Torsional rigidity test: 67 coupe

Discussion in 'Classic Mustang Specific Tech' started by mustbereel, Oct 7, 2007.

  1. I was in Chicago a few weeks ago and found myself with time to kill. I should have stopped by to see in person the work you're doing. Instead I spent about 6 hours at ORD. Maybe next time.
  2. i'm sure that will improve overall stiffness a little bit but with the flexible mounts it won't be as much as if the engine trans were solid mounted to the car. you could use solid mounts instead of an engine plate but again you'll probably see some flexing even there.

  3. i'm guessing yo could probably fish plate the roof seams on the insides of the panels and gain some strength that way as well. also the original shelby roll bars, though only a 2 point bar, were tied in at the floor and also bolted into the roof where the original shoulder belts would have been so that would have added some additional stiffness to the structure as well.
  4. :nonono:
    Yes, I see where you have added the additional bracing, along with the cage work. I guess where I am coming from is more of a stock look, hence no round tube cage. I have been following your fire & ice projects and have done (copied) many of the chassis strengthening ideas (convertible rockers, seat platform, engine compartment bracing) along with bracing from the rockers up into the B pillar area. So far most of this can be hidden by body, interior panels so I was looking for ways to add as much strength as I can while keeping the stealthy appearance.
    Does the structural foam have to be used in an enclosed channel (ie. frame rail, rocker panel, etc) or can it be used in a C type channel that is open on one side?
  5. I do not see why the struct foam won't work in an open channel. It should increase the strength of any struct member it is applied to. Some shapes should generate more bang for the buck, but I have no experiance with the material other than OEM applications.

  6. The integral nature of the roof on the structural integrity of the unit body car is the reason that I try to steer folk’s away form shaving the drip rails on these cars. While I believe that this can be preformed safely I feel that most people are not willing to do the necessary reinforcement to the roof that is required to offset the lose of this component.
  7. Agreed.

    When we shave the drip rails we always leave about 1/16" of the drip rail and then add a metal trim strip around the window opening and seal weld all the seams.

  8. Going back to the export brace: The reason it works so well is that it is a single broad piece with deep ribs. Using singular bars connected with Heim joints will only support the singular triangle it forms. And quite frankly the heim joints limit that. Looks pretty though.
    The Monte Carlo bar works so well on a stock suspension because the top of the shock tower flexes in more than the bottom and therefore causes the shock shaft to bind in the shock. Add the Monte Carlo bar and it works in unison with the lower subframe.
    The "X" brace attached to the subframe works to keep the back of the car structurally in line with the front of the car. Mass in motion wants to stay in motion along the linear path it travels. The X brace staves off the slinky effect as the car corners (that's a little over simplistic, but the best I can explain without lots of hand movement).
    Stitch welding the frame works if you look at forming boxes (i.e. cowl, frame rails, radiator support = box). In the track cars we also beefed up the LCA brackets and strut rod brackets to help hold things in place.
    Want to add some serious front structural support. Use a solid front motor mount plate welded up the inner fender wells. It works just like the rear seat plate by forming a wickedly strong box. But in this case it's a short double box because of the proximity of the radiator support. Of course it will rattle your teeth out.
    Remember the whole "mass in motion" thing. Every time you add something you increase the mass. So you can improve static measurements but negatively effect dynamic performance.
    One other thing to consider. Crumple zones. The nice thing about Reen's front sub frame bars is the "S" bending of the tubes. This allows the tubes to crumple on impact, while losing a marginal amount of strength for their intended purpose. (IMO) a great compromise.
    Great thread!
  9. Hi 66,

    I think it is important to keep all of the structural modifications behind the engine / front suspension and in front of the rear axle. That will keep all the original crumple zones, such as they are in a 60's comuter car, intact.

  10. More test

    I'm back at it again. I decided to make a new export brace that should act more like the orginal. As 66Runt pointed out the round tubes with heim joints can only support the load along the axis of the tube. Although I belive this triangulation is where the majority of the improvement comes from I wasn't really happy with the results of my braces. I made the new brace from 1"x2"x 0.60" rectangular steel tubing.


    The brace mounts to the fender aprons with 12ga. angles.


    For all you MII installers: I did not just attach the brace to the flimsy fender aprons. I have added quite a bit of support on the other side and I have reinforced the area at the cowl where the brace mounts. Look back through this thread to see the reinforcements. I don't know how effective this brace would be without these reinforcements.

    These tests were done without the rear seat divider and without the sfc x-brace. Also, someone wondered about the effectiveness of the tank armor to reduce flex. I put the gas tank back in to get an idea of how much that area contributes.

    Now for the test results.
    New baseline: 0.44"
    Round tube export brace: 0.39" About 11% gain.
    New export brace: 0.38" 2.5% better than round. Perhaps a heavier wall would ad more but not much better than the heim joint setup.
    Stock gas tank back in: 0.37" About 2.5% gain. Tank armor would probably add more but with a substantial weight gain.

    Hopefully by the end of the weekend I'll have the IRS cradle in so I can test that and then I have the engine in to see what effect that has.

