Questions on my upcoming chassi modifications and cage setup?

[J. Fast]

I pulled a front subframe from a 91TT to template a tubular K member. Is the front subframe the same for all years?

The rear suspension cross support that extends between the two towers, can I cut that out with my spotweld cutter suspension suppported or do I need to be frame supported on stands, or is that not a good idea unless @ brace it?

Rear subframe, going to use the same 91 piece to template from also. Will that bolt up to 2nd and 3rd gen chassi?

Completing welds at the A pillar hoop, I've taked to a few people who recc I cut the floor out and drop the cage thru the floor to complete the welds. Several others hook their wire and come thru the windshield opening. How hard is it to complete that weld or can it be completed with the windsheild still in?

The front crossbar from drivers side to passenger side A pilliars. Can I cut that and remove it suspension supported?

Any reccs, reasoning, or preference on building the cage and welding when suspension supported vs. frame supported?

This is a big time deal for me as it's a safety concern. Any input would be great.

[anyonebutme]

yes

yes

yes

drop the cage, I don't even like plinth blocks

yes

doesn't matter as much as you'd think. All cages done by my local guy who's the NASA midwest inspector are done suspension supported, and he's yet to see any measurable change in any dimension when jackstanded. No such thing as "preload" when it's welded.

I have lots-o-input, but it's not all applicable to all classes, so pick a class first unless you're going for a "TT" classless cage like Jon and Pete. I can argue door bar design and halo vs headache bar all day.

[J. Fast]

Excellent, thank you for that! I will be dropping thru the floor then.

Where are the best places to reference warpage or twist on the chassi as we're stich/seam welding, and putting on the cage? I'm thinking of places to weld pins or something to the frame for ref and measuring before, during, and after?

I would like to build to this spec... 2012 PPIHC Time Attack. Class and specific requirements are listed in the attached google doc's rule book.

Here's the 2012 rule book. >> https://docs.google.com/viewer?a=v&q...hMGQco0qrcsvwg <<

General Cage requirements are listed on 29. Class Specific Rules start on page 55. Additional class specific cage requirements are on page 59. I will follow the highest minimum diameter/thickness required between general and Time Attack's class specific requirements.

[anyonebutme]

For frame warpage, theres like 60 reference points for our cars, though I don't have a frame manual that lists the dimensions. Maybe the factory service manual has them somewhere? A frame shop will have the book. Otherwise, I'd just take extensions to the mounting points of the suspension, as frame warpage that doesn't move the mount points in relation to it's sister will not effect the car. front and rear subframe mounts and front strut towers are possible locations. Rear tower location don't matter as the suspension does NOT rely on them for locationing, those just hold the tops of the rear dampers still. In reality unless this is a body-in-white, it's not going to be perfectly inline anyways. More than once I've seen shops straighten brand new cars from the showroom floor while building them, and then get beat by shops that built from preowned cars with thousands of miles on them.

Seam welding: I've never worried about it, and just welded, putting out fires along the way, lol. I highly recommend building a rotisserie, it's pretty easy and will make your life SOOOO much easier doing this step. Can be made out of 2 cheapie engine stands from harbor freight and some steel tubing. Be sure to be careful and make it as adjustable as possible, as finding the balance point is hit or miss on an unfamiliar car. Having the car spin around on you will be more scary than running off a cliff edge at pikes peak, I guarentee.

I'll just hit the major points right now:

1. Get 6-point harnesses. Your family jewels will welcome you. Also, get one with swappable adjusters for pull up and pull down tightening, as sometimes only 1 method will work in a certain car. Also, 2" lap belts are the shit, I highly recommend. On similar topic: HNR's are a requirement. There's not many companies that make them these days due to everyone getting sued by HANS. If you use a HANS, use a HR seat! HANS does NOT provide side impact protection. For that matter get a good HR seat anyways. If you can, try before you buy. Some like the HANS, some like the DfendR (I'm one), some like the R3 hybrid, some like some other ones. SFI just started requiring recerts on HNR's every 5 years, FYI, so think about the ability of the company to do so before you buy, as some of the companies have been...eliminated...from competition and chose to just close their doors.

2. If you are as tall as me, you will have to modify the floorpan to drop the seat to get that 2" above helmet to main hoop height. Dimpling or cutting the roof subframe to raise the main hoop will help some. This means no more 3 piece driveshaft and no PST aluminum driveshaft, as you will no longer have a front carrier bearing mount. Welcome to my world.

