flexin frame...need some fab advice plz

A bit more frame help---When you cut things apart, I wouldn't box the crossmember. ---(boxing a section that already has 4 sides doesn't really serve any purpose structurally). Go and buy a new peice with a minimum 3/16" wall thickness (yellow in model).The new side members (dark blue) should but-weld to the ends of the existing rear side members, and the new crossmember should end on the insides of the outer frame members.---Doing it this way, very little of the front to rear stresses will p*** through the crossmember. They will mostly p*** through the perimeter frame as it should be.---Brian

 

Thanks again...I am using 3/16" tubing for the supports...another area I was looking at, and someone suggested was where the builder welded in the kick up in the rear frame. Its just **** welded, I thought maybe I should run some plate on each side of the weld to add strength...or is this a waste of time?

If you enlarge this pic you can see what I am speaking to...the seam is right near the kick up.

 

Do as Brian's second pic shows, that is the best way and a much better pic than what I tried to show.

As for the **** welded section, if the welds are good it should be fine, BUT, I would suggest a doubler plate extending from behind the **** weld joint and extending onto the NEW piece you add would be a very good idea.

Cosmo is right about the height of the frame rail is really where your flex problem is still going to have some issues. If you can make the frame taller, it will help considerably.

However, your current fix with the pieces added per the diagrams will improve your current design significantly.

 

If it ain't broke, don't fix it. I don't think its necessary---however---if you would feel more secure with a strengthening plate in that area, why not weld one on the inside of the frame where it won't show. It certainly won't hurt anything, and if it makes you feel more secure, that alone makes it worthwhile.

 

I should have time next weekend to put it back together...thanks again for all the info.

 

Hey erock805---just curious---what are you calling a "kick-up"??? The generally accepted term for a "kick-up" is the point at which the frame goes from horizontal and begins its upwards climb to p*** over the rear axle. This position in your photograph is about 36" or more from where you have been welding and grinding, and I can't see any seam there. Am I confused, or are you using the wrong terminology?

 

Nope I am using the correct terminology....If you blow up the pic u can see where it was welded together about two inches before the frame kicks up over the axle.

here is some pix of the thing apart...

 

So I looked at the picture and realized that I only can see it cause I know where it is...here is a couple more shots of the seam before the kickup.

Also I took another shot of the crossmembers. Brian, I u suggested replacing the entire peice...but I could resist showing such quality workmanship.

I know I aint perfect...but I never would done something like this...

 

what the hell are you talking about 2x3 not being strong enough. do you realize how many people run 2x3 frames with no problems. what is your frame made of?


also have you ever seen 2x3 break?? where would you come up with it actually breaking in half?

 

Erock---Yow, that is ugly as old sin!!! I see what you mean. Yes, seeing what a mess the rest of that frame is, I would definately fish plate the kick-up on both sides. As far as 2" x 3" material goes, I personally wouldn't use anything less than 2" x 4" x 1/8" wall, but I know that there are a lot of cars out there running less.

 

Cosmo is correct...this rear frame section is designed to be used when a roll cage is installed. What is the wall thickness of the rectangular tubing? Also ladder bars are not the most ideal setup on the street. They bind and will cause an already weak frame to twist. Ladder bars are for drag racing. You should consider a 4 link setup with either straight or triangulated upper bars. The more triangles you integrate into a frame design, the stronger it will be.

 

The issue is not whether it will break, but the stiffness, or in the case we are dealing with here, too much flex. A taller frame rail WOULD be stiffer and less flex than a 2x3. Will 2x3 break? No, it will not break. Since the issue is too much flex, a taller section gives much more stiffness in bending.

 

the frame tubing is 3/16th that i can tell... as far as the ladder bar set up....I have heard that before, but they seem to be common.

Right now I am just hoppin I can get this thing back together again...this is the farthest I have pulled a car apart....I keep telling myself patience, patience, and when I start rushin...I walk away for a bit...if not I know I will fu@# it up. Thanks again to all. After I fix the crossmember, kick up, and weld up the two havles together along with the supports I will look at adding heigth to the thing...

I still gotta figure out how to make the power brakes fit under the body. One step at a time.

 

Update!!

 

oops ...here is whats happened in the past couple of weeks.

• I cutt three and half inches out of the frame.
• pushed it all back together and welded it 10 times better than the original weld
• boxed the cross member with 1/4 " plate
• added frame supports on the sides of the old frame from the back to where the fire wall will be...see pix

Now here is the question...is this strong enough? or should I add two inches under the main frame from the rear cross member to just under the fire wall???

 

man that looks 100x better keep up the good work glad you fixed alot of that mess

 

Wow, nice work man, that looks about a thousand times better.

With those tubes doubled up now where you added the new ones, that shouldn't see much flex at all in that spot now.

great work.

 

Ought to be strong as a garlic milkshake!

 

Great work!!! You do not need to add anything to the depth of the frame----you're done. Ya did a good job, congratulations.---Brian

 

Mucho betterer!
Brian's drawing and your crafting of the side rail stiffeners are just what the doctor ordered. That original 3 x 2 crossmember as "torque-tube" was not nice! Now you've at least got the front-to-rear stiffness you need. Hopefully less bouncing. Imagine if you had a Chrysler 392 set back into the p***enger compartment, the m*** would rotate that short section of crossmember until it snapped.

 

Thanks to all Esp Brian and your image...that did the trick. I am going to fish plate the weld before the kick up this week, mount the brakes...then figure out what to do with the fire wall (more quality workmanship from the previous owner).

Any ideas what I should use as body mounts?

 

Nice work and I agree you should not need any additional material under the frame rails. You have probably fixed 90% or more of the flex problem you had.

 

Looks good to me. Doubling the outer frame rail gives twice the strength, which should be all you need.
I might go with a bolt-on loop under the driveshaft, because I still don't like that center crossmember.
As to body mounts, two flats with a section of bias-ply as an insulator might work well.
Tip here: always set up your body mounts with 3-4 shims; you'll inevitably need to adjust, and this'll allow adjustment up AND down, if need be.
Cosmo

 

Uhm...I dont get it? "flats"? sorry what do you mean by flat? It had inch thick rubber between the frame and the body...is that good? I can post a pic.

 

Good to see things are progressing nicely. Be carefull with the shims if your using more than 1/8" to 3/16" worth , it could be an indicator that something in the ch***is or body mount area is still out of place. I know the old bodies used wide tolerances but as far as body mounts they werent that far off. Radiator supports now that's another story.

 

palosv3---You are correct if someone is building a car on its original frame. In this case, where the frame was built by an obviously unskilled builder ---you use whatever shim thickness it takes to level the body and box. As far as "what are flats"---I think cosmo means two sections of flat steel (as in big washers) with a peice cut from the face or sidewall of an old tire between them---(an old hotrodders body mount trick)

 

Kool...I can do that easy...thanks again Brian

 

The issues of the shims are important as they are alignment indicators. If there is a sag in the rails it could cause caster issues in the front suspension. Regardless of the errors made by the initial builder,they need to be paid attention to.

 

much improvement!congrats and keep it up