The Next Generation. 3G T.A. [Archive]

RobNoLimit

06-29-2018, 06:06 AM

We are sharing this hoping to expand the idea of what a Pro-Touring car may be. Or, a certain type of PT car. Like, a Super PT. For this, it is time to go outside the box. Way outside. We are pretty far along in the project now, but let me go back and start from the start.

About two years ago Keith Corrigan and I (Rob MacGregor) started having a discussion about a new car build. Not so much about the car itself, but the concepts, directions, and rules for a new build. We studied the past builds of ours, most currently the HellBoy C10 and his Velocity Camaro. Both are solid competitors and great drivers, and, both have reached there performance limits (without major reconstruction). We talked about the current crop of fast cars, The Leisinger 'vettes, the RideTech 48hr vette, Dusold's Camaro, and such. What we liked, and what we didn't. Some discussions focused on events and their rules. So we have gathered up some rule books. SCCA, SCTA/Bonneville, Silver State, PPIHC, USCA an more. We may not go to any of these, but, a well built car should be capable of attending. If we can fit in here, then others like the Texas Mile, Ohio Mile, Sand Hills, and other Hill Climbs are also a fit. A car capable of the Power Tour, The One Lap, Cars and cones, a cruise to the local BBQ joint. A Supercar with stamina.

This thread will look different, and I hope to include sources and part numbers along the way. We have also summarized many discussions and topics, these will be posted like pictures, from the saved documents. AT the end, we will disclose the final hour count and total cost to get the car out to it's first event. We both feel strongly that the "Why" you do something is maybe more important that the "How", so, those discussions will be included.

The car itself, an '85 FireBird. We'll cover the "Why" of that later. How far will we go? FAR. BTW, if you are not a subscriber to "Race Car Engineering" (magazine) or "Hi Performance Academy" (facebook) you want to consider doing so, it will help you keep up.

cornfedbill

06-29-2018, 07:20 AM

Rob,

I know why these 3G F-bodies are not popular, but have considered building one myself for events such as Sandhills and Big Bend, along with standing mile events such as the Big Blue mile. The aerodynamics are excellent. The cars also have a good shape and proportions for high speed driving.

What they lack in character, they make up for in potential.

I just never liked the strut suspension in front. The rear is not bad. With a new front stub and some work to the rear, both of which are available in your product offerings, I expect this car could reach a new level of pro-touring performance.

I am excited to see how this turns out.

RobNoLimit

06-30-2018, 07:00 AM

Thanks Bill. To be Honest, I kind of think of these as the "Disco Camaro". But, I am coming around.

The choice of 3rd gen Firebird was mostly Keith's. - Hopefully I can get him to chime in on this. But, there are some compelling factors.

WheelBase 101"
Width 72.4"
Weight 2868 lbs (4 cyl - 5 speed - hard top)
Drag CF. .29

BTW, these cars still hold the record for the lowest CF drag of any US production car. Not much down force, but pretty slippery. I would hate to know the CF of the HellBoy. :(. And, the underside of these cars is pretty messy, so I think we can smooth it out and help with some down force. At a factory spec wt of 2868, there is a plus. Some classes have no weight specs, others have a set minimum, and some use the "10% less than OE" - That would be 2581 lbs. While we are going to be VERY weight conscious during this build, I don't really want to break the bank with Carbon Everything. I think we can be smart and sparing in this regard. The 101" WB is nice, good for short course stuff. C-5's are 104, and C-6's are 106.5 (or so). Compared to Velocity's 108, It's about 7% shorter. The width is not bad, we are going to try not to make it too 'Fat', tight courses penalize a 'wide stance' car (or truck). So, we went out looking for a 4 cyl hard top bird with a straight body. This is not as easy as you may think. But, we did find one. Just for kicks we weighed it, with a flat tire and some trash in it, 2893 lbs. Then we started gutting it.

The OG plan was to use C5 running gear, shorten the torque tube to match, and build a tube chassis to put it on. So, we bought a C5 roller and started measuring. Those are expensive notes, and, we now have a lot of spare C5 parts. In the end, this picture tells a lot. One is a factory C5 front lower arm. It's really close to what we wanted. But, the coil-over mount and sway bar mount were not quite where we wanted them, and, with the wheel specs we're looking at, the wheel hit the arm at 27 degrees of steering. Not enough. Also, the aftermarket "kit" parts to put Del-a-Lum or bearings in the lower arm are pricey (corvette guys $$) So, we built some arms. These use the factory C5 lower ball joint, and teflon lined spherical bearings. The fit in the OE adjustable mounts, clear 36 degrees of steering angle, and weigh less than the OE (chromoly)All in all, they cost about the same as buying a bearing kit for a C5. Now we have spare lower arms. It's gonna be like this a lot.

USAZR1

06-30-2018, 03:17 PM

This should be an interesting build. Looking forward to it, Rob.

RobNoLimit

07-03-2018, 05:37 AM

As part of the original plan, we had decided to build a full tube chassis. The main considerations for this are strength, safety, and weight. Most would think this is going "too far" or pushing the cost "too high", but I hold a different opinion.

If you start with a 30+ year old platform, the basic build plan today is to repair or replace the floors, add subframe connectors, install widened wheel tubbs, modify the trans tunnel, and maybe the foot well, pedal mounts and seat mounts, then the firewall, and add a cage. Maybe even raise the rear hump and modify the trunk floor for fuel tank and axle travel. So, there isn't much of the OE platform left stock, and, all of this was heavy and expensive. So, if you commit from day 1 to go for it, in the long run, this is the most cost effective approach. (we think anyway).

