Tuesday, March 10, 2015

Rebuilding the back wheel in a hurry

A few months ago I had my back wheel rebuilt by a local bike shop.  At the time, they were unable to get the thick Dutch spokes, so they kindly did what they were able, and fit the thinner Australian spokes, and to accommodate those spokes, put a normal rim on.

However, the thinner spokes just aren't up to the ~250kg gross vehicle mass of the Bakfiets when fully loaded, and so I have been popping spokes and really just fire-fighting on the back wheel since then while I ordered new Dutch spokes, which took a little while longer than hoped to get here.

However, this morning they arrived, which turned out to be not a moment too soon, as I had popped another couple of spokes in the last few days, and was faced with the prospect of pulling the back wheel out again, just to keep it going.

This afternoon at work, however, I noticed that I had a completely flat back wheel, which I had presumed was due to a spoke-head poking a hole in it, since the thin spokes have to be tightened quite hard just to keep the wheel reasonably straight.

Thus I was faced with absolutely having to pull the back wheel out and sorting it all out again. I was much happier to do this going back to the 10 or 11 gauge Dutch spokes rather than persevering with 12 - 14 gauge Australian spokes.

My tyre was very flat, and I couldn't pump it up faster than it was going down, so I assumed a spoke had pierced from the inside.  (I later found the problem was, ironically, the rim tape that is supposed to protect against flat tyres caused by spokes had split, and the sharp edges of the rim tape had made the hole.)


Spot the broken spoke in this image:


And in this one:


After I pushed the bike home, it was time to dive in and start removing the hub from the Australian rim:


Once removed, it was able to stand on its spokes, looking like the Martian battle machines out of War Of The Worlds, emerging after they, too, had extracted themselves from their transportation:


After spraying for martians, the hub was all nice and alone:


I then set about lacing the new wheel up using this really helpful video as my guide.  It was the first time I had actually laced up a wheel, and although I had to back-track a couple of times, it wasn't that hard. It probably helped that I have been changing a lot of spokes recently, but even so, it just isn't that hard.

The next challenge was to true the wheel.  With the bakfiets you can't really sit the bike upside-down and pedal to see how the wheel is wobbling and then fix it.  But I also don't have one of those really nice wheel truing stations.  So I built one out of half a dozen bricks.  After all, you only need something to hold the axle of the wheel, and then something to act as a reference so that you can see how the wheel is wobbling all about.


For the reference, I strategically placed one of the bricks on the ground, so that I could see how the wheel was moving.  Here it is wobbled to one side ...

... and to the other.


Once I had it roughly right, I put bricks more closely on both sides to see if the wheel stayed in line.


Then it was time to put the tube and tyre on, and put it all back together:


I then had to spend another 15 minutes or so tweaking the tension on the spokes because it was sitting a bit too far to the left and rubbing.  But after about five hours, I have managed to rebuild the back-wheel, so that I am not bakfiets-less for the school and work run in the morning.

Thursday, February 26, 2015

One of those days ...

Yesterday was one of those days.

I had a few errands to run, including dropping an old carpet off at the dump on the way to collect some gear for work.

The cargo bike was great for taking the carpet to the dump, and cost only $5, whereas the minimum charge when dumping from a car is $15, so my bargain centre was happy.  Also, it is always fun to see the reactions of the staff at the dump when you arrive on a bicycle carrying a large load.

However, this and other recent heavy work, and hopping down a few too many gutters had caused a problem.

Well, actually, me needing to replace spokes in the back wheel a few months ago was the real problem.  I couldn't find the strong dutch spokes at the time, and so the bike shop rebuilt the back wheel using thinner Australian spokes, and so the back wheel hasn't been as strong as it should.

Anyway, when I got back from running the errands, it was obvious that a few spokes had broken and a few more were on the way out.

