I’ve been asked for some input about an incident that happened to somebody I know.
The driver in question hooked up to a trailer, did the “tug” test, connected the safety clip, drove around the premises, loaded the trailer, drove onto and off of the weighbridge, and was pulling out of the premises and turning sharply when the trailer came away from the tractor unit.
This buckled one of the trailer legs, damaged the trailer rave and the tractor unit, and caused damage estimated at £1,600 which he has been told he will have to pay for out of his wages.
Leaving the legality of this aside, after the incident occurred the fifth wheel handle was still engaged and the dog clip was still in place.
Is it possible for this to happen by slightly under-running the pin or does it automatically indicate mechanical failure of the fifth wheel jaws or trailer pin? I always thought the jaws would only close if they engaged with the central part of the trailer pin but another driver I spoke to said that they can be activated by the bevel.
I have heard of this happening before but very rarely. I always make sure there is no daylight between the fifth wheel and the underneath of the trailer as I believe its possible to think you’ve hooked up ok but there’s a gap there if you know what I mean.
Did the driver do a visual check of the jaws i.e. got underneath the trailer and looked?
This would really be a “belt and braces” step because if he has done a tug test, checked the handle is engaged and was able to lock the safety clip, then he has done as much as reasonably possible to ensure the trailer is coupled correctly. This should mean that his liability for any damage ends there.
By all accounts it is possible to lock the jaws and have the pin sitting on top of them. As for drivers responsibility, unless it is company procedure as laid down in the ssow signed by the driver in his training records that a visual check is done then they can’t really take action against him. If that was the case and I was in his shoes I would be fighting any sanction in grounds that I had done the tug test and fitted the dog clip and thus followed the company procedure. Mind you I always lift the unit suspension once the fifth wheel has gone under the trailer which should avoid this scenario.
I always check that the bar is across, but I suppose that is no guarantee that nothing untoward will happen.
If everything was done correctly then there maybe there was a fault with the turntable, from the few mishaps I have seen, the trailer has come adrift within a matter of yards.
Harry was oldish or high mileage unit that this happened on
Why i ask is that i had a simular event a few years ago but in my case i was lucky as i had another driver from our company helping me as he was waiting for the trailer space in a customers yard.
I hitched up to the loaded trailer which had been dropped quite high did the tug test walked under to check the pin all good the other driver tugged the arm all good so i pulled away and turn sharp right and down a small slope to go around the yard and the trailer became detached and landed across the units back wheels.Same damage landing legs,rave bar,rear mudguards on units along with one set of lights.
The other driver followed me back to our yard after we got a few forklifts to lift the trailer and reconnect it the trailer followed perfected.So the fitter was dispatched to meet me in the main yard to check it all and was tolded to wait for my P45.But on testing the units 5th wheel it had so much slack in it it was deemed that the angle of the turn and slope had given the the pin enough room to pop over the top of the jaws.
Just wondering as mine happened on a very high mileage Scania it was four years old but was on around 850kms ex triple shifted and loads of triler swapping which had worn the the fifth wheel and jaw.
the big un:
Harry was oldish or high mileage unit that this happened on
Why i ask is that i had a simular event a few years ago but in my case i was lucky as i had another driver from our company helping me as he was waiting for the trailer space in a customers yard.
I hitched up to the loaded trailer which had been dropped quite high did the tug test walked under to check the pin all good the other driver tugged the arm all good so i pulled away and turn sharp right and down a small slope to go around the yard and the trailer became detached and landed across the units back wheels.Same damage landing legs,rave bar,rear mudguards on units along with one set of lights.
The other driver followed me back to our yard after we got a few forklifts to lift the trailer and reconnect it the trailer followed perfected.So the fitter was dispatched to meet me in the main yard to check it all and was tolded to wait for my P45.But on testing the units 5th wheel it had so much slack in it it was deemed that the angle of the turn and slope had given the the pin enough room to pop over the top of the jaws.
