VEXPro - After the season

[The Lucas]

Originally Posted by Tom Line

I'm looking forward to trying the ball shifters this off-season. We usually don't use shifting drivetrains because of weight, but that may change now. I would absolutely LOVE it if Vex can look into supplying a kit that allows fast reliable shifting without pneumatics. In fact, with a little innovation, it's not impossible for the same kit to work on the supershifters as well. I've seen a number of solutions. The most elegant I saw was a single window motor with spring loaded arms (Hot in 2012). The servos are simply not powerful enough to shift under load. I've seen very few teams use them for exactly that reason. We plan on putting the ball shifters on our robot for the off-season to test them out, and will probably look at a solution at that time (we don't have pneumatics on this year's bot). There was a fellow at MARC last year with a really nice sliding arm linkage made out of lexan that was along the same lines - just bolt on a window motor and go.

I originally sent this suggestion via PM to Adam, thinking it was just a possible solution to specific issue, not thinking it was really relevant to the general VexPro product recommendation topic. However, after reading your post I and Adam's other post, I think it might be on topic.

Electric Solenoid Actuators are legal for use in FRC since last season. See R32 for the specs and R70 for the maximum output of your Solenoid Breakout (alternatively, you can use relays). I speculate that the primary reason for this rule change was to facilitate shifting without pneumatics. I expected to see some teams use them or Andy Mark/VexPro to make a electric solenoid shifter kit. However, I haven't seen anything yet, maybe it is something they will develop this off-season (I dont know what the market is like for non-pneumatic shifters and the ball shifters are new this year).

There are many design considerations for electric solenoids including:
-Push vs. pull (this determines your default gear ratio)
-Return spring (to keep you in default)
-Solenoid package and mounting bracket
-Force vs. stroke (it varies, look for it in specs) enough to shift
-Wattage
It would be nice if one of the vendors engineered a nice solution for everyone to use.

[Paul Copioli]

All,

The VEXpro wheel hubs (including Mecanum Wheels) are all made from glass filled Nylon. One of the many reasons we used glass filled Nylon was so that thread locker (specifically, Loctite 242 or equivalent) can be used.

We will make it more clear in our documentation, but in all cases when using steel screws with aluminum or steel mating parts, thread locker should be used. There is nothing in the standoffs inside the wheels to physically lock the screws.

I highly recommend using thread locker with all of our hex standoffs in all of the VEXpro wheels.

Paul

[AllenGregoryIV]

Versaplanteries are amazing and pretty much allow our robot to exist.

We're also using a full VEXpro drive train with the chassis in a day, single speed gearboxes (5.33:1), vex sprockets, and versawheels.

I will say that we have seen heavy ware on on our versawheels. The four that are on the ground all the time are practically round after our two regionals. They are first on our list of things to change out at Razorback next week. I still love them but we have worn them down enough to need replacement. At $5 a wheel I really wouldn't care if I had to change them each regional.

Also I can't say enough about how awesome their hex shafts and 1/2" shaft stock are for the price. Plus their hex shaft collars are awesome as well.

[Teched3]

We went with single speed, 2 stage transmissions, and they have worked great on our competition robot as well as our practice bot. The only comments I have about Vexpro are:

The plastic transmission housings when we got them early in the season did not give good gear interface and were noisy. We immediately decided to make our own plates and spacers, and they have worked great. Nice and smooth, and no discernible wear on the gears.

The lack of sufficient inventory on the hex bore Versahubs (217-2592), which are still listed out of stock. Modified AndyMark hexhubs to our Vexpro wheels. The few we did get were great. Fit on the hex shafts though some were too tight. Used a Jewelers file and dressed the flats to get a good sliding fit. Next year we will machine the shafts to .500 d. and key to 1/8 as in the past for better concentricity. Initial shortage of hex bearings created a lot of anxiety as well.

Longer shafts on the ball shifters for wider wheels on WCD would also give more design versatility. We used an additional hex bearing in our frame on the shaft of the single speed tranny to take some of the load off the shaft bearings in the housing. Couldn't do that on the ball shifter due to the shorter shaft.

[dyanoshak]

Originally Posted by MattC9

When our event rolled around our driver put those things to the test and near the end of quals on Saturday he had trouble shifting on one side and started to drive in arcs. This was due to a loose piston mount.

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.

[MrForbes]

Originally Posted by z_beeblebrox

We used a complete Vex Pro drive system with ball shifters, drive in a day and traction wheels. Overall, everything works great (The shifters shift plenty fast), although the shifters do occasionally lose output shafts, but are easy to fix..

After the Bit Buckets' robot lost an output shaft in their last qualifying match, we made a quick crutch to try to prevent it happening in eliminations. This is the Rube Goldberg fix....good for entertainment value, maybe not the best solution to the problem, but they were still driving fine when they lost.

[z_beeblebrox]

Originally Posted by MrForbes

After the Bit Buckets' robot lost an output shaft in their last qualifying match, we made a quick crutch to try to prevent it happening in eliminations. This is the Rube Goldberg fix....good for entertainment value, maybe not the best solution to the problem, but they were still driving fine when they lost.

Except, after our first elimination match, we learned that the screws holding the shifting piston to the ball shifter came loose. Because the shifters had to be disassembled to tighten the screws, it would have taken more than an hour to fix. We used a clamp to hold the piston in place for the last match. However, we had to stay in low gear.

[Tom Line]

Originally Posted by MrForbes

After the Bit Buckets' robot lost an output shaft in their last qualifying match, we made a quick crutch to try to prevent it happening in eliminations. This is the Rube Goldberg fix....good for entertainment value, maybe not the best solution to the problem, but they were still driving fine when they lost.

Red Oak? Nice choice. Show it to us again after it's stained and polyurethaned.

[Steven Donow]

Some more comments on VEXPro after this weekend:

Versaplanetaries-they held up completely fine for us(except for a busted 775-nothing VEX related) except at one point, the CIM output shaft flat out broke. Now, this could just be due to considerable wear of the shaft throughout the season, but we were lucky to have it happen to us at the end of the day with no matches left in that day.

Ball Shifters-Worked great as they did before, except for one match where the mounting screws of the pancake cylinder became loose, which was a relatively difficult repair. Also we experienced another issue that another team also experienced (from losing their pneumatic system for a match)-when the cylinders lose air, it seems that they default to neutral gear-it'd be nice if it were a spring return/release cylinder that defaulted to either high or low gear.