nobggrnchvy Goatbuilt Ibex

[pardyam]

are you running an atlas support ring as well?

Yes, but you already knew that from reading the last sentence of my reply

 

[mobil1syn]

Yes, but you already knew that from reading the last sentence of my reply

too many constraints with the atlas ring, thats why your trans broke.

 

[pardyam]

too many constraints with the atlas ring, thats why your trans broke.

so by that logic, wisconsinites, hydrodynamics, and the OPs are all going to break as well?

 

[mobil1syn]

so by that logic, wisconsinites, hydrodynamics, and the OPs are all going to break as well?

increased likelihood if they have a large impact.

 

[pardyam]

increased likelihood if they have a large impact.

I didn't come in here to argue the merits of running an atlas supported vs unsupported, that's been hashed out plenty. My point was that a single 1x2x120 rectangular tube with an 1/8" skidplate will not support a 5,000 lb rig with a pallet sized belly opening, without deflecting enough to damage the trans housing. There are any number of ways of remedying this, all of which have been pointed out in the thread already. I agree that the trans may not have broken if it were not constrained, but the root cause was deflection in the trans mount x-member. I think a better solution than mounting the drivetrain with a ratchet strap so its free to move out of the way of flexy flyer skid, would be to prevent the skid from caving in in the first place. I doubt the OP would have ever had a problem, but I did with the same setup, so just trying to save the guy $1500 and weekend worth of work.

 

[Bggrnchvy]

Just playing devils advocate here.....how many of these chassis are out there and how many have had this issue? It appears that the crossmember is 1/4-1/2 higher than the outer parts of the belly. What about running an AR skid with some bracing welded to the back side of it so it doesn't defect and rest on that cross member?

I've been staring at it and putting some ribs on the back of the skid that clear everything else nested in there might the simplest answer to adding stiffness.

increased likelihood if they have a large impact.

I don't have much confidence the extra weight of the 205 and moment from the crawl box in front will keep the back of the 4l80e in one piece with a single mount either. I also didn't have enough room to raft the rear support and under t-case adapter support to one point of contact with the chassis to keep the perfect 3 point drivetrain plan.

As long as the mounting points don't move appreciably in the chassis (aka fail), I think that statement is incorrect though. The length of the drivetrain is better supported and can endure hard G hit than if the tail end was unsupported. It's also mounted down it's axis, so it still resists torque very similarly to the OEM designs.

It's kind of like a roll cage: the occupants, well secured, can withstand 50 G's for a few milliseconds and not be likely to die from the simple deceleration. When the roll cage tubes stop staying outside and come in looking for squishy people parts, the G's required to be lethal decrease pretty exponentially as human meat bag mashes against round tube.

 

[arse_sidewards]

Why not add some cheap bump stops as snubbers if you're worried about it?

This is assuming you have poly/rubber mounts that'll compress a bit when you take a hit.

 

[Wisconsinite]

1x2x120 rectangular tube

It is 1.50X2.5X.188. There are hundreds of subframes and skid plates out there, and I hear of very few failures.