This is pretty late, but I have been very buy with the start of the school year. Without wasting anymore time lets get into it. For this tournament me and RJ traveled to Wilkes-Barre, Pennsylvania. We left home about 10PM Friday evening, with plans on arriving there at about 8-9AM Saturday morning. Travel goes well without a hitch, and we end up arriving at around 8:30AM.
This tournament was hosted by Raymour and Flanigan furniture store, and they had the box set up in the middle of the Store, and it was the first thing you saw when walking in to the store. Very cool setup with a lot of couches and chairs surrounding the box for people to sit and watch the event.
The box setup in the main lobby of the store
When getting there, they had us move around back to their warehouse area which is where they had us set up pits.
I ended up wearing my old high school robotics shirt, represent.
Me rebuilding the weapon assembly for the 4th time that morning.
The first fight of the day was against Captain Doom. Captain doom had 5 ground scraping forks on the front of their bot and a powerful drive train that made them very difficult to bully around the box. Without my primary weapon this match was going to be near impossible to win due to their more powerful drive train and low ground clearance. At the end of the match however, we have a giant collision that ends up knocking something lose in Captain Doom and they are rendered immobile. We win the match and qualify for the round of 8.
Since Captain Doom was just a push bot, we didn't have any repairs to do outside of charging the batteries. This left us a lot of time to try and figure out why our weapon wasn't spinning up. Upon the recommendation of another builder (I can't recall who) we lowered the kv of our brushless motor and swapped from a 3200kv motor to a 1100kv motor.
Me rebuilding the weapon assembly yet again.
Finally ready, with the weapon working.
For the next match of the day, we were facing Mondo Bizarro. Mondo has a very nasty vertical spinner on the front, but a relatively weak drive train. So for this match I wanted to stay away from the front of his bot and get around to the sides and the back. However, this did not go quire as planned, and I took a lot of early hits that ultimately led to the failure of my weapon. This fight won me "Most Destroyed".
After it was all said and done, we were unable to continue on the day. We finished top 8 and got this cool gif.
cool gif
Overall Thoughts:
I think performance was pretty okay, but had issues with reliability off the bat. Below are a few thought on how to change the design and how to prepare for future competitions next calendar year.
Remove all 3D printed parts from the design. They are pretty rigid, but tend to snap and break instead of losing chunks and chipping. Want to switch over to UHMW for the mid and back plate, or possibly 2 different materials. The logic being that the back is subjected to more hits, and the mid is subjected to more torque and sheer force as the different sides get hit. Will probably get completed after the November Tournament in Virginia.
Make the permanent switch over to a lower kv motor. Maybe not 1100kv as that seems a little bit too low, but under 2000kv. However, all I have on hand are 1100kv, I'll see if I can find some 14-18 hundred kv motors before the next tournament. (Will probably get completed before the next competition in 2 weeks)
Practice driving, I really shot myself in the foot not practicing driving more, with that being very apparent in the Mondo match.
When replacing the set screws for the wheel hubs, I noticed that the hole in the hub isn't actually lining up with the slots in the drive shaft and the set screws are actually sitting outside of the slot. So, I'm going to do a slight rearrangement of the wheel assembly to see if I can get the slots to line up with the set screw, and if not I'll grind the slot slightly wider to accommodate. I suspect that this was the reason why I lost so many wheels in my first competition, since the set screws weren't in the slots, any loosening of these screws would cause the wheels to come off with enough centripetal force.
Also related to the wheel assembly is that the mounting hubs are actually not screwed in all the way due to the short length of the screws used to screw it in. I believe at some point in the design process I changed the depth of the counter sink and never adjusted the screw size to accommodate for the new longer distance the screw has to reach to be fully threaded into the mounting hub. If I have the time I'm going to make my way over to the hardware store to get a 1/4" or 5/16" screw to replace the current 3/16". I didn't necessarily have issues with the hub ever coming lose in the last event, but better safe than sorry.
Additionally the teeth on the weapon are only held in place with zip ties working kind of like a shaft collar. I think I'm going to try and replace them with larger zip ties to get a more effective collar on the shaft, possibly add some sort of high friction item on it so that it really chokes the shaft and doesn't slide.
Update On Current Status
With the competition coming up in just a few short days, I'm getting down to the wire here. I still have to manufacture 1 more wedge, I don't think I'll need more than 2 for the whole weekend. However, if time allows I will try to cut out one more so that I can have a total of 3 for the weekend. I currently have only 1 extra back plate, but I'm not really worried about any of the bots at this event having the destructive power to destroy the plate outside of Silent Spring since most of them are wedge bots, or other vertical spinners.
Yesterday evening the Blue Loctite, vice grips and brightly colored duct tape to mark my vice girps came in the mail. This morning I made my way over to Kleindorfer's hardware. They have consistently been a great help to help me find the hardware that I need, with fast and professional customer service. They helped me locate replacement screws for a few different applications around the bot which include...
Wheel set screws - will lock
Drive motor mount screws - will lock
Shaft collar screws - will not be locked
Weapon motor mount set screw - will lock
I was able to get most of them in a higher grade than what came with the parts originally to hopefully, when paired with Loctite, hold up better to repeated screwing.
