A simple trailer is like an over-grown car trailer, with a tandem axle set in the middle, and a rigid drawbar that transfers weight onto the towing vehicle’s coupling - usually around 4 tonne.

The gross weight for that tandem axle set is usually 14.5 tonne, as the axles are usually less than 1.3 metres apart. A 3-axle set is permitted to run at 18 tonne.

Clause 4.3(6) of the Dimensions and Mass Rule 41001 specifically limits the Gross Combination Mass for a truck and simple trailer to 32 tonne.

Sections 4.4 of that same Rule specifies that the Trailer : Truck Mass Ratio for combination vehicles shall be 1.5:1 or less - that is, the gross mass of the trailer must not exceed 1.5 times the gross mass of the towing vehicle.

That’s pretty straight forward for, as an example, a rigid truck towing a full trailer - the 1.5:1 ratio sets the maximum trailer weight at 60% of the combination, so if we are running at 44 tonne gross combination mass, the trailer is limited to 26.4 tonne.

This is where I should have checked my logic a little more closely, because my first thoughts for the simple trailer application went something like:

                         Maximum Combination Mass =          32 tonne

                        Trailer : Truck Mass ratio                    =          1.5:1

                        so maximum gross weight of trailer    =          32 tonne x 60%

                                                                                    =          19.2 tonne

                        typical trailer Gross Vehicle Mass      =          14.5 tonne on wheels plus

                                                                                                4 tonne on coupling

                                                                                    =          18.5 tonne

Conclusion: Not much point in having a 3-axle simple trailer, because you can’t utilise the full 18 tonne permitted for a 3-axle set.

Wrong.

Read the words and definition of terms more closely - Clause 4.4 refers to “gross mass”, which is defined as “…the mass of that vehicle and its load…which may be determined by adding the mass on the vehicle’s axles or axle sets.”

Note the subtle difference between these words and the definition for “Gross Vehicle Mass”, which is “…the gross vehicle mass specified…by the manufacturer…”

The 2-axle simple trailer mentioned above would have a manufacturer’s Gross Vehicle Mass of 18.5 tonne - that is, you can load it up to 18.5 tonne total - that is, 14.5 tonne on the wheels and 4 tonne on the coupling - and everyone is happy.

From the Trailer : Truck Mass Ratio aspect, however, things are slightly different.

The Mass Ratio considers the trailer’s “gross weight”, being the sum of the weights on its axles or axle sets - in this case, only 1 axle set, running at 14.5 tonne.

Therefore, for a combination mass of 32 tonne, the truck can run at 32-14.5 = 17.5 tonne, giving a mass ratio of 0.83:1 - well below the permitted maximum.

So, if we consider a 3-axle simple trailer with 18 tonne on its wheels, the truck can weigh 32-18 = 14 tonne, giving a mass ratio of 1.29:1, still below the maximum.

Our 3-axle trailer would have a tare weight of around 4.0 tonne, so the laden weights would be something like:

                         Mass on axles                                      =          18.0 tonne

                        plus mass on coupling                         =          4.0 tonne

                        less tare weight                                   =          4.0 tonne

                        gives a payload                                   =          18.0 tonne

Conclusion: Yes, you may carry an 18 tonne machine on your 3-axle simple trailer.

Subsequent note to self: Read those words more carefully.

This increased mass limit is touted as being for “high productivity vehicles”.

I wondered what effect this increase might have on the Road User Charges that applicable vehicles would incur, on the basis that no alterations are envisaged to the Dimensions and Mass Rule other than the maximum permitted combination mass - that is, axle and group ratings continue unchanged.

This effectively means that the only rigs that may run at 50 tonne are:

                                    3-axle rigid truck and 4-axle full trailer

                                    4-axle rigid truck and 4-axle full trailer

                                    3-axle tractor unit and 5-axle B-train

The other combinations - including a 4-axle tractor unit with quad semi trailer - are ruled out as axle group ratings will be exceeded.

