E86 Front Triangulation Braces Retrofit

[heinzboehmer]

Added the weight of the stock cabin air filter housing to the documentation (thanks OldRanger for weighing yours!).

Here's a screenshot of the data:



Looks like with the 3D printed strut tower brackets, this mod results in a net 909g (2lbs) weight reduction over the stock parts.

I haven't done the math, but just by eyeballing, it looks like the car's center of gravity will drop by a little bit (most of the weight savings come from the replacement HVAC plastics) and likely not move very much front to back (E86 braces are out front and windshield mount is out back)

[karter16]

Are these the studs in question? M10x1.5x20 and M10x1.5x30 from MRO?

https://mrohardware.com/product/m10-x-1-50-high-torque-studs-sfhh00m1020d/

https://mrohardware.com/product/m10-...-sfhh00m1030d/

Yep those are the ones

[karter16]

Why not just insert the helicoil and cut a threaded rod. On my carbon part, I molded threaded inserts and then used an M8 class 8.8 threaded rod cut to length. Loctite on the end that goes into the bracket.

With the caveat that I'm not really the appropriate sort of engineer and didn't FEA it, this was my original plan, but I got a little sketched out about the thread depth available given the size of the part (bearing in mind in my case the part is aluminium) and thought that Heinz's approach of having an insert that couldn't pull through seemed better to me.

[George Hill]

Are these the studs in question? M10x1.5x20 and M10x1.5x30 from MRO?

https://mrohardware.com/product/m10-x-1-50-high-torque-studs-sfhh00m1020d/

https://mrohardware.com/product/m10-x-1-50-high-torque-studs-sfhh00m1030d/

[bigjae46]

I mean thread a bolt in in place of a stud, not a bolt to replace a nut. I think adding the flats is no better than adding a hex pattern personally. Either way it’s a printed part job. Seems easier to add threads there and eliminate all semblance of a press fit. Just bolt a bolt in instead of pressing a stud..

Why not just insert the helicoil and cut a threaded rod. On my carbon part, I molded threaded inserts and then used an M8 class 8.8 threaded rod cut to length. Loctite on the end that goes into the bracket.

[karter16]

Well just heard back and the fab house (ApexBatch) are happy with the design, and the quote seems reasonable to me so think I'll probably give this approach a go, if for nothing else but to prove it out as an option for those who find it harder to source the specialist hardware.

[heinzboehmer]

A little 3D printed retainer would help with keeping the fastener from moving too much when you start the nuts, but yes still floating.

[karter16]

Awesome thanks! Yep I made sure the wall thicknesses were going to be okay. Thanks for that tip, I probably knew that once upon a time but had completely forgotten and hadn't considered it at all!

Haha I do appreciate that the thread approach is better, my thinking with this approach is part me being stubborn but also part it saves me needing any M10 helicoil hardware.

[Bry5on]

Just check your wall thicknesses to make sure there’s nothing too thin and you’re good. That should work.

Pro tip: Note that you should always pick a corner radius slightly larger than the diameter of the tool you’ll be using so the end mill can make the corner without chattering.

edit: just remember that with a design like that, the fastener is still technically floating and won’t be rigid when you start running the nuts down and/or it can fall out when this part is removed. Last attempt to get you to switch to threads

[karter16]

Of course, thanks both, I'm a bit dumb.

I envisaged one thing - a slot cut with a (virtual) 17mm end mill, and then designed something completely different.

This version takes my actual original plan and improves on it by reducing the amount of extra material removed. a 17.2mm x 20mm pocket, with 10mm sides that hold the bolt head, suitable for a 6mm end mill. Note that the shape is intentionally not a regular hexagon as this design only intends to hold the bolt head on two sides.

[heinzboehmer]

Something like this should be fine right? Obviously I haven't done FEA on it, but I did go through all your screenshots and don't believe this design impacts the areas of highest stress. I'm also not particularly stressed if it does prove to be a problem as easily swapped out if there are any issues.

Bryson spoke to this already, but the problem lies with the sharp corners. Elongating the bore and adding transition fillets would help.

The issue I see with printing this is that the machined mating surface on the windshield mount is super smooth and flat. If printing, I would add material to the E86 attachment point and mill it down so it's also flat.

[Bry5on]

What is it about the flats that makes it a printed part job? I don't see how it's different from a manufacturing perspective to the circular pocket Heinz has in the current design?


Sent from my iPhone using Tapatalk

Very easy to machine/drill a circle/cylinder, not so easy to machine an arc to flat transition, especially if you are short on packaging space and need a tight radius on the transition from arc to flat. You’ve gotta think about what tool(s) you’d use to make that part. A tap and hole is about as simple as it gets

[karter16]

I mean thread a bolt in in place of a stud, not a bolt to replace a nut. I think adding the flats is no better than adding a hex pattern personally. Either way it's a printed part job. Seems easier to add threads there and eliminate all semblance of a press fit. Just bolt a bolt in instead of pressing a stud..

What is it about the flats that makes it a printed part job? I don't see how it's different from a manufacturing perspective to the circular pocket Heinz has in the current design?


Sent from my iPhone using Tapatalk

[Bry5on]

I mean thread a bolt in in place of a stud, not a bolt to replace a nut. I think adding the flats is no better than adding a hex pattern personally. Either way it’s a printed part job. Seems easier to add threads there and eliminate all semblance of a press fit. Just bolt a bolt in instead of pressing a stud..

[karter16]

Oh yeah, duh. That would totally work and is way simpler

Something like this should be fine right? Obviously I haven't done FEA on it, but I did go through all your screenshots and don't believe this design impacts the areas of highest stress. I'm also not particularly stressed if it does prove to be a problem as easily swapped out if there are any issues.