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Technical Model A Subrail Fab

Discussion in 'Traditional Hot Rods' started by brianf31, Oct 18, 2017.

  1. brianf31
    Joined: Aug 11, 2003
    Posts: 659

    brianf31
    Member

    The subrails on my '31 coupe rotted long ago and were replaced with some roughly hewn angle iron. I need to fix that but since the car is channeled over a wide frame, I can't bring myself to buy and chop up a $350 set of new subrails.
    The most complex and visible shape, of course, is in the door openings. Has anyone come up with a novel method of fabricating their own? I searched but couldn't find. I'm thinking brake press sheet with notch/bend/weld/grind to get the correct curvature. Pics are appreciated.
     
  2. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,157

    fiftyv8
    Member
    from CO & WA

    I've seen guys use rectangular light tube as a substitute but originals always seem to look best.
    I had a model T that needed a sub frame and found one on ebay from memory, so it was original and not expensive to buy. Check out craigslist, ford barn or swap meets as well as I'm sure a decent set will come under $350.
     
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  3. jackalope
    Joined: Mar 11, 2011
    Posts: 687

    jackalope
    Member

    I was in your shoes and ended up finding a decent subframe that I was able to repair before chopping up.
    That said, when I do this again, I will make my own and here’s how I will do it.
    We will start off ASSuming all panels are already repaired and bottoms are not rotted out.
    Once you have the entire body MINUS subframe you will need to mock everything on a flat surface and internally run bracing wherever is needed so as to ensure squareness and good gaps/lines. Once everything is secured you can then start to build the substructure TO the in place body. I would NOT look at all those subframe contours on the original frame and let that intimidate you. Just do what I’m suggesting and you’ll be totally fine especially if this is being chopped and channeled.


    Sent from my iPhone using H.A.M.B.
     
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  4. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,501

    Mr48chev
    ALLIANCE MEMBER

    Someone did a thread a few years ago using the light rectangular tubing (on a 32 frame) but it should work on an
    A frame just as well. I hope so because my 31 Victoria had a wood subframe/sub rails that I want to replace with tubing.
    Check 31 Vicki with a Hemi's build thread as I think he fabbed his own subframe for it.
     
    brianf31 likes this.

  5. patmanta
    Joined: May 10, 2011
    Posts: 3,670

    patmanta
    ALLIANCE MEMBER
    from Woburn, MA
    1. MASSACHUSETTS HAMB

    Man, at least you Model A guys have the luxury of turning down repop subrails!

    I don't know of anybody even making Model T subrails for 26/27. If I did, I wouldn't have scratch built mine.
     
  6. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    Do you like and want to keep the channel ? ...
    if so, use some subfloor scraps and box them to make the section that shows when the door is open...
    like some '60's trucks did stock...
    I have some scraps, but put out a request and you will find some closer to home...
     
  7. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,157

    fiftyv8
    Member
    from CO & WA

    This may also help you depending in which direction you may choose to go.
    This was posted somewhere previously and I just decided to keep it for reference. Klar.jpg
     
  8. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,400

    manyolcars

    just dont use square tubing.That is so wrong
     
  9. Brian sent you a pm..........
     
  10. Mechman_22
    Joined: Mar 18, 2014
    Posts: 143

    Mechman_22
    Member
    from Nc

    following this since im in the same boat
     
  11. IronTrap
    Joined: Jul 13, 2011
    Posts: 468

    IronTrap
    Member

    Have a local metal fab shop bend up a 90 out of 1/8" and then cut and modify them to fit the contour of the body. The one leg of the channel will span the gap between the body and frame and sit on the top of the frame rails. The other will be the height/dept of the channel on your car. You can then build cross rails of your desired style. A good brake or that metal shop could bend up hat channel like stock or you can use straight channel as well.

    I did a video on the basic process at work on my coupe a few years ago. Shows the process a little better than I can describe!

     
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  12. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,157

    fiftyv8
    Member
    from CO & WA

    Great idea...
     
  13. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    A plasma cutter makes it look so easy... the right planning makes it look so good...
    I didn't hear him mention it, but one might locate the cross channels to align with where the seat bolts will be located... drilling a couple new holes to bolt the body down is a gravy job...
     
    46international likes this.
  14. brianf31
    Joined: Aug 11, 2003
    Posts: 659

    brianf31
    Member

    Good tips here.

    IronTrap, I was so impressed with the Pagoda coupe floor build that I saved it as a go-to document.

    My issue is that I won't have any lower structure on body perimeter to butt/weld/fit to the vertical leg of your inverted L. I also have some wide gaps between body and frame. So my thought is to form a Z the height of the channel. The lower horizontal leg will run up to the lower edge of the body.
    I also need to replace all lower edge sheet metal at the same time. I may have to add another L where the patch panels meet the Z.

    My biggest issue is what to do at the door opening. I need to replicate stock subrail curvature and perhaps the rounding break at the outer edge.


    Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
     
  15. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    30 years ago a buddy told me that to channel a hot rod body ;
    I should have a sheetmetal shop bend me some Z's...
    piecut to match the A and B pillar angles... weld...
    I found that ;
    the skins are close to the frame width at the cowl, you may have to bend the horizontal strip from your patch panel up and against the inside of it's outer skin...
    carefully set the body onto the lower flange and trace the outside skin of the body onto it...
    trim the lower flange 1/8" inside of the marks...
    lets you weld the inner fold of your patch panel to the trimmed flange edge of the "Z" and not have it show...
    careful with trimming the A and B pillars, you want them to have a good weld to the "Z"...
    .... before you do anything do your door hinges and pins ...get your doors right... weld braces to keep the body lines lined up...
    you can't shim the cowl later as the Z won't flex...H I H...
     
