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Old 19th April 2009, 01:00   #1
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Default My quest to build a AC Cobra Replica

The quest started almost 7 years ago. Then I wanted to build a caterham super 7 replica. Got started with a fiat chassis and did some modifications to it. But ended up scrapping it as the costs involved was too high ( for me when I was still a student ). As they say old passions seldon die I am back with a new project this time around.

Here is what I plan to do

1. Acquire a very good replica scale model of the AC Cobra
2. Get it converted into a 3D model with a laser scanning CMM
3. Import the model to Catia ( heard is easier to work with than pro-e )
4. Section the model as needed
5. Generate machine codes for the model
6. With a CNC machining centre get the sections milled out on a block of polystyrene foam
7. Assemble the foam pieces
8. Fibreglass and take a mold out of it
9. Get a fibreglass body!!!!

Now once I have the fibreglass body I am planning to build a space frame around it. Once the frame is done I am planning to work on the suspension and other parts.

For now I want expert inputs on the scanning and milling part.

A reference website I stumbled upon - Polystyrene model making process, exact polystyrene replicas, polyurethane foam copies, 5 axis polystyrene milling machine, raw polystyrene blocks
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Old 19th April 2009, 01:10   #2
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Harrie, this is an amazing coincidence. just a couple of hours ago, I was looking at a little scale model of a Cobra and was thinking "what would it take to replicate it into a fully running car?"

then I see this thread. all the best dude.
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Old 19th April 2009, 07:13   #3
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I can see your enthusiasm in resurructing a classic. But fabricating a handfull of body panels with clean fit is tedious and expensive too. And on top of that you've got to put together chassis, suspension, engine, intrerior and upholstery and ensure their proper functioning.
I assume you have the brains and the Gandhis to put it in together. To have your work cut out, you could contact Chinkara Motors who have built an authentic replica of the AC Cobra. Instead of putting your efforts into body-building(car's of course~!) as proposed, you could channelize into sorting out the suspension, engine mounts, vibrations, gearbox ratios etc etc......
(Would love to assist you and gain some hands on experience since I've opted for Non-traditional machining as elective this sem.)
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Old 19th April 2009, 09:59   #4
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Money is not an issue as of now. Just want to go through with this.
Here is a link to the old thread i had created for the same

https://www.team-bhp.com/forum/modif...d-kit-car.html

Got up refreshed this morning and found that there are quite a few 3D models already available. Have to check out the models in detail and will probably try doing a 1:10 scale this weekend.
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Old 19th April 2009, 14:09   #5
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Hi Harrie,

What is the goal / what do you want from this project ??

1) A great looking cobra replica
2) A cobra replica that performs great
3) Experience building a chassis + all the other mechancials
4) Experience building a fiberglass body
5) A prototype for future builds on the same lines
6) ...
7) etc


Depending on what you choose above...


Quote:
Originally Posted by Harrie View Post
....

Here is what I plan to do

1. Acquire a very good replica scale model of the AC Cobra
2. Get it converted into a 3D model with a laser scanning CMM
3. Import the model to Catia ( heard is easier to work with than pro-e )
4. Section the model as needed
5. Generate machine codes for the model
6. With a CNC machining centre get the sections milled out on a block of polystyrene foam
7. Assemble the foam pieces
8. Fibreglass and take a mold out of it
9. Get a fibreglass body!!!!

Now once I have the fibreglass body I am planning to build a space frame around it. Once the frame is done I am planning to work on the suspension and other parts....
In my opinion - this just sounds like a very roundabout / backwards (opposite?) way to do it! Unless ofcourse youre primary choice was #1 and #4 above....

---------

Anyway, have you heard of Factory Five Racing? I think they are the leading producer of Cobra kits.

Mk3 Roadster


I had a chance to visit their facory a few years back. Here are a few pictures (mostly just the Cobra stuff) for you to look at :

Display car dash
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They make the buyers assemble the kits themselves - that way FF has no liability
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Amazing paint quality
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The bodies waiting
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Closeup
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Beefy exhausts
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A welding jig (though this was for the new GTM chassis)
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CNC cutout map for the fibre cutout machine
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The cutting machine at work
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Workers laying up the pre-cut fiber into the moulds
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After its removed from the mould (its then trimmed with a multi-axis CNC machine... i have a video of this
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The chassis
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The final product
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Also this thread has some good links to other home grown projects & aspirations : http://www.team-bhp.com/forum/indian...t-cruiser.html

And heres a link to a shelby crash in india (with another link in there to a pic) : http://www.team-bhp.com/forum/super-...s-kolkata.html (Shelby 1962 replica crashes in Kolkata ?)


Do give us some more details - & goodluck!!
R

Last edited by Rehaan : 19th April 2009 at 14:15.
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Old 19th April 2009, 14:46   #6
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Hi Rehaan, I am basically looking at trying out this mode of product development. And if the successful end result is a AC Cobra replica with just 120bhp I would be even more happy

I didn't want to think of importing the body or something like that basically because it would be cheaper for me to do the same here.

Also this means that in the future it might be possible to build more exotic cars on the same lines ( though they might not be street legal ).

I am going to try and do a 50% replica first. Will be milling it out to check things out. Then will have to find out someone who has a VMC large enough to undertake this project. Or I will have to splice the car up and get my tinkers to assemble it up later.

As regards the chassis and drive train I really haven't thought of it as of now. But planning to get a pipe bender to work on it and build a space frame around the shell. Then do some FEA and modify it accordingly. Will be looking to plonk in a g13 or g16 with the gypsy drive train in it.
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Old 19th April 2009, 14:52   #7
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Dont we have someone who makes replica's in India. I remember seeing some replica's 2 years back at Vahan Yatra. Champa or so , IIRC.
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Old 19th April 2009, 15:39   #8
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Harrie,

Good luck with the proposed project.

