral hub motor
  • A controller with lots of wires
  • Two brake levers with cut-off switches
  • A pedal crank sensor
  • Lots of zip-ties
  • A small bag of tools to perform the installation, including a crank puller and a cassette socket.

The process of installation went like this;

  • Remove rear wheel, swap cassette onto new motorised wheel (Fiddly but doable, as I already had the chain-whip and the cassette lockring socket – the one in the kit didn’t work as the teeth were rounded out)
  • Install bottle-cage bracket for the battery (Easy, 5mm allen key)
  • Install motorised rear wheel, requiring some effort to pull the dropstays apart to slot the axle in, install torque-tab washers, tighten up bolts (Quite difficult – adjustable spanner)
  • Install pedelec sensor; (Frustrating!)
    • Attempt 1: To install the sensor (which is basically a tachometer that goes on the crank) the LH crank has to be removed. I attempted this with the crank-puller provided with the kit, and promptly stripped the thread in the crank, defeating any chances of installing this particular sensor.

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    • Attempt 2: Order the split-half crank sensor, wait two weeks for shipping, then install without needing to disturb the LH crank after all.

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  • Install brakes with cut-off switches : The brake levers have a cut-off switch in them which cuts power to the motor when you brake. The power also cuts when you stop pedalling so I wasn’t too fussed about these, but the problem was that the brake levers in the kit were for a straight-bar bike, where I was installing my kit on a drop-bar that was oversized for the brakes, so this was obviously not going to work…
    • Attempt 1: The switches are crimped into the brake lever body at manufacture, so you can’t get them out without taking a hacksaw to the brake body; so I cut them out.

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I then discovered that the switches are of the ‘dead mans trigger’ type, i.e. normally on, braking switches them off. For the controller to work they needed to be permanently depressed… I tried to do this with duct tape, and then attempted to solder the switch permanently, which also didn’t work. I gave up and began searching for an alternative brake switch.

    • Attempt 2: A brake switch which you install directly on the brake cable was located, and could have been integrated more tidily than the brake lever option, but this too didn’t work.

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    • Attempt 3: A search online revealed that you don’t actually need the brake cut-off switches after all, so I decide to forgo them altogether, and with this I plugged all the cables in and the motor worked for the first time.

 

  • Install cockpit: The LCD display and hand-throttle needed to live somewhere – I elected to use a handlebar ‘cockpit extension’ which wasn’t included in the kit.

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The End Result

With the final installation of the ‘cockpit’ up front, the bike was complete and ready to ride. I had chosen a modest 250 watt motor so I wasn’t expecting blistering speed, but on my first ride I was impressed to say the least. (250 watts is also the legal limit for ebike on-road use…)

Suddenly steep hills and inclines that I struggled up previously became gentle inclines, and having experimentally set the ‘governor’ on the controller to its maximum, my new top-speed on the flat was now an enjoyable 25mph 15.5mph! Before I would have struggled to maintain 20mph 10mph continuously, now it was almost effortless!

I discovered that the controller uses the built-in speedometer inside the hub, together with your pedalling RPM and thumb throttle position to deliver just the right amount of power, as displayed in watts on the LCD screen. It revolutionised my commute, and at time of writing I’ve completed almost 1700 electrically-assisted miles!

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My finished electrically assisted beast!

[Thank you Pete for a both entertaining and informative couple of posts! I particularly like the Spokey Dokey Bikes plug – thanks for that! So there we go folks – if an aircraft hydraulics specialist can manage it, how hard can it be?!? I have not had the pleasure of working on a “Yokes Power” unit, but I have worked on both Bosch and Shimano STEPS systems, so you’re in safe hands (plus there’s always Pete to consult! Thanks again Pete, great posts]

Also, we have added Pete as a permanent guest to post as he wishes – so you’re no doubt in for some real treats!

Chris (and Pete) out.

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