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Thread: CR14 Frame Design

  1. #11
    Quote Originally Posted by kabhi View Post
    @Adam we have run the tests along with the forces as specified in rulebook. Doesn't it cover this scenario?
    Actually we are going to change harness bar this time. We are planning to make it bent and hence that needs to be triangulated.
    You're probably in line with the rule book. But in general when designing structural things, just picture where the loads go for various cases. You don't need to do analysis, just stare at it and think for a while.

    Ex: If there is a 20 G crash, then there will be ~3000 lb ~= 13kN pulling forward on the bar. If you triangulated the shoulder harness bar nodes then this would be borne in tension or compression to other nodes around the frame, but it's not, so all this force goes into bending the main roll hoop. You could use something like this to do some hand calculations:
    https://www.google.com/search?q=simp...90%3B798%3B474

    I guess my point was to ask why you have so much triangulation everywhere else but not here? What's the justification for triangulating everything else with such heavy tubes but not one of the safety-critical nodes? I assume that most of your "extra" nodes are for triangulating some suspension bracket or something. If I were you I would work on combining these together / using the "rule-required" nodes for these and eliminating excessive tubes.

    As for tube sizes, I'm pretty sure no teams that I know of go up in wall thickness to get tube manufacturing tolerance against the rule-spec'd wall thicknesses. Are your tubes actually that far out of tolerance? 10% is a lot, I'd expect wall thicknesses to be within 3% and for that to be acceptable at inspection. In my experience 4130 tubing from the German mills (Benteler, etc.) always satisfies this.
    Penn Electric Racing

  2. #12
    I typed out a response yesterday but it ate itself. I'll oblige a response tonight.
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  3. #13
    I don't have anything as constructive as what other's have mentioned, but please, please but your firewall in and a firesuit on when you test your car.
    Dalhousie University
    Halifax, NS, Canada
    -=-=-=-=-=-=-=-=-=-=-=-
    2012 to Present - Chassis (Frame, Suspension, Steering)

  4. #14
    Quote Originally Posted by Adam Farabaugh View Post
    As for tube sizes, I'm pretty sure no teams that I know of go up in wall thickness to get tube manufacturing tolerance against the rule-spec'd wall thicknesses. Are your tubes actually that far out of tolerance? 10% is a lot, I'd expect wall thicknesses to be within 3% and for that to be acceptable at inspection. In my experience 4130 tubing from the German mills (Benteler, etc.) always satisfies this.
    Here is the link to the thread i was talking about
    http://www.fsae.com/forums/showthrea...tuck-Australia
    read the comment of fixitmattman..

  5. #15
    @Brett MacPherson We give utmost importance to the safety of the driver. I have mentioned that car was in the "initial" phase, as you can see we were working on the wiring harness.
    I posted this pic so as to compare designed frame to actual frame of car.
    Last edited by kabhi; 09-29-2014 at 08:08 PM.

  6. #16
    Senior Member
    Join Date
    Nov 2010
    Location
    NSW, Australia
    Posts
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    kabhi, it appears that someone was driving the car? If that is the case, then no, you have not given utmost importance to safety. Brett is 100% right. The most common cause of real danger in these cars is fire.
    Jay

    UoW FSAE '07-'09

  7. #17
    The fact that you're a new team with an untested car, and inexperienced drivers mean the chances of something going wrong are very high. Giving the driver the utmost importance in safety means forcing them to wear a firesuit at all times, even if you're just puttering around a parking lot. If you're not so concerned with driver safety, then nothing will get your team shut down quicker than having a team member injured while you were being negligent.

    Now I think it's time for me to go back to lurking.
    Dalhousie University
    Halifax, NS, Canada
    -=-=-=-=-=-=-=-=-=-=-=-
    2012 to Present - Chassis (Frame, Suspension, Steering)

  8. #18
    Quote Originally Posted by Brett MacPherson View Post
    Giving the driver the utmost importance in safety means forcing them to wear a firesuit at all times, even if you're just puttering around a parking lot.
    I will definetely make sure of that next time.

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