# The cost of a carbon fiber car chassis

#### mastermechanic

Hello everyone!

We're getting prepared to an electromobile car efficiency challange as a team. I'm gonna take place in the chassis and exterior design team. I have lots of question but today I'm gonna ask one of them.

How much does it cost us to produce an ordinary car chassis? I'm trying to reduce the weight as possible. Actually the word "ordinary" is not compatible with our challenge because the car will be relatively light and small, so chassis will not have the same complexity with an ordinary car. We wont do this directly but I'm just trying to have a general idea about that, of course we will have further research.

So what do you think? How much does it cost to produce an electromobile car chassis with carbonfiber?

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#### berkeman

Mentor
Asking about high-volume production costs of regular car chassis probably is not a good comparison to custom chassis design and fabrication in very low volume. You could look at the costs of custom race car chassis design and fabrication for a better comparison, maybe.

Also, have you looked at the light-weight chassis designs and fabrication that go into the solar car challenges? That is probably a lot closer to what you are working on...

http://funds.gfmcdn.com/8601175_1453830842.7134.jpg

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#### CWatters

Homework Helper
Gold Member
I think things like bucket seats for go carts are made from 4-6 layers of 2-300g/sqm cloth with something in between like a foam. Chassis for a light weight car might be similar? How many square meters of carbon cloth would that be? Perhaps double the cost of that to cover the cost of the mould, resin and sundary other things like reinforcement patches. Add something for metal fixing points?

One issue is changes. Much easier to change a welded tube chassis than to change the mould and make a new carbon one.

#### mastermechanic

Asking about high-volume production costs of regular car chassis probably is not a good comparison to custom chassis design and fabrication in very low volume. You could look at the costs of custom race car chassis design and fabrication for a better comparison, maybe.

Also, have you looked at the light-weight chassis designs and fabrication that go into the solar car challenges? That is probably a lot closer to what you are working on...

http://funds.gfmcdn.com/8601175_1453830842.7134.jpg
View attachment 221991
Nope, unfortunately :(. We're going to design a car that's very similar to the normal ones actually I can say it will be a "real" car. The race inspectors are going to examine the car in terms of security as well, if they don't find it reliable we'll be disqualificated. So, almost everything that exist in regular car chassis should exists in our car (chassis legs, roll bars etc.)

Since it's an efficiency challenge, I thought, even though it's expensive, if the performance/cost is high, it worths to design it with carbon fiber.

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#### anorlunda

Mentor
Gold Member
I didn't find much on cost. But I did see a lot of carbon fiber DIY videos on Youtube.

I believe that commercial cars use carbon fibers plus other materials in their frames. Of course the best guess for other materials is steel. But how much steel and where are open questions.

Whoever builds it safely will have to do a full strength/stress/tortion/bending analysis first. I don't know how much you consider expensive, but I would not be surprised by $100K just for analysis and design. Of course you can skip some analysis by overbuilding it bigger and heavier than the absolute minimum. But that conflicts with your desire for minimum weight and maximum efficiency. You must think about that carefully because you may reach the point where and additional 10% decrease in weight costs 1000% more. In other words, expect a cost-efficiency curve to look like this. A car is smaller than a boat, but more complex. This link http://www.sailingscuttlebutt.com/2013/09/26/cost-compete-34th-americas-cup/ says that the cost of an America's Cup sailboat challenge is about$200 million.

But to win your competition, you don't need the world's most efficient car. You need one only slightly better than the 2nd place competitor. That is challenging.

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#### berkeman

Mentor
We're going to design a car that's very similar to the normal ones actually I can say it will be a "real" car. The race inspectors are going to examine the car in terms of security as well, if they don't find it reliable we'll be disqualificated. So, almost everything that exist in regular car chassis should exists in our car (chassis legs, roll bars etc.)
Which brings up an important question -- Are people going to actually drive around in this car? At what speeds? If the chassis fails while it is being driven, what are the risks to the driver and nearby pedestrians?

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#### mastermechanic

I didn't find much on cost. But I did see a lot of carbon fiber DIY videos on Youtube.

I believe that commercial cars use carbon fibers plus other materials in their frames. Of course the best guess for other materials is steel. But how much steel and where are open questions.

Whoever builds it safely will have to do a full strength/stress/tortion/bending analysis first. I don't know how much you consider expensive, but I would not be surprised by $100K just for analysis and design. Of course you can skip some analysis by overbuilding it bigger and heavier than the absolute minimum. But that conflicts with your desire for minimum weight and maximum efficiency. You must think about that carefully because you may reach the point where and additional 10% decrease in weight costs 1000% more. In other words, expect a cost-efficiency curve to look like this. View attachment 222053 A car is smaller than a boat, but more complex. This link http://www.sailingscuttlebutt.com/2013/09/26/cost-compete-34th-americas-cup/ says that the cost of an America's Cup sailboat challenge is about$200 million.

