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You could always take some flat stock and weld fasteners/threaded cylinders to the strap. Drill the bottom of the frame to clearance holes for the fasteners and then weld the perimeter of the strap to the bottom of the frame. You would only have the thickness of the flat bar added to the overall height of the frame rail.
 

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Discussion Starter #162
You could always take some flat stock and weld fasteners/threaded cylinders to the strap. Drill the bottom of the frame to clearance holes for the fasteners and then weld the perimeter of the strap to the bottom of the frame. You would only have the thickness of the flat bar added to the overall height of the frame rail.
Yeah. I have thought about something similar. Depending on where the final frame height ends up being, I would not be against dropping the belly 1-2". The one thing that would really do is help smooth out the transition to the rear control arm mounts. That 'bump' concerns me a bit.

My twist on that idea when I was thinking about it was to weld some 1x2" channel to the bottom of the frame with the so it was like a U shape. Drill holes in the bottom, then leave one end open enough you could slide in 'nuts' that where square and just fit in the bottom. Use something like 3/8" thick stock so the thread length would be ok. The square nut wouldn't spin and you wouldn't need to hold it. If you did strip one or break the bolt off it could be replaced.

The frame is already 6" tall however and theFJ tub is pretty tall to the cowl. I don't think I will 'need' to make the frame any deeper unless I end up sinking body all the way down so the floor is touching the top of the frame.

Good ideas though, keep them coming.
 

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I mention using threaded cylinders because you could use a thick wall cylinder and when you have a failure of the thead simply drill and tap to the next size up. It gives flexibility for fixing a failure if the threads are damaged. I have done this before even with a commonly found nut that had enough meat in the wall.
 

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Are you planning on the cross member mount being separate and this skid plate covers it or the skid plate is part the cross member?
 

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Discussion Starter #165
Are you planning on the cross member mount being separate and this skid plate covers it or the skid plate is part the cross member?
I very much want the skiplate to be able to be dropped WITHOUT having to support the transfer case or transmission. I want the vehicle to be fully functional without the skidplate in place if it was damaged or crushed. For finding leaks. Or for diagnosing cooling issues.

The LT230 transfer case I am planning on using seems to use mounts out near the frame, basically like engine mounts. It has one on each side.

The 6l80 transmission uses a typical GM style transmission mount under the transfer case adapter.

I wouldn't mind being able to use all of the mounts....two engine mounts, one transmission mount, and the two transfer case mounts. It would be nice if everything was well supported.

The crossmember for the transmission center mount should probably go side to side completely and provide enough support for not only the transmission and transfer case, but also be stout enough to turtle the entire vehicle on with no deflection. The belly skidplate should probably bolt to that crossmember. That crossmember should also be somewhat easy to remove if the transmission needs to be removed. It would need to clear the exhaust, front transfer case output, etc.

Then have a mount for the front off the engine mount cradle. I would need another one at the rear if I extend the skidplate towards the rear axle. There is a large crossmember for the upper rear control arm links in about the right location.

It would be nice if the belly skid plate could be replaced/replicated easily if needed. I wouldn't mind if I could stick it into CAD and just have a new one waterjet cut when I wanted in the future. If the skidplate was totally flat with no other work needed that would be best. Making one with a jig saw, some hole saws, and lots of WD40 shouldn't be too big of a deal. I will probably make a template out of some plywood or something anyways before I start cutting lots of expensive aluminum plate.

Jalbrecht47 had a neat idea. He mentioned that one side of the skidplate should fit into a tap/slot/pocket so it would be a little easier to stick up under the car, or drop, by yourself. This could be the front, back, or a side.
 

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We have limited seats of Autocad so I cant give you a picture. If you have a flat plate you could weld nuts to the flat plate on the four corners and then thread a SHCS into the nut until it bottoms on the plate. Now you have four "tabs" sticking up toward the frame. you would have four open ended slots made from flat bar. They would all be open on the the same end, ie toward the front or toward the back of the car. Once you lift the plate into position you just slide the plate until the slot is around the shank of the SHCS. Release the plate and the head of each SHCS hold the plate up in position with a small gap to the frame. Now you can hand thread the bolts that hold the skid plate up.
 

