VersaPlanetary Gearbox + BAG
These gearboxes are really awesome. Very easy to put together, mounts a number of different ways, and gear ratio changes are a snap. We designed for and bought one ratio, tested it, and then decided we wanted to up the torque a bit. All we had to do was buy another gear set, take it apart, swap it in and go. Assembly or a gear swap is a 30 minute job for freshmen whom had never assembled a gearbox before. These are great for prototyping as well. Cool bonus: An 18T HTD pulley fits right on it with plenty of belt clearance even if side mounted.
BAG Motor we had no problems with. Robust, never got warm, no finicky motor leads to deal with, etc. That said we did not apply much load.
Mecanum Wheels
Did not use these on the ground, so I can’t comment on their build quality under drivetrain loads, but these wheels were killer on our intake this year. I think these made us the best pickup at our events. Rubber is grippy and Colson-like on these rollers; great grip on this year’s game piece. The weight wasn’t too bad either. We’ll definitely be playing with these on manipulators in the future.
VersaFrame 1x1 .04" wall
The Good: Hole pattern stock is awesome. Not having to drill in a pattern saves so much time and is so easy to play with. We initially used it for our roller claw as it was versatile enough to let us change geometry around. All in all a pretty awesome system.
Don’t let the relative length of these sections fool you: I’m a fan of the VersaTubing and would buy again, particularly if it came in different wall thicknesses or hole diameters.
The Bad: .04" wall is only good for some really specific no load applications. Obviously this stuff shouldn’t leave the bumper zone but even inside a frame you need a well supported system to survive any kind of impact or cyclic loading.
When we designed the claw using this stuff, we knew that many / most members would not be robust enough to last through competition. We decided we would replace members that broke on the practice bot with thicker wall members until we stopped breaking things. I’m not criticizing Vex for our use of the product outside the bumper zone as we knew what we were getting into and designed the rest of the claw to be strong (solid standoffs, flat “belly pan” pieces to tie things together, etc).
The very thin profile is weaker than I could have imagined and failed in very interesting ways. We used screws mounted to one side of the tube (tool clearance on the other) to retain a dead axle that our intake pivoted about using pneumatics. The axle holes here, as well as the holes that we mounted the pneumatic pivot to, deformed under cyclic loading to the point where the holes were noticeably ovalized and the mechanism had significant slop. We fixed this by adding material to those areas - usually with a thicker gusset plate - but even 16 wall tube had this problem far less than the Vex setup. We also found that over tightening a bolt going through both sides of the tube would very quickly cause the tube to sink in or pull out, without much resistance to warn you of what’s happening.
We had our pneumatic pistons mounted to a plate which we riveted with four rivets to a set of 2x 1x1 tubing. The force of these pair of 3/4" bore pistons at 30 PSI was enough to rip the tubing outward, eventually shearing rivets right off. Upgrading to 3/16th rivets helped with the rivets not breaking anymore, but the failure moved to the tube instead of the rivets! We found this was the case with this tubing - if you upgraded to high strength 3/16" aluminum rivets, the tube would plastically deform dramatically before a rivet would break.
VersaFrame 2x1 .1 Wall
We didn’t use much of this stuff (just on the shooter), but it was really nice. .1 wall is a good compromise between 1/8" and 1/16" wall material that’s commercially available. Again, the built in hole pattern is awesome. We didn’t have much need for the alignment lines on the sides but those are a nice addition for locating hole centers and an easy way to tell at a glance if a hole is “dropped”.
VersaFrame Gussets
Also excellent. Just the right thickness at .09. Easy enough to drill out to whatever rivet size you feel like using. Saved us a lot of time making these on a router or the haas. The End Bearing Gusset is a really cool and rigid way to put a roller on a stick. The bent 90 degree Angle Gussets are incredible. This is a very hard part to make for us as it requires precision bending, but it’s been a part we’ve always had a need for in odd places. Allowed us to strengthen a small unsupported section of claw tubing very easily. Bearing hole is a cool bonus that I’d like to find a use for someday.
VersaChassis in General
The 5/32" hole pattern was kind of awkward. I would have much preferred a hole pattern for 3/16" rivets that could be drilled out to #10 clearance. #10 hardware and 3/16" rivets seem to be the standard in FRC for a lot of teams. It’s fairly easy to find rivets in that size and you can get a variety of different kinds (colored rivets, high strength aluminum, etc). 5/32nd rivets that we used are a bit weird and didn’t have the large grip range we were used to with 3/16" rivets.
Overall, I would like the system a lot better if it used a 3/16th rivet hole pattern and if the 1x1 was available in .063 and .1 wall as well as .04 wall. Either way though, it’s a very cool system that can really help teams out regardless of resources. We’ll be using these products in the future. Perhaps with our own 1x1 tubing though.
