Rotary Cutter Rotary Cutter

JimMorrissey · May 18, 2004

Bought a 4' rotary cutter for my BX the other day ($450). It has no names on it at all, but looks just like a bush hog.

My question is....do all brush cutters / rotary cutters vibrate and make loud noises while just spinning (not mowing)? I have to wear ear protection while using it and it shakes the whole tractor. I have a feeling the Woods version doesn't do this. Basically, I'm wondering if they are all crude bashers to be used the least amout possible....or did I get a homemade, out of balance piece of junk? --It destroys almost everything it hits, including some descent sized small trees without much problem...It's just very, very crude.

Thanks,

Jim

Laminarman · May 18, 2004

Hmm. I start up my 6' Land Pride and it wobbles my TC40DA quite a bit for a second, but then when she's humming after a few seconds (about two), the whole thing just hums and whirs. I did have an incident when it banged the tractor around and the blades got crossed underneath. Check the blades, preferably with the PTO and tractor off. /forums/images/graemlins/tongue.gif..good luck

wisconsinguy · May 19, 2004

hi

I have a 4 foot John Deere cutter on a 2210 and it is very quiet, can't really hear it run. It does shake for a few seconds till the blades are straightened out but after that it is real smooth. I'd take a look underneath, the blades should move, maybe one is froze up or bent or something.

Phil

KiotiJohn · May 19, 2004

Jim there are a few reasons for the wobbling. My first choice would be that the blades are not balanced. One may be well cut down and lighter than the other. Also a bent shaft would cause it. One could still cut with it depending on the amount of bend, but it would wobble. It could also be that somethingn is simply loose. If you have not done so, make sure you go through ALL the bolts and assure that they are torqued well down as the blades can come flying off and do a lot of damage, even death. Lift the mower into the air and turn off the tractor. Reach under and carefully inspect the blades, turning them by hand to see if there is any bending to the shaft. Look for chunks of metal that may have been broken off causing out of balance blades. It's not unusual for a well used brush mower to not have been cared properly for, and wobbling is common. Just make sure everything is right before using it again. It may save your or someone else's life. John

Soundguy · May 19, 2004

My brush cutters wobble a bit as they spin up.. but are otherwise fine when running at full speed.

Lif that cutter up with the 3pt, and then block it there.. disconnect the pto shaft and let it hang FREE

Observe the blades on the stump jumper. They will need to be able to pivot on that stump jumper. I've seen some blades rusted in place where the blades did not stand directly out from the stump jumper.. and when they spun up.. were of course unballanced.

If that is your case.. hit them with some pb blaster.. and then give them a good whack on the back side and get them to lossen up so that can swing straight out. Also.. measur ethe blades tip to bolt on each side.. make sure you havn't lost a blade tip. Also lok the blades over.. if one is worn down to a nub and the other is new.. that will unballance them. These aren't ginsu knives and don't need to be 100% same weight etc..You will always get minro imperfections between the two when hitting rocks.. etc. but the closer they are.. they better they feel running.

Some go to the trouble to remov ethem and weight them and grind them down to match.. While I'm sure this gives you a grat ballance.. I think that it is more or less 'lost' time and diminished gains... for one.. you are probably grinding off excess metal, and that will prematurely age the blade.. and two.. It isn't a 10 minute job either... like I said.. these aren't scalpels.. mor e like a swinging axe. Just get them safely on there, and real close to the same size, and go with it.

Also observe the stump jumper.. make sure it doesn't wobble or have a huge dent in it.

Soundguy

OkieG · May 19, 2004

do all brush cutters / rotary cutters vibrate and make loud noises while just spinning (not mowing)? 

No. Should be just a whirring sound of the blades spinning through the air, with little or no vibration. Good advice from KiotiJohn and Soundguy.