So after work I went to the local bike shop, who fortunately are open until 9pm on Thursdays and got a set of new spokes, so that I could fit them at home overnight, and have the bike ready for this morning.  This is the only problem with using the bike 7 days a week, every week, there is no convenient down time to leave it with a bike shop for a few days to do the work for me. That said, the work isn't usually too hard to do myself, and it is cheaper to do ones own bike maintenance, if you have the skills.

With some trouble we measured the length of the spokes, and for $1 a spoke, I had a spare set of 36.

I got home, started disassembling the wheel, and realised that I had forgotten to pick up the spoke nipples.  So another trip back to the bike shop (this time on my mountain bike since the cargo-bike was in pieces by now).  Then I realised that the spokes were too short, we hadn't been able to measure them exactly while they were still in the wheel.  So a third trip to the bikes hop ensued.  Finally I had all the components.

I am getting reasonably practiced at removing the back wheel now, but today for some reason when I removed the roller-brake, which is supposed to be impossible to disassemble, fell apart in my hands when I removed it.  It took me nearly an hour to get it back together, during which time I had a scheduled international call for work.  It was kind of fun and slightly surreal pottering on the bike talking to a guy in the UK while I worked, and completely unthinkable 20 years ago.

What is really odd is that one of the large roller bearings is missing from the inside of the brake.  This is a big thing, and there is no big hole for it to fall out.  It would be like dismantling your engine only to discover that one of the pistons had fallen out somewhere some time in the past.  Very odd.

Once I had dealt with the above frustrations, replacing the spokes was as easy as I had remembered, and I was very surprised to discover that I had got the wheel almost exactly true first time.

Now all I need to do is actually get around to ordering the strong Dutch spokes so that this doesn't happen again.


Friday, December 26, 2014

Electric conversion - part 4

In the last post I left finished up staring blankly at the strange (to me) bottom bracket fittings, like these.


So I had a look through my tools for anything that could possibly fit into a ~40mm disc with semi-circular notches.  I found the following, which I have no idea whether it is the right tool or not, but after using a screw-driver and hammer to tap them loose, I was able with some effort to use said mystery tool to get them the rest of the way off.


The information I had suggested putting the pedal sensor on the right-hand side.  However, that would involve heavy modification to the chain case.  I figured it would just be easier to install the sensor on the left-hand side, where there was nothing to obstruct it.  Installation of the sensor was pretty easy.


Then it was time to put the little wheel of magnets that the sensor uses, and refit the crank.  Again, all fairly painless.


Now that I had the pedal sensor and the electric motor fitted, it was time to turn to the spaghetti of wiring and hook everything up. This largely boils down to matching colours and sizes of connectors.  The only mystery was the purple and black connector, which turns out to be for a brake sensor if you want to immediately cut power when brakes are applied.  This isn't really necessary with a 250W motor and 180mm hydraulic disc brake on the front!


I then attached the controller onto the bottom of the rack where it goes, and fed all the cables through the appropriate feed-holes.


The controller slots in under two tabs, and then a tab is screwed on at the other end, as shown here (sorry for the fuzzy shot):


Then I attached the U-shaped thing that connects to the frame, and slots through a couple of adjustable holes in the rack. 


I already knew that these arms would be too long, so I measured up the length I needed, and cut the first one.  I also gave my rear fender a bit of a clean while it was easy to do with no rack on the back:


After cutting the 2nd arm, and a little fiddling, I had the rack installed on the back:



Here you can see the trimmed arm from the side:

And closer again:


Finally the back wheel could go back in, and the bike was starting to look more or less back together again:


Well, except for the mess of wiring that still had to be routed through:


So I installed the display and power control interfaces onto the handle bars:


Connected the wiring to the motor:


Put the battery into the rack:


Now the backend was looking pretty much right:




But I did notice a minor issue:  Like August Gorman in Superman 3, I realised I now have two keys in separate locations that both need to be in the on position.  Fortunately, I won't need to resort to the same convoluted method as him, but I might need to get one of those retractable key fob things to hang the battery pack key on so that I don't need two key rings.



