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#1
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Re: Carbon Fiber
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Also correction to my above post it was the 777 which was the first composite tail aircraft. And the reasons for the weight are as Tristan said, however do to the impacts from a FIRST game I too would tend to use thicker layups. Also just for the fun of it a video of CF failure testing: http://cervelo.tv/ Launch the player and watch "A crushing blow" |
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#2
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Re: Carbon Fiber
I strongly believe that composite construction has a place in First robotics and I have introduced them to our team and we have had great success with them. However, getting back to the original post I'm ready to throw out the red flag and cry foul. A team that has access to high grade materials, fabrication facilities and design resource can gain an advantage over other teams. These are resources that the rest of us can not acquire at any cost. Going forward I think composites need a close look by First to determine what is allowed based on availability to all teams and the cost issue. Aerospace composite manufactures have access to types of prepegs,cloth and resins that an individual team cannot get. Their performance specs are an order of magnitude better than what can be achieved with hand lay up and materials that could be acquired by any team. As to the valuation of materials , to account for 5 yards of cloth or prepeg at 1000yd price for 5 yards would be wrong as other teams could not receive that price if they could purchase the material in cut roll pricing at all. Then the subject of tooling,molds and set up and clean up cost needs to be looked at. There are many types of composite materials that are available of the shelf. Dry cloth, room temperature cure epoxy resins, FRP and vinyl ester pultrusions, composite tubes and rods, g10 11 and 12 sheets are all available off the shelf from many manufactures and distributors and should be allowed. These issues are not the same as a team water jetting a panel vs. a team cutting the panel by hand.
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#3
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Re: Carbon Fiber
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#4
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Re: Carbon Fiber
Cory made me go look it up, so there is no misunderstanding (quoted below).
I think we should create a counter that increments once each time the issue of "FIRST is a Competition vs FIRST is here to inspire students" comes up during the year. It is absolutely true that a team with a large company with many engineers and lots of expensive equipment will be able to design and build a state of the art robot, that a HS-only team with nothing but hand tools could never possibly duplicate. But we are here to show HS students all the incredible things that can be done with technology and state of the art engineering. If Lockheed-Martin is your sponsor, then any work done by Lockheed-Martin employess is considered work done by the team. This is what we want the students on that team to experience, to be blown away when they see what a good engineer can do with $50 in materials and $1,000,000 of equipment at their disposal. Quote:
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#5
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Re: Carbon Fiber
My point is that for certain composite materials, most teams would not have access to them at all. This is especially true for preps. The overnight refrigerated shipping charges should also be included. I checked yesterday and I could find no vendors that would ship small quantity high grade carbon dry or prep. The materials should be available to all teams. If a sponsor does make a composite structure for a team then students should be involved from start to finish. This is hard for the good stuff because they are usually done in secure areas of the plant. First sponsors should not just bring a product to their team , but should bring the technology to the team. Over the years I've seen to many first mentors having second child hoods and forgetting the kids. Composite construction is prime for abuse and shutting the kids out. Look up the definition of mentor and let that be your guide. I feel a rant coming on so I'll stop now.
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#6
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Re: Carbon Fiber
Gdeaver - I agree with you on one level. There is a real Zen thing in engineering when its just you and a piece of metal with a vice and a file in hand, or a couple wrenches and a box of gears and hardware, or a bunch of wires and connectors and a soldering iron
I love that aspect of engineering when I need to do those things. But in my experience over the years I spend 99% of my time doing drawings, schematics, specifications, writing and conducting tests and its extreemly rare that I actually have to fabricate or assemble anything myself. I hand a drawing or send a file to someone else, and I get the fabricated part in a box a few days later. Most of the time, that is what engineers do. In my experience as a mentor I always make sure the students have some hands-on time with some aspect of the robot build and parts fabrication, esp at the events, in the pits. I also make sure they get a realistic experience of what its like to be an engineer, where the real value of what we do happens between our ears, not fabricating and assembling things with our hands. A good example is the capabilities of Gleason Works, the sponsor of team 578. They design and build the machines that make the gears used in most cars and trucks all over the world. They can literally hack a 1/2" slab off a one foot diameter steel 'log', put it in one of their machines, and fabricate a 12" diameter complex gear in less than 5 minutes. It would be a crime if the team was not able to use that capability for their robot. Its great to be able to work with a student to create a drawing or cad file, and hand it off to the guys who operate those machines, then have this beautiful shiney metal gear that rings like a bell an hour later. There are only a handfull of companies in the US that buy Gleasons $1M machines. Does that mean team 578 should not be able to utilize theirs? Last edited by KenWittlief : 19-10-2006 at 13:24. |
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#7
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Re: Carbon Fiber
Ken,
If on week 4 or 5 a box shows up with a fancy custom widget and there was no student involvement, that is wrong. If a core group of students sat in with the design process and then watched the tech do the set up and watch that custom widget being made and then sat with the QA person and validated it, That is good, real good. However, many times this is not the case. I did allot of the work on our composites, but I had some students there mixing epoxy and helping. While we were working I beat info and the whys into their brains. At our last meeting I had a student regurgitate that info back to me during a discussion with the new students. Thats the way it should work. Bring the Tech to the students. As to your other point, I'm on the other end. I install and repair the stuff you engineers design. Too often I am repairing or replacing parts that are poorly designed and many times it is very apparent that the designers have have little experience with the physical world. They live in the virtual world of their software. Hands on in First is a good way to help these future designers. I'm am not an engineer , I'm a reverse engineer. |
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#8
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Re: Carbon Fiber
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There are many avenues for inspiration. It is conceivable that this is one of them. Different methods work for different teams. |
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#9
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Re: Carbon Fiber
This is a really interesting topic (note to self: rate thread high).
Ken, in your 578 example above, I think the rules are clear: the gear made using Gleason's $1M machine is allowed because (1) the raw material is available to any team and it's cost won't cause the team to exceed the limit, and (2) Gleason is a recognized sponsor and its employees who fabricate the gear are considered team members. Just as clearly, a composite frame made from raw materials that are not available to all teams at a cost that fits the rules would not be allowed. As an analogy that fits my own team's situation: Emerson has two nice rapid prototyping machines that could be used to make parts for 931. The first is a laser cutter. My team makes good use of this because the sheet materials we cut, such as steel, acetal, and acrylic, are available to any team and not overly expensive. The other is a 3D Systems Viper SLA machine. This beauty can make parts that are similar to Nylon 6:6 in any shape we could dream up and CAD. But we don't use it. Why? Because the parts would not be legal for FRC. That is because the the raw material is SI40 resin, which is only available in 10kg containers that cost $2500 each. So there is practically no way the team could correctly account for the material cost, even though the actual quantities used would be small. Last edited by Richard Wallace : 19-10-2006 at 14:26. Reason: added link to resin data |
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#10
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Re: Carbon Fiber
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Go back and read the rules I quoted from FIRST. You only have to account for the amount of material you actually use, whether it comes in 1Qt cans, 55 gallon drums, or 20,000 gallon tanker railroad cars. My take on the availablity rule is to prevent a situation where some kids dad is a consultant, designs a custom transmission, and then 'sells' it to the team for $20 (when it cost him $2,000 to make). If he is willing to sell one for $20 he must be willing (and able) to sell 1000 for $20 each. Otherwise that team has a $2000 custom part on their robot, that was not fabricated by the team, and that $2000 must be included in the BOM total. If the SLA goop is commercially available, then its commercially available. How big of a container it comes in, or how hard it is to transport -those are engineering issues. If you have a company that uses that material then you must be able to handle it. Can 4 HS students buy SLA goop in a one quart can, and form parts using 3 laser pointers in a Pyrex measuring cup? No. Does that mean your team should not use it? No. Crank up that SLA machine this year - its one of the most awesome technologies on the face of this planet! If you can fabricate a complex plastic part with $5 worth the SLA goop, it doesnt get any more hi-tech than that. Last edited by KenWittlief : 19-10-2006 at 14:44. |
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#11
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Re: Carbon Fiber
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In the case of SI40 resin, the smallest commonly available unit is 10kg. When a smaller unit (e.g., one liter for $250) is commonly available, I'll gladly fire up the Viper to make parts for 931. |
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#12
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Re: Carbon Fiber
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If a company who sells the service of making rapid prototypes can give you a quote for making 1 piece for under $400, and that is the commercially-accepted price, then a team could make a custom part on one of these machines. For instance, I made our first plastic Omniwheel for AndyMark on a dimensions 3D printer that used ABS plastic as the material. The company who made this part for me charged me $250 for each side of the omni wheel. This cost covered their material usage, labor, and overhead costs. Anyone off the street could take a similar design, of similar size and get approximately the same price. As long as it's done during the build season, this would be legal, in my interpretation to the rules stated above. Andy B. |
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#13
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Re: Carbon Fiber
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I should start looking for a free-lance SLA operator that can fabricate with the same resin that Emerson uses, and is willing to quote parts. |
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#14
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Re: Carbon Fiber
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this is a very common issue with electronic parts. you can get the gyro sensors that many teams use from places like Digikey. If you buy one they are $50. If you buy 10 they are $45 each. If you buy a thousand they are $20 each. The rules are saying you cannot take adavantage 1 thousand quantity pricing and only charge $20 to your BOM, you have to use the lower quantity pricing if you only use one. But its still pro-rated by the amount (number) you actually use. If they only come in a box of ten for $450, and you only use one, then you only used $45 worth the parts on your robot. Last edited by KenWittlief : 19-10-2006 at 15:21. |
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#15
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Re: Carbon Fiber
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However, if a team buys an 8' long piece of aluminum tube and uses only 3', they can account for the price of a 3' piece instead as aluminum tube is commonly available at shorter lengths. Our team has an SLA machine on its way to the lab we borrow, so now I'm curious what sort it is and what material it uses to see if it'll be at all helpful to us. |
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