Builds 86 Xtra Cab Build (4Wheelunderground 3 link front, 4 link rear and 3.4 swap) (4 Viewers)

[aztoyman]

There's no tubular part inside that stamped section on the driver side. (If I properly understood your suggestion) Pretty sure anyway because these parts are bare steel from the factory and I saw inside it when I sprayed it down with phosphoric acid to get rid of the rust. I'll take another look at it though in case I'm wrong. I think the one from my spare cab is in my shed. I hope it is, if not it's about an hour away at my buddies place.

But either way, It needs to be stronger and I think you have a good idea about running the tube through it or somehow merging/blending/welding the stamped part to the new dash bar to keep the attachment point for everything in place. The passenger side would be just the new dash bar tube continuing across. Eliminate the thin original section. I think I would still tack the small attachment points for dash structure back in place. Including the tie plates bolted to the cab. THANKS!

 

[aztoyman]

I got a chance to look at the dash bar situation today and decided to just pull the factory sheet metal one out. The one I need to weld in needs to be in the same space. I'll just add brackets for the steering column and all the other mounting points for pedal return springs and A/C ducts.

@littlevulture The factory dash bar is pretty much sheet metal halves spot welded together on the driver side and the passenger tube is spot welded on the end of the driver side section. Doesn't go across. Cutting it up to merge the two isn't something I want to try. I may steal the column bracket off it though.

 

[aztoyman]

Right about the time I was cutting my piece of DOM for the dash bar, a sudden and pretty nasty monsoon storm hit. I was determined to at least get it fit up but I didn't get to clean it up yet. I was ready to spray it down with phosphoric acid when the rain hit.

Looks like I have some serious dash mods to do. I have no idea how all that will work out.........yet.

 

[littlevulture]

View attachment 3974821

View attachment 3978430

Looks like I have some serious dash mods to do. I have no idea how all that will work out.........yet.

What am I missing here...comparing your pictures it looks like it slots in exactly where you need it to be so not much dash mods needed?

 

[aztoyman]

I'm still thinking about how I'll be welding this sucker in. Pretty sure I'll either have to cut off the roof (Oh PLEASE no!) Or cut the cage and sleeve it.

I originally thought this spot marked in red would be best as far as having good welding access to weld it back together. But now that I have the dash bar, I'll need to get to those joints too. I think the area marked in yellow is my best option if I end up having to cut it.

I really won't know for sure until I get all pieces cut and fit up, including gussets.

 

[aztoyman]

@littlevulture , it fits pretty close but the tube is larger diameter so kind of interfering with A/C ducts mainly. I'll be trying to get all the plastic in place after cutting it for the A-pillar tubes and modifying the dash top to move the two outer vents inboard of the tubes.

I think I'll either be making a new dash top or using foam and fiberglass to modify it like a bunch of YouTuber's have done to fix the cracks.

 

[Lucille]

Stepping down to 1.5" for the dash bar isnt the end of the world if that helps things fit better. Could you cut the old bar apart and weld the tabs/brackets onto the new dash bar? That would be the easiest i think to get everything lined back up. I snuck my dash bar in but it resulted in my gauge cluster not fitting. Had to go with digital display on an old tablet.

 

[aztoyman]

@Lucille, Yep, I could probably salvage tabs and brackets off the old brace. I have a stick of 1 1/2" tube if it ends up being needed. I'll git'r done one way or another.

 

[aztoyman]

I dinked around with the factory sheet metal brace to see if I could run my 1 3/4" tube through it or if I should just pull what I needed off it. Maybe if I had a way to scan it and mark where to modify it I could have. I don't have those skills or tools so I drilled out the spot welds and took it apart. Basically a top and bottom half with the thin tube to the side.

I was able to bolt the bottom half in place between the cab attachment points and the brackets from the trans tunnel up where the HVAC controls and radio go. This let me put the new dash bar in place and tack weld the lower half of the factory brace with all the mounting points in the original positions. Then I pulled it all so I could trim off what wasn't needed and keep what had to stay.

