I need some help on deciding on what to do with our kit chassis. We have our robot base running and are working on our manipulator prototypes right now. We have not decided whether we will have a long or wide chassis, but I am pushing for a wide chassis.
Is whether it is worth it for our team as a rookie team, to build a custom chassis? If we did I would thing we would make a box frame like two Kit frames on top of each to strengthen the chassis. We have a mentor who can weld aluminum for us, and some of my classmates could come up with a design easily in CAD. But I don’t think whatever chassis we come up with would be that beneficial as a team with years of experience. Because we are not doing a different type of drive like a swerve drive, there seems like there is not much benefit. We could lose a couple of pounds from various fasteners, I don’t know what else. Also, if we have to make a hole in the front for the ball retrieval mechanism, the custom frame could have better reinforcements built in. And it seems that there is not much weight saving from 5052 aluminum to the 6061 1in square tubing with 1/8in walls. We do have several spare hands though, so I could assign the chassis team to work on a new chassis rather than working on the prototypes of the manipulator. Or we could just have our mentor weld the Kit Chassis.
It should help with some stuff. My answer directly is it depends on your strategies. Never make any final design decisions before knowing what you want to do, what you’re going to do, what you’re not going to do, your priorities, what you can and can’t do, and how you plan on playing the game. Plan out a few matches, and be open to possibilities.
After you’ve done all of that, the answer presents itself to you. Trust me, it’s a lot easier to have all of that other stuff done. Then just analyze it and see what designs to choose.
This is my advice not only to you, but to all teams.
No. It is not worth it to spend your time redesigning the kitbot chassis. As a rookie team, you are going to be spending a great deal of time learning what doesn’t work. In this game, your ball-shooter and manipulator is a huge challenge in itself. Go find the 1114 video kitbot on steroids, and take lessons from that on how to assemble your chassis. Then move on and work on ball acquiring and your turret.
You will have more than enough coding and mechanical challenges just trying to put together an accurate and consistent ball shooting mechanism.
We have part of our ball manipulator stuff on the kit chassis, but we’re planning to make a custom chassis. The kit chassis won’t work for what we want to do, and we’ve built a custom chassis every year except last year (and the kit chassis does have a design flaw that we didn’t anticipate, and led to our robot failing in eliminations).
I guess what you need to do is figure out where you are, and where you need to be, and decide if you can get there using the kit chassis, or if you need to do something else. Also consider just modifying the kit chassis, making kind of a “hybrid” chassis that uses as many existing parts as possible, but new parts where needed to make it work.
Another thing…we try to make the “upper” part of the robot as light as possible, and we don’t worry much about how heavy the chassis is, within reason. Our first year, we had a top heavy robot, and learned the hard way about center of mass.
This year we plan to make another steel chassis, it’s pretty entertaining watching people see it and shake their heads in disbelief
188 made that mistake in 2006. We built a very fancy laser-cut and welded aluminum sheetmetal chassis, with a low profile and clearance for climbing ramps. It was exceptionally light, and quite stiff in most directions when the top plate was bolted on (to tie the gearboxes and bottom plate together).
Then we stuck a 30-pound shooter on the top, along with enough other stuff that the robot was at the weight limit, as usual. :o
This is exactly what we have built, and have been playing with for the last week. Our team went to a work shop after the kickoff and had the robot mostly assembled. It took us a couple days after that to figure out that our programming was not working because the connector on the cable to the sidecar was on backwards. We only are powering the middle wheels until we decide whether the base is wide or long. Then we will cut the rest of the chain.
Instead of designing a new chassis, I tell the chassis team what everyone was saying, that it is not worth designing a chassis because we do not know about chassis design. Instead I will have them work on the BAD (Ball Acquisition Device), and consider the two chassis and just making small modifications where ever we need.
Use what’s provided in the kit. We love the c-base channels included in the kit, and use them to build all of our chassis. I highly recommend 1114’s Kitbot on Steroids. We’re doing our own version of that this year, but just reading it helps.
From what what’s been described so far, I’d really suggest using the kit chassis. It’s easy to take apart and bolt back together together again, so it’s not difficult to make modifications to while you’re testing.
The most important thing I’d suggest, especially this far into build season, is that you finalize your robot design before you make any cuts or modifications to the kit chassis pieces. I would make a decision on chassis configuration soon though, because tweaking your prototypes to fit one chassis design or another can wind up taking more time than you think. You also do not want to take time away from prototyping and finalizing your other systems, such as a shooter or intake device.
You definitely seem to know what you are doing, but as a Rookie team, it’s important that you don’t try to bite off more than you can chew. As you mentioned, you haven’t designed your own chassis before, so its good to think about that before diving into it, especially since we’re entering week 3. It definitely sounds like you have the resources available to you, but make sure that you keep on top of how much time is left in build season. The last day of build will creep up on you faster than you think.
What is/was the design flaw? I am very interested to learn what the flaw was and how it impacted your robot.
Welded steel chassis? Approve!
OP: the kit frame is probably more than adequate for what you want. My team will be using a customized kit-frame, welded together to save the weight of the kit fasteners (~3lbs).
The flaw* with the kit chassis is the length of the axles between supports (the two c channels) makes it susceptible to damage from hard vertical impacts on the wheels. Two possible fixes for this are to increase the axle size to 1/2" or to move the two c channels closer together (reducing the bending moment on the axle from any given load on the wheels).
*Flaw in this case refers to a structural limitation, not a fatal mechanical design oversight.
The kit is awesome for beginner teams and vets alike. We’re not using it this year for us, but i’m sure it can be worked to make due for this year.
We’re doing this, this year. The biggest reason was how much easier it is to weld, we really wanted as many aspects of our robot to be done by our students instead of the mentors welding it.
I can’t wait to see people’s faces when we tell them it’s steel!
We built something like this last year for a “develop-bot” so the programmers can perfect their code during bag and tag. We used plywood for the middle and it worked out great. It was actually very sturdy and easy to screw things to the floor.
