VEXPro - After the season

Do you have a snapshot of your wheels with wear?

I don’t have any good pictures from our comp bot but I have attached a couple from the practice robot. They are not nearly as bad but still worn. That last picture is a new wheel for comparison.

If their wheels have worn as ours have, the taller ‘points’ of the tread will gradually wear down and begin to round until they’re even with the shorter ‘points’ of the tread. From there, the wheels seem to wear evenly - the points begin to round and will gradually get smaller until (I assume) they will more or less go away completely.

We first noticed the wheel wear after our first event, and rotated our front wheels to the rear to attempt to even out the wheel wear. From what we’ve seen, the wear may cause a minor decrease in effective COF when pushing forward, but not enough to be too worried about.

If there’s an opportunity, I will get a picture of one of our more worn wheels on Thursday Morning and report back. It’s also worth noting that we’ve played ~40 competition matches, maybe 10 practice matches and have a good 6-8 hours of additional run time on our competition robot’s wheels. Odds are, a large majority of teams won’t see this amount of run time until the Championship or after, so wheel wear may not be an issue for them.

*Edit, Allen posted pictures of 3847’s wheels… If anyone still wants more info, let me know…

I’d like to see your photos too.

My concern is we ran FLR with a rock in our drive train, and for buckeye we took out the rock. My concern is that we have run 4 traction wheels in the front and omni in the back. We have the omni level or raised. Will the worn down wheels gives us a greater rock as the competition goes on?

1712 used 6x VersaWheels, 1x 10:1 Versaplanetary, 1x BAG motor, 2x VersaHub (1/2" Round w/ 1/8" Keyway), 1x 60t #35 plate sprocket, and 1x 48t #35 plate sprocket.

The #35 plate sprockets:
Light weight, affordable, aesthetically pleasing, didn’t fail in a relatively high load application (shoulder joint for our arm). No complaints.

The VersaHubs (keyed):
Would be convenient if alternatives to #8 screws were offered, in order to facilitate the possibility of transferring torque via the screws. Otherwise, no complaints.

The VersaPlanetary:
Our resuts seemed to run the middle of the pack with these. Useful, no significant issues, but not quite in love with them either. The variety of different sized screws required to mount the motor was confusing (both metric and imperial, really?). The motor shaft adapters for the AM-9015 didn’t match the pictures in the assembly instructions. Additionally one of our students managed to snap the 775 adapter on our spare when tightening the set screw. Also, our spare binds when the mounting screws are fully tightened, so we have to leave them slightly loose. For some reason, this behavior differs from the gearbox on our robot.

The BAG motor:
We used a BAG motor through a 10:1 planetary for our initial shooter wheel at our first event. It held up just fine, but developed the open circuit issue during our unbag after the event. We have since replaced it with a AM-9015.

The Versawheels:
Overall, we love them. They provide subjectively good traction at an incredible price, and we haven’t had significant issues with them. While we can’t necessarily shove every robot we face out of the face (we can with a good chunk of them), we have only been displaced by two other robots the whole season (and one of which was while we were still <100lbs, and the other we were still ~110lb, both weights not counting batt/bumpers), 225 (6 motor drivetrain) and 2729 (2 speed drivetrain in low gear). Neither was able to move us with satisfactory speed either, ultimately resulting in them giving up and trying to drive around us.
The one comment we would make would be in regards to the description not mentioning the wheels are designed to be used with flanged bearings. We did not used flanged bearings, and one of our wheels has a tendency to visibly shift on top of the bearings when a side load is applied.

So far (after only one event):
Drive in a Day Chassis-Awesome. Easy and quick, and we were able to mess with it as we wanted, ie. we got our own laser cut “sideplates” to raise the chassis up a few inches(this was to put an intake that we ended up abandoning).

Ball Shifters-So far, they’ve been great. The only issue we’ve had was the output shaft coming loose(it happened on probably 3/4 that we’ve had…but only once during an actual match), but that is easily fixed. The shifting is great, and combined with the sprockets and VersaHubs, it’s so easy to change things to get any desired gearings.

MiniCIMs-we were originally using these on our shooter(we changed for purposes of wheels; nothing to do with VEXpro products themselves) and had virtually no problem with them.

