E86 Front Triangulation Braces Retrofit

[heinzboehmer]

karter16, you really got this in my head, so did a little bit of analysis with the help of MIL-HDBK-5.

Let's use the 10,000 hr line as the worst cast scenario, even though most of our cars will never see that much extra runtime at temp. Am assuming 503 MPa for tensile yield strength at room temp of 7075-T6.

If the part sees 300 F (149 C) for 10,000 hrs, then yield strength drops to 171 MPa or 34% of its original strength.



If the part sees 250 F (121 C) for 10,000 hrs, then yield strength drops to 297 MPa or 59% of its original strength.



If the part sees 200 F (93 C) for 10,000 hrs, then yield strength drops to 433 MPa or 86% of its original strength.



So, at 120 C for 10,000 hours, we're still above the tensile yield strength of 6061-T6 (276 MPa). I really doubt the part will see more than 120 C, but we'll see what the thermocouples say.

Even if it does, that's what safety factors are for!

According to the analysis, the windshield mount should never see more than 109 MPa (source), which means that even in the worst case scenario of 150 C for 10,000 hrs, that part should still be strong enough. The brace attachment point could fail after extensive high temp exposure, but not too concerned about that one, as it's easily replaceable.

But no sense in jumping to conclusions without data. Will keep you all in the loop with the results of my little experiment.

[heinzboehmer]

Ordered some thermocouples and amps with analog outputs to wire into my Gauge.S. Finding chunks of time to dedicate to cars has not been easy lately, but I'll get some temp data for you guys soon.

[0-60motorsports]

In for 7075-T6 version Group buy if we have enough people and price comes down LOL

[heinzboehmer]

1: I presume that the orientation of the step files is just as you designed in CAD rather than oriented for optimal machining? The only reason I ask is that reorienting them has a non-zero impact on cost on several of the online quoting tools I've tried out (Would have thought it would be smart enough to find optimal orientation but I guess not). Just wanted to check if there is some specific reason you have them oriented the way that you do?

I do remember messing with the orientation of the parts, now that you mention it. Whatever I uploaded is just straight from the CAD. Let me know if you find an optimal orientation! Can update the files in the drive.

2: When choosing between 7075-T6 and 6061-T6 I'm wondering whether you considered the operating temperature ranges of the two? From what I'm reading 7075-T6 shouldn't be significantly exposed to temperatures above much more than 100C. Whereas it seems 6061-T6 can run up to about 180C or so. To be honest I don't know how hot things actually get back there, but it seems to me that it could be getting close to 100C right? Would be keen on thoughts from anyone who knows this stuff better than me.

I haven't seen the engine side of the firewall get past 80 C, even after a 30 min session on track with ambient temps at ~30 C. Temps inside the blower motor cavity should be lower, especially if recirc is off and you're pulling outside air into the cavity.

However, I do have to admit that this is a detail I overlooked. I went with 7075-T6 because of strength and did not think about how it would fare with temp.

Data says it shouldn't see any temps that would cause degradation and I haven't seen any signs of failure, so I think it's fine? This is definitely a question for someone like Bry5on.

I should probably stick a thermocouple in there, then go for a rip and see how hot the aluminum gets. Doing a Buttonwillow track day in a month or so, would be an excellent time to gather data.

[karter16]

Couple of questions from me (please bear in mind I'm really the wrong sort of engineer for this - I'm currently relying on my remembered knowledge of 2nd-year materials and DFM papers from 20 years ago.)

1: I presume that the orientation of the step files is just as you designed in CAD rather than oriented for optimal machining? The only reason I ask is that reorienting them has a non-zero impact on cost on several of the online quoting tools I've tried out (Would have thought it would be smart enough to find optimal orientation but I guess not). Just wanted to check if there is some specific reason you have them oriented the way that you do?

2: When choosing between 7075-T6 and 6061-T6 I'm wondering whether you considered the operating temperature ranges of the two? From what I'm reading 7075-T6 shouldn't be significantly exposed to temperatures above much more than 100C. Whereas it seems 6061-T6 can run up to about 180C or so. To be honest I don't know how hot things actually get back there, but it seems to me that it could be getting close to 100C right? Would be keen on thoughts from anyone who knows this stuff better than me.

