XV Level II Front - Steel or Aluminum?

Hey all,

I'm considering buying the XV Level II suspension for my Satellite. Turns out they now offer the front K member replacement frame in aluminum or steel. I was wondering if anyone had any insight into the pros/cons of each, and the strength of aluminum in such an application. Given the cost and (current) rarity of this part, I want to get whatever will last the longest.

Thanks.

What is the grade of aluminum and steel in question? Also the thickness and cross section..

“Aluminum” isn’t inherently better. Typically the grade of the material should be known and it’s also likely not a 1:1 exchange in design or raw material dimensions.

Personally, I’d want high carbon steel, ~4130 for something like that and it would still maintain a healthy weight.

Your choice IMO is not really about "strength", when choosing between steel/alum in this application. First question, is it welded? I believe it is. Welding alum in high stress applications should done gingerly. Ever seen a welded alum con rod? You won't. Alum when loaded begins its fatigue process at its first loading, The higher the load, the sooner it fails. If the load is reversed cyclically, the faster the fatigue occurs. If corrosion elements exist, it only gets worse. Failure is usually catastrophic.
In race extreme weight conscious applications that have a limited intended lifespan and regular inspections, Alum is useful. CM is nice, but would at least require a Pro (not a torch warmed to dull red, etc) HT, post weld/fabrication, to avoid similar Alum failure results. SS work hardens, and cracks, but looks pretty. The heavier/thicker you make any of the above, the slower the negative results appear, but then what is the point?

Now if its trailer queen. have at it.


I confess, in light of all the above, I toyed with over the years with the idea of doing one out of CF, its doable, it would totally trick, and somebody eventually will build one, it will be strong, light, and fairly costly, just can't zero in on its useful lifespan, without testing.

Since this car is one that is driven a lot, and until 3 years ago was my daily driver for 30 years, it sounds like steel is the way to go. The last thing I would want is for the frame to crack from repeated use.

One thing that a simple thinking guy like me knows is that steel can deform a bit and return to shape without cracking. Not always the case with aluminum.

Well they originally came in aluminum 15 years ago, have not heard of the Kmember failing yet.

For arguments sake, might be hard to argue your observation, but your conclusion IMO is likely unsupportable for a number of reasons, two main ones, small sample to begin with, and reticence of owner to declare they spent a lot of money on a warned about known risky solution, that failed(?) and is effectively unimproveable as is, and that it was more for bragging rights anyway, then for best proven design practices.

Well JCC, I guess you will never fly because just about every airliner has welded aluminum primary structures in them along with carbon fiber reinforced plastic...I figured that if one failed like those control arms did a few years ago from another manufacturer, there would be pics all over the net. At the prices XV was charging, they could afford to get a proper heat treat. Just an observation. Tim

No they don't have primary "welded" alum structures, and alum is used because reduced weight is crucial to the task, and they have a track record of more then say 15? planes flying, they have extensive fatigue testing before manufacturing, they now have regular pre determined useful lifespan replacement procedures, and regular inspections beyond just visible. Its not an accurate comparison or observation.

Post weld heat treat of alum is problematic.

https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

When Magnumforce front ends were failing, the whole internet knew about it.

I'm sure we'd know by now if the XV aluminum K-frame failed.

BTW, their website still shows only aluminum.

Where'd you hear about them offeringi t in steel?

website

I did some searching last night, I found two old threads about XV products behaving badly, in one there was well documented shoddy build quality, and there was one UCA that failed in use, and was replaced with an upgraded part. This was years ago, pre XV Engineering. No sign of "k" member failures- they aren't K shaped so it's really a subframe. I like the A-body option they are showing as in development. It's been a year and a half, but still there isn't anything like it for old A-body Mopars.

