Pwnage, Team 2451, 10X 775Pro Drivetrain Gearbox
We ended up only needing 4X 775Pros on each gearbox to power the robot to 3-CIM levels. The weight shown was for 5X motors and power leads. The actual weight is closer to 5.5 lbs per gearbox with 4X 775pros per side. It was too scary of an idea for some to contemplate at first, but it has been a big success, so far.
What is that first stage reduction ratio? Looks like it could be similar to the EVO …
When you’re running so many motors in the drivetrain, do you just put them all on the 30 amp fuse slots of the power distribution panel? Or do you put some at 40 and some at 30? Save as many 40 amp slots as possible for mechanisms? All those motors eat up a lot of real estate!
Maybe you should pitch that to AndyMark and work with them to get that as an option for the EVO Shifter. That is really cool.
I mean, who needs PDP slots for mechanisms anyway, right? :rolleyes:
Any particular reason you guys chose to go with 775 pros over a standard CIM drive? Have you had any issues with stalling or burned motors?
Higher efficiency and less space and weight I would think, at the cost of more PDP slots. 8 775pros is theoretically better than 6 CIMs in terms of power output without browning out.
How did you ensure the 775pros did not overheat and damage them when your robot stops as they are fan cooled? especially since they are so close together
Looks sweet! Can’t wait to experiment with a drive like this in the off-season, thanks for blazing the trail.
How long before we see a team go all out and use every PDB slot for a 775 motor on their drive? 16 motor drive, let’s see it.
In the picture, your fan-cooling slots have blue masking tape over them…?
Is that just to keep swarf out when building and then you’ll pull it off to run them?
Or is that to paint them black for better heat radiation…
How fast is your drivetrain and is it traction limited?
I like this in theory but I would be terrified of stalling it.
Where did you get those pinion gears on the 775pro motor? And are they just press fitted on?
They are 12t 32DP pinions available from West Coast Products:
They are easy to press onto the shaft with an arbor press, the convenient thing about fan cooled motors compared to sealed motors is that there is a bit of a “back shaft” sticking out the back. This means that you can press fit pinions( both gears and pulleys) easily with a reduced risk of damaging the motor( the force goes through the shaft rather than the case and bearings).
775Pro for the win!
In case you haven’t guessed: I really like this motor. Team 88 is driving with (4) 775Pros per side and we are very happy with them.
I have loved CIMs from the moment that I first saw that beautiful Coke Can sized powerhouse. Back then we drove our robots with drill motors… …and we LOVED IT! We couldn’t get enough of it (actually, it was kind of terrible – so many robots driving in circles for 2 minutes…)
I was responsible for finding these motors and getting Chiaphua to donate a few pallets of a particular version that they happened to have in the States for a customer called Atwood to FIRST so that FIRST could receive them in time to get them in that year’s KOP. The next year FIRST had a custom version designed with an 8mm keyed shaft that became known as a CIM motor (Chiaphua Industrial Motors more here)
Believe me when I tell you, the 775Pro is a game changer every bit as big as the Chiaphua/Atwood/CIM was back then.
Will there be more teams smoking motors? Sure, but that’s not the end of the world. Lots of Victors and Jaguars smoked (briefly) as teams got metal dust into places better-left metal free. We lived and learned.
And so it will be with these 19,000RPM dynamos. We’ll live and learn and we’ll have better robots because of it.
At least that’s how I see it.
Dr. Joe J.
Do you have a cad file of this you are willing to share?
Why not work it out for yourself? You could start here.
PWNAGE deserves to keep the reward of their hard-earned, detailed work on this little beauty for themselves, until after the 2017 season.
How noble of you. I have little interest in actually building this, I just want to see what it look like.
12 tooth WCP Pinions and 88 tooth custom 4140 gears, could also be sourced from Stock Drive Products. I highly recommend starting with (4) 775pros per side and skipping the 5-up setup. This would allow you to package them in a tighter circle and go with a slightly smaller center gear. We are running 5.2fps in low theoretical and 19.12fps in high gear.
We are running 3 per side on 40-amp breakers and 1 per side on 30-amp breakers.
Who needs open PDP slots? What do you use yours for?
Weight!!! This is 4lbs less than a 4-CIM setup and 10lbs less than a 6-CIM setup. No, we are running the same motors in our practice bot that we started the season with. They have minimal brush wear. You can see that the brushes have ridges in then tip of them and those are still present so the brushes haven’t even worn yet.
The first trick is to slot your mounting plates so that the vents on the mounting side are not covered. The second secret is that the battery can only put out so much current. Running eight motors at full throttle (limited voltage to each) limit each to a level where a 30-amp breaker doesn’t even trip. We had one lead motor in the Talon can system on a 30-amp breaker for a while and it never tripped. If it had the whole can bus for that side would have shut down all the motors, and this never happened. We have pushed our airship, on purpose, with this setup in low gear without tripping our breakers or burning out a motor. The tires are traction limited in low. In high gear they stall, but at the power levels we are running at they can stay stalled for extended periods of time. If you look at Vex’s motor data, you will see that the motors can be stalled for longer periods of time the lower the input voltage is.
We have 16x motors on our robot this year.
1-Meter Wheel for the shoooter
1-Ball Intake conveyor motor
1-Street Sweeper Motor
To keep stuff out when building the gearboxes, we removed this after assembling the gearboxes. The motors are so cool after a 2-minute match that additional cooling is useless. I felt the motors after 9 back to back finals matches at our last regional and they were lukewarm.
Traction limited in low gear, not in high gear.
Drive train will do 13.5 ft/sec in high gear with a 120lb robot plus bumpers and battery. (It will cover 20ft in 1.5 seconds at speed). It will cover 20ft from a standstill in 2 seconds.
Cad files are online, this was an off-season project and if you search CD you will find the link to this CAD and all of our swerve drive CAD. We don’t hoard our stuff.
Good info, thanks!
I’ve been playing with sketches and gear ratios already to come up with a design with a similar geometry as the one you posted. Packing just 4 motors around the idling gear cluster rather than 5 makes it easier to build with off the shelf gear sizes. This might be something we test with in the future, it sounds more promising than I thought when I first saw the concept. After using CIMs for so long, it seems absurd to put flammable motors into a drivetrain.