    Attached Files:

  11. Very impressive progress!
    You might try a couple of "C" clamps to similate the other two bolts missing in this version versus the stock unit. Maybe getting some cowl flex due to the spacing of the bolts. The box construction *should* make up the difference for the original draws, and the gussets make that area almost as thick horizontally, so I wouldn't expect deflection of the brace so much as deflection of the center cowl without the extra bolts.
    Which brings up another point. On the race cars they had an upside down L piece welded to the cowl for additional support, instead of just relying on the lip. Something to consider for additional stiffness over the original test, if you plan to keep the brace.
    Once you complete all your testing do you plan to go back and review the process, then pick and choose what you actually want to do?
    Reason I ask, is that you are adding a lot of steel, and I'm not sure you'll reap the benefits by keeping all this stuff on the car.
    Take that with many grains of salt. I'm known to be somewhat of a minimalist. It's just really hard to deflect mass from wanting to continue in a straight line. It's also hard to speed it up and slow it down.

    Your workmanship is awesome, and this thread is priceless. I sincerely hope it will become a sticky!

    Just dawned on me, the original brace went to the shock towers. Conical structure, and shorter arms. I think the additional two bolts and the welded brace will help, but I don't think you'll realize the original reduction of deflection.
  13. Subscribing - interesting testing going on here. Is this to be a drag car or street/strip or road race?

  14. Fun street car but mostly it's a creative outlet. I build therefore I am. Emphasis on handling (hence the IRS).

    Runt66: I've added about 100lbs not including the x-brace or export brace. I realize I'm at the mercy of Newtonian mechanics and polar moments but with the 4.6 DOHC and IRS this car will be heavy no matter what. I'm expecting about 500rwhp with the mods to the supercharger so I want extra strength in the chassis. The fully dressed engine is about 630lbs vs. 480lbs for a 289 and 365lbs for the all aluminum 347 in my fastback. The fastback is about 2900lbs and I expect this car to be at least 3300lbs.

    I wouldn't add the jacking rails again but they don't weigh much and did show a measureable improvement so I'll leave them in place. I'm a big beliver in the sfc, torque boxes and export brace. The rear seat divider is a no brainer. I think I'm going to leave the sfc x-brace out and use the forward mounting holes to mount a custom transmission crossmember for the T-56.

    I installed the engine today and it looks like neither of the export braces I made will fit. The throttle body gets in the way. After I have the engine in it's final position I'll revisit making another brace.

    Blue Oval Man: Yes, I just had the stock tank installed. I'll be using a fuel cell so I won't have Tank Armor.

    Now for today's testing:

    Baseline: .38"
    C-Clamps to simulate 2 more bolts at cowl: .38 (I've already reinforced this area with 12ga angle so I didn't really expect anything more)
    IRS cradle installed: .37" At least it gave me something. Should better if I switch to delalum bushings.

    Just for fun a picture of the engine more or less in place:


    Attached Files:

  15. Some more awesome info! I want to build an all aluminium 331 with IR fuel injection and distributorless ignition, etc. (sort of the pinnacle of the Windsor technology evolution) - it's good to get some fairly solid info on the weight differences! What block did you go with? I'm thinking about using a Dart.
  16. \\

    I used the Dart 8.2" deck block. Originally I planned on IR fuel injection but the engine builder talked me out of it. He said the Webers were easier to tune! If I could do it over I would buy a kit from TWM and use Megasquirt to control it.

    I have this habit of weighing almost everything I put on or take off the car so the weights are pretty accurate.
  17. Wow! That's exactly what I'm talking about! Same block, and I'm planning on TWM with an Accel DFI 7+ controller (plus MS DIS ignition) but you'll be hard pressed to talk ME out of it hehe. At least until the time comes when I've actually got the car, and am building the engine... Maybe in 5 years, when I reach my 30s I'll be "ready" ($$$) to start my classic Mustang project.

    Well I'll stop interrupting your thread, I hope this car turns out in a similar fashion to Reen Machine's. (In terms of the actual product becoming a reality)
  18. A 2005+ Mustang 3 valve engine weights 420 lbs (dressed, not sure how much dress is included), according to the Ford Racing catalog. This surprised me, as all the other variants of the modular engine family are not exactly known as light weight.

    420 lbs is only slightly more than a 289/302 with aluminum heads, so that's not bad. I guess it's more compact than a 4V modular engine too, but I don't know by how much.
  19. 420lbs sounds light but it's hard to compare without knowing exactly what is on each engine. With the Iron block my DOHC weighed 700lbs. This included AC, PS, Alt, intake with supercharger, flywheel (Al), starter, exh. manifolds, motor mounts and a few misc. hoses that were still attached. I think it included the clutch and pressure plate too. I subracted 70lbs for the Al block but haven't weighed it since reassembly.
  20. As another 67-68 vert owner with the GW subs welded in...your best bet is to run some bracing to tie the two SFCs together like TCP offers. That can make exhaust/driveshaft removal an issue down the road, but the stringers they are talking about are a no-go on verts due to the different undersides and rockers.