Rotary Cutter 6' KK rotary cutter problem!!

Soundguy · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

( For now I will go with a grade 5 bolt and in the near future I will buy KK slip clutch option for my mower )

The harder bolt just needs more of a shock load to clip it.. I don't like that... less protection factor for the diveline.
I don't think the slip clutch is a 'fix' either... the load to make the clutch slip is fairly decent... Quick shock loads pop bolts.. but may not get 'much' slip from a clutch.. like say.. hanginf a blade on a stump and having a 90-100% slip goin on.. saving your trans from a stall situation.

( thought the folks at KK would have tried to make it right instead of blaming the PTO of the tractor. )

Why should the mower manufacturer have to 'fix' a tractor design that makes a shock load situation on the tractors pto.

Thos 'cheap' mowers are in use everywhere.. I have a 5' kk mower that has been used and abused.. on my 8n, NAA, and ex Nh1920 diesel that can run a 6' mower easilly. I've mowed in 7' tall weeds.. no problems.. course I have the clutch and can feather the engagement of the pto.. not slam-bang and go..

I don't see this as a mower fault.. but a tractor/pto issue.. that seems to be correctable by using a lower rpm at startup, and a different pto mode.. as evidenced by other posts here...

( A simple fix would be to have one blade offset to miss the second blade at startup )

Different height.. or different length.. I'm sure that would make for some interesting design calcs.... Seems like lower leading blade would be doing most of the cutting...

Soundguy

JerryG · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

Just a thought here. Does your engine idle down to the correct RPM? We find from time to time things that are not set to specifications from the factory. Examples: idle speed, high speed no load rpm, hydraulic pressure etc.

BamaRob · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

(
I don't see this as a mower fault.. but a tractor/pto issue.. that seems to be correctable by using a lower rpm at startup, and a different pto mode.. as evidenced by other posts here...
)

I was thinking the same thing, but didn't know how to say it without sounding offensive. With the "live" PTO on my Mahindra, if I push the clutch all the way in, engage the PTO with a KK 5' Kutter attached, and just release the clutch all the way out I get lots of shaking, banging, etc., even at idle RPMs. If however, I feather the clutch a little, I can start the PTO in an acceptable manner even at higher RPMs.

I don't have pushbutton PTO engagement, so I can't comment on an acceptable method of engaging the PTO on a Kutter, but I can't see how this tractor/PTO design is the implement manufacturer's fault. /forums/images/graemlins/confused.gif

Just my $0.02,

BR

Grizzman · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

One question I would like to ask you guys. Owners of Bushhog, Woods etc. Have you ever gotten under your mower and swung your blades? I have had several people tell me there is a design flaw in the KK blades because their bushhog blades don't touch, they pass by each other without contact on engagement. This would not be a issue if KK blades did not contact each other......period. KK said this is a problem with NEWER tractors with a live PTO. I guess if you buy a new tractor with a live PTO, then you are not supose to use a KK mower. Did'nt see that one in the manual or on KK website. All I got from KK folks was use a 5 grade bolt and buy a slip clutch! that will fix the problem. Well that is not a fix in my book. So everytime I use the mower, I have to make sure the PTO is in AUTO and I have to feather the clutch so the blade contact will not shear my PIN.

Farmwithjunk · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

Already commented earlier, but here goes again. I have a Woods BB840 (2 years old) and a Woods MD72 (7 years old)

NEITHER mower has blades that touch. They clear by almost an inch on the MD72 and nearly 3 inches on the bigger mower.

I get SOME vibration, for maybe 2 or 3 seconds, when first starting the blades spinning, but they smooth out quickly.

That's on a Deere with independant PTO or a Massey Ferguson with live power.

JerryG · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

they pass by each other without contact on engagement. 
Both blades are on the same plane. You can turn them to where they look like a half open pocket knife and they will hit. If they don't the stump jumper or the blade bar would have to be wide and the blades short. There are brush hogs that have this set up such as a Brown tree cutter (extreme example). Is your RPM the right speed when it is at idle? I don't mean how much fuel you are giving it. I mean the idle that is set with a screw (normally) on the fuel pump. If it is to high, then that would explain a lot and be very easily fixed.
 this is a problem with NEWER tractors with a live PTO 
This is a problem on some new tractors with an electric switch that controls the hydraulic PTO clutch. There are some others that are solenoid modulated to eliminate this problem.

Charolais · Sep 13, 2005

Re: 6\' KK rotary cutter problem!!

Grizzman, I checked on a set of blades for my 7' cutter back in June. Found that the 6' and 7' cutter use the same blade. There used to be a heavier blade for the 7 ' model but they no longer have it listed. So what KK did was make a stump jumper for the 6' model and a little bigger stump jumper for the 7' model but used the same length blade. That saved them from keeping another part in stock.

I'll agree with several of the other guys here. The problem isn't with the cutter. It's the tractor. A clutch is to allow you to start the motion of the shaft smoothly and slowly if need be. You're not getting that type of action with your set up.

I have one question about your PTO on the tractor. Is it hydraulic operated? Talk to your tractor dealer and see if he may know of a cure. He may have had this same thing happen before. There may be an adjustment that will soften the shock load.

