What is wrong with the excavator?

Introduction

This story started when my son, who now has majored in scientific computing, started laughing when he heard that the efficiency of construction machines is measured in weight and not by capacity. At that time he had experience from operating an excavator and thought it was quite idiotic if one should compare for example a computer by weight and not by performance. Since I have been an excavator designer, and therefore have very good knowledge of the forces and strains excavators are exposed to, I wanted to evaluate the present excavators. That became both an interesting and scaring study seen in the light of the present need for more efficient machines and less CO2-emision.

History

In 1839 Otis got a patent on the steam shovel which is the predecessor of the excavator. The first machine was built on a train chassis and was a “partial-swing” machine since the dipper arm could not rotate 360 degrees. Temporary rail tracks were laid by workers where the shovel should to work, and repositioned as required.
Steam shovels became more popular in the latter half of the nineteenth century. Originally configured with chain hoists, the advent of steel cable in the 1870s allowed for easier rigging to winches. Like in all other machines the steam engine was replaced by internal combustion engine by the beginning of the 1900-century. In the 1950s the fully hydraulic excavators appeared, and now they are quite universal.

Steam shovel
An old steam shovel. The picture clearly shows boiler, water tank, winch, main engine, boom, dipper stick, crowd engine, wheels and bucket.

What are wrong with the present excavators?

In the last 30 years no big changes have been made. The machine has approximately equal weight in comparison to the work it executes. The weight of the excavator is more than 15 times as big as the weight of the mass it can lift and the efficiency of the excavator is practically speaking unchanged.
I believe that this is due to the unfortunate circumstance that the excavator only is measured by kilos machine and engine power. It is therefore very little momentum competition between the competitors to increase the efficiency as long as you the buyers evaluate the machines by weight and not by what the machine in fact executes. While for example milling machines have increased the performance 50 times during the last 30 years, the performance of excavators has been standing-still. Can you excavator owners really afford this stand still? And what happen if your competitors suddenly get more efficient excavators. What then? Let us start to look at some of the largest weaknesses and limitations with the present excavators. All the producers make presently about equal excavators.

a. To heavy excavating sticks, booms and buckets.

The comparison of excavators by weight is after my opinion a misery for the entire construction business. That makes it completely uninteresting for the manufacturers to produce efficient machines. If only the excavators are heavy and have large engine power everything is well. They don’t need to exert themselves at all and the machines show signs of that. Especially if they in addition get away using brand names as an argument for you to buy their machines. This has worked excellent through numbers of years and as long as you users think that this is excellent, they will continue doing so, but it is something you should think of next time you are about to buy a 30 metric tons excavator that if ideally optimized, could do the same excavating job as an excavator that weights 10-15 metric tons. You could have saved $ 200 000 of the $ 420 000 purchase sum and up to $ 400 every day in fuel (almost the whole driver’s wages). You could save lots of expenses when you want to move the machine from one place to another and you could radically reduce the CO2-emission to the nature. Or is the earnings really so big in the construction business so that this doesn’t mean anything to you?
”But this is not possible without reducing the wearing quality. That we know based on experience from several decades of producing such machines” the present producers will for sure say. ”Several decades with stagnation in excavator development”, I will then reply. I have personally modeled, designed and calculated lots of excavator sticks and excavator booms that proved to stand thousands of working hours and therefore for sure know what types of forces and strains they will be exposed to. I am quite convinced that by taking totally new construction solutions in use, the digging stick that presently weights 1500 kgs to a 30 metric tons excavator can be constructed with a weight of 500 kgs. Equally, for the excavator boom that presently weights 2500 kgs. By utilizing a quite new digging boom, solution we will for sure be able to save 1500 kgs steel here as well. I am also sure that we can reduce the bucket weight with up to 500 kgs if we here go much more for optimizing the bucket weight and use even better steel materials in the buckets. If we save 3000 kgs weight on bucket, stick and boom, we can in addition save 3000 kgs in counterweight.

b. To large engine.

“The excavator’s engines are so energy efficient”, the producers writes, and thereby try to give the impression that they are resource and environmentally concerned. I will make a little calculation sum on this that the producers should have done long time ago. A common ”30-metric tons excavator” presently has a bucket with “normal” digging volume of approximately 1.4 cubic meter when you shall dig normal earth and gravel. To hoist this amount of gravel with the present excavators lifting speeds you need an engine power of 34 hp! (25 kW!) How large is then the engine in the present excavators? Over 200 hp (150kW). 6 times the maximum that theoretically is needed. That is 6 times to large fuel consumption in comparison to what is theoretically needed for you as a user. It is not strange that you need a 500 liters fuel tank. Still the producers brag of how they think about the environment, emission and resources. To me, it seems almost a bit impudent.
One of the reasons for the large engines is that one must have the power to lift the heavy digging sticks and booms. Power that only is choked away and turned into heat every time the digging bucket is lowered and that again must be cooled away in expensive radiators. When the excavators become equipped with a system that is balancing the weight of the digging bucket, stick and boom you do not need engine power to lift these parts of the excavator any more. You only need engine power to break loose and lift the mass of the gravel.

c. Heavy and expensive excavator frames.

