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Last Post 12 Jun 2013 04:36 AM by  djsilver
ASP Sub Frame Connector
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Der Wankel
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--
06 Jun 2013 02:34 PM
    The rules state-

    E. Longitudinal (fore-aft) subframe connectors (SFCs) are permitted
    with the following restrictions:
    1. They must only connect previously unconnected boxed frame rails
    on unibody vehicles.
    2. Each SFC must attach at no more than three points on the uni-
    body (e.g., front, rear, and one point in between such as a seat
    mount brace or rocker box brace).
    3. SFCs must be bolted or welded, but welding must be to the OE
    subframe stampings, not to the floor pan in between.
    4. No cutting of OE subframes or floorpan stampings is permitted.
    Drilling is permitted for mounting bolts only.
    5. No cross-car/lateral/triangulated connections directly between the
    driver’s side and passenger’s side SFCs are permitted. Connec
    -tions to OE components such as tunnel braces or closure panels
    via bolts are allowed and count as the third point of attachment.
    No alteration to the OE components is permitted.
    6. SFCs may not be used to attach other components (including but
    not limited to torque arm front mounts or driveshaft loops) and
    may serve no other purpose.


    If I am reading that correctly, I can weld/bolt rails from my front to rear subframes that additionally bolt to one point to the unibody as well.

    The SFC wording always confused me because it states-

    1. They must only connect previously unconnected boxed frame rails
    on unibody vehicles.
    2. Each SFC must attach at no more than three points on the uni-body


    but then says-

    3. SFCs must be bolted or welded, but welding must be to the OE
    subframe stampings, not to the floor pan in between.


    It seems to me like the rules don't distinguish correctly between the uni-body which is one thing and the subframes which are another.

    I gather they want to allow you to connect with bolts front and rear boxed sections of the chassis using a SFC with one point allowed to a non boxed section in between while not crossing the center line of the uni-body.  Additionally, if the boxed section is a subframe which unbolts from the uni-body your connection may be a weld.

    Some one please correct me if I have interpreted that incorrectly.

    My question involve the three "points" of attachment.

    Are they allowing for instance a 4" weld to the subframe and only one bolt, or can a "point' of attachment be a bracket with multiple bolts?  Sure would be nice to be able to unbolt it and have the rigidity of the allowed weld.

    Anyone have insight?  I searched, but though I saw this question asked, I did not see an answer.
    kb_solo2
    Advanced Member
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    Posts:878


    --
    06 Jun 2013 09:29 PM
    Unless you have a fox body mustang this probably does not apply to you...
    Der Wankel
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    Posts:36


    --
    07 Jun 2013 05:04 AM
    Yes, big flexy American cars is what I have seen SFCs on commonly.

    You think there is no benefit to be had on a more rigid chassis?
    kb_solo2
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    Posts:878


    --
    07 Jun 2013 02:18 PM
    the allowance is for big flexy american cars, that is why you are having trouble figuring out how to apply it to your car.
    Der Wankel
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    --
    07 Jun 2013 04:57 PM

    Yes, I know the allowance was written to benefit racers of big flexy American cars.

    I believe I can legally implement the rule on my vehicle to some benefit as well.

    Recap- I was asking for a clarification on what a point of attachment is- whether one bolt or a bracket/gusset with multiple fasteners.

    I figured it out.  A point of attachment can include multiple fasteners just as a 2 point or 3 point strut bars may have more than 2 or 3 bolts holding them to the vehicle.  SFC states 3 points of attachment each side.

    kb_solo2
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    Posts:878


    --
    07 Jun 2013 06:47 PM
    Here is the big part...

    1. They must only connect previously unconnected boxed frame rails
    on unibody vehicles.

    Does you unibody car have unconnected boxed framerail sections?  a subframe is not a boxed framerail.

     

    Der Wankel
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    Posts:36


    --
    10 Jun 2013 12:38 PM

    Yes, several unconnected box frame rail sections on my car.

    I would be interested in connecting the front box rail sections the front subframe mounts to to the rear box rail sections the rear subframe mounts to.

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    Der Wankel
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    10 Jun 2013 12:45 PM

    Shown in Red is where someone used structural foam, but it does show the closed box rail sections well.

    Obviously, he foamed some sections I would consider unibody space frame (the front fender area above the wheels).

    I would consider connecting the front subframe box rail section (clearly seen) to the rear subframe box rail sections (harder to see, but diagonal from edge of unibody toward rear subframe front mounts.)

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    Der Wankel
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    --
    10 Jun 2013 12:57 PM
    Here without the front/rear subframes you can see the diagonal box frame rail sections in the rear.
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    Der Wankel
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    --
    10 Jun 2013 04:20 PM

    SFC would be something like this.

    I went ahead and showed some lower arm bars as well between the longitudinal link's and toe link's suspension pick up points on the rear subframe.

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    djsilver
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    Posts:187


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    11 Jun 2013 12:16 AM
    I'm not an FD expert but I believe the only thing that this rule applies to are the parts marked in red on the picture I attached.  The rules specificaly forbid triangulated devices.
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    Der Wankel
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    11 Jun 2013 04:23 AM

    I believe you are referring to this section of the SFC rule as it is the only place I see mention of triangulation.

    5. No cross-car/lateral/triangulated connections directly between the
    driver’s side and passenger’s side SFCs are permitted. Connec
    -tions to OE components such as tunnel braces or closure panels
    via bolts are allowed and count as the third point of attachment.
    No alteration to the OE components is permitted.

    That rule states no connections between the two sides SFCs.  It specifically allows the 3rd point of connection to be a tunnel brace.

    Longitudinal does not indicate only perfectly parallel.  I wish it did so I could replace my (angled) lonitudinal rear multilink suspension arms with aftermarket ones for wheel clearance.

