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Thread: Hubs with built-in tripod joint

  1. #21
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    Quote Originally Posted by BillCobb View Post
    Negative, Ghost Rider, the pattern is full. (Request for a fly-by to an Air Boss).
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  2. #22
    In the past, my team (s) built cars with steel (welded) uprights, off-the-shelf hubs, aluminum uprights and aluminum non-tripod-joint-built-in hubs.

    If I have to choose, I would choose aluminum uprights and aluminum hubs with built in tripod joints, just like OP did. But, I would improve design a little, although that is part of the process of becoming a better engineer: making mistakes.
    Daniel Schwind
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  3. #23
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    Z,

    1. LVHM – We must not be thinking of the same industries. An example for engine cooling. What I am referring to is making 100 units for each of 1,000 different engine cooling packages for a dozen different industries instead of 100,000 units of 1 engine cooling package for one automotive plant. The design and production processes for each are handled very differently.

    2. Z, you brought up comparing the proposed design to actual industry. Do not switch the conversation around.

    3. I did not pretend to have any more numbers than I actually had. It is easy to make up numbers to get whatever outcome you want (see below, though I do feel those are realistic estimates). You analysis is exactly as subjective and biased as mine, in fact my first post had more cost related numbers than yours.

    4. If you want to do this objectively I will happily compare cost estimation models.

    5. Your post script makes my point for me. You are comparing a mass produce product with one which is intended to be a one off. You could make paper clips in a job shop and you could build prototype cars on an assembly line. But neither would be a cost effective decision. I would encourage students to look at custom high end bicycles; that is a better comparison.

    Billet Aluminium Box Steel
    Material 75 Material 50
    Hr. $/hr Hr. $/hr
    CNC Maching 0.75 50 0.1 50
    Sheet Metal Cutting 0 50 0.1 50
    Welding 0 40 0.75 40
    Material Handling 0.1 25 0.5 25

    Engineering Cost 3 50 3 50
    Design Cost (Drawings) 1 40 2 40

    Total 305 333

    *Sorry if the table doesn't line up right.


    -William

  4. #24
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    William,

    Your analysis is exactly as subjective and biased as mine,...
    I gave NO analysis. Certainly nothing I would call an "objective numerical analysis".

    Instead, I suggested to the OP, Josh, that HE should do a much more objective analysis of his current design, and also of the many alternatives. I then gave him some hints (as did Goost) as to where he should look for the biggest Enduro-killing flaws in his current design, and how to fix those problems.

    I note that Josh is the one person here who seems to be taking those criticisms the best. He seems to be genuinely pleased to have any apparent weaknesses of his design pointed out, so he can make the necessary corrections before comp. (BTW, Josh, widen "toe-base" to at least 6". Easy via a channel-section bolted to upright and carrying the 2 x outer-BJs. Shims between channel and upright adjust camber-angle with no toe-change.)

    By comparison, many other people here seem have the mindset,
    "Yep, looks great. Go for it. It looks a lot like what we did, which turned out a bit crappy, but was good enough... Yeah, no point thinking too hard about it, just keep copying everyone else and hope you muddle through..."
    ~o0o~

    4. If you want to do this objectively I will happily compare cost estimation models.
    YES! This is what all Teams should be doing, so I give my version of your (Will's) Cost calcs here. (Changes emboldened.)

    UPRIGHT - ............ Billet-Aluminium .......... Folded-Sheet-Steel
    $Material - .............. $75 ................................. $10 (Steel is cheap, and strong...)
    $Processing (Hr. x $/hr)
    CNC Machining - .. 0.75 x 50 ...................... 0.10 x 50
    Sheet Cutting - ...... 0.00 x 50 ...................... 0.10 x 50
    Welding - ............... 0.00 x 40 ...................... 0.75 x 40
    Material Handling - 0.10 x 25 ...................... 0.40 x 25 (Slight rounding.)
    Engineering* - ....... 3.00 x 50 ...................... 3.00 x 50
    Drawings* - ........... 1.00 x 40 ...................... 1.00 x 40 (See note*.)
    TOTAL COST - ..... $305 .............................. $250

    * These Eng+Drawing Costs are "one-time", so are somewhat misleading in that they amortise over multiple units (eg. if all four of your uprights are identical). Here these one-time Costs are the same for both approaches, so make no difference.

    Except that saying that it "costs" $115 to make each Billet-Aluminium upright, and only $60 for each Folded-Steel one, is a more realistic comparison of their relative costs (ie. Steel is ~HALF $s of Billet).