But to win your competition, you don't need the world's most efficient car. You need one only slightly better than the 2nd place competitor. That is challenging.

#### CWatters

Homework Helper
Gold Member
On Alibaba you can find the price per ton for steel and lower quantities of carbon. I think carbon is about four times the price but that doesn't include resin or labor needed to do the lay-up. Autoclave time?

#### gleem

In marine construction the special process is vacuum bagging the laminate.

#### 256bits

Gold Member
So, institution wants us to design a car which has high producibility, efficiency, performance and esthetic. Probably these are preparations of a mass-production of domestic car
Is that a guess what they desire, or your interpretation.
Concept vehicles provide a gateway for some options that may or may not be incorporated into mass production, sometimes many years after the fact.
What is designed and thought of by the team as the greatest, may be shrugged off by the buying public as undesirable, or the manufacturer.
Really no way to know.

Example - side mirrors, at higher speeds they produce air drag , what % I do not know, but that drag from a protrusion could be eliminated to a major extent by using rear facing cameras and video feed into the interior of the car. Why do not all cars have that? Is it because the public does not find that as an appealing gadget amongst all the others they are bombarded with? Do manufacturers find the addition ineffective on the retail price and sales? Would it mean a car doesn't look like a car anymore without mirrors and "someone" has decided that way? Perhaps it is that present transport laws dictate that side mirrors are mandatory on all production cars? Whose to know?

#### mastermechanic

Is that a guess what they desire, or your interpretation.

Example - side mirrors, at higher speeds they produce air drag , what % I do not know, but that drag from a protrusion could be eliminated to a major extent by using rear facing cameras and video feed into the interior of the car. Why do not all cars have that? Is it because the public does not find that as an appealing gadget amongst all the others they are bombarded with? Do manufacturers find the addition ineffective on the retail price and sales? Would it mean a car doesn't look like a car anymore without mirrors and "someone" has decided that way? Perhaps it is that present transport laws dictate that side mirrors are mandatory on all production cars? Whose to know?
Yeah you're right, electronic side mirrors has been started to be used in some car brands. It was a interpretation but in the competition booklet it says "
Visual Design Award /// This award will be given to the team whose vehicle’s external and internal design (shell, cockpit etc.) is original and aesthetically pleasing. The award also considers the designs industrial producibility and usability." So I think, doing something like Tesla has much more advantage then doing like streamlined design. It's should have also a muscular body and sportive lines like today's cars.

Mentor

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#### mastermechanic

Have you looked at current-day concept cars for ideas? Like the concept cars shown at the major auto shows...

https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2013/8-hybridsconce.jpg
View attachment 222181
Yes, I've still looking at for some reference. I have a concern about how to model my sketches because even though I reach a final design on paper I have to model it so that it can be manufactured with metal or plastic sheets. How can I model that curves on the body?

#### Sherwood Botsford

If the ability to manufacture in bulk is important, then skip carbon fibre. You don't save enough weight to be worth the cost.

In addition, working with fiberglass and resin layups is standard technology. Carbon fiber is still pretty high tech.

Safety is a concern. First of all, a lighter weight vehicle will subject the occupants to larger accelerations in a collision. Modern cars are designed with crumple zones that absorb energy in a collision. You have to absorb more energy and do it with less mass.

#### gleem

In addition, working with fiberglass and resin layups is standard technology. Carbon fiber is still pretty high tech
Actually the techniques for laying up carbon fiber, fiberglass or Kevlar are the same Lots of video to show this.

#### Tom Kunich

Wow! Actually I didn't expect that much (\$100K). That would be impossible for us to afford this even though we're in search of sponsorship. But I agree with you, I imagine that the cost will increase with the efficiency desire. Since the chassis is the critical part for car in terms of weight, I'm responsible for it. I should keep it light and safe. Probably, Aluminum (or maybe steel) is the best choice.
I have had carbon fiber components fail. I don't believe you will find CF in the frame or suspension components of a car but rather non-structural areas to reduce weight. And you can probably use aircraft grade aluminum more effectively and a great deal cheaper. And a whole hell of a lot less likely to fail. The strength of CF components relies a great deal on the strength of the resin holding it together. Over catalyzed resin or older structures can fail as the resin slowly ages and becomes increasingly brittle. I have had endless arguments with people who believe that CF is the future. But I am also permanently injured from failures from the best manufacturers.

#### Sherwood Botsford

Actually the techniques for laying up carbon fiber, fiberglass or Kevlar are the same Lots of video to show this.
Yes and no. Cutting the cloth is different. Because of CF stiffness you have to pay more attention to ply orientation. Different resins. Almost always using vacuum bag techniques. For making dog sleds, not much different. For making airplane wings, a lot different.

"The cost of a carbon fiber car chassis"

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