Another fencing question.

[Jogeephus]

Is there any difference between the torque or pressure on the center post of a typical three post corner when the inside angle is around 130 degrees versus the pressure on the same post setup on a 90 degree corner? Seems like everytime I have to jog a fence on a wide angle the center post wants to pull in some. Seems like I remember something about vector forces in physics but that was a long time ago and everyone was so busy celebrating the invention of the wheel for me to remember too much. But then again, it could just be sloppy craftmanship and a sign that I need to outsource this type work! :lol: Thanks in advance.

 

[Wewild]

Is there any difference between the torque or pressure on the center post of a typical three post corner when the inside angle is around 130 degrees versus the pressure on the same post setup on a 90 degree corner? Seems like everytime I have to jog a fence on a wide angle the center post wants to pull in some. Seems like I remember something about vector forces in physics but that was a long time ago and everyone was so busy celebrating the invention of the wheel for me to remember too much. But then again, it could just be sloppy craftmanship and a sign that I need to outsource this type work! :lol: Thanks in advance.

130 should be better but not much so as long as the outer braces are anchored to the middle brace from the top to the bottom. The center brace should be there for the support of the outer braces which transmitts through the wire to its base. The wire is the key as I see corner braces done backwards all the time.

 

[backhoeboogie]

Do you remember X, Y, and Z forces?

At 90 degrees, half the force is loaded on that corner in the X direction and the other half is loaded in the Y direction.

When you have 150 degrees, only 30 degrees is loaded in the Y direction. So you will get more lifiting effect in the Z direction, from the X driection load. Simple torque.

I am not a structural engineer, so that is about the best I can do.

Put in a deadman if you can live with it hanging out from the fence row and the torque goes away.

 

[Wewild]

Do you remember X, Y, and Z forces?

At 90 degrees, half the force is loaded on that corner in the X direction and the other half is loaded in the Y direction.

When you have 150 degrees, only 30 degrees is loaded in the Y direction. So you will get more lifiting effect in the Z direction, from the X driection load. Simple torque.

I am not a structural engineer, so that is about the best I can do.

Put in a deadman if you can live with it hanging out from the fence row and the torque goes away.

No. The torque is at it's highest at 90 and decreases all the way up to 180. 180 would represent a straight line with no torque. You have to assume that they put the braces in line with the fence.

 

[backhoeboogie]

No. The torque is at it's highest at 90

In the Y direction, you are correct.

 

[Jogeephus]

The posts are in line with the fence. I've noticed this on three seperate corners on two different places and it puzzles me. All corners are set in concrete, all are braced with wire and posts in same manner none have moved except when the angle gets this wide which leads me to believe something else is going on that I'm not compensating for.

I assume a Deadman would be a fourth anchor outside the fence pulling away from the lean. Lean is about an inch, but I'm afraid if the forces continue without some correction, it will continue to lean inward and loosen the fence over time. On the surface, it seems like each piece would have its own pull. If I had set up a double H corner I know there would be no lean so force Z must be having a larger affect on it than I can visualize. Sorry, I'm still just confused and thinking out loud with know real understanding.

 

[backhoeboogie]

I'd put the deadman in the inside of the lean if I could. 45 degrees down ward from the top of the post. The problem is of course, mowing along the fence and such. A deadman can be a pain.

 

[Wewild]

The posts are in line with the fence. I've noticed this on three seperate corners on two different places and it puzzles me. All corners are set in concrete, all are braced with wire and posts in same manner none have moved except when the angle gets this wide which leads me to believe something else is going on that I'm not compensating for.

I assume a Deadman would be a fourth anchor outside the fence pulling away from the lean. Lean is about an inch, but I'm afraid if the forces continue without some correction, it will continue to lean inward and loosen the fence over time. On the surface, it seems like each piece would have its own pull. If I had set up a double H corner I know there would be no lean so force Z must be having a larger affect on it than I can visualize. Sorry, I'm still just confused and thinking out loud with know real understanding.

Where is the bracing wire locate from the groud on the center post? And the same for the outer posts? Questimates will do.

 

[Jogeephus]

They are parallel. Have a post at 3 feet then wire parallel to this a foot above.

 

[Wewild]

No. The torque is at it's highest at 90

In the Y direction, you are correct.

I got the Z as it is almost alway verticle. X and Y are the lines. It seems your talking of forces in the Z plane. Torque would be about the Z axis. There really wouldn't be torque if the fence was built properly. Each of the X and Y forces would cancel out the rotation.

 

[Jogeephus]

Another thing I noticed was that neither of the outer two posts have moved at all, so what could this mean?

 

[Wewild]

They are parallel. Have a post at 3 feet then wire parallel to this a foot above.

You got a verticle corner post and two other posts and a wood post on each side that is parrallel to the earth that spans the distance between the sole post and the outer poles about 4.5' off the ground. You shoud have some wire runninig from the outer 2 to the sole middle one. Does that wire start at the bottom of the sole middle post and go up to the top of the outer 2?

 

[Jogeephus]

No its paralell.

 

[backhoeboogie]

deleted Check you pm.

 

[Wewild]

Check PM.

 

[Jogeephus]

Ok

 

[backhoeboogie]

No. The torque is at it's highest at 90

In the Y direction, you are correct.

I got the Z as it is almost alway verticle. X and Y are the lines. It seems your talking of forces in the Z plane. Torque would be about the Z axis. There really wouldn't be torque if the fence was built properly. Each of the X and Y forces would cancel out the rotation.

X and y are in different directions and cannot cancel each other. I think you are talking a negative Y and a positive Y force cancelling one another.

Say you have a corner post designed to load in the north direction and west direction. A perfect 90. It is designed for a north load and west load.

What he has is a post designed to load in the east direction, but slightly north although north is not in the design, and the west direction, but a little north too, but north is not in the design for it either. You are relying on depth to overcome the torque. It is not designed for torque.

Don't know how to actually explain it but I can have a civil engineer attempt

 

[backhoeboogie]

The deadman is to overcome the north force that is not included in the post design load.

 

[Wewild]

What he has is a post designed to load in the east direction, but slightly north although north is not in the design, and the west direction, but a little north too, but north is not in the design for it either. You are relying on depth to overcome the torque. It is not designed for torque.

Don't know how to actually explain it but I can have a civil engineer attempt

Thanks but I am purty good at this as my Grandfather taught me the right way before I got my ME degree. It became more clear after having done it and then seeing it in school.

We must be talking on different planes.

You are talking about the post lifting when you talk about depth. You just got to make sure that don't happen. We don't seem to have that problem. Is that torque. Well ...yes it is but it is not that big of a problem. Most folks think it is suppose to support the wire. It's not. It's suppose to support the outer post. Ours just don't seem to lift.

 

[backhoeboogie]

Thanks but I am purty good at this as my Grandfather taught me the right way before I got my ME degree.

Well then. Seems it should be plain as day. H brace to the east H brace to the west, but north forces are applied to it. Torque comes from the cantilever force on the center post.