Tow Tongue Problem!!!

Submitted: Friday, Nov 22, 2013 at 22:33
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G'day, was towing my empty 7x5 trailer the other day and got hit from behind, not much damage at all, a scuff mark on the tail gate, bent number plate bracket and broken number plate light. Wasn't until the next day, before setting out I checked the hitch as you do, found the recently bought tow tongue had bent about 45 degrees from the horizontal.......... Any one ever seen or heard of this happening? Have contacted the importer and he basically doesn't want to know about it.


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Reply By: Ron N - Friday, Nov 22, 2013 at 23:02

Friday, Nov 22, 2013 at 23:02
John - Well, if you got hit from behind, did you get the other drivers details and report the accident?
If you didn't, you'd better do so now, so you can make an insurance claim and get the damage repaired.

I'd be checking the whole towbar, the entire unit may need replacing - and there may be chassis damage as well. It's not unusual to have torn bolt holes in the chassis after a rear impact - and one that bent the tow tongue like that, wasn't a gentle bump.

I can't see why you'd want to contact the importer, unless you were figuring on paying for all the repairs yourself.

Cheers, Ron.
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Follow Up By: Member - John - Friday, Nov 22, 2013 at 23:15

Friday, Nov 22, 2013 at 23:15
Ron, hi, the bump was hardly felt, my partner didn't even feel the contact. I looked at damage and told the other bloke no problems. The towbar and everything else is ok. I contacted the importer to let him know he may have a serious problem with sub standard tow tongues.
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Follow Up By: Ron N - Friday, Nov 22, 2013 at 23:42

Friday, Nov 22, 2013 at 23:42
John, I don't think you've got a sub-standard tongue, it's the way it was hit, and the size of the impact, that has bent it.

The tongue would be designed to withstand about double the hitch weight before it would start to bend, and I'll wager even a small impact would be several tonnes of pressure.
I certainly wouldn't want my fingers/leg/hand in there, that's for sure!

Even if the weight of your van is 3 tonnes, the hitch never has to cope with that amount of weight.
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Follow Up By: Member - John - Friday, Nov 22, 2013 at 23:49

Friday, Nov 22, 2013 at 23:49
Ron, the size of the impact was not great, the tailgate had a scuff mark on it and a bent number plate bracket. Maybe the tow tongue is designed to bend, so why didn't the importer tell me that when I rang him?
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Reply By: Ross M - Friday, Nov 22, 2013 at 23:18

Friday, Nov 22, 2013 at 23:18
The tow tongue has successfully absorbed the bump energy as it deformed/bent.
The weakest link always fails first.
If that is the only real damage then I think you are very fortunate and will possibly buy a Tattslotto ticket along with the new tongue.

I notice only one chain, so no chance of a crossover to catch a wayward trailer and keep it sort of under control. Chains too slack isn't a good situation to have.
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Follow Up By: Member - John - Friday, Nov 22, 2013 at 23:32

Friday, Nov 22, 2013 at 23:32
Ross, Hi, agree about the single chain, that is soon to be fixed. The bump was not sufficient to deform the tailgate, only a scuff mark. I would not have expected the tow tongue to deform as it did for such a minor contact. Thank you for your reply.
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Reply By: Michael ( Moss Vale NSW) - Saturday, Nov 23, 2013 at 06:14

Saturday, Nov 23, 2013 at 06:14
John, about 2 years back here on EO, a similar complaint about a small bump and his Reese tongue was bent. They wanted to swap with a new one but his main problem was why it was so soft. Obviously imported recycled steel. Michael
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Follow Up By: Ron N - Saturday, Nov 23, 2013 at 12:46

Saturday, Nov 23, 2013 at 12:46
Michael, that comment about "imported recycled steel" is ill-informed and unwarranted, and shows that you know little about steel and steel qualities.

1. China is the largest producer of finished steel in the world (700M tonnes annually). China has been a net exporter of steel since 2006.

2. China supplies steel to every developed nation in the world, including America.
China produce nearly 90% of its steel from iron ore, using mostly West Australian iron ore.

The reason China uses iron ore, is that China uses coking-coal-fired blast furnaces - the traditional steel-making method - because China does not have enough spare electricity generation ability, to be able to install the more modern electric arc furnaces, as America has done.

