Firebroke#
Thu, 07 May 2009 16:13:54 +0000
This seems as good a place as any to describe what we've been doing lately with the Firebrox, LFNS's bicycle-based mobile sound system, and why you haven't seen it out much lately.
The background
One of the system's original design objectives was to get the speakers up high, so that the sound carried further instead of being projected striaght into the bodies of skaters surrounding the bike. Speakers are heavy, so this needs a stable platform, which means a three or four-wheeled vehicle
Well, obviously, most bicycles (the clue is in the name ...) are built with two wheels not four. Back in 2006 when we were specifying it, the chassis options appeared to be the Rhoades Car , the AVD Stablemate and the Brox Compact and the decision ended up being based mostly on availability/price: we found a second hand Brox Compact for a sum which left us some cash over for buying the audio equipment.
The problems
There probably aren't many people who have personal experience of trying to ride a 3 foot wide 70kg bicycle in the middle of a crowd of skaters, so you might have to take it on trust when I say that it's hard on the bike. These things are specced for carting boxes around warehouses, riding mobile advertising hoardings around town, or making deliveries - at a sedate pace and steady speed, usually in daylight. Where are we using it? At night, under constant braking and acceleration as skaters cut in front or veer into its path, and through potholes - when boxed in by skaters there's often no chance to go around them by the time they appear. If you have any amount of mechanical sympathy, it would make you cry.
That's one problem. The other is that the bike is both unusual and elderly.
Most bicycles (the clue is in the name) have two wheels not four, so if you want to design a bike which has two wheels controlled from each brake lever and 8 feet distance between the pedals and drive wheel, you have some lateral thinking to do. The rear brakes are connected in series, in a configuration which Hope (the manufacturer) says should work in principle but is actually outside spec. The front brakes are a mix of manufacturers (Sachs calipers, Magura lever) with a T joint in the pipe between them.
Most bicycles have a headset (bearings in the front tube that allows the handlebar/forks/wheel to turn) - this one has three (steerer plus two front wheels).
Most bicycles have hub gears built into the back wheel hub, or derailleur gears alongside it: this one has hub gears under the seat, and derailleur gears attached to it, and a cog on the other side with a second chain that runs to (one of) the back wheels. What am I saying? I'm saying it's more than usually complicated, and being something like ten years old many of the parts are obsolete.
h2. The situation
We took the bike off the road at the start of this year to fix it up a bit because it was beginning to look a bit battered: when duct tape has been used in a structural role that's usually a sign to get the wood glue out at the very least. Events between then and now can be summarised as "everything was unexpectedly complicated"
- There are two standards for 1" headsets, which differ in the internal size of the cups that slide onto the steerer. Learning this (when we observed that the usual ISO 1" standard cups would not fit) came as something of a surprise, so imagine the shock and awe accompanying our discovery that the other standard (JIS) didn't fit either. In the end we had to file the new cups to get them onto the tubes.
- To bleed the front brake calipers requires loosening a bolt on the bottom of the caliper to let the air out. This bolt has an M8x0.75 thread, requires an unfeasibly huge tightening torque to be leak-free, and has an Allen head which is made of cheese. You can see where this is going, can't you?
- To bleed the front brake calipers successfully requires getting all the air out (obviously enough). We managed this once and once only, after trying the lever, calipers and lines in more orientations and relative positions than the Kama Sutra - albeit with mineral oil substituting for yoghurt. Our best success was with the calipers lying on their back, though as it was unrepeatable I think there may have been something else involved too. "Damnit Jim, I'm a cyclist not a plumber"
- and, well, other stuff. Even the new paintwork involved bizarre chemical reactions and blistering (of the paint, not the painter)
h2. The upshot
We have ordered some new front brakes: calipers, lever, cables, discs, the whole caboodle... They're the Magura Big, which is designed for this kind of application (apparently they are made by the "Industrial Controls" division, not the cycle division). They are expected to arrive next week. When they do we will find that we can not mount them directly on the frame and will need to make adaptors from IS mount to strange-obsolete-Sachs-mount: happily we have anticipated this and think our tame Alu expert will probably take a week or so to come up with the goods.
So, possibly a couple more weeks without music on the LFNS if all goes to plan.
Is the end in sight?