Targa people, would you be interested in...

[spencyg]

Ugh...you can tell by the conversations on this thread that only about 1.8 people here have any engineering background.

That brace looks more than adequate for the task of preventing racking across the targa gap and I disagree that any further bracing within the weldment is required.

I do a little engineering during my work hours.

Or a lot.

 

[Nick M]

You even spelled "a lot" correctly. Well done.

 

[Poodles]

A lot of the "shimmy" is simply the heavy windshield moving around...

 

[spencyg]

And the heavy windshield is moving around because what it is attached to is moving around. You need to box in all forces for everything to share the load. Without the top bolted in, the same load coming from suspension forces behind the targa and in front of the targa needs to be controlled by far less structure which isn't being supported by all the other components of the chassis. This simple little cross bar takes the forces from the front (translated through the windshield) and transfers them through the roof to the rear chassis. The same applies to the loads from the rear struts being sent to the front chassis. This is all pretty basic stuff and all cars with a removable top suffer from these problems. This solution available to targa equipped cars is both unique to this style of top configuration, and highly effective.

How many on this forum actually remember when the MK3 supra first came out? Because I do. I get the sense that there is a disproportionate amount of "youth" here...not a bad thing at all, but when it comes to a technical discussion of the core engineering behind particulars of our car (or any car for that matter), age and experience might prevail here.

Wasn't trying to be an ass here...but with that last sentence I may have failed. Apologies.

 

[Poodles]

Not gonna argue that it wouldn't help, cause it will Now I will say that the gussets are on the wrong parts of the X, besides that, the brace will work fine.

Most people get these cars with 150K+ miles on them, take the top off and go "omg it's a wet noodle!" They neglect to remember that things wear and make it worse. Hell, simply retorquing the subframes on my car had a significant effect on reducing ths "shimmy." Worn door hinges, worn bushings, and missed maintenance all contribute to the issue. Not to mention how many other cars of that decade that were far FAR worse with the top missing (hell, even with the tops on).

 

[Satan]

My car definitely feels better with all of the suspension changes (poly bushings, new springs/struts, SF bushings, etc).

The wing definitely provides a certain rigidity that I can tell is not there w/targa off. Because my suspension is fairly new & stiff, I can still feel some flex in the body moreso, I think.

 

[Bleakvoid]

I'll admit to only being a handful of months older than my car (Manf'd 9/88...I was 5/88), but engineering is kind of an obsession of mine. Yes, I realize that there's no better solution than having the top bolted in, and possibly reinforced. But you know what? I enjoy my pseudo-convertible top. A lot. Especially because there's not 350+ pounds of moving, failure-prone parts and a cloth rag to cover it in the trunk.

Therefore, I'll take what I can get. I'm going to see about my subframe bolts when I take the stands out from under my mk3, and will probably end up with a brace for track use. Otherwise, I'll be using strut bars and an Xbrace to make up for having a worn chassis with 130k miles for the street.

 

[spencyg]

Not gonna argue that it wouldn't help, cause it will Now I will say that the gussets are on the wrong parts of the X, besides that, the brace will work fine.

I completely disagree. The whole point of the brace is to maintain the dimensional integrity of the chassis. This is being done by making sure the rear bolt point on the driver side as it relates to the front bolt point on the passenger side maintains a relative alignment to the opposite two points. The concept in absolutly no different than EVERY SINGLE PIECE OF SCAFFOLDING used in the entire world. Look at the X brace between each rectangular frame. It is pinned in the middle to make sure those two diagonal points can't move past each other at their intersection. This same method is being used here, and those gussets are spreading that rather significant load as discussed previously to a wider area of the tubes. They are as critical to the correct operation of this component as the bolts which hold it to the car.

OK. I'm done.

 

[Poodles]

The gussets are on the front and back, not the sides where they should be. The front too mounting points won't be moving in relation to eachother, there is no stress there. Same with the back.

 

[spencyg]

That would only be an issue if we thought all of our cars were folding in the middle when the targa was removed. It isn't, its twisting. The bar is meant to prevent twisting between the front half of the car and the back half. The bars do nothing to prevent folding as that would require straight bracing bolted together with far more than a few M10 bolts.

 

[Poodles]

True, but you said they were in the right place when they aren't.

 

[winsauce]

The gussets are on the front and back, not the sides where they should be. The front too mounting points won't be moving in relation to eachother, there is no stress there. Same with the back.

why is the general concensus that steel bars distort and buckle like pvc pipe?

are you an engineer? im not... thats why im not making assumptions about where the gussets need to be.

 

[Poodles]

It's common sense...

 

[spencyg]

Sorry, but your common sense is flawed. I'm done trying to explain this. I would personally buy these bars without hesitation if I wasn't intending on fabricating my own anyway.

