E86 Front Triangulation Braces Retrofit

[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?


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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?


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[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.

[heinzboehmer]

Or a hex head bolt with a pill shape for it? No need to mill a hex shape right? Just two flat sides to stop the bolt head rotating?


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

[heinzboehmer]

Why not just tap and put a helicoil in then thread a cap head bolt into the hole with some loctite. Seems easy enough if there’s enough depth in the counterbore.

Mostly for serviceability. Getting a bolt threaded in back there is harder than a nut.

I guess you could tap and thread in a stud, but at that point, the captive bolt approach is not that much more work.

Edit: Oh wait, I think I misunderstood this. Thought you were talking about threading a bolt in from below. Either this or karter16's flats suggestion would work, you barely need any force to hold the fastener in place before friction takes over.

[karter16]

Or a hex head bolt with a pill shape for it? No need to mill a hex shape right? Just two flat sides to stop the bolt head rotating?


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[Bry5on]

Why not just tap and put a helicoil in then thread a cap head bolt into the hole with some loctite. Seems easy enough if there’s enough depth in the counterbore.

[heinzboehmer]

Just a note for anyone else international doing this project. I'm having significant trouble finding a source for the press in studs. The best option I've got so far is to purchase from the same place Heinz did and pay a $250USD minimum + ~$400USD international shipping. Which obviously I'm not going to do.

I'm wondering if my best option is to modify the firewall bracket components to take captive bolts, and use bolts instead of press in studs for the E86 brace attachment points on the strut brackets.

Woah, that's not great. Hit me up and I'll ship some to you. I have extras since they're only sold in packs of many.

Otherwise, yes, captive bolts are the solution. Could argue that that's how I should have designed the E86 attachment point from the start. There's more than enough room in there, but machining a hexagonal bore is not an easy task. I think a round bore with a key + a 3D printed/laser cut insert is a probably the best way to go about it. The bores are at an angle, so you might even be able to get away without the key and just have the geometry of the insert keep it from spinning when it's bolted up to the windshield mount.

As designed, a super low profile socket head bolt (e.g. McMaster 91223A462) with a 3D printed insert would fit, but it's not ideal:






Seems like a bit of a hack vs just modifying the design to fit a hex bolt with a retainer prior to getting it machined.

Unfortunately, there is simply no room under the modified strut tower brackets for anything except the press in studs.

[Bry5on]

Maybe try forward2me.com - that’s what I use for euro shipments when I can’t find another option.

[karter16]

Just a note for anyone else international doing this project. I'm having significant trouble finding a source for the press in studs. The best option I've got so far is to purchase from the same place Heinz did and pay a $250USD minimum + ~$400USD international shipping. Which obviously I'm not going to do.

I'm wondering if my best option is to modify the firewall bracket components to take captive bolts, and use bolts instead of press in studs for the E86 brace attachment points on the strut brackets.

[karter16]

Thank you!!!

[heinzboehmer]

Question - what is it about these nuts that make them not work with the press-in studs until you've run the tap through them?

The thread profile geometry is slightly different between the stock and replacement studs.

Stock nuts are designed for rolled thread studs and the threads on the press in studs are cut.

Some discussion on that topic here: https://nam3forum.com/forums/forum/m...288#post312288