gerblefranklin said:*Sweet! I get it! 🙂
Thanks for all this info. Did you derive this information from the
links I gave you?
*
Yup. First year engineering schools stuff. It's called Mechanics of
Materials. You're math is probably good enough already for you to read
a textbook on this topic. If you run into anything you don't understand
one of your math or physics teachers can help.
Quoted message said:*
I plan on making a few steel hunters exactly like the original, and
then trying one out of titanuim. One hitch I'm runnign into is that
the person who runs the shop I may be using says her shop isn't set up
to do titanuim. She says I need a vacuum chamber for some forms of
titanium. But on the other hand, I talked to Steve Howard, and he says
that I can TIG titanium just as I would steel.
*
Steve is going to be a MUCH better source of information on metalworking
than I am. Aerospace engineers just come up with the design
specifications. We don't actually know how those specifications are
turned into parts.
Titanium LOVES oxygen, so your shop person wasn't far off. But Steve is
right - the inert gas displaces all the air and allows the molten
titanium to stay a metal instead of burning into an oxide.
One of my engineering 101 professors explained the reactivity of
different metals in this way. He said, "A freshly cut surface of steel
will oxidize in a few days or weeks, and will keep oxidizing until the
steel is gone. Freshly cut aluminum oxidizes in a seconds or minutes
but the oxide coating is so tight that it stops the reaction. Titanium
is the same way, but it forms the oxide coating in a few milliseconds."
It's safe to say that no one ever really sees freshly cut titanium, and
that molten titanium will react furiously with air if you ever give it
the chance.
The Russians built a couple of subs out of titanium during the cold war.
No one was sure exactly how they did it. It turns out they built the
subs in a giant airtight building filled with argon. All the workers
wore space suits.
Quoted message said:*
Now, assuming I'm still going to make a titanium hunter-like frame,
can you tell me how much larger diameter the tubes need to be? I
originally said 50", but would 25% work? I'd still like to keep the
tubing small.
Also, do you know of anywhere I can get the materials for a titanium
frame?
*
I'll have to get back to you on that. My sense is that 25% would be
fine, but you are going to be limited by whatever tubing size you can
find.
You might call Lightspeed or some other titanium bicycle frame
manufacturer and ask them where you can get materials. They might find
your project amusing and offer some help.
Quoted message said:* Steve Howard said I would need brand new High-speed steel end mills
for the bearing holders, and I assume this applies to the brake
bosses. He said that they'd be worn out pretty quickly. Also, where do
I get grade 5 titanium? I doubt I can just drop by the scrap yard and
pick some up.
*
Steve is telling you something quite valuable. Titanium is reactive,
right? Very reactive? Those top-end cutting tools are going to get
dull very, very fast because the titanium will weld itself to the
cutting edges as it is being cut. Those welds will round the edges of
the tools in no time, either because tiny titanium blobs will coat the
edge, or more likely the titanium will pull chips of steel off the
edges.
Steve is also cluing you in on the possibility that you may need to
spend a lot more money on tools than you will on materials. What Steve
is saying is don't waste your time with cheap tools because they will
become useless almost instantly. The really good stuff will cut
titanium for a minute or so before it goes dull.
The machinists who worked on the SR-71 (a mostly titanium aircraft) used
to go through a truckload of tools just to get one assembly built.
There are a couple of processes that have been invented for working
titanium without welding or cutting. It's so reactive that if you just
get two parts hot and press them together they will diffuse into each
other and be virtually welded without ever melting. Titanium also has
this neat property that it will slowly flow or into a new shape if you
get it hot and apply enough pressure. I think the process is called
superplastic forming. If it's not too hard to do perhaps you could make
the bearing holders this way by "mushing" them on to a 40 mm steel form.
It might be cheaper than buying a few sets of cutting bits.
So to recap, I know just enough about making things to be dangerous.
Listen to Steve. He's a pro.
--
cyberbellum - Level 1.0 rider!
I was standing in the park wondering why frisbees get bigger as they get
closer. Then it hit me.
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