Targa brace
 

I started this thread once before but wasnt ready to share the info at that time, so Im kinda redoing it.

Ok so some of you know Im having a targa brace made to fix that squishy shimmy feeling you get when you have the top out. I should be getting it this afternoon. I am going to try to get pics taken before I prep and paint it (future ones will be powdercoated or chromed). These should be priced under $100 even for a short run, though it really just depends on the cost of powdercoating or chroming.

Im really excited about sharing this with the community and I will try to get approval for a group buy on these, but in the meantime, Im interested to hear peoples opinions on the idea. If you own a hardtop please state that in your responce as I will dismiss your opinion entirely (ROFL, just kidding...Im still interested in hearing your opinions too)

In case you have no idea what Im talking about, the brace will bolt on to the stock locations of the Targa top and connect the front windshield to the roof portion via 1'' tube steel bars. I designed mine a little different than the so called "X-Brace" in that mine is connected via two "U-shaped" bars creating more of a t-top look and feel.

So there ya have it...all opinions on the subject are welcome, and feel free to point out any flaws in my logic. :cool:

Targa Bars
 

I have a set of Targa Bars from years back from the S.O.G.I. group buy! They work well. Post pics of yours, would luv 2 C them!

I may buy some when i get my turbo. I have a ? for targa owners tho...Is the car noticeably more flexible with the top on than the hardtop version? and does the targa top include any internal bracing or is it just a panel?

I actually cant tell your from experience, but from what I read, the targa is no more flexible as long as the top is on. The top itself doesnt have any cross corner braceing that I can tell, but the window sill portions are very stout, and there are thicker portions at the front and the back. Basically its a big rectangle with sheet metal over it from what I can tell.

I have a targa supra and I was surprised at how much flex there is in the body. I prefer driving with the top on because of the difference. Every little bump really can be felt as the chassis flexes. It is not so much the sensetivity of the car but the way the car twists. You can see it in the way the windshield shakes compared to the rest of the body.

If the stiffener really works then I would like to get one. I think the car should be driven with the top off..........and look like the top is off. Maybe a strut bar would help some, but I don't think that is where the problem lies.

Russ

Mk3s dont have struts, so your twisting doesnt lie there, And strut bars are completely useless on these cars. But yah anything connecting the windshield to the rest will def help out. Even just a little bar, In the middle, Like a t-top, as weezl suggested.

Got my bar...Im not 100% happy with it, but its nothing that cant be fixed. Im going to go with what he made me for now and see how I like it. When I picked it up from him we talked about a few options. I can definately see where we can improve it. Tomorrow I will prep it and paint it and take some pictures...should have those up around lunch time.

Just me again
 

Well I have a targa top on my 1987 Turbo, and well for all your Non-Targa people...well bow down to us...JK, naw....the targa top, when removed makes the car ENTIRELY flexible....like you take a corner and you can see it flex...well I guess at least when >I< corner you can see the flex....and that is why I only cruise with the top off.

A couple weeks back I made the mistake of taking the top off, and then racing with the car. The next time I put the top back on (Later on that night) I noticed a MAJOR marked change in how easy (Or I should say hard) it was to bolt down the targa top.

NOTE: The Supra targa top has four "bolts" that hold it down, they are more like big screws that anything else. These bolts when fastened down completely, and correctly, will make the whole targe top a "structural" peice, and MAJORLY reduces body twist, and improves handling.

I have bent/twisted my frame now because I decided to race with the top off, and now I just have to live with a hard-to-bolt-down targa top. However with that all said, I don't think that your option would work for me, not for the fact that I have body flex, and damage to the chassis, its the fact that I hate the t-top look, and honestly the FULL open roof was a selling feature for me.

I have a question to ask off of that...Are the lower mid body stabilizers able to do the same as your brace, or would a combo of both, help me the most. (I think I know the answer to this one)

Well again, I do love the fact that you have designed a part FOR the supra. I want to think up creative, and effective ways to improve the temp of the supra intake, and also ease of flow. My brother builds custom exhaust systems, and manifolds....anyways, he does all my piping needs, and he is damn good at it too. So I basically have a product engineer...and I have the ideas.

Great job to all who have created custom parts to better their supra.

If your talking about the do-luck center bar, (the one that follows the floor just in front of the rear seat) from what I read it wont do alot for twist, its just not designed for that. It does have some resistance to twist thought so long as you actually use both bolt positions (alot of people dont) because then the bar acts a little like a torsion bar. Would both work? yeah, in combination they would be great for stiffening up out Targas.

The targa bar is meant to do two things:
First of all, look at your car from a profile. Essentially its a big flat triangle. When you remove the top you are basically chopping the top off a triangle, making it no longer a strong structural shape. The front and back sides of the triangle are going to want to come together to complete the shape again and the only thing stopping them is the rigidity of the bottom side. So, Im filling that gap again.
Second, take a box with a lid on it...a nice flat rectangular one works well for this demonstration. Apply a twisting force on it from corner to corner. It should be pretty resistant to that force. Now take the lid off of it and try it again...not as resistant. Thats because a rectangle is basically just two triangles. So your lid is resisting the torsional load.
Side note: if you fabricate a bar that crosses the center line of your box...just how much do you think its going to do to resist either of these forces?