So, the F-Bird was gutted, all of it. And then carefully placed on a build cart/table. One of our first spec commitments was a 4" minimum scrub line. So, the body was set so that the bottom of the OE rocker was at 4". From this point, our base chassis layout began to take shape. There are really three sections of the design. Front: IFS, engine, cooling, steering concerns, body mounting.... Cabin: Driver safety cage, controls, electronics, seating, driveline tunnel, .... and the Rear: IRS, Fuel, exhaust... But, the three have to fit together, and fit into the body shell. To assist in setting the front rail sections and suspension mounts, we cut aluminum templates (CNC waterjet) to help hold the upper tubes, using the pre set lower tubes as a base. These template plates also helped to locate the Upper and Lower control arms. UCA, LCA. Suspension design was previously worked out using a mix of Solidworks, Autoware and Suspension Analyzer. This allowed us to model the complete chassis and suspension assembly, apply forces, check for high load areas, and hopefully (though no always) eliminate extra work. I say not always because the physical components are not always what you thought they were, like the LCA's that were replaced. But, that's hot rodding, so we just move along. See you in Columbus. Happy Treasonous Colonial Day.

cornfedbill

07-03-2018, 06:32 AM

I agree that these are not the most attractive or desirable F-bodies. But as you pointed out, nothing beats the aerodynamic drag of the 3rd gen F-bodies. And they are light. When it is fast enough, nobody will care what it looks like.

Is that a Winters quick change rear I see in the photo? I've been considering one for my next build - a C3 IMSA clone. But that is time and $$$ into the future right now.

The simplicity, strength and versatility of the Winters quick change makes it a good choice in my mind.

RobNoLimit

07-12-2018, 09:28 AM

When we started, we tried to lay down some ground rules. It turned out harder than we thought. If you compare this build strategy to the "normal Pro Touring" build, it won't even be close.
When we attempted to sum up the current build standard, it looked like this:
** Start with a car body that you like, or already have. Buy the current 'Hot ticket' Suspension, Brakes and Rear axle. Add in some mini-tubs and subframe connectors, and maybe a cage for safety. Drop in an LS and a 6 speed, and don't forget the Super trick wheels. Now, some guys go farther, and add some Carbon Fiber parts, and Oh yes, the billit aluminum. Next comes paint and body, and some electronics to make it all work. I know there is more than that to it, but 90% of the builds on here could be put into this category. (maybe a different motor/trans).

So, here's a little history. In the early days of GoodGuys Auto-X, there was no "Truck Class". After some discussion (and two years of pushing) Ed came around and decided this might help get some more guys out there. So he asked me, "If we create a Truck class, will you come and run in it?" Sure I will! So, I built the Silver Bullet F100 and went to the shows. So, for about three years, if I showed up to an event, I won. There were some good competitors after a while, but I was getting faster as well. So, I won. AND, people were complaining. GoodGuys actually published a letter in the Gazette from a guy complaining that he may as well NOT show up because he had no chance of winning the Truck Class. So, the fun was over. At the end of that season, I got the word. New rules. "If you win you're class, you will move into the Pro Class". I was only somewhat surprised, but now it was the "Pro Class" no longer the "Vendor Class". I only had one question for Ed, "So, that means I have to race Kyle Tucker?" "Yes". Well, that changes things. I can win in the Truck Class, but I can't win in this new Pro class. I need a better truck. So, that winter I built the HellBoy. You can't be bringing a knife to a gun fight. And you guys know the rest. Kyle was the top dog, and with the HellBoy, I was able to race with him, and we are still pretty even in the win/loss column. Some may think I should be unhappy with GoodGuys and Ed for the rule change, but NO. Without the rule change, I may have never built the HellBoy, which has spurred on other builds like Jason Brady's Blazer. So it turns out that change is good, and that as Racers, we all want to push forward and go faster.

Why is that important? Well, if I had built another version of the Bullet, it would not have been to competitive in the pro class. I HAD TO GO FARTHER. And it's that time again. We cannot follow the current standard and expect to be any faster. It's time for new rules.

rixtrix1

07-12-2018, 12:55 PM

Looking forward to this; something along the lines of a Ron Schwarz build, but more(if there is such a thing) and streetable, too. I assume you're looking at less than 6 figures, too?

RobNoLimit

07-13-2018, 11:00 AM

Looking forward to this; something along the lines of a Ron Schwarz build, but more(if there is such a thing) and streetable, too. I assume you're looking at less than 6 figures, too?

Yes, we do have a budget plan, but I am not so bold as to let it our just yet (in case we are way off) We have a base "this is the goal" number, and a 10% over-run factor. I will give out the full build parts list and hour count in the end.

cornfedbill

07-13-2018, 01:35 PM

I like the approach. I am eager to see how this turns out.

Reading the rules is important. I ran Sandhills last year and will be back again. Only this year we will be running fast enough to require a roll bar. They specify 1-3/4" 0.95" wall DOM. Then I looked at the rules for Big Bend. They require 1-3/4 0120" wall DOM. I'm glad I didn't build the cage for my Nova yet. I would have to cut it our and rebuild it.

It does make it difficult when looking at rules across governing bodies. However, they are all within a reasonable band. One can build a car that will work for almost all of these Pro-Touring/Autocross/Open Road/Shootout/Hillclimb events. It just takes a lot of due diligence.

I'm very exited to see how you break out of the box we have fallen into.

Yukon Cornelius

07-15-2018, 05:57 AM

Subscribing.

Streetbu

07-15-2018, 03:01 PM

Interesting build. Sub'd and looking forward to updates.

RobNoLimit

07-16-2018, 06:28 AM

Thanks guys. OK, one more general discussion before we really get into it.

Adjustable * Adjust * Adjustability.

Now, give it some thought. How many of us (you) have cars with adjustable things on them. Carb jets, distributor timing, valve lash (old news) Fuel and spark tables? OK, how about suspension links, caster, camber, toe, spring load, shock valving, spring rate, sway bar rate, roll steer, instant center, roll center...........

Most well built street/track cars have all of this and more, in one way or another. Now, in reality, when was the last time you were at an event and actually adjusted something other than tire pressure? Be honest. How crazy is that. We have all of this adjustment available, and, we don't use it. I will risk it and say there are only two reasons for this. 1) Not sure what to do. and 2) Don't have the time to do it between rounds. Now I will argue that reason #1 is somewhat a byproduct of #2. Look, if you don't have time to make a change, you don't. And so, you don't experience what that change might have done, and so you don't gain the experience. You have to be willing to try things to learn, but if the time doesn't permit it, the odds are against you. And so, we come to the one factor in adjustability that would make all of the difference, TIME How long does it take to make a change.

