Woman killed by tow ball in failed snatch in WA... When will people learn!

[BigDog816 Senior Member Find all posts View Profile Close BigDog816]

I recently attended a First Aid Course at work and there were some changes to the CPR part to make it easier (advised your no longer required to do EAR as part of CPR) this goes against what I've been taught in every first aid course since I was a teenager, we were told then that there is no point pumping blood around the body if there is no oxygen in it, I asked the instructer about this and he said "they've done research" this didn't convince me, to me it seems to be about making it easier, not more effective. Thing that concerns me is not the treatment I would give to someone, but the treatment I would recieve. I'm still trying to find the research that this is based on.

My point being, I would like to see a video of a failure, chain, nothing, standard damper (If that video is one of the links above, I'll check it out at a later time but can't view from this computer). I agree that a normal damper would do nothing to slow down a towball, but wouldn't the towball just come free anyway?

I'm not against a new idea, especially when it comes to safety, just want to see the proof/basis for the change.

[BigDog816 Senior Member Find all posts View Profile Close BigDog816]

Hi Guys, In the interest of safety and for the inexperienced, I thought I would post this link up.
It seems to me that in the light of the recent deaths by towballs, people are still buying these very deadly items.
If you happen to have bought one like this, please throw away the shackle so that you are not tempted to use it.
The seller has been notified and I would urge others to do the same.
regards Rod.
http://www.ebay.com.au/itm/RECOVERY-...item27bcece022
This is what I'm talking about.
The equipment may be fine, but the ""TOWBALL SAFE "" shackle in my opinion is DEADLY and should never be used to hook a snatch strap to a towball.

I agree that this product is incredibly dangerous in the way it's advertised. But is it meant to be used by removing the tow hitch and pin and connecting it by putting the pin of the shackle through the pin hole in the tow hitch reciever (hope that makes sense), as opposed to how most people would assume it is to be used, hooking it over the tow ball.

Just my thought's based on the shape of it, wider at the bottom where the pin is secured - I don't think it would fit over my tow ball?

Again, I believe the advertising is dangerous and misleading.

[MidLifeCrisis Out of control poster! Find all posts View Profile Close MidLifeCrisis]

HI AJ

By fitting chains over or to the snatch strap aren't we just swapping one weight (towball) for another (chain)?

This may sound strange but I actually thought there was no 'real' danger from the strap even though it is going very fast. I thought it had something to do with the fact that energy contained within the strap is even over its entire length and is dissipated over its length as the fibres contract. Momentum is mass x velocity.

So if you attach it to a towball and the ball breaks then the mass of the towball doesnt change over its projectory and keeps travelling at the same speed mainly slowing due to gravity. However in the case of the strap its mass is even over the whole strap so it loses moment rapidly.

Wish I had paid attention in physics instead of chatting to the goth chick.

Is there a link to a strap on its own hurting someone in a vehicle in which case I will happily learn something and not regret the goth chick.

cheers

darren

ps I think I just remembered the analogy used to describe this. Say I have a woollen blanket that weighs 1kg. If I fired it at you say with a catapult and it was doing say 60km/h then even though it may hit you and weighs a kilo you wont get hurt because the mass is spread out over a large area and the fibres spread out releasing the momentum with each strand. Now if I was to get the blanket and roll it in a ball and tie it with twine and fire it it would hurt you because the mass is confined and cant release the momentum.

This is why IMO your better off forgetting the flash looking air brakes and just carry an old woollen blanket from vinnies. If you do snap the strap, or a winch cable, the fibres grab the woollen blanket and slow rapidly.

Now I'm so confused that Goth chick is looking smarter than me,..........

[StormyKnight Advanced Member Find all posts View Profile Close StormyKnight]

Just thinking further about the 2 chains using the 1/3rd & 2/3rd spacing concept....

Now lets just work our way through what happens when a towball breaks.....

