Cantilever gate, 18' opening, 27-foot overall metal selection

[workinallthetime]

We are looking at building a new cantilever gate for more privacy and security around the place. Wondering if anyone in the community on here has any advice for wall thickness on the frame. I have two plans I am working with in my head right now, plan one uses 2x2 square tubing all the way around and plan 2 uses 2x4 or 2x6 square tube on the lower and 2 x 2 around the rest of the frame. I have welded 2" "uprights" every 4 feet to maintain the structure of the cantilever with 3/4 tubing for the pickets.

 

[zzvyb6]

Make up a model of your configuration with soda straws and super glue. Then you should be able to recognize where the deficiency is: It will 'matchbox' and sag at the unhinged end. If it really must be that wide of a gate, put rollers on it and a good weatherproof guide track so that it slides across on a rail. Plus, the moment needed to support a hinged load would need pilings to keep it in place and they WILL bend. What about an opener?

 

[workinallthetime]

The gate opener will be a Liftmaster CSL24UL. The gate post will be 4" heavy wall set 36" deep with 24" concrete around. Located the rollers for 2" square tube on 4" square tube post.
Rollers are not an option for me on gravel, and dual swing gates are not ideal for this.

 

[TripleS]

If it's going to be that big you need to design it to slide open instead of swing open.

 

[flyerdan]

I've built scads of cantilever gates, all the way up to 57'. You've got the right idea, we'd generally go 2/3 - 1/3 for the bays. I'd recommend having three six foot bays for the opening and two smaller for the tail. For something that small, I'd use 2x2 .095 for the outer framework and .065 for the uprights and interior. Maybe use .095 for the upright post between the opening and tail section.
You will need to have some truss rods to tweak it level and take any sag out that might occur later, placed thus: I\I\I\I/I/I
Picket material could be 3/4" on that and look good; we'd usually use 5/8" for pickets unless the customer specified other, probably depend on your tastes and pricing options.
Forgot to mention - if you're using an operator you'll want a strongback on it so it will track true without flopping about at the latch end, most of our gates were round stock so we'd use 1.375" top rail. You could use 1 or 1 1/4 square in 0.65 with about a 6" center to 2" ends arc, that would stiffen it right up.

 

[workinallthetime]

If it's going to be that big you need to design it to slide open instead of swing open.

Absolutely, cantilever style with the 50% rule.

 

[workinallthetime]

I've built scads of cantilever gates, all the way up to 57'. You've got the right idea, we'd generally go 2/3 - 1/3 for the bays. I'd recommend having three six foot bays for the opening and two smaller for the tail. For something that small, I'd use 2x2 .095 for the outer framework and .065 for the uprights and interior. Maybe use .095 for the upright post between the opening and tail section.
You will need to have some truss rods to tweak it level and take any sag out that might occur later, placed thus: I\I\I\I/I/I
Picket material could be 3/4" on that and look good; we'd usually use 5/8" for pickets unless the customer specified other, probably depend on your tastes and pricing options.
Forgot to mention - if you're using an operator you'll want a strongback on it so it will track true without flopping about at the latch end, most of our gates were round stock so we'd use 1.375" top rail. You could use 1 or 1 1/4 square in 0.65 with about a 6" center to 2" ends arc, that would stiffen it right up.

Thank you for the info, as you know in the world of cantilever gates an 18-foot opening isn't much. I do like the idea of a "strongback", I have experienced a 24' chainlink unit that would not close in high wind. That one was so bad the opener went into full tilt and just shut down.
Do you think the .120 wall is overkill or too much weight? The only other advice I have received was "schedule 40" for the frame, which I know is unnecessary. I also think the 2x4 bottom will add some rigidity to the structure and look good.
Thanks again!!!

 

[TripleS]

Absolutely, cantilever style with the 50% rule.

I thought cantilever means the track is top only and slides back , with a gate that big id put a track on the bottom also with wheels.

 

[flyerdan]

The .120" wall seems a bit excessive, as with the 2x4 bottom as the structure gets its strength more from design than the material, per se. If the extra cost isn't an issue and for aesthetics, you can use the heavier materials for peace of mind; the extra weight won't be an issue. The strongback concept is illustrated in the pic, it's about a third down from the top, but that can be varied for what appeals to you. The reason for the 90 degree attachment point at the end is in case there is ever an obstruction cuff put on in the future, it will fit right on. Also, if the latch end has to go into a pocketed receiver it will fit in as well. I started doing that on all the gates so it wouldn't be an issue later, would make them up from drop during down time. The pic is a 51' made of 2.375" DQ-40, a step below sh.80 but with higher tensile strength. We could get that in 38' sticks.

*TripleS*: the cantilever gates roll on 4 rollers spaced on 2 posts, kind of like a drawer slide. Properly built and set up, the roll quite easily

 

[workinallthetime]

The .120" wall seems a bit excessive, as with the 2x4 bottom as the structure gets its strength more from design than the material, per se. If the extra cost isn't an issue and for aesthetics, you can use the heavier materials for peace of mind; the extra weight won't be an issue. The strongback concept is illustrated in the pic, it's about a third down from the top, but that can be varied for what appeals to you. The reason for the 90 degree attachment point at the end is in case there is ever an obstruction cuff put on in the future, it will fit right on. Also, if the latch end has to go into a pocketed receiver it will fit in as well. I started doing that on all the gates so it wouldn't be an issue later, would make them up from drop during down time. The pic is a 51' made of 2.375" DQ-40, a step below sh.80 but with higher tensile strength. We could get that in 38' sticks.

*TripleS*: the cantilever gates roll on 4 rollers spaced on 2 posts, kind of like a drawer slide. Properly built and set up, the roll quite easilyView attachment 861156

A wealth of info, I do appreciate it. I will start pricing out the material this week. On the strong-back, I will be able to conceal it behind my detail where the pickets are offset 1 foot below the top. That is not quite 1/3rd down but should still provide the support needed.