How To Put Nuts Inside the Frame?

[jckkys]

I'm putting a '77 main fuel tank/skid plate on an earlier frame that doesn't have the 9 nuts welded inside the frame. My searches have only came up with rivet nuts. I also know later Fords used tapered self threading bolts where no weld nuts were present. These were used mostly to secure exhaust hangers to the frame. It seems a skid plate needs a strong anchor to withstand the weight of an EB sitting on a rock. What approach would be the strongest? Are there other ways to do this job?

 

[bronconut73]

BC used to have these long wires that coiled on the end so you could thread the bolt in the coil the fish the wire through the frame and pull it and the bolt through the hole....or something like that....it was 20 years ago for their fuel tank install in a buddies Bronco.

TBP uses a slick plate or bar with nuts welded into it for their hitch. You slide the bar in the frame and you have captured nuts that match the holes in the hitch where it bolts to the frame.

Just an idea...

 

[taipeichris]

Hi,

My exhaust shop guy offered me two different options when I had a similar problem.

Option 1.
1. Mark the desired hole with the outline of the nut you want to insert.
2. Drill it out just a bit bigger then the nut.
3. Thread a donor bolt into the nut, insert it into the frame, weld it into place.
4. Grind, paint, done.

OR

Option 2
1. Weld the nut on a flat bar (drill it first).
2. Cut a square hole in the frame.
3. Weld the bar with the nut on the back side into place.
4. Grind, paint, done.

I had this done when my threaded holes for mounting my two in one exhaust stripped out. He did a great job and you'd never know it unless you were looking for it.

I'm not a fan of nutserts. Over time they come lose and spin.

Good luck.

 

[jckkys]

3 of the bolts are in the rear cross-member so there is no access through the frame end. You can only get to the 3 on each side of the tank that are in the frame rails. I think I remember, after 30 yrs., that I used self threading bolts when I added the transfer case skid plate that the '77 didn't have originally. A restoration shop will be doing the bodywork and paint on my frame off. They may be able to do Chris's option 1.

 

[Broncobowsher]

I want to say the original bolts were self tapping.

 

[Broncitis]

I want to say the original bolts were self tapping.

No, the 77s have 9 weld nuts inside the frame.

I'd use 3/8-16 knurled steel rivet nuts.





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[904Bronco]

This is what he is talking about, 77 frame only...

 

[Broncitis]

Here's a stainless tank I recently made for one of our 77s that uses the 9 factory weld nuts for mounting.

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[Steve83]

Do it just like a hitch receiver. Tack-weld a stiff wire to the nut, bend it, and fish it through a factory hole in the frame to the desired location. Make the wire strong enough to prevent the nut from spinning 10 years from now. Or make a plate with all 3 that you can shove down the frame rail from the bumper end.

The ones on the crossmember don't need to be nearly as strong - they don't get any shear load. Use self-tappers there.

 

[Crush]

DANG Drew thats beautiful!!! How can I get one of those for my 77

 

[jckkys]

The frame rails are curved so a length of 1/2" thick strap would have to be contoured and bolted in itself. It is how I want to replace the top hold down nuts in the bed rail. I'm thinking none of the bolts have much need for pulling strength. 9 bolts can easily hold up a full fuel tank. The shear forces are only as strong as the stamped skid plate and rivet nuts are as strong as the bolt diameter. I'll use the original bolts for both strength and original appearance.

 

[DirtDonk]

I can't say it's the same thing dynamically as the transfer case skidplate, because they're shaped different and made from different materials. But I've literally anchored and pivoted by Bronco off of rocks on the t-case skid plate with no ill effects at the bolts.

All I did was drill and tap the frame for the bolts without adding any extra material.
Different too, in that the plate is likely heavier gauge (maybe?) and the bolts were pretty big at (if I remember) 7/16" coarse thread.

Good luck. What'cha building?;D

Paul

 

[Broncitis]

DANG Drew thats beautiful!!! How can I get one of those for my 77

Thanks!

This was the second one we have done, the first with this style mount for the 77 frame nuts.