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We have limited seats of Autocad so I cant give you a picture. If you have a flat plate you could weld nuts to the flat plate on the four corners and then thread a SHCS into the nut until it bottoms on the plate. Now you have four "tabs" sticking up toward the frame. you would have four open ended slots made from flat bar. They would all be open on the the same end, ie toward the front or toward the back of the car. Once you lift the plate into position you just slide the plate until the slot is around the shank of the SHCS. Release the plate and the head of each SHCS hold the plate up in position with a small gap to the frame. Now you can hand thread the bolts that hold the skid plate up.
 

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Discussion Starter #168
We have limited seats of Autocad so I cant give you a picture. If you have a flat plate you could weld nuts to the flat plate on the four corners and then thread a SHCS into the nut until it bottoms on the plate. Now you have four "tabs" sticking up toward the frame. you would have four open ended slots made from flat bar. They would all be open on the the same end, ie toward the front or toward the back of the car. Once you lift the plate into position you just slide the plate until the slot is around the shank of the SHCS. Release the plate and the head of each SHCS hold the plate up in position with a small gap to the frame. Now you can hand thread the bolts that hold the skid plate up.
If I use something like 7075T6 aluminum I can't weld to the plate, but I can visualize what you are talking about.
 

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You could always use a structural adhesive as used in modern auto manufacturing or even a 2 part epoxy. The mechanism for hanging the skid plate could be designed as to not see any loads after the plate is attached to the frame with counter sunk screws. If it is aluminum how heavy would a plate be that spans the frame rails?
 

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Discussion Starter #170
You could always use a structural adhesive as used in modern auto manufacturing or even a 2 part epoxy. The mechanism for hanging the skid plate could be designed as to not see any loads after the plate is attached to the frame with counter sunk screws. If it is aluminum how heavy would a plate be that spans the frame rails?
We can't forget that area is going to get pretty warm with the exhaust, transmission, and transfer case. Adhesives and glues may be ok, but could be marginal.

A full 4x8 sheet of 1/4" plate 7075T6 aluminum is about 117lbs. If I end up using 50% of the sheet area I would be pretty surprised. So the belly skidplate would be about 50-60lbs total.
 

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Here is how I did mine. The horizontal holes on the frame are sleeved with tubing and a nut is welded on the inside so you can use one tool to install the bolts. No bolt heads to counter sink or bash up and you can just slide the bolts in position to hold the weight before actually threading them all in. Seems to work great, but my aluminum sheet is all second hand scraps. Should be easier for you starting with new sheet.
 

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Here is how I did mine. The horizontal holes on the frame are sleeved with tubing and a nut is welded on the inside so you can use one tool to install the bolts. No bolt heads to counter sink or bash up and you can just slide the bolts in position to hold the weight before actually threading them all in. Seems to work great, but my aluminum sheet is all second hand scraps. Should be easier for you starting with new sheet.
and you get to carry a drip pan everywhere you go so you don't have to park in the street at a bud's house. :flipoff2:
 

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Discussion Starter #175
Another weekend in the shop....

I've been scratching my head for a few weeks on how to 'pinch' the door openings while leaving most of the floor intact. This is what I came up with.





This is the passenger side cut being planned out. I measured the taper of the body and made a paper template. I swear the tub has a metric angle :shaking: I decided to go with a 6 degree cut to start out. I think the taper is more like 7 degrees but I would rather trim a little more than have to fill a gap....

Poster board is good. Little magnets to hold the poster board are good. Big magnets to hold an aluminum ruler are handy. The pivot point is the outside corner of the door. That means I have to take about a 3/16 section out of the inside panel of the door to allow things to move right. Before I get to that.....I needed to prep the underside of the tub....



