Cross-member Skid Plate

If you beef up the plate itself, consider bringing it out the frame rails. The crossmember can only carry so much without getting twisted up.
-Donny

 

James I had a 1974 cj5 and the previous owner made a skid plate that went from frame rail to frame rail and it was hecka strong. Heavier than hell to remove.

 

Strength-wise, it’s a wash. The brake might make a cleaner appearance, but... it’s a piece of steel designed to get beat up. And you have to trust/hope/pray that the guy doing it gets it perfect.
The benefit of piecing it together, you can form the pieces to fit together before welding it to ensure a proper fit (or near-proper after warpage/shrinkage). It’s a good place to practice welding!

If going all the way out to the frame rails, I might suggest coming up the sides of the frame (U-shaped skid plate) so your mounting bolts are less likely to see rock rash. Nothing worse than a skid plate you can’t remove. Weld nuts inside the frame rails so you won’t have to be a contortionist to hold a wrench on one side and a ratchet on the other.

 

The base metal (frame) will suck the heat out of your weld long before the nut will. Bolt the nut in place (preferably with the bolt flush with the end of the nut so spatter doesn’t mess up the threads of either), start the weld puddle on the frame next to the nut, then sweep the weld over to the nut for a split second. Repeat 2 or 3 more times around the nut. You’ll want the welder set to a heat that you would use to weld the frame, not the nut. Also, most nuts are coated with a zinc or other galvanizing, so remove that first to prevent impurities. Practice, practice, practice before you move on to the real thing.

The only advantage a flanged nut has over a standard nut is the extra material between the weld and threads. Possibly easier to weld, but a little harder to remove all the coating.

Another notable pointer... the last weld will be more apt to melt the nut than the first weld was, because the nut has been thoroughly preheated by the first welds. Just be aware.

 

Yeah, I like to weld hot. Spot welds on thicker steel don’t have time to build a lot of heat if the settings aren’t high enough; you’ll just get a blobby deposit with no penetration. Just enough heat to melt the wire, but it’s not mixing with the base. The edges of the weld should show a flow into the base metal, not a 90° edge where the weld meets. You should be hot enough that you’re more worried about melting into the threads of the nut than not getting cohesion.

 

McMaster-Carr

 

It would also be a good application for Nut-serts if you didn't want to weld them.

 

If I can help I have access to a CNC plasma table at the local makerspace if you want to design something new and make a prototype.

 

I welded nuts on the B and then made an isolator type connection (so the engine mounts can still flex) to the rear of the engine pan skid plate to get some fore-aft stability. I used 1/4" 6061.

 

Here's my crude but hopefully effective skid plate.





I reinforced my cross member like so. I did bend the front and back edges up on the skids hoping to reduce the spatula affect. I didn't take a pic of that yet. No idea if this is any good yet, but it was simple which is always good





I'm also working on another narrow one that runs down the center under the oil pan. I watched a video where "Bam-Bam" rolled over and saw he had a cool skid down the center.

 

Looks like a good application for button-head allen bolts.
-Donny

 

countersink drill bit and you're in business..
I have been debating making something for my CJ6 and this thread just inspired me..

are you going to notch for driveshaft? drain holes?

 

I don't need any notches for driveshafts but I do need holes to access drain plugs. I've been hesitant to countersink those bolts, seems like it would weaken it a bit. Probably be fine since that aluminum is so thick.

 

For welding in nuts I use these. You break off the spring and they work fantastic. Oversize foot print and maybe 50% thicker than a nut. You can get them from Lowe's, Home Depot or an electrical supply house. They are used for Uni Strut. You can get 1/4" to 1/2".

 

Oh, I have boxes and boxes of those at work, never occured to me to use them as captured nuts.

 

Here's the bottom of BamBam.



I am making a similar skid plate under the oil pan on mine. I have a flat piece of steel that will mount to the frame and a vertical piece that goes up to a motor mount to give the flat piece strength. The plate that goes under the oil pan will bolt to the flat piece and tie in to my crossmember above the plates that are already there.