Re: How to make your robot withstand the beating
 

Our chassis survived the year pretty much unscathed. We machined ours out of tube aluminum stock (which can be found on McMaster & local aluminum retailers). This provided rigidity, along with a place to safely put 2 Clippard Air Tanks & our drive train modules.

Re: How to make your robot withstand the beating
 

Build and experiment with different types of chassis and drive types (omni drive, swerve drive, tank drive, 6 wheeled etc...) and work out the problems that arise then when you got the time to fix them rather then during the build season. That way when you go to build the real one for that seasons robot you know how to assemble it. Usually it's pretty similar each year so you get good at it after a while. Summer is also a good time to use CAD programs to stress analyze where there are weaknesses so you can strengthen it up. Also, think triangles they are strong. Knowing when to use which type of nut and not leaving them laying around on the robot, it'll save you the panic later when one falls out and you don't know where it went. Cover Victors and Jaguars when working on robot, or use Talons, they can be a pain when they stop working and you have to take crucial time troubleshooting. Build simple east to fix mechanisms. This year not one thing broke on our robot because it was a simple dumper with 2 sides to hang, but still effective.

Re: How to make your robot withstand the beating
 

i understand what you want to do....you want to learn from the experiences of other teams. I think that is great, and this forum is the best place to do that.

But I also know that the best teacher is experience. I know a lot, most of it is learned from making my own mistakes, some of it from watching the mistakes that others have made. I still have so much more to learn, and I know that the only way I can learn it is to try, and keep learning as I make more mistakes, and have a few successes along the way.

At Championships this year we had a sort of major structural failure of our robot. I had anticipated this failure, and had thought of making a brace to prevent it, but never got around to it because the robot was working OK and we had plenty of other things to worry about. The competition here was really tough, and our drive team had to drive the robot really hard just to try to keep up. I also discussed this with several of our students, and they seem to have a good understanding of how important it is to try things, and see what works and what doesn't, and make sure to learn from the failures. Failure is the best teacher.

The trick is to figure out how to learn from from others' failures, or better yet, how to experience failures of your own in a way that do not really hurt, but teach you well. Many of the top teams spend many hours trying different ways to do things, and they test over and over until something breaks or jams or doesn't work right, then they change the design and test some more. It's called 'iterative design'. Having the will to keep working on something over and over is what seems to separate the best from the rest.

Another thing you can do is to post pictures of your design here on Chief Delphi, and ask for constructive criticism. I know that there are many very experienced people here who can probably spot potential problems quickly, if you provide enough detail for them to see what you are planning to build.

Re: How to make your robot withstand the beating
 

That butterfly drive is almost identical to our octocanum setup. Out of curiosity, what did you use for the traction wheel?

Re: How to make your robot withstand the beating
 

Our team always uses welded aluminum frames with very sturdy bumpers. These are great if you get into any collisions. We had several collisions during the course of the competition season that left us completely unscathed and other robots bent out of shape.

Re: How to make your robot withstand the beating
 

We put rough top on our custom designed traction wheel. It worked really well for us (and the other teams who chose to use it as well.

Re: How to make your robot withstand the beating
 

Thanks. We tried Colsons on our traction wheels, and were less than satisfied with their performance on carpet. (Alas, last year we had rough top on our traction wheels, and loved them on carpet but were less than satisfied on polycarbonate!)

Re: How to make your robot withstand the beating
 

Build within your means – not every team has machinists, welders, and the like with the capability to make parts, chassis, and manipulators with skill. Know your limits.

I'm going to echo others on this thread. Past failures are the best teachers.

Specifically, consider adding redundancy to the robot. Try to avoid designing in possible failures that would affect multiple subsystems on the robot. From a reliability standpoint, consider west coast drive.

Team 20 chose a six-wheel, dropped center west coast drive this year, saving us in WPI, during Finals 3. In our case, it let us continue to drive – absolutely necessary for our floor pickup and shooter. This design choice helped us to remain operable, though not at our best.

After seeing Einstein, I am definitely willing to put a zip tie around the Anderson connectors to the PD Board and the battery...

Re: How to make your robot withstand the beating
 

Keep your mechanisms simple, with fewer parts to break.

Re: How to make your robot withstand the beating
 

Don't make it out of wood.

There goes our passive climber. #woodenrobotproblems

http://farm9.staticflickr.com/8122/8...f9d4fe65_b.jpg

Re: How to make your robot withstand the beating
 

Seconded, with a couple of caveats.
1. - The same WCD wheel block design will get positive and negative comments from people here on CD. There doesn't seem to be one "best" design because they're all subject to the precision a team can get with manufacturing.
2. - The best way to know the best practices on WCD is to build it early. We did that, and it helped reliability a lot during the build season. We'll change the wheels, maybe use belts, and tweak the design of the blocks -- but I don't know that we'll ever move away from WCD now.

Re: How to make your robot withstand the beating
 

Our drive was not a WCD, but it was similar, only with a 1/4" plate on the outside and a 3/16" plate on the inside (or vice versa, not quite sure) and wheels in the middle. Direct driven wheel in the middle and dead axle chain driven wheels front and back made it super easy to work on the drive with no box fram, which was the original plan, one used previously. Although by the end of the season we had a small warp issue, the drive ran fine and we played some really intense,aggressive defense, so the forces on the drive were ridiculous.

