Speedo-Driver Problems

The front wheel with axle and speedo-driver assembly removed

My bike has just celebrated its 3 year birthday, and with it, it’s now required to have an annual MOT inspection (UK), therefore much of the last couple of weeks was spent fixing a few things that needed doing to make it roadworthy. There was a broken weld on the centre-stand and a nail stuck in the back tyre. Most importantly, the speedometer hadn’t worked for a good while now, ever since the speed had first gone ‘off the clock’. I’d been putting the job off because it meant dismantling the instrument display to check on possible causes there.

The speedo works via a little driver attached to the axle by the front wheel (above right, and below). As the wheel rotates, this turns little cogs in the driver, that turns an impeller, which hooks into the base of the speedo cable. At first, I’d come to the conclusion that since spinning the wheel made the little impeller (the slot poking out of the speedo-driver) rotate, then the fault must be with the cable or behind the instrument display. The cable checked out fine, and oddly, so did the instrument display, so I backtracked to the speedo-driver again.

The speedo-driver assembly (attached)

Wheel with speedo-driver coupler removed

It turned out that though the impeller was indeed turning, any light resistance would make it slip. This slippage, it turned out, was due to a worn coupler. The piece – a bit like a bottle cap that fits in a recess at the centre of the wheel – anchors itself to points in the driver via a couple of little tabs at either side.

The tabs on mine were worn away and mashed-up looking, and no amount of bending them would make them engage. Eventually, though, a local bike shop found one identical that got me back in action for the MOT.

The coupler to secure the speedo-driver assembly

A week later though, and the day before the MOT, the speedo failed again. It turns out that the tabs on this new one had gotten mashed down, so I plied them back up again as a repair. I’m not sure why it failed so quickly – maybe the relatively high speed of the bike, and the fact that the cable could do with some grease, resulted in it sticking as it rotated. I’m going to cover the whole length of the speedo cable in grease next, to see if that fixes it. I might also extent the tabs further up by sawing or slitting extra length for the tabs from the base. They don’t seem to go up far enough to make a firm connection with the driver assembly so a bit more bodging might be in order.

The good news, though, is that the bike got through its test just fine. A few days previously I’d had my local bike shop fix the tyre (I took tools with me and took the back wheel off myself), and so all I had to do was hope the speedo would last the duration of the test, which it did.  Despite my concerns (and others’) about my custom-built, LED headlights with their imitation, “dip-effect” function, there was no mention of this. Neither was there any quibble about the ever-so-slightly-too-small licence plate, either. He just tightened the rear brakes up a bit and left it at that. 🙂

Disassembling and Reassembling the Hub Motor

Removing the stator is quite easy, but getting the cover plate off can be a little more challenging

Introduction

The hub motor – like any motor – is made up of two main parts. The first part is an axle surrounded by a fixed ring of copper coils, called the stator. The second part is a housing into which the axle seated, and where it is allowed to rotate freely. This housing, which part of the rear wheel, is surrounded by a ring of strong magnets that surrounds the ring of coils connected to the axle. The hub motors used by most (but not all) electric bikes also have three ‘hall-effect’ sensors seated in a metal ring surrounding the coils, which relay signals back to the controller.

The phases wires that provide power to the motor and the thinner, sensor wires that feed back to the controller are all housed in a thick, insulated cable that runs through a hole in axle to the inside of the stator. To get access to the workings of the motor you need to remove the stator from the rear wheel, and – if necessary remove the cover plate so that the area inside the coils can be accessed.

1) Remove the bolts securing the stator

The stator is held onto the rear-wheel housing by a ring of allen bolts. A ratchet screwdriver with a suitable attachment will make short work of these. It’s a good idea to put them in a little baggy so you don’t lose any.
The

The stator cover – little alan bolts secure it to the wheel

2) Remove the drum brake assembly and push out the stator

First it’s best to remove the drum brake assembly from the other side of the wheel. You can see the drum brake assembly below. Remove the nut and washer from the end of the axle and the drum brake assembly, including the cover plate, lever and brake pads should just slide off in once piece.

The next bit requires a bit of force, but is quite straightforward. Even though the bolts are off, the stator is still held in place by powerful magnets, and needs a bit of encouragement to release. To remove the stator from the wheel, find a piece of wood and rest the wheel on top of it so that the end of the axle on the underside is firmly braced against the ground. Then push down firmly on both sides of the tyre. If it seems stuck, then put your knees on the tyre and bear down with all your weight. With enough force the stator will pop out and you’ll be able to remove it from the wheel.

Here it is removed. Towards the bottom, you can see the hall sensor wires where they meet the hall effect sensors embedded around the edge of the unit.

3) Remove the stator cover-plate

This is as far as you’ll need to go in taking the motor apart if all you need to do is replace a defective hall sensor, but if you need to repair damaged wiring (like on the unit here) or even replace the phase wires for something thicker then you’ll need to also get that cover plate off the stator.

