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.