America now uses electric arc furnaces almost exclusively, because they can handle scrap better, are faster, and can produce small batches of precise-specification steel to order in vastly quicker times than blast furnaces.

The American steel industry now runs almost completely on scrap steel and electric arc furnaces. They use very little iron ore, because their ore is low grade taconite and requires costly processing.
They used up nearly all their high grade hematite during WW2, producing armaments and war equipment.

3. Steel quality is not reduced by using scrap steel as feed!! Scrap steel actually IMPROVES finished steel quality.
A percentage of scrap is fed into nearly every blast-furnace load to improve the final steel quality.
Electric-arc furnaces run exclusively on scrap steel.

Scrap steel is a KNOWN quality, because it has been previously refined and undesirable steel contaminants (such as phosphorus, sulphur, ilmenite, etc) have been REMOVED in the previous refining.

Every time steel is re-refined, its quality improves FURTHER.

Caterpillar used to use up to 30% scrap steel in every blast-furnace load, and did so since the days of Caterpillars predecessor, Holt. Caterpillar now use around 90% scrap steel. No-one ever says Caterpillar steel is rubbish.

4. No manufacturer in Australia, utilising Chinese MILD STEEL, has ever issued a statement about overall Chinese mild steel quality, being sub-standard.

5. A towbar tongue is made from MILD STEEL - not low alloy or high strength steel - which is used for axle steel.

Mild steel is the most common and widely-used form of steel. It's a low carbon steel, has virtually no heat-treatability - and it's used because it is easy to work with, and is strong enough for all general-purpose requirements.

Mild steel has LOW TENSILE STRENGTH. It's easily bent. Towbars and towbar tongues do not require the use of high-tensile steel.

6. Australian Design Rules (ADR) 62/00 and 62/01 cover the strength requirements, and testing requirements for towbars and towbar tongues.

http://www.transport.wa.gov.au/mediaFiles/licensing/lbu_vs_ci_116.pdf

A towbar has to be able to withstand 0.5 times the towbars capacity in vertical tension and compression, and transverse thrust, without deformation.
It has to be able to withstand 1.5 time the towbars capacity in longitudinal tension and compression without deformation.

7. A Daihatsu Charade, weighing just over a tonne, running into the back of a stationary truck weighing 3.5 tonnes, at 48kmh, generates an impact force of 181 kN (40,690lbs or 18,456kgs).

http://www.underridenetwork.org/SafetyArticles/EstimatingForcesDuringCollision.aspx

Even with a much lower impact speed, impact forces of even a small car on a stationary vehicle, are in seriously larger numbers than even a well-designed and well-constructed towbar and tongue can cope with, without serious deformation.

I hope this sets the record straight.

Cheers, Ron.
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Follow Up By: Ross M - Saturday, Nov 23, 2013 at 14:02

Saturday, Nov 23, 2013 at 14:02
Ron
Despite the above info which would largely be the case, there is a lot of steel which comes from NZ but originates from China and it HAS got hard and soft spots in it.

Some you can drill extremely easily and 50mm away on the same section IT will blunt the drill or is VERY hard to drill, grind, shape and bend.

Some 50mm Gal pipe via the same route of supply is impossible to bend in a pipe bender. Well it does bend but kinks every time at around 40 degrees. Many steel steel fabricators will tell you their trouble with it.

No one rule covers it all from China.

Tow bars are made to a price too.
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Follow Up By: Michael ( Moss Vale NSW) - Saturday, Nov 23, 2013 at 20:03

Saturday, Nov 23, 2013 at 20:03
Don't waste your breath Ross! Michael
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Follow Up By: Michael ( Moss Vale NSW) - Saturday, Nov 23, 2013 at 20:12

Saturday, Nov 23, 2013 at 20:12
At least the tongue took the major percentage of the impact. Even if the tow bar is slightly deformed, the tongue has saved torn bolt holes and other body damage! Michael
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Reply By: Lyn W3 - Saturday, Nov 23, 2013 at 06:19

Saturday, Nov 23, 2013 at 06:19
My question would be, is the tongue rated to be used that way, only specifically designed tongues can be used this way.

