Calculating load on a speedline.

[Mark Wileman]

hey,

how would go about calculating the load on a speedline? Its somewhere inbetween a snatch (worst case 11 x load) and a dynamic standard rigging setup (3 x load).

I've been watching some August hinkie videos and he speedlines some serious weight. Zoom to the last 1/4 of the video and you see him chunking down easily 3-400 kg sections.

Is there a HSE backed equation for speedline loads?

 

 

I passed my CS41 today so naturally the next step is speed lining 1/2 a ton of timber over someone's house

[Ian Clarke]

I'm not sure if the answer but don't forget the way you attach the rope to the tree will affect the breaking strain of the rope.

[TheHungrySquirrel]

Also figure in side load on the stem your anchoring it to

[Mark Wileman]

10 hours ago, Ian Clarke said:

I'm not sure if the answer but don't forget the way you attach the rope to the tree will affect the breaking strain of the rope.

Does a timber or cow hitch put less strain on the rope than a running bowline? I assume because of the smoother bend ratios on the hitches?

[Ian Clarke]

2 hours ago, Mark Wileman said:

Does a timber or cow hitch put less strain on the rope than a running bowline? I assume because of the smoother bend ratios on the hitches?

Let me check I've got some books I need to check to get exact numbers. I'll also link some videos for more info. But I am not sure if you will get an exact answer other than testing it yourself and recording the readings.

[Mark Bolam]

There isn't much point in any of this unless you know the exact breaking strain of the tree.

[Ian Clarke]

if you can get a copy of The art and science of practical rigging.  its published by the isa that will have some good information in there one of the bits it does say is that pieces of timber should not be dropped on to a tensioned line. they should be first arrested in a normal rigging point below system then. the speed line tensioned and then they travel down the line.

[Ian Clarke]

 this is a good video for some information.

[Ian Clarke]

and then here is a video just to show what is possible.

 

 

[macklift1]

Just remember we most frequently use deflection loads to help pull trees over, look at it as a last resort.