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#1096868 - 30/03/2012 21:33 Re: The Push Button Combine [Re: ROM]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
The Combine Forum

The Push Button Combine Part 15

7 / 4 / 2010

This thread started as a look into the future trends of combine technology but in doing this I have also realised that it is also very interesting to look at where our industry has come from over the past couple of centuries.
So as you have seen in a couple of past posts I have expanded on where Australian farming technology has come from, probably an almost totally unknown part of farming technology as far as north Americans and Europeans are concerned.

Without belaboring the point, it was with some astonishment that I read that Cyrus McCormick, the American industrialist although not the inventor of the Reaper, [ invented by Obed Hussey in 1833 ] who is credited with the introduction of the reaper on a large scale from 1834 [ Hussey's machine was the only practicable one on the market before 1840.] only introduced the self raker to his reaper in about 1861, or some seven years after the first self raking reaper was produced in 1854.
Even then, north American farmers were still decades away from a simple single one man harvesting system.

Meanwhile Australian grain farmers had been using single one man operated "strippers" since soon after their invention by either Ridley or Bull in 1843 and thousands of "stripper" were operating in Australian wheat fields only a very few years after their invention.
More details in the previous thread;

To follow on in the historical context section of this thread I ambled along to the local Easter Agricultural Machinery Display at Warracknabeal some 50 kms north of Horsham.
There is a good selection of the older Australian harvesting machinery and tractors displayed at this Museum.
They eventually intend to put the entire catalogue on the web but as the whole museum is run solely by older generation volunteers both time and the necessary web skills are not readily available to do this as fast as they would like.

With few web skills myself I have had a lot of difficulty in figuring out how to place photos / images on the web for others perusal.
Some of these image hosts seem to delight in making their instructions as complicated and convoluted as possible so it was a case of sifting through them until I found one that was simple enough to understand.
Hopefully the following large number of thumbnails / images of the machinery on display at Warracknabeal will come out OK.

And if there are any questions about these machines just ask and I will try to find the info on the machine.

The following thumbnails / images show some of the harvesting machinery around the end of the 19th century and into the first 50 years of the 20th century.
As I included "tractors" in the thread heading, I have also included a large number of tractors and types, some purely Australian designed and built through the first 70 years of the 20th century.
A further caveat is you will find the photos listed under username "Blackheathen"
I am neither black and definitely not heathen!
The location of our property is in an area known as "Blackheath" and once consisted of a non official Post Office, a church, a school, a cemetery and one farm house, all gone except for the farmhouse and the cemetery, hence the username I assumed for this image host site of the "Blackheathen"

So following is a large number of thumbnails / images on harvesting equipment and tractors from the Warracknabeal Museum.

EDIT; I tried to transfer the images over to this forum site but it will be very long tedious process for this not particularly net savvy old timer. So I would suggest that you go straight to the original source of these posts on the Combine Forum and take a look at the clickable thumbnails there which also have the comments on each lot of clickable thumbnails.
You will have to scroll down to my second post on the Combine Forum page.

#1096869 - 30/03/2012 21:47 Re: The Push Button Combine [Re: ROM]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
A long, but interesting read ROM. Bottom line is to "keep it simple-stupid".

#1096946 - 31/03/2012 11:51 Re: The Push Button Combine [Re: Petros]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
Thanks Petros
And my apologies to all as further historical comparisons [ and the various relevant links ] between the American harvesting technological advances of the early and mid 19th centuries and the superior and earlier Australian grain harvesting technologies referred to above were previously written up and can be found in "Part 10" which to my embarrassment is unmarked as such.

#1097033 - 31/03/2012 19:38 Re: The Push Button Combine [Re: ROM]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
The Combine Forum

The Push Button Combine; Part 16

9 / 4 / 2010

Just thinking!
My brother and I always had a "crazy ideas" department running most of the time.
The only real criteria was that we weren't allowed to just denigrate any idea but would carefully pick the idea apart or modify it or far more likely, one crazy idea often led to other less crazy ideas and eventually led to a completely different way of looking at something.
It was quite remarkable how often a "crazy idea" from one of us led to a completely new and different approach to solving some difficult problem that we may have had at the time.
So the following is a "Crazy Idea".
Make of it what you will!

Everybody wants to get more capacity out of their combines.
So you can hotrod those combines like NDDan and some of the Gleaner hotrodders have been so very successful at doing to the transverse flow Gleaners.
In the process they have shown AGCO just how much more latent and under utilised capacity there is still left in the bog standard rotary Gleaner.
And even better, that quite considerable extra capacity can be achieved with very little extra expense.

