After Cornering Tesla, BMW Is Going For The Kill

No, aluminum alloys return to the T0 temper with welding. And, alloys in the 2024 and 7075 series develop migration in the alloying copper and zinc crystalline components making them very susceptible to stress corrosion cracking. Failure rates are very high.

Steel spot welds, if done properly, will hold together and allow the substrate to tear before coming apart. Since many spot welds are easily and cheaply made with NO added weight, adhesive is not necessary. Seam sealant is used only for environmental sealing at the edges.

There is NO magic to carbon fiber.

The Achilles' heel to carbon fiber is the ground mass. It is plastic. It has the same UV resistance and impact resistance as the plastic alone. Epoxies degrade with temperature changes over time and UV light. Powder coating are epoxies and degrade bad in UV exposure. Not as strong is polyester. Just think of your basic water or soda bottle.

The most durable plastics are POM or polyoxymethylene. Basically, it is the 1950's improved incarnation of Bakelite. It is strong and stable in itself. Many mechanical components in cars use this premium plastic under the hood. It is a standard for tooling in car assembly lines and other industrial processes. Nylon plastic gears are NOT nylon, which is too flexible and absorbs too much moisture. They are made of POM.

 

I had not heard the term 'ground mass' before. Just epoxy.

Are the prepeg fibers that are heat cured less subject to UV degredation?

I need to build an engine mount and was thinking Kevlar because of the vibration stresses along with a more flexible matrix/epoxy. The idea being to avoid the difficult to identify cracking/breaking modes and delamination risks. Kevlar has good high temp characteristics and I am seeing ads for high temp epoxies.

I am curious about JB Weld that appears to have good high temp and reasonable mechanical strength. I have not heard of or seen UL exposure warnings.

On the engine mount, I was thinking the engine mount hard points would be a dense wood thimble or aluminum and use honeycomb for the rest of the volume. Yes I understand the problem of drilling Kevlar.

Bob Wilson

 

With Audi and BMW with a Toyota partnership, Ford has also be looking into carbon fiber, or more technically correct carbon fiber reinforced plastic(CFRP) for a couple years now.
Ford Driving Hard Into Carbon Fiber - CleanMPG Forums
"The 2,600 pound Hyperlight Ford Fusion Concept applied aluminum, high-strength steel, magnesium, composites and carbon fiber to nearly every vehicle system to reduce the car’s weight to that of a Fiesta – a near 25 percent reduction. Insights from this concept will be a catalyst for lightweighting technologies in future automotive production."

We may not see them in mainstream cars soon, but increasing CAFE targets means the auto makers have to look at everything to reach them.

 

"Ground mass" is an ancient geological term from centuries ago referring to naturally occurring to matrixes of materials including conglomerates and breccias. It is a term used a century or more ago, when Leo Baekeland developed the first artificial plastic that he trademarked "bakelite."

A better. stronger and longer lasting engine mount can be made from 4130 chrome moly tubing brazed with a silver bronze rod or welded with Tig.

That processes has been used for the fuselage frames of the WWI Fokkers and current bicycle frames.

Epoxies have very poor UV resistance. That's why exposed carbon fiber panels use polyester fiberglass resin. Carbon black powder has been used to add UV resistance to plastics since the advent of plastics used in sunlight exposure. Titanium dioxide or white pigment is used for white plastics. It is the basic pigment for white paint. Red plastics fade very badly in sunlight.

The red, white and blue nylon and polyester flags left on the moon by the Apollo astronauts are most likely bleached white or crumbled to dust.

 

+1

Yes, absolutely. Its cheaper to weld steel than to epoxy and rivet aluminum, although since the rivet/epoxy bonds are stronger it requires less points for the same strength. Alcoa and Ford did a lot of work to make the process cheaper and faster for the F150 though, and I would think this manufacturing technology would trickle to other makers. Alcoa has the recycling side down.

I don't understand this statement. Carbon Fiber reinforced polymer composites (CFRP) are much stronger and more stable than your plastic water or soda bottle. Have you ever worked with it?
Carbon Fiber Reinforced Polymer Composites [SubsTech]

Umm. gee I'm glad you didn't choose material for my bike fork, or for the bmw i series.

Besides CFRP weighing less and providing better safety cages, the i3 is 95% recyclable. Lots of advantages to CFRP, the problem is both the cost and repairability. To help reduce rapair costs the ford F150 uses steel on its frame, and the i3 uses aluminum for its frame. You damage a structural piece of CFRP you need to replace it. If bmw and audi can drop the price greatly we will see a lot more CFRP in cars and other vehicles. Hoods, Roofs, Dashboards, and trunk lids are great applications.

