heinzboehmer's 2002 Topaz 6MT Coupe

[heinzboehmer]

I like your bracket idea, why not commission it to a machine shop and have a billet set that will last forever, unless you have to use their safety benefit (:

Mostly cost. Laser cut parts will be ~$50 after bending and powder coating. Billet part will be multiple orders of magnitude more.

I might do a billet version in the future, but I have a suspicion that I'll want to iterate on the design down the line (like always) and would rather not end up with multiple useless billet pieces.

[maupineda]

I like your bracket idea, why not commission it to a machine shop and have a billet set that will last forever, unless you have to use their safety benefit (:

[heinzboehmer]

Hell yeah, thanks. Have two sets of those, so should be easy. We'll find a time.

(Have two sets because the early mounts have press in studs vs screw in and figured the screw in ones would be easier to work with)

[Bry5on]

Easy enough. Get me a pair of strut mount castings in the next couple weeks and I’ll machine them down for you one evening.

[heinzboehmer]

I'd just be designing the sheet metal parts now if I were you

Thick flat sheet with a mild bend and some tab/slots for gussets, some quick welds and you'll be good to go.

I've been giving some thought to this and for some reason, I really want to try and keep the stock strut bar brackets. That voice in my brain that tells me to make everything look factory can be annoying sometimes...

Anyway, I think I might try going for an intermediate approach that lands somewhere in between of "small reinforcement bracket" and "full replacement". Basically do the thick flat sheet part you were talking about, but make it so that the stock piece bolts up to it and essentially acts as the gusset. Would just need to drill out the threads in the stock piece and add studs to the sheet metal so that it bolts through.

Would also likely need to machine down the "feet" on the stock parts so that the stock bar doesn't move up significantly:



Getting too far ahead of myself though, first need to finalize the design for the windshield bracket and see where the E86 braces land with those final dimensions. Then I can see move on to the (first) final design of the front brackets.

[Bry5on]

Yeeeaah

I guess it's more a matter of when than if. Fortunately they don't look too hard to remake out of sheet metal. And then I can put the mounting points for everything where I actually want them.

But at this point I kinda just want to see how long these will last

I'd just be designing the sheet metal parts now if I were you

Thick flat sheet with a mild bend and some tab/slots for gussets, some quick welds and you'll be good to go.

[heinzboehmer]

Will they crack? Absolutely yes.

Yeeeaah

I guess it's more a matter of when than if. Fortunately they don't look too hard to remake out of sheet metal. And then I can put the mounting points for everything where I actually want them.

But at this point I kinda just want to see how long these will last

[Bry5on]

Will they crack? Absolutely yes.

[heinzboehmer]

Progress!

First up, sliced test fit piece for verifying the contour of the bonding surface:






Looking good! It's hard to hold the piece and take pictures at the same time, so some of the surfaces (top, mostly) look like they're not sitting flush, but the fit is much better in real life.

Checking wiper linkage clearance:




No issues there.

I did, however, find that the passenger side of the mount extended too far and would interfere with the braces. Made a couple changes to the design and printed yet another prototype:



This time everything actually fit! Braces are still slightly too long, so they are interfering with themselves, but cutting them down will solve that:




Took some measurements and decided where I want the fasteners to live. Here's a visual reference of their locations in space:



Orange cylinders are where the braces will get fastened to the piece and green cylinder is the virtual point where the two braces would intersect. Looking pretty decent there as well.

I did, unfortunately, have to make the decision to move the fastener location on the strut bar piggyback clamps. Instead of having the braces attach behind the strut bar studs (as previously designed), they will attach to the innermost stud, underneath the stock bracket. Things are too tight in that area to have that attachment point where I wanted it previously, but this should still work well.

The change is a bit easier to explain with a picture:



The bar is attached where it will now go and the hole in the 3D printed bracket is where I originally wanted it to go. With this change, the brackets aren't strictly necessary, as all that's needed is a longer inner stud, but I'll be keeping it to reinforce the cast factory strut bar end piece. I'm still 50/50 on whether they will crack when I hit the first pot hole or not

Here's a dry fit of the entire thing:



Looking very promising!

Also, you can probably tell that the driver's side brace is very much in the way of my current dipstick location. Unfortunate, but not a big deal. I'll likely just swap over to the CSL dipstick.