And dont be too quick to condemn the bar because it approaches T-top...give me a few hours to clean it up, prep for paint, and get a couple coats on it...I WILL have pics today sometime

Cool. I wana see it! And yes you are totally right about the flex theory, There is nothing you can do to make the car as strong as when it has a roof.

I dont know about that...lol wait till ya see what I got, this thing is friggin stout!


ok first picture...but its too soft to take down and put on the car yet so use your imagination hehe

http://home.comcast.net/~kthaney/files/Targabrace1.jpg

looks nice, But it doesnt look like very stiff, How thick is that tubing? the ends are good but i dunno about that square

More pics:








http://home.comcast.net/~kthaney/files/targa2.jpg


http://home.comcast.net/~kthaney/files/targa3.jpg


http://home.comcast.net/~kthaney/files/targa4.jpg


The Tubing is 1'' and the plates are 1/4'' Trust me, its stiff!


But I also want to say that this is my prototype. I actually do have some changes that Im gonna make. Its hard when you draw a template and discuss something verbally with a fabricator, and not be there when he makes it. On the next generation the backs of the tubes will come all the way to the rear mounts and the tabs will drop down off the bars. Then the back plate will be gussetted to the backs of those bars. Also were gonna laser cut the Mk3 "supra" logo into the center of the front plate.

If anyone else has any suggestions for changes please feel free to speak up.

Well, it looks pretty good! Have you driven it yet and can you tell the difference between the targa top and your brace? I mean does it seem to stop the flexing?

Russ

I cant tell the difference between having the top in or the brace in...meaning it got rid of all my shimmy problems, at least at freeway speeds. I have a favorite road up into the coast range just west of my house. I plan to take it up that full tilt tomorrow and report my findings.

Great! Let us know how it turns out. I bet other targa owners would like to ride with the top off and not feel all the flexing, I know I would, especially on these rare days here in the south when it is perfect weather to drop the top.

Russ

I retract my statement
 

I will admit, that looks so much better than what I originaly thought. How much for one of those? I could see me putting that on my car, if I painted it black or something.

Suggestion
 

Alright, well I have been thinking, and here is a change that I would also incorperate into your next wave of prototypes.

At the front of the brace, where it is mounted onto the front "bolts". I would suggest that the bars also stretch out to cover those bolt holes. Then the top of the tube would be great, shiny, and normal...but if need be there can be a small hole drilled from the bottom of the brace, to allow the "bolts" to go through. That way...lets say....you do a psycho neutral drop, or go flying around a corner (Well very unlikely around corners or neutral drops....). However if in an accident, the spot where that brace unloads all its forces....could tear that tube right off the front plate.

If it were to be my way, you would get maximum strength, and support. So if you change the back, and do the front...you could greatly increase is rigicity.

There is one thing that I want to ask you. Does that brace fit into the targa top holder? It's kinda pointless to have that if when you don't need it (And lets say if it rains) you need a spot to put it, and to be able to use the Targa Top as well.

yes it fits into the spot where the top stores.

Bends aren't very strong, though. an x-brace would be ideal for this application.
it looks alright though. it just looks too decorative to be that functional.

by no means am i bashing though. I am very jealous, as I can't fabricate, and that looks very well made. If it works, more power to ya.
Good job :bigthumb:

I hear what your saying about the X-brace, but if you take a closer look at it you will see its welded where the two bar meet in the middle, so essentially this is an X, there just happens to be some shape to that X. Yes, a straight bar will distribute load better than the bent bars, but with 1" tube steel its very solid feeling. I also didnt intend this to be a racing bar, its designed for street use, and so far it has done exactly what it was intended to do...stop targa shimmy!


But I appreciate your critique...its valuable input.

Hmm yes the tubing does look thicker when its on the car. It looks like smaller tubing when its hanging there. As long as it gets rid of the shakey-ness, that means it works. lol. It does look pretty good too, in a cosmetic way

Looks can be decieving...it has exceeded my needs and expectations...Went to Portland and back today (180 miles round trip), took her up to and past my usually shimmy zone...NONE! felt like driving with the top on.

Again I stress, this wasnt meant to be for racing, its a street use item...but I would be willing to bet even an autocrosser would not be able to tell the difference between having this on or thier targa on.

Regardless, the reception has been good, so in the next week or so Im putting in my order for at least 10 of these.

i agree 100%, and after looking at pictures of the meet, it seems to go well with the car.

Honestly, I think that it's just because it's painted white. It sticks out. If it were painted black, I think it would look better.

Also, it works. That's enough said right there.

