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Thread: Bellcranks

  1. #1
    Hey guys,

    I've recently been given the project of designing the bellcranks for our car for the 2006 competition. Last year, we got our bellcranks CNCed out of aluminum but they still required machining once we got them because the CNC couldn't cut on one side. So after talking to my suspension leader he mentioned that there were possibly other ways of doing it. Like CNCing two pieces of aluminum and using adhesive to put them together to make one bellcrank and avoid the extra machining. He also mentioned that we could make it out of steel sheet metal just welded togeterh and have the bellcrank hollow in the centre.

    I was just hoping you guys could point me to some good information or give me some of your past experience with the subject.

    Thanks for your time,

    -Tim Yeung

  2. #2
    Hey guys,

    I've recently been given the project of designing the bellcranks for our car for the 2006 competition. Last year, we got our bellcranks CNCed out of aluminum but they still required machining once we got them because the CNC couldn't cut on one side. So after talking to my suspension leader he mentioned that there were possibly other ways of doing it. Like CNCing two pieces of aluminum and using adhesive to put them together to make one bellcrank and avoid the extra machining. He also mentioned that we could make it out of steel sheet metal just welded togeterh and have the bellcrank hollow in the centre.

    I was just hoping you guys could point me to some good information or give me some of your past experience with the subject.

    Thanks for your time,

    -Tim Yeung

  3. #3
    Our bellcranks this year were paper-thin and separate plates, out of aluminum. They weren't connected together, except by the four bolts for all the connections. No problems.

    http://students.washington.edu/auto/photo_galleries/200...uild%20Pic%2016.html
    Alumni, University of Washington
    Structural / Mechanical Engineer, Blue Origin

  4. #4
    Our team pretty much did the same thing as Washington. This will work fine when mounting the thing in double shear. However our fronts were in single shear and needed to be one piece.
    ----
    Mike Cook
    It's an engineering competition, not an over-engineering competition!

  5. #5
    Bonding is definitely an option, but you have to really pay attention to how you do it. You want to avoid peel at all costs, tapered lap joints are a good option, thats how this upright was done:

    http://dot.etec.wwu.edu/fsae/v35/bonding/pages/Upright%...%20at%20once_JPG.htm


    I wouldn't bank on a bonded part being simpler, and there may not really be much of a need for it on a bell crank. I'd listen to Denny and Mike, two piece bellcranks seem to work very well, and they are dirt simple to make.

    If you do want to do a bonded part, I'd be happy to share what experience I have doing bonded parts...

    -Travis Garrison
    University of Washington FSAE
    UW FSAE 05-06
    WWU FSAE 02-04

  6. #6
    We did two piece CNC aluminum front and rear originally. They are both in single shear also and work just dandy. However the fronts ended up interfering with the shocks, so I made three piece steel parts. Super simple machining, easy to assemble and weld. Made them both in a day after waiting 7 weeks for the CNC'd ones. The pics of the front are pre-lightening via the grinder. Took off about 2 oz per bellcrank and they were still way overkill.

    Front:
    https://webspace.utexas.edu/ca61483/...r/DSC00445.JPG
    Rear:
    https://webspace.utexas.edu/ca61483/...r/DSC00444.JPG

  7. #7
    We do a 3 peice welded bellcrank. It's basically 2 pieces of sheet steel and a bearing housing we make on the lathe. Then all three are just welded together. It's a really simple process we normally give to our freshman to do. We used to do the whole machined aluminum, but the steel is just as light, stronger and much much easier to make.


    *EDIT* We also mount the bellcranks in single shear and have never had a problem with them.

    you can see one of them here, just under the vise grips. http://www.rfr.rutgers.edu/gallery/B...52/DSCF3580%20(Large).htm

  8. #8
    you should get a slot cutter for your cnc.
    bob mai - yofa42@hotmail.com
    u of manitoba design lead

  9. #9
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Agent4573:
    We do a 3 peice welded bellcrank.

    you can see one of them here, just under the vise grips. http://www.rfr.rutgers.edu/gallery/B...52/DSCF3580%20(Large).htm </div></BLOCKQUOTE>

    Went through the whole gallery -- kudus to your exhaust fabricator, that's really nice work. Also, extra style and originality points for using a sawzall as a tirechanger

    Cheers, Ted

  10. #10
    Hey Denny,

    After going over some ideas with my suspension leader, we were a little confused as to how you can constrain your bearing from moving between the two plates without having the piece constraining it rubbing on the two plates.

    Thanks a bunch,

    Tim

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