 

[QUOTE="austingreen, post: 2141713, member: 58508]
I don't understand this statement. Carbon Fiber reinforced polymer composites (CFRP) are much stronger and more stable than your plastic water or soda bottle. Have you ever worked with it?
Carbon Fiber Reinforced Polymer Composites [SubsTech] [/QUOTE]

Mechanically stronger? Yes...

Chemical, heat, UV and other characterizes are no different than the plastic matrix or ground mass alone.

 

wonder what Bugatti was thinking . . . .

 

I have no idea about chemical but this should be different, but CFRP is more corrosion resistant from the common elements spilled on it in a vehicle.. Of course heat and UV are dre different than common soda bottle plastic. I don't understand what "ground mass" is about in a composite material. A composite is going to have different characterisitcs than the individual elements.

Again problem is cost and the way it breaks. Otherwise CFRP is much botter for cars, planes, or bicycles than steel or aluminum.. Look at some specific CFRP's for these properties. It is not the same as the fibers alone or the polymers.

 

PET or polyethylene terephthalate or polyester plastic is a very durable and UV resistant material.

It is commonly known as Dacron and Mylar.

Again, you equate your personal experience of the material in the thin pressure vessel, film and fabric form.

Thicker "filled" polyester is one of the most durable plastics or polymers available. Ground mass is the material that glues and holds the fibers together, like fiberglass resin holds fiberglass together.

While the composite have different characteristics than the components, the environmental exposure layer is still the basic plastic. It has the same temperature, chemical or heat resistance as the component alone.

Steel will still be the mainstay of automobile construction for years to come. I've seen so many plastic come and go. That includes the Pontiac Fierro, the BMW Z1 sports car, the original Saturn, et al.

 

You seem to be spouting a personal opinion that differs greatly from my real world experience with CFRP. Again there are many types, and the heat and corrosion properties are fine for cars. You act as if they are going to melt in a car, when CFRP has been used near high performance engines for a long time. If CFRP was so fragile why would porche use it for the engine support cage in the money is no object 918. The answer is it can put up with hot engines, spilled oil, and gas, with no problems at all, while providing the flexibility and strength and low thermal expansion the porsche engineers wanted. This allowed porsche to use simple rubber mounts, instead of the hydraulic mounts in the 911.

As to your point composites have different melting points than their components that went into manufacture. As long as the melting point and corrosion resistance are proper for the application who cares that you think its not good as steel. For most applications it is much better for an engineering point of view other than as I keep repeating price and repair. If you reduce price...

Again this is not the plastic of pontiac or the ev1. These are advanced materials. Steel is still king on cars because of low cost for manufacturing and repairing. As cars attempt to become more efficient, materials become more important. For example tesla now has a new replacement tire for its roadster 3.0 that reduces rolling resistance by 20%. Tires should continue to improve but at a slow pace. The porsche 911 has been one of the models resistant to leaving steel behinc, but if I remember correctly its body is 55% steel and 45% aluminum. The F150 is the highest volume vehicle in the US, and it has gone aluminum body on steel frame. Certainly CFRP is better than steel or aluminum in many parts. If manufacturers can push the price of CFRP down further it will be used more and more on cars.

 

I am using a Hirth 3502, a liquid cooled, oil-injected, fuel-injected, two-stroke with electrically, inflight adjustable prop for 'torque' loading the two stroke. The bottom of the engine mount is the top of the diffusion duct to the radiator. The variable chin scoop descends down.

At ~112 lbs, it replaces the converted VW engine, 172 lbs. A steel tube mount is traditional but the duct work become a nightmare. Think "firewall" forward, integrated power plant.

Because we won't know the final weight and CG until ground testing, I am planning on a steel-tube 'shim' so we can adjust along the linear axis.

Bob Wilson

 

At 9:00 Easter tine, tonight, the Science Chanel's How It's Made Dream Cars will feature the assembly of the BMW I8.

 

Lexus has manufactured its own Carbon Fiber loom specifically for their LFA supercar - & you can watch it now;

It's quite time saver, compared to hand laying the material
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The i8 MSRP starts at $136.6K. That's about double the cost of the entry level Model S. Definitely a lot of dough for a 3 banger, with only a 20 mile EV range. i8 is quite the looker . . . but I seriously doubt it's got Tesla 'cornered'. And of course, who wouldn't rather buy domestic vs import.
.

