How are all the budding chassis Designers fairing?

[Howard Jones]

Let me ask a couple of questions.

1.Do we think that saving 200-300 pounds will cost less or be easier that gaining a hundred HP. At the 2400 pound mark 200-300 pounds is a lot. Whereas going from 300 CI to 400 CI is pretty easy and cheap. The gearbox choice will not be different at 500 vis 600HP and cooling will not be much different. I say live with the slighty heaver car and go for more power.

2. As far as AC goes then I guess we will need it but I'm not convenced we need power windows or much bling. We certainly don't need faux crap like fake carbon or oak dasboards do we?

3. Brakes, Wilwoods are 20% of the cost of bremos. Size would be as large as will fit into a 18 inch wheel.

[Matthewbmason]

I'm with Howard on the interior and exterior bling - let's keep the concept simple. The use of alternate materials to cover seats, dash etc will make a great deal of difference. Alcantara, Neoprene rubber and a good quality floor covering should turn the interior out quite nicely. Air Con needs to be considered and allowed for in the design for hotter climates, as well as natural ventilation in the cabin.

Externally, I'm quite a fan of the simple lines of the GT40, but find some detail of the new GT a little over the top - All those disection lines are too much. Lighting has to be off the shelf items, I like lamps that are enclosed behind perspex appertures, so off the shelf items from Cibie, Bosch, Narva et al would be more than sufficient.

We'd have to ensure the cabin area covered design regulations from the US and Canada, European Union, Australasia for single vehicle manufacture, or small volume - less than 25 for Australia, if I remember what you wrote, Richard.

What we'd have to consider also is the availablity and suitabiltiy of parts from the various regions, A Ford or Chev V8 might be easy to obtain in the US and Oz, along with parts back-up, but In Europe it might be prudent to allow for Engines that are more readily available there - say the Vauxhall/Opel V6s, or even Jaguar V8s!

I like Richard's idea of developing a lightweight chassis from large diameter - thin walled tube (round or square) to give greater strength and rigidity weight for weight. Could we consider Aluminium tubing for this? A saving of 200lbs in chassis body weight, will also transform the extra easy 100hp power increase over a 500hp unit into another league. But failing the upgrade to the engine, the std 500hp will be more than enough power for most people. Well, I'd crap myself in it the fist time I pushed the loud pedal to the boards...

18" wheels sound good, but no variation between front and rear tyre sizes, especially if we consider carrying a spare.

Hey Richard, I was writing you a message a couple of nights ago, but my server decided I'd had too much fun and cut me off, and I lost the PM. Will drop you a line over the weekend, I'm filling my roof full of insulation this weekend and installing the air-con. Its so good to be home from work, to do more work... The joy of a responsible de facto relationship!

Anyone prepared to start the process off? I've got TurboCAD Deluxe V11 coming in the post, so will be waiting for that to arrive - then I have to learn how to use it!

[Richard O'Clery]

Hi Guys

I'm strongly anti-bling myself, but I mentioned it because I guess a supercar to rival Enzo and Zonda needs some kind of interior statement. But I based my assumptions on doing a one off car, rather than a production supercar, which might need something more zappy inside. I would personally prefer to do a practical racy interior with alcontara over GRP, and a small amount of brushed ss, chrome or carbon detailing.

While an aluminium spaceframe could probably save a little weight, I would be against it for both a one off and a prodution car - partly because I'm not sure if it would be as durable (energy absorbtion, fatigue, work hardening?) and nobody else seems to do it and I guess they have a reason. Matt, you probably know a lot more about this than me. Sure, I agree for a production monocoque...

Regarding weight, a heavier car with a bigger engine might be better for acceleration, and with really really good dynamics we might beat the Enzo on cornering and braking as long as we still come in quite a bit lighter than it. But I think that where weight can be saved it should as the handling gains will outweigh acceleration. Let's make it lighter and then add the bigger engine!

