924Board.org

[ideola]

Well, I've been slowly but surely plodding my way through prep work on the chassis. I'll come back later and put up a chronological post of where it started and how it got to this point, but for tonight, I'm pretty excited about a custom piece of fabrication that I just picked up on Friday.

During it's two year stay in captivity in Mr. Johnston's storage unit, the chassis unfortunately underwent a bit of abuse, in addition to having bits and pieces pilfered. One of the pieces that was damaged was the lower mounting setup for the radiator, so I have to come up with a new way to mount the rad. Also, I needed to come up with a way to mount the 951 FMIC as well as the Lindsey Racing Stage V header panel I picked up a few months ago.

I started noodling with some ideas, asked for some input from a couple of my car buddies, and came up with a design that I turned over to Chris Marsh of 4M Industries. He took my cardboard model and perfected it by producing this piece (3" square tube stock):

Closeup:


Bottom view (note the cutout):


Side view:


Top view:


In-car view, from right side a-pillar:


In-car view, from front:

Ultimately, the plan will be to weld this upper cross-member in place. The welds will go all the way around both sides, attaching to the main frame rails that come forward, and adding a fair amount of structural rigidity. I'm still debating about what to do with the original front cross piece. At first, I was considering removing it all together, but now I am contemplating leaving it in place, but drilling it with a hole saw to match the new piece, and allow for air to flow through to the rad.

The FMIC will mount directly on top of the cross-member, and the radiator will mount either in front or behind, depending on a number of other variables I have yet to sort out. The underside of the cross member has a large slot cut out of it that will allow for access from the underside in order to bolt brackets to the cross member.

The dimensions I provided to Chris were pretty much dead-nuts on the money, so I was pretty pleased with how the card board model worked as a template. The piece fits very snugly in place, and can be driven forward with a mallet to get it into the precise position. The other cool thing about the design is that the angled tabs on top could potentially be ground down or otherwise trimmed back if I decide I need to move the piece even further forward, without requiring any other changes to the rest of the piece. If anyone is interested in the geometry, let me know, and I'll try to post a rudimentary drawing with dimensions later this week.
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erstwhile owner of just about every 924 variant ever made

[CrashTest]

Wow that's awesome!
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'80 931 primer, brown interior, five lug In pieces now and parting out.

[Raceboy]

Could you post the dimensions of this new crossmember?
I'm planning exactly the same thing as I need to remove the original crossmember in order to mount intercooler I bought from you.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[ideola]

Will do, I'll get them posted later tonight.
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erstwhile owner of just about every 924 variant ever made

[ideola]

OK, here are dimensions:

The metal stock is 3" square tube.

Top view:

From the top view, the longest dimension along the back side (facing the windshield) is 29 inches. The front side (facing the front of the car) is 28", so basically 1/2" shorter on each side, with the "ears" angled toward the front of the car.

Side view:

From the side view (front and rear dimensions are the same), the longest dimension along the top of the piece is 26". This means that on the front side, the "ears" on either side are 1" wide on each side, while on the back side, the "ears" are 1.5" wide (due to the dimensions described above). The shorter dimension along the bottom of the piece is 24.5" long, so 3/4" of an inch shorter at the bottom than at the top. To create the correct profile on the front and rear of the piece, the 24.5" width extends straight up for 1.5", then angles outwardly up to the top of the piece to the aforementioned width of 26".

This shape fits very snugly between the frame rails once the original 931 sheet metal vent material is removed. Also, it's worth noting that the profile is the same from that point forward, meaning that the cross member can be slid forward or backward along the framerails so you can position it ideally for your application. If you need it to go even further forward, there is sufficient material on the ears that could be trimmed off to allow the piece to slide even further forward.

The rest of it is optional, up to your taste. On my piece, there are nine circular holes cut out of the sides to lighten the overall weight and to provide airflow into the engine compartment (I am experimenting with some ideas with plastic tubing to actually induce air through those holes into the engine compartment). The holes are roughly 1.5" in diameter, and spaced roughly 1" apart. The opening on the bottom of the piece is strictly optional. Again, in my case it serves dual purpose: one, to lighten the overall weight, and two, to provide access to the "interior" of the piece for bolting various brackets later on.

