Combines My research on TR vs CR s

[JD]

You said...."Basic physics- grain (high mass),chaff (low mass) are accelerated at the same rate by the rotors." I said...."F=ma" and this applies only if centrifugal force is present which I believe is, when the rotors of a TR are turned fast enough to generate it. My belief is, that the grain gets to the pan first via...F=ma and the chaff is somewhat suspended due in fact from the centrifugal force being thrust upon it. Thus some of the chaff is carried out the back of the rotors and the rest is laid on top of the grain on the pan. Then it hits the air blast at the point of dropping to the chaffer makes it easier to serparate. Unlike other rotored machines which can not generate the force needed to do so. And yes I realize the shaking of the pan helps in getting the chaff up and the grain down also. Just the way I see it after 26 years of messing with them. JD

 

[Dustmaker]

You figure centrifugal force has nothing to with more efficient grain separationIJ Why then the smaller diameter rotorIJ Because the grain is heavier than the chaff, and the circle is tighter on a smaller rotor, centrifugal force causes it to find its way through the concaves faster than the chaff. The heavier the material, the quicker it wants to move away from the rotor. Centrifugal force has every thing to do with how these work the way I figure it.

 

[JHEnt]

True the grain has a higher force behind it but its not the force of the grain that does the separation. The advertising lingo makes it sound as though the rotor acts on grain and chaff the way a centrafuge acts on liquids. Spinning a vial of liquid in a centrafuge will cause the larger particles suspended in a liquid to move to the outside. Smaller ones are squeezed toward the inside. When the centrafuge is turned off the large particles settle to the bottom. This priciple works for things suspended in a liquid medium but it does not simply convert to the way grain is threshed and separated in a very short span of air. The priciple of threshing is identicle to the principle of a cylinder, its just that the rotor by the way the material flows has a huge increase in capacity. When you get to the separating portion the basic priciple is still to lift the crop material and allow the grain to fall out. This on a rotor is really the only place where centripital force (the force which pushes and object directly_perpindicular away from the spinning axis) is used. In the rear portion of a rotor its like you took the strawwalker and twisted it into a spiral. This allows separatin to occur around the radius despite gravity. This may sound like a centrafuge but it does not work the way a centrafuge works. The rotor still works by lifting the crop so the grain falls out. Its just that the grain can fall out in any direction around the rotors axis. the more we get into this the more it sounds like I'm splitting hairs but I was just trying to point out that there is a difference. The big advantage in separating of the smaller dia rotor is the more fully used area. The larger dia the rotor gets the more unused surface there is at the rear section. This is because the majority of separation will occur in the 1st half of rotation making the other side mostly unused.