The 64T gear part of the module is one of the printed parts of the module. It snugly fits into the ID of the bearing, and the top part of the module (also printed) is bolted to the 64T gear part. These two parts lightly clamp on to the inner race of the bearing.
We did not try doing any suspension system on the drive. My assumption is there is likely a marginal gain, but I expect it is pretty minimal. 2767 could speak to whether they have measured how much of an impact it has actually had on performance. We didn’t feel like the added complexity was really worth spending time on. We did not experience any issues related to losing traction on a wheel from what we could tell that would make us think adding suspension is something we would need for this drive in the future.
Nick’s description is pretty accurate. Seems to help in auton but still the biggest gains in a straight driving swerve is a tight drive train, high count encoders, hyper tuned PIDs and a flat frame regardless the the suspension. That said, we will keep the suspension as long as we use our current topology because its there.
Nick, I love your module and could have held it in my hands all day… like a puppy.
Interesting the 64 tooth gear was printed. Very cool. Was the gear driving it also printed? If not, were there any wear issues caused by the two different meshing materials? Was there any type of lubrication? (I would assume not, based on the fact its Nylon SLS, but figured why not ask.)
3 inch wheels are pretty small, based on how often we go through the 4 inch wheels, I am going to assume they probably wore fairly quickly. How often did you guys have to replace them? Did you find they wear faster than if you had put them on a tank drive? Would you guys swap modules out when you wanted to swap wheels, or just pull the shafts and swap the wherls? Trying to figure out what to expect in terms of how many times the modules will go on and off the robot over the course of a season.
It was my understanding and opinion that the suspension wasn’t super necessary. I was just curious what your thoughts were. Thanks for all the info! And thanks Mark for responding on the matter also!
The driving gear was a 44T VEX aluminum gear. No lubricant of any kind between the 44T aluminum gear and the 64T printed gear. We had no issues; there was even plenty of carpet gunk that got in the printed gear and it just didn’t care. We would likely experiment with printing the 44T driving gear in the future (would probably also change that final ratio to a 1:1 so that we could use a mag encoder stage on the VP. We have also discussed switching the VP to a VP lite potentially.
The wheels did wear. We tweaked values on auto as they wore, and generally replaced the wheels once per competition. Most of the wear the wheels saw wasn’t from spinning the diameter down, but radiusing the sides of the wheels from pushing through turns hard. This had a lot to do with more refinement needing to be done still on the steering control. The diameter of the wheel would wear over time, but it seemed to wear slower then your average skid steer wheel would, and this is what we expected.
When we did swap wheels, all we had to do was unscrew the 4 bolts that mount the forks to the module housing above, and the entire wheel fork assembly drops off. We always had 4 spare wheel fork assemblies at competition with new wheels on, so we could do a wheel change NASCAR-pit style in about 60 seconds by the end of the year (we used a drill with the clutch set to a certain value and a straight allen wrench in the drill to do this).
We used an absolute encoder too (not for swerve). They are nice because the position is, as the name implies, absolute. This means they update the position regardless of the program, even when the robot is off. So, if the module turns between matches, when the robot turns on, it still knows exactly where it is. A relative encoder needs a reference of some sort to determine its position off of.