The ball gains energy very quickly as the strap contracts, but once the strap returns to its normal length, no more energy is added to the ball - this would occur after travelling only about 1/3rd of the length.
The ball has enough energy now to travel basically flat as can be seen from the evidence that this thread was started by....

So to stop or slow the ball we have two options... (note both rely on the fact that the strap is still connected to the ball - it may not be!)

At the 1/3rd mark we need to slow the strap & thus the ball - we can either use wind resistance or a weight which is the same as using a damper or a chain around the strap.

The damper works by being pulled through the air it causes drag - there are a couple of issues with that - 1. it works better the faster its going & 2. its not really a very good aerodynamic brake.
If a chain was used @ the 1/3rd mark, the chain would get some pull from the strap as the towball broke, but if the chain was heavy enough it would be dissipated before the strap would pull again on the chain with the ball.

Now effectively what would happen is that the ball would try & pull the chain & as stated if the chain was perhaps at least 5 times heavier than the ball, the ball would stop pretty quickly & as such be not able to reach the towing vehicle.

Assuming a 1kg towball @ 60km/h....the 5kg chain with the same energy would be running @ 12km/h (Conservation of Momentum Mass1 x Velocity1=Mass2 x Velocity2)

One major flaw in using either of these methods is that the strap has to remain attached to the bit flying through the air - if it doesn't then obviously neither method will stop it.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Stormy, Sorry but that is a bit simplistic. Bear in mind if a snatch strap has a WLL of say 8t it will probably fail well above that but even at 8t each and every fibre has a balanced load of 8t either side of it. Bit of Newton coming out there. When the strap breaks it tries to retract with 8t force at the point of the break because the opposing 8t is no longer opposing it. That is 8,000kg x gravity. Hookes law can be calculated based on the stretch on the strap, the mass of the vehicle being snatched and momentum. Again conservation of energy the momenum of the vehicles will equal the stored energ in the strap. I will think through the physics/applied mathematics and if I can make it look sensible will post here. Either way a quick looksee would indicate that a 5kg towball or shackle etc would be hitting you at 200km/h or so.

[MidLifeCrisis Out of control poster! Find all posts View Profile Close MidLifeCrisis]

I always though there was inertia (stored gravity effect) that activated in the blanket/cover thingy pulling the strap down when a break occurred thereby directing the bad bits downward away from drivers? Having 2 or three improved this? Weighted items therefore being more effective also. Drag or resistence against the item being a minor part only given the seriousness of that stored energy in the strap.

Too hard to draw pretty pictures but you physics freaks should understand what I am trying to say.....

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

I'm not against a new idea, especially when it comes to safety, just want to see the proof/basis for the change.

Do a recovery course, you should see the footage, it is quite compelling.

Either way a quick looksee would indicate that a 5kg towball or shackle etc would be hitting you at 200km/h or so.

That would be around the figures I have been quoted (160km/r +)

No method of dampner would have helped in the above situation as the strap would not have been securely attached to the tow ball.

Once again I don't wan't to debate the pros and cons of different recovery techniques, I am only passing on what is currently being taught in nationally accredited courses. If in doubt, even the slightest doubt about how to go about a recovery then get some good training.

Cheers Andrew

[tassie tiger Advanced Member Find all posts View Profile Close tassie tiger]

Do a recovery course, you should see the footage, it is quite compelling.




Once again I don't wan't to debate the pros and cons of different recovery techniques, I am only passing on what is currently being taught in nationally accredited courses. If in doubt, even the slightest doubt about how to go about a recovery then get some good training.

Cheers Andrew

Hi Andrew

I would still like to see the footage that you are talking about. My experience is a little old now which is why I am interested in anything new. I was a full time driver trainer for six years and rewrote the 4wd and recovery course for a Commonwealth agency (ended in 2002). Until this thread I have been unaware of any issues with the strap being a danger in itself, only objects attached to it.

I understand your argument that a recovery point may come loose however if the shackles and recovery point are rated higher than the break point on the strap then the strap is the fuse.

