HayDR
Veteran Member, Approved Advertiser
Safety devices are matched to the torque range of a PTO. The key is knowing what Catagory PTO the application requires and then match the safety device to the PTO.
Determining the exact shear bolt
- Thread starter nomad
- Start date
</font><font color="blue" class="small">( If the shear pin is your weakest point, why do you consider design optimization poor quality. You start with a set of design parameters and stay as close to them as possible, erring on the strong side. Over design is wasteful and in the end hurts the customer as they will be paying for it. )</font>
I think we are confused (in communication) here in the steps of design.? The shear pin isn't designed yet, but (in your previous post) you already started with Grade2 (for its price/availability/etc). So, you already selected Grade2. Now, designing of attachment will be affected also by this early selection of the pin and the result (attachment) will be "relatively" poorer quality (which you may call optimum design) since your design travels around Grade2 use. We are saying same thing up to now. But, the problem starts here; the tolerance in the design. This farming field applications (unlike other industries) require larger tolerances in the designs because farmers are using their implements in very different conditions. I agree in that it's in their responsibility of farmers using them in not-mentioned conditions of farmers. But changing an implement just for a shear pin isn't reasonable and isn't practical. So, this problem of selecting the shear pin in real application requires a solution, at least in my opinion based on farmers' complaints here.
</font><font color="blue" class="small">( As far as the rest goes:
Aluminum is a pretty poor choice for a test material as it reacts significantly different than ferrous materials. )</font>
As I said before, I'm not good at material science details. Aluminum may not be a good selection as its characteristics is different than ferrous materials like the steel. But I still think there must probably be some sufficient analogy between the deformations of aluminum and steel. I think a rough/approximate mathematical model using some symmetries can be made for the deformation path of aluminum and steel under the same forces. and modelling deformation parts of them only will be sufficient. Anyways, this needs further study, but who cares about farmers' shear pin?, except Nomad;-).
I think we are confused (in communication) here in the steps of design.? The shear pin isn't designed yet, but (in your previous post) you already started with Grade2 (for its price/availability/etc). So, you already selected Grade2. Now, designing of attachment will be affected also by this early selection of the pin and the result (attachment) will be "relatively" poorer quality (which you may call optimum design) since your design travels around Grade2 use. We are saying same thing up to now. But, the problem starts here; the tolerance in the design. This farming field applications (unlike other industries) require larger tolerances in the designs because farmers are using their implements in very different conditions. I agree in that it's in their responsibility of farmers using them in not-mentioned conditions of farmers. But changing an implement just for a shear pin isn't reasonable and isn't practical. So, this problem of selecting the shear pin in real application requires a solution, at least in my opinion based on farmers' complaints here.
</font><font color="blue" class="small">( As far as the rest goes:
Aluminum is a pretty poor choice for a test material as it reacts significantly different than ferrous materials. )</font>
As I said before, I'm not good at material science details. Aluminum may not be a good selection as its characteristics is different than ferrous materials like the steel. But I still think there must probably be some sufficient analogy between the deformations of aluminum and steel. I think a rough/approximate mathematical model using some symmetries can be made for the deformation path of aluminum and steel under the same forces. and modelling deformation parts of them only will be sufficient. Anyways, this needs further study, but who cares about farmers' shear pin?, except Nomad;-).
Villengineer
Gold Member
</font><font color="blue" class="small">( I think we are confused (in communication) here in the steps of design.? )</font>
No confusion on my part. I said you start with a set of parameters. Since they are widely accepted, cheap, and readily available it's entirely possible that the use of Gr2 shear pin could be one of those parameters.
</font><font color="blue" class="small">( Now, designing of attachment will be affected also by this early selection of the pin and the result (attachment) will be "relatively" poorer quality (which you may call optimum design) since your design travels around Grade2 use )</font>
There is nothing about Gr2 that makes it "poorer quality" than any other grade bolt. Quality is how it's made, not what it's made of. I have seen plenty of poor quality Gr8 bolts. Like I said before you start out with an objective and if it can be accomplished with the use of all basic components and materials, why complicate things?
