Ball scoring issues with Indexer

VEX Robotics Competition Discussion VRC
#1

I am building a Hood bot with flipout intakes and a pooper. The issue I have right now is that the ball is not going into the goal at all. I tried different configurations and I am unable to figure out why it is not working. The ball gets to the top of the intake fine, but it doesn’t have the momentum to go into the goal.

Pictures will help describe my by problem, but I can’ t get into the at the moment and will post them as soon as I can.

Please tell my anything I can try to fix this issue. Thanks in advance

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#2

whats the rpm of your flywheel

#3

the important factors are hood angle, roller speed, and compression.

you want a decent roller speed, at least 1000 rpm. The compression should be enough to force the roller to transfer a lot of it’s energy to the ball, but not too much that you start to lose power. Rubber band rollers and having a but of spring in your hood helps. As for the hood shape, a lot of different types seem to work. I use a curved hood that curves around the path I want the ball to take, but I’ve seen straight hoods that are just plates tangent to the desired arc of the ball work as well. I think the curved ones are probably better as they have fairly uniform contact with the ball, but the flat ones do work.

Build quality might also be a factor in your problems, if you have excessive friction in your rollers you won’t be able to shoot the ball no matter how good the rpm and hood geometry are.

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#4

It was at 200rpm, which is the issue.

More RPM made a huge improvement. i went from 200 to 600 RPM by changing the motor cartridge. It helped to an extent to where the ball goes in half of the time. Instead of using a 600 rpm motor, is it better to use 200 rpm to and gear it to 1000 rpm?

Curved hoods seems to be more consistent,

Here is a video of one of the times it did not work:

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#5

You could use a 2:1 chain ratio with the 600 to get it at 1200 rpm. Anything above 1000 rpm (but not too fast like in TP & NBN) should be fine

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#6

That is something I will try.
Would that be better or a 6:1 ratio at 200 RPM. The motors were overheating quickly at 600 RPM so I’m guessing that 200RPM motors are better here? Please correct me if I’m wrong.

#7

First, you should make your top roller faster. Also, it looks like your top 2 rollers are too close together, and the ball gets caught on a shaft which makes it lose all its speed. You could also probably stand to make the hood open up more towards the end so the ball is launched a little bit higher rather than straight into the rim.

600RPM should be fine. I’d bet the main reason they burn out is because the ball gets caught which puts a lot of extra stress on the motors, but you should also check for friction. It’s a bit hard to tell if there is any from just the video, but if you haven’t spent any time tuning it out then there probably is some. You also can’t get a 6:1 ratio from sprockets without compounding or using gears, and extra joints create extra friction.

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#8

the ball seems to get caught on the hood. having a smoother shaped hood and still faster launcher would probably help, though with better geometry 600 rpm could work.

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#9

How tall is your top roller? It might help to raise it up 1-2 holes if you have room.

#10

It is at the highest it can go. I if I move it one hole up, it would help, but then it would be out of size.

#11

Hey everyone. I thought I would post an update here. I was able to get it to work well now.

It is important to consider what everyone has said here. The rollers have to be fast, but they do not need to be unnecessarily fast. I went with a 200PRM with it at 15:6 motor for the main rollers and 600 RPM for the rear roller motor. The hood angle was key. The placement of the rear rollers was also important. It is also important for there to be the least amount of friction possible.

Thanks to everyone who helped me with this.

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