Rotary Cutter rotary cutter question

[gav64]

I am looking into a rotary cutter to use a couple of times a year to cut about 2 acres of forest underbrush, plenty of rocks out there.
which is a better choice, slip clutch or shear bolt. I am more worried about the tractor (hst tranny) than the cutter.
Any recomendations for cutters for this application. glenn

 

[Farmwithjunk]

I am looking into a rotary cutter to use a couple of times a year to cut about 2 acres of forest underbrush, plenty of rocks out there.
which is a better choice, slip clutch or shear bolt. I am more worried about the tractor (hst tranny) than the cutter.
Any recomendations for cutters for this application. glenn

The MORE you need the protection, the MORE VALUEABLE a slip clutch becomes. Shear bolts will also drive you bonkers in conditions like you described. You'll be on the ground changing bolts instead of mowing.

Just make sure the slip clutch is adjusted correctly and able to slip when needed.

 

[HD Labs]

I am wondering the same thing myself. If the slip clutch never slips and gets seized up then it does me no good. On the otherhand I don't want to have to change shear bolts every time I hit a rock or stump. How often is enough to adjust slip clutch? Any hints on making sure its adjusted properly? I am looking to buy cutter as well and am hung up between WOods BB60 and Bush Hog Squealer 600. Specs seem to be the same but woods is about $300 more. Like the orange paint and the 5 year gear box warranty though.

 

[MrJimi]

Is there an easy way of checking a slip clutch just prior to mowing, if its stuck it would the same as welded?

Jim

 

[Farmwithjunk]

I am wondering the same thing myself. If the slip clutch never slips and gets seized up then it does me no good. On the otherhand I don't want to have to change shear bolts every time I hit a rock or stump. How often is enough to adjust slip clutch? Any hints on making sure its adjusted properly? I am looking to buy cutter as well and am hung up between WOods BB60 and Bush Hog Squealer 600. Specs seem to be the same but woods is about $300 more. Like the orange paint and the 5 year gear box warranty though.

OK... Here goes. This usually gets about a thousand "No, this is how you do it" replies, but here we go.

Find the 6 or 8 (depending on brand of slip clutch) bolts that hold the clutch sandwiched together. Untighten them 'till springs are out of tension. With mower hooked to the tractor, start PTO. That SHOULD make it slip. If clutch is siezed, shut down everything. Take a big spud bar or something simular and "lock" blade carrier (i.e. stumpjumper) so it can't turn. Apply PTO S.L.O.W.L.Y. and carefully. That will make it slip. Once it's free, remove spud bar (shut down tractor/PTO while removing bar) Let it slip under power for a couple minutes. Shut everything down, and re-tighten slip clutch bolts PER SPECS IN MANUAL. Every brand of clutch and every HP rating has its own specs. (Stack height of spring/bolt/nut) That's it. Install gaurds and start mowing.

I do mine once in the spring and again about halfway through the season. If the mower sits out in the rain, maybe a time or 2 more than that. It takes all of 1/2 hour and you'll never have to stop and search for ANOTHER shear bolt.

 

[Soundguy]

The MORE you need the protection, the MORE VALUEABLE a slip clutch becomes. Shear bolts will also drive you bonkers in conditions like you described. You'll be on the ground changing bolts instead of mowing.

Just make sure the slip clutch is adjusted correctly and able to slip when needed.

FWJ.. I'm thinking that if he only mows 2x per year.. he's gonna spend more time adjusting, slipping/checking his clutch each time he mows.. vs changeing a few gr2 shear pins.

If he mowed often.. it would be a different story altogether..

Soundguy

 

[HD Labs]

I'm a little slow at understanding how the slip clutch actually works. Could someone explain that a little and maybe that would help him to understand the concept as to how it works and why or why not it would be better for his situation.
I on the otherhand probably would use mine at least every 6-8 weeks but wouldn't necessarily use it in the rough stuff to cause it to slip. Could this affect how often it needs to be inspected/serviced?
I only have one area that really has any rocks to speak of and the rest is fairly well maintained.
May rarely try to forge a new path into some sapplings but more often than not just maintenance. What would you get SOundguy? I think I am safe to assume that Farmwithjunk would get slip clutch???

