The Plot Thickens

I now have a nice geodesic fruit cage. It’s sixteen feet accross and eight feet high and I’m going to grow blackcurrents in it.

It cost about £70 for the treated 2x1 battens. There are 35 struts 1.43m long and 30 struts 1.26m long. The ends of the struts are cut at a bit of a mitre (73 degrees or so) and they come together at hubs made from two inch lengths of two inch diameter post. There’s a hole at the end of each strut and the struts are all lashed together arond the hub with bailer twine. I bought a double pack of bailer twine for £30, but there’s 14,000 feet of the stuff so it’ll last forever - I’m going to try and sell it by the yard from my shed.

It’s a 2-frequency icosahedral dome, so this means it’s made up of six pentagons, five around the side and one on the top. The spokes of the pentagons are the short struts and the rims of the struts are the longer ones. Putting it all together was trickey. I bound up the pent hubs and tied the rim struts loosley to them and then assembled the five side pents, binding up the hubs as I went. Putting the pent on the top was the most difficult bit, but now it’s all lashed up it’s very strong.

I’ve grown blackcurrents for several years, but not under cover. You can’t grow blackcurrents like that, can you. The birds won’t go hungry this year because I’m leaving the old bushes at the bottom of the plot for now. Although it’s 16 feet in diameter it’s not actually that big so I don’t know how much fruit I can get in comfortably. I did have a fruit cage a few years ago and I made the mistake of not leaving enough room between everything and it was terrible. I’d have liked to have made it a stretched dome, but this was my first attempt so I thought I’d keep it was simple as I could.

Are you ready for Shedmas yet? Last year I had the lights hung but I’m weeks behind this year. A job for the weekend I think

I’ve been having some quality shed-time of late. A couple of those nice chocolate shorbread biscuits from Budgens and a flask of coffee, and I spend a lovely couple of hours in front of the pot-bellied stove burning last year’s bean poles. Last couple of weeks I’ve taken my laptop over there too and joined the shedworking revolution. Not your ideal shedworking environment perhaps, but still good.

Latest on the communal allotment trading hut is that we’re looking for someone to volunteer a pole or so of their plot. I had a good meeting with the council and we’ve agreed to work together on it, though that was almost a month ago now and I’m pretty disappointed that the notice hasn’t yet gone up. If we identify a likely plot and the neighbours are happy I think the proposal will go forward to the council for approval. Lots more hoops still, but it’s still a distant possibility that we’ll be able to start building late summer.

I generated this with my new Schwelder dome script Bactrian.

I’d heard of geodesic domes - I think they entered my consciousness after Apu Nahasapeemapetilon sang about them, but I wasn’t really aware of their older, plainer cousins, the trapezoid domes, and particularly the Schwelder dome. These are what Victroian engineers were fond of, and because their facets are trapezoids they’re in many ways friendlier structures. Because they cleave at any horizontal plane (geodesic domes are particularly unhelpful here) they’re particularly good as low-profile domes, and they take conventional doors are windows well too. I’ve written another script to generate the vertices and topology for trapezoid domes, and after calling the geodesic version Dromedary, I thought I’d call it Bactrian - kind of Dromedary II.

The picture is anything but conventional, and I have absolutely no idea if it could be realized physically, but it shows how the dome can be generalized to other forms. I was quite sold on the idea of a geodesic for the site shed, but I’m thinking seriously about a Schwelder because it looks much easier to tame.

Dromedary is the elliptical geodesic dome-generating software that I’ve been writing. I’ve hung an alpha version on my website here. I used it to generate the struts and vertices for the elliptical dome you see here - it’s 16 feet across, half as long again, and eight feet high. It’s an ellipsoidal dome and because it’s cut off quite low down - it’s nine fifteenths if you’re dome-savy - it has usable height even close to the walls.

I still have some tinkering to do to make Dromedary useful - it still needs to print a decent parts list, and it needs to specify the angles for the ends of the struts, but that’s no great difficulty now that I have the vertices and topology.

Of course, building it is another matter. My plan is to build a fruit cage, but I’ll probably go for a design with fewer struts.

Sorry about that, normal service has now been resumed. I suffered a bit of blog-fatigue after FoGroBloMe and then the cookie had expired and I could find where I’d put my password, and then my dog ate my homework…

Anywho, where were we.

Oh, right, sheds. Have I mentioned how I’ve been trying to build a site shed at my allotments? I have a meeting at the Town Hall next week and I’m hopeful that we’re going to make some progress towards getting permission.

I’m thinking about making it as a dome, or probably an elliptical dome. I’ve been writing a bit of software to generate the strut lengths and angles because elliptical domes are lots more complicated than spherical domes. Turns out that generating the vertices is no great shakes, but printing some kind of plan so it’s possible to bolt all the different struts together in the right order is not so easy. The real problem I’ve had is just labeling the struts in the visualization - it’s increadibly slooooowwwww to render with POV-ray, and dxf doesn’t support it, so I’m having a look at the NetBeans application framework so I can write a viewer - but I’ve got a bit side-tracked. The pic is rendered with POV-ray.