The combine harvester


One of the most important machines in the moderen agriculture is the combine harvester. To be able to produce enough food in a rational manner it is important to be able to harvest large amount of all types of cereals very efficient. In 2005 it was harvested more than 2.2 billion metric tons of cereals. This illustrates with all clearness what enormous amount one here must get harvested in short harvesting seasons and these set high demands to the machines. The need for food will continue to grow and within short comes also the wish to produce huge amounts of fuel from grain with heavy political pressure. Then the combines must be even more efficient and demand less energy and man hour to do the job.


The combine harvester is quite simply a combination of a threshing machine invented by Andrew Meikle in 1784 and the reaper invented by Cyrus McCormick in 1834. Picture 1 shows a threshing machine from 1881 and picture 2 shows a McCormick reaper. The very first combine harvesters that were produced were made to be drawn by horses. Later they were made as tractor-drawn, some with separate engine to power the grain separation and in 1938 the first commercial self-propelled combines as we know it today.

Picture 1. Threshing machine from 1881.

What is wrong with the combine harvester?

After so long time with almost the same concept it is maybe time to take the solution to a renewed evaluation. Think of all the new developments in technology and knowledge that have appeared through that period of time. Maybe the combine design is not so optimal any more? How would one model a new combine if one should design a new combine out of the demand from the future agriculture? One perhaps should base it on the present technological possibilities without looking too much on the construction of the old combine harvester. We wish to contribute to design such a new combine by starting a going through of the possibilities and propose solutions here and now.
After having done a careful study of the operation, and the whole technical solution that are mostly used, my meaning about what is wrong can short be summed up like this: Very much. Let us start by looking at some of the largest weaknesses and limitations with the present combines. I will try here to rank them after seriousness.

Picture 2. Reaper from 1800-century.

a. Sieves boxes and grain sieves.

The sieve system on the combine is a heritage from when one used a manual sieve to separate grain from husks. This is a very space demanding system with shaking movements, variable and space demanding air fan and returning system. In the way they are made at present, the sieves must be kept horizontal in order to some extent perform well because their operation are only based on the gravity forces. In order to get this working better on fields with side hill and uphill leveling they equip combines with sophisticated automatic leveling systems in all directions. This increases the complexity and the costs even more. The sieves demand also much knowledge for correct choice and correct adjustments to avoid loss of grains. They have also easy to tighten if it is humid, much weed or earth. It is difficult to prevent earth from entering the combine if it is much straw fall over. Immediately after the dew is falling in the evening the sieves will pack. You must also have much control while working if the loss shall be kept low. Even if the combine only loses 500 grain each square meter (1 grain on a 4 multiplied with 5 centimeter) it sum up to 200 kilos each hectare field for wheat, barley or oats. You maybe seem that this is not that much, but you must have in mind that here all the expenses are paid and with a grain price of 0.2 Euro per kilo this loss will be 4 thousand Euros on a 100 hectare farm. Money straight out of your pocket. In addition the sieves must be changed or adjusted (if adjustable) dependent of the grain type, weight and size. This demand good knowledge and insight if it shall be optimal. Change of sieves after grain type also take time and require ample space.
I am convinced that sieve boxes and sieves can be replaced by better, more compact and cheaper solutions and above all, with much higher capacities.

b. Larger threshing capacities so that the speed can be increased

It should have been put more effort into developing new solutions here because if the speed could have been doubled then you could have harvested twice as much with the same machine. That represents a halving of the investments and labor expenses. This should not be an unreachable goal since all other businesses have managed that and even more. Why shall always the agriculture be an exception?

c. Better header technique so the speed can be quadrupled compared with the width.

At present a lot of effort is placed in foldable headers and removable headers that can be transported on a trailer.
Many find that maybe imposing, but it for sure does not impress me. With the present laser technique, computers, radar systems, satellite navigation systems, on the ground placed navigation systems etc. etc. it for me is compete incomprehensible that one does not go much more for increased propelling speed in stead of only increasing the header width with all the costs that leads to. Maybe there’s the rub. It is probably much easier to demand a sky high price when the combine size is measured in foot header width. Almost just as stupid as that one measure construction machines only on weight (Example 50 tons excavator). This standard should have been replaced long ago and the combine size should have been measured in harvested hectare per hour and tons harvested grain per hour.

d. Unfavorable placing of grain tank and engine.

The manufacturers of combines places the grain tank on the top of the combine in complete contempt for everything that is named centre of gravity, instability with steep fields and driving over unevenness and ditches. As long as you used grain sacks this was not dangerous and on the top of the combine it is for sure always space. The sky is the limit. When you in addition have a large diesel engine placed on the highest thinkable place on the combine it is a matter of course that you cannot drive at high speed when you turn, drive in steep fields or over ditches. With such a high centre of gravity this becomes both dangerous and unpleasant. If the manufacturers should do something about this they must of course think in terms of quite new layout of the combine and it is maybe to much to demand that the manufacturers shall have enough imagination to evaluate the placing of the different component anew. The combine could indeed become more efficient, better and cheaper than competing combines. And they cannot of course, do anything better than their competitors. The competitors could then be ousted and the farmers could get an improved economy.

e. Larger grain tank

The grain tank on the combine should have been much larger so that you got a reduced number of emptying. That would do the harvesting easier because then the driver that transport the grain will get more time between each emptying and thus could have worked more efficient. If the grain tank hadn’t that bad placing, then it had of course been naturally to have it made much larger.

f. Threshing controlled propelling speed.

