Portable Ring Sundial – Colin Thorne
Well over a year ago, in fact probably a couple of years ago I had been shown some plans for Colin Thorne’s Portable Ring Sundial while visiting a local model engineer. He had nicely put together a spreadsheet showing the calculations to generate the graph and had passed this on to me. I`ve fancied building it for a while and when I ordered my latest clock book (Gearless Clock) and materials, I ordered a copy of the plans. It always did look a simple build, the problem is an accurate graph needed engraving on a piece of brass 20mm wide and I don`t have a steady enough hand. I spoke to my friend and colleague at school who is an Art teacher and he said he had a hand engraver for something he does on wood but he hadn`t ever done metal but was willing to have a go. I left it with him and it came back yesterday!!
So I have done everything with the metal but I take no credit for the engraving – all thanks to Mr Dolan!
Top section is my initials CR and the latitude:
Graph is on the bottom section:
He couldn`t help doing something on the normally blank back! I like it a lot!
Removed the layout black and gave it a polish:
Then started to bend it around a former:
Got stuck because I couldn`t bend it, posted a message here on madmodder and after taking advice given, primarly annealing all was well :nrocks:
Silver soldered the two ends together. I`m still a bit messy with my silver solder, I think I still put a little too much on but I`m getting better.
Layed out for the top hanging bracket:
And that is a far as a I got this evening, here is a dry pose!
I think it is going to work quite well. I need to give it a really good polish up and then start to assemble the parts!
Very apt that on the sunniest day of the year here in Manchester, perhaps even of the last few years, glorious sun and blue sky without a cloud in the sky all day long, I finished my sundial…..well near enough to test it out.
I first drilled and tapped the ring for the hanger
It is held by two little cheese head 10BA screws:
I soldered up the little ring holding stub on the top. I must admit, it went pretty dirty looking….I need some citric acid for pickling asap.
After a little polishing, more needed, it looks good. I don`t know if my friend knew the position of the gnomon hole but it fits perfectly below the engraving!
The following photo is well out of focus but it shows how clear the “sun spot” appears on the scale!
And here it is working, it was getting late so the sun wasn`t at its best still very clear to read:
The date is July 3 – therefore we are in Cancer which is the very first column. The time relates to around 6:15pm.
The time was 7:15pm and the dial was reading about 6:15pm ….I really presume this is OK as we are currently in british summer time, hence an hour in front of GMT. I`m very impressed with it!
It needs some elbow grease now to polish it up and then a chain!