3. Use an aftermarket steering wheel shaft bearing/support. Stock one is heavy, requires stock dashbar, and shaft length limits driver positioning. I like to move the drivers seat all the way back possible and use aftermarket pedal assembly, but requires more fabrication. Not a requirement, but while you're having to fabricate something here anyways, might as well do it all the way.

4. Add foot protection bars that go from front downtubes to firewall. They will hurt your feet in a wreck, but better to have aching feet than have none at all.

5. I recommend taco gusseting, gusseting is required throughout the "halo" by rules, but I'd also gusset the "window frame" and brace cage to A and B pillars if allowed. Tube gussets are fine, but tacos are lighter.

6. "dash bar" is required by rules that goes from downbar to downbar.

7. Pay attention to the mounting plate area rules on page 63. Vertical plates are counted and this can catch you up if you do the main hoop up against the subframe shelf. Speaking of this shelf, there's a semi-debate on whether it's a good idea to mount the cage on top of it or in front of it. As with all debates, nothing is a wrong answer unless proven otherwise, but some scruitineers frown upon that practice even if it is proven safer.

8. Adding a bar across the rear shock towers doesn't hurt, but it also doesn't help as much as some would think. SCCA prohibits this or adds "strut bar" points, so beware. Since the rear suspension doesn't care if the towers move other than affecting shock forces, don't take a penalty to add one. There's debate on whether to attach rear downbars to the towers to not, as the point is to hold the roof up, not the suspension down. If the tower collapes in a rollover, you just lost rear support, while the "floor" will not collapse.

9. Looks like an "upbend" is allowed to get the front downbar very close to roof, but check with the scruitineer before building. I guess a diagram would help be describe this. I'll draw something up later. You can even do this if doing a top halo, but you can't do it by the rules if doing a front roll hoop. Looks like additional A pillar support bars are allowed, like those popular in IMSA/FIA GT racing. Again, scruitineer is final word....redoing a cage sucks.

10. Door bars: 3 bar NASCAR style, 3 bar FIA (cross and "sill" bar), are both allowed, 2 bar NASCAR is NOT allowed in the racing class but allowed in the TT class. This is probably the most hotly debated thing in cage design by everyone. There are basically 2 NASCAR style and at least 4 FIA style bar designs to choose from, and each one has it's pros and cons. This will be tomorrow's discussion topic maybe. Note that in the PPHC TT rules, you can NOT completely "gut" the door inner structure like in most classes, but you can hack it up to clear the tubes as long as the stock inner door handle is in the STOCK location. Be sure to check this before you weld in your bars and close the door just to realize there's interferance with the stock door handle. NEVER "S" bend the door bars to clear the door frame. It flys in some rulebooks, but it's just a dumb idea strengthwise.

Hello, wall of text...

[J. Fast]

For frame warpage, theres like 60 reference points for our cars, though I don't have a frame manual that lists the dimensions. Maybe the factory service manual has them somewhere? A frame shop will have the book. Otherwise, I'd just take extensions to the mounting points of the suspension, as frame warpage that doesn't move the mount points in relation to it's sister will not effect the car. front and rear subframe mounts and front strut towers are possible locations. Rear tower location don't matter as the suspension does NOT rely on them for locationing, those just hold the tops of the rear dampers still. In reality unless this is a body-in-white, it's not going to be perfectly inline anyways. More than once I've seen shops straighten brand new cars from the showroom floor while building them, and then get beat by shops that built from preowned cars with thousands of miles on them.

Seam welding: I've never worried about it, and just welded, putting out fires along the way, lol. I highly recommend building a rotisserie, it's pretty easy and will make your life SOOOO much easier doing this step. Can be made out of 2 cheapie engine stands from harbor freight and some steel tubing. Be sure to be careful and make it as adjustable as possible, as finding the balance point is hit or miss on an unfamiliar car. Having the car spin around on you will be more scary than running off a cliff edge at pikes peak, I guarentee.

I'll just hit the major points right now:

1. Get 6-point harnesses. Your family jewels will welcome you. Also, get one with swappable adjusters for pull up and pull down tightening, as sometimes only 1 method will work in a certain car. Also, 2" lap belts are the shit, I highly recommend. On similar topic: HNR's are a requirement. There's not many companies that make them these days due to everyone getting sued by HANS. If you use a HANS, use a HR seat! HANS does NOT provide side impact protection. For that matter get a good HR seat anyways. If you can, try before you buy. Some like the HANS, some like the DfendR (I'm one), some like the R3 hybrid, some like some other ones. SFI just started requiring recerts on HNR's every 5 years, FYI, so think about the ability of the company to do so before you buy, as some of the companies have been...eliminated...from competition and chose to just close their doors.

