The only drawing I have Mike is a poor one and subject to copyright, so it wouldn't be much use to post it.Quote:
Originally Posted by mike_ie
RELEVANT POINTS IN CONSTRUCTING A PICKET HOLDFAST
1. Three star pickets are driven into the ground as close as possible to each other (touching) at an angle of about 45deg. pointing away from the car. The vee-face of the pickets faces the car, so as to maximise the grip in the soil i.e. harder to pull through the ground. The pickets must be at least 1200mm long and buried for 2/3 of their length.
2. About 1m away and directly in line with the direction of pull, two pickets are driven in and the same process is repeated for the last picket. All must slope away from the car and be perfectly in line.
3. A 16mm sisal rope 12m long (in perfect condition) is then tied near to the top of the group of 3 pickets with a clove hitch (we protect the rope from the pickets by wrapping a sandbag around the pickets first). The rope is then passed down to the base of the group of 2 pickets (suitably protected) and returned back to the top of the group of 3. This is repeated until four turns have been completed; an assistant is handy here to keep the turns tight and stop them falling out of place.
4. When the four turns have been done, the excess rope is wound round-and-round (frapping) the turns from the top of the group of 3; the assistant is invaluable for making the frapping quick and easy. The frapping is tied-off with a clove hitch about the turns.
5. The process is repeated with another rope from the group of 2, down to the single picket.
6. The chain or recovery strap is attached to the base of the group of 3 pickets. When the load comes on, watch the base of the pickets for any excessive movement and stop winching if they appear to be losing their grip. I have never had one come loose and a cobber of mine told me that he winched a bogged Land Loser out of a salt lake using this type of holdfast!
7. Star pickets are near to impossible to remove without mechanical assistance, so a simple cam-action device that grips the base of each picket works every time with a hi-lift jack.
SAFETY
1. All ropes; shackles and slings etc. must be rated and in good condition. Natural fibre ropes should not feel soft to the touch and should not smell mouldy - if they are don't use them, because if they break someone will die! Similarly synthetic ropes must be rated and protected from heat; chemicals and sharp edges as with a natural fibre rope.
2. Keep bystanders 1 1/2 cable lengths away from the recovery, in case the rope or hardware breaks.
Cheers Charlie