Bit hard to blame the tongue if this is the case.
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Follow Up By: KevinE - Saturday, Nov 23, 2013 at 11:07

Saturday, Nov 23, 2013 at 11:07
I agree with Lyn,

The tongue seems to be mounted upside down?

I have a heavy duty tongue that can be used upside down, but it has reinforcing welded across the bend at 90 degrees. That tongue doesn't seem to have any reinforcing?

I have seen the same thing happen where a camper trailer was towed across a creek crossing with a very steep egress; once the car was up on the bank & the trailer was on the steep bit, the tow-bar tongue bent like that, only that tongue was on right side up, so it bent downwards. Their mistake was using a tow ball instead of an off road hitch.

Tow bar tongues aren't made to support lots of downward (or in this case, upward) stress.

Just my .002 ;=)
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Follow Up By: Slow one - Saturday, Nov 23, 2013 at 11:34

Saturday, Nov 23, 2013 at 11:34
Lyn and Kev,

Being a Hayman Reese Tongue there will be a derating sticker on it for when it is inverted. If it doesn't have a sticker, then it can be used both ways with no loss of strength.
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Follow Up By: olcoolone - Saturday, Nov 23, 2013 at 11:41

Saturday, Nov 23, 2013 at 11:41
Tongues can be used both ways as the force is equal and the amount of leverage force the towbar has to withstand is only going to be a maximum of 350kg (ball weight).

What happened is the towbar tongue was used in a way it was never intended to be used and the leverage ratio from being hit from behind was greater that the design leverage ratio.
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Follow Up By: Lyn W3 - Saturday, Nov 23, 2013 at 13:48

Saturday, Nov 23, 2013 at 13:48
The Reese Co. in the USA has specific ratings for "Up Rated" tow tongues and are generally made of solid stock or one piece forged steel or aluminium. I would say that less than 25% of their range is "Up Rated"
I would also presume that most of their stock is made in the same Chinese factory as Hayman-Reese products.
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Follow Up By: disco driver - Saturday, Nov 23, 2013 at 19:49

Saturday, Nov 23, 2013 at 19:49
If one left clicks on the photo, it enlarges it and you can see that the writing on the tongue is the correct way up as it is, in the square tube receiver.
AFAIK no labels are designed to be read upside down when installed.
It should be perfectly safe either way up.

Disco.
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Follow Up By: Member - John - Saturday, Nov 23, 2013 at 21:02

Saturday, Nov 23, 2013 at 21:02
Lyn W3, the tow tongue can be used both ways, it is listed as 3 1/4" drop, 2" rise.
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Reply By: Erad - Saturday, Nov 23, 2013 at 07:00

Saturday, Nov 23, 2013 at 07:00
The towbar is certainly bent. Whilst you could probably get it straightened out, I would say that it is not worth the risk. The consequences of having a trailer coming loose and crashing into something or someone are too dire.

The first thing I would do is throw away the towball. It has obviously had a major impact.

I had a Commodore run into the rear of my NL Pajero. I had stopped at traffic lights and because I didn't have mmy foot on the brake, the Pajero was heavily shunted forward, causing both fron seat backs to collapse (also causing some whiplash to both my wife and I). Surprisingly, body damage to my Pajero was virtually nil. The Commodore was a different story... The towbar took most of the force of the collision, and whilst it was probably repairable, there was no way I was going to even consider it. Although the towball had not been directly hit, I had a new ball put on as well.
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Follow Up By: Ross M - Saturday, Nov 23, 2013 at 07:28

Saturday, Nov 23, 2013 at 07:28
The obvious bent bit isn't the tow bar, that is under the vehicle.

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Reply By: Member - Tony (ACT) - Saturday, Nov 23, 2013 at 07:36

Saturday, Nov 23, 2013 at 07:36
I tend to agree with the above comment. The tow tongue is designed to have the weight applied in the direction of travel, apart from the reversing aspect you do with vans etc. This also worries me regarding snatching vehicles using the tow tongue, with ball removed.