Or to get that extra capacity, you can of course go out and buy a larger and far more expensive combine to gain that extra tonnage per hour throughput.

So what other alternatives are there to increasing harvesting capacities, particularly alternatives that do not entail a big outlay or much extra equipment?

An increasing number of combine owners are using grain carts which enable a combine to unload on the run and the grain cart then hauls the grain away to large mobile field bins of perhaps 75 tonnes capacity from which the trucks outload or the grain carts unload directly into to trucks or silos.

Our neighbor some dozen years ago bought and used a grain cart with his IH rotary.
Being very systematic he kept a close record of the extra capacity that he gained from his combine using the grain cart.
It increased the combine's harvested tonnage by close to 30% over a full day's operations and this was also the numbers over the whole season in all the cereal crops.
Effectively he moved up perhaps one and half to two classes in combine capacity just by using a grain cart to haul to a large 75 tonne tractor hauled mobile field bin from which the truck then hauled grain into the grain receival points or to his home based silo system.

There are a number of disadvantages to using a grain cart.
First is the cost of the cart and the extra grain cart tractor driver but the extra capacity and overall efficiency gains of the combine and operator more than make up for this.
Secondly the need for a sufficiently high HP tractor to pull the loaded cart through any difficult ground conditions although here again the normal grain farm tractor usually has sufficient HP and is usually standing idle when harvesting and so can be used for the cart haulage.
The need for reasonably experienced tractor and combine drivers who can coordinate their speeds and timing and distances apart so as to not spill any grain or far better, being skilled enough to avoid a collisions between the tractor / cart and header end.
This problem is usually solved by the combine at least using an auto steer system which drives a straight line which then enables the cart driver to formate with the combine with relative ease but even a slight misjudgment by the cart driver can and will lead to very expensive noises arising at the juncture point of tractor / cart and the end of the header.

The combine to cart unloading situation and maintaining the right clearance / distance for unloading becomes very touchy when the harvesting speeds start to get up past the 10 KPH or higher speeds [ 6 MPH plus ]
10 Kph and much higher harvesting speeds are not at all unusual in the Australian lighter crop conditions.
And it gets much worse when unloading at speed over undulating ground.

Then another disadvantage is the need for the combine to always unload on the same LH side which means that a considerable amount of juggling of box filling distances has to be made to accommodate the direction of travel so that the combine can be unloaded into the cart when the box is near full which needs to be when the unloader auger is on the harvested side on the left.
And at speed the distance travelled while unloading can very rapidly use up the available distance before the combine has to turn for the back run from which the combine cannot be unloaded due to the unloader being on the crop side unless a round and round or racetrack type harvesting pattern is followed.
Only possible with standing cereal crops.

The current situation with grain carts here in Australia is not that dissimilar to the introduction of much new farm technology.
GPS based auto steer systems are a recent classic case of how the introduction of new technologies are adopted by the farming community and it's supporting manufacturing organisations.

First the rather crude and trouble prone new technology systems come out of some small manufacturer and the early adopters move right on in.
If after a few years it looks like the new technology, despite the known problems, is slowly being adopted by more and more farmers then as in this auto guidance case, the larger electronics manufacturers pick up the technology and refine it so that it becomes more reliable, more accurate and much simpler to maintain and to fit into existing machines.
From this point the race is on amongst manufacturers to get a very substantial hold in the market and the advertising and sales pressure and the sophistication of the technology increases at a very rapid rate.

Then finally the technology is fitted as an integral part of the new machines by the combine / tractor manufacturers and within a few years is expected to be a standard fitment by the purchasers of any new combines and tractors.

I have seen this pattern with grain loss monitors in the 1960's and again with the ongoing introduction of the auto steer systems into today's combines and tractors.

A similar pattern is becoming evident with the introduction of grain carts at least here in Australia.
More and more combine owners are moving to grain carts to increase their combine's output while trying to minimise any extra expenditure.

The next move by savvy grain cart manufacturers will be to dramatically reduce the chances of collisions with the combine's header end and to make the formating of the grain cart with the combine as easy as possible for both the combine operator and the grain cart tractor driver.
This will probably entail a short range radio link between the combine's and the tractor's auto guidance systems that will enable the tractor to automatically match speeds and maintain a constant distance to the combine.
It will also include an unloading auger control that will automatically switch on the unloader when the grain cart is correctly positioned and switch it off if the grain cart moves too far out of position.

