Built a crossmember for my 4 link front today...

[Boostwerks.com]

...Overall it turned out pretty good. I will need to massage the floor a little for the UCA mounts, but should result with a little better geometry than the 4 link kits on the market. From my rough measurements my anti-squat is around 65%.

Specs:

2x6 1/4" tube fish mouthed on both ends
1/4" plate sides with 8 13/16" holes
1/4" UCA brackets
1/2" LCA brackets (little overkill, but will last longer over rocks)

It will attach to the rig with 8 5/8" AVK nutserts. The AVK's are inserted directly to my ruff-stuff stiffeners, which will make the entire setup very strong. The UCA's will consist of 5/8" heims and 1.25" .25 wall DOM. The LCA's consist of 7/8" heims with a 3/4" ball and 1.5" .25" DOM.

I thought i'd snap some pics before it's painted flat black tomorrow.

Let me know what you think. I'll be building the links next weekend, so stay tuned.

Thanks,
Bryson.

 

[downhillracer]

Damn... thats some nice work.

 

[vetteboy]

Fab work looks nice, but I'm a little confused on your geometry...

From the angle of the tabs it looks like you're still planning on having 4 links plus a panhard. Realize that a parallel (or close to parallel) 4-link setup builds in the same inherent binding that radius arms have, for the same reason...the axle movement is overly constrained, and you've got the left and right links fighting each other for pinion control over travel.

Using bushings helps band-aid the binding as they can 'squish' in a way that a flex joint can't, which is to effectively lengthen or shorten the link length to allow for the axle to rotate properly. Without that movement the axle is going to want to twist in the middle.

Your crossmember is stout enough to run a 3-link with a panhard; why not do that and have a setup with no binding at all?

 

[RCP Phx]

Looks good so far,but Im trying to figure out what you doing at the t-case mount(pics 3,5)?

 

[jdxj]

LOOKS GOOD TO ME Damn good

I think he's goint to mount the tcase in the recessed part of the CM that will lower the tcase without lowering the theCM

ITHINK

 

[RCP Phx]

I hope not,for strength and sealing purposes.

 

[XJ[4x4]77]

those are some nice ass welds! looks good! i would like to 4 link mine but am afraid i lack the welding experience

 

[whitneyj]

I hope not,for strength and sealing purposes.

what do you mean?

 

[Hammered]

Dems some nice welds right there.

 

[RCP Phx]

what do you mean?

By cutting that big box out totally destroys the stregth of the tubing.And I always want "zero" places for mud/moisture to gather(sealed crossmember).

 

[whitneyj]

ahh. . . gotcha. Even with the 1/4" plate that the tranny/tcase mount bolts to, you're worried that's not strong enough? The stock xmember is no where near that strong.
I agree with the mud/moisture collector.

 

[CanMan]

Looks good so far,but Im trying to figure out what you doing at the t-case mount(pics 3,5)?

He's probably took into account that the stock X member sits that low, and his new one sits highter, hence having to cut out the box tube so the TC/Trans/Engine sit horizontal in the vehicle like it would with the factory X member.

 

[RCP Phx]

ahh. . . gotcha. Even with the 1/4" plate that the tranny/tcase mount bolts to, you're worried that's not strong enough? The stock xmember is no where near that strong.
I agree with the mud/moisture collector.

The stock crossmember doesnt have any let alone 4 links mounted to it !!!!

 

[Boostwerks.com]

Fab work looks nice, but I'm a little confused on your geometry...

From the angle of the tabs it looks like you're still planning on having 4 links plus a panhard. Realize that a parallel (or close to parallel) 4-link setup builds in the same inherent binding that radius arms have, for the same reason...the axle movement is overly constrained, and you've got the left and right links fighting each other for pinion control over travel.

Using bushings helps band-aid the binding as they can 'squish' in a way that a flex joint can't, which is to effectively lengthen or shorten the link length to allow for the axle to rotate properly. Without that movement the axle is going to want to twist in the middle.

Your crossmember is stout enough to run a 3-link with a panhard; why not do that and have a setup with no binding at all?

Yup, got a 1.25" DOM track bar being built as well. The geometry is similar to the BDS setup, except the UCAs are longer. It's only lifted 3.5" so I'm not going for huge articulation here. The purpose of the 4 link setup for me is primarily on road comfort and stability with articulation being a close second. The heims are on just the crossmember side with WJ bushings on the axle side. I might very well do exactly what you said though. I could very easily remove one of the UCAs, but I'll wait until I can test it out to make that call.