 

[CDsdad]

I'll probably get corrected, but anyway.

You hit a stump, rock, terrace row, bottom out or whatever with your bushhog. Instead of stalling or binding your tractor pto and transmission when your bushhog stalls, the slip clutch allows the tractor pto to keep turning even when the implement stalls. It is the weak link in the connection between your tractor and bushhog. After you get the implement out of a bind and stress off the slipclutch, the implement will return to normal operating speed if it ain't tore up.

Hope that's what you were looking for. As far as mechanics of the thing, I'd have to draw it to explain it. Maybe somebody else can explain better.

 

[Soundguy]

My 2 large mowers ( 10' and 15' ) both have torque limiters on them ( slip clutch )

I like them just fine. My 5' rotary mower has a shear bolt.. I'm ok with that too. I don't find it a hard chore to line up a shaft and yoke, and then drive a slug out with a punch, and then slide a new bolt in, and put a locknut onit with 2 wrenches. I carry the wrenches a small hammer and the punch in the tractor tool box along with some shear bolts.. It's really no big deal. Also.. once you have mowed an area often enough.. all the rocks are flat!

For what to use? I look at it kind of as a money / repair / repalce issue, and also take into account where it will be mowing.. etc.

For sure.. a properly adjusted slip clutch will give you some good protection with no bolts to change.... however.. that soft grade 2 bolt bops like a baloon when you feed 30 hp thru a driveline. My mower has popped a shear bolt on an ant mound... and I never felt it.. nada.. nothing...

Lots of equipment uses shear bolts.

I fthe fellow is gonna be good about adjusting his clutch prior to each mowing.. then that will be a real safe bet. If he forgets naw and then.. go with shear botls.. all you have to do is forget once with a slip clutch.. and you may have a driveline with -0- protection.

Also.. look at mower and tractor. I don't want the expense of replacing a 10' or a 15' mower.. or the tranny in a 75-95 hp machine.

On the other hand.. a gearbox o5' mower ? that's realitively cheap (grin). i do think shear bolt protection is -fine- for the averagfe user.. and slip clutch is extra insurance. As a test.. if you have a smooth shaft coupled slip clutch, you can always adjust then attach with a soft bolt.. mow.. and then when an issue arises.. see what goes first.. the soft bolt.. or the clutchslipping... That will tell you a bit..

As for how a slip clutch works.. it's just a torque limiter.. has disc;s in it that are held in contact by pressure from the adjustment bolts/springs.. That is.. one sod eof the drive line is not permanently coupled to the other side.. the connection is rigid.. but when your input torque overcomes the tension on the nuts/spings, and the output is in a bind ( rock/stump.. etc ).. then the force overcomes the pressure/friction holding the clutch coupled, and the input slips.. thus letting the tractor pto still spin even if the mower blades are stopped or slowed.. that help any? in this case.. a picture / diagram would be worth 1000 words.. etc.


Soundguy

 

[Farmwithjunk]

FWJ.. I'm thinking that if he only mows 2x per year.. he's gonna spend more time adjusting, slipping/checking his clutch each time he mows.. vs changeing a few gr2 shear pins.

If he mowed often.. it would be a different story altogether..

Soundguy

In the original post, he mentioned cutting 2 times a year.....In a lot with stumps and plenty of rocks. Under conditions like that, I'd hesitate to use a mower that was offered with only a shear bolt. (probably light duty mower). All the good mid duty and heavy duty mowers I know of all come standard with slip clutch.

I'm just not a shear bolt advocate, in any conditions. Also, a great deal would depend on how much a person wanted to spend, I suppose.

 

[HD Labs]

Thanks Soundguy and CDsDad. I do understand how it works a bit better now. I will be using the cutter with a Ford 8n and Massey 240 (23HP-34HP I belive). DOes that have any bearing on slip clutch shear bolt issue? would one be better over the other with the HP tractor I will be using vs. cutter/gearbox size?
I am beginning to beleive that for my application I will be better off with shear bolt. Thanks again.