Then some combine manufacturer will realise that without much extra research or much massive new investment in new tooling for even larger capacity combines, they can, by developing at low cost, a grain cart that is fully compatible with their current range of combines and which has a complete interlink so as to accurately formate with that particular combine model / make, increase the tonnage capabilities of their entire range of combines by a very substantial amount.
And up goes their combine's capacity by perhaps another 25% as long as their grain cart is also part of the deal.

Then the next development takes place and that is to configure the combine to take better advantage of the grain cart's strengths.
A combine manufacturer realises that the combine can only unload while going one way and that is with the unload auger away from the crop.
Well it doesn't seem too hard to place an unloader turret [ and I don't like turrets one little bit but for this exercise!] right in the middle front of the combine grain box which would allow the unloader to swing to either side so that unloading can be done while traveling in either direction.
Nor with the auto steer is it completely necessary to place the cab right in the centre of the combine.

JD's had a few models that had an off set cab to allow for a front mounted engine so as a crazy idea, why not place the unloader turret out in front of the grain box with the option to swing both ways and off set the cab to allow the turret placement in the centre.
For the rotor type combines, this would put the well of the turret ahead of the rotor end which would make life a lot easier for the designer.
This would also allow the grain cart to start to load while well down the run and then pull out at the end while the combine does it's turn and starts back down the field and the grain cart could then reposition again, the loader would be swung to the opposite and now new cart position and the unloading process would be completed.
Naturally the grain cart's unloader would also be a fully fold down unloader so that the grain cart can be loaded from either side.

With a number of combines operating in a field such a system would have huge benefits as a reduced number of grain carts could service a number of combines regardless of their direction of travel as the carts would be in constant loading, traveling and unloading mode.

One other current problem with combines and the use of grain carts is that combine engines are run at close to constant full power while harvesting.
Combine engines as with all engine's outputs are based on duty cycles.
Below is the typical specification for a CAT engine's duty cycle;

IND - C (Intermittent) Intermittent service where maximum power and/or speed are cyclic. The power and speed capability of the engine can be utilized for one uninterrupted hour followed by one hour of operation at or below IND - A. Time at full load is not to exceed 50% of the duty cycle.
Typical service examples are: agricultural tractors,harvesters and combines.

With the use of grain carts the combine engines are simply run at close to full power for many hours at a time and this is something that the engine manufacturers are very unhappy about.
Cummins here in Australia are very wary of combine engines as they are regarded by Cummins as being pushed way past their operating regimes as regards duty cycles in combine operations.
And that is with regular high idle no load running and a consequent cool down cycle while unloading let alone with continuous high power and no low power interludes for duty cycle purposes.

That is something that the combine manufacturers need to fully consider as well but up to now they seem to just want to look the other way and hope that any engine problems just disappear.
They won't and the introduction of grain carts on a large scale as a cheap way of increasing combine productivity is merely going to increase the combine manufacturer's engine problems unless they rethink their current combine powering strategies.

And while we are about it, why are cabs which are nearly fully self contained these days as they are built as multi use units, always bolted down in the one position.
Why not have cabs on a simple hydraulically controlled arm that will allow a cab to move a limited distance left, right,in and out, possibly up and down and also have a limited rotation so that the operator can position him / her self in a position that suits them best.

Crazy Idea I know!


#1097142 - 01/04/2012 12:05 Re: The Push Button Combine [Re: ROM]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
The Combine Forum

This is the final post I wrote on the "Push Button Combine" thread.

These posts plus some shorter ones in the thread took a lot of time and research to try and make sure I got my information and facts straight as I was writing for a foreign audience who had been led to believe that they were the original inventors and developers of all the significant advances in agriculture machinery over the last 200 years.

I simply ran out of enthusiasm and so decided to stop while [ I hoped! ] I still had considerable interest in what I was posting.
This final post was getting into the technical side of combine design which I along with my very innovative brother who I was in partnership at the time, have dabbled rather heavily in whilst developing our unique medic seed harvester.

My thanks to all those who have had the interest, the patience and stamina to read this far.

The Push Button Combine Part 17 & Final

17 / 4 / 2010

Most grain growers have a fairly good knowledge of the principles behind the various processes that are carried out during the collecting, threshing and separating processes in a combine.
However I suspect that a lot of owners / operators more or less throw their hands up in the air if you ask them just what are the design principles behind the designs of the sieve fans in a combine.
Those hands might only go up a bit when you talk about the age old garden variety paddle fan but when the discussion gets onto the principles of operation of a squirrel cage fan and / or a cross flow / vortex flow fan then a certain silence might descend on the discussion.