I would have the tow bar inspected along with the mounting points, get a new tongue and ball, and count your lucky stars it wasn't worse.
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Reply By: Member - Andrew - Saturday, Nov 23, 2013 at 08:13

Saturday, Nov 23, 2013 at 08:13
Hi John
Just some thoughts.
It appears that the bend is right on the stress point as the rest of the tongue is not obviously distorted. Because all the impact force was tranferred through the tow ball then the leverage is putting all the bending force through that point. The damage is consistent with the ball taking all the force and the bend occurring at the most vulnerable place.
The bump may have felt soft but there is still a bit of energy to dissipate and it ended up being concentrated on the towbar tongue. The rest of your damage might be light because the towbar tounge, by bending, absorbed all the force. At least that part is easily replaceable and because it gave way first it prevented damage further in.
Having seen minor bingles that don’t even scratch the paint on plastic bumpers but leaves crumpled stuff behind it I have learnt that it is hard to really work out how hard the hit was by the drivers feel. What I mean is that the way you felt the impact is not always the same as the effect on the vehicle.
Regards
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Follow Up By: Lyn W3 - Saturday, Nov 23, 2013 at 09:27

Saturday, Nov 23, 2013 at 09:27
The fact that the Tregg type hitch is solidly mounted to the Tow Tongue amplifies the leverage on the tongue. If the hitch height was slightly above horizontal with the Tow Tongue mounted upsidedown then all the force of a relatively minor rear collision would be transferred to the weakest part which was the stress point which Andrew described.

As I said above if you are going to use a Tow Tongue upside down use one which is designed for the job, These are generally the right angle type with reinforcing such as the genuine Toyota ones.
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Reply By: Robin Miller - Saturday, Nov 23, 2013 at 08:23

Saturday, Nov 23, 2013 at 08:23
Had one in which the drawbar bent before the tongue John.

Back in post 90980 (Broken off stub axle ) was evidence of poor imported steel.
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Reply By: Member - PJR (NSW) - Saturday, Nov 23, 2013 at 09:38

Saturday, Nov 23, 2013 at 09:38
Question a bit OT but what is the fairlead for?

Phil
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Follow Up By: awill4x4 - Saturday, Nov 23, 2013 at 10:50

Saturday, Nov 23, 2013 at 10:50
Johns GU Patrol is really quite a well set up vehicle for touring and he has a winch at both ends of the car.
Regards Andrew.
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Follow Up By: Member - PJR (NSW) - Saturday, Nov 23, 2013 at 10:53

Saturday, Nov 23, 2013 at 10:53
Smart man but where would I put a winch at the back!! I have wondered about it but always stumble with the rear mounting.

Thanks
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Follow Up By: Member - John - Saturday, Nov 23, 2013 at 13:00

Saturday, Nov 23, 2013 at 13:00
G'day, Offroad Division in Caboolture Qld make a rear bar that will take a Warn 9000 lb winch.
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Reply By: pop2jocem - Saturday, Nov 23, 2013 at 12:24

Saturday, Nov 23, 2013 at 12:24
Well guys, not trying to just be argumentative but I agree with John, unless he is understating or underestimating the magnitude of the shunt up the bum his trailer took.
How a piece of what appears to be about 16 mm thick by around 50 mm wide flat bar could be bent over that relatively short distance when you take into account the impact was not applied vertically but horizontally would have me questioning the quality of the steel used.
I once tried to straighten the offset in an old tow bar tongue to use the steel for another purpose. A 14 lb sledge hammer and a sizeable block did not make much impression. I got bent out of shape before the tongue.

Cheers
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Follow Up By: Ron N - Saturday, Nov 23, 2013 at 13:57

Saturday, Nov 23, 2013 at 13:57
Pop - Yeah, but they don't make tow bar tongues like they used to! [;-)

Maybe you didn't have a big enough feed of Weeties before you picked up that big spoiler?? LOL

Hint - As an old pro spoiler-wielder from waa-ay back - if you use a block of wood to beat on, the wooden block will absorb 50% of the impact of your blows.

When we used to beat out dozer track pins by hand (God, I'm showing my age now!), we always used to block the track chain solidly against the sprocket by backing up to a big wooden block that locked under the track plate, and then placed a huge lump of solid steel, square up against the rear of the track link.

This meant that any impact by the sledgehammer was transferred 100% to the track pin, without any deflection of the track chain whatsoever.

You'd see blokes grunting and beating on a loose, bouncing track chain for hours, and wondering why they weren't getting any movement in the track pin!

