Dave the Welder crosses a milestone

Frequent readers may recall we have been working on design and construction of front courtyard gates since a front courtyard javelina jade plant attack I'm thinking in February or March. I could research it, but suffice to say we've been working these gates a long time. Now DTW has quite the eye for detail so the process have been VERY VERY VERY well thought out.

All of this has been discussed in one manor or another previously. The Feelings First Folks can just jump to the pictures. For the engineering inclined, here is a recap.

As all things the Quail Manor, there is a lot of detail. 

First was lots of back and forth on how to do these as swinging gates. Which was just not going to work. Latches take-up an inconvenient amount of room. You have to allow space and provide support for the hinge and strike sides. Space is not something in abundance at the Quail Manor. Which led us to sliding gates.

Which led us to how to support these things and keep the structure streamlined. Your musist is by nature a minimalist when it comes to visible structure. Which led to a lot of custom yet unseen rollers for the driveway gate. Which has been complete for quite some time. Works great.

That left us with the other courtyard gate. DTW was the first to realize the patio slab slopes away from the house. Frequent and observant readers will recall that DTW grew up as Dave the Concrete Guy. Learning at the foot of his father who had a big concrete company. Slabs exposed to weather slope about an inch every couple of feet or so to encourage drainage. So no way is this gate going to simply roll on rollers like the driveway one.

Which leaves a cantilever gate. This is going to be a 5 and half ish foot cantilever. And these gates are not made out of balsa wood. So we have to support the gate's weight when closed. Technically we have to support the gate's weight AS it closes. When open it sits and slides on a footing just like the driveway gate. When closing, it hovers up over the slab. 

In theory, I could look up and derive an accurate formula, but the cantilever force that has to be resisted is conceptually the weight of the gate times the length of the cantilever. In our case, a lot times about 5 and a half ish feet. So, a lot times 5. Technically, this force increases as the gate closes. Peaking at about a lot times 5. About 6 inches before it reaches the latch at the house, a floating roller (made of hard rubber so it does not make noise, like I said, DTW has an eye for detail) engages and takes what has heretofore been the ever increasing cantilever weight or force.

The support when open mode is pretty straight forward, we (DTW in his role as Dave the Concrete Guy) just pours another footing with a rail like for the driveway. This footing is poured at the elevation of the patio AT the house. Which makes the floating roller thing work. This was made more complicated because SWITBO has been busy planting stuff. To keep DTW in his role as Dave the Concrete Guy, but more importantly your musist out of trouble, we commissioned SWITBO her own self to move some things. And Dave worked around some more established things. It's now been awhile since the footing was done and I think it worked out.

The real challenge is as the gate closes, the force created by the increasing cantilevered weight of the gate is now pushing UP on the top track. This pushing up has to be resisted by the top track staying right where it is. To make the gate as tall as possible (we're not sure how high a motivated javelina can climb or leap, or if they have a version of a leg-up), the top track is real near the top of a block wall that was not reinforced to take a not insignificant force trying to lift the blocks up off the wall. 

The Civil Engineers among you will know that concrete is swell in compression. The taking weight role of the footing. Sadly, it's not worth a damn in tension. The holding down of the top track role. The cement holding the block wall is basically concrete so we could have a problem.

 The load in our case is the cantilevered weight of the gate and the counterweight is the weight we embed in the back edge of the gate that is always supported and never cantilevered.

The load in our case is the cantilevered weight of the gate and the counterweight is the weight we embed in the back edge of the gate that is always supported and never cantilevered.

So. DTW builds the gate such that we can add weight at the BACK of the gate which always remains supported by the footing and rail. This way, we have uncantilevered weight being pulled down (it's a gravity thing) onto the well understood and proven footing with embedded rail technology. To further excentuate the counterbalance, he extended the top rail of the gate so there is a cantileaver hanging off the back end as well. By doing this counterbalance thing, the upward force is reduced to effectively zero so the top track is really just guiding things along. We added the weight the last time I was down there. The result is you can support the cantilevered gate by pushing down on the back of the gate with one finger and rolls straight and true over the patio to the house wall.

If you look at the pictures you will notice an outlet in the wall. It looks like it might have gotten a wack from a test gate open. Anyway, the outlet limited how far the uncantilevered part of the gate could extend. That's why the top rail is all we could extend.

