Saturday, August 21, 2010

The bike shop, of course!

People bring us all sorts of mechanical things to fix. Shown here is one of two drive units from water bikes someone dumped on us this week. Aside from the fact that it has pedals and has the word "bike" in its name, it's not something we can service extensively in our facility. Sure, we could provide a crank arm to replace the one that got mangled because the owner neglected to keep the bolt tight. We could tighten the other crank arm bolts. We aren't set up to dispose of any amount of rusty, water-contaminated heavy gear oil. We had no service manual. Undoing obvious things only got us a little way into the dark, stinking interior.

When I popped the top on this, a smell like an oily sewer oozed forth. The congealed remains of its lubricating oil sat like filthy pudding at the bottom of the casing. I looked in with a flashlight. It's sparse and simple. The chain makes a 90-degree twist to go around the propeller shaft. It seemed tight enough. Everything was rusty, but what do you want? This thing gets used in water. I topped up the oil from a bottle of it the customer had provided.

This is the view deep into the second drive unit. The chain disappears into the sludge. The chain was a little loose on this one, but I couldn't get the prop off to see if there was any way to tighten it from the lower end. The upper end only fastened in one position as far as I could tell. The prop was secured with two set screws, which came out easily, over the ends of a pin, which would not budge. Because the unit still functioned I did not want to risk disabling it if things went wrong while disassembling it. I added oil and closed the lid.

People bring us any pin and roller chain, no matter what size, because it looks like a bike chain. They come to us for cables for everything from lawn mowers to go karts to ultralight aircraft. Of course we get the garden cart wheels, too. The bike shop was the birthplace of modern mass-produced personal transportation. The idea that we can fix anything is not so far-fetched. If we had a better machine shop we could really get crazy.


Steve A said...

So, what you're saying is that if the chain inside the entry doors of my 747 needs some TLC, I should taxi it up?

Seriously, an interesting perspective - as usual.

limom said...

Man, I need one or two of those things!
Is it an actual bicycle chain in there? I can't imagine one twisting ninety degrees.
Way cool though it's giving me some ideas.

cafiend said...

limom, the chain is smaller than a regular bike chain. pin to pin distance may be as small as half the pitch of a current bike chain. The link plates might have a lower profile as well. This allows he chain to be supple enough to make the twist in the distance between the crankset and the drive gear.

Steve A, if you can get it into the back parking lot I'll be right down. Actually I could probably board through an upper floor window.

Lee Bell said...

Don't feel unusual about the boat part. I did gun smithing for some years and I've had people bring me everything from golf clubs they wanted refinished to a grandfather clock that needed hand made parts!

cafiend said...

In the early 1980s I was sketching some ideas for a high-performance pedal boat for transportation around Annapolis. I worked in a waterfront area and had access to a launching point in my own neighborhood. It seemed like an interesting variation on riding to work. However, since the job I commuted to was of the bottom-feeder variety, I never had the funds to proceed. Meanwhile, other people's inventiveness has overtaken me. These water bike thingies are very clever.

My idea was a trimaran, actually a monohull with outriggers. It used paddle wheels instead of screw propellers, so the paddle boxes formed the basis for the wings. It would have had an enclosed cabin for foul weather comfort. It was going to have a fixed-gear chain drive, but with a set of sliding sprockets and in-line chain tensioners to provide some different gear ratios for different wind conditions. A clutch system would allow one paddle wheel at a time to be disengaged and locked so the pilot could spin the boat in its own length.

I soon moved inland and changed jobs. My interest in the project faded.