Page 17 - May June 2012

together. I drilled these holes out so that they were just big enough to take T-nuts for the 10 mm studding.
T-nut, mending plate and divider parts
The first helix – a learning process
The main helix sections were cut in a similar way to the above, the only difference being that these were marked out across the width of the sheet rather than in pairs lengthways on the sheet.
Top of sheet along with parts of homemade trammel
This resulted in a small triangle of timber missing at each outside joint, but did cut down the amount of waste timber overall. The missing part was not going to have much impact and will eventually be hidden under the fascia.
Missing ‘V’
Currently, each turn of the helix is made up of:
• four sections of half-inch (12mm) ply;
• eight pieces of 3⁄4" × 3" timber cut 31⁄2" long but with the ends
cut at the angle of the incline so they stand vertical;
• 16 pieces of 3⁄4” × 11⁄2” also cut 31⁄2” long, also cut with the ends at the incline angle.
Spacer blocks
Also required were the 24 wooden spacers between the base and the first turn of the helix. Again the tops of these were cut to the angle of incline but the bottoms were cut square or perpendicular to the sides. Finally 32 lengths of 10 mm stud- ding are cut to the various lengths required.
All the spacing blocks were drilled on the centre-line at 10.2 mm to 10.5 mm to clear the studding – 10 mm was a little too tight! The 3" wide spacers have two holes at 2" centres to help tie the two ends of each section together. Belt and braces maybe with both dowels and repair plates, but it does mean the joints are supported on both sides equally.
These were drilled using a jig I made from an engineering parallel, some toolmaker’s clamps, and a bench drill.
Drilling jig set-up
As I did not want a board join where the track went from zero elevation to the start of the climb, I cut the first section of the helix to include the lead-in from the storage yard, as can be seen in photo 1. This shows the one waiting for the construction of the main helix. This means that the first piece is in length, the total width of the helix. A similar piece will be cut for the
6
3
4
7
5
8
june 2012 17