A few days ago I wandered around the dealer's yards that represent five makes of combines in this town.
One dealer, Caterpillar, did not have any combines displayed so I couldn't check the Lexion
I was just a little surprised at the variety of sieve fans I found on both the new models and the older traded models.
Now what I saw may not be the absolute latest and no doubt I will be corrected very rapidly if I get something wrong.
My excuse is that I no longer even try and keep up with the telephone numbered series of model identification that some manufacturers seem to delight in these days and if I did I probably would get a 9670 mixed up with a 9760 or a 7690 and etc if such things exist.

These numbers might mean something to the aficionados of that manufacturer's products but when you get at least three manufacturers all designating their models with similar and interchangeable telephone numbers it does show a truly remarkable lack of imagination by their marketing sections.

I don't know about Americans but if the car manufacturers tried to sell their entire range of models here in Australia starting with numbered models like model 62, something close to a push bike, 625, about 5/8ths of a reasonably performing vechile, 6.25.8 for the family job and then the 625-7.85 for the performance machine I doubt that the sales figures would be exactly spectacular.
Call them Cobra, Falcon, Corvette, Mustang and etc and sales would go right up and everybody would know which make and model you are talking about!
Although come to think of it, a [ hypothetical ] "Mao" model from "Great Wall Autos" does seem to lose a certain something in the translation.

I have along side of me a Buffalo Forge Fan Engineering book of biblical type dimensions with some 860 pages dealing with all aspects of air and gas movement.
Fans and fan design alone, take up some 200 pages of this book.
It was always close at hand when I spent a number of years along with my brother, designing and building an one off, ultimately very successful suction type medic pasture seeds harvester which I commented on in the Two Rotors thread.
That darn book cost me an eye watering $180 AUD in 1983 and that was at wholesale rates as it was not the very latest edition.

Now fans look bloody simple and anybody can build one!
That perhaps applies to the simple old basic but inefficient paddle fan in it's sheet steel casing.
For the rest of the fan designs, well I have news for you!

Fans both in design and in construction are a very sophisticated bit of engineering and involve some very complex formula's and calculations if you are to get an efficient and good performance fan.
There are some specialist fan design companies who do nothing but design fans and test those designs.
Then there are specialist fan builders who often have their own design teams but also build fans to designs from the specialist fan design groups and who do no other engineering except build fans and fan systems.

Very few people are also aware of the basic fan laws with regards to fan output and the power that fans require.
It is always a very good idea to know and remember the following simple facts about fans.
Provided the fan is running within it's RPM design range and importantly, has an unobstructed inlet and outlet flow and all other factors, most of which are quite important in practical use, are unchanged;

1 / Air volume changes in direct relationship to the changes in fan RPM.

2 / Pressure changes are the square of the fan RPM changes.

3 / HP required is the cube of the fan RPM changes

If we use a practical combine based example where the combine fan RPM is increased by say 20% or 1.2 times which is well within the fan RPM range used by combines.

1 / Air volume will increase in line with the 20% fan RPM increase = x 1.2
A 20% increase in air volume for a 20% increase in fan RPM's

2 / Pressure would increase as the square of the RPM change; = 1.2 x 1.2 = 1.44
Pressure will increase by 44% for a 20% increase in fan RPM's

3 / HP required will increase as the cube of the RPM increase;
= 1.2 x 1.2 x 1.2 = 1.728.
HP requirements will increase by 73% for a 20% increase in fan RPM's

The converse is of course also the case with fan RPM reductions.

That sort of HP increase / decrease has all sorts of connotations for the drives on combine fans but other factors also come into the practical side like the amount of resistance to the fan airflow that exists due to the sieves and of course, just how much resistance to the airflow the mass of threshed material on the sieves has.
There are also some variations on those basic Fan Laws due to the different design approaches used in fan design but the basic underlying thrust of the fan laws holds for any particular fan design.

There are three basic types of fans.

First is axial flow type of fan where the airflow is along the axis of and through the fan.
The common multi bladed domestic cooling fan and the vehicle radiator fan are examples but the axial flow type of fan also includes some of the most sophisticated fans around, the multi-bladed gas turbines used in aircraft and in the steam and gas powered electricity generating power stations.
Another example that is familiar to rural Australian's is farm reservoir water and / or well / bore pumping windmill.

