Designing a New Strut Tower Brace..Opinions Please...

[Yahnozha]

Hey, Im working on a new strut tower brace for my ride (99 G20) Basically ripping off a japanese version but adding some other aspects to it. Material is yet to be determined, but an aluminum alloy of sorts (T5 6063? is what im looking at).

I got some questions and could use some help and opinions...

1) Does anyone know the distance from the top of the sheet metal (where the bracket mounts) to the underside of the actual bar at the higest point of a typical STB?
2) Notice any problems with this design?

Other notes: Im going to redesign the light green plate to have some swiveling capacity to align to the cross bar, by elongating the mounting holes to the base plate (dark green piece) and use a solid aluminium cross bar, uless I can get a carbon fiber one produced reasonably.

Just curious as to what you guys think? Please let me know. Sorry for the crappy rendering of this, and right now it sits 2" high

Pat
www.customsteel.com

Red 99 G20 (soon to be G20t..haha)
Unorthodox Underdrive 2 piece set
JWT POP
Hot Shot CAI (currently being modded)
Clear Lenses
PIAA H3 & H4 (on order)

[AznVirus]

looks like its going to be too large and bulky. could be sturdy, but might not be affective since the bar isnt actually connected to the car, thus the roll of the car has to go to the "bar holder", which is attached to the car, then transfer the stress onto the bar. dont know, just guessing

[b-b00gie]

Two ideas:

On the "light green" piece... on the tabs where the bar would attach, you should concider making it a 2 bolt design for strength and rigidity. (eliminate flex)

like so....
______
|
| O
|
| O
|_____


Also... if you plan on selling these I would HIGHLY suggest prototyping on a 2000+ G20. The 2000+ requires a little more height clearance so if you make the brace fit a 99 it may not work on the 00, 01 and 02 models. Where as if you designed it to fit a 00 thru 02 it would also work on the 99

BTW, please feel free to email me if you would like me to work with you in obtaining measurements to fit the 00+ models.

[T4 Primera]

Rather than slotting the light green peice - perhaps a swivel eye bearing (don't know if that's the correct name for them) could be threaded into one or both ends of the bar. Then the alignment would not be a problem and the length of the bar could be adjusted and even pre-loaded.

Your mounts are very aesthetically pleasing but i'm just wondering if they are overly complicated and hence expensive to produce. For example, while adding the six bolts to the top looks good, they will not add any strength and you are still limited to the maximum shear resistance of the three bolts on the tower. Are you incorporating the intermediate (dark green) piece to raise the bar for engine clearance so that the bar will be straight?

I think it would be important to design enough give into the bar (both in tension and compression) so that it will give before reaching the combined shear stress of the mounting bolts or tower sheet metal. Otherwise, if the vehicle were to suffer sudden flex from mounting a curb at speed etc., too stiff a bar may result in shearing of the mounting bolts. Most bars I've seen are not completely straight, even when they could be, and this may be so that they have enough flex in them to prevent shearing bolts.

Good on you for having a go at this - I think the available strut bars are way overpriced since most of the money for them seems to go into looks rather than function. I'm sure they work well, but I'd rather pay for just the functional aspects and not so much the artistic stuff. Each to their own I guess.

[Yahnozha]

Thanks for the comments so far on this piece. Ive taken another shot at this with some of the recomendations. As you can see the main height of the piece is now at 1-1/4" minus the bar that jets up at an angle.

Brian - I would like to know that dimension for the height of the bar to fit on a 2002 modle.

Yes this is a complicated design, but ease of manufacturing will be on the light scale, considering that large pieces of aluminium are expensive and take long to machine. Breaking it down makes it easier and faster to produce. It also makes for 2 universal pieces, the light green piece and the purple bracket. The dark green mounting piece will need to be made for each side.

What I do like about this design is that you hide the mounting bolts under the light green cap, just a bonus. Also, you dont want these 6 bolts nor the strut mounting bolts to shear, you want the bolt(s) holding the actual rod to shear and not caus any damage to the car.

I will still be elongating the holes on the light green piece for adjustability and alingment purposes, for each car is going to be slightly different.

On the eye bolt design, is that an added bonus to be able to pre load these bars? I could easily accomodate that with this design and make the eye bolts on the bar itslef.

Yes, im going for the straight bar all the way across, in case your wondering...the bent bar does ad some flex to the design, but flex is what you are trying to eliminate with the STB. Besides with a striaght bar I could engrave your name or some cool saying into the top of it, not to mention that it is a direct transfer of load from one strut to the other and that is what you are trying to achieve.

Yes, you can get specific sheer strengths bolts for assembly as to not damamge the strut mounting bolts in the case you happen to be trying to run down your g/f and hit a curb in the process..

More coments are welcome with the evolution of this...

Much Regards,
Pat
www.customsteel.com

[b-b00gie]

Pat, I'll try to take pics and measurements for you this weekend since I have to do some work and an oil change on the car anyhow...

[Yahnozha]

Brian - that would be cool, Im getting ready to post another pic of the design with the elongated holes on the bracket. I think it will work out better...but who knows..

Pat

[Yahnozha]

Alright, here is the latest with the design. Ive eliminated three of the holes used to mount the brace. Ive also made them elongated, this will give 15' of adjustment either way from center to mount the bar.

I think the only critical thing on here is the angled bracket, It may be too tall...gotta keep it under the hood you know.

