Hi, we’ve got a bit of a rookie question here relating to some of our mini-CIM and BAG motors (This is our first FRC season, so be nice).
Mostly we’ve been struggling to attach all our different wheels to the three main motor sizes that we have. All our wheel hubs seem to be fitted exclusively to CIM motor shafts, and all the others don’t fit.
Plus the BAG motors have these absurdly short shafts, with no keyway. Is there something with a grub screw that mounts to that? And the Mini-CIM have a shaft that looks like the regular CIM shaft but is actually slightly smaller.
So does anyone know where we can get some shaft adapters, or some wheel hubs for AndyMark wheels that will fit smaller motors?
If you are using these on a drivetrain, you should certainly be using gearboxes of some sort between the motors and the wheels. For example the ToughBox Mini on the Kitbot drivetrain (assuming you have that). As a result, the motors shouldn’t have to go directly to the wheels, instead your wheels would have a 1/2" hex or 1/2" round w/ keyway or similar shaft size. Compared to the 8mm shaft of the CIM.
If you are planning on an intake or something similar, I can highly recommend Vex Versaplanetary Gearboxes to be used with the BAG motors. They have an input option that works natively with the BAG motor. I would not recommend using BAG motors (or VersaPlanetaries, for that matter) on your drivetrain.
For the MiniCIM, they were designed to be a drop-in replacement for the CIM with 2/3 the power, so the mounting holes and shaft SHOULD be more or less identical. Even if the shafts are slightly shorter, the wheels can still mount to them, right? Either way, you should certainly be putting these through gearboxes as well, and not connecting them directly to wheels.
I’ll second this, in the 12 years I’ve been in FRC only once did I have a reason to directly drive a wheel off of a motor with no gearbox (2013 Frisbee shooter, and even that was not a great idea). For almost all applications, your motors should be run through a gearbox or some other reduction (chain+sprocket or belts) rather than directly attached to a wheel. BAG motors in particular cannot handle the same loads as a CIM or MiniCIM (they also run as much higher RPMs) and may burn out when whatever they’re direct-driving takes any sort of load.
You don’t have to get too specific if you don’t want to give it away but if you could explain a bit as to what you’re trying to do we can give you better suggestions to workaround the issues you’re having. Pictures are also helpful.
BAG motors are not designed for drivetrain usage, in general–think “[generic game object] intake” instead. And I’ve seen (smelled) one smoked BAG in normal intake usage. (Just one, though, since they were introduced.)
As noted above, all three types need a gearbox of some type; there should be two in your Kit of Parts that are built to put CIMs (and MiniCims, which use the same mounting pattern) to use in your drivetrain (unless you opted out of that particular part of the kit).
Also as noted, if we knew somewhat of what your general objective was (drive, intake, launcher) it would be easier to inform you of easier ways of doing the same thing.
Hi everyone that has responded so far, and thanks for your advice.
We are specifically trying to use them for our intake. What we are doing is have two arms, tensioned with a spring on the inside, applying pressure on the cube. Two wheels are then attached on each arm. Each arm has one motor powering both, directly driving one of them and then via a belt powering the other.
Yep, you want a gearbox. You will likely fry the BAGs without one.
VersaPlanetary, you’ll need to figure out the ratio you want based on how fast you want the cubes to fly into your intake, follow assembly instructions. Advise that because you’ll have two wheels on each there might be a little extra inertia, but you want to run fast on intakes as a general rule of thumb.
Also, if I am not mistaken the gearboxes will take the shock loads (i.e., a bump to an arm, or a ball being fed into a shooter) so that the motor will not have to. Chain runs are especially good at this IIRC. This will reduce the chances of the motor being smoked or something of the like.
Depending on the motor and direction of the shock load, you may be mistaken.
Gearboxes make it more difficult to move the motor from the output shaft side, therefore a shock load on the output of a gearbox may damage where the output shaft meets the gear (or carrier plate). Whereas that same shock load to a motor may just turn the motor.
Reducing shock load to a gearbox is usually done with chain and sprocket from the gearbox to the moving member.
Shock loads, not exactly - gearboxes are suceptible to shock loading as much as anything else is. That doesn’t mean they will always fail, but when high shock is a concern (eg long arms) using chain as a dampener is much better for the gears.
Side loads, generally yes. Side loading a motor output shaft such as in an intake or shooter with high compression could accelerate wear over time; gearboxes take the load at the gearbox output shaft so the motor doesn’t have to.
Really the compelling reason to use a gearbox is to find a different place on the speed / torque tradeoff curve. If you’re not sure how fast your mechanism should be going or what torque it needs, the first hint I’ll give is that it’s very rare that you don’t want to increase torque and reduce speed (only direct driving a flywheel shooter with a CIM is the main common FRC application I could think of)
This is a link to where we get all our gearboxes for intakes. This is a big supplier for FRC teams. You can get a 1/2 hex output shaft for the end of your gearbox, and order wheels with a 1/2 hex boar. These gearboxes can be used for many motors including 775 pro, bag motor, Cim [with add on kit], and Mini Cim [with add on kit]
VersaPlanetary gearboxes are great and versatile and common in FRC.
There are other gearboxes made by AndyMark and BaneBots too. For example, the KOP this year includes a AM-57 Sport planetary gearbox and the 775 motor that can go with it. Especially if you’re a rookie and don’t have a lot on hand, this might be a possible drop in for what you want to do.
The big motors are usually used with AM Toughbox / CIMplebox / Supershifter / Vex ball shifter and the smaller motors are usually used with planetary gearboxes like VersaPlanetary / AM 57 / Banebots PG*. There is some amount of COTs shaft adapters to adapt smaller motors to bigger gearboxes, like the CIM-like output for VersaPlanetary.