Today I was also able to print out the outline for the new wedge, the new angle of the wedge even on paper is looking a lot better than what it used to and I will hopefully have it all cut out and ground down by Sunday.
Officially signed up for R&F Robot Fight 2019 (9/14/19) and Hill City Robot Combat 2019 (11/9/19). Was unable to sign up for NERC Franklin Institute 2019.
Rebuild
Currently: The bot is completely rebuilt, have run a weapon and drive test and everything seems to be working. Updated the circuit to allow myself to more easily turn off and on the bot (and make it compliant with safety protocol.
To Do: Cut and grind new wedge and backup wedge, buy stainless steel replacement screws for all set screws and shaft collars, buy loctite and apply to appropriate areas.
While flying home, I had a lot of time to review a lot of the film more closely, and reflect more on things that went right and wrong in and out of the box at the last competition. I'll be splitting up the list by rough groupings of what the note has to do with.
Driving Technique and Bot Configurations:
For the first couple matches I had the control toggle on on the controller, this toggle is designed to give finer movement and control of RC devices. As I quickly found out I was one of the quicker bots in the arena and should be leveraging that to my fullest advantage instead of trying to focus on the finer movement.
Use speed to more effectively get around to other bots sides.
Remove wedge for large vertical spinners with a wedge.
Weapon Management and Battery:
From what I can tell the battery is over specd and is capable of running multiple matches without needing to be recharged/replaced. However this is only speculative and is based on 2 relatively short matches. Maybe cut back to a 750mah or 850mah to help cut weight and size. Will need to do actual math for this, ugh.
Rev to higher rpm, with 4 weapon teeth I can afford it. Didn't seem to have any termal or reliability issues after removing that one tooth. Also didn't cog as much (only during a new dig match) as it did during pre-competition testing.
Weapon reliably started up and reved quickly. Considering changing weapon gear to 18 or 22 teeth so that I can get a better ratio to hopefully solve any cogging that is still existent.
Things to Change/Improve/Redesign:
Loctite, almost lost semi-finals to a lose drive motor, luckily it didn't come lose till the tail-end of the fight. Wheel set screws, weapon set screw, drive motor mount screws.
Even out the grind on the drive motors key slot.
Prep all my motors leading up to next event (luckily at this last event I didn't have any motors burn out) so that if one breaks I can actually change it.
Lower wedge angle, and grind it more flush with the floor.
Make sure wedge is actually touching the floor.
Things to buy:
LOCTITE on drive motor mounts. All 6-32 screws seem to stay tight and probably don't need it. Maybe on set screw for wheel and weapon mount?
Belt Sander to grind wedge better, (brownsville???) if not go to grainger or other tool supply store
3/16 steel setscrews for weapon hub.
possibly new sized banebot hub?
Switch out screws on shaft collars to stainless steel ones from the stripped crap screws that are on them now.
Event Update
Events that I am attempting to attend in the next couple of months leading into the new year are...
This may change based on class/project/test schedule this coming semester. Each event is about a month apart so that I have a break between tournaments to reprint, fix, and update design between events. Currently, I am registered for R&F and HCR, and will be attempting signup on Friday at 8PM est for the NERC event. I have been warned that the event will be very hard to get into and that the signup will fill up extremely fast, so I plan on being online and on top of it that day.
After this weekend and getting my first real driving practice with the bot with the weapon in full swing I have a lot of personal notes for ideas on how to improve the design before the next tournament in September (hopefully). First things first I want to cover pros and cons of the design that I saw this weekend.
Pros:
reliable/rugged
high potential damage
very fast, seemed to be one of the top 2 fastest bots there in the weight division which has potential for a lot of out driving these drive motors are very well rounded and are probably actually over-sized for this weight division.
lots of torque, won a few pushing matches
invertable, can drive upside down
after reducing the weapon teeth from 5 to 4, I had a lot higher weapon reliability.
Cons:
relatively high wedge clearance, wasn't winning wedge on wedge fights
steep wedge, couldn't get people up the wedge due to the aggressive 45 degree angel
difficult to open and close top of robot quickly
need a main power switch that powers and unpowers the whole bot, opposed to the janky 5v eliminator workaround I had
Ideas for redesign:
Less steep wedge to allow bots to actually drive up it and into the weapon, lower the grade of the wedge by 33% and bring it down to 30 degrees instead of 45.
Better ground wedge, have it have a lot tighter ground clearance to allow me to win more of the battles for the low ground.
Possibly change wedge material to aluminum sheet? (not sure if weight will allow)
Redesign backplate of the robot since I abandoned the side armor in favor of a front wedge.
Use loctite to connect the drive motors with their mounting hubs, they tended to unscrew themselves after rougher matches and when the weapon was running for a long time, this connection should be almost permanent except for when a drive motor burns out. Actually had a drive motor twist its leads to crap after it came unscrewed during a match.
Add tolerances to the mounting holes in the backplate so that I don't have to sand it for 50 minutes every time I print a new one.
Possibly add a well for the nuts that attach the top and bottom plates to the frame, to hopefully decrease time it takes to remove and attach it.
Look into why the nut in the middle of the top plate keeps getting stripped and messed up. I've had to dremmel off the screw 3 times now. :( not fun.
