New body 1

[aussielimo]

I'm taking the huge step of designing a body to go onto an existing chassis, so I can use the completed vehicle as a business card for my 'embryonic' design service!!

Chassis' have to be torsionally tested here in Australia, so I'm choosing the chassis of an existing Cobra kit with an approved-for-the-vehicle driveline so that I have no Australian Design Rules hassles when I go to register it. My aim is to simply design a body that will go onto the chassis and hey presto this is what I can do for YOU!! Hahaha!!

Seriously, I've looked at wood sculpting and clay modelling, and I have some pretty rough design ideas in my head. For someone that's never used CAD in any way shape or form but is pretty computer savvy, what's the best freehand CAD system that you could recommend?? I'm told the ideal way is to design what i want, download it onto CD, take it to a plastics/GRP molder, who then feeds it into a moldmaker which creates design out of foam which becomes the plug (step in any time if I'm wrong).

I am in Australia as you can gather, and there are NO automotive CAD schools or courses anywhere, just architectural ones. I'll be strating completely from scratch so your help will be most appreciated.

Cheers

JOHN

 

[GregLocock]

"Seriously, I've looked at wood sculpting and clay modelling, and I have some pretty rough design ideas in my head. For someone that's never used CAD in any way shape or form but is pretty computer savvy, what's the best freehand CAD system that you could recommend?"

I believe some people use Rhino 3d for this.

"I'm told the ideal way is to design what i want, download it onto CD, take it to a plastics/GRP molder, who then feeds it into a moldmaker which creates design out of foam which becomes the plug (step in any time if I'm wrong). "

You might be a bit frightened by the price of that, why would you make a plug rather than the female mould?

The old way is to make a male plug (physically) by carving it and building it up, then take a splash off that to use as the female mould.








Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[kchan711]

Hi John,

Like Greg said, Rhino 3D is good place to create a 3D body. It works using Nurbs surfaces and uses common polygon tools to build your model. In addition, any modern parametic CAD builder such as ProE or Solidworks will allow you to basically freeform surface sheet metal for bodies. The best thing is that their models can usually be accepted by fabricators directly. Being that all of those programs can get pretty pricey, why not try something free?

Go to

http://www.blender.org

. It's an open license graphics modeling program developed by its users. It has a multitude of functions and capabilities similar to AutoCad 3DSMax. You can also use a scanned image to build a model from within Blender. Unfortunately, it's learning curve is sometimes a little steep.

Kyle Chandler

http://www.chiefengineering.net

"To the Pessimist, the glass is half-empty. To the Optimist, the glass is half-full. To the Engineer, the glass is twice as large as it needs to be!"

 

[griffengm]

AussieLimo,
There is a demo download available for Rhino. I tested the demo on a plastics project some time past when we were looking at converting some sheet metal constructs to plastic. It was okay but we figured out how to do the job with Inventor which we already had.
One thing we did on this project that worked well was to go to a molding house and use their expertise in creating the shape. Sometimes you can dream up a shape that may be almost impossible to mold. We found that pencil renderings of the concepts were as usable as CAD drawings. They also worked with us to create much lower cost molds for the low volumes we were to use.
Luck to ya!
Griffy

 

[DKirkham]

Cobras are right up our alley--having made quite a few of them. We are the supplier of aluminum bodied Cobras to Shelby.

You didn't mention what you wanted to make your "business card" out of--aluminum? fiberglass? steel? bondo?

It makes a big difference as which way to go about all of this.

David

http://www.kirkhammotorsports.com

 

[aussielimo]

Thanks for your input, fellas - I'm hoping just to use fibreglass/GRP as the material, and I'm looking at a grand tourer body along the same lines as a De Tomaso Longchamps coupe - simple two-box outline with flat front and rear windscreens. The chassis I'm interested in has an LS3 powerplant with a Jag rear end, and has a good racing pedigree, so the end result could be run in tarmac rallies if desired.

Is curved glass that hard to make, or is it just a matter of some glaziers wanting a large minimum order? All I'm interested in at the moment is the prototype and one tosspot wanted an order for 300 screens to make it worthy his while.

Similar stories would be much appreciated - I'm trying to also get an idea as to what's in store for me!

Thanks again for your help

JOHN

 

[GregLocock]

I vaguely remember $2000 for a custom, fairly simple, windscreen. You might like to get hold of "Race" magazine as it is a good source for questions and answers on Australian homebuilts.

http://www.racemagazine.com.au/index.php?option=com_frontpage&Itemid=1

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[aussielimo]

Cheers Greg, I've seen the magazine in our newsagents here in Oz.

Did the $2,000 you mention for the screen include jigs, moulds etc to make it as a one-off?

JOHN

 

[GregLocock]

I don't know.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[DKirkham]

We paid a few thousand for our first windshield when we had it made in Poland--but that was over 10 years ago. Since then the windshield company has been bought by Pilkinton so I am sure the price has gone up.