I don't think the shape is real pertinent here in this discussion.Beyond what has been already mentioned regarding material/fabrication, its about the loading involved, the critically of the part, and the total design as whether the item is subject to loads an OEM K member sees.Since track record is such a focal point here in many comments, is there any best guesstimate on how many actual XV alum members were delivered and installed, and then how many of those see any regular usage?. That number would be useful IMO.

I spoke on the phone to Chris who is heading it now. He said they are able to manufacture it in steel upon request.

Unless you are an engineer working at a manufacturer or an IA, you are full of $hit...Yes they do have welded aluminum primary structures, I have worked on a lot of aircraft that do. Now machining has become cheaper and replaced it but it is still out there. Hell Boeing is using CF reinforced plastic now for spars...its not even epoxy based

What difference does it make where I work? Airliners either have or do not not have primary welded alum structures, and I or you are full of $hit.

Since i cannot prove this by showing a majority of the airliners without primary weld alum structures, maybe you can prove your point by showing examples of one's that do, and we can put this to rest, and move on.

I should probably mention this, as someone paying attention likely will, it is possible to incorporate welds in primary welded structures of critical importance, but it is not an easy task. the below link lists a high end semi trailer that has a primary welded pair of main I beam's. Its use does not require the reliably I suspect as an airliner, but it is far beyond what we require for our hot rods. The design trick this trailer incorporates is the welding is located on the beams neutral axis, is the lowest stressed area of the beam. This option is not always available.

https://www.wabashnational.com/brands/benson/product-portfolio/aluminum-flatbeds

www.faa.gov/documentLibrary/media/Advisory_Circular/AC_33-6.pdf

Engine cases are primary structures as one example

Well that is 12 pages of detailed requirements to repair piston powered crankcases.

Chapter #6 discusses criteria to allow welding repairs, in part:

"Weld repairs in the following
areas, unless approved by the engine manufacturer, must be
substantiated by a detailed analysis of the repair that ensures
the airworthiness of the part. Substantiation may include
dimensions (locations and alignments of critical areas), hardness
tests (before and after welding), full scale engine block test,
in-service tests which include periodic inspections (on similarly
repaired cylinders or crankcase), military specifications,
industry standards, fatigue testing, and engineering analyses"

I am not convinced in every case the "crankcase" is considered a "structure": .in the context of our discussion..

I early on mentioned an Alum Con rod is not repair welded, which I still stand behind.
Everybody knows ALUM race Hemi's are repaired by welding.
Everybody also knows the welded alum Hemi's have less value and often less perceived reliability, depending on where the repair is located, and a seller usually is expected to disclose any repairs prior to sale.
A weld is a repair in an attempt to extend the useful life of a component, subject to the 12 pages, Choosing an alum welded primary structural solution in an airliner initially, is still not proven IMO

FWIW, I cannot currently prove, but seriously doubt, XV ever had more then, if any, a half{?} of page of alum welding procedures, nor any of the welding criteria listed in your Aircraft crankcase weld repair advisory in their procedures..

Didn't see HAZ issues mentioned once in your attached advisory., nor analysis/determination of alum alloys addressed for welding

Those items are in the MMPDS 12 or 13, I dont currently have access to be able to upload those...but an engine case is structural, so are engine mounts, which can be welded in some instances. Hell the grumman Cheetah is glued together, the skins are glued on the structural members...didn't last long but the OEM did it.

I suspect the welded crankcases you mention have similar structural importance as a welded Hemi block does relatively in a TF car? You can do it, but nobody likes it?

I also suspect we are now no longer talking airliners?

I still doubt XV has 12 pages of detailed requirements for welding, which I listed, and those often require an in depth engineering sign offs to permit a welding repair of an alum crankcase.

I don't see how gluing anything here relates to the original topic of downsides of welding primary structural alum on an airliner as an intended design solution. You seem to be completely overlooking the long commonly understood downsides to welding alum in this specified application.

We are now going in circles.

Others have, I believe, an informed multi sided discussion here to decide for themselves, what they are comfortable with that is welded, alum, and is structurally loaded, in their cars.