</font><font color="blue" class="small">( We are saying same thing up to now. But, the problem starts here; the tolerance in the design. This farming field applications (unlike other industries) require larger tolerances in the designs because farmers are using their implements in very different conditions. )</font>
What are you talking about? The industry I work in varies MORE than farming in how various customers use our products. Farmers just happen to be a very small slice of our customer base. We design to the specifications set before us, if you want it right on the edge we'll do it, if you want it built like a tank, we can help you out there, too. The very same product might be used by a farmer, in the auto industry, and by a lumber yard. We tell them what it can do and stand behind it.
</font><font color="blue" class="small">( But changing an implement just for a shear pin isn't reasonable and isn't practical. So, this problem of selecting the shear pin in real application requires a solution, at least in my opinion based on farmers' complaints here )</font>
Designs are changed for a single component all the time. Especially if our customers find it unsatisfactory. At the same time, if we find that the customer has unrealistic expectations, we may decide not to change anything. If you keep breaking shear pins there are a number of possible reasons and none of them may have anything to do with the shear pin itself.
No confusion on my part. I said you start with a set of parameters. Since they are widely accepted, cheap, and readily available it's entirely possible that the use of Gr2 shear pin could be one of those parameters.
</font><font color="blue" class="small">( Now, designing of attachment will be affected also by this early selection of the pin and the result (attachment) will be "relatively" poorer quality (which you may call optimum design) since your design travels around Grade2 use )</font>
There is nothing about Gr2 that makes it "poorer quality" than any other grade bolt. Quality is how it's made, not what it's made of. I have seen plenty of poor quality Gr8 bolts. Like I said before you start out with an objective and if it can be accomplished with the use of all basic components and materials, why complicate things?
</font><font color="blue" class="small">( We are saying same thing up to now. But, the problem starts here; the tolerance in the design. This farming field applications (unlike other industries) require larger tolerances in the designs because farmers are using their implements in very different conditions. )</font>
What are you talking about? The industry I work in varies MORE than farming in how various customers use our products. Farmers just happen to be a very small slice of our customer base. We design to the specifications set before us, if you want it right on the edge we'll do it, if you want it built like a tank, we can help you out there, too. The very same product might be used by a farmer, in the auto industry, and by a lumber yard. We tell them what it can do and stand behind it.
</font><font color="blue" class="small">( But changing an implement just for a shear pin isn't reasonable and isn't practical. So, this problem of selecting the shear pin in real application requires a solution, at least in my opinion based on farmers' complaints here )</font>
Designs are changed for a single component all the time. Especially if our customers find it unsatisfactory. At the same time, if we find that the customer has unrealistic expectations, we may decide not to change anything. If you keep breaking shear pins there are a number of possible reasons and none of them may have anything to do with the shear pin itself.
Ok, I'm lost in this communication. I meant by "relatively poor quality" anything from material, size, how it's made because I was trying to use a kind of language that everybody could understand.
Anyways, we can summarize the REAL stiuation as
Farmers are frequently breaking many shear pins if theirs are Grade2 and they are affraid of using higher grade pins like Grade5 or Grade8.