Designing and building a lighter chassis and bodyshell won't cost any more, and one radiator at the rear can save up to 70lbs of pipe and fluid weight! Dropping AC, stereo and power windows would save a lot of weight, but this comes back to what a supercar is supposed to be - again in a one off for any of us we might be happier than the general market to lose some creature comforts. Now if we were building a low volume racing car for the road, we could ditch all the heavy stuff (even alcontara weighs something)!

Matt, I hope the roof insulation goes well - it will be warming up this weekend. Also keen to hear about TurboCAD v11 - I'm still on v7.1!

[Andy Besic]

Do you all really want to start from scratch to build another version of a GTM, Ultima, Noble M400? IMHO it would take years to develop, and the development time could not keep up with how fast the bar is being raised by established manufacturers. Look at the new Ford GT vs Ferrari 360 and then a year later vs Ferrari 430. The Ford GT has already been surpassed and will quickly be left far behind without constant re-development.
Even the Lotus Elise and soon to be released Exige would compete with your proposed car on the lower end of the cost scale. $10k added to the exige in wild motor mods will give someone and aluminum chassis, AC, Windows and probably over 300hp under 2000lb for what $70k?
For a new venture to work the design of the body of the car would have to be something that is timeless and stirs ones emotional passions as our beloved GT40's.
Not to toot Fran's horn but he has the best idea so far. Take the passionate established body designs that exist and put "supercar" underneath...the best of both worlds. I look forward to seeing how his concepts actually work.
My humble .02

[Fran Hall RCR]

Richard..what do you think the chassis on the new new Ford GT is made from???
Its tubular albeit square and rectangular section....and its aluminum

The Audi A8 is also an aluminum chassis as is the new Corvette C6...and the glued together Elise

[Howard Jones]

OK, OK, lets limmit our disussion to a oneoff homebuilt and agree on a buget. We can also assume that we will retain jigs etc. and 1 or two addtional cars to possibly follow on. But not an intention to go into a continuing business. I sugested 100K US could get the job done nicely.

Lets also agree that for the sake of our dicussion we will use the car for < 5000 miles of street driving each year and 6 open track days per year. We can also throw in a short race in a amature club setting once or twice a year. How about 25 laps or less and on a 2.5 mile track.

So with these in mind I want to add

1. Roll cage, like most of the current GT40 builders offer. 1 hoop in front of the seats along the windshield and 1 behind and a central conection with removeable top side window edge connections to ease entry on road use.

2 Onboard fire system. MUST HAVE!!

3. Lets put one radiator in one of the side pods and the other coolers in the other.

4. 15 gal fuel cell behind the seats and infront of the engine but not inside the cabin (this gets us pass several santioning bodys rules for fuel tank location).

Heres one to think about, If we copy a bodyshape from a car built in the eary 1960s we can help ourselves with many goverment motor vehicles depts. We then can design removable body pannels that will later be exchanged with better areo shapes. Front clip, sidepod covers, etc. A little higher cost for additional pannels but not enought to bust our buget. Hm their are several besides GT40's that will work. We only need the basic shape, not a reproduction of the given car underneath.

Buget; I'll give us a start.

1. Transaxle, clutch, flywheel, halfshafts, bellhousing. $20K I might be a little short here depending on HP spec. Lets add another $5K if we go to 600HP from 500HP.

2. Engine $10-$20k. Based on a 400-450 CI American V8 with single 4 barrel carb @ 500-600HP and free assembly labor, ours.

3. Brakes $3k Wilwoods 13" X 1.25" rotors and hats with 6 pots up front and 4 pots in the rear. We will use twin a off the shelf peddle assembly with duel masters and a bias bar. Includes clutch master. We will make our own adapters ar necessary depending on uprights used.

Any other thought?

[Richard O'Clery]

Mike & Kevin, I agree about the GTM - if they have their numbers right (and I'm sure they do) they are seriously showing what can be done with a low volume production car and a smart approach. I'm very keen to see how they go.