I have a few things to tweak on the CAD drawing before i get more parts CNC laser cut and formed.

I do plan to offer these if there is interest. The way I designed it, they can be set up for intank pump or external. It is internally baffled and is all constructed from 12 gauge 304 SS. The welded joints are all overlaped with formed flanges so there are no butt welds at the edges. The overlap with formed flange gives a stronger double wall edge with a nice smooth radius.

 

[bronconut73]

Thanks!

This was the second one we have done, the first with this style mount for the 77 frame nuts.

I have a few things to tweak on the CAD drawing before i get more parts CNC laser cut and formed.

I do plan to offer these if there is interest. The way I designed it, they can be set up for intank pump or external. It is internally baffled and is all constructed from 12 gauge 304 SS. The welded joints are all overlaped with formed flanges so there are no butt welds at the edges. The overlap with formed flange gives a stronger double wall edge with a nice smooth radius.

Really cool.

Something that the vendors are not offering right now, besides the stainless is a slightly smaller capacity for a little more ground clearance. Like maybe a 17 gallon capacity.
Just some food for thought.

Love your tank Bud.

 

[Crush]

What is the capacity there Drew? and is it any closer to the axel than the stock tank/skidplate assembly?

 

[Apogee]

Thanks!

This was the second one we have done, the first with this style mount for the 77 frame nuts.

I have a few things to tweak on the CAD drawing before i get more parts CNC laser cut and formed.

I do plan to offer these if there is interest. The way I designed it, they can be set up for intank pump or external. It is internally baffled and is all constructed from 12 gauge 304 SS. The welded joints are all overlaped with formed flanges so there are no butt welds at the edges. The overlap with formed flange gives a stronger double wall edge with a nice smooth radius.

That's nice! FWIW, you may want to consider 316L stainless steel, as it should reduce weld porosity and the chance for leaks.

 

[sykanr0ng]

Thanks!

This was the second one we have done, the first with this style mount for the 77 frame nuts.

I have a few things to tweak on the CAD drawing before i get more parts CNC laser cut and formed.

I do plan to offer these if there is interest. The way I designed it, they can be set up for intank pump or external. It is internally baffled and is all constructed from 12 gauge 304 SS. The welded joints are all overlaped with formed flanges so there are no butt welds at the edges. The overlap with formed flange gives a stronger double wall edge with a nice smooth radius.

Could those be made with the mounting tabs lower as an option?
That would allow those with body lifts to tuck it up farther for better clearance.

 

[Broncitis]

Could those be made with the mounting tabs lower as an option?
That would allow those with body lifts to tuck it up farther for better clearance.

Yes, that was my plan

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[jckkys]

The skid plate/fuel tank support is only about 1/2 again as thick as the body sheet metal, so the 3/8" bolts are plenty strong with rivet nuts. The transfer case skid plate is much thicker. To answer Paul; I'm building a '77 "restoration"on a '68 frame, with a '68 title, and vin plate. My idea is building what a '77 Bronco would have been without government mandated emissions etc. I'm also keeping the '68 fold down windshield and removable door window frames. So running topless can leave only the role cage over the driver and passengers. I also prefer the T-shift transfer case, 2 speed + delay FJ40 electric wipers, '69 Mustang head rests, fender flairs, 351W and 31" tires on steel wheels with dog dish '77 F150 hub caps. These are all things I would have done in '77 if I had the $. Anyone buying a new '77 would have been happy to opt these few improvements, if they could have ordered them from Ford.

 

[ntsqd]

The way that I add threads where there is access is to weld an un-plated (or deplated*) nut to a tab that has a hole aligned with the nut threads. Then feed that into position and hold tightly in place with a bolt that has anti-seize on it's threads. Drill a large-ish hole thru the frame metal but not the tab. Rosette weld the tab to the frame thru the hole. Grind smooth.

That's nice! FWIW, you may want to consider 316L stainless steel, as it should reduce weld porosity and the chance for leaks.

Rule for welding SST is one alloy higher in the fill rod, so 316 would require 321 filler ($$$ & not common from what I understand). Just sayin.....

*A white vinegar soaking removes cad plating.