BUILD-OFF CHALLENGE: Tygaboy's '75 LS3, It seemed a good idea at the time... Options

[stevegm]

Interesting idea. It should provide some stiffness, without the bulky full overhead cage.

[Cairo94507]

Now that is a very cool way to stiffen the car and do it as low-profile as possible.

[Cracker]

Very nice Chris...have it running at WCR! (IMG:style_emoticons/default/shades.gif)

Tony

[worn]

That said, I also wanted to hide as much of this "cage" as I could. So I'm trying something a bit different. A "through the firewall" design!

I like it a lot, but with my flexible car I get noise as the targa top wiggles against the bar. The main flexure I should think would be a bending of the longs open and shut. Sorta like when they fail and the door gap changes. The more you make the bar fore and aft strong and tied in the better. Also you would want to fight twisting motions between front and rear. Instead of a single bar you might try smaller tubing but more truss work. But maybe not since you want to have it bolt in.

I very much like the ideas you have and also your shop!!!! I like my bead roller too.

[914forme]

Very nice bar tuck. If your not planning on running anything up the logs, cut a slit in the lower rear firewall, and extend stiffing all the way from the front to the rear suspension console.

I would also highly recommend 914 LTD outer log kit. Brad's kit will make your car stiff, runs from the front log all the way back to the rear suspension console. I can jack inside of my car up and the back, and lift three tires off the ground. It also only twists about 1/8" That was with a Roll bar, and petty bar installed. Have not tried it with out the roll bar and petty bar.


You could also go full steel top, or bolt down your fiberglass top, and add re-enforcments to that to to help out.

I checked a 944 out, 18ga metal, and very similar design to the 914 A-pilars. though the Gas had a re-enforcment added to the lower A-pilars.

You can also build a box section going down the center of the chassis. Think Lotus back bone, very strong, and can be made very light.

You are on a very slippery slope.

BTW, LS3 excellent choice (IMG:style_emoticons/default/aktion035.gif)

[tygaboy]

Very nice bar tuck. If your not planning on running anything up the logs, cut a slit in the lower rear firewall, and extend stiffing all the way from the front to the rear suspension console.

I would also highly recommend 914 LTD outer log kit. Brad's kit will make your car stiff, runs from the front log all the way back to the rear suspension console. I can jack inside of my car up and the back, and lift three tires off the ground. It also only twists about 1/8" That was with a Roll bar, and petty bar installed. Have not tried it with out the roll bar and petty bar.


You could also go full steel top, or bolt down your fiberglass top, and add re-enforcments to that to to help out.

I checked a 944 out, 18ga metal, and very similar design to the 914 A-pilars. though the Gas had a re-enforcment added to the lower A-pilars.

You can also build a box section going down the center of the chassis. Think Lotus back bone, very strong, and can be made very light.

You are on a very slippery slope.

BTW, LS3 excellent choice (IMG:style_emoticons/default/aktion035.gif)

You're stealing my thunder! The plan is to remove the stock tunnel and build a taller tunnel structure. I want to get the Boxster shift lever up nearer the steering wheel so kill two birds...
And I already have the 914 Ltd kit but not sure I'll need it with the inner long stiffening and the stiffening cage. We'll see. I can always add it later.

[tygaboy]

CHASSIS STIFFENING: Front Hoop/Door Bars

In keeping with the "hide as much as I can" approach, I bent up my front hoop (if something 9" tall qualifies!) and started trial fitting.

No, that isn't the real footing. It's just blocking the heater hole...

Initial fitment suggests I have plenty of foot clearance, can remove/install the steering shaft and even run the stock fuse panel, if I wanted (I don't).

It lines up nicely for a bar that will run from the hoop corner, through the heater hose hole and tie into the front shock tower.

[tygaboy]

CHASSIS STIFFENING: Con'd

Next, I started on the door bar. I haven't landed on the final height. Taller = stiffer, but again, I want it to be as easy as possible to get in and out.
Comprise is the order of the day on this design.

The pics show an overall height of 5" to the top of the bar. At this point, I think that's as high as I'd want to go.

I'm not final on the design in terms of the drops to the long. It'll be two or three, I'm just not sure. Here's a pic of each. (Note that I hadn't yet coped the drop supports in that 2nd pic.)

One of my race car fab buddies is coming over later to take a look and make recommendations.

[Rand]

I don't think you need three verts. My choice would be the outer spacing, the middle is doing the least. The last pic. Remove the middle.

[Cracker]

Chris - You don't need to have your bar that high - consider what I designed for you below (and if followed) - never look back.

The center support is important and I would not eliminate it from the design. The gussets at each end upright are absolutely necessary and should be implemented. Call me if you need to discuss.

I too will be re-configuring my cage in the next year or so - converting it to a more "hot rod" style like your car. I won't go any higher than the 4.5" (and probably even lower) from top of rocker to top of bar I've illustrated below when I do it (JMO).

Keep up the good work.

Tony

[tygaboy]

Chris - You don't need to have your bar that high - consider what I designed for you below (and if followed) - never look back.