 

[Poodles]

I completely disagree. The whole point of the brace is to maintain the dimensional integrity of the chassis. This is being done by making sure the rear bolt point on the driver side as it relates to the front bolt point on the passenger side maintains a relative alignment to the opposite two points. The concept in absolutly no different than EVERY SINGLE PIECE OF SCAFFOLDING used in the entire world. Look at the X brace between each rectangular frame. It is pinned in the middle to make sure those two diagonal points can't move past each other at their intersection. This same method is being used here, and those gussets are spreading that rather significant load as discussed previously to a wider area of the tubes. They are as critical to the correct operation of this component as the bolts which hold it to the car.

OK. I'm done.

That would only be an issue if we thought all of our cars were folding in the middle when the targa was removed. It isn't, its twisting. The bar is meant to prevent twisting between the front half of the car and the back half. The bars do nothing to prevent folding as that would require straight bracing bolted together with far more than a few M10 bolts.

Sorry, but your common sense is flawed. I'm done trying to explain this. I would personally buy these bars without hesitation if I wasn't intending on fabricating my own anyway.

Yes, you're done making yourself look like an idiot. The gussets would only work in the way you think if they were too straight bars overlapping eachother like on scaffolding, not meet at the intersection. Not to mention the twisting force is 90 degrees to the gussets making them worthless in your example. The only force acting along that plain is the compression force, which yes, does exist. As already mentioned the gussets are in the wrong place to prevent it. I will say there are some forces along them, but it's only of the the 3 axis being loaded.

Quite frankly, the gussets don't even need to be there, the forces are minor (the targa is not that strong as it's made to flex so it properly seals).

 

[winsauce]

For a mod you can be a pretty useless troll at times...

Grow the hell up poodles stop the name calling, and please stop making comments on topics you are applying your "common sense" to. Where are you credentials? Are you an oak tree mechanic? Did the effing squirrels tell you how it should be done? If so, make your own brace... Please show me how much better it is. You’re not helping anyone by posting garbage like you have been. Let’s see an alternative design with some supporting data?

Either the bars work, or they don’t... this needs tested, not talked about; and if it’s not been tested on your car then stfu about how useless the gussets are to prevent the twisting force. it’s all bs trolling and needs to stop. show me data that its wrong, show me stats, where are your test results? You even said yourself:

Quite frankly, the gussets don't even need to be there, the forces are minor (the targa is not that strong as it's made to flex so it properly seals).

So who gives a damn at this point what you think about the gd gussets if the bar is strong enough w/o them?

Does this style bar do what it was designed to do?
We don’t "know" anything yet as nether if us have tested the brace, or been presented with definitive and tested results...

I "think" yes, I’ll either buy this model or fab my own...

You "think" not, so after you pull your head out of your ass
step1: dont buy it or make one like it...

step 2:most importantly gtfo of this thread you attitude is blemish here & no one gives 2 squirts of piss what you think is "common sense". There is no room for assumption in an engineering application when you’re not a gd engineer.

There’s just something in your arrogant attitude that brings out my inner keyboard warrior. So here comes my ban for calling you out yet again...

Konichiwa Bitches ::hang::

 

[Greek]

Yes, you're done making yourself look like an idiot. The gussets would only work in the way you think if they were too straight bars overlapping eachother like on scaffolding, not meet at the intersection. Not to mention the twisting force is 90 degrees to the gussets making them worthless in your example. The only force acting along that plain is the compression force, which yes, does exist. As already mentioned the gussets are in the wrong place to prevent it. I will say there are some forces along them, but it's only of the the 3 axis being loaded.

Quite frankly, the gussets don't even need to be there, the forces are minor (the targa is not that strong as it's made to flex so it properly seals).

I had to.

 

[Poodles]

:icon_roll

 

[suprarx7nut]

Those gussets have got to be at least a little helpful. Maybe not the absolute best position but still helpful and surely not "useless".

They help to hold that center section together, REGARDLESS of whether they are along the major or minor axis. If the front and back get pulled apart, the gussets are under compression holding the x on place. If front and back are pushed together, gussets are under tensile loading. Twisted clockwise or countercloclwise I'd need to work it up in cad to see what it actually does or whether putting the gussets along the sides would be better.

Provided the steel bars don't flex when under compression any x design should be helpful.

Oh and by the way, I am literally a degreed mechanical engineer from an abet acredited university.

Poodles, take it easy and like winsauce said, don't preach your "common sense" if you don't have any data or principles to back it...

No hard feelings, just sayin.

Sent from my HERO200 using Tapatalk

 

[Clint]

WTF is going on here! Why was this old thread bumped!