HTD Belts & Pulleys
We decided that the quick lead time of Vex belts in build season was worth switching from GT2 to HTD even if it is a theoretical downgrade. We used 15mm Vex belts with 24T B&B pulley stock in our drivetrain. No problems whatsoever to report. No ratcheting, performance changes, or otherwise. Exact centers with 15mm belts are a very good system for FRC drivetrains.
We used a 9mm belt with 18T pulleys on the claw roller. We used CAD to model an exact center distance between parts in an assembly and it ran just fine with no problems. Pulleys were light and durable. The belt subjectively seemed looser than one might expect but it ran like a champ. I don’t think I would want to manually tension these belts and just guess the “right” tension when exact numbers work so reliably. These belts aren’t going to stretch in an FRC season.
Vex 1/2" Hex Shaft
This stuff is awesome for 99% of use cases. Being able to slip fit through any hex bearing is just so awesome. Saves us hours of facing down our hex shaft stock to fit through bearings. They can’t take any load thrown at it (obviously) but they have merit. Subjectively the way these shafts failed didn’t quite “seem” like 7075 of a proper temper - the alloy may have been slightly off or untempered? If that was the case though it was close enough not to notice until you were pushing the limits of any 7075 shaft.
A specific problem with these shafts is mentioned in the next section.
Vex Gears
These are great. I love the standard width and the noticeably improved efficiency over competitor’s gears. Aluminum gears are also extremely light. In our drive they took whatever we threw at them, and didn’t wear much with white lithium grease applied.
These gears do have a problem with our specific use case for them. In order to fit in “any” hex shaft, the hex bore is a bit loose / oversized in these gears. First, I just want to say that it makes no sense for the hex bore in a ball bearing to be tighter and more precise than the hex bore for a gear. Why not use the same oversize broach in the bearings? Second, this loose broach creates a bit of inherent slop / backlash that can stack up very quickly. We made a six stage arm gearbox with .003" added to the centers and using the Vex hex extensively. The slop in the gearbox was compounded so badly that the arm had literally 7 degrees of slop. This was very difficult to fix after the fact and ultimately we replaced the geared arm with a winch-down system because of this slop. This isn’t an issue in common 2 or 3 stage gearboxes, but it does prevent us from doing an entirely geared arm which had its advantages. Oh well.
Ballshifter Shaft
We used the shifting hardware from a Ball Shifter this year on our winch and overall the system worked well. It did not need a substantial amount of pressure to release our 80 pound CF spring shooter. There was wear on the gears and shifting plunger over time but it took several hundred shots for it to become a problem and replacing shifting hardware was cheap and easy.
The mechanism to couple the ball shifter to its shifting piston is inherently flawed. A tiny bearing and some rotor clips are clamped on by a plastic device which also captures the piston rod and nut. The bearing did not take radial loads well and ended up seizing. The rotor clips sheared several times with only 30ish pounds applied to the mechanism. We did end up using a 1.5" bore piston with the device regulated to 30 PSI, so forces were a little bigger than a normal shifting piston, but if the setup is that borderline, I would not trust it in a drivetrain either. We ended up making a cool custom coupler designed by our head mentor that used a bigger bearing. We had to thread the end of our Ball Shifter plunger shafts and install a flanged cylinder onto the shafts to retain the ball bearing one way. We used external and internal snap rings to retain it in the other direction. Once we upgraded this piece, the shifter worked pretty much just fine.
I wish the balls wouldn’t cut into the gear or shifting plunger so much. Maybe a less hard set of shifting balls could be used, or a steel plunger.
Also, the hex shaft on the end just slid out one day on the practice field. Pretty annoying. We applied some Red loctite and fixed it but there should really be a cotter pin or something.
We found that over tightening a bolt going through both sides of the tube would very quickly cause the tube to sink in or pull out, without much resistance to warn you of what’s happening.
Colson Hubs
These are still awesome and they look even better in black. Some teams (20) noticed that the OD was a bit small for a good press fit and that they could slip the press fit before the wheels slipped on the ground in extreme cases. Knurling the outside fixed this. We didn’t encounter this problem, but a bigger OD would help prevent teams from running into this problem. Otherwise absolutely no complaints.
Hex Shaft Collars / Spacers
LOVE these shaft collars. Very light, thin, and a good range from tight to loose. These are so useful. The spacers also proved really useful too. Just having hex broached plastic spacers in your toolbox is so much cleaner than making something out of PVC or whatever. Will buy both again.
All in all, happy with the Vex product line this year.
I do have to say, lots of teams are very critical of Vex’s belts because of snapping in the drivetrain. I’ve very much noticed a common denominator between these scenarios- Teams used 24T, 9mm belts without exact centers in their drives. This is simply not a good design for FRC. 9mm belts with pulleys that small are drastically undersized for the application. Using tensioners makes unequal tensioning, overtensioning, or undertensioning very possible which can make these problems worse. You would have failed Gates belts or SDP-SI belts too. I don’t know if Vex belts had manufacturing problems or not, but using 9mm belts and small pulleys in the drive is asking for problems. Trust me, go 15mm.