[Nate047]

Do it.

Completely agree. Would be awesome if someone takes that on.

Trust me guys, I’m not the one you want doing this 😂 if you need photography of the kit, I’m your man!

[EthanolTurbo]

I can't comment on the e46, but on another car I own front triangulation is available as an add-on, big difference upon install. I don't see why the e46 would be any different.

I added the M2C/M3/M4 aluminum brace + carbon fiber U brace on my OG M2 and it made a noticeable difference in the front end responsiveness and rigidity, and that's on a chassis that's over 2x the torsional rigidity of the E46 M3. Furthermore, I don't think that's as drastic as these triangulation braces so yeah I'm all-in on the front end bracing being a mod that makes a big difference in feeling, responsiveness, handling, turning etc.

Edit: I also drove Bry5on 's E46 M3 wagon with all the bracing done on the front and rear end and it was phenomenal. Made it feel stiffer than an E90 M3, closer to a Z4 M Coupe honestly which is a massive improvement. And to top it off, his wagon has about the same miles as my coupe (250k+) so it's not like we are driving cherry shells, these are worn and for sure have lost rigidity with usage.

[oceansize]

I can't comment on the e46, but on another car I own front triangulation is available as an add-on, big difference upon install. I don't see why the e46 would be any different.

[heinzboehmer]

Front end triangulation is one of the most noticeable mods I’ve done to the car.

+1. It's right up there with tires, seats, general weight reduction and, of course, airbox.

[Obioban]

To Heinzboehmr - how much of a difference did you notice in structural integrity after you implemented this? Was it noticeable?

Front end triangulation is one of the most noticeable mods I’ve done to the car.

[karter16]

Edit: Actually, karter16, slotting the holes in the brackets is 100% the way to go if you are planning on designing an entire new piece. Make them match the slotted holes in the strut towers and done.

Kinda hoping you go this route now. Would be a much more elegant solution than what I have on my car now.

Ah I HAD misunderstood! for some reason I was envisaging needing forward/backwards movement. Excellent - I'll continue thinking this through then!

[Bry5on]

Precisely. Slot the holes! 3D print, powder coat, you’d never know it wasn’t factory.

[heinzboehmer]

Why would you need adjustable camber plates? The custom strut tower brackets would go on top of the strut tower, not below it like a camber plate. Factory top mounts should work.

You do need them with the current design.

You specifically need the style where the studs can move independently from the top hat (e.g. the Turner ones). This is needed to account for the fact that the braces will always stay in the same spot, but the top hats will move around depending on camber settings.

I guess another option is to slot the holes in the strut tower brackets. I think that's how Slon solved this same thing.

Edit: Actually, karter16, slotting the holes in the brackets is 100% the way to go if you are planning on designing an entire new piece. Make them match the slotted holes in the strut towers and done.

Kinda hoping you go this route now. Would be a much more elegant solution than what I have on my car now.

[heinzboehmer]

This is the route I was planning to go until I realized that you need adjustable camber plates to be able to install the brace - unfortunately makes it a no-go for me in NZ without going down the low volume vehicle certification path.

You could slot the strut tower side holes in the braces and that might give you enough wiggle room to line everything up without camber plates. I haven't tried this though.

I can tell you that I just barely managed to squeeze these things in there with camber plates. Install makes it abundantly clear that the chassis was not designed with this type of bracing in mind

Also, the left side brace gets stupid close to the DME cubby, so you'll likely end up limited on the camber adjustment with the stock top hats.

[Slideways]

This is the route I was planning to go until I realized that you need adjustable camber plates to be able to install the brace - unfortunately makes it a no-go for me in NZ without going down the low volume vehicle certification path.

Why would you need adjustable camber plates? The custom strut tower brackets would go on top of the strut tower, not below it like a camber plate. Factory top mounts should work.

Edit: Elongated holes required to work with stock camber plates.