VEXPro - After the season

We were pleasantly surprised by the offerings from Vex Pro. This was a good year for all FIRST teams by their addition.

Ball Shifter - We had several failures mostly self induced. The fitting on the solenoids are just too fragile and I would like to see them (or even the whole solenoid) changed. We also lost our chance at Boilermaker when the C-clip sheared off the end of the sifting shaft costing us two matches.
I’ll be perfectly honest, with FIRST allowing so many good powerful motors to choose from, I doubt we will ever shift again unless the game screams for it. Six or even eight motor non-shifting drives may become the norm for us.

Bag Motor - This motor caused us many headaches this year. We started with four on our robot and ended with zero. I really hope the problems with this motor are solved, it’s a nice package and has huge potential

VersaPlanetaries - A real game changer. Easy to use, easy to change and modify, by far the most significant new part to come to us in a long time. These little things took every thing we could throw at them. We used six on our bot from 1:1 to 1:300 with various motors. We abused them and they never let us down.

Gears - These low cost high quality gears enabled us to finally have our dream of a robot without chains. Our completely gear driven drive never gave us a second of trouble. The gears on our practice chassis still look almost brand new after many hours of use.

I’m eager to give it another go now that we’ve fattened up a bit. We weighed in at just under 97lbs at Hatboro when you shoved us. We were up to just over 110 at Lenape, but we never got in a pushing match with you guys there. Should be slightly heavier still if we reach Lehigh.

We found the direct opposite with 1712. The points would dig into the carpet when pushed sideways, almost working like a cleat. We’ll continue to observe this as the wheels continue to wear.

Sorry I’m a bit late with this reply, been a bit busy competing…

Here’s a picture showing the difference in tread profile between a well-worn versawheel and a brand new one. The wheel on the left has ~40 ‘official’ matches on it, ~10 practice matches and some build season run time on it. It’s noticeably slicker than a new wheel, almost as if the tread has glazed over.

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. :slight_smile: :slight_smile:

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.

I was thinking about purchasing a set of 8" Mecanums for my team. I was just wondering why there is such a significant disparity in price between the ones VEXpro sell and the ones AndyMark sell. Does anyone know if there is a comparable quality difference as well?

As far as I can tell, there are two major differences:

  1. Plastic (glass-filled Nylon) vs Aluminum body
  2. Place of Manufacture
    (tradeoffs here – reference Andy Baker’s 2009 Small Business lectures for advantages of local part sourcing)

It’s all about final application, particularly with respect to #1. Neither is superior to the other without context.

Just and addendum to our ball shifter woes.

After further investigation I believe that our problems were self induced and not the fault of Vex.

I don’t think the c-clip was properly installed and that is what lead to it’s failure not a problem with the shaft itself.

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

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.