Correct? I think we all agree in that summary (doesn't matter whoever doing the mistake. this is reality) I had a solution in my mind and it was modelling the deformation behaviours by a real field test by using aluminum. Yes, such a model can be made. because generalized equations of stress-strain is same for both of the steel and aluminum. During the elastic deformation, from mathematican's point of view, these equations can be considered linear and nonlinear during the plastic deformation. But the nonlinearity in this plastic deformation isn't so high. Nonlinearity is very high only during the fracture moment. But since we are modelling only deformations small nonlinearity during the deformations will certainly not be a problem for a mathematican. As I said above, their forms of generalized equations are same. The only difference for steel and aluminum equations is the specific constants (or functions of their material properties.) These functions related to material properties can be nonlinear, but with some symmetries, this nonlinear functions can be reduced to lower dimensions unless it's at fracture period. While even fractures which are highly nonlinear are already being modelled, modelling simple deformations certainly won't be difficult. Certainly there must be some symmetry groups which can be applied to specific material functions of aluminum and steel. These symmetry groups will simplify big equations with material emphirical functions. So, as a conclusion, a certain aluminum specimen can be produced for farmers so that they can fix their steel shear pin type and size for their special applications. If the specific deformation functions of steel and aluminum are given to me (any material science professor there;-), I can contribute by writing a small software for aluminum specimen. (its cost? will not be higher than a baler cost;-)
Finally, I'd like to repeat the summary:
Farmers are frequently breaking many shear pins and therefore, they are angry if theirs are Grade2 and they are affraid of using higher grade pins like Grade5 or Grade8.
Anyways, we can summarize the REAL stiuation as
Farmers are frequently breaking many shear pins if theirs are Grade2 and they are affraid of using higher grade pins like Grade5 or Grade8.
Correct? I think we all agree in that summary (doesn't matter whoever doing the mistake. this is reality) I had a solution in my mind and it was modelling the deformation behaviours by a real field test by using aluminum. Yes, such a model can be made. because generalized equations of stress-strain is same for both of the steel and aluminum. During the elastic deformation, from mathematican's point of view, these equations can be considered linear and nonlinear during the plastic deformation. But the nonlinearity in this plastic deformation isn't so high. Nonlinearity is very high only during the fracture moment. But since we are modelling only deformations small nonlinearity during the deformations will certainly not be a problem for a mathematican. As I said above, their forms of generalized equations are same. The only difference for steel and aluminum equations is the specific constants (or functions of their material properties.) These functions related to material properties can be nonlinear, but with some symmetries, this nonlinear functions can be reduced to lower dimensions unless it's at fracture period. While even fractures which are highly nonlinear are already being modelled, modelling simple deformations certainly won't be difficult. Certainly there must be some symmetry groups which can be applied to specific material functions of aluminum and steel. These symmetry groups will simplify big equations with material emphirical functions. So, as a conclusion, a certain aluminum specimen can be produced for farmers so that they can fix their steel shear pin type and size for their special applications. If the specific deformation functions of steel and aluminum are given to me (any material science professor there;-), I can contribute by writing a small software for aluminum specimen. (its cost? will not be higher than a baler cost;-)
Finally, I'd like to repeat the summary:
Farmers are frequently breaking many shear pins and therefore, they are angry if theirs are Grade2 and they are affraid of using higher grade pins like Grade5 or Grade8.
Egon
Epic Contributor
Nomad; have you considered designing a viscous coupling with lock up capability that is torque sensitive for release capabilities.
That would sure eliminate a lot of time spent changing shear bolts.
Egon
That would sure eliminate a lot of time spent changing shear bolts.
Egon
Egon, viscous coupling is a good idea as it will also absorb/damp the shock which is the main reason in breaking the shear bolt. But the price is a restriction here and we are talking about farmers using the shear pin only. A very simple viscous coupling (which will cost very cheap) possible? Worth to think about it.
Egon
Epic Contributor
Time is worth money when the farmer is working. This is really true at planting or harvest time. The less time he's fixing stuff the more time he has to do all the good stuff.
Why not move technology ahead and forget those simple shear pins?
Egon
Why not move technology ahead and forget those simple shear pins?
Egon
Villengineer
Gold Member
</font><font color="blue" class="small">( Farmers are frequently breaking many shear pins if theirs are Grade2 and they are affraid of using higher grade pins like Grade5 or Grade8 )</font>
As they should be. If the attachment was designed to use a Gr2 shear pin then they should use a Gr2 shear pin. To suggest that they should do otherwise is irresponsible. Even if you don't get them hurt or killed, chances are you will cause them even more agravation when they start breaking major parts of their attachments.
If they are so put out by having to replace shear pins, then buy attachments with slip clutches. I can't believe that a vicous coupling would be that much cheaper than the clutch systems already available.