The Windmill Journal

[ Being the next to Antarctica as the driest continent on Earth, the ready availability of water in Australia has a significance that for North Americans and Europeans with their immense and readily available supplies of water, find hard to grasp. ]

With the more simple versions of this axial flow fan, pressure rises and the controlling of the rise and flow evenness with the twisting or torquing of the airflow from the rotation of the axial flow fan makes for some rather difficult engineering to get evenness of air flow across the entire sieves for such a fan design in combines.
This rotation and unevenness of the airflow can be corrected by using deflectors and guide vanes to straighten the flow of air but this then increases drag on the airflow and significantly reduces the overall efficiency of this type of fan design.
The type of Axial flow design fans that we use in everyday use can be choked right off without any ill effects to the fan.
But that characteristic also poses problems when the sieves become overloaded and the air flow then just shuts down and blocked sieves may be the result.
However, despite the inherent design problems in creating a smooth airflow from this type of axial flow fan under sieves, I think Claas at least, still used a bank of axial flow fans under the sieves in some of their combine models.

For interest, just to give a few examples of axial flow fans and the sizes they can and are manufactured to;

Wind Tunnel Fans

The next is the very common and popular radial flow or centrifugal flow fan type where air is drawn into and flows into the centre of the fan impeller and is then through centrifugal force, thrown out through the fan blades, ie; flows out of the fan in a radial flow.
The air is contained and directed by the fan casing which usually takes the form of an increasing in radius scroll as the casing contains and directs the air flow around the expanding radius of the scroll into an outlet.
This basic fan design can range from the most simple 4, 6 or 8 bladed paddle fans that were and still are found in nearly all of the older combines and are still found in some of the latest combines right up through to the huge in both diameter and capacity, centrifugal mine ventilation fans or power station boiler and exhaust extraction fans that take thousands of HP to drive.
The centrifugal fan design type encompasses a huge range of fan designs using the basic centrifugal or radial outflow design.
It includes the narrow cased high volume and / or high pressure fan types that are not that dissimilar to the centrifugal water pump in design and operation as well as the wide cased, very high volume fans for aeration and ventilation.
The difference between the centrifugal water pump and the centrifugal fan is just that the centrifugal water pump is designed to operate with an incompressible fluid whereas a centrifugal design fan, as do all fans, operate with a highly compressible fluid, ie; a gas or air in our case.

The paddle fan is cheap and easy to build, reasonably efficient, gives a good flow of air that with a little tweaking of the casing / scroll design can give an even airflow distribution right across the fan outlet and therefore is very good for the evenness of air flow under a combine's sieves.
Which is why for some 150 years or more it has been the most used design of fans for an innumerable number of applications of every conceivable type that require the movement of air.
The useable width of the paddle bladed fan is limited by the amount of air that can flow in through the open end holes of the fan scroll casing before that air turns into a radial flow out through the fan blades.
Too long a fan of this type and sufficient air will not reach the centre of the fan leaving a dead spot on the sieves and causing big disruptions to the airflow from the fan under the sieves as the air tries to flow across to the low pressure region to even out the pressures.
To overcome this, some combine manufacturers split their paddle fans into two units on a common shaft with a large opening in the middle of the fan scroll housing to allow air to flow into the centre of the fan and provide an even air flow right across the sieves.
The simple paddle bladed fan also is not particularly fussy about the accuracy of the scroll of the casing so considerable dimensional intolerances can be accepted when being manufactured before a noticeable falling off in performance can be detected.
As with all fans, the clearances of the cut offs to the fan wheel where the fan air flow changes from the outlet to the start of curve of the scroll can make a big difference to fan performance but once the air starts it's journey around the scroll towards the outlet, paddle bladed fans are not very fussy about clearances.

The other check to be made is to have the minimum of clearance around the end of the fan blades and between the blade ends and the end housing of the casing / scroll.
Leakage around the blade ends or uneven spacing between the ends of the blades of the fan and the scroll end housing will allow considerable air flow around the blade ends and allow variations in air flow under the sieves.

Centrifugal fans can and do also have neutral, forward curved and backward curved blade designs, all of which give different pressure rises and volume flow characteristics so that a fan design can be selected to achieve certain air/gas flow characteristics.

JD some time ago in some of their models used a bank of closely spaced and very sophisticated narrow cased centrifugal fans mounted on a common shaft under their sieves.
NH still appears to be using the old bog standard simple paddle fan under their sieves if the what I assume is a late model NH combine I looked at a few days ago represents NH's current fan installations.

A version of the centrifugal fan is known as the Squirrel Cage fan named after the wheels that I assume tame squirrels [ no squirrels in Australia except in zoos. ] and tame rats, mice and etc get inside to run and exercise.
The Squirrel Cage fan has a large large number of closely spaced, long, narrow, curved forward blades set well out on the periphery of the fan wheel.
This particular version of a centrifugal fan design if properly designed has some excellent high volume flow characteristics and some good pressure rises as the the fan RPM's are increased to handle heavier sieve loads.

