Optimal angle for a gate support - simple engineering

[Bill Edwards]

Thanks.
My thinking is that if I get the top support halfway (ish) then it can take at least half of the weight, effectively turning the gate into two sections - one gate hung by hinges, the other half held by the brace. Two smaller sized gates, either of which will be fine to take their own weight - I'm just splitting the big one into two really, from a weight/force point of view. But knowing exactly where to put the top support was something I wasn't certain about.
Fitting the hinges right at the top or bottom is a good idea but less than practical as it needs to be easy to give them a tweak from time to time as things drop - hopefully not the gate, but the hinges will certainly wear after a while. Anything other than easily purchased, standard gate hinges are best avoided for this because if they seize, break etc it needs to be easy to cut them off and replace them without any fabrication.

The whole thing is a little wobbly with 40mm box, but that isn't such an issue, it's the thing bending anywhere that causes concern.

 

[chevy2]

As its a farm gate and appearance is not that important and going by its intended length i'd be inclined to fit not only one diagonal cable/bar but two,
One at the end of the gate and one in the centre as this will take any whip out of the gate and reduce the chance of cracking over time.

 

[chevy2]

Thanks.
My thinking is that if I get the top support halfway (ish) then it can take at least half of the weight, effectively turning the gate into two sections - one gate hung by hinges, the other half held by the brace. Two smaller sized gates, either of which will be fine to take their own weight - I'm just splitting the big one into two really, from a weight/force point of view. But knowing exactly where to put the top support was something I wasn't certain about.
Fitting the hinges right at the top or bottom is a good idea but less than practical as it needs to be easy to give them a tweak from time to time as things drop - hopefully not the gate, but the hinges will certainly wear after a while. Anything other than easily purchased, standard gate hinges are best avoided for this because if they seize, break etc it needs to be easy to cut them off and replace them without any fabrication.

The whole thing is a little wobbly with 40mm box, but that isn't such an issue, it's the thing bending anywhere that causes concern.

Use the larger hook and eye type hinges which use locknuts on either side of where the hinge goes through the gate,
easy to replace if they break and cheap to buy.

 

[Bill Edwards]

I take it you mean this type?
http://www.ebay.co.uk/itm/2-ADJUSTA...464?pt=LH_DefaultDomain_3&hash=item3f0a09a750

This is all that's used on the farm in varying sizes as they are readily available, strong and have more than one size.

 

[chevy2]

I take it you mean this type?
http://www.ebay.co.uk/itm/2-ADJUSTA...464?pt=LH_DefaultDomain_3&hash=item3f0a09a750

This is all that's used on the farm in varying sizes as they are readily available, strong and have more than one size.

Yeah they're the ones, i've seen them used on some real big commercial gates with about a 30mm thread and bore hole for the pin.

 

[KemppiFrog]

Thanks.
My thinking is that if I get the top support halfway (ish) then it can take at least half of the weight,

Actually, if you put it half way, then it is taking all the weight, with a component compressing the inner section against the hinge line. If the brace was vertical, than it would be supporting the actual weight, the load on it increases as the angle towards the pillar decreases, with a maximum at horizontal. This load would be the weight of the gate on a lever of half the gate width x the height as a fraction of the half width. i.e. if the gate width was 4 x its height the tensile load on the top hinge would be twice the weight.

(I think I got that right..)
KF

 

[DrNik]

Pedro, has it, if you only have the top of the diagonal on its own hinge, if it starts to bind it will just twist the box section, also the hinge will be dragged downwards at 45 degrees, and snap it off, the box running along all of the hinge is the best

 

[wyn]

If you are using eyebolts i would also weld tube through the box section for them to run through.

 

[Bill Edwards]

Thanks, I installed crush tubes - I know what would happen if I didn't!

I'm ready to hang it so when I get the chance I'll do so and see how it goes, with an attempt to get the top brace at 45 degrees. If it's not good enough for whatever reason it can soon come down for alterations.