VIP
South East
Posts: 8,293
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Unfortunately that isn't necessarily the case with the alloys used in alloy wheels. You really need to know what's in the metal before you start welding, which can be tricky! It is exactly the case, Getting the weld rite is the skill once done and correct it is stronger than the parent materiel. However every time you create a welded joint you get a week point either side of the weld so original material thickness is important. Well done, point well and truly missed...
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Usedabused, the point Adam was trying to make is that without knowing what metal the wheels are made from you can't know what filler rod to use when welding them, or if they need pre-heating or any other special treatment. Combine this with the fact most alloys are made from low grade cast aluminium that will contain aeration and contaminating impurity, and it's a genuine issue. Also a strong weld bead's no use if it's not stuck to the metal either side of it. Besides which it's not always true that the weld's stronger when dealing with TIG welding, if an exactly matching filler rod is used then the weld will be the same strength as the area around it assuming they cooled at a similar rate after welding. There's also the consideration that even if the weld does end up stronger, then a ring of harder material in the wheel will cause an uneven distribution of strain when it's under load, which can lead to premature fatigue around the welds. It's not quite as simple as the weld always being stronger and that always being a good thing unfortunately.
This would all go towards explaining why the wheels above appear to mostly be forged or spun, and not cast. It's not to say it's impossible, clearly it's not, it's been done many times, with great success, and considering most wheels are hugely over-engineered anyway, there's a pretty decent margin for error in most cases.
I'm no expert on these matters, but from what I've picked up from being around people who are handy with a TIG, that's what I could gather of things anyway.
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Banded alloysDeleted
@Deleted
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i would agree totally with the above post, we use an aluminium MIG welder at work and it makes it seem easy as anything to stick ally together, but the wire is available in a mind boggling series of grades all relating to different compositions of aluminium and alloys, I think the control panel has what must be heading for 20 or more pre-programmed settings on it all relating to different materials.. you wouldnt catch me welding alloy wheels far too risky unless you had the manufacturers data to hand on composition etc
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Got a bit more time to explain.
The problem with cast wheels is knowing exactly what's in it. High silica content alloys are used because they flow in the casting better, but when welded the silica solidifies before the surrounding metal, causing brittle areas in the weld. Methods used to correct this can be unreliable.
The problem with forged, spun or billet wheels is that they are often made of aged and heat treated alloys (6xxx series usually), then machined / cold forged. Your weld/HAE is going to be circa 60% weaker for a given cross section than the metal you are welding.
Thats not saying it can't be done, but you have to know about the metal you're working with.
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Last Edit: Nov 8, 2011 18:42:20 GMT by Adam
1997 TVR Chimaera 2009 Westfield Megabusa
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Got a bit more time to explain. The problem with cast wheels is knowing exactly what's in it. High silica content alloys are used because they flow in the casting better, but when welded the silica solidifies before the surrounding metal, causing brittle areas in the weld. Methods used to correct this can be unreliable. The problem with forged, spun or billet wheels is that they are often made of aged and heat treated alloys (6xxx series usually), then machined / cold forged. Your weld/HAE is going to be circa 60% weaker for a given cross section than the metal you are welding. Thats not saying it can't be done, but you have to know about the metal you're working with. I did actually mean to mention heat treating in my post, but managed to forget, but yeah, that's another very good point, and a better explanation of the issues with welding cast.
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So that means pop rivets and filler, then?
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Click picture for more
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On an episode of 'Custom My Ride' (yes, I know ) they had some custom wheels made up to their design, and according to the wheel bloke once they'd made up the centres they just heated the 'hoop', dropped the centre in, and that was it. No welding, no bolts, nothing. Just an interference fit. Is that possible, or, have they just left a big chunk of the manufacturing process off the telly?
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" East bound and down, loaded up and truckin' "
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So that means pop rivets and filler, then? Nah. Plain ol' duct tape...
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On an episode of 'Custom My Ride' (yes, I know ) they had some custom wheels made up to their design, and according to the wheel bloke once they'd made up the centres they just heated the 'hoop', dropped the centre in, and that was it. No welding, no bolts, nothing. Just an interference fit. Is that possible, or, have they just left a big chunk of the manufacturing process off the telly? Yep, that's absolutely true....but done in a way that's a LOT safer than you're imagining it
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Banded alloysRobinxr4i
@robinxr4i
Club Retro Rides Member 143
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You just use Chemical Metal right? Says on the packet fills anything, sorted!
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Sierra - here we go again! He has an illness, it's not his fault.
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damask
Part of things
Posts: 163
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theres a quick bit showing them milling and asembling the wheels as the other guys said, putting the centres in heated hoops, on this one, they're welding them, but on american hotrod it shows the heating/shrinking method, i just cant find a video
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An interference fit is incredibly strong if done right. A job I did a couple of weeks back involved rebuilding a couple of gigantic turbos. The alloy compressor wheels were about 18" diameter and were mounted onto about a 4" steel shaft. No keyways, no spline and no tapers... just interference. These things run at about 18,000 rpm and shift a huge volume of air (outlet is over 8" diameter!). Getting them off was hard going and they grab onto the shaft the second you drop them back on as they cool so rapidly on contact.
I would think on an alloy rim you could engineer a pretty tight interference fit as the potential expansion of the hoop when heated is huge.
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1962 Datsun Bluebird Estate - 1971 Datsun 510 SSS - 1976 Datsun 710 SSS - 1981 Dodge van - 1985 Nissan Cherry Europe GTi - 1988 Nissan Prairie - 1990 Hyundai Pony Pickup - 1992 Mazda MX5
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Gray
Part of things
Silence isnt golden!!!
Posts: 742
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Could it be done..... yes Could it be relied on..... absolutely not Would i do it?.... show wheels maybe but not for use why?..... composition of the alloy, to likely to crack, no matter what anyone says
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Nov 11, 2011 13:26:41 GMT
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Got a bit more time to explain. The problem with cast wheels is knowing exactly what's in it. High silica content alloys are used because they flow in the casting better, but when welded the silica solidifies before the surrounding metal, causing brittle areas in the weld. Methods used to correct this can be unreliable. The problem with forged, spun or billet wheels is that they are often made of aged and heat treated alloys (6xxx series usually), then machined / cold forged. Your weld/HAE is going to be circa 60% weaker for a given cross section than the metal you are welding. That's not saying it can't be done, but you have to know about the metal you're working with. Yep you are totally correct I I am a total gobshite and stand totally corrected.................. ** ( Sculks off and stands in the corner kicking stones all embarrassed )
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