Rotary Cutter/Tractor Weight Rule of Thumb?

[Anonymous Poster]

Hi,

I plan on buying a rotary cutter this spring. I want to buy a pretty good one. Or at least an average one...

My B2910 Kubota weighs about 1,800 lbs or so. The front tires are foam filled and that adds about a hundred pounds I think...I expect I would have the loader on while using the rotary cutter.

I see a standard duty 5' rotary cutter will weigh in somethink like 550 lbs +/-, while a medium duty would weigh 1,000 lbs or a little more.

Would a medium duty 5 footer be too much to hang on the back of an 1,800 lb tractor? Is there a rule of thumb to follow here? I guess the concern is when transporting more than when actually cutting...

Any pointers greatly appreciated!

 

[JohnMiller3]

<font color="blue">... Any pointers greatly appreciated! ...</font>

Well Bill... where do I start...? I want to be gentle... /forums/images/graemlins/wink.gif

First off... how much/thick of brush do you think a 22 PTO hp tractor can manage...? I don't know the exact geometry of your Kubota B2910HSD... but if it's similar to my Satoh ~~22 PTO hp, 2200 lb. unit... I'd say you'd be pushing it with a standard 5' rotary cutter... a medium duty would be out of the question...

Just for a moment, with all else being equal... if your Kubota could manage to transport the medium duty 1000+ lb rotary cutter around... now what...? When you get tangled up in some tall/thick grass... that little torque reserve on the Kubota will just die...die...die until it stalls out or until you disengage the PTO... cutting woody stuff is even worse!

A medium duty cutter will serve NO advantage to you and your current tractor... For your present situation, I would stick with a standard duty 4' rotary cutter that does up to 1" woody material and to go beyond that... I'd consider a larger HP tractor... both in mass and PTO hp size... /forums/images/graemlins/smile.gif

 

[Anonymous Poster]

Hi John and all,

This is EXACTLY the input I need...

<font color="blue"> A medium duty cutter will serve NO advantage to you and your current tractor...</font>

Now I was not looking at the standard vs medium duty from the perspective of what I would cut, but rather from the perspective of which would last a lifetime due to mechanical construction differences.

I figured that the medium duty would not take much if any more HP to turn it in free air than the lighter duty one, but that it might hold up better to limited physical abuse and maybe some storage abuse too over the decades... /forums/images/graemlins/blush.gif

To give you an idea where I am coming from, I have a KK back blade that so far does all I have needed it to do...but I now feel I should have put that money towards a nice, heavy duty "big-name-brand" back blade, which would have better construction and a couple extra features...

Actually, I only have a couple acres that I want to clear and then probably keep cut a few times per year. So my guess is that a standard duty of ANY brand would probably do the job, but that a cheaper, lighter, thinner one might not last as long as I expect to.

It was reading another thread where the light popped on in my head as to the weight of a medium duty unit being pretty high compared to the weight of my B2910. /forums/images/graemlins/shocked.gif Something I had not considered and also something that doesn't seem to come up as much as PTO power requirements.

Now I believe there are a lot of B2910 owners out there [and other 22 PTO horsepower tractors as well] with 5 foot rotary cutters hanging off the back...enough that I assumed it was a workable combination. Provided that one was not intending to do more than his tractor is capable of, naturally...

I am still amazed that while I have read a lot about HP needed to turn the cutters [when working them hard] I only realized recently that the other important consideration is the weight of that rotary cutter hanging way out back there /forums/images/graemlins/tongue.gif Who wants do to wheelies all the time when moving with the rotary cutter in the transport position? I don't!

So, given the fact that my tractor will NEVER work a medium duty rotary cutter to its limits, if I would decide that I want to pull a 5-footer behind my tractor and do light cutting with it, would it be crazy to do that? I mean crazy to consider hanging a 1,000+ lb implement of ANY kind back there if it sticks out that far and needs to be lifted for transport?

I probably did not ask the question right the first time. What I was looking for is a rule of thumb relating tractor weight to the maximum weight that we might want to hang on the TPH, if it sticks as far back as a rotary cutter does.

From the standpoint of keeping the front wheels on the ground and maintaining steering control when using the implement or transportig it.

I think a box blade of any weight liftable by the TPH would be fine for example...

By the way...no need to be gentle /forums/images/graemlins/grin.gif

Thanks for your input John [and hopefully a follow up /forums/images/graemlins/smile.gif ] and for comments from anyone else that wants to share something!

 

[BillyP]

Bill,

I agree with John, the 5ft medium duty would be out of the question. It's way too heavy for your tractor. You could probably handle the light duty (weight wise) but if you cut heavy grass, you're gonna run out of power. I believe I read somewhere that you need 5 to 6 PTO hp for every foot of rotary cutter.

I have a 6ft cutter on a 36 pto hp tractor. Sometimes it'll bog down a little.

Stick with a 4 footer. Your tractor will love you for it /forums/images/graemlins/wink.gif

 

[Bird]

Bill, I'll agree with John & Billy about staying with the light duty mower, but I'm gonna disagree with them on the size. I had a 4' rotary cutter with my B7100 and when I traded up to a B2710, I also pretty quickly traded that 4' rotary cutter for a 5' one and would not at all like anything smaller unless I was going to be cutting brush over 1" in diameter more than just occasionally.

 

[Soundguy]

For one thing.. you will probably be near the lift capacity for your 3pt hitch if you go for a 1k# rear impliment.

If yours is 22 pto hp, that puts you right on the edge for the 4/5' powered impliments.

I wouldn't hesitat to use .. say 5' box or rear blades though.

As for the cutter.. you might try to borrow a light duty 5' cutter like a KK or a TSC brand, and see how they cut on your machine. I think you will find that thick grass will be the hardest, with stemmy brush surprisingly easier.

For instance, i mowed my severly overgrown paster in november, and it had 7' dog fennel and ragweed in it... some taller than the tractor cannopy.... barely touched the engine... in the back pasture I was cutting some 18" thick argentine bahai and bermuda.... you would had thought I was pulling stumps... and I have 32 pto hp....

You might try the 5' and take less of a bite as in a half or 3/4 width pass or a slower pass. Most people get spoiled and try to cut in too high a gear.

( You should see my 8N cutting..... 1st gear only /forums/images/graemlins/crazy.gif )

My light duty KK 5' hog is holding up fine, and I've cut the 1 - 1.5 inch woddy sapplings, heavy briars, a tall grass, and even scalped a few hidden rocks!
Keep whatever you get sharp, and properly serviced ( oil in gear box - grease in appropriate fittings, and paint scratches to prevent rust... and it will do fine... You will also find that hosing off grass cuttings will increase deck life. )

My yanmar 1700 is iffy on a 5' cutter.. no heavy stuff...but then, that is less pto hp than yours.

good luck!

Soundguy

 

[DK35vince]

I'm with Bird on this one.
I field mowed and light brush with a 5' standard duty cutter on a JD 850 with 22 PTO HP.
It was well matched to the tractor and I would have been dissapointed with a 4'.

 

[djradz]

I agree. Go with the light duty cutter at 5 ft. I think for what you're proposing to do you'll be just fine. Four foot would be OK but heck, my little Craftsman lawn tractor is 46", and that would take forever to cut what your proposing. Since you already are happy with the KK blade, I'd consider the KK rotary cutter. For about $550, you'll get a pretty husky cutter, that with the proper care can last you a lifetime.

 

[John_Mc]

As others have already noted, I would go for the 5 foot, "standard" duty. IF, as you say, you will be mowing several times per season, (say, once every month or so?) you should be OK with a 5 footer. If you let things really go between mowings, or only intend to mow once per season, then teh 4 footer might make more sense (of course, in this case you could always just take less of a "bite" with your 5 footer).

The first time you mow, you may have some difficulty with the 5 footer. Just take it slow and/or overlap a bit on each pass (so you are not cutting the full 5 ft on each pass). You'll probably want to go slow the first time or two anyway, to keep an eye out for rocks/stumps/etc.

 

[buck1]

Stay standard duty at 5' and you should be okay.