Alright, so as many of you may know, push-bots have become the new meta; particularly for teams with limited resources and/or time, but who still want to make a robot with a fair chance of winning or placing in a competition. They have become somewhat controversial in their outstanding competitive performance for comparatively minuscule build times.
That being said, my team has begun the development of our mk2 pushbot - but we are experiencing drivetrain issues at this time - we are suspecting breakers or power expanders to be the culprit. Does anyone have any insight into our situation, or has experienced and/or resolved a similar one?
After some time driving, some of our drive base motors shut off, but come back after a while - this has happened at competition before, and in the past years, on other robots as well, and quite frankly we are not sure what the issue might actually be. On our build last year, we had the same issue at competition, which was strangely resolved by taking off the power expander.
8 4" wheel drive - each wheel powered by an individual turbo geared 393 motor
Outside 4 wheels are omniwheels, inside 4 are traction
Power expander used for the inside 4 wheels (currently suspected as the source of the issue)
2 393s used for arm
All 393s are evenly distributed in the cortex ports so as not to overload the internal 1-5 or 6-10 breakers
The turbo motors are probably your problem. Even with that many motors the friction created by pushing large stacks of game pieces under the fence and around the field will likely cause the internal ptc’s to trip on the motors. Personally I would not like to play on a field after a push bot had played on it either because the pushing of game objects builds up a large amount of static electricity and interferes with vexnet communication. It takes almost as long to build a competitive push bot as it would to make a dumper or a claw, I would suggest spending your time making a dumper or claw and improving it as the season goes on. Push bots won’t of any use at nationals or worlds.
I agree with @bwilfong2018 that the turbo motors are a big part of the issue. In a prior year, I had a team that built an 8 wheel mechanum drive pushbot and it could push anything anywhere. They used 393 motors as they come (high torque) and had zero issues.
I have also seen pushbots with 4 wheels and 8 to 10 motors powering those wheels, but not successfully with turbo motors. Some have had success with high speed, but even there, you still run the risk of tripping the ptc in motors.
The static electricity is a legitimate concern. I know that @Powerbelly sprayed the fields down with static guard at his tournament multiple times during the day. That took care of all those related issues and we plan to do the same thing at the next tournament we host. Other teams have gone to spraying their robots with static guard or rubbing them with dryer sheets. We are considering doing that as well.
I had trouble with the last one. It wanted me to check “I’m not a robot” before I could submit the survey, but I’m not entirely convinced that’s true. After all, I spend most of my time around robots and people have called me a robot before… Can someone help me work this out?
@Aponthis ok, do you fit inside of 18^3? Next, are you made of vex legal materials or exactly similar parts? Thirdly, can you get stars over a fence? If you awnsered yes to all three of these then you are indeed a robot
That reminds me of when my friend downloaded Pókemon Go on his phone but he seriously couldn’t get past the “i am not a robot” box
As far as pushbots go, I think they will eventually become totally illegitimate later in the season once people can start scoring small clumps of stars extremely quick or scoring larger groups of stars a little slower but still really fast(yes I know some can already do those).
Back to the original topic, I think we should find a name besides “pushbot” for these 8-12 motor pushing beasts. “Pushbot” is a derogatory term, usually referring to boxes with wheals that do nothing. These robots are a viable design, and do a lot more than nothing. Thus, I think we should start calling them bulldozers to distinguish them from useless pushbots and unmodified, screw-for-screw, instruction built clawbots.
Bulldozers can be good, but after seeing a number of them at my last tournament, I think other designs have higher potential.
One thing that may make pushbots (‘bulldozers’) much more viable is the fact that, as robots increase in capacity, their unfolded size becomes much larger. One team that comes to mind is 127C (@Aponthis), which at the last tournament, had a massive unfolding forklift that had a maximum capacity of 8 stars, iirc. However, 2 robots of such size on the field at the same time would make movement difficult. I think one of these robots with absurd capacity would work well with a much smaller pushbot zipping around the less manuverable robot.
Link related: https://youtu.be/DebqFCXBwE4
Honestly, we drove this thing around for over 4 minutes straight and played a whole comp with it, didn’t burn out once. 10 motor torque drive, with a 1:1 ratio straight down the drivetrain, and we split the motors on a power expander; two batteries are pretty important for a pushbot, since you’re running all 10 motors constantly. Pusher design on the front is actually quite important, make sure that its pushign as ar as it can under the fence without violating the rules. Also, to whoever said it takes as long to build a quality pushbot as it does a claw or dumper, we built ours in a day. So no, it does not take as long lol
I can say that this is a bad strategy. At our last tournament (we were forced to build a pushbot after our main design destroyed itself) we finished 5-0 in qualifications, but we picked a team with a very large robot. They disconnected in a match in the middle of the field, and we couldn’t get past them at all. We burned out and lost the match. Big robots, if unreliable, are a burden on the alliance.
This is not an argument against pushbots/bulldozers, but rather against your alliance partner. At very high levels of competition, such disconnects are not a problem (side note: when hosting a tournament, disable 2.4Ghz WiFi, it messes with VEXNet); a more interesting question is how did you and your alliance partner do before they disconnected?
They specialized in getting in our way. It was pretty impressive how they managed to do it that well… We were second seed and lost to the 6th seed (although we lost to 974X, but they weren’t doing too well that day). They ran a catapult with a four bar on the back to hang, and I can remember it almost smashing into our cortex while we passed them. Not fun.
I understand where you’re coming from with this statement, and i do somewhat agree. I believe a push bot wont be able to win worlds, but i have no faith at all in the system to weed out push bots. Every year at worlds, only about 50 teams per division are decent in my opinion and there are many (dozens if not more than 100) which would never be able to qualify for worlds let alone state in some other, more difficult regions. Therefore given the “ease” of building a useful (but not elite) push bot, i completely expect to see push bots continually throughout the remainder of the season. And yes, ALL elite teams will (if not already) converge on one or two non-push bot designs, however it cannot be ignored that push bots will still be around and still be a factor in competition (and in my opinion, a reminder of one of the many failures of the game design committee).
Every year’s game will have some flaws. It’s impossible to have a perfect game that isn’t too similar to a previous year’s game. I think that having well-though-out 12-motor pushbots being reasonably effective is a minor shortcoming.