So "Time to Adjust" must also be a design factor. Looking at a GoodGuys, AX-Guys or USCA event, about 1 hour between rounds is the max. But be reasonable. You have to park and get out of the car, you may discuss the change to be made, look at some notes, and you need time to get back in the car, calm down, and get in the line-up. And, SCCA is a faster loop. So, we set out sights on 15 minutes In this short window, we would like to be able to make a change, be sure the car is set up correctly, make notes, and wrap it up. As part of the car build in total, components must be placed and mounted in such a way as to allow this to be done. And to do this, the placement, mount style, hardware, and component choice all come into play.

Our list of Adjustments includes: Front alignment (caster, camber, toe, roll center), Rear alignment (camber, toe, roll center, roll steer), shock valving, shock rubbers (if used) spring load, spring rate, sway bar rate (front & rear), Gear ratio, brake bias, ..... Just for kicks. We will add all of this into our decision blocks, and that will make for some compromises. But, if you're not really going to adjust it, it doesn't need to be adjustable. Keep that in mind.

SSLance

07-16-2018, 10:53 AM

^ So spot on and so crucial!!

Subscribed...

RobNoLimit

07-17-2018, 09:16 AM

Newton's First Law ".....an object in motion will stay in motion, until some other force acts upon it....." In math terms, that's all performance is. To win, you have follow Newton's laws. Put another way, a 3400 lb car going due south at 60mph, WANTS to keep going due south at 60mph. Rolling friction, driveline drag and air drag are the only things acting upon it to slow it down. Now, you want to turn 90 degrees and head due east, you need to work on Newtons laws. Because, the car DOESN'T want to do that. It wants to keep going straight.

F=ma another smart guy rule. Force = Mass x acceleration. Next I will translate and butcher. (as this is purely for the sake of discussion, I need no correction. I know this to be incorrect, BUT, it is understandable) How about if I said it this way. Energy = weight x speed ( I know, but I did say Butcher) SO, you get it that a car weighing 3400 lbs going 60 mph has a certain amount of energy keeping it heading in that direction lets say 3400 lbs x 60 mph = 204,000 energy units. Lets call these units "Hexo's" But lets also say that 1 Hexo = 1000 energy units, so we could say 204 Hexos. Just one more way to see it, 1 Hexo = 1000 lbs x 1 mph. OK.

So, why is this important? well, if your 3400 lb car is at 60 mph and you want to stop, you need to exert a total of 204 Hexos of braking force (and have the traction hold). If your car is heading due south at 60mph, and you want to turn it 180 and head due north at 60mph, it will take 408 Hexos (204 to stop it, and 204 to get it back to 60). So, any speed you can conserve during your U-turn will reduce the amount of Hexos (energy) needed to due the job. Now this may be oversimplified and somewhat inaccurate, but the concept of mass and energy is what we're talking about. And, it is this knowledge that helps us to understand the differences in weight location.

The first sketch is a top view of a given car. The center rectangle is defined by the centers of the contact patches on each tire. CG (center of gravity) is set in the center of the rectangle. Our first goal is to keep as much weight as we can (in total %) inside the rectangle. With the rule being, the closer to center the better. You may note that I marked "Front Swing" and "Rear Swing" as well. This is BAD. Any weight outside the rectangle acts like a pendulum, or the head of a hammer. It's leverage (distance) from the CG gives it more energy, Hexos, and is harder to control. Front Swing weight will want to keep going straight when the tires are turned, creating a push. Rear swing weight will initially follow the turn, but want to keep going, and drag the back of the car with it. Both of these are "Bad Weight" and will require more Hexos to be used to turn the car.

The second sketch is a side view of the same car platform. 100" WB, 26" dia tire. 4" scrub line. Note that no CG is marked. For most cars, the CG is somewhere close the camshaft height, but proper weight placement can help lower that. The perfect place for weight would be at ground level, directly on the tire's contact patch, but that's not gonna happen. SO, we have to work in the real world. The closer to the center the better, and the lower the better. An understanding of this will create 'arcs' from the contact patches to the CG. Each ring above is progressively worse. Note that at some point, weight high over the CG is seen as equally bad as low mounted Swing Weight, but this is not so. Any weight placement in "Side View" must also go through the "Top View" test. So, Swing weight in zone 5 could be considered twice as bad as the same weight in zone 5 right over the CG.

The key here is to understand that a pound here is not the same as a pound there. And, the more bad weight you carry, the more Hexos (energy) it takes to turn it. The only tool we have to "Push" the Hexos around is Traction. Bad weight uses more traction to control, and leaves less available to change direction. In this sense, a heavier car with a higher % of "Good Weight" may be a better performer than a light car with a high % of Bad Weight.

RobNoLimit

07-17-2018, 09:33 AM

Now, lets put some of this to work. When you consider weight, the engine/trans is one of the heaviest single components that you will mount in a car. SO, we had this discussion. Move it back, Yep, everybody gets that one. Move it down. Yep, Got that too. But HOW FAR can you go? Well, we can move it back until it's inside the rectangle, that,s not too hard. And, we can move it down until it hits our 4" scrub line (also known as belly pan, or frame rail bottom). With an LS and a steel bellhousing and stick trans, the lip of the bellhousing is about even with the oil pan. If this is the low point at 4", the crank CL will be about 12"

RobNoLimit

07-17-2018, 09:42 AM

So we started thinking, how can we lower this weight. Well, we know we are going to be running a dry sump oil system. And, we have the pan. It's a low profile pan from A&E. That will help with pan clearance. But, the Bell housing is still the barrier. Not too tought o solve. By using a more race style BellHousing/clutch/starter assembly, like a Late Model Dirt car, we can get that out of the way, and then drop the eng/trans down about 1 1/2" - 2". not too bad for off the shelf gear.

