Retired Old ■■■■:
Most of Leatherhead is lying awake all night.
As the rear of the jaw pushes against the rear of the trailer pin, the trailer is technically being pushed. However, the term pulling is used describe when the prime mover is in front of the trailer not hooked on behind a low loader pushing. I think this is a circular argument and now I am going to push off out of it and leave it for some other pushy drivers to continue.
Jelliot:
Carryfast:
Being absolutely technical a ‘tractive unit’ forms part of an artic outfit the other being the semi trailer.As such the pin is attached to the trailer and the ‘eye’ is formed by the fifth wheel.In which case the ‘eye’ ‘pushes’ against the pin.The same applies in the case of B train couplings.So the question really should have been does a fifth wheel coupling pull or push a trailer.Whereas in the case of a drawbar outfit the pin is attached to the ‘prime mover’ and/or trailer and the eye is part of the drawbar.Therefore the pin ‘pulls’ against the drawbar.
As for the Ozzies road trains used to be mainly drawbar outfits obviously using a prime mover and usually semi trailers converted into trailers using converter dollies.After the change to combinations of an artic and drawbar trailers using converter dollies the term prime mover was probably,erroneously,kept on.Probably because a semi trailer that’s designed for use as part of a road train isn’t really just a semi trailer in it’s own right.
Not a lot of people know that.
OK, bag of worms time
Most road trains operating in Australia at the moment are set up as this…Prime mover at the front that uses a B coupling ie a 5th wheel. Most of the time, but not always the 5th wheel is set on a ball race. The 5th wheel is only there to couple to the pin, the ball race does all the turning, and is locked into position to hitch and unhitch to the pin on the semi trailer. The 5th wheel does all the oscillating. Up until the last ten years or so the second trailer would have been connected to the second trailer via a converter dolly, that would be connected to the rear of the first trailer by an A coupling, VBG Rockinger etc…As would all the other trailer allowing for an overall length of 53.5 meters, usually 1 prime mover, 3 semi trailers, and 2 converter dollies.
Note the difference between an A and B coupling is this.
In the event of a trailer overturning an A coupling ( VBG/ Rockinger etc ) will swivel through the horizontal independently of the rest of the vehicle allowing the trailer to overturn with out effecting the rest of the vehicle.
A B coupling ( commonly known as a 5th wheel ) won’t allow this and will take the rest of the vehicle with it in the event of an over turn. On the whole the Australian government and CSIRO decided that a B coupling was more stable than an A coupling.New regulations now start that it is possible to us a B-A-B combination as long as the overall length of the vehicle does not exceed 53.5 meters, and it goes like this…
Prime mover at the front coupled to an A trailer, that trailer carries a 5th wheel at the rear which is connected to regular semi trailer and that on it’s own would constitute a regular B Double combination. The rear of the B trailer is connected via an A coupling ( VBG ) to a converter dolly, which tows another B Double trailer set. So in essence it’s 2 B Doubles being towed by one prime mover. There are restrictions on which routes these vehicles can operate on.
Those are the most common Road Trains Used in Australia today.
If your pulling B-A-B’s, sometimes when you get to hill ( especially in the wet ) you might have to drop your rear set, go over the hill and return for it, then try and re couple in the dark. That’s fine if you getting payed by the hour, but most drivers are payed by the K so it ■■■■■.Some of the trucks that run in the mines on private land are very different, and when you think of mines were not talking about a few k’s from collection to delivery, some of the haul roads are 60 to 100’k from the diggings to the processing plants, and get farther out as the mining work develops.
I hope this clears it up.
OH and just my opinion but prime mover pulls the trailers, if you’ve ever tried to push 3 trailers and 2 dollies backwards you wouldn’t have any doubt at all…
Jeff…
Well said Jeff
who gives a ■■■■ as long as its still behind you when you get to your destination lol brgds
shirtbox2003:
Answers please.
Hey, the trailer pushes the tractor downhill 
and pull the tractor uphill or till the strongest wins
Cheer Eric,
Here`s another way of looking at it…the drive axle (axles) is BEHIND the fifth wheel plate jaws and the trailer king pin, therefore the physical force, the “drive”, is PUSHING forward, against the king pin! So on that basis, you could reasonably argue that the trailer is pushed.
shirtbox2003:
Answers please.
Trailor or …trailer,answers on a postcard please!
David
BRS FH66:
Retired Old ■■■■:
Most of Leatherhead is lying awake all night.As the rear of the jaw pushes against the rear of the trailer pin, the trailer is technically being pushed. However, the term pulling is used describe when the prime mover is in front of the trailer not hooked on behind a low loader pushing. I think this is a circular argument and now I am going to push off out of it and leave it for some other pushy drivers to continue.
What a load of boll@cks !! how can a trailer pin push when the trailer cant move unless it is being pulled !! Doesn’t everyone have more important issues to attend to ?
I’m off to bed, early start tomorrow, got trailers to load for Doha ! Rest well everyone. new route…watch this space.
GS
GS OVERLAND:
BRS FH66:
Retired Old ■■■■:
Most of Leatherhead is lying awake all night.As the rear of the jaw pushes against the rear of the trailer pin, the trailer is technically being pushed. However, the term pulling is used describe when the prime mover is in front of the trailer not hooked on behind a low loader pushing. I think this is a circular argument and now I am going to push off out of it and leave it for some other pushy drivers to continue.
What a load of boll@cks !! how can a trailer pin push when the trailer cant move unless it is being pulled !! Doesn’t everyone have
more important issues to attend to ?
I’m off to bed, early start tomorrow, got trailers to load for Doha ! Rest well everyone. new route…watch this space.
GS
Bhaam! Like a boss! Well said Gavin
GS OVERLAND:
BRS FH66:
Retired Old ■■■■:
Most of Leatherhead is lying awake all night.As the rear of the jaw pushes against the rear of the trailer pin, the trailer is technically being pushed. However, the term pulling is used describe when the prime mover is in front of the trailer not hooked on behind a low loader pushing. I think this is a circular argument and now I am going to push off out of it and leave it for some other pushy drivers to continue.
What a load of boll@cks !! how can a trailer pin push when the trailer cant move unless it is being pulled !! Doesn’t everyone have more important issues to attend to ?
I’m off to bed, early start tomorrow, got trailers to load for Doha ! Rest well everyone. new route…watch this space.
GS
Still waiting for photos from the last trip !!!
Are you going this time, or are just going to lard it about on your boat while someone eles has a bit of fun■■?
Jeff…
Personally I think that it is the fifth wheel that does the pulling as the weight of the trailer bears down on it. The pin is a safety device. Proof of this is that when you pull the unit out from under you have to apply the trailer brakes or the whole things comes with you even though you have freed off the pin lock!!!
Good replyfrom jelliots post makes sence,also makes us think,jazzandry your post is also spot on…ps my post on my driving history is locked at the moment, techinal issue [i think ]lots more to follow in smaller parts [maybe].
Certainly hope you’ll continue your story. It’s rivetting!!!
