How to stiffen my pole?

[Nimonic]

So I fabricated this wrought iron and cedar picket gate. First gate I've done. Only potential issue I have is that I used 4x4" 0.120" wall square tubing as support posts. Approx 11 ft long, with 3-4 feet in the ground. The hinged side seems to flex more than I expected and I've really had to max out the hinge adjustment to keep it from drooping too much. The 3-4 feet in the ground is reinforced with ~4, 80lb backs of concrete. The ground is not giving way. The pole flexes. That I am sure of.

Anyway, started thinking about how to minimize the deflection of the hinged post. Maybe fill with concrete and then stick 3-4 tubes of 1.5" 0.120 wall round tubing inside there? It would be sort of a composite at that point.

Stupid idea?

Thoughts?

 

[VocaTexas]

Trying to keep it serious here....

I assume you have nowhere to put a 'deadman'? That's the way you brace ranch fencing and gates around here. One thing I have done using 2 3/8 and 2 7/8 pipe (too late for you now) where I couldn't use a deadman was to put a smaller pipe inside the larger one and weld the ends together. Makes a very stiff pole.

 

[Zeke]

Trying to keep it serious here....

I assume you have nowhere to put a 'deadman'? That's the way you brace ranch fencing and gates around here. One thing I have done using 2 3/8 and 2 7/8 pipe (too late for you now) where I couldn't use a deadman was to put a smaller pipe inside the larger one and weld the ends together. Makes a very stiff pole.

He could still slip another pipe into the post and weld the top and as close to the base as possible with a plug weld. If the post was pulled back some before the welding it might settle in plumb. To stiffen the part below grade he could pour epoxy down inside and hope it would float up along side and in between the inner and outer posts.

 

[larry_g]

Another option is to extend the post up and brace between the tops of the posts. You commonly see this in a ranch gate with the name of the ranch in the brace or hanging from it. You could mirror your scroll work on the top of the gate into the cross brace.

A second option would be to cut the gate in half so the hinge posts see a lot less load.

lg
no neat sig line

 

[Tarheelgarage]

you have a deadman; no amount of stiffener will help

 

[Nimonic]

Originally planned a double gate, but the driveway slope would have made it look like ****. Deadman would definitely help, but I plan to hang a personnel gate on the other side of that pole as I extend it to the corner of the house. I may consider a deadman in between the two gates (vehicle gate and personnel gate). :

 

[Hobbit]

You can weld another piece of steel to the back of the post to stiffen it up but the post is likely flexing at the very bottom when exiting the foundation its in. If this is the case filling with concrete wont work either the new concrete wont bond with the old inside the post which is right where the flexing is likely occurring. Looks like you need to pull up you pole and insert a thicker walled substitute. A wheel on the unhinged end that is taking the load at full closure might prevent the flex.

 

[jwhcars]

I hear ****** works ......

 

[readhead]

If the existing post has concrete inside up to grade then your only choice, short of replacing the post, is to tie back the top of the post to something. Oops, I just looked at the photo again and it looks like the gate posts are stand alone pieces.
If there is no concrete in the post then slipping another pipe into the existing one and plug welding would be your best bet.
All the bending moment is at grade so anything you can get below grade will help the most.
As much as you don't want to hear it I would suggest cutting the gate in half and swing off each post. We build a lot of gates and the first thing we do is all the calcs for the posts and operators. Quite often we have to lighten up the gate to get the whole system to work. By the way that is a good looking gate.

 

[zkling]

Do you have room for an H brace on the back side behind your fence?

 

[Jack Olsen]

Is the inside of the post accessible and unobstructed? If so, inserting another piece into it will -- as others have said -- do a lot to stiffen it up. Even if you can't weld it at the bottom, you can do so at the top, and even drill into a section lower down and then weld it back up.

With my front yard fence, I hadn't anticipated how it could sway like a sail if a kid were to stand in the middle and push and pull while looking out at the street. I wasn't core drilling into the wall, so there was a weakness at the 'ankles' of this long section.

I happened to have some stock on hand with a pinched square profile that slid right into my 16 gauge stock. It worked very well and was easy to do.

 

[xyster101]

That gate is awesome! Post more pictures, the other side too. What do you think it weighs? That is a lot of leverage against that one post.

I like the idea of linking both posts together with your name or scroll work mixed into the cross piece. More money, more time.
Could you do a dead man made from the same steel tubing, but weld it half way up to the post opposite the gate at a 45 angle and cement that into the ground 4'?

 

[Leaflessshadetree]

What about putting a caster wheel on the latch end?