2. If you are as tall as me, you will have to modify the floorpan to drop the seat to get that 2" above helmet to main hoop height. Dimpling or cutting the roof subframe to raise the main hoop will help some. This means no more 3 piece driveshaft and no PST aluminum driveshaft, as you will no longer have a front carrier bearing mount. Welcome to my world.

3. Use an aftermarket steering wheel shaft bearing/support. Stock one is heavy, requires stock dashbar, and shaft length limits driver positioning. I like to move the drivers seat all the way back possible and use aftermarket pedal assembly, but requires more fabrication. Not a requirement, but while you're having to fabricate something here anyways, might as well do it all the way.

4. Add foot protection bars that go from front downtubes to firewall. They will hurt your feet in a wreck, but better to have aching feet than have none at all.

5. I recommend taco gusseting, gusseting is required throughout the "halo" by rules, but I'd also gusset the "window frame" and brace cage to A and B pillars if allowed. Tube gussets are fine, but tacos are lighter.

6. "dash bar" is required by rules that goes from downbar to downbar.

7. Pay attention to the mounting plate area rules on page 63. Vertical plates are counted and this can catch you up if you do the main hoop up against the subframe shelf. Speaking of this shelf, there's a semi-debate on whether it's a good idea to mount the cage on top of it or in front of it. As with all debates, nothing is a wrong answer unless proven otherwise, but some scruitineers frown upon that practice even if it is proven safer.

8. Adding a bar across the rear shock towers doesn't hurt, but it also doesn't help as much as some would think. SCCA prohibits this or adds "strut bar" points, so beware. Since the rear suspension doesn't care if the towers move other than affecting shock forces, don't take a penalty to add one. There's debate on whether to attach rear downbars to the towers to not, as the point is to hold the roof up, not the suspension down. If the tower collapes in a rollover, you just lost rear support, while the "floor" will not collapse.

9. Looks like an "upbend" is allowed to get the front downbar very close to roof, but check with the scruitineer before building. I guess a diagram would help be describe this. I'll draw something up later. You can even do this if doing a top halo, but you can't do it by the rules if doing a front roll hoop. Looks like additional A pillar support bars are allowed, like those popular in IMSA/FIA GT racing. Again, scruitineer is final word....redoing a cage sucks.

10. Door bars: 3 bar NASCAR style, 3 bar FIA (cross and "sill" bar), are both allowed, 2 bar NASCAR is NOT allowed in the racing class but allowed in the TT class. This is probably the most hotly debated thing in cage design by everyone. There are basically 2 NASCAR style and at least 4 FIA style bar designs to choose from, and each one has it's pros and cons. This will be tomorrow's discussion topic maybe. Note that in the PPHC TT rules, you can NOT completely "gut" the door inner structure like in most classes, but you can hack it up to clear the tubes as long as the stock inner door handle is in the STOCK location. Be sure to check this before you weld in your bars and close the door just to realize there's interferance with the stock door handle. NEVER "S" bend the door bars to clear the door frame. It flys in some rulebooks, but it's just a dumb idea strengthwise.

Hello, wall of text...

Was considering making my own rotisserie. Possibly making two A frames and putting some sort or rotating collar with pinholes on it so I can lock it in place every 30 degrees or so. Figured I'd just put baseplates on it and put some drop-in anchors in the garage floor. Thanks for reminding me, I need to measure the height above the floor in the back of the garage so I can rototate the chassi. LOL, it would suck to spend all that time on the rotisserie and go to rotate and find it's too tall. ...so going to work on drawing something up for that.

Seats and Belts are good to go. I have two styles of Kirkey seats and 6 point RaceQuip camlocks. I was able to modify a Standard Kirky Bracket and build an adapter plate to allow the seats to be bolted in really low... and use the stock mounting. I'm 6' and have about 5" radius free and clear to the roof.

HNR's, I was thinking about going with an Intermediate Isaac. Still haven't made a final decision on that one yet tho.

Driver cavity, I do have a Wilwood inverted pedal assembly to put in. Never really considered moving the seat back and pushing the pedal assembly. I'll have to do some staring and thinking for awhile before I decide. Foot bars, yeah, got some feedback from one of my buddies that runs Group N Rally. He pretty much said the same thing.