Using the estimated weights in the following tables and the current Road User Charges, the calculations for each combination of RUC cost per tonne payload show an interesting trend - every one of them gives an increased RUC cost per tonne, of 16-21%.

So much for “high productivity”!

What this tells us is that there will have to be rather more changes than just the Gross Combination Mass - the Road User Charge scale of fees, for one!

Example 1 - 3 axle truck, 4 axle full trailer

          44 tonne GCM        Truck                       Trailer                  Combination

          Tare (tonne)                9.0                            6.5                           14.0

          Payload (tonne)         12.0                          16.5                          30.0

          Gross (tonne)             21.0                          23.0                          44.0

          RUC                       $369.93                    $184.80                    $554.73

          $ / tonne Payload                                                                       $19.46

          50 tonne GCM        Truck                       Trailer                  Combination

          Tare                            9.0                            6.5                           15.5

          Payload                     13.0                          23.0                          34.5

          Gross                         22.0                          28.0                          50.0

          RUC                       $432.14                    $349.47                    $781.61

          $ / tonne Payload                                                                $22.66 (+16%)

Example 2 - 4 axle truck, 4 axle full trailer

          44 tonne GCM        Truck                       Trailer                  Combination

          Tare                           10.5                           6.5                           17.0

          Payload                     11.5                          15.5                          27.0

          Gross                         22.0                          22.0                          44.0

          RUC                       $237.00                    $162.42                    $399.42

          $ / tonne Payload                                                                       $14.79

          50 tonne GCM        Truck                       Trailer                  Combination

          Tare                           10.5                           6.5                           17.0

          Payload                     14.5                          18.5                          33.0

          Gross                         25.0                          25.0                          50.0

          RUC                       $348.71                    $240.25                    $588.96

          $ / tonne Payload                                                                $17.85 (+21%)

Example 3 - 3 axle tractor, 5 axle B-train

          44 tonne GCM       Tractor        1^st Trailer      2^nd Trailer      Combination

          Tare                            8.0                5.5                5.0                  18.5

          Payload                      9.0                9.5                7.0                  25.5

          Gross                         17.0              15.0              12.0                 44.0

          RUC                       $192.99         $93.23         $103.09           $389.31

          $ / tonne Payload                                                                       $15.27

          50 tonne GCM       Tractor        1^st Trailer      2^nd Trailer      Combination

          Tare                            8.0                5.5                5.0                  18.5

          Payload                     11.0              11.5               9.0                  31.5

          Gross                         19.0              17.0              14.0                 50.0

          RUC                       $268.49        $127.22        $172.63           $568.34

          $ / tonne Payload                                                                $18.04 (+18%)

Last Saturday, I was washing my house’s soffits and guttering, using my Raven Telescopic Water Brush - NZ-made, by Raven Products in Auckland.

I must have been a bit over-zealous with tightening one of the plastic extension collars, because it broke. I had to stop part-way through the job, of course.

After thinking for a little while about the futility of fixing things these days, I decided to be a bit cheeky, and see what happens if I see about getting a replacement.

With my digital camera, I took a photo of the broken part. Next, I used Google to find Raven Products and got their website. I then sent an email to their Technical Services Department, wondering about the possibility of getting a replacement, with the photo as an attachment.

Upon checking my messages on Monday night, behold! a reply from Richard Mitchell, Raven Sales and Marketing Manager, sent that morning and asking me to confirm my postal address so that they could send the piece.

I duly replied, giving my address and confessing that now I’ll have to complete the job. I also asked how I could make payment - might a cheque be acceptable?

Come Tuesday night, another reply from Richard, commiserating with me that cleaning the house is the down-side, but also saying to not worry about payment for this one - one of the perks for buying NZ made.

So, what tools have we used?             - digital camera,

                                                            - Internet,

                                                            - Google,

                                                            - email.

What have we learned?                      - these electronic gizmos can be useful,

                                                            - buying NZ-made can be good,

                                                            - most folk we deal with are great.