[heinzboehmer]

Initial test fit went well:



Some tweaks needed to get it perfect, but one more iteration should do it.

[heinzboehmer]

Also, ran the numbers for the two piece approach (using the current draft design) and the weights are as follows:

• Front "tall" piece
  • ~0.9 kg (1.98 lbs) if made out of 6061 Al
  • ~2.6 kg (5.73 lbs) if made out of 304/316 SS
• Rear "sheet" piece
  • ~0.4 kg (0.88 lbs) if made out of 6061 Al
  • ~1.0 kg (2.20 lbs) if made out of 304/316 SS
  • ~0.2 kg (0.44 lbs) if made out of sendcutsend 3.99 mm thick CF

A lot of these are WAY more than I want, especially since this weight lives high up and in the front of the car.

Design is currently bigger than it will end up being (width wise mostly), so that will shave some weigh off, but the bulk of the weight comes from the front piece being completely solid. Once I figure out the precise angle that each brace will sit at, I can work on hollowing the piece out, while keeping enough material in the load path of the braces. It'll be a fun exercise to find a good tradeoff between weight, strength for the braces and appropriate surface area for bonding the sheet.

Of course, making the front piece out of carbon would dramatically decrease the weight, but I have zero carbon skills, and I absolutely do not trust myself with this as a first project. It would absolutely suck to be grinding the failed pieces out of there in a few months.

If I can make the entire thing weigh less than 1 lb, I'll be happy.

[heinzboehmer]

Fantastic!

What are your plans for the microfilter housing?

Ah great question! Forgot to talk about that. Since the attachment points of the E86 braces will be fully underneath the windshield, the firewall plug will need little modification. Basically just a clearance cut.

Filter housing can also keep its general shape, with some reliefs for the top of the braces. For the first prototype, I plan on cutting some clearances into a stock housing and printing some pieces that I can epoxy in to close up the holes. Trickiest bit will be making sure the gradients on all surfaces point towards one of the two drains, so that water doesn't pool up inside there.

Eventually, I'd like to print a mold for both pieces and remake them out of prepreg carbon using a method like this one:

https://youtu.be/6xj06Am94aQ

Need to get the geometry correct before going crazy with the carbon though

[George Hill]

Fantastic!

What are your plans for the microfilter housing?

[heinzboehmer]

Oh! I also designed these things:






They fit over the ends of the E86 braces and tell you exactly where to cut/drill them so that they fit on the E46 chassis. The cuts will shorten the total length of each brace by 53 mm, which is just enough to make them fit.

[heinzboehmer]

Loving the E86 brace - top "thinking outside the box" work as usual .

Thanks! Looking forward to finishing and installing on the car.

Also, quick update on the design of the windshield attachment point. First, a run down of the space constraints:

1. This feature exists for RHD windshield wiper linkage clearance. Don't need to worry about this for now and the piece can be designed to bond to this surface.
2. This is the same linkage clearance but for LHD cars. The entire marked section is off limits.
3. This part is flat and can be used for extra support (even directly behind the linkage). However, there's not a ton of room between it and the blower motor, so whatever goes in there has to be essentially a thin sheet. Note the (hard to see) grommet. Thin sheet will need to have clearance for this.
4. This white piece sticking down is a grommet that holds the plastic windshield cowl in place. The brace piece must have enough clearance to allow the grommet to work as designed.

While my design will only directly fit into LHD cars, the geometry under the windshield is symmetric side to side, so all that's needed to make a RHD piece is to mirror it.

With the constraints in mind, we come up with this. Note that this design is missing some curved edges that need to be part of the final design. Those will come later once the general fitment is validated:



I think it's pretty clear why the design looks like it does. There really isn't any other geometry that works under there! Space is very limited.

Next step is to print some slivers of the piece and test fit on the car, then move on to the final design.

Speaking of, I still don't have a plan for how to manufacture this, but these options are floating around in my head:

1. Print the thing in some kind of metal and hope it holds up
2. Mill/print the front part and bond a CF/metal plate to the bottom for the flat feature
3. Design it for laser cutting, bending and welding

I think I like (2) the most. Would make it pretty strong and relatively easy to manufacture. I would just need to add some threads to the bottom of the front piece and then bolt + bond the sheet to it. Also, sendcutsend cuts CF sheets, so no need to mess with cutting that stuff in the garage