Fran, you're absolutely right about the Ford GT. I imagine the production techniques for the others are out of reach of our hypothetical budget, but the GT looks like a spaceframe from what I've seen. Is it welded normally (for aluminium)? Is it all spaceframe or semi monocoque? I must admit I haven't done any research into using aluminium for a spaceframe, so I'm out of my depth...

Howard, I'm curious about your fuel tank location - while it sounds ideal for minimizing the change in handling between full and empty tanks (if it's not too tall) and good for safety, won't it extend the wheelbase too much?

[Joe T]

Interesting Thread, if the fuel tank goes across the width of the Car it can sit in the the area freed up by the slope of the seats, a few sports cars already do this AC 3000ME Etc. Its one of the best places to put a variable mass and normally doesnt creep into the engine bay area.

Do you really need all that Horse power, how about reducing the weight significantly and use a lightweight engine and chassis and focus on the power to weight ratio. I would guess thats why more manufactures are looking at ally. But what about an all fibreglass Monocoque? using bolt in front and rear subframes as well as roll cage, like Davrian or Lotus Elite, Renault GTA(Sort of).

I know, I'm sorry, I forgot where I was for a minute!, can I least make the suggestion of thinking about some of the big Audi or BMW V engines, lighter etc. I'll go away now...

[Kevin M]

Joe,

I certainly like the “Lotus” approach, light weight helps everything, not just acceleration like HP does.

That said, I think you need to define the planned use of the car. At lower speeds, a light car with good power to weight, like a Lotus Elise, can be very fast. Once you get over 100 MPH though, weight is not the issue as far as acceleration. The issue becomes power to drag. From 120 MPH up, if you have two cars with the same power to weight ratio, the heavier car with more power will always be faster.

This was the reasoning behind putting the 427 in the GT-40 Mk II. That car existed to win one race, Le Mans, and with the Mulsane straight, a heavier but more powerful car was faster even though it lost some time through the corners.

So, if you are designing a street car that will rarely exceed 100 MPH, light with low power is better. For faster race track use, heavier with more power will be faster.

Kevin

[Russ Noble]

[ QUOTE ]
heavier with more power will be faster.


[/ QUOTE ]

And lighter with more power will be faster still!!! [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/crazy.gif[/img]

[Howard Jones]

1. Transverse fuel tank.If you use the area at the bottom of a GT40 behind the seats and full width of the car I believe you would have a tank inclousure of aprox 60"X8"X10". Or 4800 CI or about 80 liters. This amount of area will yield plenty of room for a 15 Gal fuel cell. This estimate is without adding length to my GTD.

2.Beginning with a target weight of 2400 pounds and a buget of $100k per car I think that keeping it simple using tried and true construction materials and methods I believe 500-600 hp will be just about right if we are going to take down enzos. To get down below 2000 pounds will require either a race car only,leaving out all road goodies, AC, heat, two seats, cabin carpet insulation etc., or going with a small light engine and power adders, turbo, superchargers. To use a 400hp 4 banger will get very expensive. Fuel injection, intercoolers, lots of addtional plumbing etc. Thisis why I propose using a Alum + 400 CI V8.

Our friend the enzo has 550hp and 3200 pounds. We will need HP, lots of it, Big tires, and great brakes. So big light V8 in the middle, top of the line Quaife gearbox, big brakes and tires and little else should do it. Given we have a $100k to work with.

Make the whole thing out of chrommoly and fiberglass. Light cheep for the performance level.

Anybody been looking a shapes? How about a 910 porche type only bigger. More width and a little lenght.

[Matthewbmason]

Lightweight does it for me, the argument of improved cornering characteristics wins above ramming a huge motor in the chassis and waiting for the battle to start at 100mph plus. I think the basic premise of this chassis/car has been laid out.

1) Mid mounted V8 of some description - although an American V8 looks most favourable due to cost of initial purchase, spares cost/availablity, tuning options etc. BMW/Audi V8s while are going to be lighter and develop more hp per cc, or cu/in, the cost of maintenance, tuning parts availability, cost of initial purchase etc starts to put these engines out of the equation.

