I made a catapult bot but it has problems with it I need help to figure some out and how to fix 'em.
I have pictures below and a link to something with videos of some games because I can’t put them on forums. I am very aware of the treads though I’m in the middle of fixing that.
-Use bearings on all places where the shafts (low strength and high strength) go through metal. Especially where your catapult pivots and on your drive.
-Don’t use steel too much on your robot, as its very heavy. It is good for parts of the robot being put under lots of stress or force, like a catapult hard-stop or the catapult arm.
-Make sure you support any moving joint (shafts or screws) on two sides to prevent the shafts from bending, especially on your drivetrain.
-Make the catapult wider and maybe a little shorter, by having a wider catapult around the same width as the triballs you don’t need to make a holding tray at the end of your catapult, which reduces the overall speed of the catapult when it is throwing the triball.
-Make the catapult a bit faster, when my team had a catapult we geared it 12:33 so it spun the catapult at 33rpm, we found the speed and strength of this gear ratio to be very good for matchloading.
-Box anything attached to flanges of the C-channels, do this by placing 7/8" of spacers between the two flanges of the c-channel, I’ll leave a video explaining this and other building concepts below.
Despite some of your flaws, you still have a very decent bot and trying to make your robot better is the true spirit of a vex competitor. Changing parts of your robot allows you to learn more about other building techniques.
If you want or need any further help my discord is bbfarms#1524 I would be very happy to give you some tips and help with anything robot related.
Videos about building techniques:
Ok this link should work
When I click on a video, it states that I need permission to access this video.
On another note, as you try to change your drive base to use wheels, I would recommend looking at this Catalogue of Drive Gearings for different geartrains. I would recommend switching to at least a 4 motor drivebase, as that is the competitive minimum. For this game, I think that it’s necessary to have a drivebase with your wheels relatively close together if you want to be able to go over the barrier. I would recommend checking out 450 RPM on both 3.25in wheels and 2.75in wheels, as well as 360 RPM with 4 3.25in wheels.
As for general advice, I think that @91416N’s advice is very good with 1 minor exception.
12:33 gearing doesn’t exist, so I’m assuming that he meant 12:36. Your catapult appears to be plenty fast (the same speed as 12:36 gearing; catapult speed is correlated to the speed at which the slip gear spins, so if you power the slip gear with a red cartridge it will have the same speed if you don’t account for torque), as I have the same design (36:84). If you do decide to rebuild, I would recommend switching to a 12:48 gearing, a 24:72 gearing, or a 12:36 gearing to give the same speed of launch while having more torque to pull back on the catapult with, but other than that your robot appears to be really good.
GLOU! (Good Luck in Over Under)
I got the videos to work I think and thank you for the advice. There is a problem though, I do not know how to read gear ratios do you mind explaining it to me so I can understand it more. We are putting the wheels far away from each other for now just because we work well without ever having to cross to the other side, but I will probably fix that after my next game which is in three weeks. Still though thank you.
There are numerous resources to learn about gear ratios, but the basic premise is that as the rpm of the motors go down (which you can think of as speed), the torque will go up (which you can think of as power). You can adjust this using gears. Some mechanisms, like flywheels, don’t need very much torque but they definitely need a lot of speed while catapults don’t need as much speed but definitely need more torque. For a drive, you ideally want a good balance. Competitive drives can go all the way from 250rpm to 600rpm based on wheel size. If you would like to learn more about gear ratios, the link I’ve attached below is very helpful to give a basic understanding of gear ratios.
Hope this helps!
I do understand that. It is the ratio itself that confuses me for instance 12/36, but thank you for the help and link.
Nahhh really?!
I’m just kidding, my team is actually currently utilizing the 257RPM drive. I was just attempting to give them a general idea about the range of drive speeds.
Oh no I wasn’t talking about using it. I was just using it as an example of the fact that I don’t know how to read ratios if that makes sense.
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