We sent them a drawing and they did the rest. Making a prototype windshield is not that difficult. They have jigs with sliding pins in them. It is much like that cool toy at the store you press your face and hand into on one side and all the million pins conform to whatever shape is pushing on the opposite side.

Then, they just heat up the glass and let it settle onto the pins. When you get your glass, you can actually see where the pin touched the glass (but it cleans off).

Also,

Be aware the Jag rear end can not take that much abuse or power in the stock state. (We have probably made 1000 of them over the years).

Good luck...I hope you have a LOT of time on your hands. I would recommend reading all of the Carroll Smith books. The sooner the better.

David

http://www.kirkhammotorsports.com

 

[aussielimo]

Thanks for your advice, David - I'm in no rush and I might even document it for an interesting internet read!

I used to muck around with that pin toy as a kid - I laughed out loud when I saw your reply and I can see it working well! I've been advised to make the front and rear screens the same to save production costs, and that sounds like a great idea as well - also very achieveable with a two-box profile design.

You're right about the Jag diffs - the serious racers here modify a complete Ford 9 inch diff assembly to take the Jag halfshafts and cradle mounts, and put the later '92-on XJS shafts on which relocate the rear brake discs to the wheels instead of being inboard like earlier ones.

I've learnt that the recent W427 project that Holden Special Vehicles has undertaken (think Pontiac G8 with the 427 out of the Z06 'vette) means the production line LS3s and gearboxes that are removed during the retrofit of the 427 are available for next to nix...food for thought.

One of your cars with an Aussie owner has appeared in a recent kit car mag in Australia and received a good rap...a good result when there are cheaper low quality options available in the market.

Cheers

JOHN

 

[patprimmer]

I expect rear windows are a lot easier than windscreens as they do not have to be laminated glass. Plain safety glass or even scratch resistant polycarbonate can be used for fixed glass other than a windscreen.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[DKirkham]

Ahhh,

Yes, we have used Lexan many times. I would certainly take a stab with Lexan--it would be way cheaper. Thank for the thought...I just might be using that soon enough myself.

John,

Thanks for the kind words. We work hard to make our cars as nice as possible. We modify the Jag Dana 44 diffs to take the beating. Stock units are pretty bad. The main problem are the axles. They like to break with high horsepower. Long ago we switched to 17-4 H900 and changed to 30 spline axles instead of the original 19 spline IED's. Then all of our problems went away. We make those in house too. Many of our customers push way over 600 hp in their motors...several have even gone over 700 hp.

Here is a link to our latest project.

http://clubcobra.com/forums/showthread.php?t=85278

David

http://www.kirkhammotorsports.com

 

[patprimmer]

David

If you use Lexan or any other brand of PC, make sure it has a scratch or mar resistant treatment. Untreated PC has very poor scratch resistance.

It is doubtful if even scratch resistant PC will live long in a wind up window as the weather strip on a dirty window will wear the coating and eventually scratch the surface.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[DKirkham]

patprimmer,

Yes, when we do use Lexan, we always use it with the scratch resistant coating. For our project (prototypes, etc.) they don't need to last long.

Thanks for the tip!

David

http://www.kirkhammotorsports.com

 

[aussielimo]

Just spoken to a plastics manufacturer who has been sprouting the virtues of plastic (bumper bar grade) over fibreglass...less density means low weight, higher impact resistance, easier to prepare for painting and a better quality finish.

I don't like the inconsistency of plastic with its tendency to shrink and distort in the mould, and I don't like its added cost over GRP (fibreglass to you Yanks ). I'd prefer a metal body overall, but the cost of hand forming or stamping aluminium/steel in dies is prohibitive.

Comments?

Cheers

JOHN

 

[patprimmer]

Go with FRP.

Bumper grade is polypropylene/EPDM allow. It is difficult to get paint to stick without special treatments and primers, and it has a very low flex mod and a very high co-efficient of thermal expansion. Bumpers need a lot of design work so they at least appear to fit the car at various temperatures.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[GregLocock]

For one offs there is no doubt in my mind that fibreglass is the way to go, and there are plenty of expensive cars that were made by the method I outlined above. Lotus did go to metal tools eventually, but I bet all their low volume stuff was glass tools.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[aussielimo]

Been having serious talks with a GRP moulder, and he's actually come up with a surprisingly good idea...some input would be great.

Here in Australia, we make lots of car-based utility vehicles which we call 'utes' (think El Camino) and one of the current variants from Ford is the Falcon ute, which is available as a cab chassis (see link) and he has suggested that a mould of a bare cab shell presents the best option.

1. The mould is a copy of a vehicle's cabin - donor parts from that model will bolt straight in, including dash, seating, screens, HVAC controls, etc.

2. Should a frame design be required, it could closely follow that of the donor vehicle so it accepts subframes, suspension, driveline, etc.

3. Someone's already gone to the trouble of making the cabin dimensions suit tall and wide folks - bonus!

I can only see advantages in this - anyone have any bad news I've overlooked??

Cheers

JOHN

 

[patprimmer]

Some of us might know a lot more than you imagine about Australian utes and the Falcon in particular.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.