OkieG

BB_TX · May 19, 2004

After several years of cutting brush, deadfall, and hitting stuff that washed out of the creek, mine vibrates more than when new, but not enough to be of concern.
Soundguy give very good advice on making sure your blades are loose. This is essential both for balance and to make sure the blades can absorb the shock of hitting objects, rather than transfering that shock to your PTO shaft.
Each spring I pull my tractor up to the side of the cutter, securely attach a chain from my FEL to the opposite side of the cutter and raise it up until vertical but still setting on the ground. Then I back up just enough to the cutter leans back toward the tractor. That way I have safe access to the full underside of the cutter without having to crawl under it. I make sure the blades are able to swing freely, and if not, loosen them. The blades should be free enough to hang straight down when the cutter is turned up like that. Then I put some heavy weight oil or gear lube on the pivot pin. Once a season is all it needs. I can easily sharpen the blades while I have it up.
Make sure your gearbox is tight to the deck or tighten it while you have it up.

KiotiJohn · May 21, 2004

( Observe the blades on the stump jumper. They will need to be able to pivot on that stump jumper. I've seen some blades rusted in place where the blades did not stand directly out from the stump jumper.. and when they spun up.. were of course unballanced.)
Great suggestion Soundguy. I hadn't thought about that even though I experienced that situation many years ago. Too many years ago!! John

JimMorrissey · May 22, 2004

All,

Thanks for the input. I will check the blades. For the record, it's new so the blades are not out of wack. They may not be tightened enough though. I'll take a look. Frankly, I think I'm just mad that I didn't spend the extra $450 and get a real Woods attachment! I'm now hyper-sensitive to any problems with my new "junk". I never buy junk.....Not sure why I bought this. It's just not the finely machined piece of equipment I envisioned; however, it does work and work well. You wouldn't believe the "brush" I cut to pieces. It's amazing what the thing with destroy. Basically, anything the BX can drive over, it will cut up....I'm talking 1.5 - 2 inches in diameter.

Jim

KiotiJohn · May 24, 2004

( Basically, anything the BX can drive over, it will cut up....I'm talking 1.5 - 2 inches in diameter )
Jim, I respectfully suggest that when you're going to cut anything over 1" in diameter with that mower that you slowly back into it, let it cut a little, back again, until you've cut it down. That mower is most likely rated for 1" material and just simply running right over it and cutting it all at once may damage the mower. You'll be pleased with the results, and I've cut up to three inch doing it this way with no damage to the mower as I'm only really cutting a little at a time. John

OkieG · May 24, 2004

slowly back into it 

Backing into the target is a useful technique, but has been the source of trouble for me. When you back up, if the back of the cutter deck meets resistance, the front of the cutter can raise up if there is appropriate slack in the toplink. The geometry on my small tractor (and probably the BX as well) allows the front of the deck to raise enough to contact the PTO shaft shield. First couple times it seems like no big deal, but the rotating shaft will quickly wear a hole in the shield where it's pinched between the spinning PTO shaft and the front of the deck.

Backing into thick brush and saplings is such an integral part of my brush hogging technique that contact was occuring all the time. The shield was ruined and even though I tried to avoid shaft to deck contact, I knew it wouldn't be long before the shaft and/or deck would be damaged.

Shortening the top link while backing, then slowly lengthening it to drop it on the brush prevents contact. But this very difficult to do with a manual toplink.

There is currently a thread in Customization titled "Your Best Additions to your Tractor". I am fortunate enough to have plenty of implements to play with, and my entry on that thread is a vote for an hydraulic toplink.

Any 3PH implement will increase it's usefulness with an hyd. Toplink. It usually takes some planning (and money) to get one up and running, but the benefits are amazing...especially for a brush hog and boxblade.

Anyway, my long-winded point is--Be careful not to let the deck contact the PTO shield while backing into anything with the blades spinning.

