Question...I just noticed that when standing in front of my car, looking down the frame rails, the both have a slight twist outward from the center of the car of about 3-5 degrees. The twist on each rail begins behind the front crossmember and ends about midway of the door. In other words, the top of each rail is rotated outward. No engine in the car yet, btw....but I've had the SBC installed before I moved out to CA and tore it back down. Frame rails were boxed and SoCal K member installed. Should I be concerned?
id get it on a jig and straighten it before putting it all together and noticing it drives all weird... and if you notice it every one will..
what do you think caused it? i agree with Notrod13, you should correct before putting it back together.
When I first read your post I thought the rails were unboxed and was going to say that Model A frames are like spagetti without boxing and proper crossmembers, but then I read that you have those modifications made already. Who did the boxing and crossmembers and were they like that when that was done ? Don
Im not sure...it's weird that *both* rails are almost mirrors of each other, the twist beginning and ending at the same spots, with almost the same degree and fade. I'm wondering if maybe the old trans crossmember was removed before it was boxed? At any rate, if I end up having to straighten it, the K member will have to come out beforehand. Sigh.....I should have just bought a new frame from the get-go instead of being dead set on a vintage frame. So f-ing annoying.
A fellow HAMB'er did it for me. What really ****s is that before I got this frame and the work done to it, I got left in the lurch by a different HAMB member on another bad frame ....tried to get things rectified.....ended up getting left out in the cold. So now...two frames that are jacked :/ Here's a pic explaining...had it on my phone, photoshopped it. I can try to do a dead on photo tonight. The red lines indicate where the twist begins and ends, arrows indicate direction of twist and degree....4 degrees on p***enger, 5 degrees on driver.
Well, it looks like the front crossmember and the middle crossmember are doing what they are supposed to do because the frame is twisted only in the area between them. My initial thoughts are that once you set the motor weight down on those mounts it will force the frame back down and take some or all of that twist out. Have you checked it with the motor resting on the mounts yet ? Don
Yeah, that's what I'm hoping...I never really noticed it with the motor in...maybe at that point it'll only be a degree or so....which might be ok at that point. The 305/Alum PG combo should weigh in at 800lb or so...the flathead/t5 will come in at 900 or so....ought to be enough to force it back perhaps. I'll see.
One thing you might consider is to do what I did with my A frame. I used a Speedway crossmember under the motor, that way all the weight is resting on the crossmember not the frame. It also puts one more crossmember in between that long distance between the front one and your X or K member. I know it is not totally traditional, but mine has been under there for over 20 years and I abuse my car a lot and it has helped keep the frame from twisting. Don
1. Ever notice when frames are 'jigged' on work tables or frame fixtures they are actually welded to the holding fixtures? 2. If you place the engine/trans in the solidly welded & boxed frame and it 'straightens' the twist, it is not boxed and braced. Simple. Black and white. (otherwise, a jigged, boxed, and cross membered frame would sag 4 or 5 degrees when weight was applied) 3. The 'fix' for this one can be simple. Borrow or build a steel table or set the frame on a level sheet of steel. Cut the tube cross members loose at their joints, and make a simple 'spanner' to twist the rails straight, while being held down. This can be square or rectangular tubing, and can be temporarily welded to the rail and jacked (bottle or floor jack) while frame is chained down. Simple leverage. I have in-floor chain tie-downs in my shop, for this purpose...but I've used steel I-beams, flat 3/4" steel sheet, and long pieces of railroad track before! 4. The dropped tubes Don is showing are a good example of superior strength without blocking the way for exhausts, linkages, etc. But don't add them until you twist the rails beyond induced tension.
Sounds like a simple way to re-set the frame rails. I'd mention to tack, and move around with short weld runs, to let the distortion-shrinkage pull against it's neighbor, a new and opposing weld. Don't simply weld on top then flip and weld on bottom side. I learned that one at sixteen years.
Are you measuring your twist angle on the outside of the rails, or on the new boxing plates? You might want to check both. It's possible that the top and bottom flanges of the rail were never the same width so when the plates were welded in, they are now leaning outward. If you really do have a twist, I think you'll be hard pressed to bend them back straight since they are now boxed. You may just want to leave them as is and take the twist into account when setting up the rest of your ch***is. You'd probably want to cut the motor mounts out and reweld them in so they are flat.
I measured twist on inside and outside....outside is slightly less than inside...a couple degrees at most. I also used a level to check the cowl mounts that are now exposed since I shortened the body....they're off level by several degrees, too. I have to make all new body mounts because of the body mods...redoing the motor mounts isn't a big deal. Wondering what else I'd have to take into account to change. The rest of the ch***is is pretty much set up, rear radius rods, etc.
I'm thinking that if the frame sets level side to side both front and rear and the crossmember is installed correctly you might be OK to leave it and continue on. What is your plan for the build? A mild channel would make the visual issue go away, or how 'bout new sides on the frame? That is what I did on my A. On the other hand if you will not be able to live with it, take it apart and start over. No harm in that either.
The visual isn't that bad, at least its mirrored and in the same spots. My big concern is everything else...geometry, handling issues.
I have 2 thoughts...(1) I had one that did that when I welded in the motor mounts. It was a motor swap on a mostly finished car, so I just left it that way. I drove the car for several years that way and I didn't notice any problems. Its just a old car, not the space shuttle. (2) If it bothers you fix it now, no matter what it takes, or you'll never be happy with the car. JMO
Cool...report back and let me know. I searched 501madmav's threads and didn't see anything about it...maybe it's buried in one of them somewhere. I skimmed through his roadster build and didn't see it. Regarding the unboxed rear, I read somewhere that leaving the rear portion unboxed allows for the frame to have a little more movement and prevents cracks of the rear crossmember or some such. I'll have to dig that up.
Jeez, that will NEVER work... pretty sure the car will immediately catch fire, careen into oncoming traffic, and explode upon driving it... In all seriousness, I would measure the frame to make sure it's not twisted/crooked/diamonded/etc. If it checks out within 3/16" or so, put it together and drive it. A couple degrees difference on the top of the rails between the front crossmember and the Kmember isn't going to mean squat on a glorified horse and buggy ch***is riding around on cross springs and bias ply tires. I'm all for having a nice, sound, square ch***is to build on but some of you fellas seriously over****yze this ****.
H'i I just caught this thread, I'm running a completely boxed [1\4" plate] 29 model A frame. this winter I'll upgrade from a sbc to a blown 392 elephant motor [Hemi]. do you think the motor cross member will add more support over a more traditional frame mounted bisket setup? Thanks John
LOL! Yeeeeeah. I try to look past the over****ysis when I ask a question and try to glean the "yes it's ok" or "no, you're f'd" out of responses.
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