speaking of a slip clutch,

BrettW · Mar 19, 2003

Am I correct in buying a #2 bolt as a sheer pin? thanks again and I still havn't found a sheer pin yet. I looked where the implement is attached and only saw a spring loaded bolt that lets you remove the shaft.

em14 · Mar 19, 2003

Check your manual and it will tell you what you need for a shear pin ... many simply use a #2 bolt of a certain diameter ... some may use a #5 but the only way to know is to check your manual or ask your dealers parts guys ... also I think that most will be bolts (at least on Ag related) ... if not most farmers will have "adapted" a bolt ... the wrong hardness could be expensive and dangerous ...
Leo

JohnMiller3 · Mar 19, 2003

Am I correct in buying a #2 bolt as a sheer pin?

What does your implement manuals show for replacement? What brands do you have?

Rule of thumb is to use Grade 2 bolts (of course the proper diameter as well) for shearing purposes ~~ under 40 PTO hp...

You can purchase a 2-plate slip clutch assembly and retrofit your implement for basically under $100. if you're spending more time replacing shear bolts versus doing the work with the implement in question...

(Remember all slip clutches will have to be adjusted to your tractor's PTO hp output...ex. an aftermarket slip clutch preadjusted to slip ~~ @ 600 newtons won't slip at all being used on a 20 PTO hp tractor... the manufacturer doesn't know what size tractor the implement will be used on...)

Rch · Mar 19, 2003

BrettW, I've got a Lucknow snowblower and the shear pin is an intergal part of the universal joint that goes on the tractor PTO /forums/images/graemlins/mad.gif. The safety shield on the tractor AND the flared end of the safety shroud on the shaft may be hiding it. They make it hard to change it in the cold, especially at night on my rig.

OverlyRun · Mar 19, 2003

My first year mowing with the rotary cutter gave me lots of practice replacing shear pins...it can be done in about 3 minutes if you've got some bolts (#2) and the wrneches in the on-board toolbox. But if you're out of bolts that day, you're out of business. So I got the slip clutch which takes about 15 minutes at the end of mowing season to loosen and insure still slips....will take a little longer to tighten in at the beginning of mowing season...but I still have the same, now-unused, shear bolts I had when the slip clutch arrived.

I don't know which protects the drive train better....the shear pins seem to snap pretty easily, maybe more consistently than a mis-tightened slip clutch? Is there any science that answers this question?

Chas

BrettW · Mar 20, 2003

What's your PTO hp? Mine is 20, thanks again for all the replys. bw

JohnMiller3 · Mar 20, 2003

the shear pin is an intergal part of the universal joint that goes on the tractor PTO 

Hi Ray,

Do you have a photo of the setup you're describing?

Shear pins and slip clutches are always placed at the "implement" end... never on the tractor side (because of the splined PTO shaft)...

I'd be interested in seeing this new design that you are using...

JimMc · Mar 20, 2003

There is a driveline protection commonly called an inline shear bolt. Most inline and slip clutch drivelines are splined on both ends. If your inline shaft has the shear bolt at the tractor end, it needs to be reversed. The point of driveline protection is not to protect from the forces coming from the tractor, it is to protect the driveline from forces coming from the implement. In the case of a rotary cutter, the sudden shock of hitting something unexpected and bringing all that rotating mass to a sudden stop. Placing the driveline protection at the tractor end normally results in twisted PTO's.

John, I'll try to find the picture of an inline shear bolt and attach it.

JimMc · Mar 20, 2003

Found it. The picture shows the driveline without the shiedling in place. Of course, they are supplied with shielding installed and it should always be used.

This device prevents overloading by means of a shear bolt of specified size. When the bolt shears off, the hub and yoke assembly is kept together by a ball bearing ring which allows the two parts to rotate independent of each other. It is mounted on the implement side.

Advantages are that it is much easier to inspect and change out when it shears. Disadvantage is the cost is approximately $10 more. Don't look for this in price sensitive applications such as light duty cutters.

JohnMiller3 · Mar 20, 2003

Thanks Jim for the pix... I've seen the ones Bondioli has made but for higher horsepower units and "It is mounted on the implement side... as we've both already stated... (probably used more in Europe than the U.S. I imagine...)