Keep in mind that an "accredited course' may mean a few different things. If it refers to one that has been approved by the national training information service (or its new replacement) that the accreditation is in relation to the actual training system employed. They are not experts in the subject matter and would in reality not know the difference between high and low range. That is not their role.

If its accredited by an association then it simply means that that association approves of the training delivered. It is correct in their opinion.

Nice chatting.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Let's say that a strap is attached to the recovery vehicle by a shackle and the recovery vehicle attachment point fails, similar to the towball example, and the failure is at maximum stretch of the snatch strap. A 9m long strap will stretch 20 ~ 30% and is rated at around 8,000kg. At the point just before the failure if the stuck vehicle hasn't moved and the recovery vehicle cannot go further then the momentum of the recovery vehicle is stored in the elasticity of the the strap. So the kinetic energy of the recovery vehicle equals the strain energy in the strap. 1/2 * m (vehicle mass say 2,500kg) * v (velocity in m/s; 10kph or 2.8m/s) squared equals 1/2 P (force applied to the strap) * x (extension of the strap; 20% of 9m = 1.8m). 0.5 * 2500 * 2.8 * 2.8 = 9,800 kg m/s = 1/2 * P * 1.8 so the force in the strap is 10.9t so not too rough in the way of assumptions. At the point of breakage we now have the strain energy applying its energy to the shackle. Let's call the shackle 2kg (6.5t shackle) and the weight of the strap 5kg. There would be some internal resistance in the strap so I will cut the energy by 20% which I think is extremely conservative. So 80% * 9,800 kg m/s = 1/2 * (2 + 5) * v squared. This gives v = 47.3m/s. 170 km/h!!!! Ummm can a D4D go that fast? I think that the internal resistance of the strap would only account for maybe 5% loss of energy and redo the calc and 200 kph is the result. Caution people. There of course will be some reduction through wind resistance and hitting people. Ooops.

TT my snatch strap is rated at 8,000kg, my equiliser strap is rated at 8,000kg. I use two 3.25t shackles on the equiliser strap and a 4.5t shackle on the recovery hitch. All WLL ratings. Anything could let go. Probably the strap since shackles are so conservatively rated and each use of a strap (and age and UV) will weaken the strap. By the way by my calculating the pin that holds the recovery hitch into the towbar will shear at about 12t.

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

...there is no point pumping blood around the body if there is no oxygen in it... I'm still trying to find the research that this is based on.

Bigdog,
I think they are thinking that just the act of pumping forces air into the lungs. I did hear the research at the time, and I think they found a 15% improvement in outcomes using the new guidelines. I assume this is because those unfamiliar with the technique find it simpler to do. I also note that the American Red cross still say that you are better to include breaths if you "know what you are doing"

Cheers

[the ferret Junior Member Find all posts View Profile Close the ferret]

I agree that this product is incredibly dangerous in the way it's advertised. But is it meant to be used by removing the tow hitch and pin and connecting it by putting the pin of the shackle through the pin hole in the tow hitch reciever (hope that makes sense), as opposed to how most people would assume it is to be used, hooking it over the tow ball.

Just my thought's based on the shape of it, wider at the bottom where the pin is secured - I don't think it would fit over my tow ball?

Again, I believe the advertising is dangerous and misleading.

It's called "towball safe" because it's designed to fit around the throat of the towball and not come off.
I am sure that that would be the case, however I for one would not like to be hit by a towball &
shackle combined.
The tongue of the towbar is not a rated recovery point, in fact a person died recently because the tongue broke at the weld at the box section on a genuine Toyota towbar.
Fitting the shackle to the tongue would cause the pin to bend and possibly snap or pull out of it's thread because the load would not be distributed over the length of the pin.
Please don't use this method.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

To me the really scary part is that even with all the correct "rated" shackles, recovery points, dampners and "matched" snatch strap rating to size of the stuck vehicle, Murphy's Law can still bite you.

