My 1970 Mustang project - Frame/Floorpan/Subframes.

Discussion in 'Classic Mustang Specific Tech' started by BlackGMC, Feb 19, 2007.


  1. 351w_swap

    351w_swap New Member

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    I used 14 ga. tubing in and effort to find a balance between weight and strength. I think I got it right because I can grab the bar between the back of the rear frame rails and lift up the car with very little if any flex. I did not put plate, just a some sheet of the same thickness because the old sheet was rusted out where the crossmember met the rocker. The reason i didnt put a plate was because I am building a full frame car and supporting the body off of it while I believe from the pictures that you are stiffening the existing structure. Then again the plate idea wasn't completely lost on me, here is a pic where the crossmember meets the rocker.

    This is an older picture but it does the job.
    [​IMG]
    #41
  2. BlackGMC

    BlackGMC New Member

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    Very nice!!
    #42
  3. RacerX

    RacerX Founding Member

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    BlackGMC & 351w_swap,

    How low have you located your rear crossmembers? I've tentatively located mine with the bottom of the crossmember even with the bottom of the rocker flanges.

    351w_swap,

    I'd like to see more pictures of your's

    Both these projects look great.
    #43
  4. BlackGMC

    BlackGMC New Member

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    Take a look at these pics.

    This is the mounting plate that attaches directly to the rocker panel, around the leaf spring mount. It is located about 1/2 inch above the bottom of the rocker panel.
    [​IMG]

    The end of the cross member is only about ~3 - ~3.5 (I don't remember the exact measurements) inches tall, cause I tampered it down for ground clearances.

    [​IMG]

    The top of the crossmember is level with the top of the leaf spring mount. So basically the crossmember is mounted 3 inches from the backside of the leaf spring mount, at the same height. Hopefully that helps...
    #44
  5. 351w_swap

    351w_swap New Member

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    I used the bottom of the rocker flange, I almost wish I could have put it lower though because it is going to really limit my suspension travel. My photobucket site is http://s161.photobucket.com/albums/t206/sweet_65/ you can go there, those are all my pics at the moment, i need to sell some parts so i can buy some parts, until then, i dont have enough money to do much.
    #45
  6. RacerX

    RacerX Founding Member

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    Thanks guys

    I'm looking at going with a CWI or Heidts IRS so suspension movement isn't so critical. I started cutting into mine this past weekend since the weather broke. I was thinking of selling off some parts also, particularly those I won't be using, so I could afford to do all the fabrication work.
    #46
  7. BlackGMC

    BlackGMC New Member

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    The saga continues. Well today I got the passenger side floor pan out!!! I was so rusted I did not even have to drill the spot welds, not to mention help with the SawZaw!!!



    Good news the inside of the front subframe is exactly 2.5 x 2.5. That means I can run a 2.5 x 2.5 square box up inside of it and run it back to the rear crossmember like I had hoped. The top of the new subframe will intersect the rear crossmember about 2 inches from the bottom of the rear cross member. So like I had figured the new subframe will only extend about 1/2 below the rear crossmember. I will probably tapper the end up so if fits nicely. Not to mention the base of the front subframe is perfectly level with the rest of the car. So I run the custom floor pans right on top of it. I amd still trying to figure out how I am going to run the rocker panel kickers and the driveshaft tunnel kickers and bracing, but that can wait a little bit. Exciting day when all the planning actually works out.



    Anyways hear are the pics.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    #47
  8. BlackGMC

    BlackGMC New Member

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    Well I thought I would post up an update/plan for my subframes, with some good luck I should be able to start on them this weekend. I am still riping out the old floor pans. The passenger side is 95% ready and the driver side is about 80% ready. I should finish by the weekend. I requested a quote today for all the steel I will need. The plans are below.

    [​IMG]

    The main subrame connect into the front subframe and runs all the way back to the rear crossmember. It is 2 1/2 X 2 1/2 1/8 steel box. It is about 4.5 ft long. Basically it runs up the front crossmember about 1.5 feet. The way i have it planned the cross member will mount directly to the bottom of the floor pan, so it will not be seen inside the car. Then the runners off of the subframe connects are 1 1/2 X 1 1/2 1/8 steel box. They will attach to the rocker panel via a 5 X 1/8 steel plate. The support for the tunnel will be an arched 1 1/2 X 1/8 bend. The lines in blue are the basic shape of the new seat platfroms which will be made out of 1 1/2 x 1/8 steel bars, these are going to be a B**** due to the angles and everything, but I taken a ton of measurements and have good plans now. I thought I would never use geometry again, but it surfaced.