 

From what I see. the I8 uses a pretty much conventional frame welded from standard "box beam" sections.

Carbon fibre is mostly used in the passenger compartment module, while the rear fenders are moulded plastic panels.

So, it is NOT that much unconventional as BMW has lead us to believe.

 

BMW didn't lead us to believe the use of the carbon fiber was unconventional in the i3 or i8. It forms the passenger compartment, with some aluminum stiffeners, and body panels, which is mated to an aluminum frame.

What they did in the i3's case was to use so much of it in a car well below $100k. The new Corvette uses less of the stuff and is still over $10k more starting. BMW's and others' goal isn't to use CFRP differently than it is used in super and race cars, but to get the production and repair costs down to the point where it can be used in all cars. That may take awhile to reach the Sonics and Yarii of the car world, but it may not be that far off for the reasonably prices Lexus and Buicks.

A few years ago now, Toyota and BMW announced a partnership. The headlines where about Toyota sharing their fuel cell technology. What got buried in the articles was that they were getting access to BMW's carbon fiber tech. It may actually be BMW's loom up there making the LFA, and also the hydrogen fuel tanks for the Mirai.

Here is an article on repairing the i3: Crash your carbon-fiber i3 EV? Here's how BMW will fix it - CNET
The BMW spokes person says the repair cost will be comparable to a traditional car, which I take to mean a BMW fixed at a dealer. Compared to aluminum and high strength steel, though, the investment for a body shop in terms of tools and equipment will be less with carbon fiber.

 

Yep you are seeing it right. The i8 is much less expensive than the 918, and it is a beutiful car. The 918 did the innovation when it came to phev CFRP sports car. The i8 is trying to be an eco 911, and if it can drop the price it has a good chance.
Compare Side-by-Side
Note 15 miles of ev blended mode, then it does as well as a camry, in a car that can hit 60 in around 4 seconds. The only thing not to love is the price. If bmw can continue to lower the price of CFRP they probably can take over from the 911 as the iconic sports car that people can actually drive to work. Still not that many 911s are sold. This will always be a niche market.

The i3 leverages a gm design. Again the innovation is in reducing the cost of the cfrp. Both cars hit a price point not seen before for what they are. 10 years out we may be seeing a lot more fiber, but like in the 911, there will always be some parts that are better made out of steel, others better made out of aluminum.

 

The person who wrote the original article seems to have been ignorant or very ill informed.

Tesla will beat BMW on the matter of a BEV every way 'til Sunday.

If the Chevrolet Bolt delivers on it's hype, thy will be the real competition for Tesla.

 

+1

Yes, absolutely. BMW really is concentrating on PHEVs and CFRP. Tesla is concentrating on BEVs only. The two compete with sports sedan, luxury SUV, and sports car market. These overwhelmingly belong to the german manufacturers. Adding plugs to these cars may expand the market, and the question is will bmw's phevs be good enough for it not to lose major market share to tesla. That all depends on future cars, but the i3 looks like a hit on the low end, the model S a far bigger hit on the high end.

I don't think the bolt will compete directly with the model 3, let alone the other tesla models. The model 3 is rying to take market share from bmw 3, audi 4, mercedes c class, lexus is. The bolt looks like a much lower volume model, going after the compact hatch market. Sure some will buy it simply because its a bev and has enough range, but ... that is much smaller segment than the one the model 3 is going to compete.[/quote][/QUOTE]

 

I do think there will be some competition between the Model 3 and Bolt.
We are still early in the EV adoption. A few years ago there were some customers cross shopping a Tesla Roadster and a Leaf
The Model 3 and Bolt will be very close in price and range (if both reach the announced goals). If GM gets the Bolt to market first, I do believe they will take a little business away from Tesla.

 

The 3 series is a compact. Presumably the model 3 will be a similar size, but a frunk could push it into the EPA mid-size category.
The Sonic is seen as a sub-compact, but the cargo space of the hatch puts it in the mid-size class. The chances of the new platform shrinking or going xB are slim. So the Bolt will be about the same size with maybe a little more cabin space due to the need of a smaller engine bay.

Being meant for the higher end market, and the rep of the Model S, I see the Model 3 pulling in some luxury ICE buyers. Among current EV buyers, I don't think luxury appointments and features are has important. So they'll likely opt for the Bolt unless the Model 3 has a more comfortable cabin.

The Model S got EV buyers because of the range. Those that couldn't afford it and are waiting for the Model 3 will likely go for the Bolt.