What to do with a Warped Brake Disc…

October 23, 2010

So, what to do with that warped brake-disc that’s been lying around since I bought the bike?

Be the envy of your neighbours and impress pretentious artists by turning it into this delightful timepiece…

An old clock bought from Age Concern for £1, and a bit of glue, and voila!

Step aside, Damien Hurst! 🙂

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Building a Battery Header Board

October 18, 2010

The Battery Header Board – A handy way of accessing the terminals of the Primary Battery Bank

Parts

Tools

  • A crimper
  • A pair of wire snippers
  • A soldering iron and solder
  • A sharp blade, like a Stanley knife
  • A hacksaw
  • Epoxy resin glue

Battery Balancing

SLA battery banks that are connected in series and then charged via a 48V, 60V or 72V charger (depending on the number of batteries) are not always charged evenly, and when the bike is used, the batteries do not discharge evenly either. This is due to discrepancies in the quality of batteries used. With constant use, and over numerous discharge/recharge cycles these discrepancies become magnified and the charge in the batteries fall out of balance, with some cells having a higher charge level than others.

If the bike is not used very often, and is periodically charged to maintain the the batteries, then they will – over time – naturally self-balance. But if the bike is used frequently, especially on a daily basis, then the batteries will gradually fall out of balance. An un-balanced battery bank means impaired performance, as a serial battery bank is only as good as the charge of its weakest cell. Batteries will therefore periodically need balancing, which means charging them all individually with an ordinary 12V charger to bring them all back up to their peak charge.

Because of the poor accessibility of the bike’s primary battery bank, though, this can be a tedious job. The seat assembly must be removed, and the securing cross-bar on top of the battery bank needs to be detached to allow better access to the terminals. Furthermore, if the bike has been upgraded to 60V or 72V, it also means detaching and removing the extra battery or batteries that sit on top of the original bank.

It’s a nice idea, then, to have a convenient way of accessing the terminals of the battery bank by routing a series of small gauge feed-wires from the terminals of the bank to a suitable board. I’ve spent some time coming up with an elegant and safe way of achieving this via an eight pin connector which sits under the seat, and which can be used to monitor battery voltages, and – if necessary – enable individual cells to be recharged without the need for dismantling the bike.

The principle is very simple – to extend leads from each battery terminal to a suitable assembly – but the actual work is quite fiddly and time-consuming. This is something for a rainy day or two, or else – like I did – to break up into little stages to do in your spare time over the course of a week or two.

Building the Battery Cable

The first stage is to build a cable that runs from the battery heads to the female side of an eight way connector that can be mounted in the underseat storage compartment. I’ve used 10 amp figure of eight cable, which is solid enough to carry a charge current (and even to power things off of), but flimsy enough to act as a fuse if an accident happens and the terminal heads get shorted.

First, you need four lengths of the cable. About an 450mm (18″) length of each should suffice as it doesn’t need to run very far. I’ve split this off at the end into two 75mm (3″) lengths, just far enough for the separate wires to reach the terminals of each battery. For good measure I put a bit of heat-shrink at the junction of the ‘Y’ in the cable to secure it.

Next you need to crimp the connectors onto the ends. I’ve used more heat shrink here, and also soldered the crimp for added strength, as it’s important that these don’t work loose.

The final strand of each connector looks something like this:

And here’s all four of the assembled cables that are ready to be combined into one tidy, larger one.

I’ve used a larger bore length of heat shrink, here, to tie all the cables together.

The other ends of the wires are crimped to the spade connectors that comprise the female side of the eight way connector.

The end result looks like this. Once checked for continuity, it can then be hooked up to the bike’s battery bank.

While you’re attaching them to the batteries, use a continuity tester, again, to check which pins of the connector each battery correspond too, and note it down. That way you can know exactly which battery you’re dealing with. This is helpful if you’re running your 12V battery system or other interfaces (such as a car accessory socket) of a particular battery, and would like to keep track of which is which. Here’s the cable in situ, with its connector rigged up to the battery bank.

The Cable in situ, shown connected to the terminals of two of the Batteries

I’ve cut a small rectangular notch by the hole for the extra batteries here in my 72V arrangement, leaving enough space for the wires to sit comfortably, but making it small enough to keep the connector anchored to the top-side of the underseat compartment base so it can’t fall through. It’s also loose enough pull through a small amount and manoevre into the right position to connect to its male couterpart.