The center support is important and I would not eliminate it from the design. The gussets at each end upright are absolutely necessary and should be implemented. Call me if you need to discuss.

I too will be re-configuring my cage in the next year or so - converting it to a more "hot rod" style like your car. I won't go any higher than the 4.5" (and probably even lower) from top of rocker to top of bar I've illustrated below when I do it (JMO).

Keep up the good work.

Tony

Now that's what I call "Community Support"! Personalized, no less...
Thanks Tony!
And I agree, the height needs to come down. Mostly because at 5", you can't open the door from the inside - the bar interferes with the handle. So that's going to determine the final height. Looks like about 4" to the top of the bar.
And my race car buddy did come by. I believe I now have a final design for the entire cage structure, floor and cross bracing and a cool tunnel!

More soon.

[tygaboy]

Oh boy. oh boy... is this going to be a full weekend in the shop!
Today, I got the blanks for the inner long stiffener. I got two 10' sections of 16 ga bent with a 7/16" inside radius. This is just a tick tighter than the corner radius of the long itself. I wanted to err on the side of tighter as too big a radius would cause the stiffener to rock on the long.

One leg is 4.5" and other is 7". This will allow me enough material to do the cabin as well as up the long, past the suspension console.

LOTS of (IMG:style_emoticons/default/sawzall-smiley.gif) , (IMG:style_emoticons/default/smash.gif) and (IMG:style_emoticons/default/welder.gif) for the next couple days.
And yep, I'll weld slowly, cooling as I go. But I sure am looking forward to having the floor and firewalls back in!

So, here's what a custom inner long stiffener looks like before the "custom" gets applied. (This has to be in the top 10 for "Most Boring Build-Off Challenge Picture"!)

More pics tomorrow as I start fitting!

[Mueller]

I'd throw a seat in there 1st and test how much of a PITA it is going to be getting in and out of the car before settling on the height of the horizontal bar.

[Rand]

Curious what your thoughts are on simply running a tube from the rear shock tower straight to wherever is the best point in the front wheel well inside. One simple tube for maximum triangulation, no need for all the extra bits in the truss design.

[tygaboy]

Curious what your thoughts are on simply running a tube from the rear shock tower straight to wherever is the best point in the front wheel well inside. One simple tube for maximum triangulation, no need for all the extra bits in the truss design.

I'm pretty sure that angle would make it tough to get in and out. If I remember, I'll mock that up and see how bad it might/might not be. Worth a look. Thanks for the idea!

[tygaboy]

I'd throw a seat in there 1st and test how much of a PITA it is going to be getting in and out of the car before settling on the height of the horizontal bar.

Great minds... I've been doing just that with my assembled '74. It'll be at least 1-2 inches lower than what's pictured.
And you're in Antioch? I get over that way semi regularly. We'll have to meet up.

[Rand]

I'm pretty sure that angle would make it tough to get in and out. If I remember, I'll mock that up and see how bad it might/might not be. Worth a look. Thanks for the idea!

Could be. But look at Sir Andy's car. His is easy to get in/out of. More swooped, but reality is, a bar like this doesn't interfere as much as you'd think. Sometimes it's actually easier to get in and out using the bar. And it triangulates the huge miss behind the firewall! That's an important part of this car, especially when you consider the worst rust weakening happens behind the firewall. Could also run an X tube to front suspension points.

Real cages and reinforcements have already been engineered. This is just brainstorming. But I figure this one red tube does more than all the black ones combined with less weight and effort?

[Dion]

Fantastic fabrication. Way to go Chris. I'm paying attention here:-)

[Mueller]

I'd throw a seat in there 1st and test how much of a PITA it is going to be getting in and out of the car before settling on the height of the horizontal bar.

Great minds... I've been doing just that with my assembled '74. It'll be at least 1-2 inches lower than what's pictured.
And you're in Antioch? I get over that way semi regularly. We'll have to meet up.

Yep, in Antioch....actually enjoying an IPA from Lagunitas Brewing Co from up in your area (IMG:style_emoticons/default/beer3.gif)

Let me know when around, I'll clear out some space in the garage so you will not trip too badly on all the junk I have ! (IMG:style_emoticons/default/smile.gif)

[tygaboy]

I'm pretty sure that angle would make it tough to get in and out. If I remember, I'll mock that up and see how bad it might/might not be. Worth a look. Thanks for the idea!

Could be. But look at Sir Andy's car. His is easy to get in/out of. More swooped, but reality is, a bar like this doesn't interfere as much as you'd think. Sometimes it's actually easier to get in and out using the bar. And it triangulates the huge miss behind the firewall! That's an important part of this car, especially when you consider the worst rust weakening happens behind the firewall. Could also run an X tube to front suspension points.

Real cages and reinforcements have already been engineered. This is just brainstorming. But I figure this one red tube does more than all the black ones combined with less weight and effort?

Interesting... My initial reaction is that this seems worth a much closer look!
I do want to clear up your comment (bolded above) that what Tony's design (and mine) have that isn't shown in his drawing, are tubes that do triangulate from the roll hoop back to the suspension point. Not picking on your perspective at all, just want all facts known. (IMG:style_emoticons/default/smile.gif)