 

[KELLHAMMER]

I suspect you will be able to stiffen the vertical upright post the hinges are mounted to. But , over time the whole thing will start to droop because of the way the post is planted in the ground. It lacks the resistance to wanting to turn over. Think of it like a beam sticking out of a wall, commonly referred to as a canteliver. If the portion of the beam sticking into the wall is not sercured properly or doesn't extend far enough into the wall, or the structure is to weak to mount to, the cantelivering portion will droop regardless of how stiff the beam is. The longer the canteliver the greater the force acting on the fixed end. In this case, the taller the post will require a more secure base. I remember installing a 8' dia. satellite dish for my dad. It was a 6" dia by 5 foot tall round steel post that mounted to the top of a concrete footing which was below grade with three anchor bolts embedded 18" into the footing. The footing was four feet by four feet and four feet deep That's 2.4 cubic yards of concrete. That 196 -80lb bags of sakrete. The design was mainly for the dish to resist the wind blowing on it from any direction. The weight of dish itself was incredibly light.

 

[ez-duzit]

...put a 'deadman'...

This is how you fix it.

 

[InPrimer]

a caster wheel is probably the easiest solution, I put one on a lean to shed hinged on one side that covered a water meter and other equipt, not the same, but it relieved the stress on the pole side

 

[ez-duzit]

A wheel won't help on that sloping driveway.

 

[mtmgtz]

I hear ****** works ......

Only for 4 hours. He needs a permanent stiff pole...

 

[woodrail]

Install 2 additional poles 16" away from the original hinge pole in a triangle pattern. Tie them all together with some ornamental iron.

This will effectively create a truss that should offer substantially more support.

 

[Pluribus]

Not going to touch this one, but I'll throw out a couple of ideas...from a safe distance, of course. Are you sure it's post deflection? Did you put a straightedge on the post to confirm? My suspicion is that on something like this, the entire base in the ground is moving. With a gate (lever) that long, there's a tremendous amount of force on the post and its base. Very little movement in the post/base will result in a fair bit of sag at the far end of the gate. 4" x 4" x .120 is some stout stuff. If it's not the base in the ground moving, it will likely be someday.

That said, if you're sure it's the post itself bending and not the base in the ground moving, could you weld a fin on the back side of the post with the hinge on it? Feasibility depends on how deep into the ground you can get access. I'm picturing a triangle tapering from about 3" at the top of the post to about a 12" as far deep into the ground as you can get access. I'm throwing out #'s as a non-engineer, but I do know a fin like that can add tremendous strength.

Different application, but here's a link that should represent the concept:
http://www.flickr.com/photos/38021715@N00/5561505616/

I know you want access for a man gate to the side, so a conventional deadman wouldn't work. With your fabrication skills, why not build a trellis/pergola type thing that has space for a gate, plus serves as a deadman. I'm sure there's a way to triangulate and brace something like that with an opening for access.

 

[Nimonic]

I know you want access for a man gate to the side, so a conventional deadman wouldn't work. With your fabrication skills, why not build a trellis/pergola type thing that has space for a gate, plus serves as a deadman. I'm sure there's a way to triangulate and brace something like that with an opening for access.

This may be the thing to do. It will address the pole stiffness and the moment on the foundation.

Thanks to all for the comments, including the dirty ones.

 

[p_mori7]

The 3-4 feet in the ground is reinforced with ~4, 80lb backs of concrete. The ground is not giving way. The pole flexes. That I am sure of.

How much does that gate weigh ? Just looking at it, it appears to weigh at least 300 pounds, almost equal to your concrete base. Because it's Center of Gravity is way off from the CG of the post & base, you need a much heavier base to keep it from drooping in my opinion.

 

[gahrajmahal]

I think I would try a ramp on the fixed end. A small caster hidden in the tubing on the gate would make it slide easily up the ramp. It would then be a secure rest for the loose end of the gate to rest on. You could easily try this out by clamping the ramp to the post and it wouldn't be too obvious. If my idea is confusing I will make a sketch for you.

 

[theoldwizard1]

First, that is a very nice gate !

a caster wheel is probably the easiest solution ...

A wheel won't help on that sloping driveway.

The caster will work fine because the caster end of the gate is at the high side of the driveway when the gate is closed. You will need a spacer block for the caster to sit on when it is open.

The downside of a caster is that if there is a lot of upward force on the gate it will try to twist the gate. You would need 2 latch, one high and one low to prevent this.

Anything you put inside the post nowwill have limited affect because it is not tied through to the lump of concrete your 4x4 is sitting in. The real answer is, yank the 4x4 and replace it with a 6x6, .250 wall. It will bend, just not as much especially if you fill it with concrete and rebar when you install it.

 

[Diesel_D]

They make spring loaded casters for gates in smaller sizes

 

[1956 F100]

I have a buddy who filled his with concrete. Made it considerably more rigid.

