The Randall & Associates Ltd Process:

1. We both need a requirements specification. If you don't have one, we'll help you generate one. (No Charge)

2. We provide you with a free estimate (No Charge)

3. You decide that's great! Lets get together.

4. We visit you on site if needed and we talk to you some more about the job.

5. We provide a full written brief of the job, and if it feels right, you sign a contract to allow us to start the work.

6. Sit back and relax, knowing we're on the job!

OK, well why do you guys think you're so great at this?

At Randall & Associates Ltd, we pride ourselves on being industry leaders in the design of ROPS frames. We use the most up-to-date versions of finite element analysis software sourced from the USA (ALGOR).

Our staff have assisted the Department of Labour in their development of a Code of Practice for the use of ROPS frames in New Zealand .

Randall & Associates Ltd ROPS frames are in use all over New Zealand with over 1200 frames carrying our certification.

"Courage is doing what you're afraid to do. There can be no courage unless you're scared." .
Eddie Rickenbacker

Portfolio > Roll Over Protection Structures (ROPS)

HOW RANDALL & ASSOCIATES LTD CAN HELP YOU

How we can turn your problems into opportunities!

Roll Over Protective Structures are known as ROPS frames. They are built on heavy machinery to prevent the operator sustaining life-threatening injuries in the event of a machine roll-over.

These structures have an interesting requirement in that they need to be strong enough to take the force of an impact, but supple enough to bend so that they inhibit the machine from just bouncing off the frame and making the roll-over worse.

In 1996 Randalls became involved with ROPS after an enquiry from Motor Holdings Komatsu about providing designs for the range of machines that they were currently marketing.

The challenge at this time related to the fact that all of the existing standards were performance related, and therefore in order to demonstrate compliance with computers required “event simulation” requiring a side load to be applied to a certain load level held (no movement) then the side load increased until the frame had absorbed amount of energy (force times distance) once again held (no movement) and then to THE DEFORMED shape of the frame apply a vertical load and held (no movement, finally apply a longitudinal load to the deformed frame and held (no movement). This type of analysis required non linear event simulation analysis.

Non linear analysis is required where something moves in a non linear fashion—such as steel once its has reach its yield point. With linear analysis you put a load on something and it moves says 10mm, you know of you double that load then it will move 20mm—if you take the load off it will spring back where it came from.

With non linear you apply an incremental load it will move a certain amount, if you apply another increase in load it will moved a little bit more but BASED on its last position. Take the load off and it springs back a little bit—not all of the way

The computer will take into account strain hardening, it will take into account what portion of the through thickness is in yield and what potion is behaving linearly. If you model too coarsely the computer results will be wrong, if you model too fine the result won't converge. There is a tolerance set inside the computer than says that the next iteration can only be so far as far as movement goes as the last result, some times it ping pongs all over the place and the computer gives up (non convergence) . Non linear is also very sensitive to boundary constraint (to accurately predicting how things bend plastically you must accurately model what they are attached to), you have to include an adequate portion of the machine structure in the analysis to get the analysis right ..

Still there is more, computer analysis only provides an indication it does not provide bench marking. We were fortunate at the time to be involved with Cullimore Engineering who had made for may years the “Roll Master” brand of tractor ROPS. This were physically test at Lincoln University and the frames were kept (some of them anyway) by Cullimore for future reference for new designs . These provided the initial bench marking for the computer analysis. (Cullimore told us it took on average three goes to get a compliant design and each test from memory about $5000. As the tests were always done with the ROPS mounted to the tractor, there was always the risk of damaging the tractor)

Linear analysis requires only one computer iteration, the type of analysis required for ROPS analyses requires at least a 1000 iterations per design iteration and initially took us three iterations to get the design right

So back in 1996 when 4MB on a computer was large, 500MB hard disc was large an iteration which now takes a couple of minutes took half an hour. We had three computers running flat out and it took two to three weeks per analysis!.

The original safety frames were based on RHS and were unattractive. Frame designs became more complicated starting from “off the shelf” RHS to fabricated RHS with square corners, to fabricated RHS with rounded corners to fabricated RHS with corners profiled out of plate.

All the while we were building a dossier about the functional aspects of excavator ROPS, about what the operator liked/ disliked, ditto for the mechanics,, ditto for the fabricators, ditto for the frame installers. We were also building up a dossier about how the frames performed in accident situations like rolling several hundred meters down a bank, having a giant macrocarpa tree fall on the machines, rolling over on hard surfaces, rolling over on soft surfaces, falling off trucks, falling off load ramps, hitting bridges whilst on a low bed.

In 1998 Martyn DeLiefda (employee of Randall and Associates ) came up with the idea of constructing a safety frame out of solid plate and sold that idea to Eaststeel who immediately could see the aesthetic advantages offered by what was essentially free form design.

It took Martyn about 5 months of work to come up with that first trail blazing design in solid plate ROPS. It took that long because when you use a computer you have to be able to bench mark what you design, and being trail blazing, we had no past history to base decisions on. We had to verify by several different computational approaches and rational engineering analysis that what were doing was correct.

Over the next 12 months or so RHS frames became a thing of the past and from then on we developed free form plate frame structures.

We have design and certified 1000's of frames and have hundreds and hundreds of frame designs with analysis covering exactors for Airmann, Caterpillar, Daewo, Hitachi , Hyundai, JSW, Kobelco, Kato Komatsi, Caterpillar, Liebher, Samsung, Sumitomo, Tackiuchi, Volvo and Yanmar

Our list of frame design for rollers includes, Bomford, Bro, Caterpillar, Dynapack, Hitachi, Hamm , Kawasaki , Komatsu Saki and range of others

Our list of machine types includes haulers, compactors, dumpers, graders, loaders ,scrappers, skidders, tractors

SOME FACTS ON ROPS FRAMES:

SAFETY FRAMES - Did you know......

• That the best ROPS frames are designed for a particular machine weight and to absorb a specific amount of energy (through permanent deformation of the steel)
• The momentum of the rolling machine is the absorbed energy and that reduces the probability of the machine rolling through more than 180 degrees
• That the FOPS test object is a 200mm diameter steel cylinder weighing 225kg. Its end impacts the structure after falling a distance of 5.2 metres
• That the OPS protection test for quarrying, demolition and general contracting machines is similar to the FOPS test
• That the OPS test loads for forestry machines are rather less, but the requirement to prevent intrusion by objects greater than 48mm diameter is difficult to achieve
• That a ROPS frame is one-shot device? Use it hard once and throw it away.
• That one of the most high rollover risk machines is a steel drum asphalt roller
• That a well designed ROPS will assure the safety of a seatbelted operator when the machine rolls about its longitudinal axis, 360 degrees or less, down a hard packed clay slope at an angle not greater than 30 degrees
• That a considerable variation of ROPS structural details is possible. Not all forms and details are suitable for all work environments. Know what is your ideal and try to get a ROPS specified close to that.
• That visual appeal is important and helps the machine owner create a professional image for the company
• That the difficulty of designing a ROPS varies with the size of the machine. 12 to 20 tonne machines tend to be the easiest. Small machines are often difficult because there is little space/structure to which a ROPS can be attached. Large machines are difficult because the loads are very large.

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Some Cool Examples of our ROPS Work