Hopefully, this is clear. If not, let me know.
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erstwhile owner of just about every 924 variant ever made

[Raceboy]

Thank you Dan very much!!! That saves me bunch of time.

I'll go for circular holes as well as opening in the bottom too. I'll post pics when I'm done with it, hopefully in a week or so.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[ideola]

Just a suggestion, it's pretty easy to mock this up in cardboard first. Not sure how you're intending to fabricate yours, but the piece Chris made came out pretty much identical to my mock up.
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erstwhile owner of just about every 924 variant ever made

[ideola]

Achieved a major milestone last night! The last of the destruction is over! I'm about ready to turn the corner and start PUTTING STUFF BACK TOGETHER instead of taking it all apart

Over the weekend, I finally got around to removing the trans, torque tube, and gas tank. Progress last night was primarily in cutting out the rear deck panel and tire well. This entire area has been opened up to allow for a fuel cell cage and additional supports to be welded between the frame rails. This will also make the task of installing my axle-driven alternator much easier.

You will see in some of the pix below that I left about 4" of the original deck in place, directly behind the rear seats. This was done to preserve the mounting locations of the fuel lines and brake lines that run across there. Ultimately, the deck will be recovered with a sheet metal panel, probably aluminum, and my current thinking is to have it removable with dzus fittings.

Next on the list for the chassis: I'm going to attempt to clean it all up now with kleanz-easy solvent and scotch brite pads to remove the adhesive and other miscellaneous crap on the interior. I am still mulling over the idea of having the whole thing media-blasted, but not sure I want to spend the $700 or so on this chassis.










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erstwhile owner of just about every 924 variant ever made

[tuurbo]

That's an amazing amount of work accomplished Dan. Are you doing this by yourself?

[bass gt]

Dan,

Great work!! Having seen these pics, you've given me some really interesting ideas for my chassis build. Things like mounting the dry sump oil tank in the rear against the side rail, and running all the oil pipes through the trans tunnel, by the torque tube. I could then mount the oil cooler adjacent to the tank, as there is so much room there.
The fuel tank would sit on the other side, against the rail, whilstthe rear section of the cage would be removable to allow easy access to the tanks and gearbox/driveshafts. I have even thought about putting the radiator in the back there, but that might be a little too adventurous!!
Out of interest, whats the measurement from the top of the rear rail to the botttom of the inner arch, specifically the section you can see below the rail to the rear of the wheel arch from the inside?
Oh, and your box went today Drop me a line when it arives.


Steve
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Front Wheel Drive is the Devil's work.

[ideola]

tuurbo, yep, I'm doing all the work myself so far, although I'll be bringing in a welder to do the fuel cell cage and the rollbar-cage work in the cockpit.

Steve, I'll take measurements when I get home this afternoon.
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erstwhile owner of just about every 924 variant ever made

[bass gt]

Dan,

If you are goingto do some measurements, could i ask for the following.
a) Width between inner edge of rear chassis rails
b) distance from gearbox beam rear edge to rear box section, behind spare wheel well
c) height and width of torque tube tunnel
d) Diameter of torque tube
e) Distance frm top of rear chassis rail to bottom of inner arch.

Many thanks Dan. Having seen your pics, i am seriously considering mounting my entire fluid system, rad, oil tank, fuel tank, oil/water exchanger into the rear. The rad would be central, with the fuel & oil tanks either side. Water?fuel?oil pipes run down the torque tube tunnel. The rad would be boxed in from above, with the box venting through the rear number plate area between the rear lights. fans on top would draw air through the rad, pressurise the box and expel it through the rear. At speed, the low pressue to the back of the car should suck the air out.
This would allow the entire front to become an intercooler!!
Thoughts?

Steve
_________________
Front Wheel Drive is the Devil's work.

[ideola]

Steve
Sure, I'll grab those measurements, no problem, now's the time to do it!

