matt1289

Please share some pics of how you or whoever welded your UMI subframe connectors in.

I've just about got the hang of welding fairly decent and want to practice the welds I am going to do before hand.

conan

iTrader: (5)

These are the only pics I have on my work computer, I could find some pics at home of the welding in the rear if this isn't what your looking for.

matt1289

Mine look a good bit different.

I did finally find this picture. Should I weld all the way around?

conan

iTrader: (5)

Looks like UMI changed the design a bit. My UMI's are 7 years old, 2009 is when I took that pic.

You can weld it all the way around if you like. Just make sure you don't throw too much heat at it all at once or you can start to warp things.

trackbird

iTrader: (4)

Remember, welding upside down is a different technique than welding on a bench (the settings in your machine may be too hot since they aren't typically for welding vertical or upside down). If you run too much heat you will have the weld run out of the puddle and drip (try not to be directly under it in case it drips...been there, done that...have the scar from it). Most of the time you want to stay with .035 diameter welding wire (or smaller) to get the puddle to "freeze" before it starts to run. Typically you need to stay around 100 to maybe 120 amps (on the hot end, if you can even go that high) to keep things cool enough to freeze the puddle while still getting penetration. You can always make multiple passes (in one exercise in class we were welding beveled 1" thick plates together running vertical welds from bottom to top at roughly 100 amps, you just keep stacking your beads and making sure they fuse into the metal below). Get some samples of material that are similar to your frame and the pads on your subframe connector (similar thickness for each material), clamp them together and try welding and then try welding them from below (hang them off the side of your welding table if you have one and can do it that way). Practice until you have it "down" and then go to work on the car.

I don't want to sound like I'm picking on Conan, I'm not. Since we are talking about techniques..... The first set looks to have been done with a series of "tack" welds. There's a crater in each one that tells me it was likely done with a mig welder as a series of single welds. Unless it was done for heat control reasons, the installer would likely be much better off laying down a single mig weld per side (or a series of "stitch welds about 1/2" to an inch or so long) than doing the single "spot" welds. MIG tends to start "cold" and it builds up heat as you weld (you can counter this by running the machine "hot" if it's a big enough machine). Starting over and over again isn't the best way to get good penetration (though heat builds up in the metal from the repeated welds and the pause between welds can be used to keep from burning through the thinner floor material). I'm not saying that those will fall off, they are likely on to stay. It's often done for appearance reasons and (if that is the case) it frustrates me when strength is traded for looks.

To answer the question on the second one, you shouldn't need to weld around the entire pad (other than it helps keep water out of there, you might make sure you goop any openings with a good coating of paint or something to seal it up). Those welds should be plenty strong (assuming good penetration). Most mig wire is 70,000 PSI tensile strength. It doesn't take a full perimeter weld to make things strong. There are strength benefits to minimizing the total amount of heat you put into the frame. So the stitch welds like you show are a good way to do a strong job that doesn't add a lot of additional heat to the joint.

My welding instructor constantly pushed me to "turn down the heat" and watch my heat input into my welded joints. I was always running things on the hot end and it took me quite a while to back the heat down and weld the joint with what was "needed" instead of what I wanted to do. He was always concerned with the total heat input to the joint and the "Heat Affected Zone" (HAZ) around the weld (the transition between metal that was heated while welding and metal that stayed relatively "cool"....typically this is where a proper weld will fail, not the joint, but the HAZ surrounding it).

If you're machine is set up with voltage and wire feed displays, try about 17.9-18.2 volts and approximately 200 inches per minute of wire feed speed with .035 wire and "drag" the weld instead of pushing (every machine is different, but try those and fine tune from there). That should get you about what you need to weld overhead.

Sorry that was so long.

I'm not a pro, but I'm a decent amateur. Your results may vary and people are always free to tell me I'm wrong.

matt1289

So the front mounting point for the UMI subframe connectors are 1/4 inch thick. The metal that they are welding to is only 1/8 inch thick... Well 2x 1/8 thick pieces in certain places.

What is the point in that? Not only do I have to overhead weld it. I also have to weld a 2x as think piece to the front subframe

Darth_V8r

iTrader: (4)

:word: welding upside down sucks

trackbird

iTrader: (4)

The thicker plate is more rigid. When you weld around the edges, the thicker plate will have the strength to not flex or bend nearly as much as it would if it was thinner material like the chassis. The chassis material will be more rigid than you might think because it's bent on the edges and that will make it stronger than a flat sheet of material.

Just point your mig gun/wire about 65-70% at the thicker plate and "wash" your weld to the chassis. You want to weld the joint between the materials, so you are going to weld the point where they touch (not "up on the thicker plate", weld the actual joint), just adjust the angle of your gun to put more of the heat and wire onto the thicker plate. Make sure you see the metal of the subframe melting/fusing with the bead. But you want to concentrate your heat on the thicker plate so you don't burn through the chassis and so you get enough heat in the thicker plate to actually fuse it together.

matt1289

I've been practicing a few weeks now. Starting to get the hang of it. How would these hold up? 1/4 welded to 1/8 inch steel overhead.

trackbird

iTrader: (4)

I'd like to see the back side of them. That will tell me as much as the front. Those are looking decent. The bottom one looks pretty decent overall, but I think I'd like to see a bit more heat in the thinner plate. Also, I see what appears to be some "undercut" on the thick plate. They are the little "divots" where the edge of the bead melts the base (original) metal and pulls it away from the plate that you're welding. You'll want a touch more bead/wire in that area to fill that. Watch for the corner to melt off the thicker material and then you should see the weld bead "replace it" (or weld right up to the edge as it melts). I don't have a good example, but I'll attach a couple pics that might help a little.

One is a tig weld on 1/8" stainless (two 1/8" plates together) and the other is a stick weld on roughly 1/8" plates. I should have brushed the stick weld better, but what I want you to see is the "edge" at the top of both welds. See how there's a fairly straight line at the top? There's no undercut, it would show up as "low spots". The TIG weld is actually even with or slightly taller than the edge in most spots. The TIG welded plate is sitting on the edge of a welding table, that's the other plate of steel under it that isn't welded. It looks like it wasn't finished. lol. These aren't perfect, they have some bobbles in them (I had hand and elbow surgery not too long ago and I was having some issues getting things to go smoothly).

The stick weld was run without weaving from side to side, just straight down the middle until the weld filled out to the size needed and as I saw the edge of the upper plate "break" (melt and the edge starts to flow into the puddle), I'd move. I just kept a speed that allowed me to watch the edge form into the puddle and the bead to stay the same size/size I wanted.

Do those help any?

dojob

Why did you go from using them as a bolt-in to welding them? Issues with the bolt-in?

infinitebird

iTrader: (11)

Well they are obviously a lot stronger welded but the bolt in is easier to install, so a lot of people bolt them on first and then weld later. I'm doing the same thing.

dojob

Absolutely stronger, i was asking with regard to creaks/groans, bolts loosening, etc...