Cargo Compression vs. Shooter performance

We’re having some major issues with our cargo placement “shooter”. We’re using a single shaft, versa planetary box with a 775 (I believe) geared to 3:1. I’ll check in the am for proper numbers. This is off the top of my head. We used 4"x2" Colsons initially but found the ball would not clear the chamber so we increased the chamber’s size by reducing the size of the wheels we used. I’m thinking we need to place more weight onto the shaft to increase inertia. Any suggestions there would be appreciated. We don’t have milling capacity so custom weights are kinda’ out of the question. We’re using 3" Colson wheels as our shooting wheel set. We changed from 4" to 3" to get more clearance in the shooting chamber. This year’s cargo balls are so compressionable that the 4" Colsons burned a hole in one rendering it useless. I am toying with replacing the Colsons completely with some AndyMark soft wheels (35A, 4") but won’t know if they work until we put them on.
Any suggestions for improving drive performance? Optimum gearing you’ve found that works better than others for this game? I really don’t want to settle for just the cargo ship and hatches. I don’t believe that is a good return on our team’s investment in money, design time.
This is frustrating on the last two days of build but we did make our own issue by assuming the design would work. :wink:

I know for previous years and this one you need the happy medium of speed and torque I don’t think a 3:1 will do that. We are using a 12:1 this year and used a 16:1 last year and haven’t had problems with it. How is your shooter designed too can you add a hood with surgical tubing if you change wheel size to compensate. A good thing to look at might be a few of the robots from stronghold.

Can you post some more pictures/drawings/videos explaining what your shooter looks like, what you want it to do, and what it does now. You said you’re having “major issues” with the design, but didn’t really explain what those major issues are. Changing your compression distance/wheel compression or gearing might help solve your problem, but there might be something else causing it.

It’s late in the game to be changing your drive ratio. The options also depend a lot on what type of drivetrain you’re using, and the optimal ratio will depend on your robot type and strategy. At this point, lots of driver practice will probably do more than changing drive ratios.

Our main drive works great. It’s the shooter drive that is lame right now. I’ll post up some pics in a bit.

Here’s a quick video that shows our shooter mechanism I was in error. We are using a BAG motor with Vex Versa transmission. The 775 is part of our ball/cargo transport system to the shooter

You are correct in thinking that your problem is likely inertia. With minimal time to transfer energy you need a large amount of stored energy where the amount required to be imparted to the ball is much less than total energy stored. More wheels is the easiest way to add inertia and they don’t need to be in a position where they can contact the ball. So add those 4" wheels back onto the shaft but positioned where they do not contact the ball.

Here’s a video of our testing on Thursday. We replaced the 4" with 3" Colsons. Will remount some of the 4" wheels on Monday and test results. I couldn’t get the CD site to upload the mp4. Here’s the You Tube link instead. This is not a reveal video. Just a testing video.

How far do you want the Cargo ball to go? Is it only to get into the Cargo Ship or are you wanting it to get to the top Portal of the Rocke Ship?

If you are only aiming for the Cargo Ship, you need more of a “toss” than a reall “shot” and you can probably get away with a much less powerfull and slower motor/wheel combination. We are using a BAG motor with 25:1 VP’s driving 6" roughtops on each side. The Cargo ball is always in contact with the wheels. The initial testing was promissing. We’ll know some time this week how well it really works.

the team wants to hit the top portal. I’m thinking based upon the design, we’ll do well on the lower, the cargo ship and the 2nd portal. We’re able to pick cargo off the ground as well as hatches. Our hatch mechanism is tough enough to get us started onto the 2nd Hab then our wheels get us to the top. Just have to drop the middle wheels so we don’t get high centered and we should be good to go. We kicked around different ratios yesterday. We just weren’t sure if the balls could withstand more compression. They’re fairly fragile in my opinion.

If you are aiming for the top Portal, you need to follow the prescription Mr_V gave. He is recommending a lot of what I found the top shooters at Houston Champs 2017 were doing.

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