He's not really this old

The motivation for requiring certification of draw beams and drawbars came from a spate of fatal accidents involving heavy motor vehicles where the drawbars or beams had worn out and the heavy trailer had parted company with the truck. The operators knew when it was time to replace a drawbar or beam because it was then in two pieces

Today is vastly different. Certification costs are in the region of $250-$450 bearing in mind that this certification includes additional components which weren’t around 22 years ago. In real terms certification costs are probable only 25% of what there were then. NZ Transport agency now set the bar.

Do I think things have gone backwards—absolutely?

22 years ago, from a design point of view, things were pretty dreadful—there were some abhorrent designs. A four axle stock trailer with a 100 x 75 rhs pole (had been upgraded from 75 x 75 rhs after it had broken and the trailer had hit the Awatiri. Most drawbeam required upgrading but because we designed to fatigue criteria and as weld has a much lower fatigue allowance than parent metal, the upgraded drawbeam were reminiscent of battleships. Got a lot of ribbing, some good natured, some not so good. After a period of time 5 to 10 years later I thought overall the standard of design and manufacture had improved significantly. Good robust designs made by manufacturers who knew what they were about.

What’s happened now is that we have a whole new generation of designer’s certifiers and regulators. The regulators have added a lot more complexity to the compliance regime in the name of consistency. Many of the new designers have little practical experience about why things are the way they are and rely heavily on the regulators for guidance! They challenge the old heads, saying in not so many words that we are stupid, not realizing that the old heads know full well that this is a numbers game—you can never eliminate the possibility of things going wrong but you can as sure as hell reduce the odds!

The benefit of employing a specialist engineer within your business is, I guess, confidentiality as well as you the business owner or manager being able to call the shots. The dis-benefit is that the cost of employing someone is usually 2.5 to three times their pay (divide that by the number of hours that they are actually doing the job they were paid to do) – they can get up and leave any time. Pay that experienced designer say 80k PA ($40/hr) , say they do that type of work 65% of the time that they work for you equals a real productive cost of $185/hr.

The benefit of employing us is that our fee rates range from $90 to $175 per hour, we have around 250,000 man hours of data based information on tap, we have a range of skilled individuals to call on, we are totally confidential, have been around for 22 years and intend to be around for much longer

Bearing in mind the above, Randall and Associates Ltd would like to offer a helping hand, by way of fixed fee service contract, to all good operators, manufacturers and suppliers on a national basis which recognizes your excellent standing in the community. We would undertake the following services on a national basis

• “Design and certification” and or “design and issue of statements of design compliance” covering all aspects of heavy vehicle manufacture or modification
• Sales drawings, promotional drawings, concept sketches
• Provision of standard designs specification either on our letter heads or yours

The benefits to you of a fixed fee contract are

• You just pick the phone up and ask for something to be done—you do not have to worry about cost,
• Better staff utilization,
• National coverage, national consistency for design and specification,
• Reduced compliance and design hassle (one organization to work with).

The benefits to us:

• Better use of our staff and expertise,
• Better use of our data based knowledge,
• Better way for us of dividing up the work day.

Call to action—contact Nigel to find out more

Randall and Associates, a mechanical engineering consultancy, employed me after I had completed a BE(Hons) in Mechatronics from Massey University. In the final months of my degree I was job searching and it wasn’t a matter of finding a job, but choosing the one I liked the sound of the most. With Randall and Associates specialising in the heavy vehicle industry and earth moving machinery, I was drawn to this type of consultancy.

When I began, I joined a team designing a fatigue towbar tester. This projects purpose was to mechanically test towbar designs (simulate the life of towbar in hours not years) before they were mass produced. Signal processing, linear displacement, force measurement, hydraulic monitoring and controlling as well as data acquisition and processing were all involved throughout design, manufacture and support for this project.

Other projects include heavy vehicle chassis design, towing connections, truck and trailer bodies, excavator, roller, bulldozer, grader roll over protection structures, cab risers, falling object protection, operator protection, and body protection for the use of general contractors and for the use forestry applications. Theses projects require design by 2D and 3D modelling, finite element analysis and hand calculations. The forwarding of information to clients requires manufacturing drawings to current and relevant standards.