Once this is in place, you already have a useful header that can be used to take voltages, and even to recharge with a basic cable. But I’ve gone the whole hog and put together a posh looking board – complete with template – that can plug into this and be used to directly clip one or more 12V battery chargers onto.

Building the Battery Board and Cable

When I cut a hole in my seat for the 60V and 72V upgrades, I put aside the bits of plastic I cut out in case they came in handing later. One of these was just right for me to fashion a little board for my external connector heads. Mine was 160 x 70mm (2¾ x 6¼”) , but you can make this any size you please. Just bear in mind that it’s desirable if it can fit in the space alongside any underseat batteries you have, but shouldn’t be so small that the terminal heads are in danger of being shorted by any clips that you hook onto them. That would make a bit of a mess out of your fuse-grade wiring.

To accomodate the terminal heads, I simply melted holes at set intervals (about 38mm, here) with a soldering iron, then cut off the goop with a craft knife. You could of course just drill them instead.

For the terminals themselves, I opted to make mine from scratch from a piece of copper plate. I cut out little 28 x 8mm plates with a hacksaw, in which I’d pre-drilled holes to thread the wires through prior to soldering.

If you don’t want to go to all this trouble, then you could just use some bolts, and secure them to your wires by sandwiching them between a couple of nuts on the board’s underside. That was my original plan, but in the end I went for this deluxe solution.

I wasn’t happy with the 4mm holes I originally drilled, so I drilled smaller, 2mm ones closer to the end. The old holes were eventually hidden in the layer of my plastic board, so only the new, corrected holes showed round the back. I made my holes small enough so the connectors were a tight fit, then I used epoxy resin round the base where they connected to glue them solidly in place. Be careful not to get any glue on the connector ends where the wires go, as you need to solder them.

Below is the board shown from the underside, with the little (new) 2mm holes showing where we can thread and solder the cable wires.

The next stage is to hook a corresponding set of wires to the other (male) side of the connector. Your wires can be as long as you need them to be to reach the corresponding heads on the board, but I cut each pair to correspondingly longer lengths to help me keep track of which pins I wanted to go to which terminal heads.

I took more pictures this time, so you can see what I was doing to wire in the pins.  I assembled short lengths of heat shrink that the wire would go through prior to crimping the connectors onto the male pins. I also used little 5mm bits of thick copper wire to reinforce the small wires’ connection to the relatively large crimps.

Here I’ve just crimped them, and am about to add a bit of solder to reinforce the connections.

Next, the solder.

Then I push the heat-shrink up into place and warm it with a lighter to give a nice solid seal.

The pins then go into the connector, in the order of their corresponding terminals on the header board.

And finally, the finished cable assembly:

I’ve added another thick gauge piece of heat-shrink to wrap all the wires into one short stump of cable, but you can make this trunk as long as you need. I was content with just a short length as I wanted the board to just sit by the connector in the underseat compartment.

Next, I glue the neck of the cable to the board and reinforce it with a strip of – also glued – insulating tape. Then the wires are cut and stripped to the right size, threaded through the holes at the base of the terminals, then soldered in place. Then I run two other strips of insulating tape along either sides of the boards base, covering the soldered connections.

For the final step, I’ve beautified the assembly by adding a template to slide over the terminal heads and sit on top of the board, which can then be glued on if needs be. It’s a pretty illustration showing which terminals of which batteries the header points connect to.

Tip: You can print the template image to any dimensions you want from the printer ‘options’ or ‘properties’ dialogue of your software. Under the ‘features’ tab, in the dropdown options for paper size (or elsewhere if you’re not using Windows), there should a ‘custom’ option where you can specify the exact width and height of the printed image. You should make the image slightly (2mm or so) smaller than the board to make room for a border if you laminate it like I did.

Next I printed out and cut out my template before putting it through a laminator. I also cut out the holes in the template first, so that the edges of the holes would also be nicely laminated.

Finally, the laminated piece is cut to the right size, and holes made for the terminal pins.

And voila – a handy, professional-looking battery header board for all your battery checking and maintenance needs!


Not so good vibrations…

October 9, 2010

When you put together any assemblage of solid-state parts that are all tucked safely away in a vehicle’s compartment, it’s easy to get lulled into a false sense of a security, thinking of the various components and the wiring that connects them purely as static entities. It’s easy to forget that when you’re bouncing along down roads laden with pot-holes and crevices, all of these items start to vibrate, jiggle or even bounce around in a variety of exotic ways. Toughly clad wiring, and connections that look solid as a rock can start to erode in subtle and insidious ways that can potentially result in a catastrophic failure.

One of the advantages of constantly tinkering with with my bike is that I get the opportunity to look things over, check connections, and fix anything that seems to be amiss. I also become acutely aware of how, across the miles, the most solid looking assembly can degenerate with alarming speed. All the nuts and bolts that hold the bike together can slowly begin to work themselves loose under the barrage of vibrations that assail them while they’re in motion.

The routing of cabling is particularly important in this respect, as trapped, pinched or chafing wires will gradually succumb to friction, resulting potentially in shorts. I noticed this very quickly after I’d rigged up my makeshift cable serving the 12V system.In a hurry to get up and running I’d not given though to this and just squeezed it down the side of the hole with the batteries. Within a week it had started to show signs of wear where it had been rubbing against the too-tight space that had been allowed for it, nicking the insulation to the point that the copper was showing through. Cutting a slot for the said wires, and patching them up with a length of insulation tape fixed the problem, but a more subtle and serious instance of this was already in the making.

If you’ve been following the story of my upgrade you’ll recall how I installed and routed thicker welding cable around the upgraded battery bank. Below are pictures of the work in progress.

Zooming in on the master terminals of this picture, you’ll see how both the positive and negative cables have been routed along side by side, eventually leading to the back of the bike where they meet the Anderson connector.

On the face of it this looks OK, as I was careful to put good, solid lengths of heatshrink by the connector to keep it safely insulated, and the thick insulation on the weld cable is more than adequate. But now think of this all in motion with the batteries jiggling up and down with every bump in the road, and the bolt on the positive terminal scraping against the cable from the negative terminal, rubbing against the thick rubber insulation and slowly wearing through it…

All easy to see with the benefit of hindsight, as, a few weeks later, I was greeted by this sight when I took things apart in the course of doing some work on the bike:

The bolt on the master terminal had been slowly chewing its way through the adjoining cable’s insulation, finally arcing against the bare wire of the negative cable.

Because the arcing was intermittent, I never noticed anything while riding the bike, which worked fine, but there was a real danger here that – had the vibration also loosened off the bolts on the master terminals – the bared wire could have wedged itself against the positive terminal, potentially destroying the batteries or even setting them on fire. Fortunately I saw this before the situation degenerated any further, and the problem was easily fixed with a fresh, double layer of heat shrink, and a new path that kept the two cables well clear of one another.

Don’t make the same mistake as I did here! Because of the layout of the battery bank, the master terminals are very close together. If you upgrade the leads on your battery bank to something thicker, take care to route the cables very carefully and well away from where they can make contact.

Regular inspection and maintenance is really important with electric bikes, as the sheer weight of the battery banks makes them particularly prone to shaking around with quite a bit of force.


K62 – Times Two

October 4, 2010

The Ego Scooter with it’s chunkier K-62s, front and rear

Last week, having replaced the front tyre with a new Continental K-62, I was given a nasty reminder of the fact that – as much of an improvement this was – the rear wheel was still ready to brutally betray me at the drop of a hat.

My first experience of the remarkable crappiness of cheap, chinese-made tyres came in 1996, when my VFR400 threw me off and went sliding down a (mercifully slow-moving) stretch of the M4 on my way to work one rainy morning. With that in mind – and having already had one scare with the Ego’s former front tyre – I was still taking things easy as I negotiated a wet and windy evening journey to the B&Q just a short hop across town. I was therefore alarmed and infuriated when the rear wheel hit a patch of something-or-other, and slid alarmingly at the cusp of a turn into a side-road that led me back home. The offending something-or-other turned out to be two manhole-covers, one in front of the other, and cleverly positioned on the exact arc that any two-wheeled vehicle would be liable to take as it negotiated this bend. I hadn’t seen it in coming, and it was a harsh reminder that I would never be able to use this bike with any real confidence while it had such sub-standard rubbish performing the vital role of keeping it upright and firmly attached to the road.

By coincidence this came just a couple of hours after I returned home to find a “You Were Out” card from the delivery firm charged with getting my second K-62 to me, but it firmed my resolve to put the thing on as soon as I could to complete the job.

