What can you make with twenty eight skateboard wheels, a couple of gears and eighteen feet of rack, a nice chain pulley with forty six feet of chain, shafting, couplers and around three thousand pounds of steel? Well…one thing you could make would be a three part cupola with a retractable section so that your roof could be opened to the sky whenever the need arises.
Sometimes I get to be involved in fabricating unusual mechanical items and this project was one of those. From what I understand, a certain golf course wanted to “hide” their irrigation pumps within a rather picturesque building made to look like an old gristmill complete with a water wheel. The pumps housed inside of this building are fairly large and need to be serviced from time to time which is done by lifting them out of the building with a crane. This meant that there would have to be a way of opening the roof for access on those occasions. The architect came up with the idea of having a three part cupola centered on the ridge of the building roof where one cupola section would retract into the larger center section. They asked me to work out the details and build the framework for it.
The overall dimensions were approximately 26 feet long, eight to eleven feet wide and a little more than eight feet tall from the mounting surface which was a specially constructed pair of steel purlins forming the roof structure of the building. We cleared some floor space to work in my son’s shop because my shop just isn’t big enough for a project of this size unless I were to remove all of my equipment first!
I decided to make four “bogies”, one for each corner of the moveable section, to run on tracks (2″x2″ angle iron) so that one of the smaller cupola sections could roll into the middle, larger cupola section.
I mounted the bogies onto 2″x2″ square steel tubing which would be the bottom longitudinal rails of the retractable cupola frame.
A gear engaged on a rack on either side of the moveable section would provide positive movement via chain and chain wheel mounted on the shaft connecting the gears.
A lot of measuring, cutting, machining, welding and a fair bit of head scratching later it began to look like it would work.
I recruited my wife to help me paint the whole thing inside the shop with BRUSHES!! Normally we would have sprayed it outdoors but inclement weather interfered with our delivery date so you do what you have to do. After a day to dry, one of my sons brought a backhoe home to help load it onto a trailer. We rolled it outside on short sections of pipe which works very well as long as you have a smooth surface to work on. Then we lifted the cupola assembly up high enough to roll the trailer underneath and strapped it down.