How are all the budding chassis Designers fairing?

Hello all,

I've been reading the posts and threads on this page, paying particular attention to posts that discuss the design of a modern chassis for the GT40 replica, or indeed, the design and development of an authentic looking monocoque.

It would be interesting to see how all the guys who have been using CAD and even pencil and paper in one design have been doing with their respective projects.

One aspect that I found quite funny was that there was one person who was building a monocoque from dimension given to him from a genuine chassis, and couldn't divulge the information as it was secret! Now, in my humble opinion, if the purpose in keeping this information secret, was to stop people getting their hands on such information and making copies of the hallowed chassis, then isn't it ironic that the person with these dimensions is making a replica monocoque chassis?

I find this as a bit of getting one over on everyone else.

I admire the fact that so many people share ideas on this forum, from every aspect of motoring life, not strictly GT40 related, which goes a long way to demonstrate the quality of this forum.

I'm not a designer, although I'd like to have the skills and time to do so. Are there any members who would be interested in sharing details of their designs, for budding builders like myself? I am a fitter and Turner by trade, and have access to a pretty comprehensive, if olde worlde, workshop (manual machining tools, not CNC yet). So while I'm willing to pay, and I'm sure others would be prepared to pay for a design, there could be a barter of design vs finished product.

This may be too difficult, maybe the web hosts could incorporate a "shop" for designers to post their products. Some money goes to the forum, and the majority to the designer.

Any comments?

Regards,

Matt.

 

[Richard]

Hi Matt

You have a PM

 

Thanks Richard, if your still on-line I'm replying to your email as I write.

It is amazing that there are so many talented people out there, giving ideas some room to develop. I think your project sounds fantastic and I take my hat off to you.

I hope more people will join this discussion, I'm not looking for freebies, I'm more interested in seeing how much further people have developed their projects designs. I've seen some great looking CAD drawings here and I believe that this forum could be the place to start a world wide co-operative on designing the ultimate affordable sports car.

 

A lot people have been on their way to produce the ultimate sportscar. We must first define what we mean by the "ultimate" car. In the case of Gt-40 we allready got a fixed outer shape that probabley has to be retained.

In Sweden we got a sort of "slalom course" that is pretty fast, we got four straights for 1/5 miles in between the slaom parts. So hp is a good fature and brakes is getting real punichment. Ok, a Ferrari 360 M;odena is making a 1,28 sec time. Lingenfelter Corvette 1,26. Corvette DRM 500 RSR 1,24. A Radical had SR3 1,20. BUT, a Opel Speedster made 1,21 using a Saab turbo 300 hp engine! Ther is no Supercar even close to it. 187 cars have been tested. And a very well known racing driver did ALL the tests. F,ex Audi TT Quattro 1,34. So we may start thinking how this could bee???

I have a lot ideas about building a fast sportscar, but it is no easy task. And I be happy to be part of a serious project.

Goran Malmberg

 

Hi Goran,

I think your point about what constitutes the ultimate sportscar presents several questions, which I suppose, has been debated for decades, since in every generation born around the time and after the invention of the car has had the same inspirations.

My suggestion included the fact that it should be affordable. And since the potential for a co-operative to have far wider points of view pertaining to technical and aethestic stand-points, then it would be fair to assume that a modular design would be required to make the ultimate sportscar(s). So that puts the Veyron 1000hp engine etc is baasically out of the question.

I think the MK1 GT40 certainly has the visual appeal, and so does the new GT, but the underside has been largely under developed over the years, which is essentially what seperates a good sportscar from a truly mind blowing example. And the basic layout of the GT40 is just plain awesome.

 

Matt.
Guess the GT40 and the Pantera share the same problem of having a poorly designed underbody. Also, a diffusser is blocking off the engine air circulation. Much of these features nessisiates some redesign of the outside body. In the case of the Pantera there are a terrible rear subframe that should be totally cut away for a starter. At first glance the car got very good potential. And it show especially in historic racing where no cars can use aero to a greater extent. Even at Boneville the Pantera show to be very fast, and could be driven without any ballast.

My car weights 2700 pounds, which should be lowered to say 2200. To recieve a modern A-arm layout I must use 18 inch wheels to be able to get the spindles and rear upprights inside the wheels. I need new close to zero Sai front spindle and relocated steering rack. Lower CGH by say 2 inches. And as mentioned, totally rebuilt rear end structure.
So, one wonder if not a new car is to be prefered?