So now my steering column mounts, parking brake lever mount, pedal return spring mounts and all necessary stuff is where it originally was. Next, I took the worst plastic dash structure that I have (of 3) that needs to go in next. So I could trim it to get around the A-pillar bars and dash bar. I originally thought this was do-able. Maybe it is, but I don't think it I'm going to try to salvage this plastic dash. The dried up and cracked dash pad won't sit where it needs to without a lot of trimming either.

So I'm going to keep plugging away at the roll cage. I'm not going to sacrifice safety to keep my dash. I'll maybe take another look at it another time but I'll most likely fabricate something. Everything still plugs in and still works otherwise.

The cage back stays will have to go through the rear window opening so that's the next obstacle. The opening on these 84-88 Xtra-Cab's are much larger than the standard cabs so there's not much sheet metal between the roof and the top edge of the window to run the tube through.

I warned my wife a while back that this cage was going to be a challenge and I told her I'd rather not install one. She insisted and after seeing some videos and watching some friends roll, I think she's right.

Anyway, you deserve pics after reading all that.

 

[aztoyman]

Here's a pic of my GOOD back window. I'm NOT butchering this one. I have another one I can modify to run tubes through.

 

[aztoyman]

I took this window apart instead. It's had attempted break ins and it's a bit rough all over. I can either put in one piece of polycarbonate in the gasket or in the frame, or two small pieces of polycarbonate, one on each end. I think the later is the better option.

 

[aztoyman]

Because the back stay tubes will come off the top of the main hoop, through the window here and either down to the bed floor above the bed to frame mounts. OR, if it's ok to run them to the shock towers I may do that.

 

[aztoyman]

Being as I have the cage bolted to the cab and the cab is on body mounts, I don't know if it's ok to attach the back stays to the shock hoops. Still looking into that. Speak up if you have an opinion on that.

The back stays need to come off the top of the main hoop, be straight and angle at least 30 degrees from horizontal. That's where I'm at if I go straight to the bed (mounting plates) directly above the bed mount. Right in front of the fender well.

And for those that are asking why I don't drop the cage through the floor. This is looking up at the body mounts. The red circles are where the tubes are. To add, My original plan was mount DIRECTLY OVER the mounts. Had to move them outboard mainly so the sill bars align on plane with the main hoop and A-pillars.

Today I was watching babies so all I got done was two tube gussets cut, notched and cleaned of rust and mill scale. Maybe tomorrow I'll have more time.

 

[ntsqd]

I'm not sure why the 30° requirement. Force flow thru the cage is more important. I would put these tubes so that they feed the shock mount loads into the rest of the cage directly, no disjointed flow of those forces.

Given that the cage is bolted in I'd use 'Hega' Joints at both ends of these tubes to allow some compliance without risking fracture or cracks. That means that the tubes want to exist entirely outside of the cab. The whole cage & chassis assembly is going to flex and if these tubes go thru the window or the sheet metal there will need to be some sort of flexible seal (shifter boot?) to allow the relative motion without leaking or squeaking.
Instead of going thru the window they could terminate into box structures at the back of the cab that perhaps are bolted thru the cab sheet metal or thru an insert in the window to the cage structure inside the cab.

 

[aztoyman]

@ntsqd I'm not sure why the 30 degree minimum. It's just been consistent in all the cage design rules I've managed to find.

I've read a few questions to the scrutineers/tech inspectors from guys with pickups not really wanting bars through their cab or rear windows. Asking about options like bends in the bars, or running them to the horizontal bar instead of the top of the hoop or if they REALLY NEED them.

The replies were that without them, the cage could "parallelogram over" / collapse in. Some classes allow a "Petty bar" in certain circumstances on an individually approved basis. Some classes allowed no back stays if they met this list of SFI rules. I looked them up and it was basically a funny car type enclosure around the driver. So basically install a proper set of bars as per the rules or don't pass tech.

I don't have to pass tech, but It sounds like they are necessary for a safe cage.

I looked up the "Hega" joints mentioned. If I understand correctly, they are a bushed tube to cushion a welded connection between the bottom of the bolted floor plates to the frame. They are sold as frame tie in kits. Sounds like a great idea and then I stumbled across a "disagreement" between an engineer and maybe another engineer?? Anyway, the one guy said it does isolate flex and vibration but in a crash would behave as a hinge and not a ridged mounting point.

