Bending or Welding Aluminium?

[C08]

I need to make a couple of bracket shaped fittings. They need to be sturdy and I am thinking of 20mmx10mm aluminium strip. If it is possible to bend this thickness to a right angle (the bends do not have to be sharp but not too long) then I will buy some strip and bend it myself but if it will not bend then I will have to go to a welding shop and pay them to weld them up. I am thinking of aluminium as they will bolt to the alloy body of an outboard engine.and this avoid the dissimilar metals problem.
Any ideas-it is a long time since I bent any aluminium and then it was a much thinner section.

 

[paul-essex]

buy angle section

 

[fisherman]

I use 30x5 or so, and it is difficult to get a neat bend in it, you'll have to beat it, and it will 'cup'. I asked the local engineer to put a 90 deg in it, he complained that it took a lot of time, and handed me a hockey stick. Should have realised he would find the most difficult way.

 

[C08]

Thanks for the suggestion but the shape I want is a straight length about 2 inches then a right angle and a straight length of 4 inches and another right angle with a 5 inch length. The 2" and the 5" end up parallel but facing in opposite directions.

 

[C08]

I use 30x5 or so, and it is difficult to get a neat bend in it, you'll have to beat it, and it will 'cup'. I asked the local engineer to put a 90 deg in it, he complained that it took a lot of time, and handed me a hockey stick. Should have realised he would find the most difficult way.

I am not bothered about a bit of curve to achieve the 90 degrees but I am not sure about whether you can bend 10mm? Perhaps if I bent around a bar of say of 1" diameter that would achieve my shape ok?

 

[smithy]

It will help if you anneal it first and then maybe again as it work hardens halfway through the bend. Put some soap on it and use this as a temperature indicator. When the soap turns black stop heating and leave to cool.

 

[fisherman]

Just get it cut and welded.

 

[Iliade]

Your nearest double glazier may have a bender capable of doing this.

I do know that Lewes Glass have one. Quite why I don't know.

 

[Jassira]

Why not just buy a bit and have a go, if it won't bend you can always cut it and have it welded, just buy it a bit longer than you need to give you a bit waste to play with.

 

[jonjo]

I am no expert but since I still hanker after getting a Malo style mainsheet arch fitted to my yacht I have been reading up on different aluminium alloys. Make sure you pick a variety that is known to tollerate forming.

 

[vyv_cox]

You don't tell us what these brackets will be for but my assumption from the dimensions is that they will be required to support some considerable load? Aluminium strip bent to a right angle is far from the ideal material for the job, it will be difficult to ensure that it is not cracked during the bending process and once in place, with a cyclic stress imposed by an outboard motor swing from them, the brackets will fatigue quite quickly.
Stainless steel is widely used in combination with aluminium, has far greater strength in smaller sections that can be bent fairly easily. Galvanic corrosion should not be an issue if Duralac is used, and presumably the brackets will be bolted on using stainless steel bolts anyway.

 

[macd]

I have my doubts about those tight bends in that size bar, particularly close to the end of the piece. It'll help if you make the 'tail' of the bend too long, then cut it off later. It'll also help if you soften the aluminium by heating: smear on a light coat of Fairy liquid, heat with a blowtorch until it goes chocolate brown...then stop, because it'll melt shortly after if you don't. The piece will stay soft for a while after cooling. Aluminium alloys vary appreciably in their willingness to be annealed in this way.

Seawater-resistant aluminium alloys usually also contain magnesium. AlMg5 is quite widely used in marine applications, but I think mainly as a casting alloy. Any of them may be tricky to source in small quantities. Any untreated 'normal' alloy will be very prone to corrosion unless anodised or surface coated. Powder coating should last a few years, although it usually seems to let go eventually.

 

[noelex]

The minimum bend radius for 10mm 5083 is about 20mm for H111 temper and 25mm for H321. This means what you are trying to achieve would just be possible (if I understand it correctly) with bending.

However, it would be much easier and simpler to cut and weld the parts. I also think this would be more reliable. Bending aluminium in this sort of tight radius needs a lot of expertise and the results from a DIY effort would be unpredictable in terms of strength. The cost of proffesional welding will not be much.

If you do weld the joints consider incorporating some gussets at the 90° joints if this is possible.

 

[prof pat pending]

Or get it machined out of a flat plate.

A more expensive route, but you'll get a more reliable part and it will be the shape you want

 

[macd]

I am thinking of aluminium as they will bolt to the alloy body of an outboard engine.and this avoid the dissimilar metals problem.

So you'll be using aluminium fasteners, too?

 

[C08]

Thanks for some constructive comments. The brackets are to bolt to the rear of my 20hp outboard main engine (cat) to enable the engine to swivel via linked lines to the bar connecting the rudders. This should give me about +/- 35 degrees of swivel and make an enormous difference to berthing the boat.
I could just get the brackets welded up but the last welding job I had done cost me double what I thought it was worth so I would rather do it my self if possible.

 

[Steve_N]

I could just get the brackets welded up but the last welding job I had done cost me double what I thought it was worth

I think it's quite common to think that welding should be cheap, a misconception coming from arc welding I guess.
As for TIG welding stainless (which I'm guessing it was) anyone who has set themselves up to TIG as a hobby welder can tell you how expensive it is in terms of time, equipment, consumables, cylinder rental etc. It's an eye opener. And that's before you get onto the treating, polishing etc. of the finished piece.

 

[lw395]

Why not just use the steering connection already on the outboard?
I struggle to visualise the set up, it seems very complex to link the tiller of the outboard to the tillers of the cat.
Surely the forces are not so huge you need lots of 10mm plate bent up?

Or design something that's easier to make.
Either use bits of ali extrusion you can buy, e.g. fabricate using angle and flat bar, or use thinner plate that you can bend, then reinforce if more strength is needed.
Two bits of 5mm flat bar bent in rightangles then riveted together to make your 10mm thick right angle will be much easier.

 

[Huggers]

Thirty years ago I made 25 mast steps from aluminium flat bar and welded each one using Lumiweld. The first step was tested to destruction and thus encouraged I made up the rest, installed them with ally rivets and beetled up and down the mast whenever I wanted. The steps are still going strong.
Google Lumiweld. Dead easy to use and cheap. No connection with whoever makes the stuff.

 

[C08]

Why not just use the steering connection already on the outboard?
I struggle to visualise the set up, it seems very complex to link the tiller of the outboard to the tillers of the cat.
Surely the forces are not so huge you need lots of 10mm plate bent up?

Thanks for suggestion, believe me I have tried to use "normal" outboard steering arrangements. My problem is that the outboard is in a recess at the back and the normal cable cannot cope with the vertical movement when the outboard is on full tilt to sail. I bought a "no feedback" steering system and it was fine steering up set for outboard down or outboard up but would not cope with both positions.
I am reconciled to getting it welded now.