You should get a tinted lexan/gass cover made and put it one of those braces too, The its just like T-tops. I would love a clear targa cover... BTW, ever get a final cost for it? ill get one one of these days

I like the idea of the clear cover! Also I would like the brace too, but I will paint mine black, but if they do get ordered will we have a choice in powdercoating colors?

Thanks
Russ

ive also been thinking of a sort of brace for my 87t when i get it rolling. i was thinking something basic and not bashing but i dont really like the ttop look. also something to think about, having a brace made that you can have on and then put the targa top on also. i mean say you have the brace on and it starts pouring rain, all you have to do is just throw on the top instead of having the remove the brace and the then put the top on.

thats what the clear cover is for!(plus some weather seals)

Well its good to see some thought out discussion on the topic. Certainly there is room for mods on this, and anyone with a little imagination and some "know how" could make it work. But Im going to leave mods up to the people who get one of these for now.

As for finishing, I have decided that they will come unfinished. It saves on ititial costs and keeps my handling down to a minimum. As soon as I hear from a Mod I will pass on information as to how to get your hands on one of these.

brace questions
 

thanks for sharing your creation with all of us! that's a great idea you came up with. Can you answer a couple issues about the design? 1) how much does the entire brace weigh? 2) where the brace sits and touches the existing rubber gasket weather stripping on the front and back parts of the roof, is there additional weather stripping on the underside of the brace to make contact with the original weather stripping? (concern about the bare metal damaging the existing weather stripping).

thanks in advance for your clarification

What if you took the 2 end plates that you have, And just ran parallel tubes from front to back along the windows, With little gussets to prevent it from bending? It would just be like if you cut a sunroof shape out of the targa top to simplify it. i was doing some mechanical engieering research, And the force applied to the roof section isnt what i thought. Its the obvious front to back (windshield and rear section trying to touch each other), But it would have to apply the same force for the car to twist, unlike the side to side bending i thought. The front and rear sections of the car generally pretty stiff already, So they will not bend on their own. They Just allow the car to bend at its midpoint. So All you would need is the brace to be stiff front to back, Not torsionally or horizontally. For example...hold a block in your hand (like a lego, box of food, Anything and try to move your hands front to back. It makes the box want to spin, And apply force front out towards your hands. That means you could make that thing way smaller and it would do the same job lol. Sorry if this is boring...

Well to answer some of those questions:

The Brace weighs 18lbs. (The targa top weighs 26) There is not extra weatherstripping on the rear bar where it rests on the factory seal. The way the top bolts down there is no rubbing happening there so I dont see how it would wear the seal any more than putting the top there.

Isphius, I know what your saying but there are at least two reasons why what you mentioned would not be something I would want on my car. First of all, the point of the bar as its designed is to allow the driver the feel of having the targa top off, while maintaining chassis rigidity. So a bar going essentially across the top of the door glass would in my opinion not be very elegant. If you have a targa you know how when the top is out and you go to sit in your car, you can grab the front windshield and sort of slide into the seat....no ducking under the roof...I like that and want to keep it. Secondly in regards to your description of the kinds of forces involved in chassis flex and which direction you need to brace against, your not entirely correct. Yes you definately want to brace against the action of the windshield and the roof coming together, but in terms of the most benificial to handling of the car, the twisting action is by far the most important, and the reason is pretty simple...sway bars.

Sway bars work by linking both sides of the suspension together. Basically doubling the spring rate of any given corner, by distributing the force to the other side through the sway bar. This creates tremendous forces laterally AND diagonally across the vehicle. When the targa roof is in place it bears the load of these forces across its structure, essentially connecting not only front to back, but front left to back right and back left to front right, etc.

By welding the two curved bars in the middle I provide a transfer point for this stress in the middle of the car, (the two big "U" shapes become one "X" shape).


Cliff notes: bar is 18lbs, no wheatherstripping (doesnt need it) bar needs to be the shape it is for chassis strength (door bars would look ugly and not bear the load properly)

Well yes thats explained well, But what i was saying is the forces are applied to that section of roof differently than i thought (remember up there me saying it looks too wimpy, because i thought it was a bad shape, but now i realize its just fine). And I do know what you mean about the sliding in thing, It is fun (i had an 83 trans am with t-tops and a convertible lebaron to drive before) But I was thinking that itd be cool Just because there is nothing above you. I will try both out when i get to drive my turbo around (its a targa). I need dam money to finish it!

Wondering
 

I am wondering how much for the brace..or have you not ordered a whole slew of them yet?

Anyways, I am interested in that...I need something like that, for what it was meant to be...a targa top feeling opening...

I am having some changes made to the design. I should be getting that back in the next couple of days. Once I do I am going to order 20 of them and have some for sale. I may already have the first 20 sold already because of the interest on another forum. I'll try to be able to offer a few on here, but I may not have any until the second run of 20 is placed (about 3 weeks from now)