The only thing holding the plate on is the friction between it and the axles’s bearing, however it’s a very tight fit and can’t easily be removed without specialist equipment. A hub-puller of the right size, or a hydraulic press can be used to push the axle through while the plate is held firmly. In the end I went to my local university’s mechanical engineering workshop, and they popped it off with a big hydraulic press.

Once removed, you can see where the cable emerges from the axle on the other side of the plate, and where short lengths of surplus phase wire are covered in nylon and tied back.

Below you can see the ends of the phase wires once released from the cable-ties and with the bits of nylon sheath removed.  You can see where they are joined to the ends of three thick, copper cables which run lead into the banks of coils surrounding the stator. Once you have access to this part, you can make any repairs to damaged wires, or even replace the thinner phase wires that come with some hub motors with thicker grade wiring that can carry more power.

4) Reassembly

The stator cover

Though the cover plate for the stator may be quite tough to remove, it’s usually a lot easier to get back on. In my case, some gentle help using a wooden-headed mallet was enough to get the cover plate back over the bearing.

Replacing the stator

As for putting the stator assembly back into the wheel, this needs to be done with a certain amount of care, as once the stator is far enough into the rear wheel housing, the magnets will slam the stator back into place quite firmly, so MIND YOUR FINGERS!

You will also need to bear in mind that the stator needs to be properly aligned so that all the holes in the case meet up with those in the housing. If not you’ll have to remove and reseat it again until it’s properly aligned. To help with this, I poked a screwdriver through on of the holes in the case and its corresponding hole in the housing so that the stator slid into place reasonably well aligned. Once the stator was in place, I replaced the bolts, diagonally from one another and eventy spaced, tightening them up alternately to ensure that the stator went back in properly aligned.

Removing the Rear Wheel

Removing the rear wheel is a little more complex than removing the front wheel, but is still not particularly difficult or time-consuming. It shouldn’t take more than half an hour to remove, and maybe a little more to put back on again.

The main issue with the rear wheel of an electric bike is that this is where the motor is located, and a cable runs from it and back to the area behind the seat where the breaker, connection blocks and controller are all housed.

You can see the end of this cable below, where the phase wires and hall sensor connector come out and meet up with their respective connectors.

The first thing to do is detach the hall connector plug, then unscrew the phase wires from the connector block so that you can free the cable with the wheel. There may also be a cable tie further down that you will need to cut off.

Before we can tackle the nuts and bolts securing the rear wheel, you’ll need to remove those plastic panels that obscure the bike’s innards to the rear. They’re held on by two little screws. Take these off and put them aside. You might want to take this opportunity to give them a good wash, as this is where road muck tends to gather.

You can see below how the cable is run alongside the left side of the frame, and secured by a couple of cable ties. You’ll need to cut these. You can replace them with fresh ties when the wheel is back on again.

Next you’ll need to deal with the assembly that secures the main shaft of the rear wheel to the bike. On the left side of the bike, two large nuts – the inner one flanged – sit side by side. To its left is a retainer bolt which will have to be fully removed. This will allow the shaft to slide out of a slot in the bar. Loosen off the nuts, and remove the bolt to the left.

The arrangement on the right side is more complex, as this is where the rear drum brake assembly resides.

You’ll need to detach the arm of the brake drum from the brake-cable actuator by removing the nut at the bottom from the end of the cable. Next take the little cylindrical gromit out of the end of the brake lever and put it back onto the cable end, re-securing it with the nut. That way the arm will be detached, but all the bits will be together  in one place when it comes time to refit the wheel.

You’ll also have to remove this bolt that secures the drum brake assembly to the frame.

Finally, as on the left side of the bike, loosen off the nuts and remove the forward retaining bolt.

The whole thing – rear wheel, drum and axle – should now freely slide off the slots that hold it in the frame.

To refit the wheel, you just do all this in reverse. However, be careful to ensure that the cable is correctly routed along the outside of the frame (and re-secured with fresh cable ties) before you reconnect the hall sensor and phase wires.

When refitting the wheel, you’ll also notice there’s some free play either side, where the axle can slide one way or the other. To make sure the wheel is on nice and straight, it’s a good idea to take a ruler and measure the distance of the axle either side from the end of the bars into which the ends of the axle are seated.

Accessing the Headlight & Front Wiring Loom

Half the battle is finding the ‘trick’ bolt, hiding under that naff sticker on the front.

Two screws either side of the ‘cockpit’ also secure the front panel.

Two more screws secure the little ‘peak’ at the front’s base.

This needs to be slid off to allow the front panel to be released.

Once removed, the front panel – with a little encouragement – will slide down to reveal its innards.

The panel can be removed by detaching the connector for the headlight cable.

Et voila! The lock assembly, indicator flasher unit, horn and headlight assembly are all now accessible.

