Broken stearing tube

[gtluke]

The biggest reason why aluminum hasn't been used for chassis is it's so hard to work with. Welding is harder to do compared to the factory spot-welds done in the past. And it's nearly impossible to do a cheap/fast steel to aluminum fastening method. Like if you want to use aluminum frame rails but steel floors and bulkheads. Or ABC pillars made of steel but aluminum bulkheads, etc. Not to even mention galvanic corrosion. Plus aluminum has historically been expensive.

Much easier to make bolt-on parts that are heavy in steel out of aluminum to minimize weight. Crossmembers, suspension arms, door impact supports, etc. Body panels are actually hard as Aluminum is hard to stamp. Castings are much easier.

For this steerer tube, I'd want to see more close up pictures. It could have been a scratch on the tube 10 years ago from a loose & then spun stem creating a stress riser that took a long time to materialize.

-Steve

more difficult than fiberglass though?
now I can't remember but there was some car recently that had aluminum fenders that was recalled or problematic because after a few years the fenders actually develop big cracks in them. I want to say subaru, they have been using aluminum for the hoods for a while.
someone recently on jay leno's garage was explaining that the reason that all the 60's race cars were iconically round is because they had aluminum bodies. That the nature of aluminum is to be round, and that it's nearly impossible to get straight lines and flat panels with sheet aluminum. What came to mind was this is probably why the deloreon was stainless and not aluminum. This dude today couldn't get the body made out of aluminum because it had too many straight lines, nobody could do it but he said there were some craftsman in italy that may be able to do it.
It was this car:
http://www.kenokuyamadesign.com/oneoff/
i'm sure with production presses you could do it though. But man if you try to shape a flat seam in aluminum and take more than one try it's going to work harden and tear right off.

 

[Monkey Soup]

The BMW Z8

more difficult than fiberglass though?
now I can't remember but there was some car recently that had aluminum fenders that was recalled or problematic because after a few years the fenders actually develop big cracks in them. I want to say subaru, they have been using aluminum for the hoods for a while.
someone recently on jay leno's garage was explaining that the reason that all the 60's race cars were iconically round is because they had aluminum bodies. That the nature of aluminum is to be round, and that it's nearly impossible to get straight lines and flat panels with sheet aluminum. What came to mind was this is probably why the deloreon was stainless and not aluminum. This dude today couldn't get the body made out of aluminum because it had too many straight lines, nobody could do it but he said there were some craftsman in italy that may be able to do it.
It was this car:
http://www.kenokuyamadesign.com/oneoff/
i'm sure with production presses you could do it though. But man if you try to shape a flat seam in aluminum and take more than one try it's going to work harden and tear right off.

The BMW Z8 gave aluminum bad press in the early 2000's because the chassis is prone to warp, the strut towers develop cracks. Most high-end German cars today have aluminum hoods and fenders.

 

[Delish]

Yeah, Aluminum is terrible. Nobody would ever use it use it in critical repetitive stress applications in which failure due to fatigue would mean loss of human life...like say an airplane wing.

I'm going with stem over-tightened which caused the star nut to score the inside of aluminum steerer creating a stress riser right at the wrong place.

 

[gtluke]

Yeah, Aluminum is terrible. Nobody would ever use it use it in critical repetitive stress applications in which failure due to fatigue would mean loss of human life...like say an airplane wing.

I'm going with stem over-tightened which caused the star nut to score the inside of aluminum steerer creating a stress riser right at the wrong place.

well this is where advanced engineering and rigorous inspections comes into play, as there really is no other choice. Or wasn't until boeing switched to carbon fiber.
but what determines the lifespan of an airplane is metal fatigue of the body. @axcxnj spends his entire day making sure no cracks can possibly form in airplane castings. but there is no alternate material available. can they make carbon carbon turbines? that would be neat.
presumably we get all our better bicycle metals from aerospace.

 

[StayHydrated]

well this is where advanced engineering and rigorous inspections comes into play, as there really is no other choice. Or wasn't until boeing switched to carbon fiber.
but what determines the lifespan of an airplane is metal fatigue of the body. @axcxnj spends his entire day making sure no cracks can possibly form in airplane castings. but there is no alternate material available. can they make carbon carbon turbines? that would be neat.
presumably we get all our better bicycle metals from aerospace.

https://phys.org/news/2017-01-ceramic-matrix-composites-flight-jet.html

 

[gtluke]

https://phys.org/news/2017-01-ceramic-matrix-composites-flight-jet.html

Oh wow. Those stock photos though! Ha ha

 

[StayHydrated]

but what determines the lifespan of an airplane is metal fatigue of the body.

creating a stress riser right at the wrong place

Aluminum is AMAZING. Until it gets a boo-boo: http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=28&LLTypeID=2

I can post lots of math here, but you don't want that.

 

[StayHydrated]

Oh wow. Those stock photos though! Ha ha

Like most National Labs, Oak Ridge probably hasn't taken new photos in at least 15 years haha

 

[Magic]

Yeah, Aluminum is terrible. Nobody would ever use it use it in critical repetitive stress applications in which failure due to fatigue would mean loss of human life...like say an airplane wing.