    Also, everyone can argue about the exact size of all the numbers in above table, but the only way to really know is to carry out the various processes MANY, many times over. For example, more practice with welding makes you faster, but CNC times stay pretty much the same.

    More importantly, as per earlier post,
    ... the most important factor is reliability, which here includes fatigue-life and strength (because no-finish = no-points). Next in importance are things like stiffness (important for hub-assemblies), speed of manufacture, mass, and cost, with all of these having to be assessed very objectively with carefully estimated NUMBERS that reflect "point-scoreability".
    So "Cost" is only one factor that should be objectively assessed, with several other more important factors to be also considered for the overall "point-scoreability" of the various designs.

    By my reckoning good folded-steel designs can win ALL those assessments. Fortunately, this makes the final decision very easy. No subjective "judgement calls" needed.
    ~o0o~

    Your post script makes my point for me.
    ...
    I would encourage students to look at custom high end bicycles; that is a better comparison.
    Indeed, many high-end bicycles are exactly the sort of expensive-junk-sold-to-dimwits that I was getting at. Who honestly believes that a $50,000 titanium-plated, carbon-nanotube, funny-Italianish-named, bicycle will make them a THOUSAND times faster than if they are riding a $50 Chinese special? That sort of high-end fashion junk is no different to the $1,000(+++???) jeans that air-heads buy, that come with the knee and bum-holes already in them.

    Yes, there is a brain-dead market out there, and those fools should be separated from their money. But winning FSAE is NOT about making money in a fashion industry (well, maybe 10 points are allocated to such in Design Event). It is about engineering a reliable, and moderately fast, small car.

    Z
    Last edited by Z; 10-29-2015 at 11:21 PM.

  5. #25
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    Z, have you ever been able to concede a single point to anyone who was born after you?
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  6. #26
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    I don't have time to comment further right now, but one thing in that cost estimate really stands out to me-I want to know where you can get welding done for $40/hr. I was a power generation industry guy, but around here the job shops are $75+/hr. If TIG welded I figure 5 mins/inch weld which comes out to maybe 2 hrs of welding or $150 instead of $30. Maybe labor costs are much lower in other parts of the country/world.
    Jim
    "Old guy #1" at UCONN Racing

  7. #27
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    Z,

    Quote Originally Posted by Z View Post
    I gave NO analysis. Certainly nothing I would call an "objective numerical analysis".

    By my reckoning good folded-steel designs can win ALL those assessments. Fortunately, this makes the final decision very easy. No subjective "judgement calls" needed.
    Z
    So my qualitative analysis was not quantitative, and my quantitative analysis was not rigorous, but your “reckoning” constitutes a compelling argument?
    Well I remain uncompelled and stand by my analysis.
    I priced the material, I really doubt the uprights are identical, and the Folded Steel design needs more drawings (flat, folded, welded, machined).
    It is absurd to change the model assumptions to give your desired outcome and then claim it is more realistic.

    Bringing up performance will not convince anyone about the cost aspect.
    Nor will I be convinced by hyperbole* or veiled insults**.

    I contend that you offered an opinion (a VERY BAD DESIGN) and demanded objective analysis.
    When offered a qualitative analysis you demanded a quantitative analysis.
    When offered a quantitative analysis you changed the model assumptions.
    I have seen nothing to change my position.


    *(Who honestly believes …a THOUSAND times faster)
    **( crappy, fashion junk, air-heads)



    Josh,

    Yes, you need to do you own analysis.
    But I think you are on the right track.

    jd74914,

    Good eye.
    Those $/hr are estimate internal costs.
    To have them made outside I would also bump the CNC cost up as well.


    -William

  8. #28
    Quote Originally Posted by Z View Post

    YES! This is what all Teams should be doing, so I give my version of your (Will's) Cost calcs here. (Changes emboldened.)
    UPRIGHT - ............ Billet-Aluminium .......... Folded-Sheet-Steel
    $Material - .............. $75 ................................. $10 (Steel is cheap, and strong...)
    $Processing (Hr. x $/hr)
    CNC Machining - .. 0.75 x 50 ...................... 0.10 x 50
    Sheet Cutting - ...... 0.00 x 50 ...................... 0.10 x 50
    Welding - ............... 0.00 x 40 ...................... 0.75 x 40
    Material Handling - 0.10 x 25 ...................... 0.40 x 25 (Slight rounding.)
    Engineering* - ....... 3.00 x 50 ...................... 3.00 x 50
    Drawings* - ........... 1.00 x 40 ...................... 1.00 x 40 (See note*.)
    TOTAL COST - ..... $305 .............................. $250
    Z
    Having designed and manufactured both sheet steel and billet aluminum designs. I'll have to agree that billet is a reliable way to go. The dimensional control over bearing bores, ball joint positions, and other critical geometry is much better. The reduction in operations are nice from a competition stand point, less handling for things to go wrong. Also from a competition stand point, making an upright that is a "competitive weight" to what a student can easily have done from billet requires incredibly thin steel.

