I take alot of notice of Trucks here in Adelaide, South Australia and majority of our major transport/freight companies that travel from state to state generally use Freightliner Argosy's, AeroDyne Kenworths and FM12-16 Volvo Trucks. The difference i've noticed from many pics of all the big rigs in the US is the large percentage of really Long Wheel base prime movers. I couldn't imagine any Trucks we use here for our B-Doubles (2 trailers around the city and interstate) or even Single Semi trailers around town to be used with anything but a wheel base as short as possible for maneuverability. Also getting the correct weight over the front axel. Im not sure if that rule applies over in the states. I've also noticed that majority of the trailers are dual axel with a large distance between them. as opposed to our Tri-axel trailers (99% of trailers) My question i suppose is altho i may be completely wrong as i've never been there myself, Why are the US trucks generally a much longer wheel base. As for trailers... weight over axels? unnessesary axels? not big on massive weight? Im pretty sure the rule of thumb here in Aust is 9TON on each rear axel including trailers and 6.5 on steer axels. It's something that i've always wondered. Australia. American
This has some info I have seen a fair number of B doubles with bonneted trucks http://www.roadtransport.com/blogs/big-lorry-blog/2009/06/aussie-roadtrains-and-outback.html You always see the Kalari ones going up and down south rd, poor buggers. Wonder if the driver stays in the cab when the woodchipper gets tipped?
Don't know a whole bunch about our truck laws except I had to get the license to be able to drive them to the shop when problems happened. I do know we have federal bridge laws that specify the distance between axles, the weight limits by tire size and the gross vehicle weights you can license any particular configuration for. To add to that each state comes over the top of the feds and applies their own set of "regulations", meaning their cut of the tickets to those who didn't know there were differences when you cross state lines. I know there are people on here that are experts who can make for a more intelligent conversation than I could supply. It's a good question.
Thanks for your replies.. A bloke at work also reminded me that we need the shorter chassis prime movers as we rely heavily on B-doubles to transport majority of our freight around the country and cities rather than the US where your Rail Network is at a much much larger organised scale. As for axel weights etc..would be interested to know if your regulations are simular to ours etc...like you said, from state to state it would vary...which i would imagine would be a hot subject amongst truckies.
It used to be before bridge ratings that you could put up to 660 pounds per cross section inch per tire. A six inch wide tread could carry 3,960 pounds per tire so you were allowed about 15,840 pound per axle if the axle was rated that high. I know it has changed now as 38,000 pound tandem rears are usual and customary in the over the road tractors and I've seen plenty of heavy hauling low boys running 44,000 or 46,000 rears. The tires are better now and people run super singles a lot. When I first stated out as a wrench 8,000 pound front axles were normal but now days it seems 12,000 pounds are the common units. You can find lots of variations in set back, standard and set forward front axles. I don't no much about advantages and disadvantages of each. In this state we have lots of trucks running single and double drop axles and I've seen plenty of truck and trailer combos licensed for 105,000 pound GVW. The common over the road truck used to run 80,000 GVW and I think in many states to the east of us that is still all that can be run. But like I say, I'm no expert on this so someone might chime in a tell me I'm all wet. I've seen television programs that show your truckers long hauling with the road trains. Are they set up with long wheel bases, big horse power and lots of gear clashing?
Road trains are usually 120 metric tons, engine power has crept up over the years, used to be 350hp was the norm, now it's 500+, there are usually 15 or 18 speed boxes in RT spec trucks. The wheelbase doesn't really change, basically it's a standard semi trailer pulling 2 or three trailers with dollys. On private haul roads you can find bigger units with more trailers. This is an older video showing RT's http://www.youtube.com/watch?v=V_oJLMiXYhs There is now a rail line between Alice Springs and Darwin, so there is not as many RT's as there used to be but a lot of time sensitive freight still goes over the road. These are usually operated by two up teams to go non-stop. This is the usual workplace of a RT driver, not much to look at http://www.youtube.com/watch?v=cuV4b6Y_oEA&feature=related