Default wrote:

The design will be a rectangle, length of 2.5 meters, height of 1.5
meters, with a brace running from the bottom of the hinged side, to the
top of the swinging side.

Why the brace the wrong way?

What type of material should I be using?

Steel :-)


I was thinking box tube of 20x20mm, or 50x20 if required.

20*20 is ridiculous. I would use a 40 * 40.
A 50 * 20 would be OK for vertical load (if the profile is standing),
but it will just warp and wiggle in the plane.


I guess I don't want a thin wall.

Yes. Then practice.

What wall thickness should I be looking at?

1.5mm, maximum 2mm


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

According to Nick Müller :
Default wrote:

The design will be a rectangle, length of 2.5 meters, height of 1.5
meters, with a brace running from the bottom of the hinged side, to the
top of the swinging side.

Why the brace the wrong way?

Exactly. The way you have it described, the diagonal member
will be in compression, and thus likely to buckle under load. And
*don't* bet that nobody would ever try riding the end of the gate.
Someone *will* do that.

Running from the top at the hinge end to the bottom at the free
end will put the diagonal member in tension, which will make it
stronger.

Aside from that -- I'll let the others comment on the size of
the material, as I have not made anything of that size.

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Roger wrote:

Interesting, I was under the impression that a brace employing
compression was more effectinve than tension.

But only if you intend to make it from concrete. :-)

No, always try to make expand them, not compress. If it is compressed,
it will swing to the side. Euler made a formula (don't know how you call
it in the US) that shows how little long, slim parts can take if
compressed. It is _veery_ little. Imagine using a rope/chain.

Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

Roger wrote:

Considering the gate when closed will be suppoprted top and bottom on
both sides when closed, there should be no wiggle.

But while you close it. It should be stable in all conditions. Also, it
will look very lousy.
Really, you won't get happy with a 20*50.
The absolute minimum would be a 30*30*2 + a 8mm (or so) brace.

1.5mm, maximum 2mm

Looking at Kalus' post which says 2.5mm, and your 2mm maximum, was there
a reason for that?

Yea, well. If you have the brace, you don't need that much stiffness (to
prevent sag). Also, it is a good training for your welding skills with
1.5mm :-)
I think it's unnecessary to have 2.5mm. But if you want, go for it. It
will just weight more and cost a bit more. And is easier to weld.

Oh!
As this is your first welding project, some tips:
First cut _all_ parts (excluding brace) and lay them out. Use C-clamps
to fix. Tack weld in the middle of the seam. If you have someone to lend
you a hand, flipp over and tack the other side. If you are alone, don't
flipp the frame over, or it will fall apart (well it can be done alone,
but only if you know how and have the right welding bench).
Watch to weld "center-center". That means, do not weld in one go, but
start in the center and weld outwards, then from the center inwards. If
not, you will get out of the right angle. Finish one side (frame laying
flat). Let cool down, check the right angle and weld on the other side
to correct. If you have less than 90 degree, weld from the inner side to
the outer.
If you have experience, you can correct any errors by changing the
sequence and welding "in-out" or "out-in" etc. Also, you don't need to
let cool down. A "bit" tricky!

A OA-torch can be quite handy for corrections. But this is another
lesson to learn. :-)

While I am at correcting:
Meassure the diagonals. Where the longer diagonal is, put your brace in.
You can correct a few mm with it. Only then weld the hinges. Because now
you know where left/right and top/bottom is.

For the hinges:
We have here (in Germany) _very_ nice and _very_ cheap and _very_ good
weld-on hinges. I would use at least 120mm hinges. Go look for them. It
is not worth at all making your own ones.


HTH, enjoy!

Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

"Roger" wrote in message
.au...
In article rs.com,
says...
According to Nick Müller :
Default wrote:

The design will be a rectangle, length of 2.5 meters, height of 1.5
meters, with a brace running from the bottom of the hinged side, to
the
top of the swinging side.

Why the brace the wrong way?

Exactly. The way you have it described, the diagonal member
will be in compression, and thus likely to buckle under load. And
*don't* bet that nobody would ever try riding the end of the gate.
Someone *will* do that.