By cutting that big box out totally destroys the stregth of the tubing.And I always want "zero" places for mud/moisture to gather(sealed crossmember).

Not true at all. Cutting out the radius' of a tube will destroy the strength. You can see that I didn't cut into the radius of the tube. Removing the flat surface in this case, does very little to reduce the strength of the tube. From my structural steel experience, this tube is still at least 90% as strong as an uncut tube of the same size. Combine the fact that the CA mounts are right next to the frame rail brackets, and that it's getting bolted to another 3/16" plate...it's more than strong enough.

He's probably took into account that the stock X member sits that low, and his new one sits highter, hence having to cut out the box tube so the TC/Trans/Engine sit horizontal in the vehicle like it would with the factory X member

Exactly. The TC mount sits inside the tube and is spaced about 1/2" off the bottom surface. Overall the TC sits in the stock location.

 

[RCP Phx]

Not true at all. Cutting out the radius' of a tube will destroy the strength. You can see that I didn't cut into the radius of the tube. Removing the flat surface in this case, does very little to reduce the strength of the tube. From my structural steel experience, this tube is still at least 90% as strong as an uncut tube of the same size. Combine the fact that the CA mounts are right next to the frame rail brackets, and that it's getting bolted to another 3/16" plate...it's more than strong enough.

Total BS! I could problably bend it just by jumping on it!

 

[whitneyj]

jenny criag. . .

 

[Boostwerks.com]

Total BS! I could problably bend it just by jumping on it!

I'd like to see you try. :moon:

If I manage 20-25 steel fabricators every day I must know something.

 

[squirrel80]

Here is the BDS crossmember I am running. It has worked great and the geometry works awsome. I have very good articulation and very little bind, but I do have a custom high steer and track bar location that puts the track bar at a very flat angle. I did recently have to gusset the upper control arm mount because it was starting to crack, but I have beaten this hard and it looks like it could have used it from the factory. Also BDS uses a side plate and crush sleeves for extra support, so they do not just rely on the bottom bolts.

 

[DrRandy]

I'd like to see you try. :moon:

If I manage 20-25 steel fabricators every day I must know something.

:clap::clap::clap::clap::clap::clap:
GREAT Work, and i'm sure it will function great as well!!

 

[vetteboy]

The heims are on just the crossmember side with WJ bushings on the axle side. I might very well do exactly what you said though. I could very easily remove one of the UCAs, but I'll wait until I can test it out to make that call.

As long as you keep the bushings in there it'll probably be OK, for the most part. But:

Here is the BDS crossmember I am running. It has worked great and the geometry works awsome. I have very good articulation and very little bind, but I do have a custom high steer and track bar location that puts the track bar at a very flat angle. I did recently have to gusset the upper control arm mount because it was starting to crack, but I have beaten this hard and it looks like it could have used it from the factory.

This is what you'll run into eventually if you keep the axle brackets stock. The binding I mentioned is inevitable and something gives. The bushing deforms but you've still got that stress on the axle mount, and given time will fatigue at the welds. Remember...just because it flexes well, doesn't mean it ain't binding.

Reinforce the stock axle UCA mount, and the weak link moves elsewhere. Find the threads in the first few pages here about guys with radius arms that are eating bushings...that's the next step. Put all flex joints in and something else is gonna give...

Not true at all. Cutting out the radius' of a tube will destroy the strength. You can see that I didn't cut into the radius of the tube. Removing the flat surface in this case, does very little to reduce the strength of the tube. From my structural steel experience, this tube is still at least 90% as strong as an uncut tube of the same size. Combine the fact that the CA mounts are right next to the frame rail brackets, and that it's getting bolted to another 3/16" plate...it's more than strong enough.

90% as strong? In what plane of bending?

In a situation where you land the rig on the crossmember, you are absolutely nowhere near 90% as strong. Now you've removed around 40% of the material cross-section at that point, and the majority of that is the section furthest from the neutral axis of the structural shape.

Keywords: area moment of inertia, and section modulus. Removing that part kills that section of tube as far as supporting bending stress in the middle. Being bolted on the ends will help though.

From the front, it's not nearly as big a deal. That's why so many truck frame weren't boxed from the factory. Given where you're applying the load I agree that the stress from the arms isn't going to be where your problem comes from.