Watchtower part 1

 I have always wanted to make a shallow dome roofed watchtower of some sort and over the years scribbled many thumbnails of the sort of thing I had in mind. Until now I had never found a suitable large shallow dome... then one suddenly appeared ouit of the blue, part of a microphone shield that had been removed at work.

The thick acrylic blow moulded shallow dome with a diameter of  695mm ( 27") was perfect for the roof of a 1/16 scale structure. The first thing I did was to scribble up a new sketch of the general arrangement.

I trawled through my hoard of scrap materials and dug out anything that looked like it could contrubute to the project. 

The picture below is shows the general layout as it stands.

The main support column comprises 150mm PVC pipe with a 150 to 100mm reducer. This then joins to a black part from a broken water pump. The watre pump part then joins to a plastic salad bowl on top of which is a plywood disc that has a bunch of custom 3D printed parts, another plywood ring with a window made from thin polycarbonate (lexan) window. The dome then sits on top of that.

The 3D printed circular segments were designed in Onshape and then printed out at home on my Anycubic Kobra Neo FDM printer and a few at work on a Prusa MkIV. The Prusa prints were faster and slightly smoother. This is not surprising as the Prusa cost 6 times the cost of the Anycubic machine.

Anycubic Kobra Neo print on the left, Prusa MkIV on the right.

Close view of the Anycubic Kobra Neo print.

Close vie of the Prusa MKIV print.

The printed parts were superglued to the underside of the plywood ring with a 3mm black foamed PVC sheet spacer inbetween. The white wall that seperates the plywood ring from the plywood disc floor is also made from 3mm foamed PVC sheet in this case white.

On top of the plywood disc (or in actuallity underneath) was glued the palstic salad bowl with a amller plywood disc acting as a locator and re-inforcing the glue joint. The salad bpwl had the bottom cut off and ws securely superglued with baking soda re-inforcement before attaching to the plywood.

More 3D printed parts were arranged radially around the salad bowl and superglued.

The water pump part has a threaded end with a locking ring. I decided this could be usefull to seperate the column for tranport. A piece of solid PVC sheet was cut to fit inside the locking ring and glued and screwed to the top of the PVC reducer. It acts a lip to so I can easily lock the bottom part of the column to the top and  seperate the two parts when required.

In the picture above you can see I have started to add detail to the pump part of the column. The pump hosing had a cast aluminium heatsink to which I added a perspex plate using the existing threaded holes. To the acrylic plate I have added atank made from  part from a commercial toilet roll holder with a coffee machine spout part glued to the top. Detailing has also started on the PVC reducer.

To the bottom of the column I added a short scrap of 200mm gas pipe to give it a wider stance and better stability. Some detail parts have been added, with a lot of pipes made from heat bent solid ABS rod.

The chunky pipes shown above are from a childrens toy which is basically a pipe assembly kit.

The next design task was for a 3D printed door. Again modelled in Onshape and printed on the Anycubic Kobra Neo. 

The figure in the doorway is a 1/16 scale Bruder toy man. A large hole was cut into the base of the PVC column to fit the door.

I made a slight modification for an interior door inside the wathtower itself at the top of the column. It has to fit a smaller diameter PVC tube and has a flat base rather than the round base of the exterior door.

On top of the dome I mounted a motorised communications dish which I have had sitting around for at least a decade for just this project. The dish sits on a planetary drive gearbox and motor that rotates it at slowish speed.

The height of the model to the top of the comms dish is currently sitting at 1325mm (52").

Thanks for looking.

More soon...