Just remembered you live in the land of the metric system, conversions of scale should be even easier.

Jake

Jake Balcom
Mettle Design
Lincoln, NE

Stephen Fitz-Gerald

All the above is good advice...
Just a few points I'd like to reiterate to save you any possibility of mistakes...
A real size TEMPLATE is ALWAYS the best way to show the guy on the rolling mill what you really want.
Enlarging your sketch to life size requires a big clear space on a floor you can make marks on.I usually use big sheets of cardboard stapled together and laid on the floor.Big Radius curves in real size can be accomplished by putting a nail in the floor and tying a string onto a piece of chalk (or a Sharpie for instance),to inscribe the arc on the cardboard.Keeping tension on the string (set at the appropriate radius)as you scribe on the floor template is like using a giant compass.
If you only provide a sketch to the guys on the rolling machine MAKE SURE YOU DESIGNATE THAT IT"S RADIUS and not diameter.When they roll a big 20 foot piece of steel they will always "burn" about a foot on either end that does not get rolled,so count on that downfall...
Hmmmm,did I miss anything?
Just keep asking questions here if you're still confused.
I've done this a million times but it's often difficult to elucidate IN WORDS each step in a process that has simply become wrote after so many years...

Will, sometimes I put in a small straight piece between the two curves to act as a transition. Also, if you have or know someone that has a cad program of any sort, this could all be figured out very accurately in a matter of minutes. For estimation purposes however changing the radius by a little bit shouldn't make any difference in the costs. You know you'll need two or three pieces and their approximate size and radius so you probably have enough info for the estimate already.

Another option is to plasma cut the profile and weld flat bar to the top and bottom, creating your own tube. More work welding and cleaning, but you don't have to worry about matching curves up.

Jake

Jake Balcom
Mettle Design
Lincoln, NE

Stephen Fitz-Gerald

Will,
One other thing I forgot to mention is there is a distinct possibility that the tube you designated to be rolled may crush a bit if it's any thinner than 1/8th inch thick.I personally think that's an awfully big dimensional tube for a typical driveway gate. Is there really a need for it to be that big? If it were my gig I'd try to convince the clients to go with SQUARE TUBING of a lesser OUTSIDE dimension,but a THICKER WALL. This would provide less weight overall,with greater strength,and negate the possibility of crushing or distorting when rolled.
Just a thought...

Mmm.. it is an odd section for a gate frame.. but I think it's one of the things that makes the gate interesting..ish.
More like the profile of a wooden gate frame.
I'm actually struggling to find a source for this hollow section right now, as my normal supplier doesn't do it.
Just working out a price for this project is getting to be hard work ! Will Jones

Hey Jake,
That's not the craziest idea in the world, to fabricate my own tube.....
Will Jones

there is a common tangent to the two curves where they meet and you will find that cutting the ends with matching angles will give you a clean transition.
if you have an H press, you can do this yourself provided you move slowly and use wood or plastic as your pressure points ....also a close fitting wall each side will slop bulging.

Where to bend next ... www.metalgarden.ca

Thanks Giusseppe,
I do have a 20 ton press - If I can pick up a few off cuts of big box section it might be worth experimenting....I'd love to do it in house if it's possible.
Will Jones

Will, have you tried Hub Le Bas ? they do ERW rectangular hollow section, I know they do 120mm x 60mm x 3mm.
How about rolling the top rails in one piece to get a constant radius then cutting into 2 pieces.
David.