    The floorpans themselves with be made out of 18or20 gauge steel with beads rolled in them.



    Let me know what you think?
    #48
  9. 351w_swap

    351w_swap New Member

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    have you thought about using bigger tube with thinner walls? By using bigger tube with thinner walls, you will eliminate a part of the weight while getting more structural rigidity. Just a thought but 1/8 steel seems kind of thick for the tube and especially for the seat pans. I would buy a bead roller if I were you. Then you could make the floor pans and seat pans stronger than the 1/8 and substantially lighter. The only probem with using bigger steel tube is that you may lose some ground clearance but in some cases, this wont matter.
    #49
  10. BlackGMC

    BlackGMC New Member

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    For the subframe connectors I choose 2.5X2.5 because it is the exact demension of the inside of the front frame rail. I really dont want to use anything thinner on that piece.

    I do have a bead roller and I plan on making the floor pans using ~18-20 gauge with beads rolled in them. The rest of the tubing is not that big 1.5X1.5 max plus some flat bars that are only 1/8 thick. I need the flat bars going over the tunnel to be 1/8 so I can bend some sheetmetal over them without them moving or changing shape.
    #50
  11. lauras70mach1

    lauras70mach1 Member

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    #51
  12. BlackGMC

    BlackGMC New Member

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    Thanks for the link! Yeah that is kinda what I am going for, but I am just supplementing the existing stuff. The only thing I don't like about that setup is that the subframe extends into the floorboard. I have seen a couple like that when I was researching this whole project. The way I am planning on doing it, the subframes will not extend into the floorboard, they will be flush with it. The only way I was able to do this was to make custom floorpans. But from my measurements and calculations I will still have the same ground clearance (hopefully).

    Keep the comments and Ideas coming guys, I really appreciate everyones input.
    #52
  13. mattrod70

    mattrod70 New Member

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    #53
  14. BlackGMC

    BlackGMC New Member

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    IMO, nope, they are still a chevy dominated company..... crapola
    #54
  15. BlackGMC

    BlackGMC New Member

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    Well I have some progress pics. I had a little bit of a problem fitting in the subframe connector, it seems that 2.5x2.5 is actually about 1/8 bigger than what it claims to be, so there was alot of grinding and pounding with the hammer to it the piece to fit and I still have another side to do. It all lined up like it is supposed to so that was a good thing, the top of the subframe connector will be flush with the new floor pans. I still need to finish boxing in the rest of the front subrame but I might tackle that tomorrow. Anyways just welding in this side seems to make the body/frame a whole lot stronger and move as 1 piece. The whole body now moves as one, it is kinda hard to explain but hammer on the body no is totally different. If there is anyone out without subframe connectors I highly suggest purchasing some.

    [​IMG]
    [​IMG]
    #55
  16. mattrod70

    mattrod70 New Member

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    looks real good, don'tcha hate when the size is not the actual size, just an industry standard size?

    are you gonna bead roll some steel for custom floor plans? and are you gonna do a custom tunnel or are you keeping the original one?

    matt
    #56
  17. BlackGMC

    BlackGMC New Member

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    Yep, I am going to make some custom floorpans from scratch! I was able to get a really good bead roller on sale a few weeks ago. Yep the old tunnel will be cut out and a new one will be made. Since I will be going with a T56 (6 speed) I have read that you need to modify the factory tunnel, so I will just remake it. The only reason it is still there is to serve as a guide.
    #57
  18. BlackGMC

    BlackGMC New Member

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    I made some good progress today, but I ran out of wire so I had to cut things short today. I finished up the drivers side sub frame connector. It also took some pounding and grinding to fit.

    [​IMG]

    [​IMG]

    I started working on the subframe to rocker bracing today, I was not able to finish because I ran out of wire, but you can kinda see the overall shape. I still need to box in both sides. I am going to make 3 more (2 for each side). These are what my new seat platforms are going to sit on, so my seats will be tied directly into the frame.

    [​IMG]

    [​IMG]
    #58
  19. BlackGMC

    BlackGMC New Member

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    1 down 3 to go.

    [​IMG]

    [​IMG]
    #59
  20. 351w_swap

    351w_swap New Member

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    I like those replacement seat pans, looks like a lot of work though. Guess when i get to that point ill have a real decision to make. I was just going use some 1 inch diameter 14 ga wall tube to make the new seat pans out of, i figured it wouldnt be too much work and might go with the theme of the crossmember. Anyways, nice job, I like the way that they are boxed.
    #60

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