Ball Shifter Reviews?

Technical Technical Discussion
1

I’ve been looking over the forums, and I have been unable to find exactly what I am looking for. I’ve found bits and pieces, but I haven’t found a central review on the VexPro Ball Shifters. We’re looking into experimenting with shifting gearboxes, and while we are generally aware that AndyMark Super Shifters are the time tested solutions, the Ball Shifter offers some benefits that were are considering.

I’m looking for mostly first hand accounts (second hand details just get to skewed, but if you have intimate knowledge of another team’s situation with them, by all means, share) of how the Ball Shifters held up this season.

Here’s a few questions I’m looking for:

Was this your first time using a shifting gearbox?
-If no;
–What other shifting gearboxes have you used? How did they compare?
-If yes;
–Was the Ball Shifter easy to work with given the lack of experience you had?

How much maintenance did they require throughout the season?
-Were there any catastrophic failures that occurred as a result of the gearbox, and not outside circumstances?

What did you find to be the biggest benefit to using them? What was the biggest drawback?

Were there any technical issues in the design of the gearbox? If so, how did you remedy them?

Would you use them again?

Don’t feel obligated to answer every question. Even if you only have one thing to say about the shifters, throw it out there. Just please be sure to provide as much detail as possible!

The help is much appreciated!

2

We used shifting transmissions for the first time this year, and we went with the ball shifters. They worked out really well for us. They were very easy to assemble and use, being our first time working with shifting transmissions. We never really had to do any maintenance on them, though many teams who used them reported that the output shaft would often slip out of place, but was easily fixable with a bit of lock-tite. The biggest benefit to using them was the pushing power, and they’re SUPER fast in high gear with two CIMs on each side. We almost tipped a bot at competition by driving in high gear and then switching to low right before we hit them (we did NOT do that again). The only real drawback was that they’re a tad bulky and we had a hard time mounting them to our frame and superstructure, but we figured it out quickly. We will definitely be using them again.

3

Our team used shifters for the first time and long story short they worked great throughout the season. We had no failures and they were easy to assemble and of corse IFI/VEX are great to work with. There was full CAD support so honestly yes I would absolutely use them again.

4

I’d also like to know if there is really any big benefit to ball shifters over super shifters?

5

Ball shifters are better than the super shifters because the ball shifters are lighter and cheaper, and it they shift quicker and smoother. I would recommend these to every team interested in shifting. The included instructions are simple and they were assembled quickly.

The output shaft needs locktite, but the shifting mechanism worked great after countless shits.

6

We used the ball shifters this year, and AM shifters last year. Previously we had used kitbot single-speed transmissions.

I’ll first talk about the downsides to the ball shifters. Though their glass-filled nylon shells were very light, they were not very durable. After a season of decent maintenance, we have a crack on one of the competition bot’s shifters. (It’s still working fine, though.) In addition, until they’re mounted, the two halves of the shell are held together only by two 8-32 button head screws, which personally makes me very uncomfortable about the security of the whole thing.
As mentioned by many others, the output shaft tends to come out when regular force is applied; we suspect it’s because it’s held in by low-quality Loctite applied after the hardened steel part of the shaft has already been greased. We pinned ours after through-drilling with a carbide bit to hold the shaft in place.
On one of our shafts, the hardened steel acquired a hairline fracture after light use; this was probably an anomaly, and IFI quickly sent us replacements.
The pancake cylinder is attached to the body of the gearbox by really small standoffs held by 6-32 screws. We never had any problems, but I know some other teams don’t believe this is secure enough.
The final thing I have to say about the mechanical construction of the gearbox regards the encoder gear. Simply put, the method that IFI uses to drive the encoder is absolute trash and should neither be trusted, nor reused on the next iteration of the gearbox. The delrin gear that drives the encoder is simply pressed into the back side of the output shaft. This press is very unreliable, and we had to superglue ours in place to prevent slipping. The superglue also cracked once during the competition season, and had to be reapplied. IFI, please find some other way of driving an encoder from your gearbox.
Finally, I wish they had more output speed and spread options on the gearbox. The speed certainly may be too fast for many drivetrains, and needs a third stage to get within a comfortable level.

