Chris has some great points, but here's some additional information (shown in red) that 228 has learned from about a half dozen different iterations of homemade robot carts over the past twelve seasons. We've learned all nine points the hard way at one point or another.
Quote:
Originally Posted by Chris is me
As someone who had to push around a robot cart for four events last year, a few things:
1. Big wheels (pneumatic tires or rubber) make going over gaps and wiring sections on the floor much easier. 3 inches of ground clearance in the middle is perfect, less requires some work.
2. A solid removable handle is significantly better than a rope handle.
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Nothing is more annoying (or a potential safety hazard) than having a solid, non-removable handle. Having an easy to remove solid handle allows you to remove the handle to work on the robot and make it easier to lift the robot onto/off of the cart. This can be something as simple a bent or welded piece of aluminum tubing than can slide into a slot in the cart.
Quote:
Originally Posted by Chris is me
3. 2 (at the end of the cart opposite of the fixed handle) and 2 omni / swivel casters (at the end with the handle) works well for maneuverability; four casters is a little harder to control with just one person.
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When you put the casters at the end opposite the handle, you'll have a large rotational moment when trying to turn the cart. If you put the casters at the same end as the handle, it'll be much easier to rotate the cart.
Quote:
Originally Posted by Chris is me
4. If you are going to build your own cart, while storage for stuff like the driver station is nice (not required), storage space for spare batteries and bottled water should be provided. but your drivers will thank you if they have a spot to throw the controller. (Some robots have room on them for this kind of stuff).
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Having storage space for batteries will save you from running to the pits, and having storage space for ample bottled water will literally save you. We once had a member of our drive team collapse during the elimination rounds five or six years ago from dehydration. Since then we've taken aggressive measures to always have ample bottled water (or Nalgenes+drinking fountain) at all times.
Quote:
Originally Posted by Chris is me
5. Some events (cough 10,000 Lakes cough) have only 32 inches of clearance for your cart. Long way forward and no wider than your robot is the best solution, or at least a way you can shrink it.
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Standard doorways are between 30-32 inches wide, so this should be a universal standard.
6. Most FRC robots are a maximum of five feet tall. Remember this when building a cart. The maximum height of a robot on top of the cart should be less than the maximum clearance height of the lowest doorway you'll encounter.
7. Your robot will change every year, but when you finally build a cart, build it once. Therefore, design in an easy to change method for holding the robot every year. One good solution is to mount blocks on pieces of 80/20 (or other similar extrusion), to slide to new positions every year.
8. If you have a giant flat surface, put a lip on it. There will be times where you'll have loose hardware from a mechanism on the cart that's still being assembled as you rush back to the field. Having lips on the cart will prevent that loose hardware from getting hopelessly lost.
9. Make your cart lightweight. Don't make it motorized, don't put on surround speakers, don't have permanently attached toolboxes, etc. Make it carry the robot, carry spare batteries, and potentially carry the operator interface. Anything else should stay in the pits.
Here's a photo of the homemade (wood) cart 228 has been using since 2006, which incorporates all of the above features:
with handle removed:
