Im not sure which body kit you are looking for but this guy might have a NOS setup for you. He's in Fresno

Neat project.

For mounting the suspension, what are you using for a datum or reference plane to make sure the a-arms are not tilted too far forward or back? Any part of the suspension that is supposed to be parallel with the floor pan?

I've really thought it through and finally came to the conclusion that a modified 916 look is what I will do. I will extend the 916 flares enough to cover the 245/18 front tires and 335/18 rear tires. I have thought it through though as I want to stuff the wide tires but I don't want a ridiculous bulge at each corner. I have a couple of tricks up my sleeve to accomplish this though. Also the 996 suspension will make this car to have a 5" wider track in the front and a 4.8" wider track in the rear. It's interesting that the wheelbase of the 914 is 4" longer than the 911??

I will be building a chassis table. Also I have the 996 on hand to compare the measurements. I will be putting all of the measurements into software that will tell me what the instantaneous roll center (IRC) of the 996 is. Then I can make sure that I am not lowering the IRC. If anything I might set the suspension cradle of the 996 further up into the 914 chassis to lower my CG. When I place the 914 on the chassis table I will carry out a twist test to see what the torsional stiffness of the 914 is before I add the 8 point roll cage. I have structural software to design the roll cage as well.

whats the smallest wheel that you need to clear the brakes? I would aim for that size. 18s are way too big for a 914. 17 would probably look good with that wide body and still fit over the brakes

Is it your opinion that it is too big because of your preference or that the wheel is too big and won't fit. If it's just your preference I can respect that. However if you're saying that the wheel is too big then ponder on this. The original 914 wheel rolling diameter for a 914 is 25.4" the 335/30-18 rolling diameter is 25.9"??? Also as they say a picture is worth a thousand words see the attached picture which shows a stock 914 wheel next to a 265/35-18. As you can see that tire is shorter (it is under inflated), however it's rolling diameter calcs out at 25.3 in. Am I missing something?

Damn Bubba, your in my backyard. PM me your address. I'll send you mine. I'd love to "visit" your project while I await my engine seal kit. Kent

PM sent

Thats a preference thing for sure.


I run 18's rear and think it looks great. I personally prefer 17's in the front though as to have a little better ride quality.

And here is the front suspension. I'll be power washing it Saturday morning and then mocking it up on the 914.

Here is the mock up of the rear suspension along with some measurements and an Autocad drawing of the rear end.

Looks sweet! Lots of work, but that kind of work is Fun work!

Challenging exhaust.....

Yep isn't that the truth. Fun Work!!

It used to be challenging. Not with this though. Check out this exhaust modeling system. It's like a Lego snap together plastic header pieces that are indexed and then can be cut to the sizes that are needed. https://www.youtube.com/watch?v=R1THlAZ2BqI

Have you priced that setup yet?

Too $$$ for me!

Would be nice if you could rent it.

Little teaser as to what the frame will look like.

Yeah I know. I'll buy it and then rent it out to the group. But yeah it is pricey.

That floor looks a little weak, No X brace in the floor or a horizontal where the pedals are?

That rear looks beefy as heck! I think you should remove the rear floor all together. Gonna be hard to raise the engine/trans in.

Don't forget that the floor diaphragm is there to take the shears. The cross bracing is at the transmission - rear suspension area. I will be providing tube clamps to be able to remove the struts when needed. Good eye though.

I went to Rudy's Saturday to check out his project and to meet a local fellow teener. He has a nice 2 year project and 5 son's for helpers. That's a good start. Here is a pic of the "suspension" donor car.

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And here is what burned it down. The Stereo or should I say Stereo installer. This is why you don't let the idiots at oil change centers/stereo shops touch your car. Check out the grommets. Oh, wait a minute. There aren't any.

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I took a crappy pic here but this is the stereo's main ground block. I has 4 places for bolts to attach to the body. Can you see that is it is held on by one sheet rock screw that isn't even fully pulled down. So in essence, no friggin ground. And judging from that #4 positive cable I'm guessing it was north of 200w.

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Rudy's '74 in a shell state

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Rudy cleaning the new suspension

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Is he related to Z.....flip flops!

hahaha

Great project for sure!

Did you check the SCCA rules with regard to how high the roll bar has to be over a helmet? I was surprised how high the roll bar has to be....

The Solo roll bar standards are here:

http://cdn.growassets.net/user_files/scca/....pdf?1458925428

The top of that rollbar must be 2" above the drivers helmet, UNLESS that height would interfere with the operation or fit of the OEM top. In that case the driver's helmet must be below a straightedge bridging between the top of the windshield header and the top of the rollbar over the driver's head(the "broomstick test").