RobNoLimit

07-17-2018, 09:51 AM

But, that's not enough. I mean, we just did the easy stuff. Now the belly of the trans is at the low point, and the trans can't go any lower. The engine could, but not the trans. How about if we divorce them. We could move the trans back a few feet (more rear weight, closer to the center) AND, we could drop the engine another 2". How do you do it? you ask? Welll, we got a big chunk of aluminum and whittled out a bearing plate. It bolts to the bellhousing and carries an input bearing from a super T-10 (in a wet oil cavity) and also has bolt up provisions for a TH-400 tail shaft. All you need then is a custom shaft that fits a 26 spline LS to a TH400 slip yoke. All in all, it wasn't that hard or expensive. But we did go way outside the box.

cornfedbill

07-17-2018, 10:30 AM

Well done. I like the thought put into this build. I like the way you question everything.

Too often we get stuck in tradition and forget to question why some guy in 1953 decided to mate the transmission to a small block Chevy in a certain way. We carry his decisions forward into 2018 and beyond.

Streetbu

07-17-2018, 06:31 PM

Hmmm. So maybe a torque tube style setup with a C5/6 style rear mounted trans/diff assembly. Lower CG, redistributed weight. Me likey :)

cornfedbill

07-18-2018, 04:45 AM

RobNoLimit

07-20-2018, 09:07 AM

The C5/C6 does place the transmission in front of the rear wheels, unlike the Porsche/Audi transaxles that hang behind. It meets your design criteria. The torque tube does limit the torsional load on the frame so it does not need to be designed to support that load.

This was our plan. At first. We thought we had it all figured out, but, to make use of the C5/6 torque tube we would have to raise the engine some. Also, we could not offset the eng to the pass. side for weight balance.

RobNoLimit

07-20-2018, 09:20 AM

Our next idea was to use the C5/6 trans axle without the torque tube. It is easy enough. Machine a front mount that carries a support bearing and mount a yoke to the input shaft. Then, run a driveshaft from the engine back to the transaxle. But, that leaves gear changes out, and we really want to be able to do that. BTW, we went pretty far with this idea. I have the plate/bearing/yoke design all ready to go. I may do this on another project. We made a last minute call to go to PRI (which is way better than SEMA) to do some scouting. And we found, among other things, this awesome gear box - transaxle. It checked all of the boxes. front side gear box, 'low side' mounting, IRS CV bells, even sequential shifting! It's even fairly light @ 110 lbs. wet. We were so excited. Then, we heard the price. $37k US. Hmm, well, that's almost half of the total planned budget. It was like getting one kiss, from a smokin hot chick in Italy, and she hops on the train and heads back to Sweden. Only the heartache is left. Ahhh, it was an awesome gear box though. And, we kept on walkin.

cornfedbill

07-20-2018, 10:21 AM

This does not check all the boxes because the gears are behind the rear axle centerline. But it is was cool and has lots of potential and the ability to transfer lots of torque. And it's "only" $18,500.00. That's a lot of money and not likely within your overall budget. But not bad considering the alternatives.

While it is not what you are looking for because of the placement of the gears, I do think it would be great for some builds though.

https://www.ppgearbox.com/single-post/2016/02/03/Introducing-the-Quick-Change-6-speed-transaxle-conversion

RobNoLimit

07-23-2018, 05:37 AM

In the end, gear change (ability), availability (parts and repair parts), weight and cost won out over pure desire. We decided on a Speedway Engineering Quickchange IRS center section with a Platinum-Drive diff unit. This was built to accept Porsche style 934 CV joints with 33 spline axles. This checks off quite a few boxes for us. Serviceability and the option to do a gear change in less than 15 minutes came in as the overwhelming pros. Cons may be the mounting, as not much comes with it, but we do have a fab shop. In our initial set up, we mounted the diff so that the axle center height was at 11.5". This is 1.25" lower than the wheel/hub/CV center at 12.75. This was done in an effort to lower the overall CG of the car.

During the design phase, we set a driveline angle target of 3* max. In this configuration, we have four "drive shafts". 1) engine/clutch to trans 2) trans to diff 3) LH CV axle 4) RH CV axle. Our goal here is to have a max of 3* angle on any joint at it's spec ride height, and try to stay under 5* (CV axles) at full suspension travel. *** Less than 3* is for parasitic HP loss reduction, and the 5* limit is to reduce driveline NVH, or "busyness". Vibration can be reduced or eliminated by matching angles, but the 'busyness' or 'verb' from higher angles cannot. Once the rear suspension was in full mock-up, and we had actual CV's and axles, we decided to raise the diff to an 11.800" centerline to keep the axle/CV angles within range at full stroke of the suspension. All in all this was a big step forward. It cemented the driveline direction and allowed us to move forward into full fab.

RobNoLimit

07-27-2018, 09:43 AM

Wow, that last pict shows how empty the back of the car was!

The rear chassis design was again from 'function' first. In the design, we had to plan for Exhaust, Muffler/s, Fuel tank, Aero, and allow for shock tuning, spring swaps and sway bar adjustments. The lower chassis tubes have to mount the LCA, the lower Diff mounts, fit to the belly pan, and clear the exhaust. The upper tubes hold the UCA, upper diff mount, rockers, coil-over mounts, and are spaced to allow the fuel tank to sit in. You can spot the sway bar in a few picts, I'll get to more on that later.

At first, we planned on using the C5 lower arm (LCA) But, in the end, shock/spring and sway bar mounting locations were not correct, and, the arm geometry was a compromise. So, we built new LCA's. The adjustment on the lowers is for 'wheel base' squaring only. Once the car is set square, we won't be touching them. BTW, our new arms are 2 lbs lighter than the OE C5. The UCA was always planned to be fabbed. we wanted LH/RH adjustment for rear camber. Also, these arms are a little shorter than the C5 for quicker camber gain.

SSLance

07-27-2018, 09:56 AM

Ball joints and tie rod ends...on the rear knuckles... For rear toe adjustments I'm assuming?