Goran Malmberg

 

Goran,

Its such a frustrating thing owning any performance car. You get it, drive and then find things to improve and adjust. Then one finds something else that could be improved and so it goes round in circles on the quest for perfection. I was on a never ending trail with my Cooper S, but now its being restored back to original spec, with maybe one or two little changes...

I think given the period they were built, they aren't bad cars, especially if one considers the performance. I think there could be significant improvements made to some of the existing GT40 replica chassis out there, especially when considering underbody air flow, and the reduction of front-end lift at speed. I've seen a carbon splitter and a modified bonnet scoop for the GT, which shows that people out there are getting stuck into subtly altering the aerodynamics to improve the overall performance.

Would you go to the exent of all those modification with your Pantera. What's it like to own the De Tomaso?

Matt.

 

[ QUOTE ]
Goran,
1
I think given the period they were built, they aren't bad cars, especially if one considers the performance. I think there could be significant improvements made to some of the existing GT40 replica chassis out there, especially when considering underbody air flow, and the reduction of front-end lift at speed. I've seen a carbon splitter and a modified bonnet scoop for the GT, which shows that people out there are getting stuck into subtly altering the aerodynamics to improve the overall performance.
2
Would you go to the exent of all those modification with your Pantera.
3
What's it like to own the De Tomaso?

Matt.

[/ QUOTE ]
1
These cars where greast at introduction. But, as you said, aero is the problem. Its just that its not easely aplied. Front end lift is also a Pantera problem, but this particular issue is quite easely solved on the Pantera.
2
Well, I dont know. Its not that the car is not funny to drive as is. Its that I know exatley HOW it runs, and if making modifications I can tell what the improvement is.
If I get an idea in my head I like to see if its working.
But in this case it somewhat looks like "destroying" the car a bit.
3
A standard Pantera is nice from a sentimantal point of view.
A fun to drive car. The way I rebuilt it I can make up for pretty much by using horespower and braking potential. The Pantera got a steel monocoque that is 600 pound. Strenghten in the right areas this part of the car does not leave much to desire. I dont know if there is to big a difference to a GT 40 cincerning handling. Maybe it is in original shape, but the basic layout is pretty much the same.

If we look at the new Gt40 its a pretty heavy car at 3400 pounds. It is also 16 inches longer. For some strange reason they are making the cars heavier and bigger than the original, when supposed to be a super sportscar. From that standpoint our old cars and a homebuilt version is probabley a better choice. But the fact remains, the Opel speedster is faster at the mentioned slalom course. An I would like to beat that!
Goran Malmberg

 

[Kevin M]

The big question here in my mind is: Do we define better as “Faster around a race course”, or “More fun to drive”? I think that too often we assume that they are the same, but in my experience they aren’t always.

Without the constraints of rules, I could design a car that would make even F1 cars look slow.

We would start with a sucker design evolved from the old Chaparral sucker car. This gives us downforce at all speeds instead of only high speeds like you get from diffuser tunnels.

Next we use a large articulating rear wing with a fail-safe type overcenter pedal (again like some of the early Can-Am cars). This gives us tremendous downforce in corners without the drag penalty on the straights.

For an engine, an all aluminum BB Chevy or Chrysler Hemi at 500+ cubic inches. With twin turbos, 1,500 to 2,000 HP should be possible in endurance racing trim in a car weighing maybe 1,400 to 1,500 lbs.

The tire companies will have to develop new tires to handle the tremendous downforce and cornering loads, of course. We might have to go to 8 wheels. 4 steerable fronts like the (Tyrell?) F1 car of some years back, and 4 rears. (We will get some scrub from the 4 rears on tighter corners, but it will probably be a needed trade off).

Now that we have a car that can pull 7 – 8 Gs in corners, we need to design a driving seat that lays the driver down on his back and then pivots along the centerline so that the driver and his controls swing (leaning into corners like a motorcycle rider). This will keep the G loads vertical so that he doesn’t pass out. (A pressure suite like fighter pilots wear might also be necessary).

As you can imagine, this car will be far faster than anything ever built to this point. It will also be physically painful to drive and in no way FUN.

Of course the one downside of this car is that any mistake will almost certainly result in the driver being killed because of the speeds.

