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Re: pic: Rastogi 8wd Iteration 1.2
good work! i would put some wider cross bracings between the two pods, bend your flanges inwards and fiddle with your cheese holes a little. your lacking in some of the major stress areas and triangle departments. concept has some serious potential though. also if you run your cross braces to the outer plate of the drive pods they do a lot more for you.
take a good hard look at the slideshow in this :http://www.youtube.com/watch?v=_hTyXQUgYLE at how thier chassis is put together, pm or IM me if you wants some help with this. |
Re: pic: Rastogi 8wd Iteration 1.2
Thanks for all the new info
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Re: pic: Rastogi 8wd Iteration 1.2
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However, the .090" 5052 sheet Akash is using allows for much smaller bend radii (3/32", according to here). |
Re: pic: Rastogi 8wd Iteration 1.2
Try to get rid of all those spacer plates between the side plates by incorporating them into the inner side plate by bending the flanges in from the inner side plate. Might also think of building a low profile drive base and bolting on a frame with the robotic mechanism built on the frame. Doing so you can reuse the drive base design and build out a frame with the other parts for the robot.
Consider a bent sheet metal tray instead of the cross braces to connect the two sides together. As shown all the forces will be at the corners of your robot. It will be hard to square up and maintain a rigid frame with the cross braces. Take a look a some pictures of our 8 wheel drive sheet metal chassis. http://www.spartanrobotics.org/galle...Season&bac k= Roy |
Re: pic: Rastogi 8wd Iteration 1.2
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No matter where you go in the United States and Canada, there is a sheet metal shop within driving distance - often within bicycle distance. There you will find tooling of many types, and people with an awful lot of experience. Most will bend over backwards to help a high school kid learn about their business. So, here's the deal: Find a shop and visit them during the day sometime. Explain you're a high school kid, you are interested in engineering, and you are really interested in learning more about sheet metal. Like, for instance, how to bend flanges inside a cut sheet... I GUARANTEE that 98 times out of 100 you will get a wonderful education that day. If you're over 18, maybe even a summer job... Try it, see what happens, and let me know. Quote:
Don *Can't think much more than that... |
Re: pic: Rastogi 8wd Iteration 1.2
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As for the flanges, putting them on the inside is the way to go. I was working on a kicker guide plate this year that had roughly 300lbf concentrated in the center. The plate spanned 16 inches from side plate to side plate and didn't bend at all. The flanges not only put the material under the type of stress it is strongest in, but also increases the second moment of area. This is the same reason why I-beams are so strong and that you should move the cross supports down some. If at all possible, make the flanges continuious. Any gaps will concentrate the stresses in that area. FEA will be your friend in this endeavor, and I reccomend messing around with just a flanged strip of metal first with fixed constraints on the outermost sides. His will give you an idea of how much flanges help, as well as what happens when a flange is not continuious. If you can master sheet metal strengthening, your team will love you. |
Re: pic: Rastogi 8wd Iteration 1.2
Sheetmetal is generally 5052, it's able to be worked when cold.
1477 uses 5052. Edit: Also, make sure your fabricator has "sectionalized dies" you have some inner bends. |
Re: pic: Rastogi 8wd Iteration 1.2
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Re: pic: Rastogi 8wd Iteration 1.2
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Take a careful look at what sort of strength you actually need. Do you mind if a few small areas yield a little bit? It's probably okay if they do. Do you have a target stiffness for the chassis? If you make it out of .09" 5052 you can achieve the same strength, with lower stiffness, and half the weight, by making it out of 0.045" 7075-T6, if you can fit the required bend radii. Sure 7075 is more expensive, but the higher cost will be offset by using less of it. Making your frame half the weight has to be worth a decent chunk of money and is definitely worth considering IMHO. |
Re: pic: Rastogi 8wd Iteration 1.2
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If you have good suppliers and know where to look, small quantities (such as for personal project or a FRC team) of 6061 aluminum stock can be bought for as little as $1.50/lb. I bought a 15 pound bar of 6061 last year for about $25. I've also found 3/8" Hex bar made out of 2011 aluminum (easy to machine grade) for about $0.50/ft, which our team then promptly bought all 60 feet they had in stock for custom standoffs for the next few seasons. |
Re: pic: Rastogi 8wd Iteration 1.2
JamesCH95, thanks for the clarification. I mostly just work on designing and a little fabrication, so I'm not terribly familiar with the various grades of aluminum sheet metal. Whenever I need to machine something I just walk over and grab the stock needed from where I was told to :D.
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