     

     

    djsilver
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    Posts:187


    --
    11 Jun 2013 02:43 PM
    Posted By Der Wankel on 11 Jun 2013 04:23 AM

    I believe you are referring to this section of the SFC rule as it is the only place I see mention of triangulation.

    5. No cross-car/lateral/triangulated connections directly between the
    driver’s side and passenger’s side SFCs are permitted. Connec
    -tions to OE components such as tunnel braces or closure panels
    via bolts are allowed and count as the third point of attachment.
    No alteration to the OE components is permitted.

    That rule states no connections between the two sides SFCs.  It specifically allows the 3rd point of connection to be a tunnel brace.

    Longitudinal does not indicate only perfectly parallel.  I wish it did so I could replace my (angled) lonitudinal rear multilink suspension arms with aftermarket ones for wheel clearance.

     

     

    We agree on one thing; the rule is confusing both of us!  That said I have to start at #1

    "1.They must only connect previously unconnected boxed frame rails
     on unibody vehicles."    This sounds pretty simple until you read the rest.  My understanding is that the things I highlighted are the "boxed frame rails"

    "2.Each SFC must attach at no more than three points on the uni-
     body (e.g., front, rear, and one point in between such as a seat
     mount brace or rocker box brace)." This next section does seem to allow some triangulation, since it says the 3rd attachment point could be a rocker box brace.  I'm not sure what a "rocker box brace" is, but since the rocker panel is at the edge of the unibody, the 3 attachments can't be in line if the 3rd attachment is anywhere near the rocker panel.

    "3. SFCs must be bolted or welded, but welding must be to the OE
     subframe stampings, not to the floor pan in between."   This part doesn't seem too confusing, except that it appears the term "subframe stampings" has been substituted for "boxed frame rails".  Based on the language, I don't think they're talking about the welded "subframes" that are bolted to the unibody so support the engine/transmission/suspension.  

     "4. No cutting of OE subframes or floorpan stampings is permitted.
     Drilling is permitted for mounting bolts only."   This seems pretty simple if you agree with my interpretation of #3....,  They also say you can't cut it, (or drill holes in it until it disappears!)

    "5. No cross-car/lateral/triangulated connections directly between the
     driver’s side and passenger’s side SFCs are permitted. Connec
     -tions to OE components such as tunnel braces or closure panels
     via bolts are allowed and count as the third point of attachment. No alteration to the OE components is permitted."   This section seems to reinforce or expand the idea that the SFC can be triangulated, as long as it's not across the centerline of the vehicle.

    "6. SFCs may not be used to attach other components (including but
     not limited to torque arm front mounts or driveshaft loops) and
     may serve no other purpose."   This one seems to prohibit using the SFC to anchor two (non-unibody?) components together.  #5 seems to prohibit cross-car connections and this one would seem to me to prohibit using the SFC to connect your engine cradle to your rear suspension subframe.

    My confusion is in the inter-use of the "subframe" word.  My car is a  unibody design and it has boxed frame rails (already connected so I can't use this), boxed rocker panels and boxed seat rails.  It also has a rear "suspension subframe".  Yours also has a "front engine/suspension subframe"  I interpreted this rules to mean that you can connect "subframes" that consist of "boxed frame rails", but you can't use the SFC's to connect the front/rear "subframe assemblies" together.

     



    Der Wankel
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    Posts:36


    --
    11 Jun 2013 09:23 PM

    We agree on all points regarding the SFC rule, including the confusion on what they mean by "subframe".

    On further reflection I believe as you do that in this case (regardless of conficts of definition in other class rules) the term subframe and subframe stampings refers only to the box section "faux" frame rails found on unibody cars, not the units that bolt onto the unibody and carry the engine, suspension, steering rack, swaybars, etc.

    The only point that we disagree on is regarding my chassis, which I researched further and am confident I could defend completely in the case of a protest against my SFCs and I understand you are naturally not as familiar with.

    I looked through the Mazda parts schematics and color coded each piece according only to what Mazda has labeled it.  If the colored lines are contiguous the piece is one part # and label.

    Red Line =  Mazda calls all these and only these pieces "Frame"

    Blue Line= Mazda calls all these and only these pieces "Cross Member" (I was surprised the front engine/suspension cradle *Thin Blue Line*  is called this)

    Light Blue= Mazda calls all of these and only these pieces "Panel"

    Yellow= Mazda calls all of these and only these pieces "Reinforcement"

    Green= Mazda calls all of these and only these pieces "Strut bar"

    Thin White Line= Mazda calls this piece and only this piece "Sub frame"

    Orange/Brownish= Mazda calls all of these and only these pieces "Torque box"

    Dark Gray= Mazda calls all of these pieces and only these pieces "Junction"

    Light Gray= Mazda calls all of these pieces and only these pieces "Tunnel member"

    Original White graphics in picture= Mazda calls all of these pieces and only these pieces "Pan"

    My SFCs would connect only the front and rear (Red) box rail "Frame" sections though I am as close to the front engine cradle "Crossmember" and rear "Subframe" as possible.  My third point of attachment would be through the forward most allowed tunnel brace "Tunnel member".

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    djsilver
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    Posts:187


    --
    12 Jun 2013 04:36 AM

     

    Based on your findings I suspect this is as close as you'll get without drilling more holes.  This would connect the previously unconnected front and rear "boxed frame rails", and includes the allowed 3rd attachment point to the "tunnel member".  You may be able to get the forward attachments further forward by drilling new holes but I can't tell about "elevation changes" in the structure that may interfere.  The rear "boxed frame rail" is almost entirely obscured by the rear "subframe". 

     

     

     

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