BAG Motors-We’re now using these for our shooter, and have yet to see any problems with them(in practice that is). We were originally using them on our intake, and never had problems with the motors themselves…hopefully we don’t experience the problems people are talking about with them…

VersaPlanetaries-THESE ARE AMAZING!!! Changing reductions and motors has never been so easy, especially compared to needing pinions with Banebots gearboxes…We have one that is 15:1 with a 550 on our hopper and that has given us virtually no problems. Our shooter now is running BAGs 1:1 with them, and the only issues so far have been: on some of the gearboxes (4:1s I believe…) the little pin next to the assembling holes(I have no other way to figure out how to describe that) didn’t line up, and we weren’t able to make 1:1 gearboxes out of them. Also, occasionally, the screws that mount into the BAG motor have come loose. We retightened it and so far(after running them a large amount) they have yet to come loose. Also, the E-Clip on the bearing for the input…we also had the issue described above where the mounting collar flat out broke upon tightening the set screw too much…we also one had the bearing of the output fall out…

Traction Wheels-Great so far, nothing has gone wrong with them, except it’d be nice to see a simpler way of mounting tread, similar to the new AM Performance wheels.

Overall, VEXPro has been awesome stuff that definitely gave us a top of the notch drivetrain this year.

Here is the best I can do at the moment- this is a screenshot from one of our on-board GoPro cameras. The motors are attached using the mounting holes for the mounting plate as these are located on a 2" bolt circle. The threads were drilled out and two 10-32 bolts were used to attach the MiniCIM. The bolts were Socket Head Cap Screws. The bolt heads had to be machine to a smaller diameter to allow them to fit into the rear of the planetary. The shaft on the MiniCIM was also shortened to about 3/8" so that it would not impinge into the VersaPlanetary. We also inserted a 2mm keyway instead of relying on just the setscrew to hold the shaft.

It’s hard to say without knowing the exact specifics, but if you experience wear like we did, it will have an effect on how the robot appears to ‘sit’ on the floor.

In our case, we found that the wear on the rear wheels was enough to cause the front of our robot to sit up from the floor ~1/8" or so - making our intake appear to not work as intended…

One easy solution to the wear problem is to periodically rotate the wheels between ends/corners/etc. In our application, an 8WD with .090" drop on the center two wheel pairs, we’ve found that the rear most pair and the rear center pair wear the fastest (under the center of mass), the front center pair wears a bit slower, but not by much, and the front wheels barely wore at all. The simple solution was swapping the front and rear wheel pairs between our week 1 competition and week 3 competition. Luckily, our drive is set up in such a way that it allows for wheel swaps in less than 2 minutes or so.

Yeah, Understandable.

It’s not a quick thing to change out wheels for us, probably about a 20-30 minute time frame. I was thinking about buying a pair and making the secondary chassis of this years bot with the vex wheels. The 2013 chassis is the best one we have made and we have spares of just about all pieces.

Are you running 8wd?

Thanks for the information.

Well, we did have a loose piston, but the issue was actually due to a poorly assembled power pole on a Jag. That side of the drive train was driven by only one CIM during that match because that one Jag wasn’t powered.

The piston was probably loose all day before we noticed it. The Ball Shifters worked well even with one of the pistons hanging on by a few threads.:slight_smile:

We used the 8" VexPro Mecanum wheels this season with 1/2" round keyed VersaHubs and were pleased with them. Our robot only competed in 1 regional event but we never had to use any of our spare wheels or rollers. Our students loved not having to spend hours assembling them like last season and I loved the multi-pound weight savings we got in our drivetrain by switching.

And for reference, they just barely fit on the Andymark Nanotube output shafts for direct drive (I don’t think we had to get the longer shafts, but that was a while ago).

We had several of the VersaPlanetary gearboxes on our robot and we liked the easy configuration between shaft output types and the multiple motor inputs.

The biggest issue we had with a couple of them was we stripped the hexagon socket set screw that tightened onto the motor shaft. I haven’t determined if this was the students using worn hex keys, incorrect size hex keys, or what. If we tried to take the set screw off, the internal hexagon socket became damaged so that we couldn’t remove the set screw. Maybe a different quality set screw would eliminate this problem.

We used several VP gearboxes this year. On some (but not all) we found that an M2.5 hex key fit better than a 3/32", which is the size indicated in Step 3 on p. 8 of the VP User Guide. Probably a higher quality set screw would help fix this variation.

We have been using the M2.5 for most of ours and they have’t stripped at all. I’m probably going to find a source for better set screws in the future and just replace them all.

I’ve also found some other variations in the gearboxes. I think we have bought around 12 of them and on occasion they don’t have the alignment peg thing at all in one or two of the stages. We also had one of the snap rings come off and drop our shooter wheel to the floor. It was a quick fix but it did happen once. Like I said before they amazing and I wouldn’t trade them for the world but they do have the occasional small problem.