So keep your top on

For SCCA, doesn't the main hoop have to have a cross bar, and all of it in a single plane? I.e. no fore/aft bends.

Would you happen to have the Roll Cage Standards?

hahahaha So Cal boy for sure. You gotta have the board shorts and flip flops. But that day ended up being in triple digits so it was perfect.

I put a link in my post and here it is again:

http://cdn.growassets.net/user_files/scca/....pdf?1458925428

And I believe all the SCCA rules are listed here:

http://cdn.growassets.net/user_files/scca/....pdf?1445897037

Well I started to analyze the frame and found that the front windshield bar (the one in red) will need to be upsized. I wasn't expecting that. Also, I wasn't expecting to stiffen the longs (n14 to n13) but after today's, result, looks like it's a must to stiffen the longs even with a roll cage. Click to view attachment

Sweet! You don't see too many people doing FEA iterations on chassis.

What software package is that? Almost looks like Ansys APDL or maybe more like Grape? You're modeling with beam elements or trusses? Can you glue a shell element floor on to better match reality? In one of the racecars I worked on laminating a thin carbon shear panel on the floors increased stiffness by 25-30% (experimentally verified via twist test too).

I think you're seeing artificially high loads in N43A because of the huge open box in the cockpit. If you add triangulation near the doors and closer the floor I bet you'll move some of that load path (if my visual FEA makes any sense haha).

Your loading seems a little weird. Why load the lower arms so highly in the vertical direction? They shouldn't see all that much vertical force since it's really all desisted by the spring/damper unit. Why not model the suspension in as an infinitely stiff member and then load with bump, lateral, and longitudinal forces? Then you wouldn't have to draw a free body diagram to figure out point loads.

With actual loading N36B might be more heavily loaded than you think (and in some combined weird bending/buckling mode so it probably needs a big safety factor). If you're doing frame stiffness twisting it (via moment about the front suspension nodes with the back fixed) seems more widely accepted than loading one side. There is a good SAE paper on it, I might be able to find it somewhere.

Sorry if you know all that stuff already. I'm not a mechanics guy by any means but I've spent a bunch of time doing chassis design/analysis for some tube frame racecars and a Lotus.

Now that's what I'm talking about! Love this kind of input. Now to answer some of your questions. The lower A arms were not loaded, what you are seeing is the 3 points where the suspension cradle is bolted to the chassis. The 900 lb vertical load represents a 5g load on the wheel. The next step will be to simultaneously load a 900 lb load in a downward fashion on the opposing suspension cradle support points to create a couple, or rather twisting of the frame as you mentioned. I will be running the same scenario at the rear and then run another scenario to simulate bending forces in the frame. I will go ahead and model the floor and both firewalls with plate elements and see what happens. Might as well model the "longs" as well. this will give a better representation of the behavior.

I'm modeling with beam elements with fixed joints in all directions being that the joints will be notched and welded.

I would love to get my hands on that SAE paper. I'm sure that I will learn a couple of things.

Are you going to model the suspension?

If so check out GrabCAD, I got the CV joints and center section from there (I modeled the rest)

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Hey thanks I'll remember that when I need it. Right now, I'm getting a feel fro the way the frame will behave. The next item on the list is to build the frame table and to mount the 996 to get all of the suspension pick up points tabulated. Then mount the 914 to start building the chassis with the same suspension pick up points built in. I'll be using a plumb bop and a laser meter to measure and square every thing. It's finally coming together.

Hoping it is built with I beams and 1/2" plate, so you can weld to it. In reality the I beams are fine, you should make the plate float on individual sections. So you can level the plate separate of the frame.

So it looks kinda like this on a much larger scale.

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Not mine but highly admired from the Garage Journal Forum.

I am making it out of 4x4 tubing. The tubing has much tighter mill tolerances than hot rolled I-beams. Also square tubing is much better than an I-beam in torsion. To make it out of an I-beam I would have to have it blanchard ground. I'm going with 4x4x3/16 frame with six 4x4x3/16 legs. All cross braced with 4 casters and 6 leveling screws. I'll tack weld on the ground enough so that I can raise and assemble. Then I will level all six legs with my survey equipment. Once leveled I will continue welding all seams a little at a time and from opposing corners so that the table does not warp. Then I will finish in that same Hunter Green as the rotisserie. That small chassis table looks like it's awesome for small projects though.

Pic of what it may look like.

I get worried that people will take offense to comments like those sometimes.

Gotcha, I just looked at your pictures again; didn't realize the 996 stuff was all on a subframe. Now it all makes sense.

