Flail Mower Let's talk flail mowers

[Eagleview]

If a change of flails is wanted , they must be the same weight as what is on there now . A pair of "L" shaped knives can be changed for a single "cup/scoop" type flail as they are the same weight but cast hammers cannot be used . Even if they will fit on , the rotor will be out of balance . There is always a lesser amount of flails/hammer/knives on one side of the rotor . The two end counter weights on the rotor make up for this . If heavier flails are used , the counter weights will not be heavy enough to counter their weight .

Just thought I'd add that so people are aware of the fact .

 

[IslandTractor]

The two end counter weights on the rotor make up for this . If heavier flails are used , the counter weights will not be heavy enough to counter their weight .

Is this a universal rule or just for your flail? I wonder why flail manufacturer's don't just balance the rotors naked so that any flail type, used in all the attachment points, would give you a balanced rotor.

 

[leonz]

Is this a universal rule or just for your flail? I wonder why flail manufacturer's don't just balance the rotors naked so that any flail type, used in all the attachment points, would give you a balanced rotor.

The water pail example is a good way to explain this;



If you tie a rope to a water pail and fill it with two quarts of water
and whip it around it takes a smaller effort to spin it and you have
to exert less effort.

The same pail with more water takes more effort and energy hence
the centrifugal force created is greater and requires a heavier balance wieght-
heavier knives are greater wieghts and require greater balance opposite the knife
to counter the centrifugal force -hence two rows of knives for the heavier P hammer
blades and cup knives among others.

The orbit must be even and balanced in order to do the work with out damaging the rotor and bearings.


I hope I did not hijack the thread with my response.


leonz

 

[Eagleview]

I knew you would ask that , I hope you know how much trouble I just went through .

There is always a lesser number of flails on one row of the rotor , these flails are positioned to cut the gaps left by the other rows . The rotors are Dynamically balanced at the factory with the flails attached . As you can appreciate , if the flails were not attached , they would not know how much counter weight to add and exactly where to add it to make up for the lesser amount of flails . As you can see on this old Berti , it has rows of 6 flails and one row of 5 , you can also see the square steel stock counter weights welded on to make up the difference , my Cabe is the same .

I don't know about the mowers with hundreds of little knives as to what they do , if they need counter weights or not as the rows of knives may be equal .

 

[IslandTractor]

I knew you would ask that , I hope you know how much trouble I just went through ..

Yeah, well now I have to go out and flip my mower over (not currently mounted on the 3pt) to count for myself tomorrow. :confused2: I know I have 28 sets of knives (2 per station). I guess that does not allow simple division by 3 or 4 and therefore I guess there is some assymmetry. Too dark to check right now.

I understand your point I just don't understand why they don't simply balance the flail stations so that any number of flails will work. If you consider a centrifuge, they are balanced so that if you put the same weight in all stations the centrifuge is balanced regardless of how much weight you add. I don't see why flail makers would not use that same principle. If you think about it, flails lose weight as they wear. That means they will become progressively out of balance if they are in balance only with fresh flails as shipped from the factory. However, if they are in balance so long as each flail weighs the same (and flail knives do generally wear equally over time) then it would remain in balance as knives wear and would also be in balance if you changed all the knives to a different style. Seems odd to me that they wouldn't do that.

 

[Eagleview]

By doing that , you are only balancing the shaft , not the reciprocating mass . What happens after you balance the shaft and then add the flails in rows of uneven numbers ?

 

[John_in_TN]

Island Tractor is right, your description must apply to specific flail mowers, not to all of them. My JD flail has three rows of blades with 12 blades per row. I am running the lighter "cup" style blades, but can change to the heavier style blades IF I change all of them as a set. I just can't intermix the blade styles.

 

[leonz]

UM no,


You have the rotor and it carries the throw weight of the hangers, knife blades, bolts nuts etc., the rotor is forever balanced with the welded on wieghts to avoid issues with broken knives and the other possible nasties.


The rotors orbit is forever balanced but if the knives are improperly positioned the stress is magnified at that location



The flail mower rotor is the center of the mowers universe and the orbit is small and centralised where the knives and hangers are not stationary plus
the knives are traveling slower than the rotor as the orbit for the knife is larger in diameter and takes longer to travel the circumference than the rotor does.

leonz:thumbsup:

 

[Eagleview]

A flail rotor with flails attached in a balancer and one waiting it's turn . I had seen a better photo of this but can't find it at the moment .

 

[sodamo]

Now I'm curious :laughing:

Mine came with both sets:
28 Hammers - mounted in 4 rows of 7

Second set is the grass knives 56 mounted in pairs, 4 rows of 7.

I just changed them out this past week.

But If asked, I'd been willing to bet the hammers outweighed the knife pairs. Guess tomorrow, I'll have to check.