Thread: How to properly design a gusset?

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Originally Posted by Youngster

If your welding skills are marginal, the ''backing'' is a good idea. One thing you want to be sure of using this type of joint is that the ''backing plate is right against the tube. Any gap will cancel the benefits you hope to gain from this system especially if you are going to gring the welds afterwards.

Another alturnitive is to have an experienced welder do the work for you.

Ron

The "Backing" is a good idea no matter how good a welder you are. A gusseted weld is simply to some a safety factor. I guess the engineers amoung us can decide if its needed or not. It would seem to me that any simple "BUTT" weld would benefit to some degree with a little internal support.

I also don't understand the "Experienced Welder" comment. Would seem like a good welder would be what is needed, plenty of them on here. Some experienced welders may be bad welders. Depends intirely on how they were experienced

RS

Hombre,

I love your welding comment! That reminds me of the saying, "Wisdom always comes with age, but sometimes age comes alone."

Generally, the filler rod used in welding is stronger than the base metal. That means that after a full penetration weld is ground down to the exact thickness of the base metal, the connection should not break at the weld. However, there are many factors that can weaken the joint. Any flaws in the weld weaken it such as holes, cracks, or impurities. And the heat and cooling of welding changes the chemistry of the base metal around the weld which often makes it more brittle than it was originally. For these reasons, it is a good idea to add a gusset plate across the weld to reinforce the original weld and to add weld length to the connection. Obviously, if you divide the force acting on the joint by the weld area you calculate the stress on the weld. By adding weld length, the stress goes down.

Mark

To me a gusset goes on the outside, bridging an angle. The over plate across a joint was always referred to as a fish plate on trucks and heavy equipment, you may call it something else. I usually try not to weld a fish plate on the ends as a perpendicular weld will weaken the frame at that point and it may break across the end of the plate where the wled is. I'm no engineer but usually I try to visualize how the stresses will apply and reinforce accordingly. There may not be a set formula. I also don't think the frame in the diagram needs any gussets but a plate on the inside over the joint would be good. On my last frame I opened up the frame on the inside so I could get inside the tube and put a good reinforcement along the other side without it showing. Then I welded a piece back in to close it up and plated over that with a larger piece. Now the outside of my framrail tubing is plated and you can't see it.

I have to agree with Jerry and a couple other guys. You don't even need a gusset. 2 x 4 x 3/16 wall and assuming 16 feet long and 2 pieces , you are into about 200 pounds of steel just for the main rails!! Now you should be able to make a sound weld on 3/16 tube any day of the week with either Mig or Tig. You are not going to break it with 500 hp in any kind of chassis. Don't forget you will have some kind of integrated roll bar/cage that will add emensely to the chassis rigidity, not to mention a pile of weight unless you use moly tubing.

I'm reassembling my hotrod in a racecar shop where they are building a FC with moly tubing according to SFI specs. It won't weigh much over 150 pounds complete and it be fully capable of handling 2500 hp every week end. The mate made over 100 runs last year and not a single broken weld pluss the car is 10+ old and the new car is better built than that one.

My street rod has 2x3x1/4 wall tube chassis and 450 hp at the rear wheels. I put over 1000 hard miles on it last year and nothing broke or bent.

By the way nice Cad models. SolidWorks?? If so why not run Cosmos on it just for fun. I have it but it is tricky to set up the restraints and there are too many unknowns for me to do it.