3 Link upper mount: need feedback

hey guys, I wanted to post this on here to see what I should do.
I built a beefy long arm crossmember with intentions to build a new Y link radius arm front suspension. Then the guts on pirate talked me into doing a 3 link and I went for it.

My LCAs are 39" long 2" square, and my upper is 31" and I wanted to mount it on the drivers side because there's a bit more room there & also, I built a truss... So I want to use it. There isn't much room to build a bracket on my crossmember because the driveshaft.. and I might be able to squeeze a bracket between the yoke & the transmission, but the transfer case linkage is in the way.. and I really don't want to try to move it.

My solution was a unique one, it was the perfect location for my link geometry.. And it also fit the length of my upper and was clear of any obstructions, so I went with an idea I had... And honestly it tubed out exactly as I visioned.

I build a 1/4 plate that conforms to side of the transmission tunnel, and build a bracket that mounts to this plate & protrudes through a hole in the floor from the cab. This plate is welded to the tunnel and bolts using an inner plate that sandwiches the unibody material between two 1/4" plates.. And bolts with 10 bolts and locknuts on the inside. Here are some pics:

Plate position while building, 8" wide x 6" high:


This is an unfinished pic of the bracket & outer plate, I added two triangular gussets on top the bracket reinforcing the attachment tonthe plate:


The bracket goes through the hole in the tranny tunnel and the plate will be welded with large tacks around the perimeter. There will be 10 1/2" bolt holes also drilled around the edge where the bolts will tighten against an inner plate sandwiching the sheet steel between the two heavy plates:


The inner plate I didnt take a photo of before install.. It's a frame, also 6x8" conforming to the shape of the tranny tunnel with the center cut out so it can slip over the bracket & then tightens down with 10 all steel lock nuts. Remember the outer plate is welded to the floor.. And bolts to this plate. Once tightened down & threadlocked.. It really created a strong & solid bracket mount fir my upper control arm in my 3 link:


From the front.. You can see the gussets on top the bracket in this pic. I hopped black RTV around the edge to seal it up.. And on the nuts to keep them from vibrating loose:


Here's a final top view. Again I sealed the edge.. This is a permanent fixture, so it will bedlinered over:



The Deal:
I thought this was an ok solution, but in my build thread on Pirate.. It's getting beat up pretty bad. I assure you this mount is very strong and I really want to use it.
People seem to think the unibody will rip apart? They think the floor will tear and be dangerous. The push & pull link forces are parallel with the sheetmetal..
I don't know what to do?

DO YOU guts think this will work?
Please don't put it down... Just let me know some honest feedback and advice. I'm not an engineer. Thanks

You are going to die.

Looks good... The only problem I saw were the square cut corners on your floorpan. It is usually better to drill the corners then connect the dots. The square cuts made a stress riser making the metal easier to tear. Other than that it looks good. More gusseting wouldn't hurt either.

i wouldn't trust that.

the unibody is known to crack around the tranny tunnel as is. now you have the tranny tunnel holding your axle in place. screw that.

The t-case linkage is the only thing stopping you from building a mount on the cross member?
Billy

If you make the plate on the outside about 3-5 times longer to spread out the forces to a larger area of the floorpan you should be alright. The mount you made looks pretty strong but it's attached to thin sheetmetal that cannot take the loads it will see and it will almost surely tear out when it weakens due to constant flexing. If you spread out the forces to a larger area then it should last longer. I would suggest extending the inner and outer plate back about 24" and then running some 2x4 tube from the inner frame rail under the seat to the plate and welding it up. I would also run some 1 1/2 X 1" from the frame rail under the floorboard to the bottom of the existing mounting plate. This will give you two places where the forces can transfer to the frame.
All that having been said, I recommend putting the upper link on the passenger side. There's much more room for it there and you can easily mount it to the crossmember, which is plenty strong enough to handle the forces. Of course you will have to significantly beef up the axle mount because the stock mount will rip off in short order with a 3 link. Good luck and please post up what you end up doing with it.

i personally would look into puting it on the crosmember and move the linkage. im startin to look at making my own las

I agree. I wouldn't trust it. It will work for...who knows, but heavy shearing forces will eventually crack the sheetmetal around the bracket. It would be a little safer to tie a cage into the top of that bracket, but obviously you don't want that right next to your foot.

