Rotary Cutter What size rotary mower to get for Kubota L3830?

[aczlan]

We have a Kubota L3830GST (37 engine HP and 32 PTO HP per Tractordata)
We currently use a 5' cutter on it and while the tractor knows it is there in heavy stuff, it doesn't clear the tracks.
Looking at getting something bigger and am torn between 6', 7' and 8'
Main uses would be:
1. Keeping an overgrown hay field knocked down 2x/year
2. Finish mowing around the hayfields (to have a path all the way around)
2. Mowing our hay fields if we decide to mulch that cutting
3. Finish mowing the grassy "picnic" field out back
On occasion, we might push back some hedgerows, but not very often.

I am thinking that a 7' twin spindle (such as the SQ84T) would be ideal, but I haven't seen one on Craigslist yet.
Also thinking that a tri deck finish mower would be fun, but too big and not heavy enough to do the overgrown field mowing

I have thought of a flail, but I dont like them and they dont show up on the used market very often, so unless one fell into my lap, flails are out (no offense Leonz).

Aaron Z

 

[MarkV]

The general rule is 5 PTO hp per foot of mower so a 6' mower would be the norm for your tractor.

MarkV

 

[murphy1244]

6 footer.

 

[patrick_g]

6 footer.

I'm running 39 PTO HP Kubota and 6 ft brush hog. I have taken down trees up to about 4 in in diameter. Not easy. Can't mow a pasture at high speed when heavy grass.

You would probably be able to run 6 ft but I'd not go bigger unless only mowing sparse stuff (we both know that won't happen)

Pat

 

[aczlan]

Found a 6' one for $500 on CL. Will have to check the tread width... The guy has a 7' one as well. Wish he were close enough to try them out on the tractor.

Aaron Z

 

[patrick_g]

Found a 6' one for $500 on CL. Will have to check the tread width... The guy has a 7' one as well. Wish he were close enough to try them out on the tractor.

Aaron Z

Folks will quote x HP per foot of cutter but... it isn't really linear.

You can probably use a 7 but you will not drive very fast in anything but the lightest grass loads. Of course, if your fields are rough enough you won't drive fast anyway so maybe that is OK. I have both smooth areas and rough ones. In rougher areas I have to go less than a walk maybe 2mph or less sometimes. With medium load of grass and smooth lay of the land I go too fast to admit how fast. Faster than a typical jogger, closer to a marathoner and sometimes nearly a sprinter.

Pat

 

[aczlan]

Folks will quote x HP per foot of cutter but... it isn't really linear.
You can probably use a 7 but you will not drive very fast in anything but the lightest grass loads.

And as I understand it a dual spindle machine is easier on the tractor than a single spindle machine (ie: a 7' dual spindle is easier on the tractor than a 7' single spindle due to being shorter and the difference in rotational mass)

Of course, if your fields are rough enough you won't drive fast anyway so maybe that is OK. I have both smooth areas and rough ones. In rougher areas I have to go less than a walk maybe 2mph or less sometimes. With medium load of grass and smooth lay of the land I go too fast to admit how fast. Faster than a typical jogger, closer to a marathoner and sometimes nearly a sprinter.

I know the feeling. The 5' behind the L3830 is almost unnoticeable in most cases, the limiting factor for speed ends up being how much bouncing I can handle.

Got pictures of the 7' that the guy is selling for $1700:

Looks pretty nice.

Aaron Z

 

[patrick_g]

And as I understand it a dual spindle machine is easier on the tractor than a single spindle machine (ie: a 7' dual spindle is easier on the tractor than a 7' single spindle due to being shorter and the difference in rotational mass)


I know the feeling. The 5' behind the L3830 is almost unnoticeable in most cases, the limiting factor for speed ends up being how much bouncing I can handle.

Got pictures of the 7' that the guy is selling for $1700:
View attachment 259011 View attachment 259012
Looks pretty nice. Aaron Z

Picture of yellow cutter is medium duty unit, probably sufficient for needs of the OP.

Regarding twins for 7 footer being easier on tractor... maybe so but not for stated reason. The moment is greater for a longer blade and if you abruptly dump the clutch you will cause more wear with heavier longer blades. Twins don't cut blade length in half due to overlap and aren't all that much less of a load.

To cut effectively there is a minimum blade speed (not RPM) but equivalent straight line speed to get good cutting action. To achieve this speed near the hub/stump jumper) you will, of course, exceed the min required at the blade tips. This excess speed translates to imparting more momentum to the cut material. This is an energy sink which siphons off HP to move grass faster than needed after it is cut and isn't a particular benefit. Aerodynamic drag goes up and wastes HP too.

Since drag goes up with the 3rd power of speed (double the speed and it takes 8 times the HP) long single blades take more HP than a pair of shorter blades (usually) assuming not more overlap than needed. ...and then there is mechanical train losses from the gearbox arrangement, another set of rotating bearings, and so on.

Anyway there are trade offs, 4 blades to sharpen and balance vice two, more bearings, more expensive gearbox and mechanical drive components, less reliability...

Pat

 

[stoyan79]

6 footer would be ideal.

I have 6 footer on my 3700su, which I believe has the same engine as your tractor. I wouldn't go any bigger.

 

[bucktaker]

its likely a cat 2 unit anyway....buy it.. try it.. if you dont like it sell it