Interesting AM14U2 and AM14U3 upgrades

As part of the Bayou Workshops on 27 October, I’m doing a presentation on “making the most of the Kit of Parts Chassis”. I’m going to assume that the kit this year is the AM14U3, or an evolution of it similar to the transition from the U2 to the U3 - or that the team prepurchases a U3 and “opts out” of the kit chassis. I plan to show what 3946 has done with the U2/U3 over the past four years, and I know of a few other really interesting things, like the KitBot on Steroids and that crazy Meckiwiin 2015. I also want to present things which are appropriate to relatively low resource teams, who have a drill press and band saw (or hack saw) and somewhere between zero and $450 to spend on chassis upgrades. I’ll also include some tips on mounting VersaFrame manipulators onto the KoP chassis.

Please post links to pics and descriptions of clever, low cost upgrades to the recent kit chassis here. In return, I’ll post my final presentation and pics of my demo items shortly after the workshop, either in this thread or as a white paper.

I designed pretty simple flipped-CIM and flipped-MiniCIM gearboxes that direct-mount to the AM14U3 a while ago. I never actually built or tested them, so I can only vouch for them in theory. But they should be the kind of thing that a low-resource team could make use of (if they can find a sponsor or higher-resourced team to cut the plates for them).


This is great. I’m glad you’re working on this sort of presentation to show teams cool things you can do with the AM14U family of chassis platforms.

If it fits with your presentation, there are a bunch of upgrade kits and parts we offer for the AM14U family of chassis (some legacy AM14U and AM14U2, most primarily for the AM14U3,) that might be worth looking at - depending on budgets of teams.

If you’d like any specific insight of other stuff about the chassis, feel free to DM me or post here. I’d be happy to answer that sort of stuff if you need that for creating your presentation.


I am planning to restrict to things a team can build from COTS parts, a saw, a drill press, and hand tools.

Absolutely, this was part of the plan. I was going to start with the basic kit (and why it has six wheels), then things involving only belt, gear, and wheel swaps, then move on to the COTS options (e.g. frame opening, wedge plate, alternate gearboxes), before moving off into a few crazy mods. If time allows, I’ll also do a few minutes showing a simple technique for mounting Vex Versaframe based manipulators securely.

Anyway, now that this discussion is underway, I’ve been wondering for a while about the Mezzanine. There does not appear to be any way to cleanly mount this to the U3 chassis without additional hardware, or possibly by assembling with the risers inverted. Updating the kit and/or drawing to include mounting to the current chassis would likely make this a more attractive option to teams in the rush of build season.

We used the AM14U chassis in 2015 and 2016. One of the best upgrades we made was to mount the corner wheels ontube axles (drilled out to 3/8" bore) (edit: you could also probably use this tube stock). Then we riveted on these panel nuts on the inside plate so that you could change out the corner wheels without having to hold spacers in place or get a wrench into the frame to hold the nut.

I also recommend these clip-on nuts for attaching upper structure and bumpers, again without having to reach a wrench around for a nut.

Yeah, this kit definitely needs an update/replacement. It was originally designed for the first-gen AM14U.


We also used sleeve axles in 2016 STRONGHOLD, but this was only of benefit because the center wheel almost never did any work (it was a 4" wheel where the others were all 8"; it was there mostly to help us get off of the edges of the moat) and we had to do so much work on the chains. Why did you have to access the corner wheels more often than the center ones in 2015 and 2016?

I like the panel nuts. IIRC, we at least partially solved this problem in 2016 by using coupling nuts between the sheets, with bolts coming in from both sides.

Great idea! We’ve used rivnuts for this in the past, do NOT recommend, as after a few dozen cycles they may start spinning, making a real mess. For these clip nuts, how big do you have to bore the hole in the chassis to get them to seat?

Reminds me:
Does anyone have a solution better than rivnuts to secure the outside sheet? Just about every competition we’ve had to remove at least one to swap a wheel or motor or belt or something, so the stock screw and nut doesn’t really cut it unless you have a fancy socket tool. It looks like the clip nuts don’t lie flat enough to let the outer plate fit into the end plates.

One of my favourite upgrades to a kit-bot chassis is to mount two parallel aluminum extrusions to act as a base to whatever mechanism they plan to mount. The rails can be longitudinal or transverse, but I find the extrusion to be a flexible means of attaching something to the chassis.

Your other option would be Vex VersaFrame, which would be well suited to a team with equipment limitations.

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This is really cool!! I’d love to see a picture of how these work in an FRC context- if they work how I think they do you may have just solved our bumper problem that our team has had for the past 3 years.

Could you please put this stuff up here, as we are a rookie team who fits this profile, and are building an offseason bot whith the AM14U3 square deal edition and competing on october 27th, so we could use a lot of this information.

That’s how we attached our bumpers. There’s nothing really to it. Pick the hole you want to attach to (must be 1/2" or less away from the edge of the sheet metal). Drill it out for 1/4"*. Clip the nut over the hole (like this video, although these aren’t exactly the same nuts). Line up the bumper bracket over top (you might need a small screwdriver to pull everything into line). Install the 1/4-20 fastener (we use a drill with a socket to make it fast).

