Splines on Titanium

[rjwoods77]

I am designing a jackshaft for my car(using cvt) and I have the dimensions set and the spline set. I am now looking at material options. I dont want to have to post heat treat the shaft because of the very laborious post machining process, especially with the splines, so I was looking into using 4340,300M,1144 or EDT 150. But then I was thinking about titanium as well because for about the same cost I could get a bar from titanium joe. So this leads me to the questions:

-Are splines in Ti bad news? I know it is notch
sensitive an all but....

-Will a steel sprocket gall the shit out of the splines? If so should I make a Ti sprocket to go with the Ti shaft? Will the chain gall the shit out of the sprocket then?

[BeaverGuy]

Last year we used titanium half shafts on our car. We were told by the company that cuts our splines for us that splining titanium was not a good idea because of galling. So instead we threaded splined steel end pieces into the titanium. Everything seems to be standing up to our abuse so far.

[Denny Trimble]

Threads? So I'm guessing you didn't have inboard rear brakes...

How much weight did you save over a hollow 4340 shaft like the Taylors (.750 OD / .400 ID)?

[BeaverGuy]

I'm not sure about the difference in weight. But I believe they decided to use the Taylor shafts this year.

[Underthefloor]

We didn't realy save any weight using titanium. If the plans had been followed each axle would have weighed about the same as the taylors. I think that they didn't turn down the titanium as much as they should have last year so they are even heavier than in the model. The 17in long axle model in proe weighs 1lb 12.2oz.

[Underthefloor]

I think that they could be made quite a bit thinner. The guy that got us the titanium used to build driveshafts for race boats. He said that Ti splines would be risky.

[Foote]

I know everyone thinks that titanium is really cool stuff, but it's really just heavy and hard to machine. If you are trying to cut your own axles or splines, i would highly recoomend not going with ti. It is the hardest stuff you will ever work with, but at the same time it is the gummiest. It will take you forever and you will probably break many tools.
In addition to being stupid hard to work with, it not very much lighter. unless you make thin wall, large diameter driveshafts, i think you won't really see any advantage.
I suppose these are just my opinions, but once you've run through all your tools, don't say i didn't warn you.

[rjwoods77]

Foote,

Not getting on you or anything but just want to clarify a couple things for you. Ti isnt heavy. Its .19 lb/in^3. Cutting Ti isnt hard. You just need the right inserts and the correct feeds and speeds. It cuts very much like stainless. If you ever had a tough time with it, most likely your tools sucked, your machine sucked or who ever machined it sucked. I've worked at a machine shop for 4 years and we cut Ti from time to time. You have to be a little nore careful with it than stainless but it really isnt that bad. Gets a bad rep from people who dont use modern tooling and modern machine practices. You can see plenty of advantages with Ti. It just can be very expensive and it is impact/notch sensitive.

[James Waltman]

Justin is kind of a wimp. We made titanium front spindles on our last car. It can be machined without too much drama. Though I'll admit that I don't have much experience with it myself.

Our spindles from the last car (ti on the left).
http://dot.etec.wwu.edu/fsae/images/Stub%20alxes%20in%20Titanium%20and%20Aluminum_JPG. jpg

You should look into sinusoidal splines. We have been using them for a long time and I'm a big fan. It makes it easy to drive aluminum parts with steel parts. I think it could be done in titanium without too much trouble.
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/Assembly.JPG
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/CV_joint.JPG
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/Hub.JPG
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/cv_joints.JPG

[rjwoods77]

Jimmy,

Those are nice. I am asking about splines for the primary sprocket. Dont have much space to play with.

[rjwoods77]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Rob Woods:
Jimmy,

Those are nice. I am asking about splines for the primary sprocket. Dont have much space to play with. Those are a rounded 5 tapered 5 star right. 3+ insert cutter and increasing interpolation for about 15 steps? <HR></BLOCKQUOTE>

[jack]

shear modulus's (psi):

cold rolled steel: 11.5e6

stainless steel: 10.6e6

heat treated steel: 11-11.9e6

titanium: 5.8-6.2e6

..just thought i would throw this out there...