When I start my KK it may take 8-10 seconds for it to smooth out before I release the PTO hand clutch lever all the way. And that's with the engine at idle (600 rpm's) I have a JD 820 MOCO hay conditioner. It's pretty much the same with it too. There's no way I could start that MOCO with a push button clutch if it didn't have some built in protection to give the conditioner time to get up to speed with the engine at idle. It has 3 PTO shafts connected together, a gear box that turns more gears for the rollers, a belt that turns the reel and a belt drive that turns the wobble box for the cutter. If I dumped the clutch on that I'd be picking up the pieces off the ground and the $$$$ would be flying.

I saw one post suggesting to start the engine with the PTO already engaged. Please don't try that. That can cause the crank shaft in the engine to break and several other parts as well.

See what can be done with the tractor to solve this problem first.

Soundguy · Sep 14, 2005

Re: 6\' KK rotary cutter problem!!

( I guess if you buy a new tractor with a live PTO, then you are not supose to use a KK mower. Did'nt see that one in the manual or on KK website )

Naaa.. I mowed for 3.5 years with my 5'KK on a tractor with live pto... never once sheared a pin on startup.. sheard them mostly on ant mounds...

What the other guys are telling you sounds right... it's not the mowers fault that any particular tractor has a whambamthankyoumam type pto.

Just think about it.. you can hundreds to thousands of pounds of metal in a pto powered device.. you simply can't shockload that much metal into action. PTO setups that don't have some sort of feathered engagement, are, IMHO a design flaw.

As has been mntioned.. there are remidies.. as you said.. starting in 'auto lets you feather.. some peoples push button pto already modulates.. etc. I really feel that the the plain 'starght-andgo-fullpower-darn-the-torpedos type units just did not incorporate any/enough forward thinging.

I also do not feel that using a hard bolt or a slip clutch is a 'good' answer for this specific problem, except.. that a slip clutch in line.. never hurts...

Soundguy

TonyV · Sep 14, 2005

Re: 6\' KK rotary cutter problem!!

If I understand all of this right, you've got two seperate issues here. The fact that the blades come in contact, and the fact that you're busting shear pins when you start up. The fact that the blades contact one another would have nothing to do with the shear pins of course, and they should straighten out fine after the cutter comes up to operating speed. Interesting though because I've never experienced this problem on my 5' KK that I've used for about 10 years now. I use to pull it with my old 8N (no live PTO..a real bummer when I got it stuck /forums/images/graemlins/crazy.gif) and now pull it with my Kubota L3400DT....live PTO with 2 stage clutch. No problems, aside from a little initial vibration, in either case. Given my limited experience, I have to agree with what others are saying in so much that its a setup issue. It is unfortunate however that KK couldn't design its product to be used across all possible operating platforms, but perhaps I expect too much. In any event, I think once you get use to engaging the PTO as others have suggested, it'll become second nature and the problem will take care of itself. I'm not sure that I'd go with the heavier duty shear pin as opposed to the pin that KK used initially though...that pin was chosen for a reason. Better to me to go with a slip clutch if your unable to feather the PTO in as others have described. Good luck with this and I hope all the great advice you've received in this thread works out for you.

...Tony

N80 · Sep 14, 2005

Re: 6\' KK rotary cutter problem!!

If I don't carefully 'feather' the PTO lever on my Kubota L4400, my JD LX6 mower and an old heavy duty 7' JD both clank and bang for a second. They both have slip clutches.

But I'm with Tony, I don't see how any of that, including the blades hitting, is violent enough to shear the bolt.

HammerFour · Sep 15, 2005

Re: 6\' KK rotary cutter problem!!

I wouldn't be that concerned about the fact that the blades can hit, during operation they will be swung out and that won't be an issue.

What would very much concern me is the sudden pto engagement...as another poster mentioned, that will tear up a lot of equipment as pto attachments aren't designed to go from 0 rpm to x rpm in an instant. The inertia of the rotating parts of the cutter are what is breaking the shear bolt, same as if you hit a big stump that stopped the thing from rotating at low rpm, the effect is the same, just in reverse.

I would only use the mechanism on that tractor that let's you ease the pto up to speed, I guess you could use the sudden starting method for low inertia devices like pto pumps or generators, but I wouldn't even use it then. Mechanical systems don't like sudden starts and stops, it breaks stuff.

NoTrespassing · Sep 16, 2005

Re: 6\' KK rotary cutter problem!!

Could someone explain the PTO system on these tractors? When is it recommended that manual be used vs auto?

I use a 6' KK without a problem. I slowly let out the clutch on when engaging the pto. I sometimes need to lubricate the blade pivot points to make sure they extend all the way and do not fold back slightly and become unbalanced.

One possible way to avoid the problem would be to manually fold the blades in the opposite direction before engaging the pto. That way on start up they would swing to cutting position rather than swinging in to each other.

It sure sounds like the option to use the clutch to engage the pto is the real answer. Is it that much of a problem to engage it that way?

Kevin

have_blue · Sep 16, 2005

Re: 6\' KK rotary cutter problem!!

