Which bot for Worlds?

  1. Proven skills bot - driver is very efficient. Obvious disadvantage is no stacking. I think it makes an alliance selection almost a “certain no” so they would have to focus on skills and hope they get good qual partners and are able to finish top 16.
  2. Average chainbar - driver is familiar. decent efficiency. Can stack up to 5 cones internally.
  3. Brand new dr4b. Will only have about a week of driving practice.

** all 3 bots will have autonomous options for matches (minimum 10 or 20 pts from either side)
** MS team

What would you recommend?

Disclaimer – I’m just their teacher…want the decision to be theirs ultimately, but would like to share some community feedback with them.


I would suggest option 2 unless the team has experience with building a DR4B. Stacking is going to be incredibly important if you want to make it to eliminations at worlds so option one would limit you to hoping that the other teams dont score all of their mobile goals, which is unlikely. Also, building a DR4B was incredibly complicated for my team since we have never built one before so it took us about 6 months to really make it work well.
Tldr: If you have experience with DR4Bs go for that, if not I would suggest the chainbar.

I recommend sticking with the chainbar. Even if the driver is currently average, from now to worlds is plenty of time to get A LOT of practice. 3 weeks is enough to make driving a robot second nature if you just spend 1-2 hours at least 3-4 times a week. I say this from experience because our driver from Starstruck had about weeks or so to master driving the robot and he became close to perfect at it. Even though this game requires more accuracy than Starstruck, I still believe that it is enough time. You may even have some time to make a few tweaks to improve it so it becomes better than “average.”

Speaking from experience, I have made the jump from chainbar to reverse double four bar myself. The DR4B is a consuming design that has a huge payoff when done correctly, but is a very large pain to redo if you mess up. Considering the fact you have a week of driver practice assuming all goes well and ideally with the DR4B, I’d recommend staying with the chainbar unless you can do the following:

  • Make sure you have a power expander! This is crucial in building a dr4b, as the power requirements are a lot more than that of a chainbar.
  • Build and tune (make sure banding is good, the lift is actually linear, all motors on the lift are powering, etc) such that you are allowed for a minimum of 1 week of driver practice.
  • Have an adaptable driver. As the driver for my team, it was a bit of a jar going from a nonlinear to a linear lift. The approach to gameplay and the added option of now being able use the driver load station requires skill and flexibility within a driver (knowing when to manage what). I would recommend experimenting with partner control if you have other members who have some experience with driving (I would personally split partner control as such: 1 controller for base and mogo intake and the other for lift and intake).
  • Get started immediately. You have a little less than 3 weeks before worlds. You need at least a week of driver practice.
  • Follow the following motor distributions:
  1. 4 HS motor drive
  2. 1 HS motor mogo intake
  3. 4 HS motor lift (1:5:5:1 in the gearbox)
  4. 2 HS motor vertibar/chainbar
  5. 1 HS motor rollers (Goliath intake)/top-down claw
  6. 6 motor drive HS/Turbo (I personally prefer HS)
  7. 1 HS motor mogo intake
  8. 2 motor Turbo lift (1:7:7:1)
  9. 2 HS motor vertibar/chainbar
  10. 1 HS motor roller/top-down claw

I used the first blueprint and it yielded great success for me and my team.
I would also recommend using screw joints for the middle two gears in the gearbox (just personal preference, you can extend the length of the joint via standoffs if need be). Although considering the time you guys have, I think just slapping axles on in lieu of experimenting with screw joints might serve you better in this case. Also make sure that your mobile goal intake does not wobble. I was successful in building mine, and I was lucky enough to build it so it did not wobble when stacks got high. Also, be realistic in your designs. You’re never going to be realistically stacking more than 15 cones per
mobile goal, so build your lift to accommodate that much only. Don’t use unnecessarily long metal (unless your strategy requires it).

If you find that meeting one of these criteria are difficult, here’s what you can do:

  • Get a lot of driver practice with the chainbar. Get really fast and really accurate. Learn scoring strategies, maneuvering tactics, etc.
  • If possible, add an elevator to your chainbar. Since your members are already familiar with the chainbar subsystem, it only helps the cause. The elevator will allow for you to be able to stack more than 5 cones (the chainbar I used had a six cone maximum. While I ultimately caved and went for a dr4b, the elevator lift definitely was a good option).

If you really feel like a DR4B is the best way to go, I would encourage you to go ahead and do it. However, things can go awry with such a complex design, especially with such little time. I personally was unable to build a good dr4b in a reasonable time span (took me about 4-6 hours of consistent work to get it perfect). Working with my team yielded in 3-5 hours of getting a perfect lift. Honestly, I feel that since your chainbar enabled you to get from regionals to states to worlds, you should stick with it. The allure of dr4b is tempting, but with such little time and a complete design revamp, you stand at risk to jeopardizing your whole bot. Ultimately, the call is up to you and your team. Just my 2 cents.

