Having a valid answer for this or similar questions really bugged me for a long time. I reckon it is a fair question and even though you know you shouldn't, what are some "common sense" answers that let you go away feeling comfortable about
why you shouldn't?
For me it started when being told at a club training day that I could not pull off the mount points on my ARB bar on my Rodeo. They looked like that's what they were made for!! The follow on was that it wasn't up for discussion or explanation, just that they're not made for it and that's it. Let me not go off topic, but just say that's where the similar thoughts started and it really bugged me that no one wanted to give me some reasonable technical or at least common sense technical level answer.
Coming back to the topic of the towball I think much of the issue is directly related to the quote on Growler's signature: "WARNING: TOWBALLS USED WITH
SNATCHSTRAPS DO KILL!!"
I'm not saying the snatchstrap is the only problem with towball recoveries, but I think it is where the major issues start and most of the examples will be. I'm not a great fan of snatch straps simply because they can be so easily misused.
With an 8000kg snatch strap (the lighter rating size) it is difficult to tell how much force will actually be applied between the two vehicles. If the pulling truck is in low first and driven off slowly but constantly with the other truck lightly stuck and only 1-2 metres of slack, then the force won't be too much. But in real life the guy who is stuck is up to his bonnet in mud, has a heap of gear in the car (equal to lots of weight) and the bar of his car is nudged up against a hard edge coming out of the bog hole. In no time at all to have any chance of getting him out with a snatch strap it can escalate to a dangerous place. How much force is being put on now? These are the "youtube" ones where you see them run at top speed with 4 or 5 metres + of slack. All that energy goes into the stretched strap and it has to go somewhere. You can easily imagine now that the 8000kg strap is still going to stand up to much more than the 3500kg tow ball. You can also easily start to imagine that the force could be in excess of the 3500kg rating of the towball. Something has to give, hopefully the stuck vehicle, but otherwise it is going to be the next weakest link, which is probably the towball (or a poor recovery point).
This all ties in perfectly when you look at the forces required based on twisty's post, for the extra forces, etc.
To me this is a common sense starting point that lets me start to understand "
why" we shouldn't do it.
There are some great background points in this ARB article (things like forces involved, not being able to control the use of a product, etc.):
http://www.arb.com.au/getting-starte...ery_points.php
(I think this article was originally in the ARB Spring 2011 Newsletter as well, which is where I originally noticed it)
Coming back to the original question about the towball vs the shackle (quote from the article):
"Thankfully, there are standards for the shackles we all use to attach straps, however their rating system is based on lifting gear standards, and the safety factors in lifting gear mean that the rating is one fifth of the failure point."
So, going from this the common 4.75T (4750kg) shackle we usually see and use is not meant to break (as a safety factor) until it has 5 x 4.75 = 23.75T.
Do you think you'd have the same 5 x factor on the 3.5T towball? I really doubt it. Do you think you'd have the same 5 x factor on the 8000kg snatch strap? I'm sure it isn't. (there was a 4wd action article where they tested various brand staps until they broke, but I can't find it just now to see what rough factor it was - would love it if anyone had a reference to that?)
So, at least for me, that gives me a comfortable, "common sense" answer as to why not the towball when we use shackles in many situations with recoveries.
Final comment: Any solid object used in a recovery can easily end up being a deadly "missile" - including shackles. Minimize their use, never join straps with them and always hook to a solid rated recovery point (rated points is a whole other topic, but I'll leave that to TD and other experts). You can use a good shackle on a good strap and hook it to a tie down point which will break and easily still kill someone with no towball involved.
Sorry for the long answer, but hope some of this makes sense to answer the actual question.
Originally Posted by cgm
Having a valid answer for this or similar questions really bugged me for a long time. I reckon it is a fair question and even though you know you shouldn't, what are some "common sense" answers that let you go away feeling comfortable about why you shouldn't?
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