This is where we come to the allure of something like a GT40. With no aero aids the cornering speeds remain reasonable. You don’t have the issue that once the car gets out of shape and starts to get sideways the airflow through the tunnels and over the wings is disrupted resulting in a loss of downforce just when you most need it to try to save the car. The speeds are such that you don’t need to be a F1 driver just to keep up with the car, a mere mortal can actually drive it.

An old saying that I have found to be true is: “It is a lot more fun to drive a slow car fast than to drive a fast car slow.” For a car to be fun we need to actually be capable of approaching it’s limits reasonably safely with our current skill levels.

Let the debate commence! /ubbthreads/images/graemlins/grin.gif

Kevin

 

[Andy Besic]

Kevin

That is a beautiful statement of reality. Having a GTD with big brakes, sticky tires, excellent handeling and 410hp I can honestly say anything more will make the car more dangerous than fun.

 

Is there anywhere I can purchase a chassis blue print??

 

Gentlemen,

I do agree with your sentiment, we could go to the ends of the earth, to build a mind warping car, but in reality it would never work, as well as looking like a pig. Not very practical.

However, I don't think its too much to assume that if one had a replica, or original sportscar, then as owners and drivers we fell in love with the basic package of dynamics, looks and performance of the car we end up with. However, at some point we would look to improve at least the performance and handling characteristics of the car, to extract just a little more enjoyment.

In my first post, I did mention affordable and sportscar in the same sentence, in fact they were right next to each other. IMHO, the GT40 replica, or authentic is a great sportscar, regardless of what era it was built. Same goes for Healy 3000, the Mini Cooper 'S', the 911, TVR etc, etc. But, as and when I build my own car, there will come a time when I will want to improve the vehicle to suit me. I'm not a big fan of my front wheels loosing feel at high speed, nor do I particularly enjoy watching the nose of the car wander, when the bloody thing is supposed to be going in a straight line. I'm not fond of ponderous steering and skating over ripples, so I'd be happy with a measure of compliance in the suspension set up.

I used to drive my MK2 Cooper S slowly and at my limits, and I have to say that I enjoyed the stability and predictabilty of the way it went forward and left and right at slow or high speeds. As the engine sits slightly forward of the front wheels, there was never a moment of vaugeness in the steering and it would react to every input.

I think my overall point is similar to yours, gentlemen, in that a car should be fun and accessable at whatever speed it is driven and not just above 200kmh. We have to remind ourselves why we're on this web forum. We all love scintilating performance. I doubt we'd be overly happy trying to wrestle a Group B rally car taking our family away for the weekend, nor do we find a 1.6 litre NA station wagon the Nirvana to balls-out motoring. If it was fun we were after, we'd all be driving MG Midgets, or riding scooters.

Hey Stanton, the only chassis design availble on the web for a GT40 is available for free download at http://www.webguy.ca/downloads/kitcarplans. Its supposed to be an ERA GT40, but who knows? Also heard it is a scam and doesn't fit together.

 

[Howard Jones]

I have a GTD with about 370 HP or so, SP8000 Dunlops, adjustable front and rear anti roll bars and a few mods of my own. I think most of the other newer cars on this forum are faster.

I did my first track day a couple of weeks ago and I can tell you that If I put slicks on it, it will be faster than I will ever want to drive it.(lap times).

The one thing that keeps coming up around here is areo lift at "high" speed. The front straight at the track I was on took me to the rev limiter(6K) in 4th. Believe me there is NO areo problem at these speeds. As far as 180+ speeds go I know of no track in the US where I would have my cars anywhere near that fast. AND I believe that no track day organizing body would WANT a track that fast. I am sure you would see temp checanes put up very quickly if the place was that fast.

So supercar hun? Lets start with;

1. It will have to be a home built "kit" because if it is a auto company doing it then we will have another enzo or Ford GT.

2. Now that we are building it ourselfs then we should keep it under 2400 pounds. I would love to see 2000 but the car is going to be "streetable" correct. Thsi will require thicker fiberglass and generally thicker walled tubing throughtout.

3. lets talk about power to weight ratio a little bit here before we go on. 2000 pounds and 500hp gets us 4 to 1. Thats better than a Enzo, so at 2400 we will need 600hp, Good enough?

4. We will be using a mid engine layout like a GT40 right? engine in front of the transaxle? So lets go with a sequencal 6 speed from Quaife. Nice compact, light, modern, and can take the power.

