…plus lots of other updates
It’s been a little quiet on the blog over the last week or thereabouts so I wanted to I’d like to share a number of things that have happened during that time…
After dropping off the motors and wheel rims at Halfords in Llandudno, the guys were able to take all of the measurements, but weren’t able to locate the correct spokes from any of their suppliers. Just like me, they did some digging around and the only suppliers they could find were in China. I’ve since ordered the spokes from China, but of course they’re all celebrating the Chinese new year at the moment so it’s going to be a number of weeks before they arrive.
The first 48v battery pack is ready. After bottom balancing all of the cells, I was impressed as they were charging as most of them remained within 0.001v of each other, and there was just one other cells which was 0.002v behind the others. Fully charged, this is a 56.5v battery:
Interestingly, John Williamson (Aka Burgerman) of www.wheelchairdriver.com has been reading through my posts, and based on his background working with charger manufacturers in an advisory capacity for 25 years, he’s suggested that bottom balancing is the wrong way to go about this. Thanks for taking the time to read my posts John, I think more research is required on my part.
Grinding away the Dropouts
With much trepidation, I spent a large part of yesterday grinding away part of the BMX forks to get the motor axles to fit. Looking at them though, I’m really worried that the dropouts on the forks (the part where the axle will sit), aren’t going to handle the torque produced by these motors. I’ve had to file so much away, that there’s far less metal on the forks now than there used to be. Originally, I imagine an engineer would have calculated how much metal needs to be there:
Snapped dropouts is a common problem with e-bikes:
To overcome this, you can buy and attach what’s called a universal torque arm. This arm takes the torque produced by the motor and transfers some of it higher up the forks where they are stronger:
My only problem with this is that I think they look untidy. I gave it some thought last night and have made some rough sketches of a purpose built “torque arm” that will bolt to the frame. If I can get those made up at a reasonable price that’s what I’ll do, if not then I guess I’ll have to go with these unsightly universal torque arms.
At least the motors look cool now that they’re sitting in place and Ada’s really pleased with the purple dust cups which she chose.
Six motor controllers arrived from China yesterday and at first glance I’m really happy with them. They’re far smaller than I expected them to be which means they’ll be easy to fit within the mountain wheelchair frame.
The main problem I have with these controllers though is that the Chinese user manuals have been badly translated into English. Trying to understand what the manual is trying to say is rather difficult.
Whilst I was waiting for the controllers to arrive, I was however able to produce a wiring diagram to provide power the 6 motors:
Once I had the wiring diagram and knew what I wanted to achieve, I then spent days searching through online components for the parts I needed. Trying to find a simple thing like a 48v switch (200a and waterproof) has been impossible in the UK so I’ve had to resort to getting parts shipped from China again.
Actual working Mountain Wheelchair Motors
Nonetheless, and this is quite a big moment, I’ve just managed to get the actual mountain wheelchair motors running for the first time!
You’ll have to excuse the temporary wiring, but, Woohoo! It’s working!