I would make a mount off the crossmember and be done with it.

Like we said on Pirate, you're going to regret it down the road if you don't beef it up. BTW, everyone who posted about your UCA link mount on Pirate is also a member, and have built their own rigs, so you got some experienced comments. If you're really looking for advice, which I think you are, be sure to put more weight in the advice of guys who have fabbed before, and not some random comments from folks on the internet who haven't actually done it before.

Here's the weaknesses. The mount bracket has a flat plate on top, which is then welded along it's edge to the flat plate that sets againt the floor sheetmetal. While you have a gusset or two on top, that mount is still going to try to flex and has the potential to fatigue that weld and crack, especially at the leading edge.....at the front corner. The gussets that you put on top need to be at the front and rear edges of the mounting bracket, to ensure there won't be any flex against that weld, and to strengthen the weld at the ends/edges of the bracket. Then, I would box in across the top of the two gussets. Now you would have a mount that would last through anything you'd through at it over time. You'd be surprised how much force that single upper arm is going to take. I already ripped one off, that I thought was built strong enough, so I'm speaking from experience. Thankfully, I caught mine before it came off, so could fix it without incurring any damage, but if a 3 link mount comes off you're going to mess up some expensive parts.

Then there's the floor. I know that the two plates you have sandwiched together are strong, but that's not the problem. The whole mount, meaning all the force exerted on that arm, is held by nothing but sheetmetal. That thought alone, regardless of the beefiness of the bracket, is a problem. Just like cracks in the frame and body in other areas of the rig, the wiggle that you're going to get in the flor around that bracket will eventually cause the floor to crack and rip. You might as well fix it now, because you will be fixing eventually. Like others have said, the floor can crack in that area when there isn't a link mount attached to it, just from the frame flexing. My buggy is tubed with a pretty stout chassis and cage, but I still have that floor, and it's craking apart after two seasons of wheeling. I'm considering cutting the whole thing out. So, listen to experience, or listen to random comments.......you choose, it's your rig and your future.

Making it stonger isn't going to be that hard. I already commented on the bracket itself. To make it stronger against the floor, you can run a single plate from the crossmember to either side of the mount, which would add structure to share the load with the floor and should be strong enough. But, your driveline might not let you do that. What should be simple to do, and would also be strong enough, is to run a tube from the A pillar down bar of your cage, across the floor over to the plate on the inside of your mount. Add a couple small gussets from the tube to the plate to help with strengthening the weld joint. That tube would triangulate the forces using the floor sheetmetal as a shear plane while the tube keeps it from moving.

Give it a shot.

I imagine low axle ratios and lots of torque up front would tear that off.

Beef will be needed.

Props to you for trying out a new setup though.

Goatman said:

What should be simple to do, and would also be strong enough, is to run a tube from the A pillar down bar of your cage, across the floor over to the plate on the inside of your mount. Add a couple small gussets from the tube to the plate to help with strengthening the weld joint. That tube would triangulate the forces using the floor sheetmetal as a shear plane while the tube keeps it from moving.

Click to expand...

Not a bad idea...and probably a good opportunity to make some custom seat mounts, as well.

You don't have to take it as far as what I did:



although I will say that removing the trans tunnel and building a new one is one of my favorite things I've done to rig in the last year and a half.

I need to remove my whole floor, eventually.............and I'm not looking forward to it.

I don't want to work on it anymore, I just want to go wheeling.

FUGLY!!! That tin will flex and then crack.

Richard when was the last time you pulled out the old XJ? Sorry Off topic.

Mosephus said:

Richard when was the last time you pulled out the old XJ? Sorry Off topic.

Click to expand...

Unfortunately, it hasn't even started in over a year. This summer it's going to the Sierra's, and I just want to get it out and drive it around.

I'm having too much fun with the buggy.