Running from the top at the hinge end to the bottom at the free
end will put the diagonal member in tension, which will make it
stronger.


Interesting, I was under the impression that a brace employing
compression was more effectinve than tension.

Just as well I asked

Roger.

I have made many gates, once having been a steel erection contractor for
nine years, making ornamental metal.

I believe all things steel should be made to support three times what they
need to support. A gate of this size made of the proper materials will
easily support the 3x weight. But that doesn't allow for the fat little
brat that will try to ride on it.

Hence, the "banjo string" tensioner. A solid diagonal brace that is solid
running from the top of the post side of the gate to the bottom of the
swinging side of the gate is okay, but it does not allow for tensioning.
AND, a diagonal going the other wrong direction does not allow for
retensioning if it every becomes tweaked for any reason. It must be removed
and replaced, which may involve a lot of cutting and blasting.

A simple aircraft cable or single rod/allthread tensioning system allows for
lifetime adjustment of the gate. Posts settle. Earth moves. People hit
the gate. Fat little kids ride on it. Fat 32 year old kids ride on it.

One of the surprising things about gates of this type is their flexibility.
I used to have to straighten a lot of gates. A remarkable amount of
straightening can be done by laying the gate on bricks on the ground and
jumping on it. A remarkable amount of straightening can be done with a
come-along on the diagonal. Use soft nylon slings to hook on to the steel
so you don't cause more bends. You think they are solid, and they are
heavy, and they feel solid. But they tweak really easily.

This person is talking about putting backing on the gate. If this is done,
AND A NUMEROUS AMOUNT of screws are placed to hold on the backing, this adds
a LOT of rigidity to the piece. Just, please, use a measuring tape and put
them on at even spacing! I get so riled when I see a good looking gate with
backing that looks like a drunk monkey put in the screws. It isn't hard to
follow a tape to evenly space the screws, and it adds LOTS to the final
appearance. So does good cutting of the backing pieces, particularly around
locks and latches. Looks like a real pro did it. A person who knows ZERO
about gates can see the difference between even screws and ones put on
helter skelter. However, the banjo string will make the backing deform if
it has to be tensioned a lot. In that case, the screws may have to be
removed until the backing lays flat again. But, if that happens, there may
be enough damage to just replace the backing.

Just some observations from messing with that stuff longer than I care to
remember.

Banjo string tensioners are cheap and work really well.

Steve

That might be true for a steel gate but a wood gate works better in
compression. In wood, the joints fail long before the the crossmember
buckles.

DoN. Nichols wrote:
According to Nick Müller :

Default wrote:


The design will be a rectangle, length of 2.5 meters, height of 1.5
meters, with a brace running from the bottom of the hinged side, to the
top of the swinging side.

Why the brace the wrong way?


Exactly. The way you have it described, the diagonal member
will be in compression, and thus likely to buckle under load. And
*don't* bet that nobody would ever try riding the end of the gate.
Someone *will* do that.

Running from the top at the hinge end to the bottom at the free
end will put the diagonal member in tension, which will make it
stronger.

Aside from that -- I'll let the others comment on the size of
the material, as I have not made anything of that size.

Good Luck,
DoN.

According to RoyJ :
DoN. Nichols wrote:

According to Nick Müller :

Default wrote:

The design will be a rectangle, length of 2.5 meters, height of 1.5
meters, with a brace running from the bottom of the hinged side, to the
top of the swinging side.

Why the brace the wrong way?

Exactly. The way you have it described, the diagonal member
will be in compression, and thus likely to buckle under load. And
*don't* bet that nobody would ever try riding the end of the gate.
Someone *will* do that.

Running from the top at the hinge end to the bottom at the free
end will put the diagonal member in tension, which will make it
stronger.

[ ... ]

That might be true for a steel gate but a wood gate works better in
compression. In wood, the joints fail long before the the crossmember
buckles.

O.K. I can accept that. But he was talking about building a
steel gate, not a wooden one.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---