I'm going with stem over-tightened which caused the star nut to score the inside of aluminum steerer creating a stress riser right at the wrong place.

This is why you are recommending me the aluminum version of your bike to watch me catastrophically OTB!? Lol.

 

[gtluke]

Like most National Labs, Oak Ridge probably hasn't taken new photos in at least 15 years haha

I work in a lot of government plants, those may have been taken last week.

 

[alex_k]

Aluminum is AMAZING. Until it gets a boo-boo: http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=28&LLTypeID=2

I can post lots of math here, but you don't want that.

basically that was cost of their "safe-life" design philosophy - stay with "fail-safe"!

http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=28&LLTypeID=10

 

[Delish]

This is why you are recommending me the aluminum version of your bike to watch me catastrophically OTB!? Lol.

Yes. I want to see you drop out of the Calcutta sky in a firey ball...figuratively speaking.

 

[Delish]

Aluminum is AMAZING. Until it gets a boo-boo: http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=28&LLTypeID=2

I can post lots of math here, but you don't want that.

Carbon fiber is also Amazing until it gets a boo-boo.

 

[Patrick]

Carbon fiber is also Amazing until it gets a boo-boo.

yup

 

[gtluke]

what material does a good job after it's damaged? not much. I guess steel but aside from a bike frame it seems like a poor choice for bicycle or airplane parts.

OH HAAAAY
Who know that in 1989 dodge sold a car with fiberglass wheels? F'ing awesome attempt!

 

[Rockbottom]

Is that dirt packed in the steerer tube attached to the stem? At first I thought it was the star nut but doesn't look like one I've ever seen before.

Speaking of star nuts, was it set to the correct depth? I would imagine a shallow setting on a star nut could play a factor.

That's the star nut you're seeing in the steering tube piece attached to the stem. I believe I set it at the right depth when I installed it into the steering tube. Can't remember the exact depth I placed it in to be honest. I even used that special tool to hammer it in evenly

 

[Santapez]

more difficult than fiberglass though?
now I can't remember but there was some car recently that had aluminum fenders that was recalled or problematic because after a few years the fenders actually develop big cracks in them. I want to say subaru, they have been using aluminum for the hoods for a while.
someone recently on jay leno's garage was explaining that the reason that all the 60's race cars were iconically round is because they had aluminum bodies. That the nature of aluminum is to be round, and that it's nearly impossible to get straight lines and flat panels with sheet aluminum. What came to mind was this is probably why the deloreon was stainless and not aluminum. This dude today couldn't get the body made out of aluminum because it had too many straight lines, nobody could do it but he said there were some craftsman in italy that may be able to do it.
It was this car:
http://www.kenokuyamadesign.com/oneoff/
i'm sure with production presses you could do it though. But man if you try to shape a flat seam in aluminum and take more than one try it's going to work harden and tear right off.

Aluminum was used for bodies as it was lightweight and easy to manipulate with cheap labor. It's hard to think about it now, but the fiberglass body on the Corvette was revolutionary and was thought to be far supreme to the aluminum bodies of it's competition with it's pre-flight-age aluminum. Aluminum body panels were typically made using english wheels or hammering on bucks, they weren't stamped. If you had a long flat hood you'd have to use a flat sheet of thick metal and that's even harder to stamp or work with.

Fiberglass is not really great chassis material. You have to lay the fibers out correctly to get the correct strength, and it's not really that lightweight, therefore you're using cloth not blown fibers. You need to have a lot of precision for fittings for screwing ancillary components in and any major joints like where suspension pieces mount to would be extremely thick. Carbon Fiber works very well, but it's labor intensive, expensive and nearly impossible to repair.

Fiberglass can either be cloth which is the common type used in production vehicles, or blown fibers which is used often in shitty kit kars. I would actually say the reason Corvettes went with fiberglass was it's probably easy to use for bodies in low production vehicles. Molds are EXPENSIVE. I'm pretty sure it was the DeLorean molds that were found to sold in the firesale as cargo ship anchors.

I'd bet the DeLorean went Stainless because it looks cool. Aluminum you can't leave bare while Stainless you can. If it's not bare, what's the point? Stainless doesn't have to be any heavier than regular steel, I don't think that's why the car was so heavy, I think it was a combo of shitty chassis and the safety features. Plus there's something about Stainless and the electrical charge that builds up with the use of a flux capacitor.

There's the Canadian DeLorean car which I can't remember the name of. Looked just like it, same time period. Pretty sure that was a fiberglass tub chassis now that I think about it...

 

[soundz]

 

[SmooveP]

Land Rovers had aluminum bodies going back to the very beginning in the 1940s and continued at least until the late 90s on Defenders and Discoveries. All Ford F-150 bodies have been aluminum since 2015. Lots of flat slabs of bodywork there.

 

[pete497]

Looks like it failed from bending. Pushing and pulling on the bars. The crack initiated under the stem clamp at the star nut. Its possible you over tightened the stem clamp. As you tightened the clamp the star nut was digging into the steer tube. Likely a fatigue initiated crack that broke through when you crashed. The challenge with designing with Al is that it has no fatigue limit. That is there is no stress level below which a crack will not initiate from fatigue ie repeated cyclic stress.