If you would, point me in a direction for that steering wheel bearing support. I'm assuming I can buy it "made to order"? Does that include the components from the bearing to the steering rack, or do I have to make it fit?

Still researching, asking a lot of questions, and getting a lot of feedback on doorbars, routing, plating, and what not. I'm guessing there's a month or so of prep and getting a ton of extra crap out of the way before I go to town on the cage. I'll have a ton of questions about different loads on various panels and wether they're structural and/or can be removed or modified and what not.

I appreciate the cage feedback. 3 bar, style of bar, and opinion on Al, vs steel? Keep it coming!


Progress

Yesterday, I worked on removing the rear shock tower brace, sunroof holding mounts, and the speaker mounts. I like it, it looks way cleaner and will make for easy floor covering template later.





Next, I think I'm going to cut or remove the first layer of sheetmetal from the rear hatch latching assembly all the way to the door frame. I looked at it for about an hour or so, after examining it, I think I can get all the way to the outer skin and not lose any structural integrity. The exception will be at the B pilliar. I'll keep two layers there vs. three.

[anyonebutme]

Quick links as I'm leaving the house:

http://www.andrewsmotorsports.com/im...op/shaft_2.jpg

JEGS Performance Products 60740 JEGS Steering Column Mount & Steering Shaft Brackets

Borgeson Universal 670600 - Borgeson Universal Steering Shaft Support Bearings - Overview - SummitRacing.com

I'll try and find the all-in-one unit later.

[J. Fast]

Worked on it for about 4 hours this afternoon. As expected all the layers can be removed from the B pilliar back without compromising the frame. The first layer is just a filler for the interior paneling. The second can be removed from the B pillar all the way to the rear.

You can see the seam for the first layer I removed, it's the blade edge on the wheel well. I'm going to remove the entire seam and stitch weld it as I go.



Here's a better angle. You can see the second layer behind it.



Few more angles of how everything ties together behind the first layer.







I'm going to remove all the layers from the B pilliar all the way to the rear. Looks like I can take it all the way to the skin and not compromise the frame. I'll add support to the panels (if they need it) when I come back with the cage. Think it's okay to pull the second layer on the roof?

FYI to anyone interested, the first layer you see removed on one side weighs 38 pounds. The strut cross member weighs about 20 pounds. I think everything removed to the skin from the B pilliar all the way around the back to the opposing side is about 120 pounds. Nothing is structural either.

I'll work my way around and weigh everything an get a true weight number on it.

I'll keep checking as I go but after I finish the other side, and the rear, I'm going after the first layer above the door and roof. It looks like an inch or so of cage clearance can be gained. I might take the entire chassi to the skin and gusset the corners. We'll see if the chassi stays true ('knock knock').

Prolly 1500 spot welds to go... it's very tedious and time consuming to not burnish or breakthru the exterior. I think when it's done and all the tack welds are ground down and I prep everything for paint it'll look really clean. I'm very happy thus far.

[anyonebutme]

Just be sure to pick up all the suspension with the cage and youll be fine removing the "box" of the frame.

[J. Fast]

The "box" of the frame, is that the tunnel, first layer of sheetmetal, the intermediate layer (I'm calling it the 2nd layer of sheetmetal), or all three?

Can I take the door frames down to the skin?

[anyonebutme]

The strength of a unit body relys on not a sheet of metal, but on sheets that make "boxes" when welded together, same as aircraft contruction. The inside and outside layers are the stressed components, while the middle acts as "spacers" and supports for positioning. You'll notice at the roof and above the rear rocker for instance, removing the inner piece means there is no longer a continuous box section when you follow the stressline from the rear suspension to the front along the pillars. This weakens the structural rigidity along the transverse axis, and some reduction in twist as a concequence. With a well designed cage, this is not a problem, but without one it is, so before people start cutting metal out of their street cars, beware. You could technically remove all the inner and intermediate metal if your cage catches all the suspension pickup points (on our cars, subframe mounts and struttops), as then it'll basically be a "body on tube" chassis. Be careful here as if you decide to go racing, many will class those harsher than just a safety cage. NASA for instance puts those cars in the unlimited and race classes automatically, but I don't think you will run into this. Make sure your class allows tubes to pass through the firewall before having some get the front strut towers...

For what it's worth, when I was cutting my 92 in half to crush it, I cut completely through everything except the rockers on each side, including cutting the entire roof off and the floor/driveshaft tunnel, and the car was still strong enough for me to jump on it without failure. With rockers that stong, no wonder the spyders drive as nice as they do.