Frame Notch Based On Strength I originally posted this on another website March 2011, since Classic Parts Talk is where my build thread now resides I am reposting my notch thread here. A lot of guys are notching their frames to lower the trucks stance. As a Mechanical Engineer some of the photos these guys have posted on various websites reflect notches that are scary. Please note that I don't have a dog in this hunt; I am not selling anything. Don't shoot the messenger, I am merely trying to help. How you notch your truck frame should depend on its original factory design and how your truck will ultimately be used by you or any future owner. My personal philosophy has always been any change to the frame should restore the original strength, but that is me. I always assume that just because I may never push the envelope of my truck to its rated capacity doesn't mean the next owner won't. Things to consider: How do you plan to use the truck? If those plans include hauling loads in the truck or pulling a trailer with the truck the frame will see these loads and frame strength will be very important. Long bed trucks load the rear frame section more than short bed trucks. A look at various designs using Finite Element Analysis (FEA) A Stock Frame (based on a 65 C10) is the baseline for all of these designs. The FEA assumes a factory stock standard coil spring / trailing arm type suspension, circa '65 (I have been told that the suspensions from 63-72 were all very similar) and assumes a bending moment from hauling and towing loads. Worth noting is that if hauling and towing loads are not present the trailing arm suspension style frame has almost no load at the rear axle, only the weight of the frame itself and the truck bed. A Stock Frame (based on a 65 C10) is the baseline for all of these designs. ------------------------------------------------------------ Commercially Available Notches 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 1/4" 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 the suicidedoors.com website, circa March 2011) The half circle notch is slightly stronger than stock (about 10%) and gives about 8" more travel. Half Circle Notch FEA ------------------------------------------------------------ The Step Notch is slightly weaker than stock (about 10%) and gives about 8" more travel. Step Notch FEA ------------------------------------------------------------ DIY Weld In Notches Pipe Notch. This yields 2" more travel than stock and is as strong as a stock frame. It utilizes a 3/8" reinforcing pad and a 1/4? boxing plate to accomplish this. Pipe Notch FEA Deep Pipe Notch. I saw this being done on one of the websites. It was a boxed installation and it is about 76% weaker than stock! Deep Pipe Notch FEA ------------------------------------------------------------ Step Notch made from rectangular tube. Here is one I developed that is made from mitered 3-1/2" x 2-1/2" x 1/4" wall tubing. It is about 10% stronger than a stock frame and gains you about 3-1/2" additional clearance. Tube Type Step Notch FEA Tube Type Step Notch as viewed from inside ------------------------------------------------------------- Summary If you want the frame to be as strong as stock and you want a frame notch deeper than the 2" there is simply no substitute for adding some sort of truss structure, or replacing the frame section with another structural member that has the same or greater section height as the original frame. Whenever someone starts talking about a deep frame notch (> 2" nom.) and state that just by adding thicker plates to the sides of the frame rails this makes the frame stronger than it was in its original condition, yet they are and not adding vertical height, they do not understand beam analysis. Some final thoughts The implementation of any design affects its strength. The final fabrication can only be as good as the welder / fabricator performing the work. I have yet to see a bolt in notch that will restore the strength of the frame to the factory condition. I have not seen any manufacturers "certifying", via a signed document, the strength of their notch kits. The information posted here is for reference only. Results will vary based on actual dimensions, materials used and the quality of the implementation and fabrication.
Safety knows no season Well written & said there ! . This is why I so dislike Hot Rods : less than .001 % of them are safe in any way shape or form because of failure to understand or even try to understand , the basics . In my years I've seen many terrible crashes and dead people due to mechanical failures after someone made suspension / frame changes and didn't do enough .
As many trucks as I seen butchered in the forums in the last ten years, and as many slammed trucks I see on CL there is going to be a lot of good body parts opening up soon....! The sad thing is they (not all) will take the cheap way out to get it done, even with the better kits that are out there such as porterbuilt....its not unlike the ratrod craze....!
Well said Nate. I catch considerable flak on other website for wading into topics where a poor design is being discussed. All modifications need to increase or maintain the original capacity of the vehicle. If it doesn't, then don't do it.
The Sad Truth Is that ignorant folks are often scared to admit they have NO IDEA what they're doing and so prove they're stupid as well as ignorant (NOTE : no shame in ignorance , it simply means you don't know a thing . stupid is knowing a thing is wrong or bad then doing it anyway) by attacking the person who tries to help . Yet another version of " my d*ck is bigger than yours ! " ~ seriously who cares about your masculinity ? . SAFETY KNOWS NO SEASON ! if you've ever watched a person burn to death or die slowly because of basic Vehicular Stupidity , you'd understand why some of us care enough to mention how dangerous your " TOTALLY AWESOME DUDE !!!!" POS is and how you can make it better . The other site I go to has about 1/3 C - Notched trucks and most could be used for how NOT do do it in this article . It's all fun and games until someone gets hurt or killed .
Sadly , The whole " C Notch " thing is most loved by the very typ of ego driven idiots who neither know nor care about safety , as long as it " Looks TOTALLY AWSOME DUDE !!!!! " it's fine , right until it breaks and they get hurt then all Hot Rods are suddenly bad and must be outlawed , blah blah rant whine , snivel etc. I get this same thing (B.S.) in the Motocycle and Low Rider world too ~ as long as it LOOKS good , who cares if you can't actually drive it anywhere ? . And everyone calls me the fool because I drive an ancient 6 cylinder P.O.S. everywhere I go , 800 miles every week and usually faster than most traffic .
