C notch advise

I went ahead and did a 3" deep C notch in the frame for my 56 Chevy pickups this weekend. After welding everything up, I worry about the strength of the frame. Is there a way to beef any of this up now? It's boxed with 1/8" plate and notched with 1/4 thick walled pipe.
I won't be towing anything or hauling anything in this truck, should I be worrying about the stress this is going to take?

 

Need to add more beef to the top. Looks fairly weak as is.

Try to keep the frame height intact, just moved higher.

 

Yep, a gentle hump that somewhat matches the curve of the frame rail and stretches and tapers out in each direction a few inches should do it. That's what I plan for mine with a similar notch.
I've seen a couple where the builder took a piece of square or rectangle tubing and notched an trimmed it so that it ended up being a tapered hump over the notch but that might be more work than using some flat bar to do the whole thing.

 

The easiest way to strengthen the area is to get a square tube and welded it to the top of the frame above the notch, cap the ends and that woud be enough. The way it is now isn't very sturdy.




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As the other guys have said you need something above the notch. Possibly the full original boxed section size of the frame before you notched it to get back the strength.

I can't see from your pictures, but I hope you had the rear of the frame supported when you did the work and were careful with measurements and leveling to be sure it didn't move.

If not then the part of the frame to the rear of your notch work could be way off where it is supposed to be. Sagging down and unlevel or worse.

 

You're work looks good so far, so don't fix the problem by making the fix look like an afterthought.

With that in mind why not weld another 1/8" or 1/4" boxing plate over the first one?

 

It was all supported by jack stands in front and behind the area. The frame stayed straight and true through out the entire job

 

This exactly how I do my F1 and F100 frames, but they are slightly taller by the look of it. Looks like you've done a good job, no use redoing everything, like some have said, just weld an extra gussette to the top about 12" long, you'll be good to go.

 

boxing it like you have should be enough, even for light towing or light loads

 

And on what engineering degree do you, and others of ike mind, base this opinion? There is NO WAY this "C" notch is as strong as the original frame section.

This is the second thread in two days in which posters have assured an OP that their work is "good as is". And, in both cases, nothing could be further from the truth.

Unfortunately, we have too many HAMBERS offering advice who "do not know (realize) what they don't know" on structures. Get a few text books on geometry, physics and structural design and bone up on the subjects.

Posts #2, #3, #4 and #5 "get it".........follow their advice.


Ray

 

If you are using a leaf spring setup, then yeah, that C-notch will need more reinforcement to prevent it from folding up.

If you are using a 3 or a 4-link type suspension with all of the loads supported ahead of the C-notch, then there is much less concern/stress on that C-notch.

I have a degree in Mechanical Engineering and I'm a registered and practicing Professional Engineer of close to 30 years. I hope I pass the audition.

 

From the c-notch back to the end of the frame, you have effectively a 1" tall frame, so leaf springs are out. The strength of the frame comes from it's cross-sectional shape, and the height of the web. There is a good article out there comparing different c-notch methods, and this pipe-c-notch is the weakest by far. Yours is probably around 10% of the original frame strength.

 

might not look the best but you can plate the outside of the frame with 1/4 inch plate at least 1 foot for and aft . if the bed your using has a metal floor it can be reinforced under side and used as a top brace when mounted to the frame

 

So what size of square steel should I be using on top of the rail?

 

My suggestion would be minmum of 1/8" material (3/16" ok too). Pieces about 12" long of 1/8" plate contoured to fit the upper frame rail, 3" deep (high) at the center of the "C" notch and tapering to '0' at the ends. This gives a taper 6" long either side of the center. The plates would be welded to either side of the frame rail, duplicating the rail width you have established. The plates would be capped with a strip of 1/8" spaning the length of the plates, terminating at the original frame rail.

Doing that would replicate the shape and strength of the original frame....actually a bit stonger, since it is boxed and not an open channel as originally built.

Ray

 

Should the plates be welded to the outside of the rails or do they get welded
On top of the rails but flush to the outside

 

On top, but flush to the sides, would work very well and look better than welded to the sides.


Ray

 

Thanks Ray, I appreciate the help man

 

http://67-72chevytrucks.com/vboard/showthread.php?t=457037
I've posted this link before but, it may help you so, here you go.
I took this from 67-72chevytrucks.com.

 

And don't grind down your welds. You are doing this for strength, not looks.

Disclaimer, I am not an engineer nor play one on T.V.

Neal

 

That link is great Walls, sure wish I would have seen it before I started. oh well, nothing we can't fix. Someone also sent me the link on Facebook a couple hours to late

I built up the welds on the one side already and will be doing the same all around the area. Thanks for that tip. I'm teaching myself how to weld as I go

 

Edit: Oops! looks like someone beat me to this.



These exerpts were taken from:

http://67-72chevytrucks.com/vboard/showthread.php?t=457037

Hope this helps.

Bolt In
This model replicates the popular bolt in notch, it gains you about 3-1/2" additional clearance. It captures the bottom and the outside of the frame and is ¼” thick. The frame is not boxed. FEA reveals the frame is 80% weaker than stock.

Bolt In Type Notch

​

Add a welded in boxing plate to the back of this design and the FEA reveals the frame is still 60% weaker than stock.

​

Weld In (Dim. data was taken from this website: http://www.suicidedoors.com/notches/...step-notchkit)

The half circle notch is slightly stronger than stock (about 10%) and gives about 8" more travel.

Half Circle Notch FEA

​

 

Walls: I am constantly viewing locals 'C-Notching' their frames...much to my chagrin.
Your posting of the Tube Analysis site is very timely, should be a 'Sticky'!

Excellent presentation.

 

thanks Walls-very helpful and well-done.

 

I made up a cardboard template of what I'm thinking this arch should look like. Look about right? That gives me 3" above the peak of the notch and spans over 16 inches of length

 

Better. Much better.

 

Although I totally agree on the strength of what is pictured, AND on some advice being wrong/bad from some HAMBers......... asking for a degree? Really? I would imagine if anyone working on his car on here needing a degree for that particular job (elec for wiring, welding certs to weld, mech eng for suspension, and so on) there would be ZERO (or at least very few) posts on here.

 

That should work for frame strong wise, but what's that do to the floor clearance.
Theres a lot of ways to skin that cat of yours and that certainly is one fine way.

 

The bed floor is being moved up so clearance won't be an issue.

 

Think about what the frame looked like before you notched it, and try to make it look that way again except humped over the notch.

As someone pointed out above, use channel or square tubing to make the hump. You can taper it down from the center, but if you were to cut your frame vertically at any point, you'd want to find the same cross-section.