Saturday, February 11, 2006

Fascinatin' Fasteners...

I had to work on my soldering station yesterday. I reached over and switched it on, only to be greeted with a loud BANG as something blew up inside the case. Very often this means a blown electrolytic capacitor in a power supply. These capacitors are two conductive sheets separated by an insulator. In the case of an electrolytic cap, the insulating material will eventually fail. Current starts flowing through the unit, heating it considerably. It explodes. Electrolytic capacitors are polarized, so if you accidentally install one backwards, it explodes immediately. Most technicians only do this once. Once is quite enough.

But before looking at the circuit board, I had to get the case apart. Some black-hearted engineer specified tamper resistant fasteners on this unit. There are a lot of different types of tamper resistant fasteners. These happened to be Torx. They look like a normal Torx head, but there's a pin sticking up in the center that prevents a regular Torx driver from engaging the fastener. There are square drives and Allen heads that are similar.

I spent most of the morning trying to find a TR-15 Torx bit. Finally, as I was about to give up, a guy from Facilities Maintenance said he had a set in his toolbox. "I've had these things for years and never used them!" he said. There's always a first time.

I put the bit in a driver handle, and that's when I discovered the recesses for the screws were too narrow to accommodate the driver. The recesses are about 0.375" and the driver is about 0.440". I took the driver to our machine shop and started grinding it down by hand. It was ticklish, finicky work, because the bit is ¼”, and I had to reduce the driver to under 0.375" (or 3/8"). The wall was going to be very thin. I worked slowly and got the driver down to a size that would fit, and then polished it to remove the grinder marks.

Sure enough, once the case was apart, I found a blown capacitor and a fried voltage regulator chip. I'll order the parts Monday.

But this is supposed to be about bicycles, isn't it? You didn't think I was going to give a lecture about electronics, did you?

It's annoying and time consuming to have to find special tools in order to complete a job, and for those of you too young to remember, I'm going to talk a little bit about non-standard bike stuff.

Back when dinosaurs roamed the Earth, and disco ruled the airwaves, most bikes were equipped with components that came from the same country as the bicycle. Italian bikes came with Italian parts. French bikes had French parts. And British bikes came with whatever parts the factory could buy that year. Much of this stuff was non-interchangeable, particularly the French stuff. Manufacturers used different diameters, different pitch (threads per inch, for instance), and sometimes even different angles on the threads themselves. So where one component might thread into another, the parts couldn't be torqued as tightly for fear of stripping the threads. A copy of Sutherlands Manual, pitch gauges, and a good metric dial caliper were essential shop equipment.

I worked in a shop that sold a lot of French bikes. The handlebars, stems, bottom brackets, and pedals were not interchangeable with any other parts. They were different diameters. But even then, the French would do something squirrelly. I had a Paris Sport track bike with all French components, except for the rear hub. It had a pair of 5/8' nuts on a solid axle. Now, track bikes are normally set up with bolt-on wheels, and most of them are 15mm. With a Campy 'peanut butter' wrench, you could tighten both crank arms and wheels, so why did the French go to 5/8"? It made no sense whatsoever.

But they weren't the only ones.

The Brits, thankfully, used the same standards as the Italians for seat posts, stems, and handlebars (for the most part.) There were some exceptions. One Italian stem used a 6.5mm binder bolt. Try to find a 6.5mm Allen key. Snap-On has them, but bring a thick wallet. They used some odd metric pitches, as well. And the British had to do something eccentric too. They used a British Standard (or was it Whitworth?) binder bolt on some seat posts. We had just one wrench for that purpose hanging on the tool board. I mentioned this to a friend who had a 60's Triumph Bonneville, and he became somewhat excited about the whole thing. Actually, 'excited' probably isn't the right word. He used language he didn't want his kids to learn! He'd bought the complete tool kit for that motorcycle!

Shimano was the worst, in my opinion. They made small changes in their components every year, so the parts weren't interchangeable. If you damaged, say, a derailleur cage by hitting something, you wouldn't simply order a replacement cage. You could, but after the price of the part and shipping, you were nearly at the price of a new derailleur anyway. And I was very hacked off when they introduced the 600 series, and required a bunch of special tools to work on the group. I remember the oddly fluted headset wrenches, in particular. The headset was aluminum, and in order to prevent damage, the tools and components were cut almost like huge Torx fasteners. In reality, this is a very good idea, but it's a PITA to have to get special tools to do just one job.

Things are better these days, mostly. Oh, there are still too many different seat post diameters, for instance, but most parts are readily interchangeable.

This originally started off because I was thinking about tamper resistant fasteners and the security they can offer. Some cyclists fill the cavities in stem bolts and seat binder bolts with RTV or hot glue, in order to foil would-be thieves. I'm sure the larger tamper-resistant fasteners could do the same job.

2 Comments:

Blogger Fritz said...

I've known of cyclists in Chicago who use tamper-resistant fasteners for their removable parts.

4:31 PM  
Blogger Coelecanth said...

My SO is Australian and she get her mother to mail us quick release skewers with 5 sided recesses. Works like a charm because you can't just walk into a bike store and purchase the wrench. I keep hoping to come out of work and find some guy trying to get my wheels off with allen key.

Headsets are the worst for non-standardization. I do maintenance for a bike share program and I've yet to find two of our bikes with the same headset. I guess that's what you get when you can't pay more than $10 per bike. :)

1:25 PM  

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