If true, could you just add a second tube and bushing parallel to the other tube? If both ends of the tubes are welded, two parallel mounts can't pivot.

I also read a few "disagreements" about cages being welded solid to the frame vs bolted to body. Race inspectors said welded to frame is always stronger, but bolted or body mounted is acceptable as appropriate for the class. NEVER both. There's enough gray areas to make your head spin.

 

[ntsqd]

I'm confused now, does this rule say no more than 30° or no less than 30°?

Can attach the cage to the cab if the cab and the cage both 'float' i.e. are not welded to the frame. It is already bolted to the floor. Bolting it to the cab in other places shouldn't be a problem, and will have the cage and the cab moving as one structure.

A Hega joint is a hinge. Why is that intrinsically bad? If the cage and cab are soft mounted to the chassis then rigidly mounting those tubes is a very bad idea. They are very long tubes, so they have a lot of leverage on the welded joints. When loaded in compression they are subject to the Tall Column Failure/Buckling mode due to their extreme aspect ratio where they are likely to bow or elastically bend, which will severely stress the end welded joints without a Hega or something like it being there. Using a Hega joint there preserves the functionality of what those tubes are supposed to do without risking the perpetual cracking that welding them solid will result in.
Look at how trusses, both for bridges and for houses are designed. If all of the cage is rigidly mounted then it needs to follow the truss design rules. When they aren't rigidly mounted then nothing can be rigidly mounted and the design needs to allow for relative motion without compromising the structure.

Loads should always be fed into nodes of the cage, not into the middle of a tube's span between nodes. If you have an 'X' in the door opening and a cross-tube behind the seats at where the upper-rear 'X' tube meets the main hoop, then those diagonals could be connected at that node. It won't be quite as strong and it does leave open the possibility that the top part of the cage could parallelogram in an accident, but it's far better than attaching them to the middle of the main hoops span between that node and the node where the halo or top tubes meet the main hoop.

 

[aztoyman]

@ntsqd Sorry, Here's a quote from NASA-Rally Sport cage specs "The backstays must be attached near the roofline and near the top outer bends of the main roll bar or lateral roll bars, on both sides of the car. They must make an angle of at least 30° relative to a vertical plane, must run rearwards, must be straight, and be placed as close as practical to the interior side panels of the body shell. Although not required to do so, the backstays usually connect to the rear strut towers."

My cab mounting points are all in the cab but the bed is a separate unit. I "thought" I should stay with the same method of connection to the bed as I did in the cab. Plates bolted to the floor over the mounts. Running my back stays from the top of the main hoop junction point and using a straight bar to that base plate is right at the minimum 30 degrees. So it meets spec so to speak.

My question was, would it be ok to weld it to the shock hoops? The shock hoops look like a better location. Straight back and not as steep an angle as going to the floor of the bed. Or would that be a problem since the hoops are welded solid to the frame? The bed itself seems to be more solidly mounted than the cab. There are I think two similar mounts as the cab but smaller and the rest are just thin rubber squares between the frame and bed that the bed bolts pass through.

As far as the engineer's discussion over the cab tie in's, it got WAY over my head. I'm mainly just pointing out how overwhelming and confusing this can be for the average gear head like me.

I do realize I need clearance around the tubes passing through the Lexan window panel. I'll boot it somehow.

 

[ntsqd]

Had to scroll back thru the thread to refresh my memory of the rear shock mount geometry. Found post #1864 with a good pic of it. I wouldn't land the back-stays on the shock towers. Too much of a parallelogram that will flex. I'd land them on the top of the frame rails where that doubler strip is over the cross-member that the front ends of the shock mount tubes tie into. Want to form a triangle with these: main hoop, frame rail, and back-stays. Tying in anywhere other than the frame rail adds a fourth 'leg' to this and will allow flex that will be working the welds every time that it does flex. I would use a Hega Joint at both ends with the bolts placed horizontally. As close as the main hoop is to the rear wall of the cab can you even hit the node of where the halo meets the top of the main hoop? Looks like you'd need to notch the window opening up to get there.