We are getting the KOP this year. I’m wondering what add-ons/tricks you could do with the KOP. Something i just thought- since smaller OD wheels have smaller/less spacing between spokes, they are stronger (maybe not by much) than the larger OD (4 in vs 8 in). If the terrain is like 2017, could the KOP 6" wheels be swapped for the 4"?
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2017 was flat… are you talking about 2016? In that case, many teams that year actually used larger (pneumatic) wheels to avoid getting stuck on obstacles.
I did mean 2017. A completely flat ground meant you didn’t need larger wheels because you didn’t have to worry being stuck
I see, I misunderstood your question. My team’s never found any big issues with the larger KOP wheels’ durability on flat terrain, but maybe others have had a different experience.
Edit: don’t know what I’m talking about
The only problem with the 6 inch wheels we have seen is one team, who often started on hab level 2 with the normal kitbot, broke the plastic hub in playoffs. We had to switch them out for the alternate. Overall on a flat field I don’t see a problem with the durability of the KOP 6 inch wheels.
Plenty of stuff in this topic that’s still applicable:
including the original link to this: Bayou-Workshop-2018-KoP-Chassis.pdf (297kB)
The AM14U2 actually came with 4" white tread hi-grip wheels which would be good on straight carpet (e.g. 2014 Aerial Assist or 2017 STEAMworks) , but could not climb a 2015 Recycle Rush scoring platform, nor would it be able to climb to L1 for 2019 Destination Deep Space (at least not without some yeet). The clearance is about 1" most of the way around, but only about 3/8" at the gearboxes. I have a U3 mini-chassis I built with them:
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This is 500% incorrect for all released generations of the AM14U. 4" wheels are a bolt-on.
The AM14U (2014) and AM14U2 (2015) both shipped with 4" HiGrip wheels in the box. The AM14U3 (2016-2018) and AM14U4 (2019) shipped with 6" HiGrip wheels, but AndyMark has a guide for which holes and belt lengths to use for a given wheel and configuration. I believe that chart has been in the box for most if not all seasons, too.
Indeed, for a time a variant of the AM14U3 was sold by AndyMark that used 4" wheels along with a few other changes to drive down cost. (I know this because I led the AM14U3 Square Deal Edition project when I worked there.) The AM14U4 is very similar, and AndyMark sells an 8WD kit with 4" Performance Wheels as well as one with 6" HiGrip wheels. It would be trivial for a team to use 4" HiGrip wheels in either an 8WD or 6WD configuration, if desired.
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Thanks to all for getting the 4" question out of the way.
How do teams typically mount the battery in between the motors (effective defensive design)? For a team that doesnt have the machinery to custom cut?
If you take some spare end or front plate and rotate it 90 degrees (so opening faces up). Battery. Fits perfectly and just use Velcro to secure vertically. My team did this no issues all
Season.
I don’t think we’ve ever placed the battery between the drive motors. It’s nice to have it near the outside of the robot, so it’s easy to get to. Of course, the location depends almost entirely on the “stuff” that goes on top of the chassis, to handle the game piece(s). And that changes drastically every year.
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Buy these tee nuts: https://www.mcmaster.com/94122A200
Use them to install your wheel axles, then drill and rivet in place (making sure you have enough spacers so the pulleys miss the rivets). Never reach into your robot to undo the wheels again.
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The KOP axle is the bolt, what will be the replacement?
I’m not sure i understand this procedure either. Is it supposed to be a “WCD” KOP?
You use those instead of the nut on the inside.
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Not between, but down inside the chassis (low CoG, well protected) is easy! The AM14U3 kit made it trivial, but it turns out that you can do it still using two 6" pieces of AM14U4 outside rail and a piece of aluminum bar and a bungee cord. Here’s how I mounted the battery in my midget robot:
On the side at the bottom of the picture, I have a piece of wood as a standoff, and a piece of the old battery tray on the top*, and the aluminum bar I mentioned on the bottom. The battery slides into the chassis frame pretty smoothly but snugly into the end plate, as @risho900 noted above.
* mount these so the flanges point away from the battery.
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This is how we did it in the 2019 season:
This isn’t only good for defensive driving. Your battery is ~10% of your robot weight. Putting it in the center helps minimize the moment of inertia of the robot resulting in a better handling robot. It’s one of those subtle things that most people don’t notice. (Note: If your pivot point is not the center of your robot - say you have one pair of omni wheels, you’d want to center your mass on that pivot point.)
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On the inside metal plate, it would be the tee nut? And the bolt is still there? Picture if available please?
It’s not complicated. The nut goes where 3/8 nut always goes. You just rivet it in place once it’s there.
The image below isn’t the kitbot, but it was built the same way. Similar riveted nuts can be seen on the right two axles.
(On that note, the 8WD config of the kitbot makes wheel changes much easier than the 6WD)
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We didn’t. Spirit of Opportunity was flagrantly butt-heavy, between the battery and the arm being in the rear of the robot, but there was no safe or efficient way to package the battery more than an inch or two further forward. We used the stock AM14U4 battery mount dead center, with a custom surgical tubing strap for ease of securing the battery. Meant our wheel bearings were trash by the end of Smoky and a few demos, but that’s easy enough to fix (and good training for newbies).
We have used the AndyMark AM-2939 Battery Mount Kit for several years. We don’t use the bungee cord or the J-bolt. We install it vertically at the back (or front) of the robot. We screwed the side panels to the plywood botom using the holes that the J-bolt and bungee cord go through. The flat strip is installed near the top.
To retain the battery, we use a strap over the top of the battery. The strap is made from the “Extreme” Dual Lock from 3M. To attach the strap, we attach a 2" long piece of Dual Lock to each side panel. The strap is cut to be long enough to go over the top of the battery, engage with the full length of piece of Dual Lock on the two side panels and have about 1/2" extend beyond to act as a “handle” to release the battery. The strap is strong enough that one can pick up one end of the robot by lifting the battery. Unfortunately, I only have a photo of the battery tray installation from before the strap was installed.
You are correct that locating the battery in the middle of your robot will reduce the rotational moment of intertia.
Where did you install other mechanisms on your robot? Installing the battery in the middle may mean that you would have had to move other components towards the outside to allow access for changing the battery. This would tend to increase the rotational moment of intertia, partially negating the gains from locating the battery in the middle.