Hydraulic Spreaders and More Useless Numbers

The latest addition to the Dunbar household is now four months old and there are nights when young Jessica is not as fond of sleep as her parents are. Inevitably the TV goes on and we spend an hour watching home shopping channels whilst our young daughter decides it's time say good night (again). The claims made on these channels are ludicrous and have been for many years, which tells me people actually believe this nonsense, but they buy stuff and as a consequence, the channel stays on air; amazing! These insomnia driven episodes have inspired me to follow on from my previous blog which talked about the importance of getting 'behind the numbers' associated with hydraulic cutters and focus on actual performance.

Spreaders and Hydraulic Forces
Well now, let's look at spreaders, but before we do, it is important to understand how hydraulic forces work in relation to hydraulic spreaders. If you stand up straight and stretch both arms out in front of you with the palms of your hands together (now you look like a spreader) and slowly open and close your arms (as you would do with a spreader) do you know where most of the force is located and in what position? Well you may be surprised to know that the most force you can exert with your arms is right near your shoulders when your arms more than halfway open. In terms of hydraulic forces on your spreaders, this is exactly the same.

Misleading Claims
The thing is though, how often do you use the hydraulic force located at the bottom of the spreader arms, near to the control handle with the spreader more than halfway open? That's right, NEVER! But you will see some spreaders advertised with a 'Max. spreading force at base of arm' of over 350 tons; this kind of claim belongs on a shopping channel.

Have you ever seen the base of the spreader arms being used for spreading? Know the difference between theoretical and useable spreading forces!

Theoretical vs Useable Spreading Force
You see there is theoretical spreading force and useable spreading force. Theoretical numbers, just like cutters, can be astonishingly high but have absolutely no relevance at all. It therefore follows that the highest number will often be considered as the best and strongest tool, when in fact this can be completely untrue. It is vital that users and purchasers understand fully the norms that cover these tools, because (as I said in my last blog) we are predisposed to being impressed by large numbers. Some manufactures claim that this theoretical spreading force is useable, when it isn't and never could be.

Spreading Forces Specified by the Norms
You will see two types of norms when it comes to double acting hydraulic rescue tools and this depends where on the planet you are. Either the EN 13204 norm or NFPA 1936. The EN norm actually specifies the minimum spreading force 25mm from the tips. This makes it easy to compare spreaders. Remember this is (in the vast majority of cases) the position in which you will start your spreading process, so this figure actually means something. In the NFPA test the tool's spreading force is measured 25mm from the end of the tip and at 10 uniformly spaced points, ranging from the closed position to 95% of the maximum opening. The value of the highest point is referred to as the highest spreading force (HSF) and the lowest point as the lowest spreading force (LSF).

Conclusion
I cannot emphasise enough just how important it is to fully understand how hydraulic equipment works and how it is rated. You must be able to then take that knowledge and understanding and apply to to its operational use. I have spoken to many people who have purchased based on the high numbers alone; not a great move. At the end of the day hydraulic rescue equipment is a large investment and it requires careful consideration. See through the numbers, understand the norms and most of all appreciate that most of the forces advertised in association with hydraulic spreaders are simply useless and misleading, just like TV shopping channels.

As ever I welcome your feedback!

Ian Dunbar


Cutting Performance Theory vs Reality

When it comes to assessing performance, we are generally predisposed to being impressed by big numbers. Whether this is the megapixels on our new camera, the top speed of our latest car or the screen size on the new TV; big numbers attract and hold our attention. We must, however, look beyond the headline digits, especially where it is only a theoretical figure. In this instance, I am referring to the maximum forces attributed to hydraulic rescue tools.

In another blog I will look at hydraulic spreaders, but for now let's focus on cutters. The maximum cutting force is without doubt the first consideration for most people when it comes to choosing cutters and is generally at the heart of a purchasing decision. Of course, there are other considerations such as build quality, weight, ergonomics and other unique features but once the conversation regarding those has ceased, it always comes back to cutting force. The question here is: what is cutting force?

Maximum theoretical cutting force
Here we go; maximum cutting force is 100% theoretical. This is because it is the result of a calculation relating to the cylinder (or piston) cross sectional area, multiplied by the pressure at which the tool works e.g. 720bar (10400psi). It is also important to understand that the maximum (theoretical) cutting force has nothing to do with the blade design, shape or geometry. Actually, if two identical cutters were placed side by side with one having standard blades and one having blades made out of wood, they would both have exactly the same maximum theoretical cutting force. So, you should now begin to understand that there is far more to the performance of hydraulic cutters than a theoretical calculation which results in a big number.

There is more to cutting performance than a theoretical calculation resulting in a big number.