5. Two seats right? Side by side? Right?

6. Range? I like to drive my car about 3 hours max before I get out and fuel it and straighten out my legs. 600 hp ought to get something close to 15 mile per gallon on a nice 75mph run down the freeway. So lets say we want a 250 mile range. That means about 17 gals. So how about two tanks with 9 gals in each. Where should we put them? How about in the side pods so as to keep them and their weight low and in the center of the car. The other place would be between the cabin and the engine room but this makes the car longer and longer will add weight. So this is our first design problem. Where to put to gas? I say lets put it between the cabin and the engine in a fuel cell like all modern open wheel cars. We will just have to work out the fit question.

7. Cooling? water, engine oil, and gearbox oil. In the side pods? This will keep exaust air out of the areo problems later and allow the front of the car to be a much better areo shape also. Exaust the cooler out the sidepods in front of the rear wheels OK?

8. AH!!! Wheels! How big? Lets start with 18inch diameter and 10" wide in the front with 12" in the rear. This will allow for a lot of tire without too wide of a car. Again weight!

9. Total cost of car? Some of you would put this first and I bet others would put this last. Well someone will have to pay for this thing so lets don't get stupid OK. Lets target $100K and if it slips to $125K then we will still be in a range that many people have already spent on "supercars"

Afterall the labor will be free right? We are going to build it in our garage correct? This brings up another question. How do we expence the shop equipment? All against one car? Or how many are we going to build? Are we begining to see the problem guys? What to hell lets don't count anything that doesn't go on the car. Thats how everybody who ever went broke building supercars did it so what s good enought for them is good enought for us. After all the labor is free, why not the tools. We can use them to fix the lawn mower later, right honney?

10. Back to the car. Carbon fiber or fiberglass? Space frame of mono? How about a Mono with fiberglass. We still have a 2400 pound target and I think we will be Ok with fiberglass if we are careful. I don't want to blow the $100K target yet. We may need the other $25K later. All car projects go over buget!

11. Engine.... 600 hp. I'll start this with. Labor will be ours and free. Also for now lets stay with a normally asperated engine. Turbos just cause too much heat and at 600hp will require a computer to run the F.I.etc. Buget buster. Lets stay with a big C.I. light V8. Alum small block? Here we go guys, which one? Ford, Chev, or others. Remember engine size will do us the most good, so which one goes the biggest in cubic inches? Also a few pounds saving here would be very useful.

Well boys we have a start. Ideas? We will need a windshield and a body shape. Oh..... and they have to work. OK

 

[Kevin M]

Well Howard,

If you would be willing to pay about $50K for the completed car instead of $100K, look here:

http://www.factoryfive.com/table/ffrkits/GTM/gallery/gtmgallery.html

And: http://www.ffcobra.com/ubb/ultimatebb.php/ubb/get_topic/f/35/t/000256.html

And: http://www.ffcobra.com/ubb/ultimatebb.php/ubb/forum/f/35.html

Factory Five started out planning to build a GT40 replica some years back, but after a lawsuit from Ford and Shelby, they decided to do an updated version of a GT40. Sort of what a GT40 might be like if it was designed today. The car has Power windows, AC, stereo, and weighs 2,300 lbs. Engine is Chevy LS1, LS2, LS6, or LS7. Transaxle is currently Porsche although others are being looked at.

Kevin

 

[Howard Jones]

What we will end up with will be a CANAM car with a roof and lights on it only limmited by our buget. Given $125K and a track spec RF for example I am sure we can come up with a 600HP 2400 pound supercar. If we use the last $10K to change some bodywork at the front(spliter) and along the sills (straight down to the ground) we could go along way towards a +200MPH car that has some downforce. Then put on some wings and race tires, and you have youself a real world beater.

 

[Andy Besic]

But the car will have no soul.

Little story. I have to start with I hate taking my car to shows, however a friend of mine was running a local show called the showcase of speed that featured race or race bred cars only. There were highly modified vipers, corvettes, dragsters, hotrods, a few Italian exotics 2 Ultimas and others. I was parked next to the 2 Ultimas one of which was just finished to trailer queen status and was displayed beautifully with posters and backdrops. There my car sat in its full race patina finish complete with brake dust on the wheels and carbon on the rear clip.
Guess which car garnered the most emotional response from the crowd...The GT40 mk1....and it made the cover of the local paper... the only picture from the show.

 

[Richard]

Let's get the ball rolling with something based on Howard's 1st recipe. Given the nature of what we are discussing I'll make a lot of assumptions. Please disagree with me often and loudly, and maybe we can hone in on something viable.