Cheers, Ron.
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Follow Up By: Herbal - Saturday, Nov 23, 2013 at 14:08

Saturday, Nov 23, 2013 at 14:08
Quote - Well guys, not trying to just be argumentative but I agree with John - end quote.

OK, so if it is not "just" then what else are you trying to be?

John has been given the answer. If, for what ever reason the answer is not what he wants to hear (or read) then tuff...You say it yourself, the smallest part looks about 16mm by 50mm...

John does not say what hit him or at what speed. So let's say a 2 tonne car at 5kmh...The impact zone is spread over about half of the trailers rear end by the sound of it and that is 5 foot wide!!..Spread over such a large area, I am surprised that there was even a scuff mark...But the energy of the impact has to end somewhere...and it ends at a steel plate 5cm wide by 1.6cm thick.

I am not going to do the math to work out how much force the tow bar would have been under if it were a 2 tonne car at 5kmh...cos I am lazy :)

PS...Yes, I know, it is probably 19mm thick (3/4 inch) :)
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Follow Up By: pop2jocem - Saturday, Nov 23, 2013 at 17:51

Saturday, Nov 23, 2013 at 17:51
G'day Ron,

Sounds like you and I have a similar history in as far as employment goes.
I did my time (apprenticeship) towards the end of the steam era (boy am I showing my age...lol) Some pretty heavy lumps of iron went into those old engines. A fairly good intro to swinging various sized hammers too. Yeah, spent many a memorable hour working on earthmoving gear and heavy diesels after that. Would I try swinging a 14 pounder now??? Not on your nelly, that's for youguns with more testosterone than brains.
As far as a back stop goes I think you would find the end on grain of a good sized and seasoned lump of jarrah does not give or absorb much. I guess that's why most of the old blacksmiths used that as a base for their anvils.

Herbal,

Quote "John has been given the answer" etc etc.

Well that's it then, end of story.

Cheers
Pop
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Follow Up By: Herbal - Saturday, Nov 23, 2013 at 20:20

Saturday, Nov 23, 2013 at 20:20
Cool, Pop...Glad we got that sorted out...

So, John will only accept an answer that fits in with his preconceived desirable answer.. which is the tow bar tongue must be sub standard or faulty, because he refuses to accept the fact that even a low impact can cause that sort of damage... despite all the posts from people knowing better, science, mathematics, physics and logic... Some people have even pointed out that the thing is up side down... But John still insists that it is just a scuff mark...I give up !!!

And you say you are - not trying to just be argumentative - and I ask if you are not JUST trying to be "argumentative" then what ELSE are you trying to be ??

Or was the word "just" some sort of typo?

The man asked for help. He was given help. He rejected that help because he 'knows better'.... and I say if the help offered is not good enough, go and find help elsewhere !!

...That is it then - end of story :)




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Follow Up By: Member - John - Saturday, Nov 23, 2013 at 20:59

Saturday, Nov 23, 2013 at 20:59
Pop, this is not for you, but for Herbal. I hope he reads it.

Herbal, how dare you put words into my mouth/post. I have been seeking answers to something that I can't understand and I think is potentially dangerous. I have given the facts, corrected some people that can't read english and presume things. I have never refused to accept that is may be possible for a very low impact accident to cause the damage that has occured or rejected the help offered here.

No, the tow tongue is not upside done, it is designed to be used both ways, which is why it is listed as a 3 1/4" drop, 2" rise.

As can be seen in the attached pic, the scuff mark on the trailer tailgate is just that, a scuff mark.

What I do reject is your ill informed and rude comments.

END OF STORY.......................

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Follow Up By: olcoolone - Sunday, Nov 24, 2013 at 09:07

Sunday, Nov 24, 2013 at 09:07
John it would be normal for a tongue to bend like that considering the amount of leverage that has been applied to it.

The longer the lever the lesser force/energy required commonly called in engineering a "mechanical advantage".

Put a peice of 50x6mm flat bar in a vise and try bending it with a 4 inch shift and then try the same thing with a 8 inch shifter, the 8 inch shifter will bend the bar easier with less energy........ this is the same principle as that has happened to your tongue. Your trailer has acted as a 12 foot lever.

A tongue is designed to pull and not be pushed.