JD appear to be using a coarse squirrel cage type of centrifugal fan at present in [ some of ? ] their latest model combines.

Squirrel Cage fans can also be found in small versions in the combine and tractor Aircon cabin fans, in some domestic water cooled aircon units and in a number of other very high volume, low pressure applications particularly in the structural cooling and heating industries.

There also some very sophisticated mixed flow fans where the axial flow design is mated with the centrifugal design to give a very high efficiency fan impeller with big pressure capabilities and good volume flow rates.
Turbo chargers both in the blower impeller and the exhaust turbine use mixed flow impeller designs and with rotational speeds up to over a 100,000 RPM in some instances, some very hefty pressure rises can be achieved from turbo chargers.

Allis Chalmers techs once checked our now long gone 7045 tractor as we were having fuel pump problems which subsequently were discovered to be caused by excess paraffin wax in the distillate.
On cold mornings [ like cold for us is 5C below freezing for a couple of hours! ] the paraffin wax in the diesel fuel was freezing solid and the thin sheet of fuel which acted as a lubricant for the closely machined innards of the pump was scraped off from between the rotor and housing allowing bare metal to bare metal contact and the resultant scoring of the pump rotor and housing and a buggered pump.

All of which led to some loud language and some table thumping in an interesting meeting with the technical marketing managers, the guys between the refinery and the wholesalers, of the 27 oil companies in Australia at that time.
I had a lot of info from a lot of research over the previous few months on what turned out to be a widespread and serious problem for farmers, truckies, earth movers and etc so I very unexpectedly and very nervously got the job from our farming organisation of taking some of those tough oil company technical marketing managers on.
Subsequently and very quickly the excess paraffin wax problem in diesel fuel disappeared as the oil companies did not like being told face to face that they were responsible for a lot of severe damage to diesel engines due to their fuel policies and that they were ripping us off plus some TV exposure.
Got pretty rugged at times in that meeting but strangely I had quite a few of those oil company managers who supported me and the two other farm organisation guys who came along with me for support.

Back to the AC test.
Can't remember the exact numbers but the turbo charger on the 7045 was cranking up to something in excess of 30,000 RPM [ I think. It could have been more! ] at full bellow on the PTO dynometer they brought along and the pressure rise from the turbo idle to full power was an astounding 28 PSI which made the AC tech's eyes bulge.
No turbo waste gate on that 7045 either.

Centrifugal fans including squirrel cage fans all suffer from one major drawback although one that a good combine operator will rarely experience.
That is they can be choked off when they reach a critical pressure depending on their design.
They just spin away and totally quit performing with no pressure as well as no flow.
Just the same as you can turn off or throttle a centrifugal water pump with a tap on the outlet or inlet.
The same factors apply to a centrifugal fan.
So if you achieve some heavily loaded or over loaded sieves then the fan if it is of the centrifugal or axial design will just quit and do it suddenly as was deliberately demonstrated to me by a friend in his big White combine some years ago.
His fan pressure monitor just said of the fan pressure "I quit" as he drove hard and deliberately overloaded the sieves, something that a decent sieve fan design should never allow to happen.

The third basic design of fans is the Cross Flow fan or sometimes known as the Vortex Flow fan or Tangential flow fan.
This particular fan design makes hardened engineers throw up their hands as they try to get a handle on the way in which the cross flow fans work.
Cross flow fans are increasingly found in combine sieve systems as they have a number of very desirable characteristics from a combine engineer's view point as well as from a combine operator's point of view.
AC with the advent of the L series were possibly the first combine manufacturers to use the cross flow fans followed by MF in the late 1970's with a somewhat crude version but nevertheless a cross flow fan in the last of the MF Australian built combines, the previously posted "11 second combine".

The cross flow fan was first patented by Mortier in 1893 so the basic design is quite old.

The cross flow fans look very much like the Squirrel Cage fans in their design with a large number of long, narrow, curved forward and closely spaced blades arranged around the periphery of the fan wheel.
However the way the Cross Flow fan works has no relationship with the squirrel cage fan or any other fan design.

The air flow in a cross flow fan is through the rotating blades right across the width of the fan and into the centre of the fan.
There is no central along the axis, infeed of air as it applies to the centrifugal and axial flow fans.
All the air flow enters the fan through the rotating blades along it's length.
Near the outlet duct of the fan a very concentrated, intense and very high speed rotating vortex is established which is partially within the fan wheel blades and partially external to the fan wheel blades.
This steering vortex runs the length of the fan outlet duct and the blades of the fan traverse through the vortex as they rapidly rotate.
They do this without disrupting the vortex structure.
This steering vortex then directs the airflow into the exit duct of the fan and a strong outflow from the fan to under the sieves is established.

