There were some teams that had similar issues from side impacts from the cable protector last year. When being defended against, they were shoved over the line sideways and had part of their omnis broken.
Our worry was balls getting caught up in those slides and having to get a running start going over the 2x1s. Let us know how it works in practice!
Our team will also be spending the next two weeks investigating solutions as well. Our rear, Andymark higrip wheels were shattered in much the same way via defense and side loads during a match. No problems just driving.
This is one of the reasons we built a low bot, and I’ve instructed my drivers to enter the rendezvous point only if/when absolutely necessary and to climb–drive trains are taking a beating trying to go over those bars at speed.
For what it’s worth… a year and a half ago we ran a fully loaded robot with some corner omni’s and center traction wheels at a state fair (off-roading it!) for several hours, and walked away with all of them broken. Granted, they were 10+ years old at that point (we replaced the rollers earlier in the year, I believe)! I doubt there was much side load at that event, as we weren’t interacting with other robots, just driving, but the ground was very uneven!
We were using a set of the old aluminum 6" double omnis from Andymark on 1740 for the back pair of wheels on an 8WD KOP chassis. After 1 day of matches with plenty of high speed runs across the bars nearly every roller on the wheels was seized due to damage. The wheels at least held together fine and continued to operate as low friction traction wheels, but they not longer operated as omnis.
For our 6 wheel West Coast drive variant, we realized the omnis would take a beating from those bars and put them in the rear of the bot. It made the turning point a little odd, but the drive team quickly got used to it.
The wheels survived nicely.
One thing we also noticed this past weekend from the bars on the floor, that it was literally rattling battery cables and power cables on the breaker loose. We kept going around to the teams in the pits and either checking their wiring, or reminding them to keep a close eye on this. So it’s not just wheels that are taking a beating…
We experienced similar issues in 2015 when our rear omniwheel would hit the platform when driving on to place a stack. Here’s a drawing of a plate we made to mount to the 4’ VEXpro Omniwheels. That wheel has been revised by VEX since then, so this plate may not fit. Regardless, the concept should provide ideas for reinforcing any brand of COTS omniwheel.
Just to set the record straight neither of these have been discontinued, we are simply out of stock of the rollers so we are unable to build more wheels at the moment. We should be getting more rollers this week as they are made local.
Our robot has mecanum wheels and initially I instructed my drivers to to only cross when necessary, but after seeing them go through without issue, I gave the OK if the trench is blocked.
You can see 8002 run through with a little reserve in this video.
Imo, i would think Mecanum wheels would dent before they break as they have metal sides, not plastic. Correct me if im wrong.
We ended up machining some outer plates from 1/4" thick aluminum (6061) in the same pattern as the Andymark higrip wheels. We installed them onto the hubs, put the robot up against the rail with the plate contacting the rail. We then ran out practice robot into it. On the 4th hit, the plates bent. I suspect it would hold up mostly in competition, but we decided to go with pneumatics all the way around since we haven’t been able to destroy them. We tried a drop center (3/16") but found turning to be compromised more than we wanted. So we made the rear tire slick and that satisfied the driver the most.
We ran 4" Vexpro omnis on the front end of the robot at the Utah Regional this week without incident. We changed them going into finals out of caution, but our rear colsons and center nitrile aluminum wheels needed change much worse (see picture).
This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.