1. You'd do good in getting touch with BHPian Riziali. He's been there, done that with his Caterham replica ("Superlite 1200" - Catheram 7 replica (Worli seaface)).

2. Several options to buy ready made kits for the AC Cobra. Maybe, it's a good idea to work on the mechanicals instead?

3. What engine do you plan to use? The favorite 1.8 ISZ?

4. Do you intend to register this car for road use? Plenty of info in the thread link posted above.
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Old 19th April 2009, 18:23   #9
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You are taking a very complex route with Catia and everything. Cobra is a very simple car and you can do it with basic sketches and hand drawings.
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Old 19th April 2009, 19:00   #10
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After all this she will not be street legal as the RTO will not pass it no matter what. Many here have all wanted to embark on such a project but the legality of driving, insuring and most importantly liability to others in case of an accident can be very high so unless there is a change in our RTO laws this will be something to jsut make and keep in your driveway/garage unless you have a private road/city etc where you can do this Ilike the palms guys in Mumbai goregaon who own such vast stretches that they have 2 unregistered Range Rovers for getting around their property!!

Last edited by canonball : 19th April 2009 at 19:02.
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Old 19th April 2009, 22:19   #11
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Quote:
Originally Posted by Mpower View Post
You are taking a very complex route with Catia and everything. Cobra is a very simple car and you can do it with basic sketches and hand drawings.
Agreed, but still we are talking about atleast 2-3 months job here. Whereas with a digitised model we can have a body ready in like 3 weeks max.

I am not sure how it will be possible for us to import a kit car into india legally. Even if we were to import just the body alone he costs we are talking about is going to be around 2L+

If the 3D scanning and milling does not work out or proves to be expensive, then what I plan to do is to cut MDF templates of the body every 15cm or so. Assemble the templates, spread a lycra fabric over the template and fibreglass it to get the body shape.

I am not planning to get it registered. There are places here where I can drive it around without getting it registered Ok let me qualify that statement - I could drive it around in our factory we have like 3-4 kms long track there.

I havent really thought of the mechanicals part of it. I have some one here who was closely involved in building some open seater formula cars. So planning to leave the mechanicals part of it to him though I will be closely involved in the build.

As of now no solid plans on the engine. Will take a call on it once the body work is done. The chassis will be over engineered from the beginning. Will be doing a round of the Pudupettai market. Will have to see what turns up. But has to be something that will be fun. For a fibreglass body tipping the scales at 600kgs max even a 100bhp RWD would be fun.

Last edited by Harrie : 19th April 2009 at 22:33.
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Old 20th April 2009, 14:44   #12
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Harrie,

It seems you have access to 3D scanning and CNC milling without having to pay the normally ridiculous prices (especially for a large-sized project like this). If that is the case, then it sounds good.

Quote:
Originally Posted by Harrie View Post
...If the 3D scanning and milling does not work out or proves to be expensive, then what I plan to do is to cut MDF templates of the body every 15cm or so. Assemble the templates, spread a lycra fabric over the template and fibreglass it to get the body shape....
Sounds decent in theory, but im not sure the lycra idea will work out so good in reality.

We used a similar technique when making a mold for a CF seat.

1) Made the model in 3D on the computer
2) Took a cross section every X inches
3) Took a print-out (on a large plotter) of that section profile
4) Pasted those printouts onto sheets of foam and manually cut the profiles with a hot wire
5) Stuck the sheets of foam together in order
6) Smoothed it out by hand sanding etc

Pics of the process :



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Read more about it here : http://www.team-bhp.com/forum/techni...made-fsae.html (Pics: Carbon Fiber Seat - How it was handmade for FSAE)

cya
R

Last edited by Rehaan : 20th April 2009 at 14:45.
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Old 20th April 2009, 15:17   #13
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good luck on your project.
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Old 20th April 2009, 15:54   #14
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Quote:
Originally Posted by Harrie View Post
Agreed, but still we are talking about atleast 2-3 months job here. Whereas with a digitised model we can have a body ready in like 3 weeks max.
Sounds overly optimistic personally would not vouch for that time line. Based on your inputs prior to this post all you will get is the outer skin of the car and there will be no rigidity planned in neither the lines of the car.

Quote:
Originally Posted by Harrie View Post
If the 3D scanning and milling does not work out or proves to be expensive, then what I plan to do is to cut MDF templates of the body every 15cm or so. Assemble the templates, spread a lycra fabric over the template and fiberglass it to get the body shape.
Check Rehaan's post it is definitely not that simple.

Quote:
Originally Posted by Harrie View Post
For a fibreglass body tipping the scales at 600kgs max even a 100bhp RWD would be fun.
Reminds me of a mad session I had for a while with the Dolphin I bought. Had to scrap that Idea. Closest car that comes to the lines of a AC Cobra to play around with would be a Herald's chassis minus the body, add a custom space frame and then mold the body around it. 600 kg's is a pipe dream even 100 horses are a challenge if the body flexes.
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Old 22nd April 2009, 20:58   #15
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Quote:
Originally Posted by Psycho View Post
Reminds me of a mad session I had for a while with the Dolphin I bought. Had to scrap that Idea. Closest car that comes to the lines of a AC Cobra to play around with would be a Herald's chassis minus the body, add a custom space frame and then mold the body around it. 600 kg's is a pipe dream even 100 horses are a challenge if the body flexes.
Sounds interesting....can you elaborate?
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