It goes almost without saying that the excavators must have large and heavy frames when you must have so heavy digging sticks, booms, engines and counterweights, but also here the problem that the excavators are sold by weight appears. It is not much inspiration for the producers to optimize the excavator frames as long as the customers find it all right to pay more for the machine, only because it weights more. Therefore the producers do not optimize the frames either. The weight of the excavators should be halved.

d. What about the caterpillar undercarriage.

I can just repeat the arguments from the last chapter because they are the same, but in addition it is reasonable to look at other conditions here. For example the running speed, that barely has changed the last 30 years, but in the way you use the excavator today it would in my opinion be very favorable if the maximum speed was increased from the present 3.1 mph (5 kph) to 6 mph (10 kph) or preferably to 9 mph (15 kph), that is normal dozer speed. That would make the excavators much more efficient and flexible. In addition, in my opinion, a new caterpillar design should have been taken into use years ago because the present is far from optimal. It looks here as if we are stuck with the historical heritage from earlier machines where it does not matter if the excavators move so slowly.

e. The hydraulic system.

When the pilot control took over from the direct controlled hydraulic valves in the 1970s, changes have hardly occurred changes in the excavator hydraulics. 30 years without improvements is a long time when you look at the rest of the world with computers, mobile phones, parabolic antennas, home entertainment systems etc. I feel that the time is overripe for quite a new thinking when it comes to hydraulic solutions and controls. They must be optimized, made cheaper and more energy efficient to quite another extent than today. We can not only sit down and produce and choke away engine power through choking valves as everyone does now. It is quite unbelievable that it still is possible to make so old fashion machines. We want to change this.

f. Lack of continuous gear boxes.

In the future, one has to take continuous gear boxes into use between engine and pumps, also in excavators due to several reasons. This way you can optimize the engines just from engine power. The engines will then be much more optimal because you can forget the importunity of the engine torque. You will get a considerably less diesel consumption and engine wear, because the engine only rotates with the speed that is necessary to produce needed power at all times. I feel sadness by hearing all the machines racing their engines at full speed only to keep the speed high, when the same speed could have been obtained by higher gear ratio and low engine speed. It is at least not good for the engine. In these times with far too high CO2-emisions this must be changed.

g. Less soil pressure.

When the machine becomes much lighter it will also be better to drive on places that can stand less pressure on the soil, or that can slide away if the weight of the machine is to heavy, and it is just on this places you have to dig with an excavator. We also wish to improve these qualities by doing other design changes, but many of these changes are either patentable or easy to copy by competitors and therefore we do not want to explain how these solutions are yet. That will come as a surprise.

h. Better working environment.

Even modern excavators have to poor working environment with lots of noise, and they are still equipped with to poorly made dust filters. It is far too little noise dampening even on modern excavators and the engine is hardly separated from the driver’s cabin. This is the situation 30 years after that mobile compressor got noise restrictions. A more separated solution between engine and driver is absolutely necessary and one must have far better noise isolation of the engine room.

Less running expenses and investments gives increased profit.

How much more you could earn if you got the possibility to change to a more efficient excavator with half the price, half the weight and 50-90 % reduced fuel consumption you can of course evaluate yourself, but it will be a lot when you sum up everything, and there is no reason to believe that the demand of productivity will be reduced in the future.

Reflections

While I was been working with this article I have often pondered how the producers of machines to the construction business have been able to such a stand still even if the development in many other areas have developed at a furious pace. It must have something to do with that the customers have not been enough demanding. Therefore it maybe had been time for you customers to carefully think through if it is in this way you want it or if it is maybe time to carry less of your gross income directly to the machine producers. Maybe you need the money better than them since they hardly care. You are almost all the time told through advertisements and brochures from the large producers that the machines are almost perfect and they obviously reckon that there will not be made questions to the construction machines excellence. The producers have probably reckon that the construction machines are like holy cows on which nobody makes question marks to, and therefore feel quite safe, are going the pace and reckon that if they only increase the size and change the color a bit then everything is all right. Maybe this is the development that follows when the producers presently are owned by investors and investment companies that not primarily are guided from how they can make the most optimum machines, but from how they can earn as much money as possible with as little effort as practicable.
Besides, I also think that contractors that continue to buy old fashion machines that consume far too large amount of fuel and that emit several times to much CO2 will get a major problem with the opinion of other people. They will be regarded as someone that gives a damn if species like the polar bear will be exterminated.

What now?

We have become more and more tempted to start production of this new generation excavators ourselves because we then can build the new production from the basic. Excavators are in the reality very simple machines from a construction and calculating point of view. Therefore we have started with the development of the first model of this new generation. We believe that no customer can resist all these advantages that are possible to achieve with this new solution. We are convinced that it will oust the present excavators because I have participated in ousting two other products that relatively seen was just as old fashion so therefore we will manage this as well. One thing is for sure. If the development of mobile phones followed the same pattern as construction machines everybody would still have 20 kgs mobile phones today.
If you maybe are interested or have views, please contact us on email:flaco@fladby.com. Flaco’s internet is: http://flaco.fladby.com

© Tron-Halvard Fladby/ 24.5.2007