I had to identify any spot welds that where on the outside area of the hat channel. They would get in the way of the floor/door sliding as they move. I also needed to remove about 1.38" of the hat channel to allow the door to move into the new position.



Once that was finished off I could move to the prep at the bend in the door opening area.



The cut on the outside wasn't too bad. It just required a steady hand with a grinder.



This cut on the inside was a total pain in the rear. This gap will close about 3/16" an inch when everything moves. Cutting down into a 3-sided corner was REALLY difficult. I used just about everything from a grinder, to a dremel, to a hand saw, and a hammer/punch. It kicked my butt.

Now I need to move back to the other side and do it again. I found that if I drilled a 1/4" hole in the bottom of the corner that helped start things off right. Finding something to cut down into the bottom has been challenging. I tried a oscillating saw but the blade only lasted a few cuts. Maybe its time to buy a plasma torch? Maybe a roughing end mill in a high speed drill? A body saw might get down into the corner a little bit. I just don't know.

Once the 2nd inside corner is finished I should be able to stick the dang thing on the table for the actual 'pinch'

After taking MANY more measurements I have determined the body will be 55.5" wide when finished now. That will be about 1.5" narrower that the back of a flat fender tub, and 3.5" narrower than a CJ5/7/YJ/TJ tub. The dash area will be the same 55.5" wide, which is bout 4.5" wider than the dash on a flat fender so the foot well shouldn't be as cramped as an early universal jeep.

That is all I have for now, hopefully more soon.

Fun Fun
 

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Discussion Starter #177
I thought o understood what you are doing. ( pinching ) what exactly is that?
The tub on an FJ40 is tapered all the way to the back of the door opening. The width of the tub at the dash is approx 55.5" wide. The width behind the door is about 63.5" wide at the point where the tub becomes parallel.

In the factory design the doors are not parallel to each other.



Here is a blueprint style drawing of the tub. You can see how the chassis is not at its widest point till behind the doors.

I am taking out the taper from the front of the door opening back. This will make the widest point of the tub about 55.5" wide. Then I will build a framework ( that will also be the cage ), and skin it, to form the rear part of the tub from behind the door opening back.
 

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Discussion Starter #179
I got the 2nd side done in like 1/10th the time of course....



I used a 1/16" disc for the top cut on the outside of the body in the door seal area, but I switched to a 1/8" thick 'cupped' cut off wheel to do the inside cut. This gave me a nice wide slot to start with on the inside.



Then I FINALLY found a way to make the cuts I couldn't get to with the grinder. I drilled a 1/4" hole in the bottom corner on the inside wall before making the last cuts. Then I used a LONG thin sheetmetal saw blade to make two cuts on the inside that added up to about a 3/16" gap. The long blade made it possible to reach the bottom at the right angle without hitting the bottom panel or outside wall.



Next I made these little cuts with a small wheel on a Dremel tool. This little area will get 'displaced' when everything moves. I was able to drill 'down' through these two little tabs so they would break off after they where pried up with a screwdriver.

In the end it ended up looking like this...



That gap will close when the door moved and I will weld everything back up!

Time to get this thing on the table...
 

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Here is how I did mine. The horizontal holes on the frame are sleeved with tubing and a nut is welded on the inside so you can use one tool to install the bolts. No bolt heads to counter sink or bash up and you can just slide the bolts in position to hold the weight before actually threading them all in. Seems to work great, but my aluminum sheet is all second hand scraps. Should be easier for you starting with new sheet.
I've not build skid(s) for my willys yet, but I like how you mounted these. No bolt heads or countersinking! I think I'm going to steal your idea :D Though mine probably won't cover near as much as the underside as yours. And my transfer case is not QUITE flat with the bottom of the frame, so I'll need to make a gradual hump for it. I'm thinking about making mine out of aluminum, so I can get some aluminum TIG practice.
 
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