In your opinion, what are the best practical elements to include in a robot cart? What features are under or overutilized?
Portability & stability. The cart needs to be portable so it won’t take up too much space when being transported. Along with being stable enough to carry the robot along with any other tools you need to access quickly.
Make sure your casters can support the weight of the cart, tools, max weight robot, and a spare battery or two.
A folding tray below the push handles for placing a laptop could be useful.
Make sure there are blocks to keep the wheels of the robot off the cart, that way you can enable the robot on the cart. bonus points if the blocks are adjustable to allow for diffferent robot dimensions on different years.
Everything above, plus: height of robot off ground. It should be high enough that you can work on the robot comfortably, but not so high that it is physically dangerous for team members to lift it.
Make sure the handle is offset or your cart will become an ankle biter.
Survey past games for the maximum allowed robot height at the start of a match. Make sure that the cart can pass through a normal door with such a robot on it with some margin to account for the threshold strips that some doorways have on the floor.
A flexible way to raise the robot up is to use some of the black or grey totes that are provided in the KOP each year.
Ensure that the cart is transportable in a mid-sized SUV. This may mean a restriction on on some of the dimensions and weight or that some parts have to be removable.
Ensure that the wheels are large enough to get over cracks and seams in pavement since it is likely that you will have to push it across parking lots.
Make the cart < 30" wide. This will allow it to go through a standard size door opening.
Your cart should not weigh more than 400 lbs.
Your cart should be easily movable without power and by an untrained user.
Your cart should not be a Moto-Cart Jr.
Your cart ideally should carry the control board.
I’ll add a few considerations:
- Ideally, make sure your cart can support your robot in such a way that you can run the robot on the cart and not have to worry about it driving off.
- Consider the terrain your cart is driving on at the venues you normally attend. For instance, the pits at MSC are covered in this awful tiling, so we put pneumatic caster wheels on our cart this year which helped significantly with the bouncing we’ve encountered on them previously.
- Avoid using 8020 (or similar) in cart construction for long-term durability (speaking from experience).
- Make it obvious the cart belongs to your team (this can be as simple as writing your number on it with a sharpie or going crazy and putting an LED matrix display on it)
Adding to what I see above.
Recommend 4+ inch wheels to handle any bumps at door frames and any hard cable protectors.
Cart handles that won’t hurt the driver nor will let the driver’s hand slip.
Storage for basic tooling and an Ethernet/USB tether, to make any repairs needed in the queue.
Able to be easily maneuveured by one person, in all combinations e.g. fully loaded (that is full robot weight + anything else you need to carry), empty, etc
Takes up small area, for transportation to/from competition as well as during competitions (also within pits)
Low for loading (don’t need to lift a high), high for workspace (can stand and work on robot instead of kneeling or sitting)
Simplicity goes a long way. It’s cool to have a literal pit on wheels but is it really worth it if you need 2 students just to push it from a standstill?
Another big thing that I don’t think I’ve seen above is being able to easily place the robot so that it won’t move on the cart. Otherwise, the robot will either be shifting around on the cart which is a safety hazard, or it will take multiple tries to get it on the cart in a position where it will not slide around.
Be able to set the robot at a good working height, but not too high to go through a door.
Go through a standard door with clearance on both sides.
Easily moved and controlled by 1 person.
Easy to adapt to different robot design each year with minimal changes.
Easy to break down or collapse to fit in a car and reassemble by 1 person.
Minimum 4 inch wheels, preferably casters not pneumatic so they don’t got flat, so you can go over the expected wire trays and other obstacles.
A secure place to put the controls while headed to the field.
A secure location to store an extra battery.
A place to mount basic tools needed for a crash kit to stay with the robot, we use tool roll ups on the handle.
Positive location for the robot when you place it on the cart. We set our cart so the bumpers have to touch the vertical handle mounts so you know when the robot is positioned properly.
Attachment for any carry handle/strap/tool you use for placing the robot on the field or removing it.
After trying almost everything conceivable from a cheap push cart to a scissor lift table with powered drive we settled on a simple cart made from 80/20 Extrusion that also doubles as a shipping fixture for us to mount the robot into the crate. It can be broken down and fit in any mentor’s car for transit to events, as well as be adapted to fit whatever our robot frame is for that year. Most teams overkill with their cart, but it’s up to your needs. Just don’t do something stupid like making a cart so tall you have to take your robot off it and carry it through doorways. I saw at least 2 teams doing that this year.
Everything above but also make it strong enough to sit on. We like to use our cart as a bench when the robot is doing something. It’s very convenient.
Make sure its not overly loaded on one side at any given time to the point where it may tip. We had issues with ours when both our drivers station and toolkit were on the cart, and there wasn’t any counterweight and the cart would just tip.
We designed several different robot carts over the years before finally just reverting to a two-wheeler that folds-down into a four-wheeler that we bought at the hardware store, painted it purple, and called it a day.
Cons: It doesn’t hold the driver’s station or any tools.
Pros: It fits pretty much anywhere, stows easily to not take up much space in the pits, it’s lightweight with a low CG, traverses venue cable protectors easily, holds a robot and up to two spare batteries (and bumpers if necessary, stacked sideways), the rails are spaced so that the vast majority of robots can run on the cart without the wheels contacting anything, and it’s purple.
One thing I haven’t seen yet is having parallel rectangular tubes built in to the cart that can be used to accurately calibrate swerve module rotational offsets. The spacing between the tubes may need to be changed season-to-season, but good cart design could make that a relatively simple modification.
Out of all the good ideas that have been offered, I want to add +1 to a cart with adjustable height. The core of our cart is a hydraulic scissor lift and we get a ton of value out of that. Adjusting the robot height to work comfortably from the bellypan to the top of an elevator or shooter is a very nice feature to have.
Nah, you don’t need to be building a custom cart, McMaster Carr already made the ideal one to buy McMaster-Carr
We’re adding pneumatic wheels to our cart for MSC and ours also has hydraulics so we can move the robot at a lower height whilst also being able to adjust it to a good height for maintenance. It’s been great so far especially after adding a spot for our ds and we also have a small set of drawers on it for any last minute necessities for the drive team like zip ties our strategy items.
Edit: The hydraulics do make it heavy if we ever need to get it into a van or truck.
Think about the events you typically attend and take anything impactful from there into account. For example, one of our local events has some issues with doorway height on the path to and from the field. Having a super low cart can make a world of difference for your drive team, so they don’t have to take the robot off the cart several times to fit through doorways getting to and from the field each match!