For some good illustrations and information on the air flow in a cross flow fan, the paper;


There are quite a few research papers on cross flow fans as there are still a lot of not fully researched characteristics to be sorted out in Cross Flow fan design but unfortunately most of these cross flow fan research papers are behind pay walls.

From this you may have gathered that there is till a considerable amount of art still involved in cross flow fan design rather than the use of available hard concrete data.
Cross flow fans have some very interesting characteristics which makes them very popular in computer cooling fans and other areas where small diameter fans with good volume output are required.
As the cross flow fan takes air in through it's periphery right along it's length then there is no theoretical limit on just how long you can make a cross flow fan.
The air just keeps right on flowing in.
As the air inflow and therefore the air output is even along the whole length of the fan, it is ideally suited to sieves and as the various models of combines are changed in their respective sieve widths it is only necessary to shorten or lengthen the fan and it's scroll housing to fit the changed width of the sieves.
Manufacturing is also very easy as the one size, except for width fits all with no air flow problems arising from increasing width.

There is another very desirable characteristic but with a potential and literal twist to it.
Cross flow fans unlike all other fan designs, will continue to increase pressure if their outlet is blocked with say blocked sieves until such time as they overload their drives or in the worst case have a structural failure and wind themselves up into a knot.
That is why when you look at the top of the outlet fan duct panel in the R series Gleaners, there is a full width, approximately 50 mm wide slot across the entire top panel of the fan duct and a big sign saying "keep slot clear".
If you get blocked sieves with a cross flow fan and the air flow from the fan has no escape opening to relieve pressure, the fan will slip the drive belt or destroy the drive or wind itself up into a long tangled mess of metal.
That slot is a pressure relief slot for just such a blocked sieve circumstance.
The other advantage of the cross flow fan is the small overall diameter of the whole fan system for a lot of volume and pressure.
Another simplified problem for a combine designer.
He doesn't have a bloody great big fan to fit into too small a space.

The down side of cross flow fans from the combine designers viewpoint is the designing of a cross flow fan that will actually perform with the characteristics that are required.
The design of the impeller is very important as it is with all types of fans.
However with cross flow fans the design of the scroll housing is of the utmost importance as the velocity, location, size of and position of the critical steering vortex hinges very much on the design of the scroll housing in both the inlet and the outlet ducts areas.
Also the accuracy of the build is very important to get even airflow right across the sieves.
I suspect that some combine manufacturers have not quite got on top of this just yet.

I had some recent experience while messing around with a cross flow fan from one of those MF combines of the 1970's.
A very good personal friend, regarded by some of the world's top class international competition glider pilots as arguably the best FRP [ Fibre Reinforced Plastics ] glider / sailplane repairer and refinisher in the gliding world, wanted a dust extractor so for starters, we had a look at a cross flow fan from an old wrecked MF combine.
That fan was crude and needed about double the number of blades in it's wheel to be any good but it did the job in those late 1970's combines.
When making up the scroll and ducting, I copied as much as possible the original scroll of the fan, all of which I mounted on the steel bench top.
Over many days of messing around, I then found that even only a few millimetres adjustment in the fan duct and in the scroll configuration in a number of places created large changes in volume output.
It was a good lesson in the difficulty of designing a cross flow fan and no, I eventually figured it was going to be a long and costly business to start a new design dust exhaust system from scratch so my friend just brought a well proven make of dust extractor that worked from the get go.

Looking at cross flow fans in combines like the Gleaner series, I am still trying to figure out if the Gleaner designers of the original cross flow fan used in the L series were geniuses to design that fan which is still unchanged in all important dimensions in the latest Gleaners, nearly 30 years on.
Or were those designers just plain dumb lucky to crack the key to that cross flow design that has proven to be so good that it has been nearly unchanged and lasted all those years right across the various Gleaner designs since.

And they never had computers of any sort to do that designing on either!

Another intriguing feature of the Gleaner fans is the use of a throttling board to control the air flow into the constant speed fan, a huge benefit in simplicity and engineering.
That throttle board has to also be set to some close tolerances and clearances to avoid uneven airflow across the sieves.
What also intrigues me is the fact that no other manufacturer uses such a throttling board system when they have installed a cross flow sieve fan.
It's extremely simple, works and works well so why isn't it used elsewhere on cross flow fan systems for airflow volume control?

