Mountain Wheelchair Motors have been left at Halfords

This was the scariest moment so far in the mountain wheelchair build…

Last night, I dropped off all of the motors and wheel rims at Halfords Autocentre in LLandudno.

This will be first task that I’ve had to get somebody else in to complete and I felt extremely nervous walking away, leaving all of the wheelchair parts in somebody else’s hands – What if they don’t do a good job of it? What if they drop one of the motors? What if something gets damaged? Do they realise how important they are?

To be honest, the two people I spoke to were very reassuring, and the girl at the counter added to the label “Guard with your life”.

They were kind enough to let me take a photo for the blog – “bye bye motors, it was nice knowing you”

And, they even said they’d take some photos as they carried out the work which was pretty cool.

If you’re reading this Will, then I’d just like to say a big thank you for offering to do it. In the end I thought it best to go to a store to do it because it meant that if they did get damaged then I’d be able to recover the costs.

All in all, I’m a little nervous, but at the same time extremely excited. The wheels were one of the first things I started thinking about when I began this journey. Once the motors are sitting in their rims, they will be the first part the mountain wheelchair which will be finished. No more research, no more designing, done, finito!

So long as everything goes well of course :S

*Update*

Received a call from Halfords the following day to say that they had done all of the measurements and found that they needed an odd size spoke which they couldn’t obtain from their suppliers. They did however email me a link to some on ebay, but they’d need to be shipped from China. The good news is that they’ve done all of the measurements and at least now I know what size spokes to get.

I’ve been into Halfords to collect the motors as the motor controllers will soon be arriving and I want to start playing with the electronics whilst I’m waiting for spokes to arrive.

First look at the Mountain Wheelchair Motors

So the 6 motors which will be used on the mountain wheelchair arrived this morning and I couldn’t help but open them up to take a look inside to make sure they were up to spec’.

Externally, the build quality looks great are the dimensions are perfect for the wheelchair. To get inside the motors you need a special tool usually, so I was really pleased when I undid the screws on the housing and it easily lifted away.

With the housing off, the first thing I noticed was that if I turn the axle, the motor spins much faster. 5 times faster to be precise. So that’s the first thing ticked; the motors will be able to spin at their optimal speed thus improving their efficiency, reducing the heat they generate, and all the while producing more torque.

Motor Windings

The second thing I noticed was that there are in fact 32 magnets with 16 pair poles, unlike many of the cheaper motors which have fewer magnets. This should result in a quieter motor with improved torque.

The motor also has a 20T winding (all of the copper wires which are wrapped around the “magnets”):

These copper coils are what create an electromagnetic field when electricity is passed through them. As the “magnets” turn on and off in the right sequence, it turns the motor. Typically, the hub motors on ebikes have 6 to 10 windings (the amount of times the copper is wrapped around to create a magnet). A bike with 6 windings will travel at a higher speed; because there is less copper for the electricity to pass through it gets where it needs to be quicker. A 10 turn winding motor will therefore go slower because it takes more time for the electricity to pass through the coils. What this Chinese company have done for me is 20 turns which means that although the electricity will take twice as long (in simple terms) to pass through the coils, the resultant electromagnetic force will be twice as strong, thus resulting in a motor which has far more torque and travels at a speed which is more appropriate to a mountain going wheelchair.

Planetary Gears

Although I was happy with what I’d seen so far, I must admit I was a little disappointed with what I found when I extracted the motor from the housing; plastic Gears!

Presumably the gears are made from ABS or Nylon and should last some time, but I can see myself having to service them in the future. At least I’ve got a 3D printer though so might be able to make the gears myself. I would have preferred steel(?) gears but I imagine these plastic ones will at least be quieter and cheaper to replace.

Freewheel Mechanism

Finally the other thing I wanted to have a look at was the freewheel mechanism. Bicycles are intended to roll down hill without the rider having to pedal constantly. For this to happen geared e-bike hub motors have an internal freewheel mechanism. For the mountain wheelchair, this presents a problem because when put into reverse, the motors would just spin freely without turning the wheels.

I’ve read about some people overcoming this problem by welding the freewheel mechanism, but the company that made these motors for me came up with a far more elegant solution. I believe it’s called a Woodruff Key?

Verdict

So all in all, I’m a little sceptical about the plastic gears, but other than that I’m really happy with these motors; they’re lighter than direct drive hub motors, consume less power, they have internal temperature sensors but are less likely to overheat anyway, they’re well engineered, and importantly they should provide more than enough torque to get this wheelchair into the mountains.

In Other News

Now that I have both the hub motors and the wheel rims, I need to get the two things attached to each other. I’m not sure what, but something in the back of my mind tells me that it’s quite difficult to balance a rim on a hub. Add to that the fact that I don’t know what size spokes I need, I figured it was time to get some external help.

The first thing I did was ring West End Cycles in Colwyn Bay. The quote they provided over the phone, for all six wheels, was nearly £1,000! Just for putting some spokes on! Perhaps I’m just not appreciating how difficult it is?

I then rang Halfords in Colwyn Bay. They wanted £25 in labour per wheel, and although the guy on the phone was struggling to find the best price for spokes, he was able to find some which would cost about £35 per wheel. This puts the total quote from Halfords at £360.

Finally, I’ve got one more person to try who I discovered lives just around the corner from me. When I’m not so full of cold I’ll ask for him to have a look and take it from there.