Good luck at worlds!

EDIT: After checking the calendar and timetable from now to worlds, you guys honestly don’t have enough time to build a good dr4b, intake, mogo lift, etc AND get enough driver practice to be a force to reckon with at worlds. Not to mention autonomous as well. Stick with your chainbar, get it to be fast and consistent via driver practice. Make a 20 pt auton (1-2 cones on the mogo scored in the 20 pt zone) and do the same for 10 pt zone. Since you have a stack height of 5, I don’t think your chainbar can reach the stago, so don’t bother with it. Practice stacking as fast as you can, and efficient scoring methods (maybe try a bit of defense. Assuming a max stack height of 5 and you score 1-2 mogos, that leaves quite a bit of time. Try negating your opposition some points BUT STAY WITHIN THE LIMITS OF THE RULEBOOK). Stick with the chainbar, and make it perfect. Get your autons done (the two I proposed above plus a ramming auton [auton that just drives forward into the paths of your opponents in order to block their auton].

Perfect the living cr*p outta that chainbar and take that. Skills bot just seems like a boring way to spend worlds seeing as how every match is just pure luck. DR4B will preform worse than your chainbar most likely given the drive time. I promise you that a rockstar chainbar will put you in the top 10% of MS worlds. You’ll be beating mediocre DR4Bs left and right. Don’t believe me? Just look at the videos of previous year MS worlds. In VRC, consistency and cycle time is king. What should you do in the remaining 2.5 weeks?

  1. Program mulitple consistent autons, I’d recomend a 20 pt mogo with cone, 10 pt mogo with cone, a defense drive forward, and stationary if you can reach
  2. Clean up minor build issues in 1-2 days max, do NOT rebuild mechanisms if it can be helped

Out of curiosity, what is the motor distribution on this chainbar?

p.s., to put this all in perspective, at ITZ SoCal state ( a relatively competetive state championship) the number 3 captain was a chainbar.

Thanks for the feedback!

@AyushR66 they have already started the dr4b. They have a drive, mogo lift, and both sides of the lift done. Still a lot of work to do with stabilizing and finishing before actually driving though.

@Ashwin Gupta this gives me some confidence on their behalf. There is still a little tweaking here but it really is just simple stuff. Current setup is 6 HS motor drive, 1 motor mogo, 4 motor lift, and 1 motor Goliath intake. Thoughts?

Edit: the skills bot is a pretty good one. Curently a score of 132. Not a Worlds winner with that score, but quite conpetitive nonetheless.

@jonathans Are they not going to internally stack the cones? In my opinion, they should’ve kept the Chainbar and practice different strategies with it. Like mentioned above. It takes time to tune a really good DR4B and with worlds cutting it close, and this is their first one, I don’t know if that was a wise decision, but if they can pull it off… props!

Good, the 6 motor drive is your biggest asset: so use it. Practice cycling two mobile goals with the 5 cones from the field each. In a match, you might only be handling one mobile goal depending on how good your partner is, and at worse you’ll handle two. That really shouldn’t take longer than 1:00 of the match most likely so try to get it into that time.

It leaves you with quite a bit of spare time for defensive gameplay. Your 6m drive will let you be aggressive without burning out. You can win push fights against 4m HS drives which is 80% of the metabots so use it. e.g. if the oponent goes to pick up their mogo you can get in their way. If they keep pushing, they’ll stall themselves out, if they wait for you, its at no consequence to you because you still have plenty of time to do your two 5 stacks and let your partner handle the rest. Play this offensive/defensive mix correctly and you’ll rank high on your own and if you don’t you’ll get picked as a second for the defense.

I would suggest option 2. Unless they can score in the 90s or more in programming skills, they will not be able to win skills at worlds without stacking cones. There are 8 middle school teams that have score more than 104 in driver skills and 6 of them have been 110 or more. By worlds, it may be even more and the numbers may be higher.

Having a decent robot with lots of practice will be better than having a great robot without lots of practice. That is my though, anyway.

@[TVA] Thomas - They were really set on this, but just haven’t been able to iron it all out in time it looks like. I’m in agreement that it was a tall order for a bunch of 7th graders who had never built one before, but no way I was gonna tell them know if they wanted to give it a shot.

@Ashwin Gupta - Thanks for all of you input. They are good kids will appreciate the point of view.

@blatwell - I agree. There a lot of good middle school scores.

Hey @johnathans my team (Team 56G) is going to worlds too! We are also a middle school team and if you would be interested in talking to us we would love to. You can contact us at team56G.info@gmail.com. We can also give you some pointers on using that dr4b!.

@Team56Gofcape nice! I’ll be in touch. I’ll shoot you an email in just a bit.