All in, the gate is 10 and a half feet long. The patio is 5 feet wide. There was no way to feed a 10 foot gate through a 5 foot opening. And we need to be able to remove it in the unlikely event we needed to fix something. The DTW solution is to construct the gate in two parts. The heaver than hell carriage part has all the rolling parts is about 5 feet over all. It slides into the top and bottom rail system. Then the gate part is bolted to the carriage part for the overall length of about 10 and a half feet fit into a more or less 5 foot opening. Then the whole perfectly balanced system slides back and forth between the top and bottom rails.

If you look carefully you can see the rubber wheel up by the house that has just contacted the patio slab. It's not installed yet, but there will be a strike plate attached to the house to meet the gate when closed. Then there are two metal wheels in the carriage that always ride back on the footing. Above the two wheels in the carriage are two more wheels that roll on a track in the top rail. Letting the wheels into the frame is quite a feat. There is a wheel box constructed on each bottom corner, of DTW's design, around which the gate frame itself is built. The top wheels actually have a bit of adjustment available.

The locking latch (keyed alike for both courtyard gates of course) is itself in a box, of DTW's design, that forms another corner of the frame. In the pictures you can see it is covered with tape right now to keep the guts clean while welding and grinding take place.

Keeping the frame straight and true requires some not insignificant talent. In the first place it is 10 and a half feet long. And it bolts together from two pieces. And every time you weld something, the heat tends to pull the parts towards the weld. So you weld a little beat a little, weld a little beat a little, grind a little. Repeat.

As with the driveway gate, the footing track upon which the gate rolls is a rebared concrete masterpiece. The track itself is a piece of angle iron that sticks up into a groove in the wheels. To keep it straight and true, it has a truss, of DTW's design, that is welded to the rebar which then becomes a physical part of the concrete footing. The footing is tied into the wall with rebar and epoxy. They aren't go'n anywhere. The Welding and Concrete parts of DTW's experience are two crucial trades for the construction of the Quail Manor gates.

As with the driveway gate, if you look REAL closely at the top track, you will notice there are no visible fasteners. Again, of DTW's design. Here's a cross-section.

  • The top rail starts off as a rectangular channel. DTW cuts the face off one edge that will become the bottom of the top rail.. Ponder the challenge of evenly cutting a 10 and a half foot long piece of channel so the result is uniform. He does it free-hand. No saws involved.
  • We worked out how to mount the channel on the garage gate and used it again here. The idea is to create a key-way on the back of the channel. The key takes the weight of the channel and provides a place to which the channel can be bolted and removed if necessary for repair. To fabricate all this... 
    • He welds a length of quarter inch thick stock to the top half of the back of the top rail. Here again is the keeping the piece straight and true while the welding process is trying to warp it one way and another issue.
    • Then he temporarily tacks a similar piece of quarter inch stock to the bottom half of the top rail. These two pieces of stock form the key way. The bottom part of the key will be attached to the wall first, but HAS to line-up with the channel. By temporarily tack welding it to the channel he knows it won't move. Very much. Everything seems to move. I suspect it is a physical law to make fabrication as difficult as possible.
    • So he drills the holes though BOTH the channel and the stock at the same time so they are guaranteed to line-up. BUT, to get in there, he needs to drill access holes in what will become the outer face of the channel. So the bolt heads don't get in the way of the wheel that is going to roll in there the bolt heads have to be countersunk so they sit flush with the inner surface of the channel. The countersink is a pretty good size bit so the access holes in the outer face have to be big enough for that too. Drilling and countersinking ensue.
    • Then he removes the bottom part of the key that was attached temporarily. These holes get tapped so they will accept the bolts that go through the channel and hold the channel tight to the wall.
    • But first, the bottom part of the key has another set of holes drilled and countersunk so the bottom part of the key can be attached to the wall with what are called "Tapcons". Something about the thread design of the tapcons make them just perfect for attaching stuff to concrete. Once the bottom part of the key is attached, the channel with the top part of the key can be rested on the already attached bottom part of the key and then politely bolted together using an allen wrench that can be fit up inside the channel without any access holes required.
    • We started this dissertation with the statement that there are no visible fasteners. So before the channel is reunited with the bottom part of the key, these access holes in the outer channel face have have to be plug welded and ground smooth. On the outside AND on the inside.
    • Frequent readers will recall we let all this metal rust. But. We don't want the inside of the channel rusting. There are parts sliding around it there. So DTW sprays some galvanized paint up in there.
  • It's a marvel.

Here is a little tutorial on plug welding.

Feeling First Folks, rejoin here.