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Tech Request: Transmission Tunnel

Discussion in 'The Hokey Ass Message Board' started by GTSDave, Mar 4, 2008.

  1. GTSDave
    Joined: Jan 10, 2008
    Posts: 133


    I have come to the point with my Barracuda where it is time to fab up the tranny tunnel. So far every thing has been going pretty smooth with the chassis build but the tunnel is giving me a headache.

    I need suggestions on how I could roll out a couple of cone shapes to start out on this thing. I am limited on sheet metal tools, but do have a bead roller and lots of cutting equipment hehehe.

    What I was hoping for was a few suggestions on ways to form a couple of cones / tapered sections that I could weld together to form a new tunnel.

    Does anyone have a few tips for me?

    I guess I should add this is a race piece with the entire tunnel cut out at the moment. I am running a wedge with a Jerico 4-Speed and Lakewood scatter shield. Nothing is stock, and I am still learning metal sheet metal work.

  2. ray-jay
    Joined: Feb 23, 2008
    Posts: 200

    from Buford GA

    I used to improvise a lot when it came to sheetmetal fab. If you keep the sections short then you can easily bend them over a trailer tire, mini bike tire, your thigh or other round object. By short I mean front to back as it would be placed in the car. Just do a mock up out of poster board taped together and you will then have the patterns.

    I used .040 alum sheet a lot. It is a bit more difficult to form but it is less likely to kink or acquire dents while forming.
  3. GTSDave
    Joined: Jan 10, 2008
    Posts: 133


    Class rules dictate I must use steel. Most of the steel on this car is 20 gauge, so it is a little tougher than aluminum to bend.

    I was thinking of doing it with 2 cones. One large one coming off the bell housing area, then a second one tapering off to the driveshaft tunnel.

    I didn't think of using a tire to bend around it. With all the dirt bikes, go carts, and other motorized toys at the house I may be able to find a tire that is the right size.

    Thanks for the tip.

  4. Here's a neat sheetmetal site:

    TUTORIAL: Learn how to layout a cone

    Learn how to layout a cone and the formula, these numbers can be replaced with your dimensions.

    The formula for the cone is...

    - First you must find the difference between the large and the small Dia.
    - Multiply the large dia. by the vertical height,
    - divide this product by the difference first obtained large dia and small dia)

    This will give you the length of the center line you need from the top of the cone to the intersecting point (A)

    Large Dia - Small Dia = 20" - 8" = 12"

    Vertical height X Large Dia. 22" x 20"= 440

    440 divided by the product of the difference in dia.
    440 / 12 = 36.66 and this 36.66 is the length
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  5. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,106


    We just use poster board to mock up what we want, then use that as our patterns. You can put it in a brake and bend any corners, punch holes for clecos, etc. It works very easily and holds shape well enough to approximate metal.
    Start with a straight tunnel from the rear, up to the tail shaft. Leave it too long until you put in the tranny tunnel to see where they meet. Once you have it mocked up, you can mark for flanges and write notes all over it. Add some here, trim some there. Step back and take a look at the finish design before you ever cut a piece of metal.
  6. 29moonshine
    Joined: Dec 30, 2006
    Posts: 1,292


    like scottbaccus i use poster board for mock up build it to fit a telphone post makes a nice radius
  7. Back in the day we used to swap Rocket Motors and Nailheads into our Shoeboxes.

    Doin' a trans tunnel was easy.

    We went to the junkyard and had the guy cut the trans tunnel out of a 59 Ford.
    57's & 58's would probably work as well, but we always went for 59's
    Nice part was, the 59 throttle pedal could be part of the install if you cut things right.

    The 59 tunnel was cut up into the firewall area and out onto the floorboards on both sides.
    It was more than enough to cover the hole made when the Shoebox trans cover was removed and the additional sheet metal that was cut away for bellhousing clearance.

    Screw it down with a minimum of sheet metal screws then weld the trans cover to the floorboards and firewall.
    Made a nicely finished product and wasn't obtrusive.
    A little undercoat and you were done.

    You should be able to do the same with a newer trans tunnel than 59.

    Don't leave the sheet metal screws in the floor.
    Some guys did and they paid the price with cuts and blood when pulling a trans or clutch.

    Use a short 10-24 to hold the pieces together if you don't weld.
  8. about using the front tin piece off a corn picker, the part that goes between the rows of corn when they pick it. If you've got any farm implement salvage yards, these should be cheap. A buddy of mine used these and they worked out real well.
  9. atch
    Joined: Sep 3, 2002
    Posts: 4,438


    cool stuff like this is the reason i try to read everything C9 writes. and then i usually scratch my head while saying to myself "why didn't i think of that?"
  10. 29Jay
    Joined: Aug 9, 2007
    Posts: 1,101

    from Ft Worth

    I love tech week... could be teach me something else I still have to do week... You guys ROCK...
  11. GTSDave
    Joined: Jan 10, 2008
    Posts: 133


    Good points all of them. I like the telephone pole idea. I also like the idea of cutting a tunnel out of another vehicle. I'll bet a pickup tunnel will easily clear that big honkin skattershield.

    I have been welding for many years, just not much on race cars hehehe. I am one of the lucky ones with MIG, TIG, Stick, and Plasma right in my garage. My grandfather was a welder after the war and had me welding by the time I was 12. Made some pretty bad ars go carts and BBQ pits for extra cash in my teens. Can't wait to finish the Cuda, and GTS. Once those are done then it will be time for the '30 A, 5 window. Then I can go wild, because there wont be any class rules to worry about hehehehe.

    Thanks everyone for the suggestions!

  12. ray-jay
    Joined: Feb 23, 2008
    Posts: 200

    from Buford GA

    Do you have Cleco's ?? If not, buy about 50 in different varieties and a couple of sets of the pliers.
  13. blowby
    Joined: Dec 27, 2012
    Posts: 6,587

    from Nicasio Ca

    Bump. I'm on my second cardboard tunnel, a few more and I'll be ready to try a steel one. Since I have no sheet metal tools other than snips I was going to have the local supplier cut it for me, but I found this blade in my table saw pile. Anyone ever use one?

    Attached Files:

  14. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,343

    from illinois

    Weld a couple short sections of angle to the ends of a section of 2-3" pipe so you can clamp it to your work table.... slip the sheet between the table & pipe.. clamp it down.... poor man's brake & soft bends !!!
  15. Mello1
    Joined: Dec 7, 2013
    Posts: 1


    try using a preform cement tube they come in different diameters. Layout basic shape with poster board and tape, then transfer to tube. get shape and height. clamp it to some plywood and start laying up some glass. don' t forget mold release on the tube!! this months streetrodder had an article!
  16. Larry T
    Joined: Nov 24, 2004
    Posts: 7,679

    Larry T

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