Gate design

[daveturnbull]

I need to make a new gate for the side of the house. It's LR related because that's what will need to pass through it 🙃

It needs to be a single gate due to width restrictions. I'd like to make a metal frame, and then fix some 4" pales to one side with 1/2" spacing.

My question is, what size box section (and possibly angle for the diagonals) should I be looking at to keep it sturdy yet as light as possible?

[steve b]

50x50x2.5 for the outer frame and 30x30x2.5 for the internal braces flush to outside should do it . A horizontal half way up would aid in fixing the wood .

cheers

Steve b

[bishbosh]

Suggest also that both diagonals run from top left to bottom right, assuming hinge is on left hand side and that you are welding the joints. Reason being that your highest loaded, and longest member   (inner diagonal) is in tension. You could in theory use round bar for the diagonals to save weight but that would make fixing the wood a tad challenging!  Angles would be good for the diagonals, sized to suit your preferred fixing method/ the rectangular frame can be box, angle or channel section, again to suit your chosen fixing method.

Having said all that though, realistically, strength isn't the issue here, it is fixing the wood and having enough stiffness to not twist a lot when in use, but at 1.8m high you're going to get a fair bit of that unless you go for silly big sections.

Box is prettier, angle is lighter and easier to attach stuff to without creating water traps.  

[Anderzander]

The diagonals in a braced wooden door normally run down to the hinge side - the weight on the outside edge is supported from the hinged side.

[zardos]

Gates of this size tend to be slide gates not hinged because the amount of force caused by the weight and leverage will need a very substantial point to fix to and probably multiple fixings to stop them pulling out.
I've seen some gates with a taller hinge side with a diagonal down bar to help support the weight.

The other option for hinged is to have a wheel/caster on the un-hinged end to help support the weight (then your un-hinged side diagonal is the right direction otherwise as @Anderzander say both should run down to the hinged side)

[ianmayco68]

I actually make gates for a living first time a question has come up about my job 😀  , with a gate that size we would diagonal brace it from top hinged side to bottom lock side and use 20mm hinges and a100x100 post .  What type of wood are you using to cover it and do you want the wood to fit internally or fit to the outside of the frame . 

[daveturnbull]

😁 Ah ha, a professional! 

I was probably going to use roofing battens, either 38mm or 50mm ones. 3 of them fixed to the outside Metalwork horizontally (top, middle, bottom) then lots of vertical ones with small spacing between fixed onto those. 

For the post, as big as required, and it can be fixed to a brick wall for extra strength. 

My initial thoughts for the steel frame were 40mm x 3mm box section, but after talking to a farmer friend he thought that was overkill, hence my question. 

[steve b]

The diagonal tension brace is the key thing to put in your design and lose the two diagonals  , something I forgot to say . If you build it and it is too flexible then the runner wheel is an easy fix .

cheers

Steve b

[ianmayco68]

I’ll have a word with the drawing bloke Sam at work tomorrow for you Dave see what he suggests if you like ? You might get away with 40x40 box , how are you planning on fixing the wood on Nuts and bolts , screws ? Also how are you locking it ? 

[Anderzander]

<must resist asking gate questions !>

[daveturnbull]

For the horizontal pieces, bolt them on. For the verticals just woodscrews as they will be going into timber. 

For the latch, I have limited space right up against the fence, so I was thinking of chopping a section of fence out, setting in a new post at the right place then welding a D loop onto the gate and a simple automatic latch like you find on field gates. 

[Ed Poore]

All I'll say is that's not a particularly big gate and shouldn't have to much issue. The gates you can see in the background at a mates yard are over 8ft wide for each leaf. Can, if you're super careful squeeze a lorry through with just one open.

I think the beams there making up the gate are 50x50x3 box with 3/4" wood on it. The two posts have a 150x150x5 box sink into 12 cube of concrete (very loose ground). Normally we'd tie the two posts together but with the amount of concrete placed under each post it wasn't deemed necessary. Over the last 2 years (Gates have been there for about 30) the post on the left started leaning because tree roots from the wood next door started levering it up. So a tractor and forestry winch were employed to pull it back and gurt big I beam has been welded between the two posts to help keep them upright.

My main point being when you consider the size of those gates and they've not sagged (ignoring the Mother Nature effect) the trick will be not to over engineer it. Being metal you can always weld more on if needbe.

If you can don't just sink a post in the ground but also put some horizontal beams out to support it when the gate is open / shut. Had you had two leaves it can also serve has a handy conduit for running cables across. Mind you that's because the last few gates I've been involved with we've been installing electro hydraulic actuators and all sorts of gubbins on them.

[ianmayco68]

Bit of gate/fab porn for everyone 

40x40 should be fine as long as you use 2.5 or 3 mm wall tube and he wouldn’t bother with a diagonal brace but he’d put a middle horizontal rail in rather than the vertical one , and you could tell-screw the wood straight to the frame.

[daveturnbull]

Thanks Ian. What's a tell-screw? 

[Glue]

19 minutes ago, daveturnbull said:

Thanks Ian. What's a tell-screw? 

I suspect its Auto Correct  Cock Up for "Tek Screw"

[Ed Poore]

There have been quite a few threads on mig-welding.co.uk recently about building gates. One notable one was KimB's thread where we (spent a long time on the phone to her) managed to get a bi-fold gate working. Covered about the same width as your gate but in two leaves so that when it was open it occupied less space (due to the design of her garden). Chap who's gates are in the picture above also fabbed up some gate posts for a client which shows the big H-beam that was sunk into the ground. That was a bit different because of planning in the Surrey Hills it could only be a 7-bar farm gate initially.

Might be worth a look at those threads for inspiration.

[ianmayco68]

Yep bloody auto correct, Glue is correct should have been Tek screw .

[bishbosh]

On 8/5/2020 at 1:28 PM, Anderzander said:

The diagonals in a braced wooden door normally run down to the hinge side - the weight on the outside edge is supported from the hinged side.

That's because welded joints are somewhat less prone to movement than timber joints. If it was a timber gate I'd agree and have the diagonal in compression to minimise any movement as the joint takes up load.

[Ed Poore]

Also bear in mind that steel is good in tension (think rebar inside concrete, rebar for the tension and concrete for compression), wood tends to be better in compression than tension hence why braces tend to be in the opposite direction.

[Blanco]

Yep  traditonal timber gates and doors are more about joint design and longevity than material properties. With modern epoxy adhesives that can change but it can be quite technical.