There is another little story on various cockups that occurred with that 11 second combine.
When MF finally got the prototype and preproduction runs of that combine sorted, they put it into production.
As soon as the production combine hit the fields, there were screams from the customers that the [ cross flow ] fan and sieves were, to put a not too fine a point on it, shxt!
As the fan and sieves had performed extremely well during final testing of the prototype and preproduction combines there was considerable consternation in the executive and designer ranks.
A careful check of every aspect, jigs, build, assembly was carried out and everything was right up to the specs as determined in the prototype and preproduction models.
In some despair and with hands being thrown in the air in frustration, a couple of executives decided to wander down to the paint shop.
There they discovered a painter who with much muttering about the stupidity of those further up the assembly line had taken to standing on the fully assembled fan and fan scroll housing so that he could paint a relatively inaccessible part of the combine way up in it's guts.
That of course, distorted the scroll by a few millimetres and consequently the fan failed to perform and the grain cockies got lousy samples from their brand new combines.

Next up maybe will something on sieve systems but a lot shorter than this effort.


#1100132 - 18/04/2012 20:31 Re: The Push Button Combine [Re: ROM]
ozone doug Offline
Weatherzone Addict

Registered: 06/11/2006
Posts: 1928
Loc: Roma SW QLD Eye to the West...
Good reading Rom ,I always learn heaps and enjoy it.And food for thought how technology is helpful and a pain . Cheers Doug
Cheers Doug. 491 Doug/ uhf ch40 When severe weather
BOM Stormspotter G0388 Roma S W Queensland Formerly Redcliffe.

#1110864 - 23/06/2012 09:33 Re: The Push Button Combine [Re: ozone doug]
GDL Offline
Weather Freak

Registered: 17/02/2008
Posts: 630
Loc: Bowen Mountain NSW
Rom your wisdom and forthright opinion is missed dont stay away to long........GDL

#1117418 - 31/07/2012 20:31 Re: The Push Button Combine [Re: GDL]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
Just thought I would toss this in tonight.
Back in those posts above I mentioned how manufacturers pinch ideas from farmers but never ever give any credit as to where they get those ideas from.
And the bigger the manufacturer, the worse they are when it comes to recognising the innovators and farmers and small engineering shops innovations and developments that the big outfits just basically steal.
Well I don't know if this was being developed before I posted it in the second last post above dated; 9 / 4 / 2010
To quote;
More and more combine owners are moving to grain carts to increase their combine's output while trying to minimise any extra expenditure.

The next move by savvy grain cart manufacturers will be to dramatically reduce the chances of collisions with the combine's header end and to make the formating of the grain cart with the combine as easy as possible for both the combine operator and the grain cart tractor driver.
This will probably entail a short range radio link between the combine's and the tractor's auto guidance systems that will enable the tractor to automatically match speeds and maintain a constant distance to the combine.
It will also include an unloading auger control that will automatically switch on the unloader when the grain cart is correctly positioned and switch it off if the grain cart moves too far out of position.

Then some combine manufacturer will realise that without much extra research or much massive new investment in new tooling for even larger capacity combines, they can, by developing at low cost, a grain cart that is fully compatible with their current range of combines and which has a complete interlink so as to accurately formate with that particular combine model / make, increase the tonnage capabilities of their entire range of combines by a very substantial amount.
And up goes their combine's capacity by perhaps another 25% as long as their grain cart is also part of the deal.

Well I was talking to a gliding mate on sunday and we got onto the subject and he told me that only days beforehand a friend or rellie of his, not long back from the USA, told him that JD now has auto-matching of speeds and clearances between grain carts and / combines / headers as the combines unload on the go into the grain carts, done with a short range radio link between the combine and the tractor pulling the cart.
I look at that date on my post and it would only take months with the current state of electronics to develop and test such a system.
I' ll leave it to you dear reader as to what conclusions you might draw from this.

I for one will be watching for the first combine that can unload on both sides instead of just on the left hand away from crop side as is the current status of every combine manufacturer's machines.


#1117722 - 02/08/2012 14:30 Re: The Push Button Combine [Re: ROM]
ozone doug Offline
Weatherzone Addict

Registered: 06/11/2006
Posts: 1928
Loc: Roma SW QLD Eye to the West...
I agree with you ROM ,How manufactures and companys take inventions amd crow and make heaps of money .I made some equipmemt for a former employer they made and sold it made lots of money and i didn't even get a pat on the back .cheers Doug
Cheers Doug. 491 Doug/ uhf ch40 When severe weather
BOM Stormspotter G0388 Roma S W Queensland Formerly Redcliffe.

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