Have a look here and read the "law of lever".
http://en.wikipedia.org/wiki/Mechanical_advantage



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Reply By: Member - Andrew & Jen - Sunday, Nov 24, 2013 at 10:04

Sunday, Nov 24, 2013 at 10:04
Hullo John

Given what you have said, this may be an explanation

I do not know the details of the car that hit you - let's assume it was a medium sedan with a crumple zone front end. Let's also assume that the impact speed was under 10 kph.

The kinetic energy even at that "low" speed is still considerable, certainly enough to cause damage. This energy will be absorbed / dissipated by both vehicles. It may be that the colliding vehicle absorbed its share in the crumple zone, which "popped out" afterwards. For the rear of the trailer, it would experience the shunt spread over the full width and given the crumple zone of the car, it would be a "soft" hit with no one part severely impacted. Nonetheless, the total force would still be considerable.

Given the build of the trailer, that kinetic would be transmitted directly through the A frame to the coupling and then to your vehicle.

Now your vehicle would presumably weigh 2.5 to 3 tonnes and would take quite a force to jerk it forward. The fact that you don't feel much of a jerk indicates something took the energy out of the system before it got to you.

That something was the tang on the hitch. Fortunately for you, it has a crank - a double bend - so that it bent, absorbing the kinetic energy.

The tang had both a compressive force applied to it AND a bending force (moment) because the hitch and the receiver are offset, by the look of it by about 12 cms.
Now the steel quality may not be high but I suspect that no matter what the quality was, the result would have been the same.

I hope that helps

Cheers
Andrew
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Follow Up By: Member - John - Sunday, Nov 24, 2013 at 14:42

Sunday, Nov 24, 2013 at 14:42
Thank you, does seem to make sense.
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Reply By: Hairy (NT) - Sunday, Nov 24, 2013 at 19:57

Sunday, Nov 24, 2013 at 19:57
Gday,
Wouldn't be worth the hassel of an insurance claim would it? Put a bar on it, straighten it out and weld a gusset on it.
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Follow Up By: Member - John - Sunday, Nov 24, 2013 at 21:01

Sunday, Nov 24, 2013 at 21:01
Agree, will buy a new one and gusset it. The bending maybe a design feature, but I don't like it if it is...............

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Follow Up By: Hairy (NT) - Sunday, Nov 24, 2013 at 21:47

Sunday, Nov 24, 2013 at 21:47
I doubt it would be a design feature.....maybe a poor design feature. More likely just an unexpected force.

Cheers
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Follow Up By: Member - Andrew & Jen - Monday, Nov 25, 2013 at 12:03

Monday, Nov 25, 2013 at 12:03
Hullo again John

A couple of additional things to think about.

1. It may well be prudent to thoroughly check the hitch and anything associated with it (bolts, etc) for cracks, distortions, etc because it transferred all the forces that bent the tang. (Bolts in shear have a far lower strength than in tension/compression) Also the towbar - bolts, welds, etc. [Although a correctly tensioned bolt also develops additional strength in a joint through friction between the surfaces bolted together.]

2. As I alluded to above, it may well be that the bending of the tang prevented more serious damage elsewhere as the several cms the hitch travelled as the tang bent and came to a stop is certainly preferable to the 0 cms of a dead stop with no movement! From this it follows that an option is not to put a gusset in, as that would lessen (remove?) any movement. Thus the question I would be asking myself is "Is the tang satisfactory for normal use, ie, towing. If yes, consider replacing as is.

Cheers
Andrew

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Follow Up By: Member - Frank P (NSW) - Monday, Nov 25, 2013 at 12:04

Monday, Nov 25, 2013 at 12:04
My two bob's worth ...

If it sets your rig up right (level drawbar with a level tug) I reckon you should replace it with an identical one and not modify it.

In this situation the tongue is a kind of safety valve. Sure it bent, but that was under a load it is not designed to take. Just towing, it was fine, right?

What it did was absorb the forces of the impact by deforming and, without inspecting your vehicle, I would guess that it may have prevented more expensive damage going through to the towbar and chassis. If it was stiffer and/or re-inforced, those forces would be transmitted to the towbar and chassis and if THEY deformed it would be way more serious.