In order to utilize the threshing machine capacity optimally they should have a computer controlled solution where a computer controls the propelling speed as a function of the amount of stalks and grain. Thus the driver would get better utilization of a costly machine and could utilize the fair weather better. A threshing machine that is evenly loaded with straw and grain will also thresh better with less threshing damage on the grain. Saved money and less cost for the farmers.

g. Variable speed from zero to maximum speed with a quite continuous gear box.

Here we are with one of my favorite ideas, quite continuous gear box. That is a solution that should have been taken into service everywhere because optimal speed all the times gives better total utilization of the machines and gives need for less investments and lower costs, both for fuel and labor. Besides you will be able to utilize the fair weather better. I have invented such a quite continuous gear box. See Internet:

h. Higher transport speeds with less engine speed.

How often do you drive your car engine without load at full speed? The most of us will answer that they do that very seldom. But when the engine is placed in a combine harvester, and one drives on a road, the diesel engine with several hundred horsepower are running at maximum number of revolutions without load in order to get to the destination fairly fast because the manufacturer has equipped the combine with to low top gear. And still there is someone who wonders why combine engines breaks down. The diesel consumption would also have been lower and diesel is after all not free.

i. Gear box between engine and threshing machine.

On for example compressors variable engine speed is in use. That should also of course be used in combines. Because when there are no stalks and husks in the threshing machine, by turning etc. then the need for power is less and then the rpm should have gone down while a quite continuous gear box provided for to keep the threshing machine at constant speed. Then the engine could have been down-sized because it could have increased the power to the threshing by gearing down and increased the engine speed when necessary. The engine could be dimensioned only from power need and not from the engine torque to keep the threshing machine at constant rpm. This would have given less investment in engine. More even threshing machine rpm. Less fuel consumption and more correct utilization of the engine and less noise.

j. Less black painting.

And then it was this black painting. And this time not in transferred meaning. I should have liked to know who that could have hit on something so complete stupid and dangerous as to paint black a combine inside and under the covers where black belts and large disks are running at high speeds. That person can impossible have threshed in the dark and has been in need to see to that bearings are not going hot or look for leaking. That person cannot possibly have had need for changing broken belts or to see if sieves are about to pack with earth or weed. Black color kills for sure all light. And where were all of you other persons that didn’t stop this man with the black painting brush. You should have stopped him. All such places should have been painted in light colors. And don’t blame on the paint price because that is the same. But this is probably due to a vulgar attitude by the manufacturers that this ”stupid” farmers easily can be tricked to buy new machines if they only get some new colors and rounded design on the cover plates. I therefore invite all farmers to speak out and tell the manufacturers where David bought the beer, or at least where he bought the barley to brew it.

Less running expenses and investments gives increased profit.

How much you could earn extra if you got the opportunity to change to a better and less costly combine with higher capacity, you must evaluate yourself. But it will be a lot when you sum up everything and there is no reason to believe that the demand for productivity will be reduced in the future.


In the computer business a personal computer costs approx 1 thousand $ and have enormous much higher capacity than a working station 20 years ago which at that time was priced to 550 thousand $. But the computers are something quite different than agricultural machines and can not be compared will now for sure the agro machine manufacturers claim.

Yes, well, another example. I saw some years ago a new spinning machine for cotton tread. The factory also had an old spinning machine that was running by the side. The old was a noisy huge ”thresher” that they said had much maintenance and tread breakage and they were not satisfied with the tread quality, but it was such machines everyone had used for years. The new one existed of a round nozzle with the size of a hand. By sending air tangentially into this the cotton becomes a tread. It had many times faster production speed, no moving parts, no tread breakage no demand for lubrication, no maintenance, noiseless and cheaper. When did we last saw an equal improvement from the agriculture machine manufacturer? The answer is quite as simple as it is short. Newer. Why not? Probably because the agriculture machine manufacturers earn more by only increasing the machine size and reckon that all the other manufacturers do the same to their "common good".
In the book "In search of excellence" you can read that you can see on the details if a company is good. I happen to think about this when I was on the exhibition Agroteknikk 2006 because several of the large combine manufacturers had painted their combines black inside and under the covers where belts and running wheels are located. This tells me a great deal of how little they care about their customers need and safety. Because if they were, they had for sure also putt his detail in order. One may then wonder how many other bad solutions that are hiding in these huge dinosaurian combines. If it only had been this detail, then it had for sure also been fixed long ago.
"Service is an especially important weapon to ensure that the customer chooses our products. I am not in doubt about that the fight about the marked will stand on the service aspect in the future." The statement comes from managing director for Sales and Marketing Branch Scandinavia in one of the largest deliverer of plows and harrows and equivalent farming equipments and can be read in the Newspaper for the exhibition Agroteknikk 2006. Hello, I have grown up with machines from this manufacturer and equivalent and we NEVER needed service. And everyone that is in a trade delivers the service that trade demand. That is of course inevitable. This statement tells met hat now they wish to press even more out of the farmers by writing large service bills with forks or maybe even with hayfork. What the farmers need in the future, more than anything else is machines that helps them to produce higher crops, more efficiency and less expensive machines and lower consumption of fuel, fertilizer, pesticides and less use of working hours. But then the manufacturers must be much more inventive, creative and focus to quite another extent to come up with new better machines.
If you may be is interested or have views we hope you will contact us on email: so we can map the interest. Flagros internet page is:

© Tron-Halvard Fladby/ 2006.11.09