Your whole test specimen thing doesn't make practicle sense to me. Are you suggesting that each farmer be given an aluminum shear pin for each attachment to put into use and then have them analyzed to find the best alloy of steel for them to use for each application? 1) The mechanical properties of common aluminums (the only ones that make economical sense) are so much lower than steel that you couldn't get an accurate reading. They would shear way before the loads required to shear any steel, thus telling you absolutely nothing 2) I don't know about Turkey, but here in the US it would be cheaper to install slip clutches on each implement than to go through this process. After all what's the cost difference between them, a couple hundred bucks? You couldn't get a qualified materials test lab to look at them for that kind of money.
As they should be. If the attachment was designed to use a Gr2 shear pin then they should use a Gr2 shear pin. To suggest that they should do otherwise is irresponsible. Even if you don't get them hurt or killed, chances are you will cause them even more agravation when they start breaking major parts of their attachments.
If they are so put out by having to replace shear pins, then buy attachments with slip clutches. I can't believe that a vicous coupling would be that much cheaper than the clutch systems already available.
Your whole test specimen thing doesn't make practicle sense to me. Are you suggesting that each farmer be given an aluminum shear pin for each attachment to put into use and then have them analyzed to find the best alloy of steel for them to use for each application? 1) The mechanical properties of common aluminums (the only ones that make economical sense) are so much lower than steel that you couldn't get an accurate reading. They would shear way before the loads required to shear any steel, thus telling you absolutely nothing 2) I don't know about Turkey, but here in the US it would be cheaper to install slip clutches on each implement than to go through this process. After all what's the cost difference between them, a couple hundred bucks? You couldn't get a qualified materials test lab to look at them for that kind of money.
</font><font color="blue" class="small">( If the attachment was designed to use a Gr2 shear pin then they should use a Gr2 shear pin.
)</font>
This is an approach of "sell and forget the rest" (joke.)
You are correct. But whatever happening, they are breaking Gr2 much and this is causing them make angry and waste time. Okay, they should follow the user manuals, but the manuals will not be able to tell them exactly what exact field conditions are designed for that certain implement and also, the conditions of their PTO, engine, etc of tractors will not be (cannot be) considered much. So, they should do somethings else. But, what to? What I am trying to do here is a try to suggesting a solution. Here, our opinions differ.
</font><font color="blue" class="small">( I can't believe that a vicous coupling would be that much cheaper than the clutch systems already available.
)</font>
Agree (although didn't think if possible to make a cheap viscous coupling or not)
</font><font color="blue" class="small">(
Your whole test specimen thing doesn't make practicle sense to me. Are you suggesting that each farmer be given an aluminum shear pin for each attachment to put into use and then have them analyzed to find the best alloy of steel for them to use for each application?
)</font>
Yes, one test specimen (within the package of implement) will be enough. Once farmer determines his/her steel shear pin type for his/her special conditions he will not need that test specimen anymore.
</font><font color="blue" class="small">(
1) The mechanical properties of common aluminums (the only ones that make economical sense) are so much lower than steel that you couldn't get an accurate reading. They would shear way before the loads required to shear any steel, thus telling you absolutely nothing
)</font>
Their magnitudes of their parameters like load capability, etc aren't important in a modelling (as you know.) Even their equations of material functions can be different for aluminum and steel. Whats important is the "form" of their "specific material" functions which are usually linear at low deformations. If their forms and nonlinearities are somewhat close to each other, symmetries can easily be found in their behaviours. Thus, this will absolutely tell me somethings about the shear deformation behaviours of aluminum test pin model and prototype steel pin. "Generalized form" of stress-stress flow relation is same for both of them anyways. So, such an aluminum test specimen is "probably" possible.
