The bulldozer


In my study of construction machines the turn has now come to the bulldozer. I think that in these times with focus on emission, environment and use of resources, it is very important that a critical study of these types of machines is done on quite free basis to evaluate the state of the technology as it may be called in patent terms, because I see that someone have worked themselves into a corner when it comes to engineering of construction machines.


The first bulldozer was invented by James Cummings in USA. He had observed that while the actual digging of the trench had been mechanized, backfilling the trench was still being done with mules and dirt slips. He realized that a machine for filling the trench was in order and developed therefore the very first bulldozer existing of a tractor and a blade that he in 1927 applied for patent. The tractor he used, as you can see in the picture of a replica of the world’s first bulldozer and the patent drawings, was a Fordson with 2 gears forward and a top speed of 7 mph (11 km/h). The name bulldozer is a combination of bull and a very powerful medicine doze.
The bulldozer was later built with a caterpillar tractor as the basis and got the shaping it has today for approximately 50 years ago. After that it is broadly speaking only the weight and size that has increased.

A replica of the world’s first bulldozer built on basis of a Fordson tractor as it is displayed in Morrowville in USA.

What ought to be done differently on the future bulldozers?

After nearly 50 year with the very same concept, I am convinced that it is definitely time to take a new look at the bulldozer with fresh eyes. I am, in fact, very surprised that this has not already been done.

a. Double speed

I will start with the bulldozer’s speed. The world’s first bulldozer had a maximum speed of 7 mph (11 km/h). What have then all the present bulldozers as maximum speed? Believe it or not. All the new bulldozers today have the very same maximum speed as the worlds first 80 years ago, only 7 mph (11 km/h). You do not find any other business or trade where the machines have not got higher speed than the world’s first specimen when the product is so old. And it does not end there. The engine power in the newest and largest bulldozers has been reduced with 40 % in proportion to the weight when we compare with the first bulldozer in 1925! And you are satisfied by this? The producers even swagger about the machines. Especially bad is this because if the machines had worked with double speed of the present then you would have done the same job with half the machine size and half the investment. A 50 metric tons bulldozer would then do the job that a 100 metric tons bulldozer does today, even without any other improvements than doubling the working speed. For the largest bulldozer we talk about investment savings in the amount of 1 million dollar. And it is not exactly high speeds we bulldoze with today. It is only 1.2mph (2 km/h) to 3.1mph (5 km/h). 2.4 mph (4 km/h) to 6.2 mph (10 km/h) is therefore also easy manageable speeds. And imagine how much more fun the machine had been to drive. I am convinced that recruiting of new good drivers also will be simpler when the machines become more dynamic, and they get much more done with them.

b. Complete continuous gear boxes

In the future we have to take in use complete continuous gear boxes for several reasons. Larger working speeds demand that you can increase the speeds from 0 to maximum much more flexible and that the maximum speed is much higher so that the bulldozer can move much faster with much lower engine speed. It must be a possibility to let the engine speed slow down to a lower speed when the power requirement does not demand full engine speed. In this way we can optimize the engines only from engine power. By using complete continuous gear boxes and large range in the gear ratio, the engine torque is without significance. You get considerably less fuel consumption and engine wear because the engine only rotates with the necessary speed to get sufficient power. It is bad to hear that all bulldozers have to race the engine only to keep the speed when the same speed could have been reached by lower gear ratio and lower engine rpm. How often do you drive your car at full speed with unloaded engine? It is at least not good for the engine. In these times with all too high CO2-emmisions this must be changed.

c. Lighter bulldozers

By improving the bulldozer technology in many other areas it also will be possible to halve the weight on the present 50 metric tons bulldozers to approximately 25 metric tons. This can be done, among lots of other changes, by shaping the blade much more optimal so that the blade weight can be reduced from the present 6500 kg to 2000 kg. That will mean that you can carry 4500 kg extra mass every time you move forward with the bulldozer. 25 % increase in the dozers working capacity. Further you are spared from carrying 4500 kg useless steel backwards every time you reverse. Through the bulldozers lifetime it sums up to a lot of saved fuel and emissions in addition to that you do not have to buy all that useless steel. But when the present producers only want to get the machines as heavy as possible because the machine sizes only is fixed by weight and not from what they really do it will of course end up this way. How long will you customers let you seduce in this way? You can get the pressure on the tracks in a better way in stead by shaping the blade in such a way that you get weight transfer of soil to the tracks in stead of only using dead steel weight from the far to heavy bulldozer blade. Do not get fooled by the producers. They say that this is necessary to get the blade strong enough. Demand in that case the calculations that shows the necessity of it because if the producers had that, they would by their own observation be able to see that this is a large bluff because the strain that the blade is influenced by are easy to calculate.
Complex old fashioned track system is the next. Large dirt collectors quite without elegance. Here it is possible to do great improvements so that they can stand much larger speeds and where the parts are much more protected against soil and stones. The tracks should consist of considerably fewer parts and get much less weight, wear and price. Military tanks with tracks can today, as a comparison, drive at speeds between 35 mph (60 km/h) and 60 mph (100 km/h).
Much better layout. Few other products today looks like an occasional pile of plates. How can you be impressed by such machines? By a careful survey of the bulldozer solution the whole design can be made much simpler. As an example, look at the engine room. Gigantic. If you look into the engine room on very well-known brands, you can see that there is much spare space over the engine that you maybe can throw your hat through the machine. And this impresses you customers. It gives at least huge engine covers that cost you money and obstruct the view.
So, we are over on the bulldozer frames. They can be made much lighter and better and above all much cheaper to produce. That in fact should interest you as customers. Therefore it is clear that 50 metric tons bulldozer can be built with a weight of 25 metric tons. That will in this case mean that a new generation 25 metric bulldozer can do the job of the ptonresent 100 metric tons bulldozer. Then it really starts to look like something because as always, the price is almost in proportion to the steel weight.

