Ideas for Bricks & Tricks (FLL Tips & Tricks Website) Lesson Content

Hello FRC Teams! We recently posted on cd regarding the creation of our new FLL Tips & Tricks site, Bricks & Tricks, linked below. We have started to develop slides for lessons for FLL teams, and we wanted to get your input. If you have participated/mentored an FLL team, please answer any of the questions below:

  • What was the toughest challenge when you partook in FLL?

  • Was there any specific aspect of FLL which you or your team struggled in/didn’t understand very well?

  • What are some helpful tips which could benefit FLL teams?

  • What would you like to see students who graduated from FLL have more knowledge about?

In addition, if you could share this site with peers or any FLL affiliated members of your team, it would be greatly appreciated. We created this website as a space for FLL teams to grow, and it would be great if we could spread the word to assist FLL teams in their journey to explore their interest in robotics.

WEBSITE LINK: Bricks & Tricks

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Accurate, repeatable and consistent navigation is the greatest challenge for teams each year. If your robot cannot get to the right place, the mechanisms cannot do their job. Teaching methods to make the robot go where it is supposed to go in a repeatable and consistent way should be the highest priority.

I would strongly suggest that you show chassis designs that DO NOT use the wheels with the blue tires that come with the Spike Prime kits. They have less traction than the wheels with black rubber tires and have caused many teams a lot of grief and frustration. Last year, both of the teams I mentor conducted tests separately proving that the tires slipping was the source of their troubles in navigation. Both teams are using wheels with black tires this season and are getting much better results.

I would also suggest that you use chassis with ONE caster ball and replace the plastic one with a steel one. The steel ones roll more smoothly than the plastic ones. With two caster balls, you can have 4 points of contact with the table, if the table is perfectly flat. Over the last 14 years, I have never seen a perfectly flat FLL table. When the table is not flat, there will really be 3 points of contact with the table. As the robot traverses the table with it’s slight undulations, one or the other caster ball with contact the table. The caster ball that does contact the table will cause some drag. Because the caster balls are on either side of the chassis, the drag will cause the chassis to turn slightly to the side that is contacting. We discovered that this can cause the robot to wander side to side. Since the tables are not identical, the error will be different on each table and even from run to run.

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Repeatable and consistent navigation is definitely one of the biggest challenges. When we attended an FLL tournament last year, we saw that the SPIKE Prime wheels were very smooth, and were slipping on the smooth mat surface, so that is definitely something we will look at. Also, you have an interesting take on the one vs. two caster ball debate, and we’ll take a look at that. Thanks for providing your input! If you know anyone else who would be willing to provide feedback/input, please let us know, as it would be greatly appreciated!

People have been making posts on Facebook describing the symptoms of the wheels slipping for the last 2 years. Most attribute the problem to other causes such as the state of charge of the batteries or dust on the wheels and/or mat. Usually, the countermeasures they use that are aimed at those “causes” are ineffective because they are not the root cause of the problem. Those who try things such as using lower power levels when starting to move AND when coming to a stop report improvements. I also seem to recall seeing posts about some team adding weight and getting a consistent improvement.

The problems caused by using two caster balls is very dependent on the tables and the total weight of the robot and attachments. In our area, some competition venues have tables of very low quality. I also tend to work with teams with more parts than most so they build larger, heavier attachments to solve multiple missions. I also teach them to use more navigation aids so their paths are more accurate and consistent, making this source of error more apparent. Many teams get away with using two caster balls because they are building smaller, lighter robots and they are using fewer navigation aids so the errors caused by the two caster balls is mixed in with many other error sources.

Another problem many teams have is that they don’t know how to conduct experiments and make relevant observations. Often, they are changing too many things at once. Many do not use consistent methods to launch the robot. Thus, they frequently attribute improvements or decreases in performance to something that did not change the performance.