*if you drill the hole for ~5/16", the clip nut has a little retaining feature that keeps it centered in the hole so you don’t have to re-line it up each time.

So then are the bumper brackets attached to the wood of the bumper and come off when you switch bumpers?

This was just a quick CAD I did up. the L bracket is attached to the bumper and then it just bolts onto the chassis. The clip is on the chassis.

Hope this helps :slight_smile:


Wow thanks a lot. That actually makes bumpers easy

Those are nice, though it’s frustrating that they don’t have them in 10-32.

The last time I put bumpers on an AM14U3 (on 5402 in 2017), we simply put some #10 screws going upward through the frame, put a hex nut on to capture it, and then wingnutted the angle aluminum bracket in place. You can see the studs and wingnuts in this picture.

The only issue came when we got to putting bumpers on the Mk. II version, as the gear pocket interfered with bumpers and we needed to split that bumper mid-season. We could add a second stud on one side (which was reasonably easy since we had ripped off the back of the robot in installing the gear pocket), but the other side couldn’t fit one in with how we had the battery. We ended up having to tap the outer face of the AM14U3 end sheet, use a button head screw, and hold our breath. I’m not sure whether that was 100% legal or not, but it made me queasy enough that I wouldn’t want to do it again.

Mind you, that issue has a root cause of “we went big on fuel in 2017”. For most teams and years, you’ll be fine. :slight_smile:

I am just getting started putting this together, so the presentation post won’t be until too late to help you.

The “why six wheels” is covered in the drive system primers I previously posted here.

The “stock” options are well documented on In particular, read the parts of the kit chassis assembly instructions which deal with different belts and gears and wheels, then follow the link Nick posted above and look at the chassis opening and alternate wheels (pneumatic, mecanum, etc).

Most of the “creative” options are likely beyond what you’re going to want to use in a month for FIRST POWER UP↗. If you’re planning to build a robot that can score in the scale, you’ll likely want to make the robot base as large as possible/legal and keep the center of gravity low to reduce the likelihood of tipping. If you’re looking at an exchange/switch bot, you may want to do something similar to what 3946 did with the post-season robot. By making the chassis small and light, it could accelerate quickly and get things done (the small blue robot that stuffs the exchange, steals cubes, plays defense, and works the switches). Remember that if you only have four wheels, you want your track width to be greater than your wheelbase That is, if you put dots where the four wheels hit the carpet, you should have a rectangle that is wider left-to-right than it is long front-to-back. A low C.o.G. is even more important for a small base.

Attaching versaframe, quick and dirty explanation: Get some versaframe 1x1 channel , as well as whatever your actual manipulators will be made of. Bore out the holes on the central face of the channel to 3/16". Cut to 3" lengths (or longer). Bolt or rivet these down to the holes in the top of the KoP chassis. Rivet gussets onto the side faces, flanges pointing up, and build your manipulators. You can see this technique here; those 3" segments stick up about 1/4" above the bumpers over the 9 and the triangle. Those are mounted to the inner sheet, but will work with end and outer sheets as long as they don’t interfere with your bumpers and frame perimeter definition.

It might be worthwhile trying these. The setback on them appears to be 3/16". The top flange of the end sheet is twice as deep as this, so no go here without cutting the flange. The top flange of the outisde sheet is only 5/32", and looks like there is enough room for it to fit underneath. If they’re thin enough, they may solve the “removing the outside sheet” issue. I’ve placed an order (slow shipping); will follow up in a week or so.

I definitely recommend this. It is much easier and more repeatable to mount the brackets to the bumpers and secure these to the robot than to use the tee-nut solution. It’s too easy to push a tee nut out, especially after repeated removals and replacements, and repair means taking the bumper apart.

If you really want the threads in the bumpers, I’d recommend threaded inserts that have female machine threads and male wood screw threads and mount on the frame perimeter face of the bumper lumber rather than from the noodle side. You can get these at a hardware store in several sizes; #10 is most common for bumper mounts.

During the day, away from my computer, an interesting thought occurred to me.

Many maintain that they can drill out a rivet faster than remove a bolt and nut. Has anyone ever riveted bumpers onto the robot, knowing they would have to drill them out and replace every time they change colors? If so, kitbot or not, how’d that work out?

As I began preparing my powerpoint slide deck a question occurred to me: How far back does the KoP chassis go, and what did it look like in the early years? The earliest mention I can find of it on CD is 2005, but it is just a couple of mentions. I know that the 2012 and 2013 KoP chassis were essentially the c-frame chassis that AndyMark still has for sale. What happened from 2005 to 2011 (and before that if my search missed something)?

Also, what other “kit chassis” are currently available that are likely to work at an FRC scale? I just want to hit these quickly and move on, but be complete as I can as I do so. I know that the AM14U3, AM C-channel, AM Nano Tube, Vex VersaChassis, and WCD chassis are out there.