We here on Team 48 decided to design and build a turret for a ball-shooting mechanism for our 25th anniversary robot, xtremachen25. This was the first time we ever put such a thing our our bot. Better late than never, right? We also did not like the right-angle COTS packaging options for climber gearboxes to pair with our dual AndyMark Climbers In a Box (which both worked just fine #ad). Add to this our obsession, for once in our existence, to have a robot weigh significantly south of the weight limit and our possession of 2 Markforged printers, and we said “Why not? Let’s have some fun!”
So we went a bit Onyx crazy. Here is what resulted. The herringbone gear pattern you see in the turret and climber gearbox were employed with reliable success at Finger Lakes. Additionally, the robot weighs around 118 pounds, which it turns out is plenty enough to add our 2nd set of hooks for higher rung climbs, along with a few other mods.
Here’s a Behind the Glass video of one of our qualifying matches where you can see the turret and climber in operation: https://youtu.be/Wh8XLmzMAYA?t=74
We had a lot of new things and new people to get up to speed at our first event, and competition results didn’t end up the way we would have liked, but we are excited for the potential of this robot and drive team. We’re back in the shop tomorrow to begin upgrades and further practice. I am very much Looking Forward to competing at the Buckeye and Midwest Regionals to see what we can achieve following some iteration time.
I will be posting the complete CAD to GrabCAD sometime in the coming weeks, once we are done making changes throughout the competition season. If anyone has questions I’d be glad to answer them here or on the aforementioned post containing links to our pack-n-go’d “final” product.
Very surprised those plastic gears are holding up in the final stage of a climbing gearbox. But risks sometimes pay rewards! Can you estimate the tooth bending load?
TBH, I didn’t bother to run the math in the process of the build as this is more or less an experiment* with direct replacement WCP/VP gears waiting to be swapped in. So far with one competition (with limited climbing) and further practice at home we’ve had no issues. We likely will be inspecting them again tonight as we have been attempting to implement our traverse hooks.
I’ll have to blow the dust off my college machine design text book or look through my old revision AGMA standards and work out the approximate numbers.
*I had already made the turret gears parametric so it took all of an hour to make up 4 gears for this application and get them printing. We don’t keep much stock of WCP/VP’s gearing and were concerned with the lead time to acquire the direct swaps.
All of those numbers are about right. I’m trying to remember the PD I used for the final stage off the top of my head. It is either 8, 10, or 12 for a 32T output gear. So, 4", 3.2" or 2.66" diameter respectively.
No insert, we have two shells of continuous CF in the walls (4-6 walls of Onyx) of the hex bore and it extends into a hub for a total hex face width/bearing area width of about 1.125" to prevent blowout.
We won’t speak of the evils of Buckeye, but we believe the full traversal climb is finally ready for primetime at Midwest.
The herringbone printed reinforced Onyx gears continue to perform well. Our only major maintenance requirement so far was to swap out the locking gear our metal climb lock dowels press into. We observed some wear there. We could probably just clock the gear 180 degrees and use it again, but why risk it?
The carbon fiber rod secondary climb hooks can be added to the “things with lots of 3D printed parts that scare me” category. The upper hook clamp and the lower clamping pivot bracket are reinforced Onyx. I believe at FLR, I weighed both hook assemblies (at the time without actuation cylinders) at 1.7 lbs. total.
All hook pivots have been coupled to the main frame via beefy reinforced Onyx brackets this entire season - the OG brackets are still on there and rock solid. That continues to boggle my mind, especially after some of our more “interesting” prior climbs. But these light 3D printed systems are slowly convincing me to trust their use in higher-load applications.
In other news, we also added something to our shooter (visible in the video) that makes it behave much better (famous last words).
It’s been great fun on our team this season seeing how many New England and other teams have ended up with some form of herringbone gear application on their robots. At least a few of us have postulated that our visit from Ohio to Battlecry last summer may have contributed to this proliferation in at least some small fashion, for at least a few teams.
I’m not looking to “quantify inspiration”; I’m just genuinely curious if anyone who was at Battlecry (or elsewhere who read this thread in 2022) decided to add 3D-printed herringbone as a result of their interaction with our team, either directly at Battlecry or via this thread.
Herringbone wrist joints, in particular, seem to be very popular this year #sidewaysturret
