Prototype Small Wheeled Shooter

No we’re aren’t but we haven’t had any problems with the Versaplantary gearboxes or bearings. If that becomes a problem we might have to modify our design to avoid cantilevered shafts but so far so good. These gearboxes seem to be be built very well as far as I can tell. Hopefully we can get through multiple competitions with out any problems.

Do the VersaPlanetary gearboxes have a ball bearing at the input and output ends? If they do, all the side loads put on the shaft by the wheel would be taken by the ball bearings. The motor shaft would then only transmit torque and would not experience any side loads.

I think the shooter team were able to get about two dozen launches before burning out the rear bearing of their mini-CIM. One of them suggested buying a whole bunch of motors and swapping them when they burnt out. :eek: Neither the sponsoring teacher nor any of the mentors went for that idea.

Yes, the planetary gearboxes do have bearings at both ends and we haven’t had any issues with them.

To be more precise, there are two ball bearings on the output shaft and one (I think, don’t have one in front of me) on the input side holding the input coupling. So the output shaft can definitely support some cantilevered loads.

Do remember that you’re not going to be able to stick a mini-cim into this gearbox. You’ll have to go with a BAG motor and a 3:1 ratio, which will endup somewhat slower than your mini-cim. So you might be better off figuring out how to make up a shaft coupling and support system for the mini-cim.

EDIT:Actually, a BaneBots RS550 motor into a 3:1 gearbox gets you a similar free speed to the mini-CIM with a bit more power. You might try that combo as a drop-in replacement for your mini-CIM.

Thanks for the info, Kevin and Allen.

I actually have a CIMULATOR left over from building the ball shooter last year. We also got a bunch of RS550’s from Banebots using the coupon this year. We would just need to cut cooling chanels in the CIMULATOR so that magic smoke won’t come out of the motors so easily. My rough calculations indicate that two RS550’s would give a bit more speed (7148rpm vs. 6200rpm) and a lot more power (508W vs. 229W). We would just have to make sure that the motors are wired correctly so they don’t fight each other.

If you’re clever, with a custom mount plate and a trimmed down shaft, you can mount a MiniCIM to a VersaPlanetary gearbox.

-John

I’d love to hear more regarding details of your shooter: motors, gear boxes, gear ratios, wheels, voltage to motors, distance between wheels, etc. Thanks.

I can’t believe I didn’t notice it was an 8mm hole until you said that.
I know what we’re playing with next week. (Note: Not for our shooter)

blinks So that’s what that “notch” is in there for. Or so you’d hope. I wouldn’t want to pin my hopes on that set screw in the CIM keyway.

Also, I have a feeling a mini-CIM would really push the limits on the load rating of the VersaPlanetary. And if you swapped a CIM in instead… Well that’d be extremely exciting.

Depends entirely on the reduction, and output shaft configuration. Check out the loading tables at the end of this guide:

I should have pictures up in the next hour or two. I have a student doing it right now.

Instructions are up on our blog

http://3847.blogspot.com/2013/01/versaplanetary-cimminicim-mounting.html

This was a pretty simple conversion. We cut the shaft more than would most likely be recommended but that lets you directly mount it to the Versplanetary with out any adapter plate.

I don’t recall but, do you have any video of shooting with the disc upside down?

Not from this prototype, it needs some sort of cap over the wheels to get long shots with upside down discs (think the C channel from robot in 3 days), otherwise we find that the discs rise up out of the wheels before they leave the shooter.

I stand corrected. If you’re willing to green light a 1/2" hex shaft 300:1 BAG Motor for simple loading, that’s the equivalent of a 1/2" hex shaft 50:1 big CIM motor. Which at 90 ft-lbs stall and nothing to sneeze at.

Allen,
Are the black spacers for standing off an AM-9015 motor too small to stand off the CIM?

Didn’t think about it but that does work. That will add back a 1/4in to the shaft.

We’re nearly identical to that. BAG motors 1:1 and 1:3 wheels close together and the wall ending at the center of the fast wheel. Compression at about 1/2 inch. You have just verified our settings.

*I’d like to hear from teams – if there are any – who been successful spinning the 2nd wheel approx 30% to 40% faster than the second wheel, instead of 3x as fast.

Do you have any reason to assume that is more optimal? We would like to know.