My advice, do CAD testing and build it pre-season, in order to save immense amounts of time later. Design is iterative, so building and beating the crap out of it, then fixing the weak points, and repeating, is the best way to improve robot strength, and you will learn a lot about strong design in the process.

Also, if your team has limited funds, try a Kitbot on Steroids from Team 1114, Simbotics, as it is a great, rock solid drivetrain that works.

Re: How to make your robot withstand the beating
 

Simbotics isn't a Hall of Fame team for nothing. The resources they make available to the FIRST community are extremely useful for inexperienced (and some experienced) teams.


Now while West Coast Drive is great, and it worked extremely well for our team this year, it's not always the most viable option, especially for teams inexperienced with WCD and drive trains in general.
In considering different drive trains- build some in the offseason, see which are the easiest to build, design, program, tune, and test. Compare their weights and attributes. I've seen far too many teams use Mecanum this year that had no good reason for doing so other than they thought it was cool.

As for building a sturdy robot, my recommendation is to keep your main systems lightweight, then add reinforcement. If you look at Team 20's robot this year, everything is reinforced with brackets and C-Channel. to prevent damage.
We only broke twice during the season. Once during WPI finals, when our drive train's chain broke (as Brennon said above, we could still drive and score), and once at CMP when the cylinder that raised and lowered our shooter tray bent after a big collision with Team 4265 (Awesome team, btw. One of the best robots in Archimedes- and they were a 2nd year team!).
In both instances, we could still drive, score points, and collect, just not quite as well.

Robustness and reliability are just as (if not more) important than the amount of points you put up. If you're the best robot Day 1 of competition: That's great!
But you need to be able to repeat your performance Day 2- especially since the Defense gets even tougher.
Good luck with your season!

Re: How to make your robot withstand the beating
 

As everyone has said already, it takes a bit of experience to figure out where the weak points on the robot are and how to strengthen them. I do suggest that if you have the funds and capability you try and build a practice chassis during the summer and test it out.

However, here are some pointers that you should consider while designing your robot especially your chassis:

1. Forces: You need to anticipate where the forces are going to be exerted on your robot. In terms of the chassis, you can either be hit from the front, back, sides or the corners. The front, back and side collisions cause the chassis to compress whereas the corner collisions cause the chassis to twist.

2. Stiffness: Once you have figured out where the forces are going to be on your robot you need to determine if physical members can be added to strengthen or "stiffen" your chassis. For example, consider a traditional 6-wheel drive that has front and back bars, inner and outer rails on the sides. The wheels are located in between the rails. Now if you make sure that the front and back bars are connected to all for rails you will have successfully supported them from collisions (they may still bend but not as much if you only connected to 2 rails). Next if you are hit from the sides the outer rails will bend; you can add bars in between the wheels connecting the inner and outer rails. Now if you are hit from the corners the whole chassis tends to twist. you can mitigate this by connecting the two inner rails with what I call a "cross-member". Also if your belly pan is connected to the front, back and inner rails you will reduce the twisting of the chassis.

3. Force transfer: This is often ignored. When you get into a hit the force from the hit needs to be transferred to ALL members of the chassis. If is not the weakest parts will fail. Some of the most vulnerable parts of any mechanism or chassis are the joints. If you are using rivets or bolts ensure that you have more than one holding the members together. Remember more fasteners you add, the more you make the chassis/mechanism act as one but be careful of the weight! Use triangular plates to hold members together in places where members "butt" against each other.

4. Electrical Components: You don't want to put any electrical equipment on a member of the chassis that takes load. Again you need to anticipate where forces will be encountered in your chassis and put your electrical components in a "safe" spot.

If you keep these things in mind and use good judgment you should definitely may able to build a robust chassis or mechanism that will last through many competitions.

Re: How to make your robot withstand the beating
 

We here at 4464 didn't have many failures at all on our robot this year, despite it being our rookie year - admittedly, we have a lot of FRC experience between our mentors, but as important as experience is it's perfectly possible for young teams to make robust systems. You simply need to keep in mind a few things:

1) Keep it simple. This is far-and-away the biggest thing you can do to keep your robot in working order. The more moving parts a robot has, the more it will break, pretty much without exception; complexity breeds failure modes. This is a fundamental law of engineering.

2) Overbuilding is better than underbuilding. The weight limit is a pain, but mechanism failures are more of a pain, believe me. It is better to be able to fit fewer mechanisms within your weight limit and have them all be overbuilt than to fit a large number of mechanisms which are all prone to breaking.

3) Machine things well. This does not mean that everything must be CNC'd or professionally done, but it does mean that you should always err on the side of caution and make things slowly and carefully. A few minutes shaved off your manufacturing time is not worth the many hours of headache that comes with a poorly-build mechanism. If you don't have one already, try very hard to get a mentor with lots of machining experience. One of our mentors this year is a career machinist, and the effect it had on overall build quality is tremendous; I learned more about proper machining and construction this year than probably in any other year of FRC I've been through.

4) Don't design things you're not certain you can build with the resources you have. This feeds into simplicity - be conservative in setting design goals, and stretch if you have the ability. Doing things the other way around is a recipe for inconsistency and frustration. I learned this the hard way on 449, many times. The time for wild ambition is in the offseason, not in the build season - when you're under a deadline and success is important, stick to what you know you can do.