With everything hooked up, I turned the power on, and was very happy to see that it all seemed to be working:


However, I soon discovered that the motor would only run when I pedalled backwards.  The solution was to flip the wheel of magnets around the other way, as the polarity of the magnets is used to detect the direction of rotation.  Now the motor kicks in when pedalling forwards, but not backwards.

So now it is all working, and a quick test ride confirmed that it is going to be very effective.  The result is that I have a factory-like electric assist install on the bakfiets, and confidence that it will all work well, and that it will be well supported.  Indeed, Dutch Cargo Bikes have been great answering all my questions as I have proceeded through installing this kit over the last couple of days, including emailing photos of bits and pieces of the factory-fitted electric bakfiets they have there to help me work out what goes where.

The only frustration now is that I need to wait before going on any serious rides with it while I wait for the charger to arrive (it was supposed to be in the box, but didn't make it for some reason), and also I need to get a new lower crown race for the new forks, which was never part of the kit.  Both are very minor things, and I hope to be all set by New Years Eve.

Thursday, December 25, 2014

Electric Conversion - part 3

So this is the part where I basically disassemble the entire rear-end of the bike, just to replace the rear-rack and install the pedal sensor that tells the controller when to run the motor.

First step is to get the back wheel off the ground so that I can remove it:


The reason that the wheel has to come out is so that I can take the mud-guard off, so that I can get to the two little lock-nuts between the mudguard and AXA lock.  Here is the bolt heads for these, which are easy to get to.  The hard to get to bit is also hard to take a picture of!


Dropping the back wheel out is something that I have done before, and didn't pose too many problems.  Once you have done it once or twice you realise how not-too-hard it is -- it's just a bit more complex than on "regular" bikes.


Here is the inside of the mud guard, and the little lock nut that holds it on.  This needs to come off, so that the mud-guard can come out, so that I can get to those really important lock-nuts that hold the old rack on:


Of course, to do that, I need to hold the top of the bolt that holds the mud-guard on still, so that it doesn't just spin with the lock nut.  This is in the same nasty little nook as the two lock-nuts I am trying to get out.


To get better access to that bolt head, I had to undo the arms that hold the mud-guard in position.  These needed to come out, anyway.


With that out the way, it turned out that I could get to those two nasty bolt-heads as well, so no need to actually remove the mud-guard.


A few minutes later I had the rear rack off the bike, and could start working on getting the right crank-arm off.  This just requires a 14mm socket and crank-puller.


Soon I was at this point, with the magnets (black wheel with shiny spots on ground), and the sensor itself (silver ring with red sensor part and wires on the ground).


Now I need to figure out exactly how they go on, as there doesn't seem to be any obvious way that the red sensor attaches.

Wednesday, December 24, 2014

Electric Conversion - part 2

Christmas afternoon is a nice time to relax at home this year, so I have been pottering with the electric conversion.

First step, detach the steering linkage on the old wheel:


Then remove the head-stem nuts so that the old wheel can come out:


The linkage arm was sort of hanging about, and I was concerned that this might put stress on the rear end of the linkage, so I put the bike "up on blocks":


Then it was time to take the front wheel out.  The weight of the bike is being supported by the stand and rear-wheel.


Here is my super-helper as I set about transferring the mud-guard from the old wheel to the new one:


The easy part was removing the mud-guard from the old wheel:


More challenging was getting it attached to the new wheel, because the disc-brake mount is right in the way of where the mud-guard supporting arms go:


This really wasn't going to work at all:


You can see in the profile view here how the brake mount (on the right) is right in the way between the mud-guard support arm at the top, and the bracket it needs to be bolted to lower down:


After some creative rearrangement of the mud-guard, I managed to make it work:


It now passes very close, but just clears one of the bolts of the brake mounting:


Now that the disc-brake and electric wheel are on the front, the next step was to replace the brake-lever.  Here it is after removing the old one, and before threading everything back on.  I apparently forgot to take a picture with it all back on.


The next challenge is replacing the rear carrier rack with the one that contains the electronics.  This has some rather fascinating fitting problems of its own which I will get to in another post.