    Z, what do you think is a reasonable upright weight?

    I would also like to add some cost to your analysis of heat treating of the steel upright (most likely an out-job) and fixturing for both items if I'm to play along and assume that you're treating this as a real business endeavor.
    Looking up the material required for the uprights we produced, $56 dollars for 6061 aluminum and $22 for 4130 steel was required (resale cost for both) for each, so in the end, you're really breaking even based on that.

    But, aren't we supposed to be discussing the hub? Talk to me, Goose.


    From the current industry that I participate in, steel billet uprights are very much the norm. I really don't think there is any argument here beyond exaggerated bench racing where the pet concepts always win.
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  9. #29
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    MCoach,

    I really don't think there is any argument here beyond exaggerated bench racing where the pet concepts always win.
    So, given that you have "designed and manufactured both sheet steel and billet aluminum designs", why not present here your engineering analyses of the two? You know, with actual NUMBERS? Of comparative masses, ultimate strengths, stiffnesses, estimated MTBFs, etc?

    This lack of real engineering on this thread (and on the Forum generally) is getting boring. A comment like "From the current industry that I participate in, steel billet uprights are very much the norm." is NOT an engineering justification. Sheep think like that.

    Anyway, it seems that the majority of you young people are beyond help. Yes, you can keep swallowing the claptrap that your teachers have fed you, namely that any piss-poor job you do is worthy of yet another gold star. And then, when the wheels fall of your car mid-comp, you can all cheer "Yeay, more gold stars for us!".

    For those very few of you who are interested in using an engineering approach, I have done some more homework and the material cost of a sheet-steel 4130/40 upright is actually closer to $5. Material cost is even less for mild-steel. Both are much stronger and stiffer than an equal mass billet-aluminium upright of the "typical" design (like OPs).

    Yes, I have done the calculations! But I won't give you the other numbers here. Whenever I have done that in the past, everyone else shuts-up and the thread goes cold...

    Z

    (PS. I look forward to the honest billet-lovers out there being true to their beliefs, and "hogging-out" a full FSAE chassis from a single billet of 7075. Yep, ~2 tons at ~$20/kg = ~$40,000, plus some (!) machining time, so you should save a bundle over those damned expensive fabricated steel frames! )
    Last edited by Z; 11-01-2015 at 10:03 PM.

  10. #30
    Just because I can quip my 2 cents (2.8 AUS cents) of my experiences does not mean that I need to divulge my entire report on these. The pictures of the designs can freely be found online with some digging, do your own analysis from there.
    I think Josh's design is on the right track: holds the wheel on the car with at least one clamping device, allows the tire to spin, and allows some stopping device to transfer force to the tire. Seems to check those boxes.

    "A comment like 'From the current industry that I participate in, steel billet uprights are very much the norm.' is NOT an engineering justification. Sheep think like that."
    Is nothing more than a comment. It is not saying "Gokart Fun Rentals runs XYZ therefore we need to because it's obviously a good engineering decision!" Do not attack the straw man, he is only in Oz looking for a heart, I hear.
    I think OP's design could use a little weight. Then again, I know I was a little shy on giving away design details when he contacted me. I think the bobbin count could be reduced. I know I spent a long time fighting that point before moving concepts when previous leaders had been convinced that anything less than 8 brake bobbins would fail. Less bobbins --> less weight on the upright, reduced part count, less rotor weight. In terms of assembly...Josh, can the brake rotor be removed without pulling the hub from the upright?


    Being attacked for being reserved is getting boring. Being attacked for sharing is boring. Why does anyone bother to share when they are just going to get torn down and pulled apart at the seams for not building a steel barrel, powered by an air cooled motor, that is infinitely rigid, makes 3Gs of downforce at 0mph, and backed by volumes of online forum posts that decry anything but?



    Z, childish wars do not determine who is right, only who is left. That is why the threads go cold.
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
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