Working for a consultancy allows me to utilise the knowledge obtained at university and the knowledge I am forever learning in the workplace, combined with the latest software packages and the knowledge of my colleagues to provide my clients with the best solution to their engineering problem.

Working in a consultancy allows diversity throughout my career. With Randall and Associates having fewer than 10 employees we have become adaptable to clients needs. This allows us to become multi skilled in our industry and with customers coming up with more and more challenging circumstances, the expectation for designs to meet their needs grows. The variety of tasks enables me to be forever learning, this is shown by the commitment of the management at Randall and Associates by sending myself and other staff on career furthering block courses to stay one step ahead of the opposition.

When Randall and Associates is approached to solve an engineering problem and I become involved in the solution, a degree of satisfaction and accomplishment is achieved when the project is completed. Direct contact with the clients throughout the projects allows no miscommunication and my job becomes more than just engineering but project and time management. For all this my job never becomes stagnant and the rewards for constant customer approval and satisfaction keep the job enjoyable.

Our engineer duly combined 4 or 5 jobs in the area and called on this client. He examined the truck in question, took a series of photos, measured things up and made a sketch and carried on his way. All this took about half an hour in the yard.

On return to the office, our engineer did a registration check which verifies things like GVM, Tare Weight, ownership, current mileage etc all necessary info needed to certify the truck with. He made toll calls and faxes to the origional designer and certifier of the drawbeam, same to the engineer who manufactured and installer of said beam, He then carried out a series of hand calculations to verify the ability of the bolts and material used. This required a quick CAD drawing to set out bolts etc accurately.

At the conclusion to all this, the engineer provided a comprehensive 2 page written technical report to the owner outlining the failure of the drawbeam to meet the specs and offer to redesign the equipment to meet the required standard. As the drawbeam still had some life left (as determined by the original cert) he also included an invoice to cover the time spent to date, knowing the owner would in all probability wait until expiry to do anything further. The invoice was for a total of 3 3/4hrs or $300( no travel I might add). All in all a pretty proficient and professional approach to the job by our engineer.

You can imagine my bewilderment 2 months, 1 invoice and 2 statements later to receive the clients call berating both the engineer and the company for charging so much for so little etc etc etc. My travel through the job file and talking to the engineer involved only told me that the engineer had done everything to give the client a frank professional diagnosis and a report that he could use anywhere in the future to rectify things. I complimented the engineer involved on his thoroughness and professionalism.

Sitting at my desk, getting more and more niggly as the day wore on, I wondered what this client expected of us and how he related to say his Doctor. I can imagine this guy going to his Dr with a bellyache. First off he has to go there, (no house visits these days), then he has to pay $70 for a 5 minute consultation (work that hourly rate out!!) and gets told to take an aspirin and a prescription to eat Quik-eze. You can guarantee the quack does not get a report from the patients mother (the manufacturer), or his father (the designer), [He may not have one of these on second thoughts] bet there were no photos of the affected area taken, no bolt check to verify if his nuts were loose and certainly no report given to explain that the curry the client had 2 days ago or the 6 Tui stubbies he had last night did absolutely nothing to relax a diameterly challenged sphinctre muscle. What if the Dr was wrong and it was only a tummy full of gas- would there be a stoppage of payment?- No-o-o-o-o sir, not silly Dr has it in bank already.

Same thing would apply if said client took his truck to the mechanic (notice the “took”)- again no house calls here either, the job would be passed to the apprentice who mysteriously gets charged out at A grade rates even though he knows diddely squat, can’t even spell camera let alone use one these days (such is the state of our education system-they do teach them different things though, we learnt to mow grass they now teach them to smoke it for gawds sake) Things are charged for that are not replaced, rag spanners tighten leaks etc.