Yes good point, the workings must take a right hiding over the years especially if its a company like ours which is dropping and hooking up trailers upto 4 times a day maybe.
the way jaws work is a lot better than it used to be,i have very seldom come across a fifth wheel with worn jaws if the clip is in it will never come detatched from the trailer …so do it the way you should
in all my years i have seen two trailers detach one the pin sheered the other the bolts holding the fifth wheel sheered because of bad maintenance
if the clip goes in the lock bar is located …end of
I have been trained by JOST in fifth wheel repair and maintenance and know the components very well.
There would have to be more than a substantial amount of wear for a properly coupled pin and fifth wheel to seperate leaving the jaws closed and release handle still ‘in’. A fifth wheel with that amount of wear would be terrible to drive with - knocking and banging. I doubt a driver wouldn’t notice this.
It is feasible that during coupling if the fifth wheel is set too low for the pin - the base of the pin can ‘trigger’ the jaws and therefore the lock bar. Once the lock bar slides across the release handle will go in and the dog clip can be fitted. it would seem to be coupled. A ■■■■■■ test would more than likely feel ‘wrong’ or different but it would more than likely tug the trailer and to an unobservant driver seem OK
it is all about visibly checking the coupling. Look for gaps between the fifth wheel and trailer rubbing plate. Look for the king pin - shouldn’t be able to see it. If it is safe to do so - look for the lock bar across the back of the fifth wheel ‘throat’. Check the safety latch/dog clip etc
I am delivering coupling training to a company on Saturday. I think they have had an incident recently. We are doing a 7 hour DCPC session followed by this coupling training which unfortunately isn’t part of the DCPC course. We will cover the braking system and why just dropping the red line isn’t sufficient. How trailer brakes work - specifically the park brake. The workings of the fifth wheel. Why rollaways happen and finally how to couple correctly and what safety checks to carry out after coupling.
I know some of the drivers will resent being shown what they already know how to do but hopefully by raising the issue it might prevent a more serious incident.
Hopefully if this link works you should get a decent video showing how the jaws lock onto the king pin etc http://www.youtube.com/watch?v=atKelxzvoHA This is the LOST fifth wheel. Other makes work in a very similar manner but I believe JOST to be the best there is
Harry, leaving aside wether its possible or not.
Surely your input is only limited to you seeing him do the tests etc.
If so, report that and walk away.
edited to add
just read your post again and maybe you are not asked for input as a witness.
i used to work in a engineering factory[wordsworth holdings-prev aveling barford],they brought big D fifth wheels and manufactured them there,i was a universal grinder but when work drop off i had to go welding as i was coded as well,we used to weld the fifth wheel plates up,ramps,sliders etc,the fifth wheels were fitted up on a jig,you fitted jaws,springs,clips,adjuster rods etc to the pressed plates,the manufactoring tolerances meant it could be a right pig to get them to work right at times,you were doing them on piece work so had very little time to mess around so often they were let go ,lets say not 100 % ,at times theyd come back under warranty to be rectified,i often had to put the lock plate on a surface grinder and skim a few thou off of them to get them to work correctly
no idea if these going out ever caused a tri to come off but worth a thought,they were sold off a fair few years ago to jost,if i remember right there 5 th wheel plate was cast so maybe not as much variation on tolerances as a pressed plate,the jaws were machined on a cnc miller,the side plates were done on a plasma cutter,adjuster rods at time were done on a capstan lathe,obviously the end product was only as good as the turner,miller,plasma burner lad,
I put a post on the Tesco drop and shop thread about this very subject, this is the relevent paragraph copied from that post.
‘‘A few months later i discovered why, picked up a loaded trailer that had been dropped on uneven ground leaving trailer on a slight lean to one side.
Anyways it was dropped low enough (real springs then) and i backed under it, kerlunk, i’d got it but something about the pick up didn’t sound quite right, so i connected the lines and dragged it out to some level ground to have a look.
Sure enough the bloody thing was sitting on top of the jaws, you could have knocked me over, till that moment i would never have believed it could happen.
Since then i too never assume the sharp tug guarantees you’ve really got it locked and always have a look to see if its inside or sitting on top.’’
