SLON-WORKSHOP Torsional Rigidity Platform. E46 M3 new experience & tests. Tech info

[Slonik]

I asked the question here, or to somebody else, about getting the chassis seam welded at one point. Whoever I asked questioned if it was really that much of a benefit. Would this be evidence of spot welding loosening or giving up over time? Or what would this weakening be from?

hello!
i think you are on the right way . i'm almost sure that main of the looses lies in the spot welding weakening.
and i'm sure, that with the seam welding, you can not only restore your factory rigidity, but impove it a lot higher.
anyway, if we back to the begin - main idea, about such products like our wall, was to make some noticable improvements and combine them with some other advantages.
in "other advantages" i've put, not to make some typical "race car" style doings, like cutting chassis, a lot of welding etc during installation.
anyway, many of us face to the cracking floor issue, and it's a good reason to make some seam welding on the rear floor area - you need to prime and respray it anyway, so why not to put some additional benefit during this process?

same time, seam welding of the main floor, front end and other chassis on the road car - very dubious idea.
cause it's a HUGE work, and anyway, you have a LOT of chances to get some rust issues in the next years.

like i said earlier, we have another one e46 m3 with some deep works during this winter. and before our "special" upgrades, we will make some restoration on the chassis, which will includes rear floor changing.
and of course, we will make few tests to get the difference figures, before any works started (typical "used" condition figures), and right after rear floor changed (incl rear floor seam welding). i hope to get figures, a lot closer to the factory values.
lets wait and see

[Slonik]

Is it possible that something about the rig is producing a lower number than what BMW’s rig would show? Kind of like different dynos producing different numbers for the same engine?

very good question!
it was the first thoughts, when i've made first tests and saw figures .
but some of the factors, convince me of the correctness of our results.
i have two main arguments:
1. chassis as is - it's not new. but anyway, i think we will get two -three confirmations nearest months.
1.1 one of them - figures on the e46 chassis after some restorations. if we get some closer to the factory figures - it works correct.
otherwise, if we prefer to use some "correction coefficient" on today, and will get higher figures after restoration, would you believe that we get fugures higher than chassis had from factory? of course not)
1.2 another one - figures on another chassis, not so old as e46.
we have e92m3 in work also. of course, its not brand new, but my experience would say that it must have a lot less rigidity drop anyway, compared to e46, due to the very different, more rigidity chassis design.
we have few f82 m4 in our workshop also. but i don't think that we will put them on the platform in the nearest months.
to mount it, it needs some preparation works on the car first, and then some time for mounting it to the platform, so it's not so easy, like "lets try it".

and another argument way:
2. i've built our measurement system that way, to eliminate any possible losses. sensors located on the chassis, so we have angle figures as raw, about nothing to loose in that case.
applied force - we have made mounting of the chassis rigid, and same time without any unwanted influence - rigid shocks mounts on the ball bearings, even aluminum adapters to the transverse bars have no solid fixing in width.
but anyway, any of that things could make figures higher only, not lower. for example, if we would make solid shocks mounts, without spherical ball bearings, transverse bar rigidity could add its to the chassis rigidity, but no way to lower rigidity.
even front transverse bar center mounting point - if we have some losses on it, so: we are applying force, i see figures, and due to this losses, applicable force to the chassis will be less, so we will get less angle and that mean that i'll get at the end higher torsional rigidity figures (same force, less angle = higher rigidity figures).

so, why i prefer to believe in the figures.

i'll add some thoughts later on that topic, why we use one way, and not another also. it will be another one 2 cents.

[usdmej]

Depends on demand. till this moment, you are the first, who ask about this ski cut out

the center of the panel seems like where you would want the most material, would this very advanced engineering schematic showing the potential cutout in red minimize the loss in rigidity?
you wouldn't get ski pass functionality back but you could still fold own the seats to pass things through

[Slideways]

Do you have any pictures of the measurements you can post, or can you make a video showing/explaining the results of the test?

[nextelbuddy]

so im curious... i have a Sedan with NONFOLD rear and it shows out of all the NON Ms it is the most stiff.. then you have the M3 coupe is stiffer than the Sedan NON FOLD but the M3 accomplishes this with Folding rear seats.. are we saying that the M3 accomplishes this through all of the additional Stiffening plates on the bottom, the V brace from the Diff to the chassis and the factory mounted strut brace? Im asking because I dont think there is anything chassis wise that is actually structurally different between Sedan non M and M3 coupe chassis besides the stiffening plates, V brace and strut brace additions.


i'm asking all of this because it sounds like since i already have the non FOLD factory wall in place + all of the M3 stiffening plates, strut brace, Diff V brace with my conversion then im already at what the M3 is with the CF wall correct?

