Re: Prototype Small Wheeled Shooter
 

I have found them to get warm but never as hot as our drive CIMs or anything like that. I think most of the 1:1 heat is from the bearings but I have no way to know that.

One of the reasons we are choosing to run BAG motors is so far they have taken all the heat we have thrown at them, which is mostly being stalled several times in a row from failed collector tests. We ran BB550 on our collector last year and stalled it once for 20 secs or so and smoked the motor. The BAGs are expensive but we don't have to replace it this competition season it'll be worth it.

I'm interested to see how the bearings in the VPs hold up over the course of the season. We'll have spares gearboxes on hand but hopefully won't have to use them.

Re: Prototype Small Wheeled Shooter
 

Bob, we're running the same ratios as you using the AM 9015 motors. We had some binding issues initially too. I emailed Vex and got an immediate reply from Paul Copioli with the very helpful technique to loosen the mounting bolts slightly and run the motor. When the motor and gearbox sound like they're running smoothly tighten the screws. That technique solved our binding issues.

By the way, if anyone else is using a AM 9015 motor from this year's KOP with the VerasPlanetary you'll probably need to use the 1/4" spacers with any gear ratio as the knurled length of the shaft is shorter than an AM 9015 motor from last year. Paul said they designed the AM 9015 collar to grip the knurling, but with the shorter knurled length it's trying to grip an un-knurled portion of the shaft. The 1/4" spacers put the knurling in the collar.

A very big mahalo to Team Spectrum for sharing their design! We were already headed down the same path, but learning about the Banebots wheels with the VersaPlanetary gearboxes sure got us to our final design a lot quicker.

In our latest round of testing we shot some upside down discs successfully into the middle and high goals from up close using the same wheels speeds as a right-side up disc without a cover. Upside down shooting was more sensitive to feeding though. If it wasn't fed quite right the disc would pop up from the first wheel. We'll probably add a cover to take care of this issue.

Re: Prototype Small Wheeled Shooter
 

Bob, when I set up a BB 550 (motor was purchased two years) in a 10:1 VP, I had trouble getting the gearbox to spin while powered. I could turn the shaft by hand (with a wheel on it - slightly difficult), but when I put it on a power supply, the shaft wouldn't spin at all and the current spiked rather quickly. I did not find this problem with the BAG motor installed 1:1. After much testing individual components, I eventually spaced the BB 550 motor plate from the gearbox with thin washers. This appeared to relieve some pressure between the motor (either the shaft or the face of the motor) and the gearbox. I notified VEX support and Paul sent me two things to try:

"1. As you suspect, the RS-550 shaft that you have may be a bit longer than we have tested and the end of the shaft may be pressing against the gear. To test this, please remove the input sun gear while the motor is installed to see if it sticks into the same space the gear should be.

2. The clamping hub and bolts are fighting each other. In order to get around this, try only using to bolts to mount the motor plate and tighten them after you have tightened the coupler."


I did not try either though, because my team had decided to go with a double BAG motor setup. Maybe you're seeing something similar?

Re: Prototype Small Wheeled Shooter
 

The versaplanetary gearboxes come "fully assembled". Should we be opening them up and adding grease?

Re: Prototype Small Wheeled Shooter
 

Yes, we recommend a light coating of white lithium grease to ensure longevity.

Re: Prototype Small Wheeled Shooter
 

I just put our motors and gearboxes through an "intensive" test. 12 volts straight from a battery to the 3:1 gearbox and the 1:1 gearbox (Both driving BAG motors.) for 1 minute 25 seconds. 3:1 Gearbox is noticeably warmer than the 1:1 gearbox. BAG Motors are warm but nothing to be concerned of, if their construction mimics that of a CIM. Do not have access to any temperature sensing probes.

*3:1 gearbox was freshly greased with white lithium grease (NLGI #2). 1:1 gearbox has not been greased yet outside of stock greasing.

Re: Prototype Small Wheeled Shooter
 

All,

There are several items that contribute to heat in a VersaPlanetary gearbox. The #1 thing that is different than other gearboxes you are used to is the thin wall of the ring gear section. The ring gear is aluminum and very thin so it conducts the heat very quickly and gets hot quickly. In addition, the thermal mass of the aluminum is less than the steel gears and bearings so it will get hotter much faster than the internal steel gears.

Also, the output shaft is also aluminum to that thing gets pretty hot, too.

The BAG motor has the same internal construction as a CIM motor and that is why it is able to dissipate heat in a similar way. It does not rely on convection cooling like a RS550, RS775, or AM-9015 so it is happy to remain at an elevated temperature. However, the aluminum VersaPlanetary case is sucking a lot of heat from the motors and acting as a heat sink. The VersaPlanetary housing gets hot, but it is nothing to be concerned about.

The bearing speed rating is over 20,000 RPM so this application should not over task the bearings.

In short, the gearbox getting hot is primarily related to the thin aluminum case and is not a concern.

Paul

Re: Prototype Small Wheeled Shooter
 

Thanks for clearing that up Paul.

Re: Prototype Small Wheeled Shooter
 

Here is our final shooter design before mounting it on the robot.
Before the hood was added today, we were able to consistently shoot at 31 ft./sec. We will optimize it now that the actual assembly is complete. We hope to squeeze another 5 Ft./sec out of it.

http://www.youtube.com/watch?v=cpHcM...ature=youtu.be

Re: Prototype Small Wheeled Shooter
 

Awesome video, I like the feeder, very simple. What are the specs? 3:1 and 1:1? Compression? Wheel Separation?

Re: Prototype Small Wheeled Shooter
 

Here is our shooter as of Monday. Standard stuff, 1:1, 3:1, bag motors 'bout 3/8 compression right now with a rubber strip on opposite side.

We designed it to use two or three wheels but found the third wheel added little for the amount of complication it added. We also tried 3" Colsons but switched back to the Bane Bots. You never know, durability testing may make the Colsons more attractive.

Sorry for the shaky cell phone video.

Big thanks to the folks at 3847 and everyone else who shared on this thread.

Re: Prototype Small Wheeled Shooter
 

Yes, 3:1 and 1:1. Wheel separation is approximately .25". Currently the compression is around .5", but we will be optimizing that using a chronograph today, getting actual numbers instead of just observation.
Although, even if we leave it exactly where it is, it is already acceptable for our game play strategy.

Re: Prototype Small Wheeled Shooter
 

Question for those of you running a close spacing between the wheels do you notice any issues with discs being in contact with both? Currently our wheels are approximately 1.5" apart and I'm wondering if it its worth re-manufacturing the attachment at this point.

Same as most people: 1:1 and 3:1 Bag motors, orange BB wheels, and using a piece of of roughtop on the fence with about .25" compression.

Re: Prototype Small Wheeled Shooter
 

I'm thinking the same thing. There's currently, on ours, something like 2.5 nineteen our wheels, as we were discovering significant wear on our 1:1 wheel. Same setup as others - 3:1 and 1:1 bag motors, 2.87 blue banebots wheels, 9/16th compression, gaffers tape on the compression wall, AND A COVER over the wheel (picture to be posted in an hour) and were getting absurdly less distance than anyone else

Re: Prototype Small Wheeled Shooter
 

We aren't running tiny wheels but smaller than most, and it was my engineering intuition that says having the frisbee touching both wheels has to be detrimental to overall performance as that pretty much necessitates one wheel slipping. Ours is designed so this isn't possible and the shooter does seem to perform quite well with minimal wear on the green banebots wheels.

Additionally, roughtop as a backstop is probably not the best material. Roughtop actually has pretty poor friction on plastics