Have seen a rated recovery point, attached to a rated shackle, tear out of the sub frame, clip the bull bar (and break its mounts) then still manage to whistle past the front doors of the other vehicle with dampners flapping as the strap became a kite tail.

Yes, a lot of the kinetic energy was "gone" but it still would have caused a lot of pain if it struck some one.
Fortunately we had everyone well clear of the attempted recovery so no one was hurt ... just a whole lot of that famous Graham Kennedy crow call .... farrrrrck

So even with doing everything "right" it can still go very wrong, so if or rather when doing a snatch recovery be damn sure every one is clear and paying close attention to whats happpening.

Lee
oh yeah the vehicle was less than 12 months old and in excellent condition so not a rusty sub frame

[tassie tiger Advanced Member Find all posts View Profile Close tassie tiger]

The best thing to take out of the whole discussion is a snatch strap is not a replacement for a winch. In six years of training we never snapped a snatch strap.

See you in the bush. With a helmet on

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

This is why I've also been carrying an 8m length of rated chain for years with hooks on the ends so you can hook it over itself when going to the beach etc, as well as a snatch strap. The chain's for pulling out softroaders (gently and respectfully of course) fitted with tie down points only and also for cars with tow balls and no "real" recovery points (usually backpacker hired troopies). A chain eliminates risk and is totally safe. With straps you see a few people choosing to slingshot cars out of bogs at fighter jet take-off speed from the 1st snatch attempt. I've never liked that idea. I've always just rolled the car forward until the strap tightens, and then given a little acceleration. If that doesn't work, then repeat the process but with a slow rolling start and so forth until the 3rd or so attempt until you get them out doing it slightly harder each time. It's much easier on the strap and recovery points, as well as the chassis/bash plates if a car's bottomed out in a bog hole. I use 4.7 tonne rated shackles for the snatch strap so the shackles will never break I know that. But like always, I opt to do pushouts first and foremost with simple man power as it's almost always quicker and easier and there's no risk.

But there was this one time we were first on the scene (3 car convoy) to 3 members of an Indian family (mum, dad and baby) who were bogged on an inland track on Fraser Island in a heavily laden softroader that was bottoming out (Feb 2010). They were facing downhill slightly and bogged their car pretty well. We tried pushing them out which proved difficult but got them out eventually only so he could then get stuck 10 meters later. The track was narrow so I couldn't drive around him either. He obviously had no recovery points and no tie down point that we could see at the rear. He had a tow ball that I refused to snatch off (because I annoyingly forgot my chain for this trip - not that it would've helped in this scenario much with uphill recovery in soft sand). Then the arrogant cavalry rocked up. They had approx 10 to 12 high lifted Patrols, Lancruisers and Suzuki's I think, most with their 4x4 Club stickers on the windscreens that I better not name, but starts with a "K" for those that are curious. Some members of this group were unprovokingly racial towards the Indian family and told them to piss off home & leave the country and so forth. Others were abusive towards me because I wouldn't snatch off the tow ball because I didn't trust it 100% so their group wouldn't be held up for 5 mins. Anyway, after repeated failed attempts we all managed to push the car out. They got stuck again a little bit further down the track where I could then just pass with inches to spare and hook the strap up to a tie down point on the front to tow them slowly for another km approx to bitumen at Eurong. All the while horns beeping in the background from the 4wd club members and them yelling out abuse the whole time. Once we could pull over and let them past some held their hands on the horns, yelled at us, swore at us and one car even through rubbish which I picked-up and binned afterwards. All because I refused to snatch off the tow ball. So even when under pressure from an angry mob, I still wouldn't use a snatch strap over the tow ball of a car in front.

[letsgoplaces Advanced Member Find all posts View Profile Close letsgoplaces]

Well done Brett. I take it none of the knobhead 4wd club (you said it started with k) offered to snatch backwards?
It's guys like that.....