current weather status
Includes readings for the past week
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View myPMB's current weather status Includes readings for the past week |
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*** Welcome to my PMB blog, the umpteenth! ***
The Corona Diaries
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When the President announced that the country would be locked down in a couple of days time in order to contain the COVID-19 Virus, I immediately checked the cellar. Two bottles of Shiraz and one bottle of Sauvignon Blanc, we were in trouble. Fortunately Edith was already en route to Cascades and she was able to sort out that problem almost immediately.
The next problem was not going to be solved so easily. We needed a stationary bicycle trainer. I immediately started phoning the local sports outlets and bicycle shops. No luck. We might as well have been looking for toilet paper. We then phoned a few friends and those that had trainers, were either planning to use them, or had just sold their trainers. I kid you not.
So we entered lock down confined to house work, gardening and physical jerks, some with weights. Desperate I decided to try and construct my own stationary bicycle trainer. My first effort involved building a wooden framework to hold two sets of concentric pipes such that the outer pipe of a set would be able to rotate around the inner pipe. The two sets of pipes would be positioned in the wooden framework in a position such that the rear wheel of a bicycle could be placed on the framework such that when the rear wheel rotated, it would do so by rotating the outer pipes around their respective inner pipes, and in ndoing so, the bicycle would remain stationary.
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Where is the bike you ask. Well, to test the rollers we placed the bike\'s back wheel on the rollers, and Bruce got on the bike. Then with me holding the bike upright, Bruce started to pedal. It worked, the back wheel rotated and the bike remained where is was, positioned on the rollers. Unfortunately the noise was horrendous, despite the generous layer of grease I had placed on the inner pipe\'s outer surface, before inserting it into the outer pipe.
The only explanation has to be that the 3 millimeter difference between the inner diameter of the outer pipe, and the outer diameter of the inner pipe, was too great. The outer pipe was literally rattling around inside the inner pipe as it rotated around it. One would have thought that the weight of the cyclist forcing the back wheel down onto the two rollers would have kept the inner surfaces of the outer pipes in contact with the respective outer surfaces of the inner pipes. That clearly was not happening.
Was I expecting too much? You be the judge.
Wikipedia records that the simplest form of bearing, the plain bearing, consists of a shaft rotating in a hole. Lubrication is used to reduce friction. Also that the Egyptians used roller bearings in the form of tree trunks under sleds. The earliest recovered example of a rolling element bearing is a wooden ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi, Italy. The wrecks were dated to 40 BC. Leonardo da Vinci incorporated drawings of ball bearings in his design for a helicopter around the year 1500, and the captured, or caged, ball bearing was originally described by Galileo in the 17th century. The first practical caged-roller bearing was invented in the mid-1740s by horologist John Harrison for his H3 marine timekeeper.
Would I try again? Not without ball bearings!
If you have any comments, corrections, suggestions or plain criticism, I would appreciate it if you would communicate the same to me.
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Google+ | www.robdempster.com |
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