RobNoLimit

07-30-2018, 05:17 AM

Ball joints and tie rod ends...on the rear knuckles... For rear toe adjustments I'm assuming?

Yes, this is OE C5/C6 'vette stuff, well the knuckle anyway. Careful lay out will allow us to tune the Roll-Steer of the car, as well as set a baseline Toe-In on the rear. The C5 uprights will end up with C7 UniBearing hubs (direct bolt in). The C7 hubs are stronger, and take a 33 spline stubshaft, stronger than the C5/C6 28 spline unit.

RobNoLimit

07-30-2018, 05:55 AM

The last picts were pretty clear. It was only the base IRS parts. One pict here is just of the LCA on it's Ride Height stand. The rod end adjustment on the LCA is only for "Wheelbase" alignment, not camber. We wanted the ability to make the car perfectly square. (actually a rectangle through the tire contact patch centers, but you get the idea) So, next came the rocker mounts and rockers. The rocker mounts use a set of needle bearing rollers. The rockers are currently 1-1 ratio, and although we thought about milling them in aluminum, modeling showed fabbed steel units to be lighter than aluminum (simple 3 axis milling).

andrewb70

08-04-2018, 06:38 PM

Awesome. In for undated.

Andrew

RobNoLimit

08-06-2018, 06:33 AM

NSRA Louisville was last weekend. If you are not going to this, and you like to get in some AX laps, you're missing out. You could easily get 20 runs per day, for three days. I had a few discussions with some people who's opinion and knowledge I value, and most of those discussions included "weight" as a topic. Total weight vs. unsprung wt vs. rotating wt. ...... And, then I had a 5 hour drive home with some alone time to think about it. AX and Road racing share some things, but short track (AX) is it's own beast. Rapid and radical acceleration and deceleration are keys, but also total direction change. For these actions, two factors rise to the top as 'most important' (IMHO). Traction, and Total Mass (weight). When you want to "change" vector force - (direction/speed), weight is a huge deal. Think of a Ping-Pong table (a really strong one), if a Ping-Pong ball is coming at you at 20 MPH, you can use the paddle and hit it back. - Change it's direction, it's Vector Force. If it was a golf ball, you could not change it's direction as well, and if it was a cannon ball at 20 MPH, I doubt you could change it's direction at all. Your car is the same thing. You want to charge down the lane at full throttle, stop at the last minute (change) and turn 90 degrees left (change) and then accelerate as fast as possible (change). Mass or weight, is making you're performance desires very very difficult. So, you may start to think that 'Lighter is better" no matter what, BUT, this may not be so. We need traction to apply the force (torque) to the ground. At some point, the car would be too light to allow the suspension to work efficiently.

I have thought for some time now (and still do) that the relationship is based on a percentage of unsprung vs. sprung weight (or total weight) Like the Ping-pong ball, if you want to hold the tire to the ground, you need a sufficient overwhelming force to do so. As we AX and Short-Track more and more, my own thoughts are that the minimum balance number is around 14 or 15%. BTW, it may shock some to realize that a Trophy truck weighs in at around 6500 lbs, just for this reason. So, I look backwards. If the total unsprung weight is 90 lbs per corner (wheel/tire/brakes/spindle + 1/2 of the LCA/UCA/spring/shock) and for example, lets say an IRS with the same rear figure, then the total unsprung is 360 lbs. If this is 14% of the total, then the lightest the car can be is 2571 lbs (360 divided by 14%) If the car gets ant lighter, the unsprung weight has to be trimmed as well. Now, if the car is heavier, it is easier to get the suspension to plant the tire, but harder to "change" direction.

Anyway, here are a few shots of the rear suspension. The guys at RideTech sent me a test shock to use, it has no fluid or gas charge, so I can open and close them easily. It may not look it, but the shock/rocker/pushrod assembly is "on plane" so that there is little or no side load on the components, and also, there is less than a 3% side shift on the pushrod through the entire stroke. At this point the travel is too much, and we will limit it with bump rubbers for tuning.

SSLance

08-06-2018, 07:14 AM

Rob, am I correct in assuming that when using a rocker arm setup like the above you are moving the weight of the shock\spring combo from unsprung to sprung weight? Or does that line always exist in the middle of the spring no matter what?

Streetbu

08-07-2018, 01:55 PM

That would be considered sprung weight from my understanding

JayinMI

08-08-2018, 04:36 AM

RobNoLimit

08-14-2018, 05:14 AM

I was thinking that it seemed like doing that would laos have the added benefit of moving weight toward the center of the car and away from the outside corners...then I realized that that would probably be considered unsprung weight. Am I correct in my assumption?

Jay

I think it's a mixed blessing. The shock/spring become sprung weight, but 1/2 the rocker and pushrod weight are unsprung. So, the unsprung weight is reduced, but the total weight is up a bit. Also, we did move the weight 'up' in this design (bad). In the game of compromises, the ability to tune in 15 min or less, and the reduction of unsprung weight won out over a gain in total weight and raising the net CG. ** This car will have a LOW CG, due to many of the other design elements. So, in comparison to other platforms, even though this decision raised the CG (appx .13" net says the E-box) we are still way down from a traditional build.

RobNoLimit

08-14-2018, 05:45 AM

Over the last week I have been thinking about another build going (not ours) and the test days they have had. I think a short timeline gave them fits. I'm sure they will get it sorted, and I'm sure it will be fast. But, I have my own feelings on the car in total. It's light, it's a wide big tire car, it's got lots of HP, and to me, it's old news. They didn't push the envelope. Nothing there that hasn't been done. So, awesome car, and a proven approach, but a little less excitement to me.

On the other hand, we are trying things. And, we may fail because of this. We are taking some risks this way. There are a dozen or more hings on this car that I have thought about, and never tried. So, it has a higher percentage of failure than a build on a known plan. Because of this, we cross our fingers a lot. Also, there's nobody to ask. No info to find. So we spend a lot of time researching and figuring. Here are some shots of this.