Preliminary Data:

Single Speed 12:64 Gearboxes with 30:50 VEXPro Gear post reduction
The didn’t go together smoothly – the 3/8" bearing wouldn’t accept one side of the output shaft and the 1/2" hex bearing was too snug a fit for the other end of the shaft (started stripping the annodization off the hex corners). Used AM bearings in both cases to solve it. On the two VEXPro gears after the gear box, the annodization is wearing off fairly quickly – possibly due to imperfect alignment, but the wear is even across the teeth. Will probably use the double reduction gearboxes next year, even though I liked the versatility of choosing custom gear ratios. Or we might use Gates or AM belts. Who knows. We really like all of the mounting options of this gearbox though.

22T Hex-bore Sprockets
We are using these in our drive train, geared for 12 ft/s. It’s a typical 4WD WCD, with these sprockets transmitting power from front to rear in a 1:1 ratio. We’ve been hit hard twice, and both times had one of these sprockets eat itself a few seconds later while driving. It’d be nice if someone also offered a steel version that was hex broached. The first time we thought it was because the wheel block slid on the impact; the second time we verified that the block didn’t move (so the chains were in proper tension the whole time).

Hex Shafts
We got the hex shaft stock, then sized them for our WCD drive train. Found that the shaft isn’t perfectly straight nor an exact consistent diameter even over short runs, meaning that it doesn’t “just work” with the hex broached VEXPro items. Sanding down the corners helped. Could have been a shipping / temperature thing. We have had the same issues with every hex shaft stock we’ve purchased. Imperfections were on about 50% of the shaft length, so about half of our shafts still have their nice annodized corners.

VersaPlanetary (Single Stage)
Used with BB-550 and AM-9015. Aggravated with the assembly. We’re swapping a 550 out for a 775 to get a better PID responds on our tilt, so we’ll see how the assembly works there. We also stripped a 9015 collet when a disc jammed early in the season, rendering the piece useless. We had a spare from the other transmission we got, which was a plus. I do like the interchangeable gears.

It’s nice that the bolt pattern remains the same. It’s kinda funny – we have this hub and an AM hub on the shooter wheel since that was the best spacing configuration :D. Very nice for quick prototyping overall. We enlarged the holes for a #10 bolt since those are the smallest bolts we have in enough variety of sizes to do the prototypes.

Generally a mixed bag. May have more to say after Chesapeake & Champs.

As a meta comment to all FRC suppliers this year I will say that one of my bigger frustrations has been with all things hex.

Finding straight, well-toleranced hex shaft that has a decent fit on runout- and wobble-free hex bearings/gears/sprockets has been a real pain. We had to mix and match hex products from VexPro, AndyMark, West Coast Products, and McMaster (and re-broach/clean up some pieces ourselves) to make assemblies that we could slide together while still being mostly runout/wobble free.

Quoted for truth.

Just to elaborate on Jared’s Post really quickly.

From what we’ve found (along with many others), aluminum hex bar tends to run a few thousandths oversize, usually somewhere in the .501-.503 range - a quick sanding with an Emory cloth or similar usually fixes this problem so it’s not that big of a deal. Interestingly enough, 2024 Hex bar from McM does not seem to have this issue though as it runs a consistent .499-.500 over it’s entire 3’ length or so with very little run out. (at least the handful of pieces we’ve gotten)

Hex broached parts on the other hand are a completely different ball game. From what we’ve seen, WCP’s parts run the tightest hexes at .501-.503, VexPro’s hexes run on the larger end at .505-.507, and AM’s stuff seems to be right in between the two. For some stuff, the difference in the broaches isn’t a big deal, but if you’re chasing backlash, that extra 5 thou in a gear’s bore can get really annoying…

I’m pretty confident this is something caused by your design, not a defect or inadequate material. We have used 7075 22T sprockets for 7 years (of our own design, or from AM) with no failures whatsoever. 7075 is stronger than many steels, including some commonly used in sprockets.

We have had the straightness problem with the majority of our hex shaft. We’re almost 100% certain it is because it is shipped in a flat package that is extremely non rigid. A switch to round cardboard tube (like McMaster ships all shaft/rod/tube in) would likely eliminate this problem. We have not had issues with VEXPro gears sliding onto straight shaft though.

Planetary gearboxes are great.
Love the versa wheel hub system along gears & sprockets.
We ran 6" mechanums on a relatively light robot (100lb without battery/bumpers). Lost a roller on the comp bot & 2 rollers on practice bot. (Did I say I love being able to buy spare rollers? Change out is fast. I not really sure of the failure mode.
Love the fast shipping & customer service.