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Thread: When are Chassis Stiffeners Needed ????

  1. #1
    Registered Member Run-em's Avatar
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    Question When are Chassis Stiffeners Needed ????

    At what point are chassis stiffeners needed --such as the Art Morrison --- to enhance the capabilities of the original frames?

    Tires & wheels?---going larger adds stress to frame?
    Better brakes--disc brakes?
    More horse power and torque?
    Dropping the frame/body height?
    Greater transmission torque capabilities---more gears & multiplication???

  2. #2
    Registered Member chevynut's Avatar
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    That's a really good question run-em. I don't have a clear answer, and don't know if there is one. The stock frames give pretty good longitudinal stiffness, but have poor torsional stiffness. Even adding straight crossmembers doesn't help much, because it can still twist like a ladder. You really need an AME type crossmember or a large X. This is more important on hardtops than sedans too, since sedan bodies are stiffer than hardtops. I think the wagons would be more like the sedans as well. Clearly more horsepower and traction are going to cause the frame to twist more. Driving an autocross hard around corners is going to cause the frame to twist more. I don't think just lowering the car would have any effect on it, though. I don't see how brakes would have much effect either, if any.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


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    Registered Member NickP's Avatar
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    Building blocks. In this instance, using the criteria you have presented in your post I would say that if your intent is to use the added HP, take advantage of the tires and desiring an overall improvement, then it will complement what you have listed. If the intent is otherwise and bragging rights are the end results, certainly it will accomplish that task too. Done well, it's a nice addition. Just plan it out so the execution is flawless. If I can help, let me know neighbor.. I loaded a pic of what we did to Geoff's. As an alternative and to eliminate the rear cross brace, pictured is another way of doing it.
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    Last edited by NickP; 03-28-2012 at 07:34 PM. Reason: Options

  4. #4
    Registered Member chevynut's Avatar
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    NCW, those look pretty nice. I thought the elimination of the cross-brace was interesting, but it seems harder to implement to me. I've done about 4 of those AME crossmembers now, and cutting the openings for the exhaust on the diagonal is a real PITA. It's a lot easier straight on, as you probably know. But the u-bend is a lot of work too, so I do like the idea.

    That looks like one of your new frame designs...how close are you to production?

    One other issue with the AME-type of crossmember is that it restricts what you can do with your exhaust quite a bit. We line up the header collectors, and determine where the front openings should be, then pick a muffler and determine where the rear openings should be. Typically we use an offset muffler to keep the outlets close to the center of the C4 differential. You only have about 11" in width for a muffler too. So some larger mufflers won't fit. You're also limited on fore-aft placement.

    Attached are pics of some we built.
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    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

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    Registered Member NickP's Avatar
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    It was a chalange at first. It took a while to jig up in the mill, but I purchased a right angle drive that gave me the flexability I needed and it makes it easy. Laszlo I am very close to releasing this chassis. I have gone through a lot of parts and fabs to get it where it is now. The AutoCad Inventor has been a reall good addition to my design ability - I have a ways to go on some of the features of the software, but it really answers a lot of questions and saves fab misques. About two more weeks and I should be able to publish the results here - FIRST! I really am excited about it! Thanks for asking.

  6. #6
    Registered Member NickP's Avatar
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    Quote Originally Posted by Blown_Shoebox View Post
    Are you planning to run C4 suspension or something less in your car?
    I am guessing this was addressed to me - yes, all new rails, coilovers, and C4.

  7. #7
    Registered Member chevynut's Avatar
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    Graeme, don't know why you think you can't run full-length headers with the AME frame stiffener kit. This is a 502 with full-length headers in one of our frames. You just have to plan the openings correctly.
    Attached Images Attached Images
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  8. #8
    Registered Member WagonCrazy's Avatar
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    Quote Originally Posted by Run-em View Post
    At what point are chassis stiffeners needed --such as the Art Morrison --- to enhance the capabilities of the original frames?

    Tires & wheels?---going larger adds stress to frame?
    Better brakes--disc brakes?
    More horse power and torque?
    Dropping the frame/body height?
    Greater transmission torque capabilities---more gears & multiplication???
    Experience with my 9 passenger wagon tells me that the reason for all the body mounting points is to use the body to stiffen the whole package. The frame alone is not very strong. As ChevyNut mentions, it bends like a ladder would if you put a twist on it. I've experienced that with driving my wagon over uneven driveways, etc. You can hear the whole thing twisting, albeit ever so slightly.

    In my opinion, the mods you mentioned in your post don't require a stiffer frame...but driving a 3500 pound tri-5 hard thru corners and uneven surfaced will reveal the flex in the frame. So the frame needs to be stiffened up more to reduce or eliminate that. The weight of the car on the stock frame creates a sag. Ever seen it when you jack up the front end on one or the other frame drop down points? (just behind the front wheels). The whole thing flexes a good 1/2 inch from the dead weight of the engine hanging. That same thing happens when you're driving down the road and hitting bumps, etc.

    Go with a cross member setup to reduce this. This is what i had ChevyNut do on my Nomad frame when he did the C4 conversion. Bought the AME center brace kit and had him weld it all in. Stiff as a board now...(but it's not in drivable condition so I've yet to actually compare the ride with my stock frame 9 passenger wagon).

    DSCN1211.jpgDSCN1215.jpg

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