To divorce the trans, we chose a small bellhousing/clutch with a reverse mount starter, This also helped with clearance to lower the motor. On the "clutch" side, we have an input housing from a TKO (thanks to Mark Bowler). to support the "Clutch Shaft" (as we call it) we are using a wet roller bearing from a M22 4 speed, and to support the output and slip yoke, we have a TH400 tail housing. We started with a 1 1/2" thick chunk of aluminum and carved out the merge plate. It is complete with a seal set, oil reservoir, vent and drain. Too many hours to count for such an item, but having it all fit was a great payoff. We are having a custom shaft made to fit (two actually, so we have a backup). There is a pict of the front LCA mount tabs. I chose to duplicate the OE style adjustment of the LCAs (for CL squaring only) So first we needed a hole to center the mount, the later we knocked out the sides to make slots (this requires a little work with a file to get nice and smooth). Last is a pict I ran across while looking for these. The F100 is owned by Kai L. of "Street" Magazine in Germany. The 'effe sits on one of our "Big-10" chassis with a floater, 406W and 6 speed, and has been around the Ring and Hockenheim many times. It is always a shock to the other drivers how quick it is. Remember, this is supposed to be fun.

rustomatic

08-14-2018, 09:49 AM

jlcustomz

08-15-2018, 02:49 AM

Nice to see this level of work going into a 3rd gen. Had a friend that put 80k or so into one about 10 plus years ago as a combination of show & go. People at shows would say why on a 3rd gen, I'd say why not. But like with so many builds done 10 or so years ago in a sort of pro street/pro touring/custom style, the chassis & aftermarket suspension really couldn't handle & make proper use of all the heavy big block power, leaving it an underused showcar.

Don't look like you'll have that problem.....

RobNoLimit

08-15-2018, 05:02 AM

I just wanted to say thanks for continuing to show great ideas, engineering, and perhaps most importantly, depth. It is what this hobby (not a business for most of us) really needs, especially with the easy access we have to information and great tools these days. I think I know which "build" you alluded to early in your post, and I really hate the way that cluster went; the results were totally unnecessary. More importantly, who needs a $200k track car with a stick axle?

Again, thanks for doing what you're doing! By the way, what happened to your crazy aluminum chassis Cobra project?

Jenny (the Cobra) is resting during the Fbird build. Honestly, last year I had too many projects, so I idled some to clear my plate. The Roach Camaro is done, Tina's Mustang update is done, and my C10 driver is almost done. Once the Bird is closer, fab done, the Cobra will come back out.

- - - Updated - - -

Nice to see this level of work going into a 3rd gen. Had a friend that put 80k or so into one about 10 plus years ago as a combination of show & go. People at shows would say why on a 3rd gen, I'd say why not. But like with so many builds done 10 or so years ago in a sort of pro street/pro touring/custom style, the chassis & aftermarket suspension really couldn't handle & make proper use of all the heavy big block power, leaving it an underused showcar.

Don't look like you'll have that problem.....

Thanks. I think we will see more 3rd gens and G-bodies very soon.

RobNoLimit

08-15-2018, 05:24 AM

Here's one. Years ago I stumbled onto a link for Mercedes Benz tech archives. There's something like a million + pages of their research and testing base. A few articles that I read stuck with me. On the sides of the "tech" findings, (very well written and charted), we're the engineers notes and comments (off the cuff stuff). One article was focused on their testing to chart "Ride Frequency" as it related to human ergonomics and therefor comfort, security and driver experience. They spent years developing test environments and machines, testing thousands of people, blah blah blah. In the end, an engineer linked something very basic. They found, that the average "most comfortable motion cycle" to humans was around 1.1 cycles per second. The side comment was something like this. "Brilliant! Six years of testing and over $30,000,000 spend has led us to understand that people, on average, are comfortable at 1.1 Htz. That's amazing. To think that we are most comfortable at a cycle that matches the average human walking step is almost unbelievable. After all, Humans have only been walking around for a few hundred thousand years. Bravo MBz." OK, so, don't overlook the obvious. That's the lesson I got out of that. They had other great stuff too. Crazy formulas for calculating the intake runner length from pulse tuning based on rpm/cyl size/torque..... Exhaust Db calcs for muffler volume, shock resistance formulas, sound canceling..... it's all there. Crazy to me that they spent all that time/money on learning this stuff, and then keep it in a public access location. So, the info is out there, we just have to find it.

CSG

08-15-2018, 07:14 AM

IIRC a ford engineer had told me to stay around 1.2 HTZ, seems close to the 1.1 but I don't have an understanding of how that .1 actually plays out in the real world.

SSLance

08-15-2018, 07:27 AM

I think we will see more 3rd gens and G-bodies very soon.

I agree Rob...and can't wait.

RobNoLimit

08-22-2018, 05:30 AM

We're waiting for a few parts, so we are bouncing around a bit. Got to keep moving. Since the project is somewhat unconventional up to this point, we see no reason to go 'normal' now. Our exhaust plan is to route the exhaust (heat) out and under the rockers, then in and under the diff and out the back of the car. The OE rocker is plastic, so we made some aluminum rocker skirts, these are just a bit wider than the originals. This gave us just enough room to fit a 2 1/4" x 4" oval tube tucked under the rocker, with the bottom flat and flush with the bottom of the chassis. We are building the headers as well, but I started with the side tubes to get a target to aim the collector to. The side tubes consist of the oval tube, an oval 90 bend, and a transition piece from oval to 3" round. The only way I could 'lift' the front turn was to slice/pull/weld. But, it came out pretty nice, and I don't think it will harm the flow. Anytime you weld stainless tubing, you should gas purge the inside. (you tube) the results are much better. Once the side tubes were fabbed, we connected the collector and started fitting primary tubes.

RobNoLimit

08-22-2018, 05:49 AM

All of the exhaust material came from Vibrant Exhaust. The header flanges are 3/8" thick, OK, a little heavy, but the shouldn't leak, so it's worth it. The primary tubes start 1 3/4" and then step to 1 7/8". The collector and V-Band are 3". There are some compromises. The primary tubes are a little shorter than desired, at appx 17". This will effect the torque curve a bit, but the trade off in heat management is worth it (we think).

