Tag Archives: engineering

Rain-based waterfall in a building

Many large buildings have a high lobby – some of these reach the roof, which in that case is often transparent. Some edifices also have an indoor water curtain in the lobby, or water running down a decorative wall. A way to save the cost of pumping the water up for such a waterfall is to rely on rain. The roofs of high buildings are flat anyway, in order to direct water into internal drainpipes, as opposed to sending the water over the eaves of a slanting roof. If the pipe from the roof is made wide, transparent and put it in the middle of the lobby, then whenever it rains, a waterfall occurs in the pipe. This works best in rainy climates and will be especially spectacular in intense rain and with a single pipe receiving the water from the whole inward-slanted roof. The lobby may become noisy though with the sound of all that rushing water.

Chair material should be breathable

Strangely enough, fancy office chairs are often upholstered in leather or other non-breathable material. After an hour or so, sitting in them gets uncomfortable because the moisture does not evaporate from the skin that is separated from the chair only by some cloth. However, people usually sit in office chairs for hours at a time, and I doubt that the chairs are designed to deliberately provide some discomfort to encourage users to occasionally stand up for health reasons. Especially in a hot climate when the air conditioning may break down or just be too weak, a breathable chair would make much more sense. Making a mesh chair is simple: stretch a breathable fabric on the chair frame. The small holes in the fabric let moisture evaporate from the surface. A mesh chair is probably cheaper to manufacture than a leather-upholstered one.

A reason for using leather may be to signal wealth by using a material associated with expensiveness.

Modern synthetic meshes are as durable as leather for practical purposes, because sitting in a chair is not a high-wear use.

Slippery sidewalk paving

In Singapore, the streets are well planned and maintained, smooth and clean like everything else. However, the sidewalks have one illogical aspect: the pavement is smooth stone, which gets very slippery when wet. Singapore is tropical and humid, with frequent rain. When initially paving the sidewalks, it would be easy and probably cheaper to use rougher covering (asphalt for example) that would not get slippery in the rain. After the smooth pavement has been laid down, changing it is of course costly, and if the locals have adjusted to the slipperiness, then switching the sidewalk cover may not be worth it.

The University of Queensland has a similar problem with the sidewalk in front of its main building. The sidewalk is coarse, like yellow asphalt with 1 cm stones in it instead of sand. One would expect such a coarse surface to provide good grip in all conditions, but unfortunately the looks are deceiving. When that sidewalk gets wet, it becomes slippery like polished glass. Again, it would be cheaper and more practical to pave that sidewalk with asphalt.

A broader point generalising the above observations is that things should be field-tested in realistic conditions before putting them to widespread use. For example, the sidewalk stones should be walked and biked on under all local weather conditions before paving a street with them.

Perhaps the smooth stones in Singapore are meant to make street cleaning easier. Still, there are materials that do not become slippery when wet and are smooth enough for mechanised cleaning and cheap enough to use as pavement.

Ventilation switch that detects odours

Many homes in the US have a switch to turn on the ventilation in a toilet or bathroom. Also, all kitchen range hoods and laboratory fume hoods I have seen must be manually switched on and off. Of course the ventilation could be run continuously, but this would be noisy, waste electricity and remove warm air (or cool air-conditioned air in hot weather) from the building. For toilets, bathrooms and kitchens, the main reason to ventilate the room is only temporary – removing odour or humidity.

An untapped business opportunity is to produce a switch that detects odours or humidity and turns on the ventilation just long enough to remove these. Humidity detection is easiest – just connect a hygrometer to the switch. Detecting smelly gases such as grease vapour in the kitchen, hydrogen sulfide, methanethiol and dimethyl sulfide in the toilet may require spectrometry or a chemical reaction. Laboratory gases are probably the most difficult to automatically detect due to their variety.