E86 Front Triangulation Braces Retrofit

[heinzboehmer]

Some updates on the remaining bits of this project in my journal, in case anyone wants to follow along with the development: https://nam3forum.com/forums/forum/m...477#post324477

Track day coming up, so should have some solid temp data next week for you guys. Preliminary data is promising.

Also, printing up the first full scale prototype of the modified cabin air filter housing as we speak. Hoping that the design for that doesn't need too many iterations.

[heinzboehmer]

Still have some finishing work to do. Now on to figuring out the strut mounts and mounting the bars. The challenge here is serviceability. I would like the two new braces to mount under the OEM bar so it is less to remove if I need to remove the intake manifold.

I am also going to do the strut tower mounts in long strand forged carbon. I am leaning towards making them thinner like Heinz’s process to fit the 3rd lug so I can make a plate which goes between the cross bar and the strut plates. Then bolt the triangle braces to the plate…like Heinz’s design.

Or maybe I mount the two braces under the strut tower plate and run a bolt through…

Hell yeah! I'm excited to see the design you come up with.

Amazing project and effort! Can’t fully say how much I appreciate this. Hopefully more people will get to use this diy for their cars and change the car for better.

I have a question. What is the reason to use or start with OEM aluminum strut brace? Are not there better and way stiffer 3piece alternatives like DMG or so? Since you can also remove the middle section of the brace for easier serviceability.
I understand that in an event of crash stiffer braces may damage the car more. But was it so big priority or you think there is not much of a stiffness available to be gained?

Yeah, like you said, I went this route mostly for crash safety.

Designs like the DMG bar are useful because they help reduce strut tower fore/aft deflection (relative to the other strut tower) with the torsionally stiffer bar. However, tying the strut towers directly into the firewall (which is essentially immovable in comparison) constrains the fore/aft deflection, so I don't think there's much to be gained from a stiffer middle bar.

Also, both the E46 and E86 braces are notched and designed to fail before anything else in a crash. Since they don't fail during normal use, there is likely little to be gained by upping the stiffness of each individual part.

I actually asked my coworkers boyfriend about this, who's a lead chassis designer at a world-renown automotive manufacturer. Wish I still had his big blurb, but basically, the gain by merely tying it in is so substantial, that as long as your tube stiffness is reasonable, the gains switching materials is so marginal it wouldn't be recognizable. He then said I could do it in chromium, but we didn't talk about temperature. There is tension fatigue, but the bar itself is so cheap it hardly comes into consideration.

Glad to hear that coming from someone with the appropriate credentials!

Also, temp data coming soon:

[YoitsTmac]

Amazing project and effort! Can't fully say how much I appreciate this. Hopefully more people will get to use this diy for their cars and change the car for better.

I have a question. What is the reason to use or start with OEM aluminum strut brace? Are not there better and way stiffer 3piece alternatives like DMG or so? Since you can also remove the middle section of the brace for easier serviceability.
I understand that in an event of crash stiffer braces may damage the car more. But was it so big priority or you think there is not much of a stiffness available to be gained?

I actually asked my coworkers boyfriend about this, who's a lead chassis designer at a world-renown automotive manufacturer. Wish I still had his big blurb, but basically, the gain by merely tying it in is so substantial, that as long as your tube stiffness is reasonable, the gains switching materials is so marginal it wouldn't be recognizable. He then said I could do it in chromium, but we didn't talk about temperature. There is tension fatigue, but the bar itself is so cheap it hardly comes into consideration.

[RazorM]

Amazing project and effort! Can’t fully say how much I appreciate this. Hopefully more people will get to use this diy for their cars and change the car for better.

I have a question. What is the reason to use or start with OEM aluminum strut brace? Are not there better and way stiffer 3piece alternatives like DMG or so? Since you can also remove the middle section of the brace for easier serviceability.
I understand that in an event of crash stiffer braces may damage the car more. But was it so big priority or you think there is not much of a stiffness available to be gained?

[bigjae46]

My forged carbon part came out to 415 grams - not much lighter than the aluminum part. Guessing it probably could optimize it to shave off 50 grams or so. I think the advantage here is it might be cheaper to produce.

I don’t have. blower motor or wipers so this should be much simpler for me. I bonded the parts using panel bond.







Still have some finishing work to do. Now on to figuring out the strut mounts and mounting the bars. The challenge here is serviceability. I would like the two new braces to mount under the OEM bar so it is less to remove if I need to remove the intake manifold.

I am also going to do the strut tower mounts in long strand forged carbon. I am leaning towards making them thinner like Heinz’s process to fit the 3rd lug so I can make a plate which goes between the cross bar and the strut plates. Then bolt the triangle braces to the plate…like Heinz’s design.

Or maybe I mount the two braces under the strut tower plate and run a bolt through…

[heinzboehmer]

Thanks so much guys. heinzboehmer thank you very much for your replies - I know you're busy at the moment, and my apologies - I did not mean to cause concern! Will be super-interesting to see what the temp data looks like. I'm playing around with the step file orientation and will report back when I'm done!

Nah, you gave me a fun side project to distract me of the stress that comes with building a new garage. Already designed a nice case for the thermocouple amps and everything. Am excited to grab some data.

Plus, now I'll have a setup to record temps anywhere on the car. Detailed brake telemetry sounds pretty awesome.

I am going to try panel bond since that is what I have on hand. Looks like the main difference is the 07333 has more give to absorb energy in an impacts. In the video neither part failed and I don't think I care about how the energy is absorbed...just don't want it to fall off. Only one way to find out.

And this also saves me money and room in my toolbox storing yet another damned cartridge gun and more bespoke adhesive! I have a 20ml, 50ml, and a 400ml gun and 11 different adhesive cartridges!

https://youtu.be/JEtHFNfx_rU?si=XqTfMX6XzRzYHUTx

The only concern I have is that any bump in the road will transmit an impact to the mount. Do that over and over and you might start to see failure.

But, again, I have no clue what kind of loads this part sees during regular use, so it might be completely fine.

[bigjae46]

I am going to try panel bond since that is what I have on hand. Looks like the main difference is the 07333 has more give to absorb energy in an impacts. In the video neither part failed and I don't think I care about how the energy is absorbed...just don't want it to fall off. Only one way to find out.

And this also saves me money and room in my toolbox storing yet another damned cartridge gun and more bespoke adhesive! I have a 20ml, 50ml, and a 400ml gun and 11 different adhesive cartridges!

https://youtu.be/JEtHFNfx_rU?si=XqTfMX6XzRzYHUTx

[karter16]

Thanks so much guys. heinzboehmer thank you very much for your replies - I know you're busy at the moment, and my apologies - I did not mean to cause concern! Will be super-interesting to see what the temp data looks like. I'm playing around with the step file orientation and will report back when I'm done!

[Bry5on]

I wouldn’t worry about the time-temp derating for 7075 in this location personally, but I won’t say no to more data either

[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!