Keith's current car, Velocity, weighs in at 3540 lbs, and runs a crate 525 LS3. And, it's pretty competitive. That's 6.7 lbs/HP. If we put the same motor in the 'Bird, that we expect to weigh around 2600 lbs, that would be about 4.9 lbs/HP. That would have the same power to weight ratio as if we put 715 HP in Velocity. So, if we give up a few here or there to get a better all around car, it's a net win. We plan on a full belly pan, so exhaust in the tunnel is a heat generating nightmare. Just look at some other current builds. Fuel plumbing, oil lines, brake lines and wiring all get taxed from the excess heat, and we don't want the problems.

RobNoLimit

08-22-2018, 05:57 AM

The passenger side has it's own criteria. The oil tank is in the corner, and we have to be careful of the distance for heat. Eventually, we will bu using some additional heat barriers, like aluminum panels and products from DEI and such. Yes, the oil tank is up front. Our weight plan says this is the best location. I have never been a big fan of 30 feet of oil line anyway, and again, it keeps heat out of the rest of the car. We'll have plenty to keep us warm, I'm sure of it. Once the exhaust is past the drivers compartment, it will move back inboard, and head back under the axle bells. We will build one muffler in the back with a single outlet. Keeping the car under 92db at WOT is a must, so we will use all of the tricks we know.

SSLance

08-22-2018, 07:46 AM

Nice work on the headers and exhaust Rob!!

And thanks for the sneak peak at the front suspension as well. :naughty: :ssst:

Peter Mc Mahon

08-22-2018, 06:09 PM

Are the tabs near the dry sump tank for the shock? Also, what is the tool laying beside the header on the bench with the splines in it for? Always like your builds, keep the info coming!

FlyDoc

08-22-2018, 06:27 PM

I like this build!
it fallows what i would like to do with a 3rd gen, fallowing the tragic end to my car in Hawaii.
I was planning a C6 type suspension, not sure of type of differentials, i like the quick change direction. I am unsure on what way to go with a trans, auto-manual, C6 out back or in conventional location, but I want to go AWD, so placing the transfer case front diff. engine setback and driveshafts would all create there own challenges. I also have researched adapting an ABS system from an OEM, I have did found a company that sells ABS systems but they are supper pricey!

jlcustomz

08-22-2018, 06:42 PM

Definitely can appreciate all the planning & engineering going on here. At the levels builds have gotten to these days it's a good thing to push way further ahead of the average stuff.
As far as loosing a little torque from shorter header tubes, that could even be a positive thing @ 2600 lbs weight which could also play well with a higher revving engine combo.

Thinking & working way outside the box can be a lonely place at times, but the breeze you feel from the freedom it gives you sure feels good.

RobNoLimit

08-24-2018, 04:56 AM

Are the tabs near the dry sump tank for the shock? Also, what is the tool laying beside the header on the bench with the splines in it for? Always like your builds, keep the info coming!

HAHA, not much of a 'tool'. It's an IRS CV carrier (scrap), but, it's heavy and it works awesome to set header tubes on to weld. Poor people have poor ways. Use what you can. Yes, the tabs are the chassis side shock mounts.

RobNoLimit

08-24-2018, 04:58 AM

Thinking & working way outside the box can be a lonely place at times, but the breeze you feel from the freedom it gives you sure feels good. Nice thought. Thanks.

cornfedbill

08-24-2018, 05:57 AM

Thinking & working way outside the box can be a lonely place at times, but the breeze you feel from the freedom it gives you sure feels good. Nice thought. Thanks.

But would you do it any other way?

RobNoLimit

08-29-2018, 05:10 AM

More exhaust picts. The pass side gives you a good look at where the exhaust runs, and how it fits the body. The drivers side shows the new lower rocker, fabbed from .090 5052 alum. These are the same height as the OE, although straight on the bottom, and are a little bit wider than the OE, about 1" per side. From the underside you can see how the oval tube is flush. Lots of other stuff to see as well.

RobNoLimit

08-29-2018, 05:18 AM

More exhausting. Top down look in the back shows the routing in and under the CV stub shafts, then back to the muffler. This external routing does not offer placement of a "X" or "Cross-over", but, we are using a single merged muffler. Length of the exhaust before the muffler may tend to produce a more 'pulsing' sound, so we are hoping that a large single muffler will smooth out the sound and keep the noise down. The large single oval outlet will fit into the new trimmed rear bumper. There are rails on the bottom of the muffler box to add diffuser panels to.

First tag on the car. I'll send a shirt to the first one who can ID the quote.

andrewb70

08-29-2018, 05:33 AM

Rob,

You guys are killing it with this build. I don't know much about suspension geometry, but from what I can tell, the level of creativity is certainly very high.

I am a sucker for driveline components and I really dig the quick change center with the modern Rzzepa CV joints. Hopefully you're working with Frank at the DriveShaft Shop for some custom rear axles. I would also encourage you to push further and utilize a dual CV driveshaft. I realize that this is a race car and NVH is a secondary concern, but anytime that vibration can be reduced, that will contribute to component longevity.

Andrew

craigs73

08-29-2018, 05:42 AM

this is amazing and seeing these 3rd gens done makes me want one at this point

RobNoLimit

08-29-2018, 05:47 AM

Keith was here yesterday and we spent some time going over the car and had a 'measuring session'. With the seat in the car he climbed in and sat in there for an hour and a half or so. We set in floor panels and mocked up pedal placement and steering wheel placement. I have my own thoughts on where they should be and they also need to fit the driver and be comfortable and workable. Space is a premium so we have to be careful. Even with driving shoes on Keith feet get a little tangled in Velocity so we are working on the spacing to cure that. But, we can't go too far apart as we still need the ability to left foot brake or heal/toe when needed. The cut parts are a first round set of parts to set the column and pedals. - all were revised after the test fit. Yes, tape can be used as a clamp.

Peter Mc Mahon

08-29-2018, 05:51 AM

Was it JFK talking about going to the moon?