2) Wheels to roughly 18" diameter for all 4 wheels.

3) Transaxle transmission

4) Seat two in comparative comfort with good ventilation and the provision for adding air-com. Windows to be non-winding (then obviously non assisted is required), but a sliding window in a similar style to a MK1 Mini is more than possible) Front glass to be sourced from an existing production vehicle to reduce costs.

5) Chassis to be space-framed, clad in steel, or aluminium sheet. Fibreglass body panels to reduce manufacturing costs.

6) Lighting to come from off the shelf suppliers, cibie etc, etc, etc.

7) Braking to come from local manufacturers - Willwood, AP Racing,

8) Suspension to be adjustable, alloy uprights, coil over suspension, with the provision for anti-roll bars front and rear. Rose jointed strictly an option.

9) Cooling to be single radiator, electric fan assisted, front or rear mount. If we go front mount, can we be tricky and us some of the chassis tubes as conduit for coolant. May help reduc weight (obviously coolant volume is increased over a rear mount design), but can also reduse clutter behind the rear bulkhead and further balance weight distribution. Oil coolers, air con heat exchangers to be mounted in side pods.

10) Aero work - No big spoilers/wings. Subtle use of front splitters, possibly skirts and surely an undertray venturi can be icorporated into the design, especially if we use steel/alloy sheet to fabricate the floorpan.

11) Roll cage (can this be incorporated into the chassis design and still pass race regs?) and fire extinguiser must be consider for fitment at build phase, or during race prep.

12) Non-assisted steering

I think 100K would easily cover this work, but I think Richard has hit the costings pretty much on the head. To build a competent chassis would cost no more than a couple of grand, so to the body panels, if we were to build out of fibreglass and fabricate the bucks from plywood and foam to start off with. Remember this is supposed to be a single build car, we are working on here. We could go nuts, but I think we can get by with some savvy design and and a creative approach to manufacture. Lets not consider the labour cost - what cost can we put on the price of love?

[Kevin M]

You know, that list is an almost exact description of an Ultima.

Kevin

[Joe T]

Mmmm, I sort of agree, I know some one who is building an Ultima type car with a V12 BMW engine twin turbo, hes not modding the engine from standard config apart from water injection, and expects 750Bhp! when it blows up he will just drop in another engine, available for about £500-£1000 dependant on mileage.(he already has 2 spares!) It will cost nothing like a 100k, but is it a supercar? it will put most to shame performance wise as the Ultima already does.

I think it all comes down to an individuals idea of a supercar, from one view the Ultima could fit the bill, it also caters for the more power to push a brick along camp.

Incidently it was a 2.1 cc Little Ford Puma that set the fastest time at my local speed trails in Brighton, terminal speed of 150mph did its first run in 9.45 the best 40'S were in the 12's.........
It all matter of horses for courses.

I think a Supercar has to take a different direction, push back some boundaries and be innovative to stand out, Mclaran F1, lamborghini Muira, Lancia Stratos, GT40. I think you have to decide on a direction or objective first then the car will take shape. But I wonder if there is anything left to try with the outline shape, weight and drive train of a GT40 type car thats not already available or under development on here somewhere, how about Turbocharged Rotary Engine??

I love GT40's Lola's etc but from a design perspective I am firmly in the super efficient lightweight camp, not so super cars like, Lotus 8, 11, cars that were giant killers, cars that used brainpower instead of horsepower.

[Howard Jones]

I would think that starting with a RF less bodywork or a Ultima chassis would save a lot of time and effort but then we lose out on the fun of doing our own car. Just about any car that is mid engine and two seats will come out looking the same from an areo standpoint. Then it's just the other two variables weight, and power.

I know a guy that is building 910 porches in his garage. When they are done they weight 900 pounds complete. The problem is in his own words is "These cars kill you if you crash them, yours on the other hand looks like it could take a pretty good hit and you would still walk away."

I wouldn't want to build the car so light that you end up with a unsafe road car. Some things just need to be built with more robust materials when they are ment for a street car.