[Slonik]

Do you have any pictures of the measurements you can post, or can you make a video showing/explaining the results of the test?

i can make some pics next time

[heinzboehmer]

so im curious... i have a Sedan with NONFOLD rear and it shows out of all the NON Ms it is the most stiff.. then you have the M3 coupe is stiffer than the Sedan NON FOLD but the M3 accomplishes this with Folding rear seats.. are we saying that the M3 accomplishes this through all of the additional Stiffening plates on the bottom, the V brace from the Diff to the chassis and the factory mounted strut brace? Im asking because I dont think there is anything chassis wise that is actually structurally different between Sedan non M and M3 coupe chassis besides the stiffening plates, V brace and strut brace additions.


i'm asking all of this because it sounds like since i already have the non FOLD factory wall in place + all of the M3 stiffening plates, strut brace, Diff V brace with my conversion then im already at what the M3 is with the CF wall correct?

M3 has some extra seam welding (and more spot welds?). Can't pull up any literature on it right now, but the things you listed are not the only changes in rigidity between the non-Ms and M3.

[Slonik]

so im curious... i have a Sedan with NONFOLD rear and it shows out of all the NON Ms it is the most stiff.. then you have the M3 coupe is stiffer than the Sedan NON FOLD but the M3 accomplishes this with Folding rear seats.. are we saying that the M3 accomplishes this through all of the additional Stiffening plates on the bottom, the V brace from the Diff to the chassis and the factory mounted strut brace? Im asking because I dont think there is anything chassis wise that is actually structurally different between Sedan non M and M3 coupe chassis besides the stiffening plate.


i'm asking all of this because it sounds like since i already have the non FOLD factory wall in place + all of the M3 stiffening plates, strut brace, Diff V brace with my conversion then im already at what the M3 is with the CF wall correct?

yeah, you have torsional rigidity similar to m3 coupe with bonded wall i think.

[old///MFanatic]

i have a Sedan with Nonfold rear and it shows out of all the NON Ms it is the most stiff.. then you have the M3 coupe is stiffer than the Sedan NON FOLD but the M3 accomplishes this with Folding rear seats.. are we saying that the M3 accomplishes this through all of the additional Stiffening plates on the bottom, the V brace from the Diff to the chassis and the factory mounted strut brace? Im asking because I dont think there is anything chassis wise that is actually structurally different between Sedan non M and M3 coupe chassis besides the stiffening plates, V brace and strut brace additions.

“The increased body rigidity is achieved by the use of additional gusset plates and weld
points. Both functional and technical modifications have been made to the side frame
structures, front and rear wheel arches, reinforcement in the C-pillar area as well as the luggage compartment floor.“ ///M
There are 102/(120) additional welds in the M3 over non-M.

[old///MFanatic]

[S14]

Is it possible that something about the rig is producing a lower number than what BMW’s rig would show? Kind of like different dynos producing different numbers for the same engine?

easy test would be to verify rigidity of a current chassis without a ton of years/miles on it against BMW's data and see how close the two compare. You can then use this delta to help correct the differences between the test rigs.

[Casa de Mesa]

the center of the panel seems like where you would want the most material, would this very advanced engineering schematic showing the potential cutout in red minimize the loss in rigidity?
you wouldn't get ski pass functionality back but you could still fold own the seats to pass things through

Which version of AutoCAD did you use to generate that schematic?

[usdmej]

Which version of AutoCAD did you use to generate that schematic?

i could say but at that point i might as well be designing Slonik's products for him

(sarcasm btw)

[Maxhouse97]

Slon - can we still do business with you from the US?

[IamFODI]

Two posts deleted. No actions taken against users at this time. This was purely to nip a potentially problematic digression in the bud.

Please, let's not make this political. Yes, the horrors of Russia's invasion of Ukraine and its geopolitcal and domestic implications deserve to be discussed. Yes, the related sentiments deserve to be aired. But unless Slonik's business turns out to be directly supporting the invasion, this isn't the place for that.

Maxhouse97's question, as-written, was a practical one. Let's keep it at that.

EDIT: In case it wasn't clear, this goes for you, too, Slonik.