Friday, December 18, 2009

Rack and pinion skylights

Rack and pinion gears convert circular momentum into linear momentum. As the pinion gear rotates, the rack is driven one way or the other in a linear fashion. I'm sure there are a number of fascinating metaphors and analogies this could inspire, cosmic, temporal, spiritual or psychological, but that can be your part of this blog. My part will be to describe what I did today:

The greenhouse skylights are operated automatically by means of a tube motor working off of temperature sensors and a computerized controller, rotating a steel shaft. A system of rack and pinion gears mounted on the shaft, which is attached to the rafters with pillow blocks, push or pull the skylights open or closed according to temperature settings in the controller.

The gears and blocks are fitted with zerc fittings to allow for grease to be pumped into the contact surfaces, to reduce friction and assure a smooth operation. This needs to be done once a year or so, because the grease gets old and dries out(obviously).

I decided to clean off that old hardened grease first, and oil the shaft, which is getting coated with rust.

(pillow block, before cleaning)

Here below are the cleaned and regreased racks & pinions in room 5:

When the skylights start making too much noise as they open or close, I can tell it's time to relubricate the gears and pillow blocks.
The pins at the bottom of the shaft are a safety feature to prevent the rack from exiting the pinion gear altogether, should the controller or the tube motor fail to stop rotation according to plan. Having seen what happens when things go wrong with rack & pinion gears, it gives me peace of mind and satisfaction to know these are operating smoothly.

Here's what the rack & pinions looked like in room 4 when I got up close:

And after cleaning and relubrication:

The view from up there:

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