I went to the Maker Faire Bay Area over the weekend, and gave a talk about composites and my book – “The String and Glue of our World – Understanding Composite Materials” on the Make Demo stage for about 50 people.It was an awesome and humbling experience, and I had a lot of fun doing it, so I wanted all of my readers to know about it.So, Maker Faire Bay Area is going to be the subject of my post this week.
This is John – a student at Berkeley who was involved in making this thing. It is a flying six propellor creation put together by the Berkeley student UAV club. And it is nearly 80% by weight carbon fiber composite so I thought that since this is a newsletter about composites this would be a good lead off pic. If you look closely, the Berkeley students didn’t use a traditional approach to doing this like making molds and hand laying in pre-preg. Instead, what they did was buy off the shelf composite structural sheets and tubing, as well as carbon fiber composite propellors, to put together the main structural components of this UAV. This club at Berkeley (UAVs@Berkeley) provides students with an opportunity to get out of their comfort zone to design and build racing UAVs like the hexacopter in the pic above that are capable of traveling as much as 10 miles and can carry 5 pounds of water bottles that they can drop on targets on sanctioned race courses.
Since this is a newsletter about composites, I wanted to talk a little bit about the conversation I had with John – the Berkeley student in the pic with the hexacopter. When I asked John to permit me to take his picture at the hexacopter, I had to tell him why – because I wanted to make it the lead image in this newsletter. And I want to thank John personally for permitting me to put his picture in my newsletter.
Anyway, that got us to talking about why I wanted his picture, so I also told him that I was going to be giving a talk about composites and signing my books. And, while John is not an engineer, he did let me know that they were dealing with a harmonic in the structure and asked me if I knew of a way to use composites to make parts of the copter lighter weight than they already are, but stiffer in the direction that they are having the harmonic vibration. Basically, the propellor support arms or spars are bouncing up and down at a frequency that is excited by the propellors.
The problem that they are dealing with is that the carbon fiber tubes that they used to mount the electric motors on with their propellors are not stiff enough in the up and down direction, so when the copter lifts off or tries to change direction it sets up an up and down vibration that is taking away from their performance. Here’s a pic of what I’m talking about.
This carbon fiber tubing they used is available on line, so that is where the students got it. But, since it is an off-the-shelf material and product form, it doesn’t take into account the entire set of requirements for being a spar supporting the electric motors and propellors for their hexacopter. Nor does it fully use the properties of carbon fiber composites. Part of the tube is just wasted weight. What they need is not the same stiffness in all directions – which is what they have now. What they need, and what I told John was that they needed more stiffness in the up and down direction. In other words, they needed to make new motor spars using more of the real benefits of composites.
What I suggested is that the supports should first not be circular in cross section, but should be oval – making higher stiffness in one direction like up-down than the direction perpendicular to that one or left-right. And then to tailor the up-down vibration frequency, they could add some unidirectional tape on the top and bottom of the oval to give it even more stiffness in the up-down direction than just making the spar out of fabric formed into an oval shape. And, once they figure that out, they can tailor the stiffness to a frequency that is not excited by the propellors. And this solution may even be slightly lighter weight than what they have now – which is also one of their goals.
I’m sure that if John talks to some of the engineering students in the UAV club about this they will know what he’s talking about and should be able to figure out what the layup should be for their “standard” propellor support spar. And I gave him a business card so they can contact me for advice if they need to do so. So, if there are any engineering student in the Berkeley UAV club, please contact me and we can talk about how you can make your hexacopter better.
This is just an example of the really cool things that you can see at Maker Faire Bay Area. There is of course lots more there, and if you live close to the Bay Area and can get to Mare Island this coming weekend, I would strongly suggest that anyone interested in making anything go to the Faire. The website for the Faire if you want to take a look is https://makerfaire.com/bay-area/. Student day is Friday, and the remainder of the Faire is open to the general public to see all of the wonderful creations of the Makers on Saturday and Sunday this week.
I wanted to share a couple of other pictures that we took at the Maker Faire with you so that you get an idea of some of the crazy stuff that you will see there. And there are even some things made using composites there that I have in these pics.
Yes, that pic in the upper right is Adam Savage of MythBusters on the stage talking to the crowd on Sunday morning. And there are the crazy cupcakes that motored around all over the grounds, a fierce looking battle bot that looks like it has a composite top, and a bunch of helmets and one still in its fiberglass mold. Pretty amazing stuff to see that people have made in their bedrooms, garages, and workshops depending on how big their creation is and what it is made of.
That’s about enough for this week. I am going to be reminding everyone right here each week that I will be presenting two papers toward the end of this year. Both of them are about sustainability of composites – a subject that all of you that have read my posts know is a passion of mine. The first one is a paper about sustainability efforts for composites in general, with a focus on what to do with wind turbine blades. That one is going to be at the International Mechanical Engineering Congress and Exhibition in New Orleans October 29 to November 2 (https://event.asme.org/IMECE). The second one will be at the Carbon Fiber Conference in Salt Lake City being put on by Composites World (https://www.carbonfiberevent.com/). In that presentation I will focus on current work in sustainability of carbon fiber in particular. I’m of course going to talk about new fibers and fiber precursors made from plants, so again, focusing on closing the circle.
And, finally, for those of you that have not heard, my book has been published and is for sale. The best place to get one is to go to my website and buy one. I will send you a signed copy for the same price you would get charged on Amazon, except that I charge $8 shipping. Anyway, here’s the link to get your signed copy: https://www.nedpatton.com/product-page/the-string-and-glue-of-our-world-signed-copy. And as usual, here’s a picture of the book, for those of you just tuning in.
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