I think that 2000 pounds is a practical limit for a two place road car, given $100K to work with.

The reason I like big V8's is the cost per Hp is so low. I think a 600hp engine could be built for < $20 per hp. AND last 100K miles.

So we are stuck on ultra low weight small high tech motor or big V8( when I say big I mean alum SB block at its max CI around 450 CI or so). I have to wonder what a Alum SB Ford weights with all alum parts on it like waterpump,intake, heads, etc. compaired to a 2 liter 4 cylinder with a turbo intercooler plumbing etc. I bet there is less that 20% difference in weight overall between power plants. I also bet the bigin will last 3 times as long.

Using our brain to keep it simple is "smart" in the best sense of the word in my opinion. I love high tech as much as anyone but building a F1 car in my garage isn't somthing I could do. Droping a big V8 in a spaceframe would be. Thats all I'm saying. Lets stick with somthing we can do ourselfs with about the same limits we have building our GT40's.

[Richard O'Clery]

I'd be happy to use a big engine as long as it was all aluminium, so it is the lightest big engine possible. I'd also prefer to use a modified modern injected engine, just 'cause it says 'supercar' to me more than any carb engine. A point of criticism for the Joss Supercar was that it was going to be priced between A$450K & A$550K but only have a 2V single cam V8 (Matt Thomas actually built the Joss prototype on an Ultima chassis, so there you go!). If we are describing our design to others as a 'supercar' we probably need a modern FI motor (anything that passes California emission standards will do if we want to ultimately consider an export market). This is not about power or dollars, but about supercar perception - which I admit is very subjective.

I'm not yet convinced we can run a single fuel tank behind the seats and infront of the engine without adversely moving the CoG rearwards (ie having to move the engine back). Twin 7.5 gal tanks may work behind each seat (as long as you don't hear the 'slosh'), or maybe even a tank in the central tunnel a la Ford GT, but development costs may blow this out. Can I suggest a compromise? Let's put the radiator back at the front and take the slight weight penalty while improving the ease of ducting cool air to it. This will also move more weight to the front end, which may help the balance. We can then put 2 x 8 or even 10 gal explosafed fuel cells either side of the engine (like the Ultima). This will help keep the wheelbase as short as possible and will minimise the chance of rupture of a single tank crossing in front of the engine if we get a hit in the rear strong enough to move the engine forward. Also, twin tanks near the CoG mean that at a track day you fill only the tank on the side opposite the driver, to help balance lateral weight.

How heavy are your GT-40s, and Mike and Joe (lucky bastards) your Lolas? (I can't search the weight thread without losing what I've typed here). If you'd be happy to put a 500-600BHP motor in your chassis, I think that gives us a practical starting weight for a durable and safe supercar. The 3200lbs for the Enzo - is this wet or dry or somewhere in between?

I totally agree with 18" wheels, and the rear tyres should be as wide as possible (335s) with all that torque. The fronts will probably be about 225, but testing will determine the final size. If we want a spare at all, use a space saver of the same inflated rolling diameter as the front tyres. Limited to 50mph, a slightly smaller diameter tyre won't be a problem if we ever have to use it on the rear.

I'd give a supercar electric windows unless it was purely a race car for the road. I'd also prefer a modern looking bodyshell. This is the really hard part - the art of the supercar. The Ford GT is the only retro to modern transition I really like. Otherwise we are just building our own version of a Lola, GT-40, 910, P4 etc. Not that there is anything at all wrong with this! I just think a new supercar needs an original modern style. It's the balance of elegance and aggressiveness that will sort the men from the goats.

I'd still go recent 2nd hand mechanical parts where possible for the one off, and save around $30K. If we were to sell a further 2 or 3 from the jigs and moulds, they would need new parts of course, with the purchasers paying accordingly.

I'd look at Harrop brakes in addition to Willwood. If there is some fat in the budget I would probably go with AP, Brembo or Alcon just for that 'supercar' perception.

Another tough question for you all - metric or imperial?