Robot Building Tips Request

Howdy Partinoids,

I’m graduating this year, and I’m concerned that due to the low amount of interest at my school for robotics, the club will die with me. To give the younglings some advice and keep up participation, I’m compiling a little booklet of tips and tricks that may not be readily apparent to the novice bot builder. Feel free to add and comment as you wish.

  1. Go to vex forums. It’s a wonderful place.

  2. If you frequent the forums, please look for a question before you ask it. We already have enough threads about putting down intakes in Gateway.

  3. Watch old vex games. It doesn’t matter if it’s a different game, many design ideals are identical across games.

  4. Don’t cantilever your axles. Nobody likes bent axles.
    EDIT: You can do it to wheels, but make sure to support the axle in two places.

  5. Try to power as many wheels as you can, so if you get tipped, you can still maneuver out of it.

  6. There’s no bonus for smaller wheelbases, so yours generally should be a little smaller than 18"x18" unless you’re trying to fit through a small space.

  7. Low strengths chain’s elasticity and cough, low strength, makes it not very useful except for small intake devices. High strength chain, on the other hand, is better than fresh-baked banana bread.

  8. Chain is more mechanically efficient than gears and lets you put your wheels anywhere, so it’s good to use on drive systems.

  9. Try to connect as many wheels of your drive system to power, so your traction is better.

  10. Conversely, gears are great for lifting arms.

9 1/2. Gears in order of usefulness: 12t metal pinions, 84t gears, high strength gears, rack and pinions, normal gears, bevel gears, worm gears.

  1. If it only needs to be flipped down/out once, elastic or gravity is better than using up a motor.

  2. It’s easier to put a potentiometer/encoder in your robot arm/drive and not use it than try to fit one in after you’ve assembled it.

  3. LABEL YOUR CONTROLLERS. World championship refs are great, but won’t look kindly on you for hurriedly re-pairing your controller and robot after the B-team stole your original controller.

  4. Let’s face it: in a perfect world, you’d have a month to test your finished robot and program the perfect autonomous. But you have other responsibilities and homework, so that’s not always the case. Even Grant Imahara spent the night before his first Battlebot competition hammering ill-fitting batteries into his robot. Try to aim for finishing your robot 1-2 weeks ahead.

  5. You don’t need a finished robot to practice driving. You don’t need a field, either. A simple, game-independent driving practice is laying out a tape square on the floor and trying to hug its inside/outside while driving around (From Grant Imahara’s Kickin’ Bot)

  6. If you have prior programming experience, go for RobotC, the mouse-based interface of Easyc is less efficient than a keyboard.

  7. A simple autonomous is better than none at all. Nearly every game so far has had a way to score in autonomous simply by a bit of thought and driving forward (green balls/footballs on the wall in Clean Sweep, “cheater rings” in Round Up, corner goals in Gateway). Even if you don’t score, you can throw a wrench into the opposing alliance’s plans by blocking their bot during autonomous.

  8. Unless you have to, don’t orient an axle so it’s in a motor on both ends. It’s hard to get in and unlikely you’ll use that exact length again.

  9. All axles should be supported by black bearings on both sides. If you feel a need for danger in your life, you can forgo a bearing on the side with a motor.

  10. If your robot does anything new or original, be prepared to explain your new strategy’s particulars to an incredulous judge. Having a printed copy of the rules works wonders.

  11. Don’t let yourself be carried by your alliance partner. They suffer the same screwups and malfunctions you do.

  12. Always have at least 2 more sets of batteries charging.

  13. Generally, using a power expander is better than not.

Any comments or additions?

3 Likes

there is a 72t gear?

  1. When using bolts, tighten them immediatly. There is no later, you will forget about them or not be able to reach it.

Never go for easy, it never works. Hard work pays.

  1. Think before you cut metal.

How about:

-Don’t use the bearing rivits… EVER!
-Use Lock Nuts on any pivot points and in places where it would be very inconvinient to have to re-tighten a bolt.

  • Aways counterbalance your arms. Surgical tubing or rubber bands are great for this. (rubber bands are easier to make consistant in tension)
    -Triangles are your friends. (much stronger then rectangles)
    -Don’t intentionally pop the clutches. (Even though it’s fun)

Cantilevered wheels are fine if you know how to do them… We will probably unveil our robots soon and one of them has a six motor catalivered asmytrical 6wheel drive that takes full advantage of the 18" box for its wheel stance. It’s pretty slick (and very stable.):slight_smile:

no ALWAYS use pop rivets, there quicker, dont come loose and are lighter
(i know screws don’t weigh much but it dose add up)

I call shenanigans on this. When they are brand new the rivets do a good job of holding the bearings in place. However, they get much looser with successive reuse and we have had many experiences where they “pop” out at inopertune times. I finally got fed up with loosing rivets during matches so I just replaced them all with bolts, no problems anymore. So if you don’t want to have to be constantly checking for loose rivets you should lean towards new rivets or bolts.

yes and screws strip with too many uses each part is subject to wear and rivets are cheaper to replace

-If planning on making a design notebook, start immediatly. Nothing is harder than trying to remember all that happened in the last 3 months.
-Kludges yeild bugs, designs yeild solutions.
-Relax robotics is fun!
-If it is not supposed to rotate, mount it using at least 2 points.
-Communicate with your team. Words such as thing-a-ma-jig, whats-a-ma-call-it, thing-a-ma-whats-it dont count as good communication. “The green thing” is not particularly helpful either.
-Trade-offs will occur. When you make a choice go with it and don’t putts around trying to do both. They are called trade-offs for a reason, you can’t do both.
-The simple and elegant solution is both simple and elegant, the epitome of a good robot.
-During prototyping go crazy, you don’t know what you can do until you do it.
-Know when to buckle down and face reality, to compete you need a real-bot not a pretty picture on a piece of paper of the perfect plan.
-Learn your teams streangths and weaknesses. Who can you turn to for help with a particular problem? Who will need help compleating a task?
-Read and research, it is amazing the number of great ideas out there.
-Purchice graph paper for sketching, trying to decipher a mess of spagetti is annoying and a waste of time.
-Take pictures of mechanisms developed by your team, you will see a need for them again.
-Take pictures of your robot, when somebody drops it, it is easyer to reasemble.

1 Like

I’ll add comments, rather than additions, as your list is well on the way to being quite comprehensive.

I’d suggest combining tip #4 and tip #8. For tip #7, while I agree that chain offers the advantage of transfering power over a distance, I’d be hesitant to make the blanket statement that chain is more mechanically efficient than gears. Both gears and chains, when properly installed, tensioned and lubricated, can achieve efficiencies in excess of 98%… gears have a slight edge and can reach closer to 99% efficient. This efficiency plummets rapidly, however as soon as the gears or chains are misaligned, dirty, or otherwise improperly set up.

I don’t know as there are any published values for the VEX gear efficiency vs. VEX high strength chain efficiency, but my experience would lead me to suspect that any fundamental difference in efficiency between the two is insignificant relative to other design decisions.

A small point, perhaps, and directed more at the general statement comparing gears and chains rather than the specific suggestion to use chain where appropriate in the drive system.

Jason