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 Post subject: Titanium frame?
PostPosted: Thu Nov 01, 2007 12:52 am 
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I know it's not exactly Locost, but in the future the price of this uber expensive alloy may come down. I know nothing about titanium alloys other than I have rode Ti bikes that were pretty amazing. They were as light as Al but dampened vibrations like steel. It was the best of both worlds.

I'm not actually considering making a Ti frame as much as I'm just curious what it would cost and if it is even do-able for a garage builder like myself. There are vendors out there who sell Ti tube and welding rod so it is in theory possible. I wonder how thin you could go and how much weight you could shave off a chassis. It probably wouldn't even be worth it. Anyone here ever do any Ti fabrication?

Anyway, I'm just fishing for information and educational discussion. :)

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 Post subject: Re: Titanium frame?
PostPosted: Thu Nov 01, 2007 1:02 am 
chetcpo wrote:
I know it's not exactly Locost, but in the future the price of this uber expensive alloy may come down. I know nothing about titanium alloys other than I have rode Ti bikes that were pretty amazing. They were as light as Al but dampened vibrations like steel. It was the best of both worlds.

I'm not actually considering making a Ti frame as much as I'm just curious what it would cost and if it is even do-able for a garage builder like myself. There are vendors out there who sell Ti tube and welding rod so it is in theory possible. I wonder how thin you could go and how much weight you could shave off a chassis. It probably wouldn't even be worth it. Anyone here ever do any Ti fabrication?

Anyway, I'm just fishing for information and educational discussion. :)


Welding Titanium requires an inert atmosphere, far more than just shielding gas from a TIG. In the late eighties, the Soviets built an attack submarine with a titanium hull, it was capable of good speed and very deep dives. For a long time the US was concerned that they had made some breakthrough with welding Titanium that we didn't understand since we had no way of matching a complete titanium hull. Then they found out that the Soviet built a hermetically sealed hangar big enough to weld the hull and had it completely filled with Argon. The welders worked in essentially space suits.

So, if you want to hermetically seal your garage so you can weld up your frame, TIG can handle it.


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PostPosted: Thu Nov 01, 2007 6:40 am 
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The other issue with Ti is the fact it catches fire. The grinding bits can burn very easily. I used to do x-ray service at a plce that made Ti blades for turbine engines and there were special fire extinguishers EVERYWHERE! When doing to finish work on the blades it wasn't uncommon for the filings to catch fire. Not a good idea for your garage.

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 Post subject:
PostPosted: Thu Nov 01, 2007 9:56 am 
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Had to laugh at the timing of this thread. I'm machining Ti threaded bushing now and have finally got it to where its "reliable". Gummy, abrasive, won't shear, seams to work harden. Nasty, nasty, nasty but with the right feed/speed/TOOL GEOMETRY not impossible to turn/drill/tap/bore.


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 Post subject:
PostPosted: Thu Nov 01, 2007 10:51 am 
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jmanz6 wrote:
The other issue with Ti is the fact it catches fire. The grinding bits can burn very easily. I used to do x-ray service at a plce that made Ti blades for turbine engines and there were special fire extinguishers EVERYWHERE! When doing to finish work on the blades it wasn't uncommon for the filings to catch fire. Not a good idea for your garage.


Titanium? Are you sure you don't mean Magnesium?

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 Post subject:
PostPosted: Thu Nov 01, 2007 10:59 am 
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Location: MTL, QC, CA
KB58 wrote:
jmanz6 wrote:
The other issue with Ti is the fact it catches fire. The grinding bits can burn very easily. I used to do x-ray service at a plce that made Ti blades for turbine engines and there were special fire extinguishers EVERYWHERE! When doing to finish work on the blades it wasn't uncommon for the filings to catch fire. Not a good idea for your garage.


Titanium? Are you sure you don't mean Magnesium?


It's a common property of metal. I mean oxidation ("rusting") is exothermic. So depending on the rate it can produce flame. Now, rate of oxidation is proportionnal to the surface area and depend on the specific metal. When turn into dust the surface area is increased. Or so it goes...

-S.


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 Post subject:
PostPosted: Thu Nov 01, 2007 11:03 am 
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I grind on Titanium parts every now and then in my line of work and I've yet to set any on fire. The fragments that come off the grinder however will burn like a sparkler until they burn up. I may shut off the lights and put some Ti to the grinding wheel and film it for you. It's a pretty cool light show.

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 Post subject:
PostPosted: Thu Nov 01, 2007 11:17 am 
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I've heard the guys on the finish line talk about fires being started from the filings if they build up too much on the floor. There are signs everywhere warning of fire hazards with Ti and about keeping the filings cleaned up. They even have special fire exstinguishers for Ti fires. Scary thing is all the Ti dust in the air in this place. True it's not as flamable as Magnesium but it's still dangerous.

On another note, I can't even fathom the cost of building a Ti frame. When I went to onlinemetals.com to get a small piece for a project I had thought of I about crapped myself at the cost of a 1' section of 1" dia rod. It was over $250!! Holy crap!

