![]() |
pic: Rastogi 8wd Iteration 1.2
|
Re: pic: Rastogi 8wd Iteration 1.2
Looks great. If I didn't know better, I'd think you had built it already and this was a picture of it.
|
Re: pic: Rastogi 8wd Iteration 1.2
Looks great!!!
I have couple of questions for you:... Does the 4 outer wheels raised? If the wheels are raised why not going for 8WD instead of 4WD? Why did you decide to use 4 dual-nano (have no idea what it is but i figured it is a gearbox) instead of 2 gearboxes and using chain/belt to convert the power? might save some weight over there. I don't know much about sheet-metal drive-train but wouldn't it be wiser to bent the sheet-metal towards the robot instead outwards? My opinion is that it will be much safer, more easy to work with, and stronger. But as i said, i don't know much about sheet-metal drive-train, so i also want to hear an expert on that question... Thank you |
Re: pic: Rastogi 8wd Iteration 1.2
Why are the hex shafts so long? Just curious, I'm sure its just something you haven't gotten to yet.
Looks good. Designing in sheet metal is a very good thing to learn if your planning on becoming a mechanical engineer of some sorts. I cannot tell you how many sheet metal parts I've designed for my various jobs I've had. It comes in handy for other parts too that aren't necessarily made of "metal" (ie: polycarb, other such plastics) which may be created using the same techniques as standard sheet metal parts. Also very handy with sheet metal are PEM fasteners. If you can master their usage, you can create really sleek sheet metal designs. Have you done any FEA on the frame? Its sometimes difficult to gauge the "strength" of a design from sheet metal, especially when first starting to design in sheet. My only comment would be to add a cross member lower on the frame to add another axis of stability, however it may be unnecessary, thats what analysis is for! Brando |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
With little experience designing sheet metal chassis, I will share my opinions anway.
1. Any reason for folding out instead of in? Without that pesky bolt heads frame perimeter rule, there should be no reason to cover the bolt heads. 2. What material is the dead axle? I assume a 3/8" pipe, taped at the end, with a bolt holding it in. 3. Again, why the dual-nano? 3a. You could alternatively make the distance between the two side plates exactly the width of an AM Shifter, then put an AM Shifter inside (with the chassis sides as the side plates). Or, you could just use an SuperShifter or Toughbox as you do now, with a live axle, then chain the other side. 4. Why the bump-climbing notch? Assuming there is less terrain then this game... 5. I like the render. Looks very real. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Quote:
Quote:
Quote:
Quote:
Quote:
Thanks for the questions. More suggestions and advice are welcome and appreciated. :) |
Re: pic: Rastogi 8wd Iteration 1.2
edit: akash is a ninja delete plz
|
Re: pic: Rastogi 8wd Iteration 1.2
I would say you're fine for powering from four separate locations as opposed to one central spot on each side. If it shortens the chain runs and makes maintenance easier, it's a good trade-off.
I can't see the stress tests for this, but as a typical rule of design you want the most support in the middle, as that's where it'll break first. I would take out some of the pocketing in the middle, it'll likely only add fractions of a pound anyway. Overall it looks great though. Your rendering and designing skills have gotten really good, great job. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
*hint - Akash, PEM nuts are good - hint* ;) Looks really good, though. Really imposing. Keep it up! |
Re: pic: Rastogi 8wd Iteration 1.2
I'm of the opinion it would be faster to stress test a prototype then it would be to run complete and thorough FEAs on stuff like this anyway. We should just build one. :)
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Something I've noticed, only because we ran into the same problem this year, is that you have effectively created a giant piece of C-channel. Moving those cross-braces down to form an I-beam shape or adding ones near the bottom should strengthen the design a bit. Just some thoughts, but I like where this is heading.
. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Also what I think with the flanges facing inward towards each other means you would have to design enough space for your chain/belt to run depending on your configuration. Which means you might have less space elsewhere for another mechanism or something like that. BTW very nice render It has inspired me to get finished with my school work faster so i can finally get around to designing my own sheet metal drive train! |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Ah thanks for the insight Andrew. You might also like this. :D I tried to copy it from one of the pictures that was posted of your 2010 bot. ![]() |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Whenever possible, I like to add threads to a part (tapping or threaded insert) rather than using a nut. One less piece to worry about, one less piece to come loose, one less point you have to reach for assembly/maintenance. Plus installation and removal now only takes one hand! :) But Andrew's 100% right about this: Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Nice Render,
Slightly curious what's the weight? -RC |
Re: pic: Rastogi 8wd Iteration 1.2
Looking good.
Also, I'll second (third?) the recommendation for using PEM nuts. We use them at my work on our sheet metal chassis, and they're wonderful to deal with. Out of 75 robots, we had one PEM nut pop loose, and the shop that pressed them fixed it for us in less than 6 hours. PEM nuts are the way to go. How many parts in there are standardized? It's always easier for a sheet metal shop to punch out and break more similar parts than differing ones. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
There are only 3 different parts here. All sideplates at the same, all cross members are the same, and brackets in between plates are the same. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Why not connect the two side assemblies along the bottom?
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Second, you might consider putting flanges on some of those inside cutouts. Yes, it ends up a little heavier, but because the outer flange is not continuous you will suffer from low rigidity (and low resistance to bending) at certain points; use flanges to compensate. Akash, when you're doing your analysis, be sure to model loading from another robot hitting you from the side at several locations. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Could you, or anyone else, elaborate on what types of places flanges can be made on a part like this? I wanted to add flanges on some of the inside pockets but wasn't sure if that was easily possible. Like I said, I'm looking to learn about this as much as possible. :) Thanks. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
And, Quote:
Thanks! |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
I'm not an experienced sheet metal designer, but what CAD program is that in?
Thaine |
Re: pic: Rastogi 8wd Iteration 1.2
I would add in some triangulation in the x-y plane. Other than that I think it looks solid.
What material were you planning on making it out of? |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Sheet Metal is usually 5052, John or Art can confirm that (or anyone with sheet metal knowledge). 6061 just isn't that great for bending. Btw how much does this DT weigh? -RC |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
(edit: Just checked the BOM at work... Turns out I was a digit off. Whooops.) |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
KOP stuff is 5052 from AM (iirc), our other sheet metal parts were also 5052. 6061 likes to crack when it's bent parallel to the grain structure. I have also done sheet metal work with 3003 and 1100, which are very easy to bend, but weaker than 50xx aluminums.
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
5052 is the stuff for bending, as most of you have stated. Whatever sheet metal house is helping you guys out will tell you the same thing. -Brando |
Re: pic: Rastogi 8wd Iteration 1.2
Just a question: Is a sheet metal chassis lighter than an 8020 or 1/16 aluminum square tubing chassis?
Also, is there any sort of guide on building a sheet metal chassis? |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
As for the tube chassis, I would think that a welded 1/16" aluminum tube chassis would probably be lighter as well as a bit easier to manufacture than a sheet metal frame. Sheet metal is nice if you have the resources and if you understand how to design to its strengths, but I dont see it as the miracle construction method that a lot of people on CD seem to see it as. |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
Thaine |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
... in theory. :) |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
For inexperienced and novice designers, chassis construction methods are far less important than actual design skills and features included.
You'll see crappy extuded tubing drives alongside crappy sheetmetal drives alongside great forms of both. Buuuuut, after a few years you come to realize nothing beats good 'ol 2x1:rolleyes: |
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
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
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
Quote:
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
![]() These parts could probably be replaced by a piece like this ![]() The parts you have, difficult to assemble/disassemble and probably have less strength since they're putting tensile force on the fastener (and onto the flange). The replacement part above puts sheer force onto fastener and your largest flange face. ![]() All these parts each have four flanges each and could probably be replaced by a simple plate similar to this. ![]() This piece is a lot more simple and uses the existing flanges on the big side chassis pieces, removing redundancy. Sorry if this seems kinda scrap together, I'm writing this pretty quickly because I have quite a bit of schoolwork to still do. :) |
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
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
Quote:
|
Re: pic: Rastogi 8wd Iteration 1.2
Quote:
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
Quote:
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.
|
| All times are GMT -5. The time now is 06:03. |
Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi