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It's breaking Strain. Breaking Strain of standard wire rope supplied on most 9000lb winches is only just over 10,000lb. Recovery winch specifications do not follow Australian Standard lifting regulations so you should not try to compare them.Quote:
Originally Posted by Tank
Ian
Ian, every winch for sale in Australia (for 4wders) shows the BS of the rope and advertise the winch at that capacity.
It doesn't make any difference whether the rope (wire cable and plasma) is used for lifting or drag winching, all ropes have a Guaranteed Breaking Strain (GBS) and if you work a cable or rope to it's GBS then you are courting disaster. Every time you use a winch rope you are degrading it's strength, that's why in the Rigging industry or any industry using cables there is a built in Safety Factor (SF).
A 10mm winch rope, which has 7 strands would have a GBS around 12000lbs with a SWL or WLL of 2400lbs.
Where do you get the figures for the GBS of a 9000lb winch rope lifting or dragging ability (Strength) is governed by wire/rope dia. and construction, I've seen 7 and 8mm ropes on a winch that was labelled 9000lb capacity.
You need to remember that the size and construction of the cable/rope on a winch determines the capacity, no winch should be rated at the GBS of the cable, it should be rated at the WLL or SWL of the rope/cable, same as rated shackles, Regards Frank.
Hi Frank,Quote:
Originally Posted by Tank
You are absolutely correct - Winch cables should be rated with a SWL or WLL much higher than the rated capacity of the winch.
However ......
This is not the case. Most 9000lb winches sold for our 4WD recovery duties will have 7mm or 8mm wire rope supplied with the winch. Bullivants catalog suggests that these ropes have MBS (Minimum Breaking Strain) of ~8,300lbf and 10,600lbf respectively.
These cables barely match the advertised load expectation of the winch. If you're lucky, the cable won't break before the winch stalls.
I'd much rather have 13,000lb (~6,000Kgf) Breaking Strain synthetic rope on the front of my vehicle than the regularly supplied, significantly lower BS, significantly more dangerous when it does break, steel cable.
Ian
Ian, winches are rated by the SWL or WLL of the cable or they are supposed to be, for instance if you spooled 7MM wire onto a winch drum on a crane with say a SWL of 25 tonne then the fact that the winch will certainly lift/pull 25 Tonne with it's correct cable, it is now reduced to only being able to lift/work to the limits of the 7mm rope and of course vice versa a 25 Tonne SWL cable would not increase a 9000lbs winch SWL, because it would be impossible to fit to the winch.
We have to get away from the GBS/MBS of a cable or rope mindset if you have the BS in your head when doing a recovery you will be expecting too much from your rope/cable. I am a retired rigger/mechanic and in the 20++ years of professional rigging I have never broken a cable, nor have I ever damged or broken any of my recovery gear over that same period. Yet every week there is a sad tale of people breaking cables/rope and they seem to think it's normal. If we work our recovery gear to it's SWL/WLL then there should not be a problem, think SWL/WLL not GBS/MBS, Regards Frank.
That's your problem Frank - I'm not saying it's a bad problem, and I had already deduced this from your previous posts! Your attitude to safety has to be commended.Quote:
Originally Posted by Tank
However .....
If I were to put a winch on the front of my 4WD rated at 9000lb, and cable with a SF of say 5, I would need to spool it with 15mm dia wire rope weighing over 1Kg per meter, and I would have to spool it on a drum dia of 300mm.
The size alone would make it totally impractical on anything smaller than a Unimog, and then the winch wouldn't be man enough!
Unfortunately, we in the 4WD fraternity have to be content with recovery winches that have drums smaller than optimum and cables rated close to their BS. This is one of the reasons why all the training for winch recovery prepares us for the possibility (probability) of a broken cable - and another reason why it is much safer to have synthetic rope out there than steel.
The alternative is to re-rate all the winches on the average 4WD's out there to 2000 - 2500lb and not be able to recover anything much!
You'll have to learn to leave your riggers hat off, but don't throw it away - keep it in the glovebox!
Ian