How about the Magnesium engine blocks that BMW is working on? No iron sleeve, ALL Magnesium. It's cool as all get out!! AND it doesn't catch fire.

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 Post subject:
PostPosted: Thu Nov 01, 2007 11:30 am 
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a good analogue of magnesium and titanium would be gasoline and diesel

magnesium like gasoline catches fire and burns easily, titanium on the other hand like diesel, is harder to ignite, but when it does burns hotter.

I used to have my pyrotechnic licence (really big fireworks) the lodest and brightest effect was the "Titanium Salute" intense bright white light and a concussion that would knock the wind out of you, if you were to near.


ever seen thermite in action, aluminum powder mixed with equal parts rust. once it starts burning, it will not stop untill its all used up, it will burn right through a iron engine block.

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PostPosted: Thu Nov 01, 2007 12:54 pm 
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violentblue wrote:
ever seen thermite in action, aluminum powder mixed with equal parts rust. once it starts burning, it will not stop untill its all used up, it will burn right through a iron engine block.



Yes Mythbusters 8) That stuff is crazy!

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 Post subject:
PostPosted: Thu Nov 01, 2007 4:58 pm 
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I used to do lots of Titanium sheet fab work on helicopter engine baffles. I cant exactly remember the grade we were using, it was an alpha alloy, but we spot welded it or riveted using monel rivets as per the manufacturers repair manual. As for working with it, big bend radiuses like aluminum, and file the edges to a machined like surface to reduce stress risers. Protect your hands to, those slivers are nasty. I remember my hands were always healing from cuts. A few guys attempted to spot weld ti to a large stainless exhaust shroud. They never did a grind test, Stainless grinds yellow, ti has a brilliant white spark. The patch pretty much fell off with little persuasion. They ended up replacing the spot welds with rivets, made for an ugly repair, but it was OK'ed by the manufacturer. The main use for Ti in a/c is hight heat applications, I havent seen it much in primary structure on the civil a/c Ive worked on.

I do recall reading about a certain motorcycle racing team that built the next seasons race bike out of titanium. They pretty much copied the design and replaced the previous metal with ti. The new bikes frame was plenty strong and much lighter but lacked rigidity of the previous bike, effectively taking one step fwd and two steps back. I guess the same would apply to the locost chassis if someone were to make it out of ti, a major redesign would be required.

Andrew


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 Post subject:
PostPosted: Thu Nov 01, 2007 5:56 pm 
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A lot of times topics like this are brought up simply because it's something different. You're right, building a chassis from a new material requires a complete reexamination of the material's properties. It wouldn't surprise me that Ti might be inappropriate, which tends to get hidden by the utter coolness of it.

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 Post subject:
PostPosted: Thu Nov 01, 2007 9:55 pm 
airframefixer wrote:
The main use for Ti in a/c is hight heat applications, I havent seen it much in primary structure on the civil a/c Ive worked on.

Andrew


The F22 has a titanium backbone and bulkheads. But then again, it isn't exactly a civil aircraft...


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 Post subject:
PostPosted: Thu Nov 01, 2007 9:57 pm 
Read up on T-45 mild steel. It approaches the strength of chr-mo, but weighs more like Ti. F1 uses for steel applications where Ti is either too expensive or not strong enough.

The T-45 welds like mild steel and from everything I've researched, does not need to be stressed relieved like 4130. If you really want to get fancy, the French make a stronger/lighter version of T-45, but I forget the name of it.

I researched this quite a bit because I considered building a single cylider, self designed, naked bike out of the stuff. The only problem is that I could never find it in the US. It's mostly in the UK, DE or FR. It wouldn't cost too much to have enough shiped to build a bike. But a car, on the other hand...

--Chris


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 Post subject:
PostPosted: Tue Nov 06, 2007 9:49 am 
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chrisf wrote:
Read up on T-45 mild steel. It approaches the strength of chr-mo, but weighs more like Ti. F1 uses for steel applications where Ti is either too expensive or not strong enough.

The T-45 welds like mild steel and from everything I've researched, does not need to be stressed relieved like 4130. If you really want to get fancy, the French make a stronger/lighter version of T-45, but I forget the name of it.

I researched this quite a bit because I considered building a single cylider, self designed, naked bike out of the stuff. The only problem is that I could never find it in the US. It's mostly in the UK, DE or FR. It wouldn't cost too much to have enough shiped to build a bike. But a car, on the other hand...

--Chris


T45 is a bit stronger than 4130 but that is it (4130 is 650 n/mm2 UTS, while T45 is 700, but yield is 620 vs. 520 for 4130)... it is steel after all and not lighter by any means (weight/volume..)
the wonder steel youare talking about is probably 15CDV6 / 1.7734.5 which is 980 N/mm2 with 790 N/mm2 yield... nice stuff, if you can afford the price - approx 50 euros per metre of 30x1.5 mm seamless tube.... this is what WRC cages are made of nowdays...


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