RobNoLimit

08-29-2018, 05:57 AM

This will be the layout. I had a Wilwood firewall mount pedal set, and we did try to make use of it, but in the end, it was too much of a compromise. The ratio is not exactly what we wanted, pedals didn't fit as nice as we would like and getting to the masters would be outside of our maintenance window. SO, custom fab it is. If you looked in the last set of picts, you may have noticed the manual rack. Being sick and tired of pumps,pulleys,belts,hoses,coolers,heat and leaks, we are not using conventional P/S. We are using an EPAS assist motor on the column input side. Again, more fab. The 3rd gen is from one of the guys at Currie ent. Looks pretty cool. And a pict from last years Chevy Trucks 100 Celebration in Ft Worth. We were invited down to do Truck Auto-X demos for the GM top brass and the media. It was a pretty nice deal.

Kcorrigan2

09-02-2018, 01:51 PM

When we (Rob and I) first started talking about this build we had to decide on a build platform. I wanted a car that meant something to me and had great chactacteristics. We wanted something that compete on road courses, standing mile (Texas Mile), autocrosses, time attack...etc, etc...and be ok to drive on the street. The first new car I ever bought was a 1985 TransAm. That was a beautiful car with the tuned port injection...I put a lot of tires on that car!
I considered an IROC, which I love, but we know everyone will be doing that. Firebirds have always been the under-appreciated GM sports car, IMHO. The car has the lowest CF (slippery), came designed with ground effects...and they are cheap to find in less than desirable state...perfect for carving up. Not like Velocity!
So, we decided to take this car “as far as we could” No normal thinking here...let’s take the best of all Motorsports and build a car that looks great and will compete with anything anywhere. The engine will evolve as my driving skills allow it to and will surely end up on KILL...but we will start conservative so I get really good in the car before adding power.
The engineering that Rob has done on this car is just plain awesome...just look at Hellboy. That truck is now what...7 years old and still is capable of winnng events...and this car will be way faster than Hellboy...just by the numbers.
There are no risky designs here, no guesswork. Everything is planned, thought out, designed and built to last and be wicked....stay tuned for more!

Angry

09-06-2018, 05:43 AM

Wow, .....A big call to be competative with so many different classes/disaplins....... just awsome engineering guys....n a credit to your n your fab skills Rob,..
cant wait to see this beast on my next visit.....

Awsome stuff as usual.....keep building n keep posting

Peter Mc Mahon

09-06-2018, 11:51 AM

So who is the quote from Rob?

wally_245

09-06-2018, 12:50 PM

Wasn't it Einstein?

shawn

RobNoLimit

09-14-2018, 12:43 PM

Ok, sorry, the quote (or close to it) was from Elon Musk (Space-X, Telsa) And to be honest, he may have borrowed it. But it is a handy thought.

On to P/S. We all want power steering, but in the last 50 years, we haven't made a whole lot of advances that people are taking advantage of. In the big picture, hydrolic P/S works backwards. When you need it most, at slow speeds with the brake on, the pump is at it's lowest output. At freeway speed, the pump is working like crazy, and you don't need it. So there is a good/bad to the standard P/S system. On the + side, tried and true, lots of parts available. On the - side, pumps go bad, racks leak, makes heat, needs a cooler, belt fails, ... We have all seen or had these issues. We are trying something different. After some searching (and testing other EPAS racks such as Mustang, Corvette, and Camaro) we chose to use a Woodward manual rack These are specially built with a wide gear contact to deal with "Powered input", and I have to say, this is the smoothest rack I have ever felt. The column and EPAS is from a Saturnn View. These are some of the strongest motors available. We got an EPAS column with the mounts and shafts on Ebay. The column spline is common, so NRG has a disconnect hub available. The column also has a tilt feature, which we used during the mounting. We also used the upper steering shaft with slipshaft and U-joints. This connects from the EPAS output spline down to a 3/4" DD shaft, so the steering hookup was easy. The nice thig is that the EPAS column itself is not modified, so if we need to replace it, it's an over-the-counter part swap. There are also some aftermarket electric control boxes for these so you can adjust the level of assist. The steering so far feels great and I am very hopeful. No pump, no hoses, no belts, no cooler.

RobNoLimit

09-14-2018, 01:08 PM

In the last pict you get a glimpse of the pedals. Due to the column configuration the standard firewall mount or reverse mount pedal sets are a no go. - We tried. Just as well, the standard pedal ratios of those kits are not really what we wanted. After what seamed like a Calc-160 finals project, it was determined that we wanted a 6.35 (or 6.4) to 1 pedal ratio. The pedals are made from .120" CM sheet, hand formed and welded up. The pivot point is a pair of caged roller bearings in a 7/8" x .063" tube (part of the pedal) that rides on a .550" dia stainless shaft. The clutch pedal has a set of tabs for a 5/16" rod end to actuate the clutch input rod. For the brakes, we used a Wilwood balance bar bearing, sleeve,bar and bar link mounts to push on the twin brake masters. At the moment we have a 3/4" clutch, and 13/16" (rear) and 3/4" (front) brake masters. It would not surprise me if the car feels more comfortable with a 3/4" (rear) and a .700" (front) down the road. Yes, the clutch master is tipped. We could A) use the smaller "mini" masters (solid so you can't see in), B) space the masters farther out from the pedals, (forcing the dash out as well) or C) tip the clutch master. We chose C. The dash will cover the most of these with view ports to see the fluid levels from the drivers seat. The pedals are rock solid and super smooth. The assembly before mounting, pedals, mounts, bearings and shaft weighed in at 3.1 lbs.

Also, I started some floor and firewall fab. The drivers well is pushed forward a bit to get full pedal stroke as deep as we could adjust the pedals. This is a little thick in .090" alum. but will probably take some abuse. Eventually, a doubled 'heat block' panel in .050" will be spaced in front of the foot well. All in all, the seat position to pedal reach is very comfortable. pedal position feels great and the column position is very natural. We are happily chugging along.