Looking at that model again it might get stiffer if you switch from the bent front windshield frame halo-style bar rearward facing bars like found in a non-halo cage. Then you'd spread the longitudinal bars (N44 and N43 maybe) out towards the edges moving them further from your head and building a better node at the windshield corners. I just get scared seeing cross-bracing put hoops in bending. It might also be worth switching around some of the triangulation (ie: in front of and behind the door) to meeting at the same places to form some "super nodes." I noticed on the full tube chassis that this seemed to help stiffness without any weight penalty. The x-bracing on top and bottom of the rear might make maintenance very difficult. I did this over a chain drive differential in the name of stiffness and really hated myself for it after the fact. You could probably get most of the stiffness with a bolted shear panel. Hopefully that makes some sense; I can draw it tomorrow really quickly too.

The 5g load is pretty conservative; I've always designed around 3g bump, 2g lateral, and 2g longitudinal loading (though not all at the same time since tire friction circles limit the combined grip) and haven't had many problems. Your analysis plan sounds good to me! Unfortunately I'm at a conference right now and having trouble remoting into my regular computer to look but I'll check for the paper as soon as I get home.

Totally unrelated to the design stuff, but when you notch everything be sure to drill small holes in all of the receiving tubes at the joints. Being able to back purge while welding makes the whole process much better. You have less problems with oils, etc. running out and end up with much higher quality welds.

Thank You JD. I appreciate your excellent input.

2g Lateral Load at rear yields a 1/16" lateral deflection Click to view attachment
3g Couple at rear yields a 0.114 vertical deflection Click to view attachment
3g Couple at front yields a 0.10" vertical deflection Click to view attachment
2g Lateral in front yields a WHOPPING 0.70" lateral defelction. This is the worst case. It makes sense too in that the hole where the engine is allows this deflection. I'll have to fix that somehow. I have to wait until the motor is in to add a removable cross brace or just live with it. We will see.Click to view attachment

I'm feeling pretty good about this chassis .

Nice! Those numbers look great!

If you have time it might be interesting to run a case with a bunch of tubes connecting the rough engine mount locations into one node. At least it'd give you some idea of how much deflection the engine stops (assuming it's not super softly mounted). I bet with an "engine" surrogate in there you'd get a lot of the 0.70" back without making any other changes. Adding a bolt-on stressed panel under the engine (could double as a belly pan for aero) would bring back a bunch of stiffness too.

Two pure curiosity questions...How much does it weigh? What software are you using for FEA?

That did it. Since the lower frame is flush with the bottom pan of the car. I can bolt on a plate along the bottom and it totally fixed the flex. The flex now is 0.1" as opposed to 0.7"! I like the way you think. The bottom plate will also blend into a rear diffuser. I am planning on exiting my exhaust above the rear bumper line.

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With regard to weight it will add about 150 lbs. However, the front and rear hood, and the front and rear bumpers will be fiberglass. I'm going with about 600 HP so the extra weight will not be a distraction.

Fantastic! Easy fix! My guess is that you will retain nearly all of the added rigidity even if you have to cut some holes in it for access to things like oil filters, etc.

The weight doesn't seem bad at all, especially considering that you are cutting out existing structure and using some glass parts.

Is this design using different diameter/wall thickness tubing?

It uses thick tubing for the main hoops and thinner everywhere I can.

Well the material came in for the the chassis table.
These are the 2x2's that I will use for the webs
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These are the 4x4's that I will use for the table platform and legs Click to view attachment
Here are the casters
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I also picked up some samples of Fine, Medium and Coarse recycled glass for the wet sandblasting. I'll try each to see which works better. Planning on blasting the suspension clean as well. I'll probably be using the fine for the aluminum blasting. I know guys use glass beads for aluminum but that is for delicate surfaces. The suspension is hardly a delicate surface so we will see how it pans out.Click to view attachment Click to view attachment

Hey Rudy, I almost stopped by today but then I thought I should first ask if your around during the day. I might still be cleaning my engine Saturday. If I do finish cleaning it by then I'll start bolting the engine back together. I'll let you know when that begins.
That's a lot of metal there. But then again your connected in the welding biz, right?

No more connections. We used to be in the industry 30 years ago. Now the only connection you need is the green kind. Damn steel is crazy expensive. The material was around $1,200 I'm usually in the office, so if you're by the area come on by.

Cool! Figured you must be given the weight. I love 0.035 wall tubing!



Ouch. Can't wait to see the cart put together!

Sorry, I'm a little late to the party

Looks like a NASCAR chassis, which would be a good reference.

Hard to see numbers with my eyes, but you will need bars at n14-n15 and in the front n13-n06 and n12-n07, or your first t-bone will be your last anything.