Derrick drawbridge
Equipment
- 4 x 10m (30ft) 10mm diameter ropes for guys
- 2 x 3m (10ft) 15mm diameter ropes
- 3 x 7m (20ft) 10mm diameter ropes
- 40 light lines
- 1 x 5m (15ft) spar
- 4 x 3m (10ft) spars
- 20 x 0.6m (2ft) spars
- 2 single pulleys
- 4 large pegs
- mallet
Method
Tie one end of each of the 4 x 10m (30ft) ropes to the top of the 5m (15ft) spar as guys.
Using the 2 x 3m (10ft) ropes attach the two pulleys to the top of this spar just below the guys.
Construct 2 ladders using 2 x 3m (10ft) and 10 x 0.6m (2ft) spars.
Thread (reave) one 7m (20ft) rope through each pulley, temporarily tying the ends together so that the ropes do not escape when the spar is raised.
Stand the 5m (15ft) spar vertically in the middle of the river and peg out the 4 guys as before.
The Scout whose turn it is to get wet this time, stands in the middle of the river and, using the remaining 7m (20ft) ropes, attaches the ends of the ladders to the spar. We again suggest that you use a ladder sling and attach the ropes to the vertical spar with a clove hitch or rolling hitch.
Finally make off one end of the rope through each pulley to the outside end of either ladder.
When the bridge is not in use the ladders can be raised to prevent unauthorized access.
Note: Since the design of the project the principles of Health and Safety have changed dramatically.
Caution should be exercised to assess the risks associated with this build and especially regarding possible falls from height, so handrails or belays and harnesses may be required.
To download the complete plan and design document please Click Here