d. Better view

The most important when you shall do an efficient job is to see what you are doing. Everyone that produces combines, wheel loaders and excavators have understood this. Only the ones who design bulldozers have not. Because, if they had, they had of course long ago made a design with the driver’s cabin in the front of the machine, above the blade, so that you could see what you have in front of the blade. Today, you are sitting up to 20 ft (6 m) behind a blade with almost 10 ft (3 m) height and 20 ft (6 m) width. When you lift the blade to top position, the height over the blade is up to 15 ft (4.5 m). What do you then see in front of the blade? Nothing. The driver has no control with what exist in front of the blade. As far as it goes the producers have taken the consequence of this and made the front window as a little peep-hole and covered even more of the view with large exhaust pipes and hoisting cylinders. If the producers made an opposite design, the driver would have had a perfect view. By the way, what happens the day an accident appears because someone get run over because the driver did not see anything. Who is the responsible?


What is it really these technicaly educated engineers have been doing all these years. Think of all the new developments and knowledge that have appeared in these 50 years in many other areas. In the construction machine business on the other hand, the technology has stood still. And maybe the worst of all. It looks like that they who work there have not understood that the machines are old-fashioned, uneconomical and quite reprehensible when it comes to use of resources and fuel consumption. And if there is someone other than the engineers fault, the engineers should give them a lesson and tell them that this can not be tolerated anymore. The technically educated engineers must soon begin to defend a professional integrity. Otherwise no one will soon pay them a decent salary and no clever youth will seek this profession. It is already clear signs that the youth do not seek this profession. When I see such type of machines, I also see that it is quite necessary that it now appears new generations of most types of machine elements such as cylinder connections, couplings between shaft and wheel, pipe couplings, moveable shaft couplings, track chains, couplings between stag and machine, material choice, etc. This is necessary to reduce the material consumption and the production costs, the assembling costs and not least, the inspection costs, service costs and the maintenance and repairing costs.

Reduced emissions

To produce new steel from ore it will be an emission of approximately 3 metric tons CO2 for each metric ton steel. 300 metric tons emitted CO2 to produce a 100 metric tons bulldozer. If we now started to optimize such machines properly, then we would have abundant of scrap steel for a long time and then the emissions will almost disappear because we could produce 4 machines from the scrap steel of one present machine and by use of scrap steel we have quite insignificant CO2–emissions.
Besides, by making so optimal machines with among other things, complete continuous gear boxes for instance, that a 25 metric tons bulldozer will do the same job as the present 100 metric tons dozer, so then the CO2–emission from the bulldozing could be reduced with up to 600 metric tons CO2 every year. That will represent reduced emission of CO2 of up to 6000 metric tons in the lifetime of every 100 metric tons bulldozer. With the problems we now have with the climate and not renewable resources, it is unbelievable that the machine producers have not started with such a development a long time ago.


This time I feel like handing the reflections over to you readers either if you are users, drivers or engineers. I ask you. Try to forget that this seemed to be dashing machines because they are big. Try to look at these machines with fresh eyes. It can not only be me that thinks these machines are hopelessly old fashioned. See how elegant even a garden wheelbarrow is in comparison. How optimum the producers there have utilized the materials and new production methods. Think how much more important it is to make an optimum bulldozer because they use so large amounts of steel in the production, bulldozers uses large amount of not renewable fuel and they spew out large amounts of the climate gas CO2. They can only continue with this as long as you customers do not demand better solutions. By the way, what happens the day a competing constructing firm has understood the point and ordered a bulldozer of the new generation, and you just bought one of the old ones?


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© Tron-H Fladby/ 25.7.2007