Bending box section

[mo_bhaiyat]

I want to make a a frame to sit my fish tank as the old wooden cabinet is worse for wear. The problem I face is that it's not just a normal rectangular box.




Firstly what size box section would people recommend making a frame from, it will be holding approximately 250-300kgs

Secondly I have no clue where to start with forming the front arc so any advice or even pointing me towards someone who could bend the box section would be great.

 

[DanielW]

You going local for the box section? makes sense as it normally works out cheaper sometimes.

Ask the your supplier can they bend box section for you,they will probably charge you a couple of quis? I know my local metal supplier charges a £1 per length if I want the box section cut down to size.
If they can bend the box section? take a cardboard template for the bend of the arc you want.

 

[blenkie1]

you could try and put a series of cuts in the box (25x25?) and pull it round till you get the arc you need and then weld the cuts up and smooth off. you would hardly tell as the cuts would be on the inside. Rolling it would be easier if you can get someone to roll it.

Here is some 100x50 box that i did. Once painted you can hardly tell its been cut

 

[Hitch]

Box section can be rolled fairly easily to larger radi without hardly and distortion to the profile. We tend to put it through the plate rolls for speed if its not a tight radius.
Id be aiming for something along the lines of 40*40*3, but probably easiest to find somewhere with a roller and check what they can do for you. Theyd probably prefer to supply the box for it too, unless youve already bought it.
If you supply it, don't cut it to the length of the curve, probably want about 400mm each end to play with (more or less, depending on the machine)

Template wise, You could create a 'sweep', a small piece of plate/ply/card with the relevant radius cut on one end, but for that job, i'd be inclined to make a full size template of the inside of the curve, slightly longer than you need, and clearly mark that it is the inside radius on it.
If you make the inside, as the box gets rolled, they can just offer the template up to it and easily see if it needs more rolling.

 

[mo_bhaiyat]

I didn't even think of that. I'm gonna try and ring some local steel guys to see if they can roll it.

 

[fixerupper]

If you know someone with the kit get them rolled, or if the bend is tight and or the steel is heavy gauge set up the chop saw and cut through 3 sides of the box evenly spaced ,clamp the steel to the right curve and weld it up again ...done this a few times and it takes time but works well.
If you are using light gauge inch box and the curve is slight, you can bend it around a ply wood former I've done this a few times ,it's quick but you have to 'go for it' and not hesitate half way round ....jeff...

 

[DanielW]

Probably cheaper to have your supplier to roll it if they do but....

check out local tool hire shops some hire out hydrualic pipe benders like this one,don't know if they have the means for doing square 40mm to 50mm box sections?

http://www.nationaltoolhireshops.co.uk/product/hydraulic-pipe-bender-1_2in-to-2in-for-hire/

 

[mo_bhaiyat]

I haven't bought anything yet, it's just the idea in my head at the minute. Will probably get the guys who can roll it to supply the box aswell the only problem is its bank holiday Monday and everywhere is closed. I'd like to avoid using the many cut method if I can because at the moment time is a premium and also I'm being lazy but I suppose it would give me much needed welding practice. Haven't touched a welder in a good few years.
@Hitch - Good thinking on leaving the length oversize on forming.
@fixerupper - I've seen the hand bending method done on YouTube but I'll try and avoid that for now too.
Anyone recommend someone/company up my way?? Or do you have a sponsor section like other forums??

 

[blenkie1]

Much easier and a better finish rolling. Cutting and welding is time consuming but if thats all you have. Another thing is once you start welding that perfect arc you had when started can quickly get out of shape.

 

[outofthefire]

The cheapest way is to make pattern by cutting the profile you want out of some mdf or other scrap wood. Then make the series of cuts already mentioned, bend the box round your pattern then weld it up. Trouble with bending box is the sidewalls tend to distort.

 

[Fazerruss]

You don't need to roll it. Box section up to 25 mm can be bent round a plywood template.

 

[mo_bhaiyat]

Would 25mm be sufficient to build this frame??

 

[Wendelspanswick]

Would 25mm be sufficient to build this frame??

Depends on how many braces you put in.

 

[mo_bhaiyat]

Excuse the crude drawing but I was hoping to go with a basic frame like this:

 

[pedrobedro]

How much curve is there on it ? If it's only slight I would put a length of 25 x2mm RHS between two blocks and stand on it then cut what you want out of it. It bends quite far before it kinks. I've had some delivered before and had to do the opposite to straighten it back out after it's been hung up for a while. Just make a triangle shape base and use a thick wooden top with the curve cut on that, it will still support your tank without complications.

 

[mo_bhaiyat]

The reason I want the curve is so I can then clad it following the curve and attach the facias cladding to the frame using magnets. The arc is literally a quarter of a circle radius 70cm.

 

[Robotstar5]

Probably need a vertical support leg under the front centre of the arc?.

 

[mike os]

with a leg in the middle of the arc 25mm box is plenty.... and is probably good without the leg, but because of the shape I would add one.

I am more than happy spanning up to 1250 on 25 box for normal tanks

you will want a ply top on it too

 

[mo_bhaiyat]

Thanks for all the replies. I've found a local firm who has ring rollers and so I'm going to pop down on Friday and see what we can sort out, he says it shouldn't be a problem. Could I get away with 40mm without the vertical support leg at the front if the arc?? I wanna keep it so I can access the sump tank that will be underneath with no restrictions.

Hear you loud and clear mike, will defo ply the top. Any recommendations on how to attach it to the frame or just simply plonk it on and it we stay in place with the weight of the tank??

 

[mike os]

if you want no leg then 40x25 or 50 x 25 should be fine

I normally screw the ply... just 2 or 3 to hols it in place otherwise it slides when you try to position the tank... pull the screws 2-3mm below the surface

a jewel trignon?