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Could you clarify something for me? When you talk about the blue vs. black rubber wheels, are you talking about the same wheel with different colored rubber, or are you talking about the older-style rubber wheels? LEGO does make the Spike wheels with black rubber, as provided in the now discontinued Robot Inventor set, as seen here:

I am referring to the wheels that did not come with the various Spike Prime kits that have black rubber tires. This is the first time I have been made aware of the wheel shown in your photo so I have no knowledge of how it performs.

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That’s why I asked. I suspect the black wheels will perform similarly to the blue ones, but wanted to be sure I understood what you were saying.

I do have a stock of both wheel colors. If there’s a standard way to test traction, I’d be happy to run some experiments. (Or PM me and I’ll send you a set.)

Put a pin of a contrasting colour in each wheel to make it easier to see when it is rotating.

Watch the robot from directly above. If it turns slightly to one side when starting to move straight forward at around 50% power, or above, it is most likely at least one of the wheels was slipping. It may turn to both sides if enough trials are run (5-10).

Have someone watch the wheel on each side very closely to see if it spins briefly before the robot chassis starts to move.

Make a program that drives forward for something like 3 or 4 rotations then stops in brake mode. Run the program 5 to 10 times ensuring that the starting position is AND heading is consistent. Starting with the flat end against a wall is a good way. Look at how much “spread” there is in the stop location. Repeat on a high traction surface and compare the results.

Your team can tell the judges about using such experiments to optimize their robot :wink:

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When I was in FLL, my team used the wheels from this lego motorcycle set. Due to the increase in grip, our robot was more accurate as the wheels experienced less slippage. When taking a look at the new FLL mats, I realized that they are smoother than the years when I was in FLL, so obtaining as much mechanical grip from the wheels is crucial.

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Those have good traction. You are lucky to have them. I think they may only been made for one or two sets in the past. They were only available from a few European vendors on Bricklink when we purchased them. They are also quite large so they may not always be the best choice. There are many other good options available.

Yes, I have a couple similar wheels, but the motorcycle set I got them from used a different tire for the front and back, so I don’t even have a matching pair. I think that’s why I always buy LEGO sets in even multiples.

Try Bricklink.com for your Lego part needs. It takes a bit of work to find vendors that have all or many of the specific parts you want. Watch out for the minimum order quantities and/or minimum order values. @Bricks you may want to add Bricklink.com as a resource in your materials.

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I should use BrickLink more. Lately I’ve been going straight to the source.

(Don’t I remember you from Lugnet?)

Yes, Bricklink.com is a great site for Lego parts, we will add that to our FLL site. Do you think having individual slides lessons for different hardware aspects of the robot (sensors, motors, attachments, gear arrangements/ratios) would also be useful?

Yes. The primelessons.org website and it’s predecessors, EV3lessons.com and NXTlessons.com, does it this way and has worked very well for many years.

The Isogawa books provide a lot of good ideas but some of them are built in a way that is only good for illustrating the ideas but are not very suitable for use in an FLL robot.

Ok, we will take a look at those resources, and we will develop slides content. Thanks for the suggestions!

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Also, if you don’t mind us asking, how should we go about advertising the site? We have been trying to advertise the site on First Forums and other places, but we have not gotten many users. Do you have any suggestions on how to advertise this effectively to FLL teams?

“If you build it, they will come.”

Start with good content and cross-links to other good sources of information. Once you have critical mass of useful (and somewhat unique) content you can more productively promote your site on social media and robotics forums.

Also remember that FLL season is over for most teams. You will likely see peak traffic to an FLL site starting in about September I would think.

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Thanks for the ideas! For the upcoming FLL season, we created a new website, added more content, and also shared some material we used from our time in FLL. You can look at the new site here: https://bricksntricks.weebly.com/. Let us know if you have any additional input. Thanks!

In the interest of spreading FLL knowledge, my friend and I recently created a YouTube channel (linked here). I personally think there is value in all of the videos and that they are packed with helpful FLL tips (there is also some info on Arduino). A few of the videos also talk about this year’s game (Masterpiece), so they can be helpful in approaching its missions.