( Different height.. or different length.. I'm sure that would make for some interesting design calcs.... Seems like lower leading blade would be doing most of the cutting...
Soundguy )

Could be the design. Maybe the stump jumper diameter is too small and the blades are too long. I'm sitting here trying to imagine how my blades could ever touch, and I can't right now. I'll check next time I go the the tractor shed, and I may be surprised.

In Grizzman's case, looks like there is enough blame to go around. A tractor should provide a way to feather the PTO up to speed, and a cutter's blades should not ever touch.

KennyV · Sep 17, 2005

Re: 6\' KK rotary cutter problem!!

Wow you are having this type problem starting a rotary cutter…?
Can you imagine what would happen if you used that type of start up on something with a lot of weight /forums/images/graemlins/shocked.gif, like the rotor in a large generator or the heavy drum in a medium/large chipper shredder?
This sounds like an oversight on the tractor drive engagement … . KennyV.

skipmarcy · Sep 17, 2005

Re: 6\' KK rotary cutter problem!!

My Mahindra 4110 PTO system has the 1) 3 position manual lever to change from neutral to either 540 or 1000 rpms. 2) A dash mounted switch to change to either manual or auto engagement, as well as an off position 3) A steering column mounted push button switch to turn PTO on and off. In the manual mode, when you push the column mounted switch on, the PTO comes on and stays on until you push the button again. In the auto mode, you push the button on and the PTO will come on but if you push the clutch in, it will stop it until you release the clutch again. Also, raising the 3 pt. will stop the PTO once it reaches a certain height until you lower it again. The electric solenoid that is activated from the switching system causes hydraulic pressure to engage a hydraulic clutch inside the front transmission that engages the mechanical shafts to run the PTO. The input shaft that the hydraulic clutch is on runs constantly when the engine is running via a shaft that runs off the pressure plate - using the clutch pedal does not stop this shaft, you are only stopping the transmission input shaft when you push the clutch - it runs off the clutch disc. I can see no benefit in using the clutch to engage the PTO in the auto mode - you are still engaging the PTO via an electrical switch, same as if you were using the push button in the manual mode. The only benefit that I could possibly see is that you can disengage the switch more quickly with your foot on the clutch than you can pushing the button switch with your finger - maybe. As I have already stated, I haven't broken a grade 3 shear bolt in my 6' cutter in about 3 years now, and I would guess I have started that cutter well over 75 times on that same bolt. My tractor idles right about 700 or 800 rpm's and that's where I engage it 95% of the time. I have engaged it as high as 1800 rpm's a couple of times, but try not to do this often, only in severe circumstances. My old cutter has the square PTO shaft and it has alot of slop/wear in it, has a large stump jumper and 2 heavy blades and it will shear bolts when I hit something that shouldn't be hit, but my tractor has never broken a bolt in it. There is some very slim chance that something is wrong with his tractor causing the bolts to shear, but I can't imagine what it would be from my experiences. I would have to lay the blame on the implement if his tractor is indeed operating just like mine.

Grizzman · Sep 19, 2005

Re: 6\' KK rotary cutter problem!!

Skip

You are correct putting the PTO in Auto mode and slowly letting out the clutch, made zero difference. I took the blades off of the KK last weekend for closer examination. The blades freeswing and hit each other mid-way and on the tips. I don't see how this could be a issue with the tractors PTO. The contact is only made on engagement, once the blades are apart they work and cut fine. The first cutter did the same exact thing as second one. I engage the PTO at idle speed at 700-800 rpms range. It is frustrating to pay $800 bucks for a cutter and it has a design flaw, especially with no support from the manufacturer. I guess I will live with it until next spring. I am going to trade it in on a Bushhog or Woods Cutter.

DrewL · Sep 19, 2005

Re: 6\' KK rotary cutter problem!!

I have a 5ft KK and the thing is as advertised. My humble opinion is.......... to continually shear the pin upon start-up it is doing as designed, but why? Get back to basics...............something is up . I would not blame KK or the tractor untill it is determined what is going on

Charolais · Sep 19, 2005

Re: 6\' KK rotary cutter problem!!

Did you start it up without the blades?

skipmarcy · Sep 19, 2005

Re: 6\' KK rotary cutter problem!!

Grizzman - By the way, what diameter bolt are you using? My shaft uses a 7/16". I use a locnut or double-nut and leave just a little bit of slack when I tighten it up so the bolt will move back & forth maybe 1/16" or 1/8". If you are using a 3/8" or smaller bolt, maybe that's the problem. If your shaft is drilled for the smaller size, maybe you can drill it out to accept a 7/16" diameter bolt.

Yalerider · Sep 20, 2005

Re: 6\' KK rotary cutter problem!!

It sounds like this is a "I have a clutch engaged PTO and its better" vs. a "you have a electronic PTO and their not very good" issue. I have used both and both have their advantages and disadvantages. The fact is he has an electronic PTO like I have. I like having the switch to use either live or independant PTO. I don't have any issues shearing pins on my Land Pride 5' rotary cutter, and I don't think it is a "design flaw" in the tractor. I use a grade 5 bolt instead of a 3 so I don't shear bolts all the time when hitting small trees.