We just have 2x M3’s holding each end. There’s very little sag so we probably won’t do much more.
Protein bar? You know, for them gainz.
Where do you guys source your polybelt? Your manipulator looks amazing!
Conveyor Belts, 2" Wide
Do you have documentation for splicing the belting together? It always seemed tricky to get 1" Polyurethane belts consistent, I think 2" would be worse.
Build Update 2/9/23
Started getting some more serious practice time in today. Starting our focus on clearing unscored auto pre-loads from the mid zone before we move into full court cycling next week.
Currently can clear the ‘worst case’ 6 cones/cubes in 1:20. We do not yet have the first wave of our driver assists up and operational, but should have those this weekend/early next week.
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112 Build Update 2/11/23
We got our first cycles today!
In the video, I’m driving (I’m not our actual driver) and also we didn’t have field-centric swerve on at the time so please excuse my poor driving XD
We didn’t get any videos of scoring high cubes, but we can. We also don’t have any ballast and still weigh around 73 pounds, so just a little bit tippy. We can’t really move the arm while moving, if we have ballast we may be able to.
At the end of the video there’s a closer look at the intake and claw extending and retracting. An interesting thing is our working pressure is at 40 psi instead of the maximum 60, so we don’t grip onto cubes too hard.
Right now we can intake with OTB, but we want to add a feed in. We don’t have it fully designed yet but we should have it done by the end of next week. We don’t have too much room for driver error while picking up cones, but hopefully software can fix that.
We’re going to be swapping out operators quite a bit for now until we have operator tryouts later this month, but we have our driver decided. I’m very exited to see how well we can do!
Is that top sprocket 3D printed?
The sprockets are REV 48t sprockets, however we have 3D printed connectors to the sprockets. Here’s a low res photo that I was able to find and a photo from the CAD. Makes spacing the sprockets pretty easy.
This past weekend on 111, we took a step back in order to take two steps forward
The robot has some durability issues. If the arm is horizontal and the robot quickly strafes or rotates, the resulting torque placed on the carriage can pop it out of the lift. This issue only gets worse if the carriage is in a raised position. While we can limit the robot’s speed while the arm is extended, we don’t want to worry about a bump from an alliance partner or defender causing damage to our robot.
Our solution is to replace the side roller bearings on our carriage with the DryLin Igus sliders. You may recognize these from the KoP. These will mechanically lock our carriage to the moving stage of our open top lift. Each slider can handle 157 lbs of static loading in all directions and we will have two on the each side of the carriage. We started implementing this over the weekend and the results are promising.
Igus makes a variation of these slides that allows for +/-.02" of float in the horizontal and/or vertical direction. To avoid over constraining the carriage, we only want the sliders taking the side loading forces and moments. Anything in the vertical plane will still be handled by the cam followers. One side of the carriage will have sliders that allow float in the horizontal direction. The other side of the carriage will have sliders that allow float in the horizontal and vertical direction. That way when our lift tubes aren’t perfectly parallel, we won’t bind the lift.
Rapid fire question time.
How are you figuring they will hold up to shock loading from impacts when the forces want to pull the slider out of the igus rail? Do you suspect a pair per plate of these sliders will be sufficient? How do you intend to test these/replace these over the season (i.e. will the act to examining/replacing/maintaining them cause sensor clocking issues)
This is a good thing to find out now about durability issues, since your robot has already been built.
We are in the same position as far as extensive testing, and on 2nd or 3rd iteration of subfunction parts.
Robot looks great. Hope to see it all work out at your events!
Eh, its high school robotics. We’ll drive it like we stole it and see what fails next!
Fair. Give ‘er the good ol’ shakedown.
The robot’s composite arm presents another durability and serviceability issue. Currently, the 3D printed end caps are epoxied into the carbon fiber tube. If we break an end cap, that tube is scrap. To allow for servicing, we are going to switch to hot glue. Then we should be able to use a heat gun to melt the adhesive and remove a broken end cap. Allowing us to reuse the carbon fiber tube.
At first I didn’t take the idea of hot glue seriously, but some quick math proved me wrong. I found the shear strength of hot melt adhesives listed in a range of 100 PSI to 250 PSI. We probably won’t achieve a maximum strength bond, so I’ll use the 100 PSI value. Our end plug has a surface area of around 8 in^2 and a radius of 7/8 in. That gives our joint an axial strength of 800 lbs and a torsional strength of 60 ft*lbs! We expect this to be adequate, but need to get a few hours of practice in to be sure.
2767 has used hot glue on carbon fiber joints for years. 10/10 recommend. We add “ribs” to provide more surface area for the glue to cling to. We also started adding glue holes asking one face of the part to pour directly into the part.
Yeah, we definitely cribbed this design detail off of you guys.
We are currently using this generic brand EVA based hot melt glue: McMaster-Carr
With this (super awesome) hot glue gun: McMaster-Carr
One other thing that changed in this design. Because the plugs are now serviceable, we could significantly ‘choke up’ with the CF tube on the wrist joint. This greatly increases the stiffness of that joint and prevents the ‘lean’ that occurred in the previous design. This also helps mitigate the effects of creep over the next couple months as the onyx joint will be held under a static moment load due to the belt tension.
We retained the bolted joint at the base to make swapping entire arm/gripper assemblies easier. We intend to build a spare of this assembly so we can repair the arm while still having one on the robot. Keeping the bolted joint allows us to swap arms without getting a heat gun near the robot.
I noticed you have a " robot_framework" repository public on your GitHub. Is the 2023 code for Team 111 also public?
No, the code for 111 and 112 is not public - we’ll be doing a post season release after we get a chance to sort through and sanitize everything after competition season. We’re keeping it private partly for strategic reasons, partly for student’s privacy, and partly because it’s a lot of work to manage/organize/review code from 30 students on 2 teams over the course of a season without having to ensure every commit is appropriate for public viewing.
If you have any questions on anything specifically (and this goes for anyone), feel free to ask and I’ll respond as able with code snippets, logic, or screenshots. We’ll also have the robot framework updated with our swerve code, and some autonomous driving once we get around to that in a week or two.