Tuesday 1 July 2014

Heart transplant for bike.2

The motor in bike.2 is broken. The gears melted, and I can't get a replacement at a sensible price. So on Friday evening, I ordered a new motor from Germanladen, via Ebay. It's a 48 volt motor, it comes already laced into a wheel, and it comes with a controller, throttle and everything else that you might need. And it cost £179, including carriage, which is a very keen price. They're based in Portsmouth, so I won't need to pay any extra duty, or Vat, or other special charges that you pay when importing goods.

It arrived today! That's very quick, because they wouldn't have seen the order until Monday. Unless they work weekends.

The first thing I did, was take off the tire and tube that it came with. There's nothing wrong with them, but I want to use my kevlar tire with the extra gel insert, and my thick puncture-resistant inner tube. That was easy to do, and I noted that the rim is double-walled which means it's extra strong. And then I turned the bike upside down and dropped the wheel into the forks. A slight surprise; the wheel nuts are 21 mm, which is a lot bigger than the usual 15 to 18 mm. I added a torque arm, tightened everything up, put the bike right way up and installed the controller and the throttle. I also connected my handlebar voltmeter up to the output from the controller labelled "headlights" because that output is at the battery voltage. I put cable ties all over to make it a bit neater, and took four batteries (three 4s and a 2s, for a total of 14s, and connected it up. 14s is 52 volts nominal, which is close enough to the 48 it wants. Freshly charged, that's 59 volts; nearly empty that's 45.

The speedometer gave me a slight problem.The spokes are thicker than a normal bike (that's good), so the speedometer magnet wouldn't screw on to it. I got round that by taking a couple of strong magnets and letting them hold on to the spoke; that seems to be good enough to run the speedometer, and if the worst comes to the worst and they fall off, then that just means I don't know my speed.

I took the bike out for a run. It ran nicely. The controller limits the current draw to 22 amps (my wattmeter confirmed that). So I could probably get more oomph out of it if I used my Infineon controller.

The bad news is the weight. It's gone from 52 pounds, to 59. And that's entirely down to the motor. Still, if I don't lift it, that won't matter. And I'm sure I can lift 59 pounds when I need to; bike.1 is 58 pounds.

I have a few finishing touches to add; I want to put a metal plate to protect the place where the wire comes out of the wheel, and I want to add a second torque arm. I want to put curly-wurly plastic over the wiring to make it look neat, and I'll add a few more cable ties.

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