Note: this is accurate to our robot at the end of the season and includes the scab plates form where we had to chop the bot in half. (If you know… …you know)
We would not recommend hanging the electronics from a brain pan like we did. The shield to protect them was more than a pain in the back side.
We would recommend looking at the gripper for an excellent example of how to make a good quality ultra light weight roller system. The gripper was exceptionally rigid and extraordinarily light weight. There was probably some opportunity to remove even more weight from the system with more aggressive pocketing.
We would consider using the linear sliders on the extender again, but would want to be able to replace them from the outside without needing to unmount the side plates. overall we only had two needle roller failures over the course fo the season which was much better than what we saw last year with the GreyT Telescope where we had a Bering failure every other match or so.
Our CAD shows the use of Rev Ultraplanetary gearboxes on the extension and wrist joints. We found them to be insufficiently durable for those applications, but had no issues with using them on the gripper. We had replaced the wrist motor with a 550 driving a Versa planetary and had success with that. Our season ended with a failure of the extension ultraplanetary gearbox.
As always our code is never hidden and available here:
We started rocking a brain pan last year, and had the total opposite experience: we absolutely recommend it to everyone! What specifically about the shield plate made this not work for 131?
From your CAD it seems like your shield was significantly more beefy than ours - we just used a piece of 1/16th polycarbonate which we velcro’d in place.
We loved your robot as always this year - it was awesome to finally play with you all at BOTB!
Our shield was also our ballast. We started with a piece of lexan using automotive push button latches but found they did not have the necessary durability. They were ripped off our robot several times. When we went to address our CG issues after Week 1, we opted for 1/8" steel. The steel belly shield was held onto the robot with captive lock nuts (would use that again for semi-permanent installations such as bumpers. We needed the attachment method to be rigid enough for us be able to fly over the charge station and land on a cone without loosing the ballast. That meant we held it on with #10-32 button head screws. The ballast plate that was the battery box had 8 screws. The other had 4 screws. It was just a pain to need to use a drill to remove the cover to get at the electronics.
Unfortunately, these were a mid-season upgrade to the robot, so the CAD was “Just good enough”. To help with the explanation, I have made this Part Studio:
We created these aluminum blocks called “Nut Holders” or “Pocket Nut Holders”. They have holes at 0.5" spacing between the 3 holes. For most applications 1" would work better so it aligns with the COTS tubing spacing, but we were space constrained.
The Middle hole has a receptacle for a #10-32 lock nut. The endmill reliefs are selected to allow some lateral motion in the nut to help with assembly tolerances. This was designed to be made with a 1/8" endmill. The outer holes are tapped for #10-32 Screws.
Here is an example in use. There are two basic configurations that may make sense depending on the use-case
The one we use last year was the flush-mount with the plate inside the tubing. This allowed belly plan to sit against the tubing and is more appropriate for high-load instances where a stabilizing effect between the two pieces is important. In this configuration the clamping force does not go through the Pocket Nut Holder, which probably has an advantage on longevity.
The other option is the stand-off configuration where the block is between the tubing and the removable component. This configuration is easier to install. If I were to implement this option, I would probably make the Pocket Nut Holder a touch thicker. (5/16" or 3/6" total thickness rather than 1/4")
In both cases, the threaded portion of the lock nut should point towards the removable component.
We used these for most of the season including a boat-load of offseason events. We had them on the bot for our 2nd event.
Thanks for the part studio and explanation. Were these only installed near the ends of the tubes, or did you fish them into the middle of the tubes as well?
Installing them half-way through the season was a bit of a headache. We ended up needing to use a hand router with 1/8" carbide bit to make rectangular access holes in the tubing so we could get them where we needed them to be.
After some practice we came up with a technique that used a piece of wire and tape to get them where they needed to go. Would have been MUCH easier if we didn’t have the swerve modules and supports blocking the way