In both these instances, I venture, this same client pays quietly but begrudgingly and carries on with life. WHY then does the poor old engineer cop all the flack from disgruntled customers. The engineer makes house calls, ensures everything complies with legislation, materials comply with design specs, provides an interest free overdraft facility to creditors and a self taken time payment service as well. He endeavours to keep his clients operating so they do not suffer financially, doesn’t go off to golf every thursday etc and generally tries his damndest to keep his costs down to clients.

SO WHY MUMMY, IS THE ENGINEER TREATED DIFFERENTLY?

We invite and encourage comments. If you would like to comment on this post - or suggest a new item for discussion, please click on the (No) Comments link below. It’d be great to hear what you are thinking!

Trucks are driven fundamentally different to cars, in that that they are almost never driven on their brakes - almost always coasting to a stop, and only being applied in an emergency situation or final stopping. Powerful electromagnetic, or hydraulic, or less common now, exhaust brakes, provide the majority of the retardation required for a heavy motor vehicle (hmv).

The new brake rule was fully implemented on the 1st July 2008 - basically the idea of the rule is that a hmv individually or in combination must be able to stop efficiently whether empty or fully laden. The rule has no grandfather rights, meaning ALL hmv’s modified now must comply with this requirement.

Things such as wheel base alterations will require certification to the brake rule as the amount of weight transferred to the vehicle’s front axle will change under stopping. The difficulty is that in order to achieve certification to the rule, almost all vehicles (if not all) will require either load sensing brakes or ABS - meaning a considerable additional cost when modifying a vehicle. The same will also apply for the fitting of a drawbeam if trailer brake gear does not come as part of the truck package.

From what I have seen, from the 1st Jully the fitment of new drawbeams to old trucks has stopped, so also has wheelbase alteration or axle configuration alterations.

If you are going to purchase a second-hand truck, REALLY IMPORTANT - select a vehicle which is the closest fit to the vehicle that you need - don’t expect, as of right, to be able to alter the vehicle afterwards.

If you plan to modify a truck for whatever reason, VERIFY FIRST that the brakes are able to be set up to comply with requirements. I do not know whether it is possible to fit ABS brakes to all makes & models - I have heard figures of 5k for ABS truck kits, then there is brake relining & certification on top of that.

From our point of view, the cost of certifying a brake modification for a new vehicle with information from the manufacturer is $750 - for a second-hand vehicle, our best estimate is $1500. Based on workflow prior to July 1st, we would have anticipated a couple of wheelbase alterations to old trucks & a few drawbeams fitted to second-hand Japanese imports. Since this date, we have seen several new vehicles, but no inservice vehicles.

What does this all mean? I suspect it means the end of truck modifications as we used to know them.

Truck handling systems, like cars, have become more sophisticated and the vehicle brakes are an active component of the vehicle’s safety system - and this cannot be altered willy nilly.

Whether, when all factors are considered this added compliance burden will be beneficial to the NZ economy as a whole (and, in my view, this is the real question) - I don’t know. I am aware that the most fundamental problem for inservice heavy motor vehicles is whether the brakes operate at all and this has to be addressed first.

Are we simply becoming busier and busier doing things that the world doesn’t care about?? The cynic in me says there is a risk that active vehicle safety systems for trucks will only guarantee that the crashes, when they do occur, will be at worse because they will be at a higher speed. Driver’s have to drive within the vehicle’s limitations and not use these new active safety systems for getting from A to B quicker.

We invite and encourage comments. If you would like to comment on this post - or suggest a new item for discussion, please click on the (No) Comments link below. It’d be great to hear what you are thinking!

Thanks to a wonderful Vision Manawatu course run by internet marketing guru Hamish Clark, we’ve embraced the exciting world of blogging and our staff members will be busy blogging their experiences and opinions of the latest in the world of engineering - and beyond. To get them started I’ve told them they can write a bit about themselves & their hobbies etc., so you never know what you’re going to learn about. Make sure you keep coming back regularly to find out what they are up to, and make sure you add your comments and questions to their posts.