However, the ball shifter has a large list of advantages over typical dog-clutch gearboxes. As it comes, it’s very light. I’m sure many teams appreciated that this year.
The actual ball-shifting mechanism is extremely solid, reliable and fast. Our team, anecdotally, noticed better shifting response times compared to last year’s drivetrain. In addition, because the balls rest and spin on a central pin, it’s much stronger than a dog gear is; team 20’s broken dog at IRI comes to mind. With a dog gear, there’s also the constant risk of shearing the screw that transfers torque. The ball shifter, though, only really has 4 modes of failure within the shifting mechanism: all 3 hardened steel ball bearings break; or the hardened steel shaft breaks; or the aluminum 7075 pin gets crushed, or the aluminum 7075 gear shears where the ball-shifting pattern is. None of these is remotely likely.
Assembly is simple, as mentioned above.
The pancake cylinder is good quality, and works great. The whole gearbox is pretty space-efficient as well.

Overall, I firmly believe that the ball shifter’s advantages outweigh its downsides. If I were to use them again, I would probably rehouse the innards in a custom gearbox to alleviate some of the issues we had. I believe 1114 did that this year. Hope this review helped.

Did you guys have a lot of Taco Tuesdays, or something?

7

The screw inside the dog gear does not transfer torque. It only takes shear load shifting. The dog gear transfers torque through its hexagonal hole which couples its rotation (and therefore the engaged gear’s) to the hex shaft. If the screw does shear, it can lead to major problems with transmitting torque, but this is because the dog is now free to ride axially along the shaft such that it may not engage with the gears anymore.

This being said, the shearing of a screw is not a flaw with the dog gear design if you don’t want it to be. A roll pin can be used for this application and is much stronger in shear than the bolt, but it is more difficult to assemble and disassemble.

8

[QUOTES=
The output shaft needs locktite, but the shifting mechanism worked great after countless shits.[/QUOTE]

:smiley: My favorite post of all time

9

I would have never even thought to try that, nice outside of the box thinking :wink:

10

These two 8-32 screws exist purely to hold the gearbox together until you mount it, rather than having to hold the thing together by hand until you get it in place. The mounting screws then provide more than enough strength to fully lock the box together.

Was there any specific circumstance or occasion that caused your housing to crack? The only cracked housing I saw happened after a fall off the pyramid, feel free to PM me pics if you have some.

11

We had issues with the encoder gear slipping in the shaft. We had to add material (paper) to get a snug fit. I didn’t want to use something permanent if we ever needed to take the box apart.

12

Three regionals, championships, IRI and several community events and the ball-shifters are still going strong. These included some high-speed ramming of the pyramid which bent the chassis and several hard dismounts from the top of the pyramid. More mounting options would be nice. We would definitely use them again.

We also used a single speed double reduction box to operate our climber. The gearbox worked flawlessly.

13

Our competition bot sustained a minor crack purely through drivetain use. (We didn’t climb for more than 10.) The frame itself was rock solid, and never gave us any problems mechanically this year. I believe that part of the reason for the crack was due to improper mounting for the first few days of the drivetrain’s use; this also caused the output shaft to slip out. We fixed the mounting issue, but I don’t recall seeing the crack until much later in the season. I’m away from the robot at the moment, so I can’t take any pictures.

On a separate note, is IFI planning to do anything about the encoder gear and/or output shaft press for the upcoming season?

14

So I just want to make sure, some of these problems that people are experiencing with the Ball Shifter (namely, the shaft coming out and the slipping encoder), are they not commonly found to occur with the Super Shifter?

So far, the issues with the Ball Shifter seem relatively minimal, so long as proper precautions are taken prior to actually using them on the robot.

15

You got it.

16

Leeland, all of our transmissions had the encoder problem. Not a big problem just an annoyance.