Cheers

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Follow Up By: Member - Frank P (NSW) - Monday, Nov 25, 2013 at 12:08

Monday, Nov 25, 2013 at 12:08
Andrew hit the submit button just before I did, apparently :-) We seem to agree. Sorry for the duplicated info.
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Follow Up By: Hairy (NT) - Monday, Nov 25, 2013 at 13:32

Monday, Nov 25, 2013 at 13:32
True......or its just a piss weak tongue that needs stiffening?????
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Follow Up By: Hairy (NT) - Monday, Nov 25, 2013 at 14:17

Monday, Nov 25, 2013 at 14:17
Gday Frank,

Would you suggest that everyone who has a tongue stronger than this because it isn't raised, lowered or has been gusseted ,go and replace it with something weaker that fails in a very minor incident?
It would be a damn good move in the eyes of manufacturers.......not the consumers pockets though. LOL

I wonder how much that tongue would flex while travelling down rough roads being so flexible? Would that flex cause fatigue and fractures?


I personally would strengthen it to stop it failing and install a shock absorber or bumper to work as a shock absorber if designing with rear end collision in mind........just me.
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Follow Up By: Member - Frank P (NSW) - Monday, Nov 25, 2013 at 15:07

Monday, Nov 25, 2013 at 15:07
G'day Hairy,

No I wouldn't suggest that. I just think that John is fortunate having a tongue that did what it did under the circumstances, rather than transmit the damage to somewhere more serious. (That may have happened anyway - he needs to look.)

The tongue is designed to take a vertical load which is pretty modest, say about 350kg (yes, there will be rigs with more), plus the tension load from the tug pulling the trailer, or the compression load from the tug reversing the trailer, plus an overload factor. The sum total of these may be significant, but they'd be way less than the compression load applied by even a mild tail-ender such as John had.

Towbars and their attachments must comply with Australian Standards. Having said that, it is possible that the tongue did not comply.

It's a common design. If it complied with the relevant standards I don't think it would flex and fatigue under normal operating loads and conditions.

Interesting you mention a shock-absorber. I think the towbar for early model (I reacll this from mid 70's) SWB Landcruisers (or maybe Patrol) had a buffering system rather like the Alko rubber suspension system for caravans.

Cheers
FrankP

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Follow Up By: Hairy (NT) - Monday, Nov 25, 2013 at 15:46

Monday, Nov 25, 2013 at 15:46
I think people are missing what John said........The passenger didn't even fell the impact.......it didn't hit hard enough to bend the tailgate.
A different type of force yes but to bend the tongue (probably 16mm or more thick) before bending the tailgate?????
I wouldn't have much faith in that tongue any more without strengthening it somehow.
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Follow Up By: Member - Frank P (NSW) - Monday, Nov 25, 2013 at 16:20

Monday, Nov 25, 2013 at 16:20
I assumed he was going to chuck it out and buy a new one.
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Reply By: Member - Craig F (WA) - Monday, Nov 25, 2013 at 15:57

Monday, Nov 25, 2013 at 15:57
As part of my work I spend around one week in five in China. We build large mining machinery. I can say based on experience that there can be a lot of discrepancies in Chinese steel and it is the end users responsibility to NATA test plate used for anything that is subject to Aus standards.
The potential for this plate to be non complient is a definite consideration.
Other things to take into account any pre heat applied to the steel prior to bending, pre heat to the weld and scoring to the plate caused by the female V used when pressing. The later has the potential to leave a weak point (crease line in the plate which looks to align with where the plate has bent.
You then need to take into account the incident that caused the damage. Was the plate level at the time of impact? If the car was nose down (Under braking, un-level Suspension or on a hill then the force applied would not be able to transfer the load.

I and a structural engineer have spent our lunch pondering this and both agree that there is a myriad of factors that we do not know.

What is safe to say is that the plate has taken a lot of force regardless of how slow the impact was there was still substantial force. Even 250 grade steel would take a bit to bend it!
I think if this is the only damage the plate has served you well as it a cheap replacement.
As for fit for purpose. In normal situations more than ample.

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Follow Up By: Member - John - Monday, Nov 25, 2013 at 18:49

Monday, Nov 25, 2013 at 18:49
Craig, thanks for the reply.

Circumstances were; level road, wet road, car had stopped, trailer was level, why I used the tow tongue the way I did, tow tongue level.

Thanks once again.
John and Jan

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