The next day I was ready and waiting when the tyre was re-delivered, and wasted little time in removing the rear wheel and taking it over to my local bike shop, where the wheel’s odd-looking, trailing cable proved something of a novelty to the staff. It was duly fitted for the usual tenner, and I put the bike back together again the same day.

The chunkier tyres, I think, look great, and make the bike seem a bit more grown-up. I’ve always found something faintly ridiculous about vehicles with disproportionately small-looking wheels, and the extra 35mm , or about 1½” that the bigger tyres add to the bike’s height are more than welcome as the bike’s now in better proportion to my own (6 foot, 14-stone) frame. The tyre is also about 15mm wider, all the better to make the most of the quality tread.

An incidental bi-product of the added height is that it sits quite a bit lower on its stand than it did before, but this also introduces an added bonus: Whereas before it seemed to require a bone-crunching amount of force with my foot to lever the stand into position, the new angle of attack that the stand gets allows it to smoothly and easily lock into position.

Ground clearance on its stand is drastically diminished, now barely 15mm or so clear, rather than the three or so inches it had before.

This means, of course, being very careful testing the motor with the bike on its stand, as any slight tip to the rear could send it rocketing off forward.

The Proof of The Pudding…

But looks aside, the question obviously is how the bike handles with both of these tyres in place. It had been raining all day and I wasn’t particularly keen on the prospect of going out in this weather, but the continual drizzle and the wet and puddle-strewn roads really were the perfect testing ground.

The roads were pretty empty so I took it for a good long spin, gently pushing its limits to see if it showed any sign of the twitchiness that it had had before. As I went through a succession of traffic lights, I took to braking harder and harder, to see what it would take to cause the bike to lose traction, but I was delighted to see that no amount of abusing the brakes seemed to even remotely unsettle the bike. And even when I eventually jammed both brakes on pretty damned hard, the bike remained solidly locked to the tarmac – the only consequence was a loud squeal of protest from the front calipers.

I got the distinct feeling – in wet conditions as well as dry – that in a fight between the brakes and the tyres, the tyres were going to win hands down, and that I was more likely to be flung over the handlebars than to put this bike into a skid in anything but the most treacherous road conditions.

So all in all, I’m pretty happy with the results, and feel far more confident flinging the bike around. I’ve not leaned too far over on bends just yet, as this is one envelope that is best pushed very, very gently. But so far so good…

Speed and Acceleration

One obvious consequence of the rear tyre being 10% wider (both diameter and thickness-wise) is that the bike will go proportionately further per turn of the motor. I predicted that I would therefore get a slightly higher top speed, but slightly reduced acceleration. I was however, completely unsure about how this would impact on the soft-start, as I was clueless as to how the controller/motor decides how to feed the reduced power to the motor on ‘take-off’.

On my inaugural run with the new tyre – even in the wet – I felt confident enough to welly it up on the straight, on roads where I was familiar with the top speed I would typically get. When I changed the front tyre – if you recall – the speedometer suddenly became (again because of the new distance-per-cycle) noticably less flattering in its estimation of my speed, and it seemed much harder to get near the venerated 40mph mark.

But with the new rear tyre, I was definitely reaching the 40 mark a little easier than before, and with some experimenting decided that I was getting maybe 2mph (clock-speed) more than I had before. I also noticed that – as predicted – the acceleration was just a little bit soggier than it had been. The soft-start, though, I’m happy to say, appeared to be completely unaffected. Pulling away felt no different than it had before.

The overall effect then, has only been ever-so-slight, so slight that I did question if I was simply fulfilling my own prophecy. With the benefit of hindsight I would have done a more rigid satnav-based benchmark along a set stretch of road to test this on a before-and-after basis, but there are so many factors affecting performance that it’s pretty hard to control for everything. The presence or absence of my backbox, the charge level of the batteries, the amount of air in the tyres and the prevailing weather can all push things either way.

One thing I can say for certain though is that the tyres fit fine, grip well, and don’t upset the apple-cart in any way that I can tell. In my opinion it’s well worth replacing the tyres simply because the one’s that usually come with the bike just aren’t up to the job of hauling around 32Kg (or 48Kg with the upgrade) worth of batteries. £53 is a small price to pay to make sure that what is arguably the most important part of a bike does a good job and keeps you out of danger.


Removing the Rear Wheel

October 2, 2010

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.