</font><font color="blue" class="small">(
2) I don't know about Turkey, but here in the US it would be cheaper to install slip clutches on each implement than to go through this process. After all what's the cost difference between them, a couple hundred bucks? You couldn't get a qualified materials test lab to look at them for that kind of money. )</font>
Here the cost difference between them is cheaper. So, shear pin clutch is almost unavailable here. Even if there is $100 difference, I think it's still worth to use the slip clutch economically if we consider time=money. (a real cost analyse will probably prove that.) But there are people everywhere who are hard to change their habits. I guess thats why they are still preferring to use the shear pins.
)</font>
This is an approach of "sell and forget the rest" (joke.)
You are correct. But whatever happening, they are breaking Gr2 much and this is causing them make angry and waste time. Okay, they should follow the user manuals, but the manuals will not be able to tell them exactly what exact field conditions are designed for that certain implement and also, the conditions of their PTO, engine, etc of tractors will not be (cannot be) considered much. So, they should do somethings else. But, what to? What I am trying to do here is a try to suggesting a solution. Here, our opinions differ.
</font><font color="blue" class="small">( I can't believe that a vicous coupling would be that much cheaper than the clutch systems already available.
)</font>
Agree (although didn't think if possible to make a cheap viscous coupling or not)
</font><font color="blue" class="small">(
Your whole test specimen thing doesn't make practicle sense to me. Are you suggesting that each farmer be given an aluminum shear pin for each attachment to put into use and then have them analyzed to find the best alloy of steel for them to use for each application?
)</font>
Yes, one test specimen (within the package of implement) will be enough. Once farmer determines his/her steel shear pin type for his/her special conditions he will not need that test specimen anymore.
</font><font color="blue" class="small">(
1) The mechanical properties of common aluminums (the only ones that make economical sense) are so much lower than steel that you couldn't get an accurate reading. They would shear way before the loads required to shear any steel, thus telling you absolutely nothing
)</font>
Their magnitudes of their parameters like load capability, etc aren't important in a modelling (as you know.) Even their equations of material functions can be different for aluminum and steel. Whats important is the "form" of their "specific material" functions which are usually linear at low deformations. If their forms and nonlinearities are somewhat close to each other, symmetries can easily be found in their behaviours. Thus, this will absolutely tell me somethings about the shear deformation behaviours of aluminum test pin model and prototype steel pin. "Generalized form" of stress-stress flow relation is same for both of them anyways. So, such an aluminum test specimen is "probably" possible.
</font><font color="blue" class="small">(
2) I don't know about Turkey, but here in the US it would be cheaper to install slip clutches on each implement than to go through this process. After all what's the cost difference between them, a couple hundred bucks? You couldn't get a qualified materials test lab to look at them for that kind of money. )</font>
Here the cost difference between them is cheaper. So, shear pin clutch is almost unavailable here. Even if there is $100 difference, I think it's still worth to use the slip clutch economically if we consider time=money. (a real cost analyse will probably prove that.) But there are people everywhere who are hard to change their habits. I guess thats why they are still preferring to use the shear pins.
rambler
Veteran Member
- Joined
- Jul 6, 2003
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- Ford 960, 7700, TW20, 1720; IHC H, 300; Ollie S77
First I gotta say - you folks have some of the best inside jokes in this thread I've ever seen. good job all! /forums/images/graemlins/smile.gif Totally enjoyed them! /forums/images/graemlins/smile.gif And yes you know who you are....
Ok, the aluminimn thing is pointless. If you want to test a pin, test the type of pin that will actually be used.
In my farming career, most farmers drilled out the holes 1/16" and use a slightly larger bolt of the same grade as the previous shear pin. We don't like to change the pin type, but slightly increase the size.
I feel nomad is trying to chang the material (aluminumn) and the diameter (using a gr 8 bolt & grinding a nick in it) and making this terribly confusing & immpossible. Somewhere in there he has a point, that each machine has it's own breaking point slightly different than another machine; but you can't try to find that by starting with a gr 8 bolt & making it skinnier - you MUST start with a gr 2 bolt, and either increase the grade or increase the bolt size. You also cannot easily create the same 'nick' in every gr 8 bolt a farmer makes by himself, so the whole exersize is pointless in the real world as nomad preposes it.