OkieG

KiotiJohn · May 25, 2004

( The shield was ruined and even though I tried to avoid shaft to deck contact, I knew it wouldn't be long before the shaft and/or deck would be damaged.)
OkieG, I've never had a problem with my PTO shaft hitting. Does your brush hog have a slotted connetor at the top link? Mine does and setting that properly is probably the reason I don't have the hitting problem, but I'm not sure. Could it be that the PTO shaft is not exactly the right length? I remember reading something about testing whether the shaft hits while you're originally measuring for cutting the shaft. The shaft should never be able to hit, and mine doesn't, even when backing into ditches etc. with drastic angles. It's an interesting dilema. John

Soundguy · May 25, 2004

( testing whether the shaft hits while you're originally measuring for cutting the shaft )

Shortening a toplink will help that too.

Soundguy

OkieG · May 25, 2004

John,
I am certain my ability to communicate has deteriorated. I am not describing well what I wish to convey. I'm sorry if the description of my brush hog problem is poor. Perhaps, a picture or two would help. Maybe I can take a couple and post them later.

The problem isn't that the shaft is too long. For example, the PTO shaft isn't collapsing to it's shortest length and bottoming out with contact inside the shaft (ie shaft too long). Rather, the slack in the 3PH toplink allows the front of the brush hog to raise up enough (when backing up against brush) so that the front edge of the deck contacts the PTO shaft shield.

If the 3PH toplink is shortened (as per Soundguy), there is not enough "slack" to allow contact, which is good. But, there is also a loss of abiltiy to terrain follow through dips, which isn't so good.

It is much too tedious to adjust the manual toplink when frequent adjustments are needed. The hyd. toptink has changed all that for the better, but if I don't take enough slack out when backing, there can still be contact.

I like pictures a bunch...and this is a situation where one might be worth a thousand words. Maybe later today.
Thanks,

OkieG

Soundguy · May 25, 2004

The slack should be taken up by a 'U' piect afixed to the rotary mowers toplink connection area. Most mowers I see nowadays have it... if the owner bothered to install it.

Soundguy

OkieG · May 25, 2004

John,
I have begun a thread in the Owning/Operating section, so as not to clutter Jim's thread with my problems. Here's the link: How Much Slack Do You Give Your BrushHog?

OkieG

stephan · May 26, 2004

If the device is new and it vibrates or makes a lot of noise there is a problem with it. Mine, while running, makes no more noise then the tractor and yes I wear ear protection but as I said that is to prevent noise from the tractor engine.

You could drop the blades and the rotor (arm that holds the blades) from the gear box and run the PTO to see if it still vibrates. It'd be most probable that the vibration would be in the arm and blades if it is in the PTO shaft or the gearbox then that'd be very strange and harder to fix.

Assuming the problem to be with arm and blades measure them with the thought that there is a line exactly in the middle (where the arm attaches to the gearbox) running across the arm where one half exactly mirror the other. Differences in length, weight, thickness etc could be causing the vibration. put the arm back on the cutter and ensure it is tightly bolted/attached to the gearbox. Measure the distance from the deck to the furthest extremity of the arm/rotor. If this measurement is not the same then the gearbox shaft might be bend.

All in all if its new take it back.

edv · May 26, 2004

I assume this is a new cutter....A 4 ft cutter "new" for $450 would be considered an economy cutter...and yes many economy cutters have no name, no serial number, etc...

Chances the blades are not balanced, or more than likely the blade carrier is not balanced. Vibrations are common on all cutters at start up..however once they get going the cutter should operate quite smoothly...safety is a concern with any cutter that continues to vibrate...blades can come off!! I would inspect cutter or take it back to the dealer you purchased unit from. You are better safe than sorry.

Edv

nomad · May 30, 2004

I have a feeling that yours is probably designed to operate at lower speeed than the other cutters. All cutters are sensitive to the speed. If a cutter is designed to operate at X rpm speed and if you operate it at X+1 rpm speed then, it will most likely vibrate due to its designed balance. If you operate it at X+2 rpm, then smaller unbalanced masses in the blade and the disc will start to play important roles. Remember nothing is zero-mass balanced - always there is some nonhomogenousity in the mass distribution in rotating components. Also, when starting the cutter increase its speed gradually in time. This will help on smooth transition from the rest to the full/rated speed. If you increase the speed suddenly, it will vibrate and damping of the vibrations will take more time.