Rear wheel steer, how does that work then?
Discussion
I was behind a (friggin massive) low loader today, being skilfully piloted around the narrow country roads. The driver was using the rear wheel steer to get around the tighter corners.
So I was wondering if it's separate control and generally how it works (I guessed the hydraulic bit)?
So I was wondering if it's separate control and generally how it works (I guessed the hydraulic bit)?
Rear steer on normal trailers is just a loose axle on the back that follows where the trailer goes, it reduces tyre wear and allows slightly shorter trailers to have the wider swing associated with a normal length trailer, the rear axle locks into place with a pressurised pin when reversing to keep the wheels straight. There is another version on really short trailers that works from a mechanical linkage between the units 5th wheel and the rear axle on the trailer.
The one that I am guessing you was following (proper low loader) Is hydraulically operated from a remote control, the ones that I have used don't give you an angle of steering you just get to choose full lock in either direction. Takes a lot of skill to be able to do it yourself whilst driving, most people get the second man (you legally need one of these on oversized loads) to walk behind the trailer controlling it.
They also use systems like that on the shunter vehicles in most docks, watching them push the trailer in front whilst controlling it at speed through tight corners is brilliant. It's like trying to pat your head whilst rubbing your tummy and driving a lorry at the same time.
The one that I am guessing you was following (proper low loader) Is hydraulically operated from a remote control, the ones that I have used don't give you an angle of steering you just get to choose full lock in either direction. Takes a lot of skill to be able to do it yourself whilst driving, most people get the second man (you legally need one of these on oversized loads) to walk behind the trailer controlling it.
They also use systems like that on the shunter vehicles in most docks, watching them push the trailer in front whilst controlling it at speed through tight corners is brilliant. It's like trying to pat your head whilst rubbing your tummy and driving a lorry at the same time.
The ones on the low loader you saw work off a wedge next to the pin on the trailer, when coupled the wedge rests within the 5th wheel and as the truck turns so does the wedge which in turn moves the hydraulics to steer the trailer wheels the opposite way to that which the truck is going, you can also plug a wander lead in the back so the 2nd man can control the wheels independantly in tight situations
And contrary to whats stated above you dont have to have a second man with you on the big stuff , a man in a van travelling behind you is now acceptable
And contrary to whats stated above you dont have to have a second man with you on the big stuff , a man in a van travelling behind you is now acceptable
Edited by loko on Thursday 24th October 13:03
loko said:
The ones on the low loader you saw work off a wedge next to the pin on the trailer, when coupled the wedge rests within the 5th wheel and as the truck turns so does the wedge which in turn moves the hydraulics to steer the trailer wheels the opposite way to that which the truck is going, you can also plug a wander lead in the back so the 2nd man can control the wheels independantly in tight situations
And contrary to whats stated above you dont have to have a second man with you on the big stuff , a man in a van travelling behind you is now acceptable
Correct however there are two solutions to active rear steer on a trailer. The wedge as rightly said activates the system, this can be hydraulic which moves the rear steer on a turntable or it can be a mechanical rod connected directly to the steer axle from said wedge. As the second poster notes there is also a passive rear steer that simply has a free but damped steering axle and extenuates the rear swing. Both solutions effectively reduce the wheel base giving better manoeverability.And contrary to whats stated above you dont have to have a second man with you on the big stuff , a man in a van travelling behind you is now acceptable
Edited by loko on Thursday 24th October 13:03
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