Quote:
Originally Posted by TheHolyHades1
1. Does anyone know if more COTS solutions exist? It seems each of the major FRC parts suppliers has their own, and I think we've covered all of the major suppliers.
|
There are certainly other COTS solutions to two speed gearboxes out there, but none I've ever found that are nearly as well tailored for FIRST applications.
Quote:
Originally Posted by TheHolyHades1
2. How do the gearboxes compare to each other in terms of durability, ease of use, ease to modify/change gear ratio and motors, shift ability, shift speed, ease to mount, etc? We're a relatively low budget team and currently don't have the budget to do testing with all of the various designs.
|
We've used Andymark Super Shifters in past years, this year we went with a VexPro 3CIM ball shifter and were very happy with it. We also purchased a pair of 2CIM ball shifters but did not use them.
Here's a few things we observed from our 3CIM Ball shifters (This will probably look pretty similar to Joseph Smith's response above)...
Pros- Surprisingly lightweight (until you add 3 CIM motors of course)
- Fairly easy to assemble, but not as easy as the 2CIM Ball shifter
- Very durable, we took our shifters apart after our 2nd event to switch ratios, and the gears all looked like new.
- Shifted without issue using the low profile pancake cylinders we got with them.
- Shifting is virtually instantaneous and can (usually) be done while stopped, in addition to while moving.
- Changing gear ratios is really easy if you're not also changing the shift spread since it only requires changing out the 3rd stage.
Cons- Changing the shift spread requires removing the tiny C-clips for the shifter coupling in order to get the ball gears out which is a HUGE pain. Other than that though the process was fairly simple.
- We ended up having to create custom spacers to be able to face mount the gearbox with the 3rd stage and have it secured in more than 2 spots. Not a big deal but it would have been nice if something were included with the 3rd stage (or could be purchased) to accommodate this.
- Assembly instructions could have been a bit clearer in places
For comparison, here's some things we've found out about Andymark Super Shifters we've used in the past...
Pros- Easy to mount
- Decent variety of available ratios (though the Sonic Shifter has far more)
- Completely enclosed gears (No external 3rd stage)
- Easy to assemble
Cons- The servo shifting doesn't work reliably, don't even try.
- Steel gears are heavy, but the lighter aluminum gears don't hold up nearly as well.
- Parts of the assembly seem unnecessarily heavy (The spacer/cover piece in particular).
- More expensive than its VexPro 2 motor counterpart.
- Slightly slower to shift than a ball shifter
And finally, even though we did not use our 2CIM Ball Shifters on our robot, we did note the following:
- They're the cheapest, by far of all the 2-speed gearboxes in common use in FIRST
- They're very easy to assemble (from the time we opened the boxes we had them both assembled in less than 20 minutes).
- They're very, very lightweight.
- They have a very small profile
Beyond that, I would venture to guess their performance characteristics are very similar to the 3CIM ball shifters.
Quote:
Originally Posted by TheHolyHades1
3. Which one would you recommend (doesn't have to be from the list)?
|
I've honestly been quite impressed with the VexPro gearboxes this year, I'd personally recommend either of their ball shifters.
Quote:
Originally Posted by TheHolyHades1
4. Overall opinion on shifters?
|
Honestly it depends on the game. Some years there have been games that did not require a shifter at all (2009 comes to mind just to name one), but years like this year where you have a wide open field and a need to cross it quickly but also be able to play defense, a shifter is absolutely essential. The exception to this is if you're using a drive system built for maneuverability over pushing power (like using all omni wheels for instance), in that case a simple low reduction single speed would probably work fine.