One of the last things Chris Bangle designed at BMW before he retired was the car you see above. It was a concept for a modular vehicle with a flexible skin that would literally change shape based on what you were using the car for. It’s trunk could change size and shape, and it could hunker down aerodynamically when it was time to go fast.
While obviously just a thought experiment, the flexible skin has me thinking about how to surface the Streetliner. Up to now, I’ve been planning to use foam and fiberglass to create the outer aerodynamic shell. However, looking at this concept and also remembering some fabric-shelled velomobiles I’ve seen online, the idea of using a more flexible material as an outer shell has a lot of appeal.
Firstly, it would greatly simplify construction. Since I’m not actually intending to mass-produce this vehicle, there’d be little point in investing the time or expense in creating a mold for a fiberglass body. Then there’s the added complexity of creating all the mounting points that join that body to the underlying chassis. Then there’s the added hassle of fabricating all the access panels and such needed to access key mechanicals under the body. I shouldn’t have to take the whole nose apart just to top off the radiator, for example. Furthermore, creating a fiberglass shell of adequate thickness so as to be good and sturdy would mean adding a not insignificant amount of weight to the vehicle.
Instead, if I were to build a series of essentially ribs over top of the chassis and safety cage, I could wrap the body in some sort of flexible skin. There are a number of durable thermoplastics I could use that would be resistant to weather, stones, bugs an the like out on the road, yet also be heat shrinkable and easy to patch and paint. Hell, you could use model airplane covering. The cloth-style covering is durable, paintable and very lightweight. Access panels could actually be pre-fabricated in framing, rather than having to be cut out of a hard shell. If designed correctly, the whole look would have a great antique aircraft look to it — like dope shrunk canvas over wooden ribs, spars and bulkheads.
Fundamentally, air doesn’t really care what a shape is made from. It just needs something to push against. Furthermore, an imperfect shape can still be very aerodynamic if it’s smooth enough. Further still, every pound of weight shed from the Streetliner is a pound I don’t have to push through the oncoming air. Additionally, I anticipate that building in this method would cost less, take less time, require fewer specialized tools and actually give me a much greater amount of flexibility to change the body shape as needed. Even the wheel pants could be made using this method — likely lessening unsprung weight and greatly simplifying installation. Anybody out there know of other examples of a flexible vehicle skin?
5 thoughts on “Rethinking the skin”
It has been a while since I’ve visited the site and I am very pleased to find you back at it again. You mentioned thermoplastics: Kydex is available in very large sheets and is much more durable that most craft thermoplastics. I have considered using it on the Cycle Kart project.
Cool. Thanks for the tip!
have you seen the electric streamliner on Youtube or on the web.He has a nice design with a door which is the way to go.The wheelbase is too short and since it is a concept,it is not totally to scale.I think if I was building one I would contact the designer of the Monotracer,or the guy who did C-1 of Lit Motors and Aptera[maybe the same guy]even the guy from streamliner electric might be a good call for a design to say raise money on kick starter, to pay a designer to work out a design,based on a few people’s idea’s.Call it Phase one or module 1,if you could raise enough money to take some ideas and put them into CAD/CAM,give away professional drawing’s or the files to build their own.If you can come up with design like the C-1 or BMW Simple concept design etc it should create a buzz allowing you to take it to Phase two,designing a chassis in Cad/Cam, and once the excitement builds and you can show the investors something really nice ,the money poor’s in, just keep raising money,get some people on board to slowly pull it all together.Rent a small building,start building up to some good shop tools etc.A good course in design,check out DP cars,he built a 4 wheel drive racer from solidworks and he documented the whole engineering project,it is a incredible source of knowledge.No amount of money can build anything without having people around you that know.The Monotracer,was built using tooling boards and MDF board as a filler[large body panels]they then cut the body shape to make the tooling ,mold for the Kevlar/Carbon composite body layup.Most people pay a outside company to do it,using kickstarter you could raise the kind of money it would take to do it right.My point is for you to do everything yourself and expect it to be something your proud of,it’s too much,you have to rely on some professionals.I have wanted to build a streamlined motorcycle for years,but to do it ,it has to be better and cheaper then the Monotracer and sell a lot more then a hundred units a year.I never would attempt it unless I was to do it right and that means finishing it,I would never quit.But like I said it’s too much for one person,I restored a few cars, built a few race cars ,but building a complete vehicle,you need some talent to fill in some of the holes.Even the Wright brother’s could have never built their airplane without the help of outside manufacturers,from whom they purchased the parts and materials,tools to build the aircraft.You need a business plan,get some numbers from other builder’s,who did the Cad/cam for the body and mold,how much[you want the molds too keep making body’s down the line,someone with layup experience could now build bodies from that mold at a later date.Same with the chassis,you want it build on a precision welding table[Bluco etc]then you could make fixtures if you wanted to make more,and so on.I could go on and on,but your a smart guy,I think you get it. Business plan,prices labor,parts to build one complete vehicle,if your serious and want to do it right then you need a good design and lots of money.Lit Motors raised about 800,000 dollars from outside investors.Their is a guy with a four wheeled leaning motorcycle under development,I think he is going to licence ,the technology,what is nice about it is the width is short,it would fit in a narrow aerodynamic shell,looking like it only has two wheels,but it leans both front and back,is very stable even with its short concept wheelbase.So much to think about and I can’t type,I’m far better talking,well good luck keep in touch.If you have a question I will try to find a answer.I have a name of the company that did the Monotracer glass work,so in the future if you can’t find it,I will look it up in my files]
Thing is though, this isn’t a project about starting up a company to build these en mass. This is about making one. Just one. And it’s especially about making it myself — it being my own design, my own skills and my own wits and judgement that make it happen. Sure, I’m going to draw on input from a number of different sources and contributors, but in the end, this is much more about skill acquisition and simply following through on a hare-brained idea.
I was posting comments from my smart phone earlier, but don’t see them here. Apologies if they’re elsewhere or in a queue.
My father worked on small aircraft. Heat-shrink fabric is stitched to the frame, shrunk tight like a drum, and sealed with “dope.” It’s good enough for planes…obviously there would be a need for protection in critical areas from rocks and road debris. Kevlar and epoxy?