[cyberax]

When the USSR collapsed, a lot of defense companies pivoted to civilian production. A factory in my town was producing titanium shovel heads.

They were awesome, unbelievably light, but very durable. They also made nice sparks when dragged across concrete pavement.

[myself248]

Decades ago, Sears sold magnesium stepladders. I've used one, and it's freakishly light, a 6-foot step ladder that you can walk around with balanced on one finger.

I've always wondered what a titanium one would be like.

[petertodd]

A lot heavier actually.

In an application like a stepladder, you have to work with certain minimum dimensions for the stepladder to be practical (eg rungs and sides have to fit in the hands nicely). You also have to have certain minimum thicknesses on the parts to have sufficient resistance to local deformation (eg dropping a hammer on the rungs). That forces the parts to be significantly larger and stronger than they otherwise would be. Which makes very lightweight metals like magnesium and aluminum the better choice, as you can make thick parts at the required dimensions at very little weight.

Climbing gear is a great example of this. Even though there's a segment of that market for which money is no object, the only use for titanium in climbing gear is certain specialized applications where corrosion resistance is important. Eg fixed gear mounted on sea-side cliffs. Because climbing gear has to have certain minimum dimensions to avoid damaging ropes, the very low density of aluminum wins over titanium's higher density/higher strength.

If you made a carabiner out of titanium it'd be stronger than necessary, and a lot heavier.

[TylerE]

This is also why aircraft use aluminum, despite the major downsides (finite fatigue life, mainly). There’s just no way steel would work (far too heavy). Titanium is awesome but a royal pain to work with. Carbon fiber is starting to come in but it has issues to - although they’ll be overcome with time.

[dredmorbius]

The Soviet Mikoyan-Gurevich MiG-25 was manufactured principally from stainless steel.

The result was a stunningly fast fighter aircraft, capable of Mach 3.2, though in practice engine overheating restricted operation maximum to Mach 2.83 (3,000 km/h), and even that for only 5 minutes at a time as the airframe and fuel would overheat. The MiG-25's mass necessitated huge wings (and overall dimensions), and limited maneuverability. Steel however provided better thermal-tolerance capabilities than aluminium, and lower cost and easier fabrication than titanium.

First flight 1964, introduced to active service in 1970.

That said, the aircraft is notable as an exception to your generally-applicable rule.

<https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-25>

I suspect carbon fibre would also have thermal limitations for high-speed aircraft.

[sufficer]

This aircraft also sparked development of the F15 which was superior to anything soviet for 10+ years

[vGPU]

Sure but the f15 didn’t start production until almost a decade later.

[j_apes]

Steel structure won't be necessarily heavier cause density and strength are almost thrice as much as aluminium ? I think the issue with steel is that it for the required strength, the structure would be too thin that it would buckle under compression much sooner.

[scheme271]

Titanium also doesn't have the resistance to abrasion that other metals have. There's stories of titanium bike frames being ruined because the rear tire was mounted incorrectly and ended up rubbing on the frame during a ride.

[londons_explore]

If you can 3D print titanium, then you can make a honeycomb structure overcoming this problem.

[bch]

What is the response to stress by this build method? Will it fail gracefully over a lifetime of stresses? Any single big stress-event?

In terms of (rigid, diamond-frame) bicycles, this is why I’m still firmly in the steel camp. No aluminium, no carbon; just steel. It really does have an excellent combination of nice ride quality, low weight, high strength, good failure mode (I’ve broken a few frames, and they tend to just bend/sag, vs the rapid unscheduled disassembling of carbon/Al).

[londons_explore]

I can't comment on the plasticity of titanium.

But complex microstructures can be designed to have non-sudden failures. Eg. you could ensure that a visible crack appears at 0.75x the ultimate strength, yet doesn't fail till 1.0x the strength.

You can also design structures so that a 'crack' is either 1mm wide or not there at all (ie. no hairline cracks).

such features of microstructures are not free though - you will lose strength/weight to get them.

[lmm]

> In terms of (rigid, diamond-frame) bicycles, this is why I’m still firmly in the steel camp. No aluminium, no carbon; just steel. It really does have an excellent combination of nice ride quality, low weight, high strength, good failure mode (I’ve broken a few frames, and they tend to just bend/sag, vs the rapid unscheduled disassembling of carbon/Al).

Bicycles don't have the minimum size problem GGP is talking about. Titanium is pretty much the perfect frame material (if you can afford it) - all the nice things you list (a bit stiffer than steel, but ride quality is still decent), but substantially lighter.

[jdietrich]

>Bicycles don't have the minimum size problem GGP is talking about.

