Customs 51 Dodge/Fargo on dakota frame (boxing/crossmember suggestions)

my old thread won t let me post so here it goes. Building a 51 dodge of a dakota frame that i shortened. The dakota frame had some heavy scale being on the east coast but otherwise ok but i m still worried about the amount of flex it has especially after removing 2 of the original cross-members.

Looking for some suggestions on cross-members or frame boxing. My plan was to build a crossmember between the 2 fish plates i used after shortening the frame and from the center of that go back like a k member. I also have to ad 2- 1 1/4" tubes to the very back to mount the gas tank then box the rear of the frame, but after reading on boxing im concerned about fatigue and stess cracking. I just want a solid truck. no high hp or track time just a tight street truck.

 

Why did you remove the crossmembers that were there?

You need a crossmember at, or very near, the front leaf spring perches. That crossmember needs to be bolted to both the top frame flange and the bottom frame flange on both sides to keep the rails from rolling under the load of the springs. That crossmember also has to allow for the drive shaft and its movement. Your rear most crossmember needs to be near the rear leaf spring perches, and it also needs to be bolted to both the top and bottom frame flanges on both sides. Bolt rather then weld will allow some movement of the frame rails and that will reduce the chances of stress cracking. There needs to be 2 bolts at least 3" apart on both the top and bottom frame flanges for both crossmembers, and those bolts need to be a 3/8" diameter grade 8 bolts.

The tubes your adding to hold the fuel tank can be welded to the vertical portion of the frame rail, be sure the inside of the frame rail where your welding is clean shiny metal. I see no need to box the rear of that frame. The bolt in crossmembers will add a lot of stiffness to that frame. Gene

 

Modern frames flex. A lot. Especially the cars and the small pickups, which use very similar frame designs as the last body on frame cars. That's why originals tend to be superior to them.

 

I'm curious why you didn't split the frame just forward on the factory splice, shorten and reweld?

 

I had to remove the farthest rear crossmember to fit a jeep gas tank between the rear frame rails. The other one was not much of a cross member rather than an exhaust hanger although I'm sure it did it's part.

I shortened it were I did not knowing how or if I could seperate the factory splice without making too much mess. I seen a few Dakotas shortened and for the most part did it the same

That crossmember location makes sense. And bolting it makes even more. Maybe I'll mock something up and take a pic.


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Excuse my krude mock up. Hahaha.

This it the crossmember I removed. I want to eliminate both of these. Mostly for aesthetics. And maybe alittle more rigidity.

The tape of course being made from 1 5/8" dia steel. Instead of welding what about another "C" bolted on the top and bottom flange of the frame. My thought is the "K" member will still allow some twisting.


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Oops. Here's a pic


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No thoughts?


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Looks like that will work, as long as your tied to both the top and the bottom of the rails on each side. If you don't get both the top & the bottom, you run the risk of cracking or breaking whichever flange you choose to mount to. The leaf springs cause the frame rails to want to roll in when loading, and roll out on cornering. Attaching both the top and bottom flanges to the crossmember helps keep the rails from rolling.

There are a couple ways to accomplish this.
1) Add "wings" or flanges to the ends of your crossmember so you can bolt into both frame flanges directly above & below each other on both ends of your crossmembers.
2) Make your crossmember ends fit between the top and bottom frame flanges and bolt to each flange and to the rail side at each end of your crossmember. Make sense? Otherwise, I can try to use my artistic abilities and my computer abilities (both phrases used loosely) and try to give you a picture of what I mean. Gene

 

Yes I think I got it. Your help is appreciated. As far as the gas tank goes, the flange/seam of the gas tank sits tight to the bottom side of the frame rail. Instead of welding the tube between the rails on the bottom of the frame I'll connect the tubes with flat stock and bolt them through the upright part of the rail. Sound better?


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Your other thread was closed...per the forum rules/guidelines;