Also, this whole discussion is about changing the bolt grades, and that is not how I'm familiar with this. You increas the size of the hole & bolt slightly; and leave the grade of the bolt the same.
I remember a discussion somewhere here about a company that makes post hole diggers, a regular duty one & a lighter duty one. all components are the same, but the gearbox & pto shaft are lighter on the lighter duty unit. It has a shear pin with one side thicker than the other side, because a thin bolt was too weak, and a thick bolt was too strong - so they used holes in the pipe shaft of 2 dofferent sizes, and a special shear pin of 2 sizes that cost $9.
In the thread they figured out that for the price of 30 shear pins, you could have bought the heavy duty post hole digger & had a better machine.
I think most people drill those holes out to the bigger size & go dig holes......
I'm sure nomad will somehow like this story & think I am agreeing with him, but i'm actually disagreeing with much of what he has said in this thread.
If I were to fine tune my shear pin, I would start with gr 2 bolts, & redrill the holes slightly bigger and use a bigger bolt if the first size sheared too many & I felt my tractor could handle a bigger load & I was not concerned about the warrenty on the machine. However, such 'fine tuning' can cost you a whole lot if you are not careful, & i am not saying I recommend it.
As to slip clutches, they are a problem. For the most part they are much better than a shear pin, but if a slip clutch 'fails' it does not work, and this will destroy your implement or your tractor 50% of the time. So the slip clutch costs more, does a better job, but it is not fail-safe. A shear pin that is defective will break too soon, and only destroy itself. So, which is better, a shear pin or a slip clutch? hum.
--->Paul
Ok, the aluminimn thing is pointless. If you want to test a pin, test the type of pin that will actually be used.
In my farming career, most farmers drilled out the holes 1/16" and use a slightly larger bolt of the same grade as the previous shear pin. We don't like to change the pin type, but slightly increase the size.
I feel nomad is trying to chang the material (aluminumn) and the diameter (using a gr 8 bolt & grinding a nick in it) and making this terribly confusing & immpossible. Somewhere in there he has a point, that each machine has it's own breaking point slightly different than another machine; but you can't try to find that by starting with a gr 8 bolt & making it skinnier - you MUST start with a gr 2 bolt, and either increase the grade or increase the bolt size. You also cannot easily create the same 'nick' in every gr 8 bolt a farmer makes by himself, so the whole exersize is pointless in the real world as nomad preposes it.
Also, this whole discussion is about changing the bolt grades, and that is not how I'm familiar with this. You increas the size of the hole & bolt slightly; and leave the grade of the bolt the same.
I remember a discussion somewhere here about a company that makes post hole diggers, a regular duty one & a lighter duty one. all components are the same, but the gearbox & pto shaft are lighter on the lighter duty unit. It has a shear pin with one side thicker than the other side, because a thin bolt was too weak, and a thick bolt was too strong - so they used holes in the pipe shaft of 2 dofferent sizes, and a special shear pin of 2 sizes that cost $9.
In the thread they figured out that for the price of 30 shear pins, you could have bought the heavy duty post hole digger & had a better machine.
I think most people drill those holes out to the bigger size & go dig holes......
I'm sure nomad will somehow like this story & think I am agreeing with him, but i'm actually disagreeing with much of what he has said in this thread.
If I were to fine tune my shear pin, I would start with gr 2 bolts, & redrill the holes slightly bigger and use a bigger bolt if the first size sheared too many & I felt my tractor could handle a bigger load & I was not concerned about the warrenty on the machine. However, such 'fine tuning' can cost you a whole lot if you are not careful, & i am not saying I recommend it.
As to slip clutches, they are a problem. For the most part they are much better than a shear pin, but if a slip clutch 'fails' it does not work, and this will destroy your implement or your tractor 50% of the time. So the slip clutch costs more, does a better job, but it is not fail-safe. A shear pin that is defective will break too soon, and only destroy itself. So, which is better, a shear pin or a slip clutch? hum.
--->Paul