Linkage on road trains - like aussie

[knotian]

I'd like to tackle a road train. In the videos I've seen that or curves, even in the cities, they track perfectly. Does any one have diagrams as to how this is done. Of course if there is MOC it would be wonderful.

[DrJB]

Just a 'minor' addition: For those who are not familiar with what a road train is. It is essentially a truck with multiple trailers one behind the other. The suspension/articulation geometries must be 'right' to ensure the convoy is stable.

Spoiler

Can you rescale your image?!

Edited May 31, 2018 by JopieK
Can you rescale your image?!

[andythenorth]

Just leaving this here  http://blog.hemmings.com/index.php/2009/11/19/54-wheel-drive-the-letourneau-electric-arctic-land-trains-that-put-australian-road-trains-to-shame/

[bonox]

Trailers are of two basic types under Australian (and international) regulation. These are type A and B. The difference is that a B type trailer is coupled to a rigid turntable on the leading unit (be it a prime mover or another trailer) and an A type trailer is coupled to the leading unit by a drawbar. Often for road trains, this means A trailers are constructed out of a classic 40 or 50 foot semi B trailer connected to a 2 or 3 axle converter dolly and the dolly has the drawbar connected to a pintle on the leading unit. ie like this:

Now a road train is typically made up of at least one A trailer and a total length under 53.5metres.

The ones that track perfectly are the B doubles/triples. That is, trailers conneted with only turntables - no drawbars, as below:

 There are limitations here on where you are allowed to run road trains and B doubles/triples, and there is a wide arc around every major city where you are NOT permitted to bring a road train. This means that you have not seen a road train in a city. You've probably seen a multiple B type setup in cities, and generally only two trailers (a B double), but there is opening for B triples in some places.

As a rule, because of the rigid forward attachment of a B trailer, they track much more accurately than a standard A trailer, but B only configurations are not generally regarded as road trains.

Suggest you find some background reading here.

http://www.truck.net.au/sites/default/files/TAPs - description of truck configuration September 2016.pdf

Some update info:

The north americans refer to the trailers similarly, but the lingo is a bit different - they have terms like Super B.

And I said as a rule, "A" trailers don't track as well as B trailers, however there are in development "smart" trackaxle converter dollys to improve tracking of multiple A trailers like an A Double setup (a classic road train). Refer to the pdf above for a bunch of lovely pictures describing the different trailer and primemover configurations.

Edited May 31, 2018 by bonox

[RohanBeckett]

7 hours ago, andythenorth said:

Just leaving this here  http://blog.hemmings.com/index.php/2009/11/19/54-wheel-drive-the-letourneau-electric-arctic-land-trains-that-put-australian-road-trains-to-shame/

Nice.. but I doubt it can do 100k/h (62mph)!

each to their own purpose though!  the arctic one is definitely special-use!

[Omikron]

Always wondered why railroad wasn't an option

[Imanol BB]

45 minutes ago, Omikron said:

Always wondered why railroad wasn't an option

If i remember correctly it is because of the flexibility the road trains offer over the conventional rail trains, in Australia, these road trains are used to transport large quantities of cargo to remote locations, locations which don't require of an ultra large quantity of cargo and are not as populated as a big city, so they don't need this type of transporting, because of this, rail trains wouldn't be so much efficient, you must first build the tracks, and it wouldn't make sense to build tracks from one remote location to another, and just lo leave an "small" cargo on each, but these locations still need to receive a relatively large quantity of cargo, you can think that these road trains, are like an "express" transport, they carry a relatively big cargo from one place to another remote place and they don't have to move over an specific like rail train does, so they are much more flexible when going to a destination, and even when they are inferior to rail trains in terms of cost efficiency, they are best suited or these type of job, you could think of trains like a large cargo ship, it wouldn't make sense to use an extra large ship to move large quantities of cargo and make it stop in lots of different destinations to just leave an small cargo, it is much more convenient to transport very large quantities to a certain place and then use smaller transport methods to distribute them to their specific destinations.

[bonox]

also many of these things are used in areas where the road gets washed away every year in the wet season. For the mass of cargo carried, plus the distances involved, rebuilding a one or two lane dirt road is a lot cheaper than rebuilding a railway.

Keep in mind that this country is the size of western europe or north america, but has a tiny portion of the population of either of those and in the time it takes me to get between major cities I can cross multiple countries in Europe. We do have rail for major transport tasks - but really only between major population centres and between major mining/farming entities and ports. That probably covers less than 1% of the major transport routes.

oh, and the only real reason to use a road train is to reduce payroll costs. Everywhere else in the world would just run three trucks instead and put up with paying three drivers.

There is a small  maintenance and fuel advantage but mostly it's about the pilot.

Edited May 31, 2018 by bonox

[andythenorth]

If you want more background (and a dose of highly fake not-really-a-drama-mate drama), Outback Truckers is a good show 

[pagicence]

@knotian If you want a road train that tracks (follow) perfectly then you might want to consider some type of mechanisms that is used on an airport baggage train (youtube link) or industrial material handling trailer (youtube link) or a trailer that transports combine’s headers. They all use same principle mechanisms (youtube link 1, youtube link 2, youtube link 3, youtube link 4) and they all have rear wheel steering at the same angle as front wheels.

But with something like a road train with truck and trailers, I don’t think that the trailers have counter rear wheel steering and there is no way that without it they can track (follow) the lead vehicle perfectly. Unless the counter steering is done hydraulically at very little angle (maybe 5 degrees at the most), and I'm pretty sure that’s not the case. Australians know this better than me. Am I right?

For a standard road train use what @bonox said.

On ‎5‎/‎31‎/‎2018 at 1:57 AM, bonox said:

Suggest you find some background reading here.

http://www.truck.net.au/sites/default/files/TAPs - description of truck configuration September 2016.pdf

Maybe this helped a little.

[andythenorth]

Perfect tracking mechanism can be seen here https://www.kellyengineering.com.au/tracking-trailer/

Think it requires front and rear steering, cross-linked, with input from the tongue (drawbar). 

Road trains probably don't track perfect 

[Captainowie]

18 hours ago, andythenorth said:

Road trains probably don't track perfect 

They certainly don't. I know from sitting behind them on the road in Western Australia that the last trailer flaps back and forth quite noticeably.

[brickless_kiwi]

The better question to ask @knotian is what scale are you proposing? 1:17 or Mack anthem? The European scale Lego truck scene is just something else when you see the photos from different shows, but also the money tied up in some of those models is something else. Search trailers on rebrickable for some ideas or even some of the MOC builders ( I'm net naming names as Id hate to miss someone out and that would be rude of me )

[knotian]

brickless-kiwi

I really build for my self and many times scale is not a factor. I've done one model in what works out to technic figure scale, made it a tad smaller and now trying to get it to minifig scale. The last effort is stumping me due to space for motors, etc. Most of my research did not show the linkage clear enough to use. The results I've gotten are great and pointed me in the right direction. If I get it built (road train) I will post a .io file.

[neonic]

Myabe late and not usefull anymore but I 'found' this topic while looking for something else.

About the steering ... I'm not an expert but I'm interested in trucks and all that, especially big rigs / heavy haulage. With those lowloaders and stuff the rear axles are 'controlled' (to steer) by the kingpin of the prime mover (guess there also other ways).
I don't know how it work with roadtrains becuase they look pretty 'standard'.
What I do know is that some roadtrains have a trailer in the combination with an engineblock for more power/traction. I think it might help with the steering too, same idea by trains.