Best Shifting Gearbox?

Technical Technical Discussion
#1

My team has decided to use a shifting gearbox to push/avoid being pushed by other robots. We think that it will be very useful for defensive and sometimes even offensive situations, as well as making precise movements.

We are making a large AndyMark order tomorrow; the mechanical lead and I have been put up to the task to create a list of everything to be ordered/decide on the drive train. Going over MANY options, we think we have narrowed it down to using 6 x 8" plaction wheels, on a 4 cim drive.
I created this thread yesterday to assist with our decision, feel free to leave your opinion as we are still open to change

That being said, we have been searching for a gearbox. After doing some quick searches, we have realized that there are many options to choose from.

Someone in the thread I referenced stated that pneumatic shifters are overall better than shifters with linear actuators (considering the fact that we are using pneumatics on our robot anyway).

I’m sure the “best” gearbox is dependent on the configuration of the robot, but we would like to know which ones we should look at and their pros/cons if possible.

Thanks!

#2

If you are already making an AndyMark order, the Evoshifters are great. They are pneumatically shifted and have a lot of possible gear ratios and can directly bolt onto the Am14u3. There are not really many cons except you want to build a belly-pan to cover the bottom to keep out field debris. Hope this helps!

#3

We haven’t done shifting gearboxes since our rookie year (when our strategy was to be a defense robot), but I certainly agree that pneumatics is the way to go. They are light and (for small loads like shifting) fast.

As with any drive train, but especially one with any peculiar variables like shifting, be sure to have your drivetrain built as early as possible so your driver(s) can learn to take best advantage of it.

#4

Thanks for the info!

Just wondering, what are your thoughts on the VEX 2 CIM Ball Shifter? It’s lighter, cheaper, smaller, and is also pneumatically shifted.

#5

Might I ask why you have not used them since your rookie year? Also, do you think the benefit of using them over a single speed gearbox is worth the shipping time, weight, and area they take up? What are your thoughts on the usage of shifting gearboxes this year?

#6

I can recommend the Vex Ballshifter. We used the 2 CIM version on our intake/climber last year (high gear for intake, low to climb), and we are using the 3 CIM version on our drivetrain this year. They are very nice gearboxes. One more that hasn’t been mentioned is the WCP DS gearbox which is also a great option.

If you are using the kit chassis (AM14U3) then I would recommend shelling out the extra cash for the EVO shifters. They fit with the kit chassis by default, whereas with these two (Vex and WCP) you will have to manufacture some sort of mounting plate.

#7

What’s the difference between the WCP DS and the Ball Shifter?

#8

They both use different methods of changing gears. The WCP DS uses dog shifting and the ball shifter uses, well, ball shifting. Here are some decent videos to see how they work: dog shift, (it’s an AM super shifter but same concept) and ball shift. Sorry these are both really blurry but hopefully you can see what is going on.

The housing on the ballshifter is completely contained while the WCP DS (dog) is open. I prefer the closed gearboxes so debris doesn’t get in, and grease doesn’t get out. This is the main reason that I would personally recommend the ballshifters over the WCP DS. I haven’t had a reason to switch yet, and I’m not really sure if the whole open-air thing is a huge issue. Someone else can probably chime in on that.

Besides that, the only real differences are the price, the weight, and the mounting options. The ball shifter is a bit cheaper, and I can’t really think of any reason that it would perform worse. Perhaps the dog shifting mechanism is a bit more robust. The ball shifter is a bit heavier, but it’s the difference between 2 pounds and 2.5 I think. Not too significant. For mounting, they are just different. Neither is inherently better. Look up the CAD models on their product pages to see how they would mount to 2x1 aluminum tube.

Also, the EVO shifter also uses dog shifting, in case you were curious.

#9

Our team used a VEX 3 CIM Ball Shifter last year and had some issues due 1) to the aluminum gears that are offered with the gearbox and 2) the closed gearbox design that makes it hard to notice or diagnose problems.

Just to preface this, we had programmed very aggressive automatic shifting so perhaps a 2 CIM or more moderate drivetrain may not face the same issues. The aluminum gears had nearly all of their teeth shredded off which resulted in a bunch of matches where we had sub-optimal to not existent drivetrain function. Because the closed design we could not see the gears without taking the gearbox apart which made it basically impossible to check to see if the gears were shredding.

With that said, we replaced the aluminum gears that we bought with the gearbox with steel gears and had less issues although eventually the ball shifter itself started to go.

Also the price seems to have dropped significantly so maybe buying some replacements and preemptively replacing the aluminum gears could be a price effective solution.

This year we are going to try the evo shifter but our team doesn’t have any experience with those so we will see of it is up to the task.

#10

This definitely clears things up.

I think our decision will be based off of the gear ratio options :slight_smile:

#11

Was your decision to go with the EVO shifter based off of your experience using the ball shifter?

#12