So far the design is pretty clean and straight forward, let me know what you all think. Im going to be setting up to make the prototypes for this in the next couple of weeks. Id be interested if anyone wants to try a set out to give me some feed back on this.

Also curious to see if anyone has broken/bent a strut tower brace before???

Pat

[T4 Primera]

Well, you obviously know what you're doing and the design looks great. Hey I just noticed your url and realised I'd seen it mentioned in regards to the banners on the NZ primera club site.

I dont know if preloading the bar would be an advantage, however some length adjustability on the bar will help take up any slop in bolt holes and allow for variations from car to car and ease of fitment. This would allow easier dimensional tolerances for manufacture while preventing things rattling around.

With your modular design there is scope for adapting to other makes/models. By offering alternative base mounts and/or bar lengths and keeping the six-bolt-upper piece the same - the appearance of the brace will be consistent across all applications.

[T4 Primera]

Your first design mounted the bar with a single bolt in double shear which is just as strong as two bolts in single shear.

First design was also more suitable for inclusion of a swivel bearing end on the bar which would solve any alignment problems and could be threaded in and out of the bar for length adjustment. It would also save having to machine those three slots on the light green piece.

[Yahnozha]

Id have to agree with the single vs. double attachment points on the bar attachment, there really is no difference, but I do agree with your point on the adjustability of the length on the bar and it would allow for pre-loading if needed.

Here is another version incorporating the eye bolt attachment, it does lend to a more simple attachment method and makes it a little cleaner from a design viepoint as well.

Im still thinking the elongated mounting holes will allow you to position the direction of the mounting bracket to a striaght line shot to the other one, as to not introduce any "off axis" loads and stress the parts further. Not that it would matter...just my two cents, I guess well find out when the prototypes are made.

As for other makes and models...why would we want those Honda boys having something this cool.... But I see and appreciate your point...now If I could get the DigitalRacer boys to carry them....hum....

Yeah, that was me on the logo design, just killing some time and letting the creative processes flow...Ill be submitting some more in the near future.

Pat

[T4 Primera]

Please excuse the long post, just trying to approach this from an engineering angle ...

Any thrust along the bar is going to apply a torque to the upper ring via the purple piece. If this causes the upper ring to twist where the purple piece attaches to it, then another alternative might be

i) make the ring a solid disc (save machining but possible weight/aesthetic penalty)

ii) enlarge the base of the purple piece (now triangular in profile)where it mounts to the disc to spread the load over the whole assembly

iii) position the bolts of the disc adjacent to the base of the purple piece so that they better resist any residual torque (better leverage).

I wish I had your graphics to better explain myself ... picture a disc with a triangular block mounted on top. The rounded upper vertex containing the mounting hole is positioned so that the triangle "leans" towards the bar.

Put a hole thru the top vertex of the upright for mounting the bar and slot the thing for double shear as before.

The triangular shape has a base extending across most of the disc diameter and in line with the bar. This helps counter the torque created by forces from the bar acting over the vertical height of the bar mounting hole above the disc.

If you want to retain the ring shape, then extending the base of the purple peice to attach to both sides of the ring, in line with the bar, could help resist torque as well. Perhaps if the purple piece was a kind of lopsided and inverted "V" it may look better.

[P10DET]

I hope I can remember all my comments.......

First, ditch the carbon fiber unless you autoclave it. If you don't autoclave it, it won't have enough strength to be effective as a STB. Also, if the CF does shatter, it will make a mess. Autoclaved CF is sharp as hell. Stick with aluminum.

Your first mounting design was the best. Ditch the angled bracket. You're just introducing another failure point. Actually, it's likely it will move around and I wouldn't be surprised if the bolt sheared pretty quickly. That arm is going to work like a lever.

The part Sandy (T4) is trying to describe is called a spherical rod end or heim joint here in The States.

Shouldn't need to slot the ring if the design is good and you use spherical rod ends.

[enginerd]

I don't like that appendage extruding from the tower unless it's made from the same material as the tower in a single piece. Personally, I'd just have a tie-rod like end with a center link between the towers. That way, a large degree of adjustment could be made (not really necessary) and it would lower the cost. Another concern is the heigth of the piece. I'm not familliar with G-20s but I'd check the clearance between the tower and the hood.

[Yahnozha]

The weather finally let up enought for me to do some measuring on this beast...the over all height of the bracket looks good at 1-1/4" tall. I have to eliminate the angled bracket due to the lack of room, so Im going back to the origional idea (thanks P10DET).

I have made the ring and bracket all one piece as before, still going with the "heim joint" bar attachment method. I think I can eliminate the elongated holes for alingment purposes but need to make the bases and install them first to get the appropriate location for the mounting locations (I hope I made sense with that)

At this point, I guess I could make this all one piece, but man it would be too cool to cover up those holes...the sacrfice for design..maybe just a superficial plate that screws down just for looks...but if I did that the way pimp 20' bevel around the circumference of the base plate might have to be sacrificed...uuuggghh...the humanity.

The crossbar might have to be slightly bent to clear the engine, but I will know that for sure when the prototypes are built...speaking of, an air solenoid switch went out on my machining center today. Pissed me off, $320 + Next Day Shipping to get me up and running again, at least it wasnt the $1500 X axis motor this time...whew..

Once again, let me know what you think. The design is coming along nicely, and I want to thank all of you for helping out, and sorry for the long post.

Much Regards,
Pat