 

[JakeKohl]

That is a very nice looking gate! I had a similar project but I used schedule 40 4" steel pipe for my posts. I filled them with concrete during installation just as an extra measure and they've held up great for a couple of years. I don't get any measurable flex. My gates look to be a little less long and weighty than yours, however - these are about 7.5' long each but I did take some measures to keep the steel light to keep the weight down.

I do agree with taking the weight off of your post and filling it with concrete. From an engineering perspective, you are not asking the concrete to carry bending loads. Instead, the concrete in this application will act as a core material and transfer compression and other odd loads between the opposite sides (skins) of the post. The concrete will eliminate a good deal of localized flexing by transferring that inward buckle (very small) to the opposite skin sharing the small localized high loads of the tubing skin with areas of the tubing that is not loaded...in short, it will make your poll a lot stiffer. It doesn't really matter much if it doesn't makes a chemical bond with the concrete that is already in the bottom of the post. I would not, however, recommend adding the steel tubing internally with the concrete. While it probably won't hurt anything, if it's not connected to the post along it's length, it won't add any structure and will probably keep the concrete from filling the void adequately.

A shallow truss added to the outside of the post opposite of the normal hanging weight will also help if the concrete doesn't provide the desired result (or if you just want to make it a sure fire solution). You could do this in a truss with a 1/8" steel strap and a king post in the middle...make sure the lower end of the strapping goes below ground level. and I would put the king post within 12" of the ground. The other end of the strap can go all the way to the top of the post if you wish. A 3" king post would probably be adequate - 6" would certainly do the trick. The truss is a little hard to describe, let me know if a sketch will help with my crappy explanation.


DSC_2616 by Green Room Graphics, on Flickr

 

[velocipede]

@Jake Kohl,
That's a beautiful fence. It appears to have some curved sections and I was wondering if the horizontal members were laminated or steam bent or??

 

[Trey T]

There are two methods that everone have been recommending:

1. place another tube inside the pole. For this to work, the tube must be connected (pressed in or slide in and welded at each end) or else it's just a dampener; however, a dampener may just what the OP needs.
2. fill with concrete. This will stiffen without much guessing and less work involved.

I like the second method better.

 

[Joe69]

I hear ****** works ......

That's exactly what I was thinking.

Joe

 

[Brad Beam]

Soak it in cider

 

[willymakeit]

Only for 4 hours. He needs a permanent stiff pole...

Or two popsicle sticks and duct tape. Easily found in a well equipped garage.

 

[Nimonic]

One other fact I forgot to mention. The ground is about 1-1.5 ft top soil and then lime stone below that. So the post and concrete put are set into about ~1.5 ft of top soil and then ~2 ft of lime stone rock. Had to use a jack hammer to get through that part. That's why I think the flex is in the pole.

 

[ez-duzit]

The pole is inadequate for the task.

 

[kerrynzl]

Pole-agra!

Seriously ,use some engine block filler grout. It doesn't shrink when it sets.

 

[JakeKohl]

@Jake Kohl,
That's a beautiful fence. It appears to have some curved sections and I was wondering if the horizontal members were laminated or steam bent or??

It is curved in that section (I hadn't trimmed the last couple of pickets when I took that photo). The curved stringers are made of three layers of 1/2" marine PT plywood. After ripping to size, I soaked the plywood for a couple of days under towels and kept soaking them day and night. I then hammered rebar into the edge of the driveway and clamped the plywood to the rebar so I could build it to match the curve of the drive. I then started screwing the plywood stringers together from both sides and laminated it three pieces thick (1.5" total). I think I used an entire box of decking screws on the two stringers! I left it that way to dry out before moving on to the next steps. It worked pretty well and it retained the shape perfectly. Since installation, they've sagged slightly between the posts - if I was going to do it again, I might double up the posts in the curved section or find a way to reinforce the plywood, or just make the stringers wider (they are currently a little under 4" to optimize the material usage in the sheet)



Fencing on the curve by Green Room Graphics, on Flickr


Fencing on the curve by Green Room Graphics, on Flickr


DSC_2591 by Green Room Graphics, on Flickr


DSC_2612 by Green Room Graphics, on Flickr

 

[velocipede]

Thanks Jake. I didn't even think about laminating plywood. Great idea.

 

[Nimonic]

Jake that looks awesome. Nice work.

 

[Trey T]

nice craftsmanship w/ the curved fence. That's worth every effort for DIY.

 

[kjbenner]

Originally planned a double gate, but the driveway slope would have made it look like ****. Deadman would definitely help, but I plan to hang a personnel gate on the other side of that pole as I extend it to the corner of the house. I may consider a deadman in between the two gates (vehicle gate and personnel gate). :

Would you be hanging the personnel gate off of the pole in question? If it's going to be of similar (heavy) build to the other gate, the extra weight would help straighten things out. It would still flex when you open the gates, but everything should still line up well when you close it.