Submission
Twin Steer
Tri Drive
Mass Limits
Discussion
Prepared by Des Taylor
I am pleased this topic has come up for public comment. As a transport operator, our business has used
tri drive prime movers for 16 years from 1998 in Tasmania in which we have gained some insights into the day to day operations and the legal compliance of this particular transport configuration. The main observations are that the laws governing the operating climate determine how productive and cost effective this industry can be. Sometimes it is the attitudes of those given the task of interpreting the laws that determines how efficient this industry can be. Sometimes initiative is restricted from advancing as the laws can be too restrictive.
In 1998 with the recent acceptance of the Mini “B” double combination grossing 50 tonne we began operating our first tri drive prime mover with tri axle semi trailers. Both of these configurations were operated under permit conditions .The state Premier, Mr Bacon expressed the need for our industry to become more productive so these innovations were both obvious and necessary.
Engineering within the transport sector has moved a long way with braking systems improving from a park brake around the tail shaft to maxi brake units on all wheels, from “4”,”5” and “6” brakes to “7” and ”8” with self adjusting mechanisms and disc brakes all conforming to Australian Design Rules. Truck GVM ratings have increased from 36 ton to 90 tonne with front axles being upgraded from 4.6 ton to 7 and 8 tonnes. Along the way a number of safety systems, ABS, EBS and stability and more have been added to the basic prime mover. Tyre technology and truck suspensions have also greatly improved. While it has taken 50 years to get to this level of engineering, the productivity of the basic semi trailer configuration has only increased marginally. The gross weight of 36 ton went up to 42.5 tonne which covered the increases in the vehicle tare weight and a small payload margin to regain some efficiency in the industry.
Our tridem prime movers started with 52.5 tonne gross (6 + 22.5 + 22.5) plus a tolerance of one tonne per major axle group .This was later reduced (6 + 20 + 22.5) when P B S compliance was deemed necessary and the tolerance was disallowed. These vehicles then operated, at 48.5 tonnes maximum weight. We assessed these vehicles against the P B S criteria and carried out the associated testing but found the expense of certification without any design protection was both horrendous and prohibitive.
These trucks were used to carry a fully loaded shipping container from the factory to the ship side without the expense of topping up at the wharf, as is normal. The efficiency of loading a container to allowable shipping mass can only be maximised if the road freight regulations permit this task to happen. Our vehicles proved they had a vital part to play in accomplishing this task.
There was a preconceived notion that our third axle equipped prime movers could not or would not steer as normal tandem equipped prime mover. While there may have been some substance with this view, evidence from past experience shows the difficulty was with old Tri Drive low loader vehicles and very heavy loads in the 1960’s. We found that by adding a third axle to the original tandem axle outlay and utilising of and being mindful of the ackermen steering principal that our vehicles continued to pivot around the main dominating axle in the group. The other advantage was the understanding that the pounds per square inch exerted to the roadway, was less in a third axle fitted when compared to two axle group when loaded legally.
Driver acceptance has not been a problem with the Tri “Drive” variation prime mover. The vehicle is a familiar configuration with a marginally heavier operating mass.
The versatility of these vehicles with mix and match trailer operations proved to be an asset in our business gaining 12.5% increased payload consistently. While the log hauling portion of our forestry based activities saw the same advantages as our on road duties durability and practicability reinforced this configuration as a viable high productivity vehicle. The addition of the third axle to the drive group increased the stability of the complete combination by more than 22% over a standard semi trailer vehicle. This was the result of testing observed at the test facility near Geelong. Operationally, this proved to be a true advantage where the rigidity of the prime mover offers more support to the following trailer in less than desirable conditions.
The Twin – steer option requires a different trailer construction to allow for the necessary truck to trailer clearance due to the forward position of the turntable in order to obtain the desirable balance of weight distribution across both axle groups. The variation in chassis wheel bases also needs to be considered with regard to correct “Bridge Grouping“. The need for different trailers to suit Twin – steers can be a limiting factor in the capacity of a fleet of “mix and match “ equipment.
Prime mover Chassis “Real Estate” (space) has become an engineering nightmare with the increase of componentry required to be fitted to prime movers. Extra capacity air tanks, Add Blue tanks, cabin/sleeper air conditioning equipment, complex chassis mounted exhaust systems, hydraulic oil tanks, oil coolers and pumps with the PTO equipment, onboard weighing provision, safe storage facilities, and the necessary adequate capacity fuel tanks to list a few of the obvious.
The outcomes of this discussion needs to see there is room for innovation without a lengthy approval process as the Australian transport task is variable and should not be constricted to “one size shirt fits everyone”.
There is always a need for efficiencies in any business which then reflects on the health of this industry. There is a real need for road transport to fit within the complexities of rail, sea and air modes IF we are to be efficient as a nation. The rules and regulations determine our efficiency and not innovation for innovation sake.
We need roads and bridges and vehicle mass efficiencies to meet the doubling of the transport task in the next 15 years. With vehicle mass increases of one tonne tolerance per major axle group, efficiency would improve by 6%.
We have a mindset of restricting productivity when we prohibit maximum loading by heavily fining the truck operator for the smallest amounts of excess weight when his onboard guide is mobile and not a static device. Then there is the driver who does 10 minutes more than his log book allows, by law and, is heavily fined when in contrast another employee works 10 minutes extra and gets paid. The issue here is if operators and drivers are to comply they need to be less efficient than where we used to be. We can justify these couple of examples by saying “it is in the interest of safety” but there is the frustration factor which also reflects on safety.
As past director and share holder I hope my experience and insight may be of assistance with this discussion. If you would like to discuss any of this with me further, I can be contacted on either email of or mobile of 0437 293 553.
Des Taylor
Exeter Sawmill Pty Ltd
18 Emita Parade
Launceston
Tasmania 7250
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