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  16. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    don't want to part with the full length subrails...
    DSCN1495.JPG
    .
    DSCN1494.JPG

    I showed them to give a perspective...
    should find scraps like these close to home..
    DSCN1496.JPG DSCN1497.JPG
    .tudor and pick ups have a different angle than coupes [see cuts]...
    coupe doors are 27.5" long, tudor and truck are 29.25"...guess both would fit...
    DSCN1498.JPG DSCN1499.JPG
     
  17. lostone
    Joined: Oct 13, 2013
    Posts: 1,527

    lostone
    Member
    from kansas

    Great info guys! I'm in the same situation myself. Thought about what others have suggested, have some L`s bent up for it.
    I would like to find the very back sub rail with about 18" of side sub rails to go with it. Been watching ebay but most pieces I come across are coupe and not tudor...
     
  18. chopnchaneled
    Joined: Oct 21, 2004
    Posts: 1,408

    chopnchaneled
    Member
    from Buford Ga.

    Tell me about it !
     
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  19. brianf31
    Joined: Aug 11, 2003
    Posts: 659

    brianf31
    Member

    Y'all have laid out a good approach. I haven't had any luck finding decent subrails but I have a thought. The body currently has an L along the lower perimeter and is temporarily supported by plates welded to the bottom of the frame as shown.

    20180101_114727_LI.jpg

    20180101_114903.jpg
    I'm thinking I'll add these plates at the cowl, A and B pillar and right ahead of the wheel well. I can gusset them for stiffness and tie the body down at the plates in a semi-unibody approach. So the load path would go through the vertical body structure, down through the perimeter L and into the frame brackets, hopefully keeping load off the body panels. I could add a Z from L angle to top of frame to close out the gap.

    I just need to figure out what to do at the door opening. The doors are currently shortened; I'll remove the 4" filler piece that's runs between the door jambs.

    How would the body hold up to this approach?
     
  20. murf 32
    Joined: May 30, 2013
    Posts: 66

    murf 32
    Member

    Probably not strong enough. But would (metal stud top hat) do? It seams to have the same profile as the cross members . Just a thought.
     
  21. Mike Paul
    Joined: Oct 10, 2003
    Posts: 931

    Mike Paul
    Member

    I'll have a nice set of coupe sub rails that are cut off just in front of the rear wheels. Still working on getting them out within the next coupe of weeks. Pm me if your interested.
     
  22. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    what do you want for it ?
    I wish they sold subrails that stop at the wheelwell [for an axle kick]... they sell the rear not the front... I am at 04210 thank you...
     
  23. Do you want to sell the sedan sections that you have? I could use those.
     
  24. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    they are nasty....only pic I have [snow] but see the rust in the crossrail and on the subrails...
    .fellow hamber has the rear cross panel 2" tall... repop..... came with his roadster... DSCN1495.JPG
     
  25. bct
    Joined: Apr 4, 2005
    Posts: 3,096

    bct
    Member

    I had a 4x8 of 1/8" bent into hat channel the same size as ford. On 50% of them i had the edge flange enlarged to 1". This will allow me to cut curves to fit the contours of the body. You could weld some 3/4 or 1/2" to the curves to hook the bottom hems of your panels, like on the model Ts. I plan on buying some 2x2 or 2x3 x.125 tubing to replicate the raised areas that start at the B pilars and go rearwards.

    Not sure why anyone would be negative on using tubing. If it's a finished car you would never know.
     
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  26. chev34ute
    Joined: Nov 13, 2011
    Posts: 968

    chev34ute
    Member

    This something I will have to deal with, with own build. I am putting together a 29 Coupe/Cabriolet hybrid and I have more than enough floors from all the different bodies and panels I have collected, including most of a 29 Coupe floor. I am thinking of taking it down to my local steel supplies store to see what the have in stock that might be able to be modified into subrails. As for the cross rails, I am thinking of hammer forming them over two lengths of box tubular RHS welded together. I will post up some images if I have any luck.
     
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  27. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,157

    fiftyv8
    Member
    from CO & WA

    As long as you have reasonable outside edges on the stock sub frame everything else can be remade in a sheet metal shop and welded in.
    All the cross channel rails can be replicated quite easily.
    Even outside edges could be fixed with some weld in patches.
    Obviously, new sub rails can be had from places like Snyder's and they also sell a rear half length if required as well as the cross channel rails if you want exact replacement stuff..
    Otherwise replicate the whole darn thing with rectangular tube and salvage your door opening pieces and cut then off and re-weld them to your new home made sub frame.
     
  28. -Brent-
    Joined: Nov 20, 2006
    Posts: 6,008

    -Brent-
    Member

    Model A Coupe Subrail Dimensions.jpg

    I converted the metric measurements to the nearest 1/16th.

    However, the measurements that worked for my 1930/31 coupe did not match these. Something about 30-31 coupe subrails being wider by an inch.
     
    Last edited: Jan 17, 2019
  29. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,577

    sloppy jalopies
    Member

    A buddy showed me his leftover "subrails" they were 16 ga. [z] bends...
    top horizontal sits on the frame, vertical is the depth of your channel...
    the lower horizontal can be trimmed to let the body sit on or beside it... HIH.
     
  30. brianf31
    Joined: Aug 11, 2003
    Posts: 659

    brianf31
    Member

    Here's how I ended up doing my channeled version. I fabbed a 16 gage zee that was welded to the cowl support structure, A pillar, B pillar and even the wheel well. Then I welded in the door opening portion of original subrails I got from HAMB'er Mike Paul.

    Channeled Subrail.jpg
     

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