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Thread: Fatigue data for steel

  1. #1
    I'm doing a fatigue analysis for our rear sprocket for which I have considered 4130, 4140 and 4340 steel grades. The steel suppliers do not have any fatigue data and since this is our first year we too don't have any testing data. I need a reliable source for the SN curves of the above grades although I'm aware they'll just give me a rough idea of fatigue life.

    I found a military handbook online:
    http://www.knovel.com/web/port...L_DISPLAY_bookid=754
    “Being second is to be the first of the ones who lose" - Ayrton Senna

  2. #2
    I'm doing a fatigue analysis for our rear sprocket for which I have considered 4130, 4140 and 4340 steel grades. The steel suppliers do not have any fatigue data and since this is our first year we too don't have any testing data. I need a reliable source for the SN curves of the above grades although I'm aware they'll just give me a rough idea of fatigue life.

    I found a military handbook online:
    http://www.knovel.com/web/port...L_DISPLAY_bookid=754
    “Being second is to be the first of the ones who lose" - Ayrton Senna

  3. #3
    Senior Member
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    I'm doing mostly electrics and data for my team and can't help you with a source of fatigue data, but I know our rear sprocket is made of Aluminium and has gone through a heap of testing and two comps just fine. I don't know what grade it is or anything like that, but is there any reason you're looking at steel over aluminium. Seems like it'd be unnecessarily adding weight?

  4. #4
    We use stock, off the shelf motorbike sprockets, made of aluminium. I think we get a new one each year, but they don't cost a lot.
    Rex Chan
    MUR Motorsports (The University of Melbourne)
    2009 - 2012: Engine team and MoTeC Data acquisition+wiring+sensors
    2013 - 2014: Engine team alumni and FSAE-A/FStotal fb page admin/contributer

    r.chan|||murmotorsports.com
    rexnathanchan|||gmail.com
    0407684620

  5. #5
    The 4xxx series has better fatigue properties and can be as light as an Al-7075 sprocket if designed nicely. Plus we're finding Al costlier.
    “Being second is to be the first of the ones who lose" - Ayrton Senna

  6. #6
    I recommend any edition of Shigley's mechanical engineering design. It will have everything you need to do a good fatigue analysis.

    To be honest though, SN curves can only get you so far. You may need to consider how you are going to distribute the force from the chain across the teeth of the sprocket?

    My advice would be to just buy a sprocket. It will be cheaper than the stock 7075 AL to machine one and by far the easiest. If you can't do that then just design something that looks reasonably stiff and make it from alloy steel. Your not going to shed a rediculous amount of weight from your sprocket by doing FEA or other such nonsense. Just make sure your mounting bolts can support the torque and away you go!
    Western Formula Racing
    The University of Western Ontario
    Alumnus

    "If I had one hour to save the world, I would spend 55 minutes defining the problem and only five minutes finding the solution." –Einstein, Albert

  7. #7
    For whatever reason, U Waterloo has an online fatigue database that is publicly accessible.

    Haven't used it yet, or even looked at it in detail, but it is what it is.
    University of Waterloo Formula Motorsports Alumni
    http://www.uwfsae.ca/

  8. #8
    Senior Member
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    Location
    Oxfordshire
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    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by nvpF1crazy:
    The 4xxx series has better fatigue properties and can be as light as an Al-7075 sprocket if designed nicely. Plus we're finding Al costlier. </div></BLOCKQUOTE>

    I think you are going to have a really hard time matching the weight of a well designed AL sprocket. Yes it's more expensive than steel, but a 12" x 12" plate of 7075-T651 cost under $50 and you wont need to deal with heat treatment.
    Chris Patton
    Vehicle Dynamics
    Global Formula Racing '10-'12
    OSU Beaver Racing '05-'09

  9. #9
    The FAA MMPDS (METALLIC MATERIALS PROPERTIES DEVELOPMENT AND STANDARDIZATION) is what you want. Every team should have this. Download it.
    http://www.everyspec.com/FAA/F...DS-01-JAN2003_24102/

    It's the Bible of metallic material data for any stuff that FSAE teams use.
    _______________________
    "It doesn't get easier, you just go faster." - Greg Lemond

    Nick Renold
    Northwestern Formula Racing - Suspension Lead '11

  10. #10
    Call either Rebel Gears or Sprocket Specialists. Quick and easy with turnaround times of less than a week. They also do custom sprockets too.

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