As for your plans, here are the things that pop into my head just based on my recollections from crawling around under the car this past weekend:

• Torque tube tunnel: it's fairly tight side-to-side, and I'd be concerned about the plumbing hanging up on the shifter linkage if you routed it above. If you go below, then you have to worry about the exhaust, and you might need to add some additional shielding. I have another chassis with the torque tube still intact, so I might be able to do some comparisons, but won't be able to get all that done tonight. But here's a variation on a theme for you: how about a smaller diameter aluminum torque tube (Bwahahahahaha!)?
  
• What about exhaust?: My concern with putting fuel tank on one side and the other fluids on the other side is where to route the exhaust. I am currently planning to install a Fuel Safe cell behind the trans, directly behind the RHS of the car (what would be driver side for you). This leaves the LHS vacant to accommodate a stock-located exhaust. Directly in front of the fuel cell will be the snailshell in the center, and to the right of that (if you're facing forward) will be the axle-driven alt. I think there will still be plenty of room to put a dry sump oil reservoir there, as this is how it appears to be configured on Frank's D-Prod. I don't know that you can put much of anything on the LHS due to the exhaust routing. Unless you have something else in mind. Coolant reservoir could go just about anywhere.
  
• Rear-Mounted Radiator: As for the radiator configuration, it sounds like an awesome idea, more weight in the back, it's just an issue of whether you can make room with the exhaust and accommodate the fluids and plumbing as noted above. Of course, it adds some really long coolant runs...what type of plumbing are you thinking of? Wondering if some PVC hard line would make sense if there was room through the torque tube tunnel. Otherwise, you could drill holes with a hole saw in the front and rear firewalls and route the hard lines right thru the cabin, have them clamped down to the torque tube tunnel but on the inside of the cabin.
  
• Fuel Cell: A lot will also depend on the size of your fuel cell. In my case, I'm currently planning to go with a 16 gallon unit, which is 26"Wx17"Lx9"H. Bear in mind, you will have less room behind your trans if you're going with anything other than a snailshell due to the diff configuration on the Audi and 968 boxes. Also, in order for my planned fuel cell to fit, there is a lip that curves back in toward the front of the car on the underside of the spare tire well that I removed. This lip is about 5"-6" deep. There's nothing structural to it, it's just sheet metal, but this will open up a lot more room than what first appears to be there when looking from underneath.

Here's the pic of Frank's D-Prod from which I am drawing a lot of my design decisions. I don't know the exact dimensions on his cell or how it compares to the one I'm planning to purchase...in my case, the choice is partly based on full alcohol compatibility. But you can see how the fuel cell is very close to the end of the snailshell gearbox. You can also see the dry sump oil tank in the upper left, and the trans cooler tank directly over the trans. One of the other noteworthy things is that it appears to me that the entire rear seat wells have been removed, which opens up more vertical and front-to-rear space in the hatch area:


You can also see in this photo that his exhaust is routed out beneath the RHS door:

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erstwhile owner of just about every 924 variant ever made

[bass gt]

Dan,

Many thanks!! Ok, heres some background info. My exhaust exits under my passenger/your drivers door. So there is no conflict with a fuel/oil tank and the rear box.
I have a sneaky feeling that two runs of 32mm alu tube could be fixed into the torque tube tunnel, at the top LH corner, as you look from the front of the car. This would allow the pipes to come around the side of the engine under my raised up exhaust manifold, and into the front of the engine. Conversely, i would look to fit the oil & fuel lines up into the other top corner of the TT Tunnel, thus keeping the cockpit area intact.
As i have the 968 box going in, i need to cut out the stock gearbox cross beam, and mount a new beam higher up, level with the top of the rail. I could then have two smaller sections running to the rear from this beam onto which the rad would hang. The oil & fuel tanks would be either side. Regarding the fuel tank, as my car is a sprint car, i need no more than 20 litres capacity, so that makes life easier!!
And whats this about a smaller TT??? And yes, if you could get the clearance dimensions between the TT and the tunnel, at the top, top corners and sides of the TT, that would be fantastic!!

Steve

Steve
_________________
Front Wheel Drive is the Devil's work.

[ideola]