Adding a Car Accessory Socket

A nice feature for any vehicle to have is a power socket. The classic ‘cigarette lighter socket’ is practically ubiquitous in cars, and accessories based on this fitting are widespread. Anything from phones to sat navs are equipped to use it as a source of power. It’s also handy for running a small compressor to put air in your tyres.

The Car Accessory Socket – Increasingly useful in our Gadget-cluttered World

Parts

• A car accessory socket (Maplin: A59FL)
• 2M of 10A figure eight power cable (Maplin: XS71)
• 2 female spade connectors and 2 6mm ring connectors

Tools

• A drill with a 25mm bit
• A pair of wire snippers
• A crimper or needle-nose pliers

This is very easy to do. The only issues are with the practicalities of mounting the socket in a suitable position, and running cable to a suitable source of power.

1. Choosing a Site

I decided to mount mine in the lockable ‘glove compartment’ box, as obviously it should be weatherproof and reasonably secure. The clear choice here was either the left or right recess.

A quick look under the front-wheel recess shows that the horn is directly in front of the left recess, and may risk getting hit by the drill-bit. The space behind the right recess is a little more roomy and easier to reach and work around.

2. Drilling the Hole

The first thing to do is to drill a hole. The hole actually needs to be 28mm if you’re using the connector I list, but a 25mm drill can suffice, as the plastic is soft and the hole can be easily ground larger with the bit.

3. Connecting the Cable and Mounting the Socket

Next, you need to prepare your connecting cable. Crimp the spade connectors to one end of the figure eight cable, then thread the connectors through the hole and plug them onto the terminal heads at the back of the socket. Once this is done, thread the big plastic nut that comes with it up the wire and into position behind the compartment. It’s easier to reach this area if you turn the wheel hard right so the forks are out of the way.

The socket can then be pushed through the hole and secured from the back of the compartment casing by the nut. It’s a good idea to use a large rubber gromit or some silicone sealant here to prevent water seeping through the join during bad weather.

It’s also a good idea to tape the cable to the inside of the bodywork to keep it clear of the forks.

4. Connecting the Cable to a 12V Source

Next, the cable needs attaching to a 12V source. It might seem logical to simply attach it to a live 12V wire in the nearby instrument panel loom, but the problem with that is that this will only be life while the ‘ignition’ is on. I suspect that most people, like myself, will want to be able to charge or power things without the keys sitting in the ignition.

So I have opted to thread the cable to the last battery in my (currently 60V) bank, where it will be available as ‘always-on’. This may raise battery charge-balancing issues with frequent use, so you should occasionally balance your batteries as a matter of course to keep them at peak performance.

I’ve run my cable alongside the existing main wiring conduit along the left side of the bike, so that it emerges into the battery bank under the seat. You can remove the side panel by unscrewing the bolt and screw securing it at either end and releasing it from its retaining clips.

Cut off the wire at a suitable length, attach the ring connectors, and secure the end of the finished cable to the terminals of the battery of your choice. In my case I’ve opted for Battery No.5 of my 60V system, as I charge this battery separately anyway and use of the socket won’t throw it out of balance so easily.

Remember – the positive terminal of the socket (marked on the plastic) goes to the positive terminal on the battery.

And there you have it: A ready power socket for all your rechargeable doodads and other accessories!

Changing The Front Disc

It’s a very straightforward job. The front wheel is held on by a nut and long, flanged hex-head bolt that passes through a shaft running through the forks, the wheel and an odometer assembly inside the right fork. Here is the assembly with the left fork, shown from the front. The big bolt in the middle is the one you need to remove to get the wheel off. To the left, you can see one of the sunken hex-head bolts that hold the disc to the wheel itself.

1) Use a spanner/socket to get the wheel off, but have something to rest the front forks on while you’re working on the wheel. Here’s what it looks like with the wheel off. The Odometer assembly hangs free on its cable to the left, and on the right you can see the bolt that held the wheel on. The inverted bucket is for the forks to rest on if it tips forward on its stand.

WARNING: Do not operate the front brake while the wheel is detached. The piston will pop out of the calliper head.

2) The disc has three larger holes for the bolts that hold it on. Here’s the new one I got, face down. Take the old one off with a suitable socket. I tried to use an alan key at first, but the bolts were too stiff, and I was only going to end up stripping them. In the end I got a socket converter to use with hex-head screw-driver attachments.

3) Replace it with the new one, but make sure you put it on the right way up! You can see which way is front by the recesses for the heads to settle into.

4) Tighten the nuts and put the wheel back in place, pushing the bolt back through the left fork, out the other side of the wheel and through the shaft in the odometer assembly. You’ll need to twist the whole thing slightly forward of the right fork to get the odometer assembly to squeeze back into place.

5) This is the wheel as the odometer assembly is being slid back into place. Make sure the hook on the assembly engages into the slot designed to receive it, or something nasty will probably happen when you try to drive it. Once engaged in place, slide the bolt the rest of the way through and put the larger nut back on the end (don’t forget your tax disc holder, if you have one mounted here!).

All done! Easy as pie…