 

[woodlandfarms]

So, can you double your protection by using a slip clutch and some sort of sheer pin together?

 

[Farmwithjunk]

So, can you double your protection by using a slip clutch and some sort of sheer pin together?

Which ever one is "set" to let go with least effort will win out. no real advantage gained IMHO.

 

[CDsdad]

If your slipclutch malfunctioned a shear bolt would prevent damage.

If your bolt didn't shear a slipclutch would prevent damage.

I've never seen anything with both, though. To me the ultimate protection is a shear bolt as long as it's the proper grade. I do own a bushhog with a slipclutch, though. I've never had a problem with it, works fine.

 

[Soundguy]

As Farm and CD points out.. When a stoppage occours.. whichever is the weakest of yuor driveline components will let go first. That may be the shear pin if the clutch is stuck or misadjusted.. It may be the clutch. So.. yes.. i guess you could say a clutch held on by a grade 2 bolt gave you the benefits of both devices, and the limitations of both devices.. with the exception that if the slip clutch malfunctioned.. the bolt would shear.

IMHO.. the engineers that design the torque limitation on a device know about the device. That is.. if the engineer set it up to be shear pin protected.. then.. I'd have to think that the shear pin met at least -minimum- protection standards.

FWJ is correct when he points out that you see slip clutches on many o fthe HD mowers.. and virtuall all mowers over 6' - 7'.. etc.

My take on that is that the larger the mower.. the larger the tractor.. and the more torque the driveline will be under when cutting... thus making a shear bolt less effective as it may pop too soon when experienceing a heavy load while cutting thick material..

The biggest thing to remember is that you MUST service your slip clutch at regular intervals to keep it functioning correctly.. and.. it is a friction based device... DO expect it to eventually wear out.. just like brake pads.. or transmission clutches.. ( I'd expect to get alot of service years out of a slip clutch that wasn't abused heavilly, and was maintained correctly.. )

Soundguy

 

[RalphVa]

My Gravely brush hog had a slip clutch. My current JD LX4 has a shear bolt. Went the shear bolt route because my neighbor's 30 year old bigger JD uses only a shear bolt, and it didn't break any gears,etc. with lots of different people using it over the years. I've only had to replace the shear bolt twice in 2 years on my LX4. It's a really simple job once I cut the silly plastic sheath away that projected over the U-joint and back over where the shear bolt is. The first time, there was no bolt to remove or anything. It was just gone. The second time, the main part of the bolt was still in the shaft. Just had to poke it out with a screwdriver.

Slip clutches just work like the clutch on your car, pickup or old tractor. I just has a disc held in place against rotation by some springs. The spring tension is adjustable with some lock nuts. You need to carefully follow the instructions for resetting the spring tension. I never had to do this on the Gravely, neither on the internal slip clutch built into it nor the couple of slip clutches on the older implements that I used it on.

Ralph

 

[Neophyte]

If you are only cutting a couple of times a year, I wouldn't worry too much about which rotary cutter you choose. An economy model should work fine for your needs. You may even want to look for a used cutter.

Slip Clutches can easily be added later on. Save your money and try the shear bolt route. If you don't like it, you can add the slip clutch later.

I will say that in the past couple of days I must have gone through about 7 shear bolts while rotary cutting (rocks, 2" trees, ground, etc.). Having to stop so often can be pretty frustrating. I was using Grade 2 bolts on my Howse 500 even though it actually calls for Grade 5. Many people out there will use Grade 5 bolts even without a Slip Clutch. I couldn't take it any more, so I finally ventured to Grade 5. Start with Grade 2 and if you find yourself replacing them too often, then you can always move up to Grade 5 . Whatever you do, don't venture beyond Grade 5.

Like others have mentioned, keep some spare bolts on your tractor along with the tools you need to change them.

You may need to special order them online or through your local fastener company, but you could also find a Grade BB bolt that falls somewhere between a Grade 2 and Grade 5. Does anyone know of a good source for Grade BB bolts?

Whichever RC you get, make sure it has guards on the front and rear. If the cutter does not have them, you can make some on the cheap using cut up mudflaps (Soundguy's good advice).