To add a little to this, the jaws were not appreciably worn, a near as dammit new F90 MAN of late 80’s vintage with IIRC a Big D 5th wheel.
This is a rare happening and no trainer that has ever overseen me has looked for, suggested i do so, or instructed me, to check the jaws are indeed round the king pin.
It should IMO be part of normal connecting up process, though some drivers still don’t have the foggiest idea how to do it anyway, in the last month our yard has seen several undershoots of the pin and more serious damage.
It would hep if some had a clue how to drop trailers in the first place and not leave them as high as physically possible.
This problem is more likely with todays air suspended tractors, the guy dropping the trailer has more than likely wound down the legs until touching the ground, done the various uncoupling procedures and pulled forward, trailer doesn’t drop much but suspension on tractor lifts as as the tractor clears the trailer, oops forgot to lower suspension! Next guy comes along to pick up the trailer, keeps going waiting to ‘clunk in’, nothing until trailer hits cab, or gap between trailer bedplate and tractor fifth wheel is just enough for the pin to activate fifth wheel locking mech and as said by others the pin is on top of the jaws.
This wouldn’t happen if the trailer had been dropped at a lower height and the tractor picking up the trailer backed on (with lowered suspension) but not fully onto the pin, then raised the suspension to lift the trailer before backing fully on. With the older steel suspensions you were usually lifting the trailer a good amount anyway so a sound connection would be made, all the various checks can confirm this but miss these out and it leaves chances of a missed pick up more possible. Having a practised set routine as most drivers indeed do, to include all the checks from first backing up to the trailer to finally releasing the unit handbrake and driving off, should cover every possibilty apart from a defective mechanism but the driver would usually suss this by the feel of the handle (sloppy) or by the handle not fully going home or as has been said ‘it just doesn’t feel or sound right’.
The jaws of the fifth wheel are secured by a mechanical lock, the strongest lock available and this would rarely fail, it would be the other components such as springs, bolts and the handle itself that more than often caused a problem. In the case of this lads incident it seems he just didn’t pick up the trailer correctly, however I was a little concerned the trailer was lifted and the same unit backed under it and pulled it back to base for the fitters to then have a look at it, unless I misread this bit and another unit was used. Sorry case all the same. Franky.
I would imagine that the only way to prove “mechanical failure” in such a situation, and therefore get off scott-free is for the kingpin to break off, or the 5th wheel assembly to completely disintergrate.
I’ve not known this to happen to anyone I’ve known over the years, but it must be an occasional mis-hap statistically?
Can a sharp turn cause a kingpin to pop-out of a fully-in & clamped shut 5th wheel jaw?
I don’t know, so I take it easy around corners & roundabouts - which means never overtaking or going around on half my wheels like some I see for certain parcel firms who shall remain nameless to protect the guilty…
I have written long posts about this subject before, the main problem is the wear ring, being WORN or breaking up. GBE had a trailer travel from Le Havre, on the ferry to Portsmouth, up the A34, A43, M1 A50 and into Hilton depot before it fell off!
We had a memo on the office wall almost immediately and the damaged wear ring was on the counter top for all to see…
i witnessed a trailer come adrift last year.when it happened i just thought the driver was a pleb,but when he got out he said it had happened a few weeks earlier in a different customers yard,and that when he reported it to the garage they put it down to driver error.he also said that this fifth wheel was not the original and had been swapped for some unknown (to him) reason,some time earlier(before the first detachment).
anyway,he refused to use this unit any longer,so our on site manager agreed that it needed looking at,but we couldnt leave the trailer where it was,so we got it upright and he backed under it again. this time we watched as he carried out a text book coupling exercise and proceeded to back the trailer up into its original position.
as he stopped the trailer became detached again but this time it did`nt slide off…we then asked him to back under a third time,but this time i went under and watched…the locking bar had only come part way across
this happened on a 56 plate fm which was then vord until a new fith wheel was fitted....driver error my arse,if you ask me there were some corners cut there(suspicious fifth wheel swap) and it was only down to luck that a nasty accident didnt occur