Assumption 1:
Supercar means it's got to perform and look like a supercar (interior too), and it must be road registerable and have the appoinment and comforts of a supercar. So, if we are building a one off we can't necessarily be budget driven. If we are building more than 3 or 4 (ie a profitable commercial enterprise) we have to be extremely budget driven or we will fail. So lets start with building a one off, and the budget may actually turn out surprisingly good. The debate can continue down the track about building few, many or a business empire.

Assumption 2:
We can make it 2200Lbs so a 500bhp engine is about right. For a one off we can trim it down from 2400lbs in a lot of ways and still include our AC, stereo and power windows. For example the idea of twin radiators at the back saves very little weight over a single at the front, but ohaving nly one at the back saves all that piping, extra aluminium and fluid weight. We make it just large enough and very carefully design our entry and exitt ducting for maximum efficiency. We put our AC and oil cooler on the other side of the car. The chassis can be made very light and stiff using larger diameter thinner walled tube with plenty of triangulation to beef it up. We can probably ease up on the GRP thickness too with a lot of attention to three dimensionality, foam filling and mounting points etc.

Assumption 3:
We make the chassis out of steel and aluminium rather than carbon if we want a managable budget. All those who have scratchbuilt a spaceframe, please chime in here with a materials cost estimate. I would say around $3K, and the same again for steering, wishbones and uprights if we are clever.

Assumption 4:
We use 2nd hand late model parts where possible. If we bought new, the transaxle and engine would be the most expensive parts of the car. I'm not up on the cost of 500bhp Ford motors, but a recent stock (350bhp) LS1 can be had in Australia for US$1500. Remap the ECU, give it a mild cam, decent exhausts, smooth flowing cool air and I'd be surprised if you wouldn't have close to 500bhp for around $5K total. What's a new LS7 (500bhp stock) worth once it's plumbed in? New Porsche or RBT transaxle $12K? Use a 2nd hand 6 speed TT box from PHII for $7500. See how cheap this is so far? A 2nd hand LS2 might be available a year or two from now when we are ready to buy one for this car.

Assumption 5:
We charge our tools to the car, but not our labour. But what tools do we really, really, really need for a one off? Welder and cut-off wheel - yes. Lathe - not worth the cost if we're only machining rear uprights and suspension bush holders. Draw it up and subcontract it out. Pneumatic nibbler, wrench and rivetter - not necessary but not expensive. We also pay someone what it takes to optimize our suspension geometry on Susprog 3D. If the performance target is the Enzo, we use the same sized wheels, tyres and brakes. As our car is lighter it will do better (excuse the sweeping generalisations).

Assumption 6:
We make a full sized mockup of the bodyshell from what is at hand - foam, plaster etc on wooden structure. We take a mould, pop out a GRP bodyshell and then cut all the shut lines and then make the internal return panels separetely. $2K all up?

Assumption 7:
We spend everything necessary on brakes, paint, interior, wheels, tyres, faux carbon panelling & supercar bling. This will cost as more than everything that's gone before, but unless we go crazy with expensive bespoke parts our budget will still be well under $100K.

At the end we will have a one off Enzo beating supercar for little more than the cost of a scratch built spaceframe GT-40 that also uses 2nd hand parts. I just hope it looks good!

Anyone want to suggest how we design and build production supercar? It'll be very different from what my ramblings above!

 

[Mike Dozier]

Richard

This sounds very similar to Factory Five's GTM
(see above links). There seems to be quite a large
buzz on the FFR Forum about the GTM...more than I
would have guessed.

My inital reaction was that the GTM would be a nice little
niche product...but nothing produced in any volume.
However, it's possible I'm wrong....and the silly thing
could take off. If so, it could easily exceed the (small)
US GT40 population in a very short time.

Is that good or bad? Probably a little of both.

MikeD

 

[Ian K]

Mark La Vea's Xtremeclassics has some nifty aero devices -
I wonder how well they work.

http://www.xtremeclassics.com

Also, there was apicture floating around here of a race car
based off a GT40 replica, but I cannot locate it. Had some
definite aero mods including a rooftop scoop for the engine
compartment and a nice spliiter.

Ian

 

[40 Bud]

There was a highly modified GTD (red as I remember), with lots of aero changes, running in Sweden several years ago - anyone have some pictures?