Comparing slip clutch rating to shear bolt rating

[rowbro]

Good day,

I am trying to figure out how to compare the rating of a shear bolt to a slip clutch rating in order to ensure my drive-line is set up to protect tractor and implement. My slip-clutches can be set to 1800Nm of torque, but I am struggling to find a comparable measure for the PTOs that only have shear bolts, and not slip clutches. Can someone please advise as to how these shear bolts are rated and how these can be compared to the torque ratings of slip clutches?

Thanks in advance.

 

[ptsg]

Not sure exactly what you're looking for but check some PTO shaft catalogues. They often list the breakdown torque for different types of protection on the PTO shaft, being clutch, shear bolt or other types of torque limiters.

Here is one for LaMagdalena shafts: https://www.lamagdalena.com/datos/descargas/archivo55/catalogo.pdf

 

[ptsg]

Bondioli Pavesi also has a great catalogue on all types of PTO shafts and gives great explanation on the shear bolts and clutch types. Even breaks down the bolt grade and the breakdown torque for each grade.

https://bondioli-pavesi.com//download/pdf/398CDS002EN00.pdf

 

[LouNY]

I prefer clutches to shear bolts most of the time.
When I set mine I loosen it way off and intentional slip good to clean up all the surfaces.
Then I'll start tightening it and using the implement if it slips in normal to light use I'll tighten it a bit more and use it again pushing it more towards the maximum I want it pushed, if it slips more then I feel it should I tighten it a bit more. When it will do the job I feel it should without slipping then it's in good shape.
It is a subjective method and not a precise method to exactly match a shear bolt, I've never seen a chart for a slip clutch telling you how tight to set the springs to equal a certain shear bolt that is a certain radius out on a pto shaft.
As both the bolt diameter and grade as well as the radius from the center of the shaft will all effect the shear strength.

 

[wirlybird]

I prefer clutches to shear bolts most of the time.
When I set mine I loosen it way off and intentional slip good to clean up all the surfaces.
Then I'll start tightening it and using the implement if it slips in normal to light use I'll tighten it a bit more and use it again pushing it more towards the maximum I want it pushed, if it slips more then I feel it should I tighten it a bit more. When it will do the job I feel it should without slipping then it's in good shape.
It is a subjective method and not a precise method to exactly match a shear bolt, I've never seen a chart for a slip clutch telling you how tight to set the springs to equal a certain shear bolt that is a certain radius out on a pto shaft.
As both the bolt diameter and grade as well as the radius from the center of the shaft will all effect the shear strength.

That is a decent method. Most slip clutch setup instructions will give you a basic setting such as, for spring type, turn the nuts until you can't turn the spring by hand then tight 1 to 1 1/2 turns.
From there adjust tighter or looser as needed for your implement.

Most implements will tell you what is required for a shear type setup. For instance mine all say to use a grade 2, 1/2 X 3 inch bolt. I think this is pretty standard.

 

[Doughknob]

http://site.alliedbolt.com/files/ShearStrength2.pdf

 

[Bill Guenthner]

Good day,

I am trying to figure out how to compare the rating of a shear bolt to a slip clutch rating in order to ensure my drive-line is set up to protect tractor and implement. My slip-clutches can be set to 1800Nm of torque, but I am struggling to find a comparable measure for the PTOs that only have shear bolts, and not slip clutches. Can someone please advise as to how these shear bolts are rated and how these can be compared to the torque ratings of slip clutches?

Thanks in advance.

It just doesn't matter.

 

[wirlybird]

I think you are trying to create a one to one comparison of two different protection methods. I don't think that works.
I think you need to see what the implement manufacturer recommends for driveline protection for that specific implement.
Slip clutch is better suited for certain implements/conditions while a shear bolt may be better suited for others.
Some implements may be well suited for either, such as a brush hog.
For instance, if you are mowing open fields with little chance of hitting anything that could damage the tractor or implement then a shear bolt may be fine and saves the cost and maintenance of the slip clutch.
However, if you are using a heavy duty rotary cutter in unknow or harsh conditions a slip clutch is likely a better choice.
Also something like a tiller would likely be breaking shear bolts frequently so a slip clutch is a better choice.

 

[Williy]

To be safe I would not go higher than a grade #2 as
bolts are cheap equipment is not!
Next time I hit the lumber company will get 3 grade
#2 bolts with lock nuts

willy

 

[jyoutz]

That is a decent method. Most slip clutch setup instructions will give you a basic setting such as, for spring type, turn the nuts until you can't turn the spring by hand then tight 1 to 1 1/2 turns.
From there adjust tighter or looser as needed for your implement.

Most implements will tell you what is required for a shear type setup. For instance mine all say to use a grade 2, 1/2 X 3 inch bolt. I think this is pretty standard.

I just follow the general slip clutch directions and continue 1.5 turns. Seems to work.

 

[5030]

I just follow the general slip clutch directions and continue 1.5 turns. Seems to work.

Same here with one exception. Every spring I'll back off the spring tension bolts on all the slip clutches and slip them with the PTO a few dozen revolutions to remove any corrosion that might have got there over the winter from sitting. I measure the bolt protrusion (base to head first so I can reset them to the slip torque spec. You don't have that issue where you are, but I'd still slip them once in a while if the equipment sits outside in the weather or you wash it.

 

[jyoutz]

Same here with one exception. Every spring I'll back off the spring tension bolts on all the slip clutches and slip them with the PTO a few dozen revolutions to remove any corrosion that might have got there over the winter from sitting. I measure the bolt protrusion (base to head first so I can reset them to the slip torque spec. You don't have that issue where you are, but I'd still slip them once in a while if the equipment sits outside in the weather or you wash it.

I adjust mine every few years. My cutter sits under a carport type of steel shelter, protected from heavy rain, but still gets moisture from blowing snow. Humidity is low where I’m at except during the summer monsoon season when it is humid. When I do slip it, it’s never been locked up.

 

[BeezFun]

Every spring I'll back off the spring tension bolts on all the slip clutches and slip them with the PTO a few dozen revolutions to remove any corrosion that might have got there over the winter from sitting. I measure the bolt protrusion (base to head first so I can reset them to the slip torque spec. You don't have that issue where you are, but I'd still slip them once in a while if the equipment sits outside in the weather or you wash it.

I've started doing the same thing. My neighbor had a relatively new JD bush hog he bought with his tractor, probably only 3 years old when he tore the PTO shaft all to pieces when he hit something. Asked me to help him look at it. Turns out the slip clutch plates were rusted/corroded together and didn't provide any protection. I would guess his mower sat outside on the dealers lot for who knows how long, then he had it 3 years. That was enough to freeze the plates together.

One other thing I do is check the temp of my clutch right after every time I use it by carefully touching it in case it's hot. If it's hot I know the clutch has started slipping and I can adjust it before the plates are burned up.

 

[Williy]

I don't have to go to the lumber company
for the bolts as my dealer is sending me some
Nice guy Mike

willy