They do, in a slightly different way. Bicycle frames are (broadly) stiffness-critical structures. Wider-diameter tubes have a higher specific stiffness because of the increased moment of inertia - that's why we use structures like tubes and I-beams instead of solid bars. Steel frames have skinny tubes, because they're limited by the minimum wall thickness of the tubing; increase the diameter too much and you have a tube that is very vulnerable to dents and very prone to buckling. Steel racing frames of the 1970s are remarkably flimsy, because framebuilders were pushing wall thickness to the absolute limit.

Aluminium bicycle frames are only lighter because the lower density allows you to retain an acceptable wall thickness on larger-diameter tubes. An aluminium frame with the same tube diameters as a steel frame would be considerably heavier than the steel frame, because an aluminium frame needs to be overbuilt to compensate for the lack of a defined fatigue limit.

All common steel alloys have essentially the same stiffness (~207GPa), but higher-strength steels allow us to use wider-diameter tubes with thinner wall sections; incidentally, this is why it's quite pointless to use an expensive tubeset in a lugged frame. CFRP obviously has immense specific stiffness, but it also allows frame designers to really optimise the geometry and use the material more efficiently.

Titanium is a really nice frame material, but it does have some significant issues in practical use. Titanium is very prone to embrittlement if there is any amount of contamination in the weld. Most framebuilders aren't capable of maintaining the level of cleanliness and the comprehensive gas purging required to produce really good welds in titanium, so it's very common to see titanium frames eventually crack around the welds.

To my mind the perfect material for a non-sporting frame was the superb Reynolds 953 maraging steel, but unfortunately it is no longer available. Reynolds 931 and KVA MS2 are still very good materials, particularly when fillet brazed rather than welded. CFRP obviously wins out in terms of pure performance, but I'm not sure that I'd ever trust an old and battle-scarred carbon frame on a hard descent.

[bch]

> Bicycles don't have the minimum size problem GGP is talking about

Good point.

> Titanium is pretty much the perfect frame material[…]

Anecdotally - I understand it’s tougher to work with at about every single step. I’ve seen too many cracked Ti bikes/parts to sign up, I think. I understand the lust though.

[PakG1]

Coincidentally, you can. https://www.sciencedirect.com/science/article/abs/pii/S00260...

[tako]

NI think AI assisted development needs comments to make better informed decisions about the code Needed to accomplish the task.

[BobaFloutist]

Can you 3D print metals yet? That sounds quite difficult.

[mhb]

Prototyping - Metal 3D Printing - Dan Gelbart

https://youtu.be/nyYcomX7Lus?si=E-B5VkFeX9W0Twc4

[smazga]

Sort of! https://thevirtualfoundry.com

Not directly extruding it, but the end result is metal.

[jabl]

> Decades ago, Sears sold magnesium stepladders. I've used one, and it's freakishly light, a 6-foot step ladder that you can walk around with balanced on one finger.

As a slight aside, magnesium is also a very interesting material. It might be we're on the cusp of a major expansion in magnesium usage due to recent advancements

- Mining from seawater (about 1 kg Mg in 1000L of seawater), or existing brine tailings from other extraction activities. With cheap solar electricity this might drive the cost down considerably (below the extremely dirty production methods being used today in China), providing carbon-emission free production of essentially unlimited amounts.

- thixomolding, a die-casting / injection molding-like process where the material isn't completely melted (thixotropic state), producing parts with much less porosity than traditional die casting.

- New alloys that are less prone to fires and corrosion.

For slightly more details, see https://www.youtube.com/watch?v=OIv_Rfl0L_A

[speed_spread]

Magnesium from mine tailings https://anrweb.vt.gov/PubDocs/DEC/GEO/TechReports/VGTR1998-1...

[justinator]

I had to do a double take on your "about 1 kg Mg in 1000L of seawater" stat, thinking it was for titanium, rather than magnesium.

For those curious, titanium is present in sea water, at 1 ppb! (magnesium is 1300 ppm)

[SV_BubbleTime]

Aluminum and magnesium are lighter than titanium at the same strength.

The idea is you can use less titanium in the application you would use aluminum, but this has limits. If your ladder was .200” wall thickness, you might in theory get away with a .070” titanium for the same weight, but you start running into mechanical stresses or assembly issues or manufacturing.

Titanium is useful when you need internal volume - most recently as an example by Apple. Aluminum was fine, but had thick walls. Steel allowed thinner was but was heavier. Titanium allowed for thin walls and more internal volume, but at a higher cost.

Basically, if you don’t have a size limit, aluminum is great! But most things have size limits, and titanium allows you to trade size for cost.

[Skunkleton]

The iPhone 15 pro is mostly aluminum. There is about a 1mm thick band of titanium around an aluminum frame.

https://www.apple.com/newsroom/2023/09/apple-unveils-iphone-... https://www.youtube.com/watch?v=S_W73ouKtjU&t=605s

[SV_BubbleTime]

And that makes perfect sense.

Thick walls on the iPhone are what are going to prevent X Y area which I suspect they need more than thickness.

[Skunkleton]

Seems like marketing to me. They got rid of the stainless steel frame from previous models, switched back to aluminum, then added a pointless band of titanium so they could say Titanium in their marketing.

[dreamcompiler]

Magnesium stepladders are great until one catches on fire because you try to weld something onto it or get it too close to a welding torch. Then things get spicy.

[postmodest]

Plus: doesn't magnesium oxidize more readily than other metals? I would worry that grandpa's magnesium ladder is a death trap.

[AlotOfReading]

Bulk metals are extremely difficult to ignite and magnesium in particular forms a very strong passivation layer on the surface as soon as it touches the air. Unless you're doing wildly inappropriate things like welding on it (tip: don't do this with any ladders, regardless of material), it's fine.

[cyberax]

Huh. Now I want to buy a magnesium ladder and set it on fire.

[dreamcompiler]

If you do, take it out into the middle of nowhere first because you won't be able to put the fire out (unless you bring a Class D extinguisher--good luck finding one of those at your nearby hardware store). Don't put water on it because that just makes it burn hotter.

[hef19898]

Damn, imagine having a titanium shovel! I want one!

[avs733]

https://nearzero.co/products/shovel

They exist! Meant for backpacking/back country work.

I spent a summer as a wilderness search and rescue intern/volunteer/grunt/mule during college and was shocked at how much weight could have been saved with better gear. There’s just a minimal market for it.

[amluto]

That company sells titanium pots, too. And they say “ Titanium leaves no metallic smell or taste.”

I don’t believe it. Titanium is, mechanically, a great material for a lightweight pot, but in my limited testing, I don’t think it’s inert enough. Green tea in a titanium pot is especially nasty.

[WillAdams]

This is actually a plot point in H. Beam Piper's _Little Fuzzy_:

https://www.gutenberg.org/ebooks/18137

the audiobook read by Tabithat is just about professional quality and is highly recommended:

https://librivox.org/little-fuzzy-by-h-beam-piper/

[OfSanguineFire]

In the backpacking and bicycle-travel community, titanium pots are widely regarded as good only for boiling water in, since they don't distribute heat as well as aluminium for more complex cooking.

[amluto]

I’m well aware, but I don’t really believe this :). As far as I can tell, no very thin pot or pan distributes heat well [0], and no very thin pan cleans up well from cooked-on food when the cleaning supplies at hand while backpacking.

[0] Concretely, this means that, when cooking solid food, the parts of the pan where the food isn’t sinking heat adequately get too hot.

[OfSanguineFire]

The non-stick aluminium pans from MSR, and perhaps other brands, do clean up well from food after cooking. In my experience (hundreds of nights of cooking while cycling the world), it is enough to wipe them clean with a dedicated towel or wet-wipe in order to pack them, and then they can be washed completely the next time one reaches a convenient water source.

[therein]

I had similar experiences with titanium cookware. Could it be acting as a catalyst to something that would otherwise not happen?

[amluto]

I don’t know.

My current favorite cooking surface is the coating used on Hestan Nanobond. It’s sold as “titanium” but, from reading the patent, I think it’s a bunch of layers of CrN, TiN, and AlN, applied by PVD in a process optimized to produce an attractive gray color that looks a bit like metallic titanium. It seems very hard, very durable, and does not obviously react with any kind of food. (And even if it did, unless something oxidized the Cr to +6 and made it soluble, nothing that might leach out seems likely to be harmful.)

The patent seems to expire fairly soon, and maybe the process will take off. I wonder if this coating could be applied to a lightweight titanium pot with good results.

[tuatoru]

Oh, there's a market for lightweight backpacking gear, all right! Check out Backpacking Light for in-depth reviews.

Garage Grown Gear has some of the trendy light and ultralight stuff.

1. https://backpackinglight.com/

2. https://www.garagegrowngear.com/

[saiya-jin]

Mountaineering ice screws. Its a dream for pro alpinists, since you have to drag every gram up there in thin air, so focus on weight saving is extreme, ie drilling holes into aluminum spoons before 8000m expeditions was normal in 70s-80s in eastern Europe block. Normal stainless steel ones are much heavier.