Cutting performance
The real test of a cutter (or any hydraulic tool for that matter) is the actual performance. This can only ever be assessed with the tool in hand and on a late model vehicle. I have previously explained that although there are still many older vehicles on the road, the true test of modern hydraulic rescue equipment, is their performance on new cars. It is only when a cutter is used on such vehicles that an assessment of its performance can be made. In use, its weight, ergonomics and blade geometry all become apparent. This because we hardly (if ever) use the tool at waist height in a neutral standing position; we mostly use them above or below waist height. Blade geometry has more of an impact than you may think. The blades are (of course) your point of contact with the vehicle; they will determine how effective the tool is at penetrating and surrounding cuts and they will influence any tool movement during the cutting process. Remember too that how the blades are mounted to the tool, i.e. inclined (see pictures below), may provide increased ergonomics and safety.

Working with the Holmatro Inclined Cutter offers you increased ergonomics when cutting high or low on the car and more room between the tool and the car (read: patient!), e.g. when making a relief cut in the A pillar.

Residual capacity
It is also useful to actually assess how 'hard' the tool is working. This can be achieved by placing a pressure gauge between the pump and tool. This is important as it will give a visual indication of residual capacity. That is to say that if a cutter performs a cut on a modern-day vehicle using only 50-60% capacity, it has lots of reserve capacity in the event of increased vehicle strength in the coming years.

EN and NFPA norms
The other thing to keep in mind when looking at hydraulic rescue equipment is the norms which they conform to (EN and NFPA norms). These are industry tests which allow comparison to be made between manufacturers. These norms test hydraulic cutters on steel profiles such as round bar. I would urge you to ask yourself how relevant these tests are when considering the actual 'real world' use during vehicle extrication. Vehicle profiles are very different from round bar.

Conclusion
It is very easy to be drawn to and impressed by big numbers and in many things in life it is very often what we look for when making a purchasing decision. However, having an understanding of the numbers sometimes attributed to hydraulic rescue tools, how they are calculated and their operational relevance (or lack of) will allow you to make a more informed decision, by focussing on 'real world' performance rather than any theoretical figure. Appreciating that the cutting tests performed for norms only rely on steel profiles rather than vehicle construction means that a real assessment of a cutter's performance can only be made by using it for its true purpose.

Put simply, whilst numbers are interesting, compared to actually using the tool, they do not really tell you a great deal at all.

As ever I welcome your comments!

Ian Dubar


5000 Series Telescopic Rams

crossramming with Holmatro telescopic ram

Lighter and more ergonomic than ever, improved performance.

Lightweight

Lighter than ever, thanks to new materials and component integration. Easy to carry and handle, reducing physical strain.

Ergonomic carrying handle

Balanced carrying of Holmatro telescopic ram

New design for balanced carrying of your ram. Mounted parallel to the tool, minimizing storage dimensions.

Improved performance

Holmatro telescopic ram has more force in 2nd plunger and more length

Increased spreading force of the second plunger (where you need it the most!) and more length to expand your options during extrication.

Integrated laser pointer in ram head - Patent pending

Holmatro telescopic ram with integrated Laser Pointer

Marks the exact spot where the ram head will contact the vehicle once extended. Facilitates first-time-right
positioning, which saves time and is safer for the patient.

Integrated LED lighting

Holmatro telescopic ram with integrated LED lighting

A total of 6 LED lights illuminate both the plunger side and the base side of the ram, giving you a clear view of your working area. Day or night: start right away without being hindered by your own shadow.

New control handle

Holmatro rescue tool control handle offering better grip

Improved ergonomic design, offering better grip for optimal tool control.

Built-in Speed Valve

When unloaded, the plunger extends quickly to the desired distance to speed up positioning of your ram.

Greenline EVO

New Greenline EVO range

The next evolution in battery-operated rescue tools

Holmatro introduces a new generation of battery-operated rescue tools which are faster than ever, without concessions on performance. The range is named Greenline EVO and consists of three cutters, three spreaders, four combi tools and two rams.  All Greenline EVO tools offer up to 33% more speed, delivering the same performance in less time.

Greenline features & benefits maintained

Next to a higher tool speed the new EVO range still offers all benefits of our existing Greenline concept:

Self-contained

  • For optimal freedom of movement
  • Rapid deployment: simply press the start button and start working

Latest lithium-ion battery technology

  • Long battery life combined with high capacity for maximum operational use
  • Low self-discharge rate, no memory effect
  • Suitable for use at high altitudes
  • LED indicator to check battery capacity left

Battery on top of the tools

  • Quick and easy to change, even in narrow spaces

Emission-free

  • No fumes: healthier for rescuers and victims
  • Ideal for use in confined and/or underground spaces
  • Environmentally friendly

All weather proof

  • Suitable for use at below zero temperatures, down to -20°C / -4°F
  • Suitable for use in wet weather conditions

Control handle centrally positioned on the back of the tools

  • Always within reach
  • Tool can rotate freely while your hand stays in the same position

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