Before I start, please tell me if I should create separate topics for each thing… still very new to VEX forums.
Our bot has just gone to its first scrimmage, and a lot of things went wrong, so I’d just like some feedback or advice on a few issues.
Our drivetrain keeps loosing parts such as collar screws or even collars themselves, yet do to the nature of the drive design it can take about ten minutes to fit the screw back in. Any tips on how to avoid either screws falling out or adding more space?
Pneumatic nuts keep loosening and falling off. This throws off the balance of our intake, which extends with a pneumatic.
When bots ram into us, our rubber bands tend to snap, rendering our catapult unusable. In our first match this happened, and our catapult was so weak that we ended up scoring 10-15 tribals for the other team.
Whenever our bot goes over the bar, it falls on its back and “turtles.” Would it help to add sleds in the middle of the drivetrain rather than the front?
Our ratchet is not very stable, and has about a 50-50 chance of working. Due to this, it’s very hard to get under the bar.
Let me know if I can be more specific, send photos, or if you need clarification on anything. I’m very new to VRC, this being my first year and my first comp. Thanks for advice!
Hello, thank you for your descriptive post, and I’ll try to do my best to answer them.
A picture here would be useful. However, if your drivetrain is braced well, try to put your shaft collars between the c-channels. Also, try to use screw joints and nylock nuts instead of shafts as much as possible as they are much more durable.
Yeah I don’t have a solution for this other than tightening them before each match.
A picture here would be helpful. Try to position your rubber bands in less exposed area or put a c-channel in front of it to take the hit.
This is caused by your center of gravity being too high or too far back (relative to your barrier sled). Try re-positioning your pneumatic tanks and or motors lower and more towards the center of your robot.
We need a picture and more detailed description to help you with this one.
Are you using any lock tight on the shaft collars? if you are not then you should, it will keep them nice and tight. For your pneumatic put lock tight on where the nuts are, not a lot because if you put too much you might not get them off. Put rubber bands in a safer place so they don"t get hit and break. Sounds to me if you put sleds on your robot then you should put them on the back of your robot. Since you have more weight back there then the front. I would rebuild your ratchet like this one. Or it can be similar to this. If you do redo your ratchet then put it in a sturdier place then it was.
Here are a few photos of our drive, the photos our slightly outdated but in the current version we have collars in between the c channel and motor. Those are the collars that are very hard to get to.
For your drivetrain issue,
Put shaft collars where the green boxes are. Do not put shaft collars where the red "X"s are, as those are very inaccessible.
As for your ratchet, I would use a regular high strength gear, not a sprocket.
If we were to put the shaft collars on the inside of the drivetrain, there would be no way to keep the outside c channel in place. I originally had this design, but struggled with a way to keep the channel in place.
The reason we had to dremel of a hole for pneumatics is due to the very tight spacing from our catapult. It wasn’t the most elegant fix, but we had about 2 days to add in pneumatics and I didn’t want to take apart the drivetrain and cata just to add more space to the brain.
I tried this but for some reason the screws on the pistons are a different size on the usual allen and star screws. Maybe the VEX V5 pneumatics kit fixed this, but I only had access to a few SMC pistons and reservoirs, and whatever connectors and electronics I could find from either SMC or VEX.
Creating separate topics for each thing might be a bit of a hassle to post and answer, so I think it’s easier to create one topic. I do appreciate you asking though.
Could you possibly send a picture so that we can see this tightly spaced drive? This is one of the cases where a picture is worth 1000 words.
For this, I really do just think you need to tighten these more. Just grab a wrench and maybe some pliers and get to work.
What type of rubber bands are you using? Are any of them fraying? How much tension are you putting them under?
First of all, I think that the sleds need to be on the front regardless. However, you might still find sleds in the middle helpful to help you glide over the bar, similar to Gremlin.
I’m going to pop my head into this topic to clarify something. You need to attach the outside c-channel to the rest of the robot frame using a crossbar. These are pieces of metal that hold the outside c-channels and the inside c-channels together.
That’s a good idea, however due to the intake and catapult being situated at the front and back respectively, the only places to add crossbars are in the middle, which isn’t optimal. And due to the nature of the spacing in between the channels, the holes would not line up for a crossbar. Writing this now I realize that I should probably adjust the spacing, so do you think it’s better to try and cut down on spacing to go for five holes, or add a little to make it 6?
Also, is having a crossbar in the middle as effective as having two on either end? It would seem not, but I don’t have a lot of VRC experience, so I can’t say for sure. Our robot is not present currently, but I will be able to test more things tomorrow. (hopefully) Thanks everyone for your input! I will move the collars inside the drivetrain.
I second this.
This year was my first year building a competition bot, and I did this. The c-channels ended up flexing outwards like this / \ and created a lot of friction. It also led to gear mesh problems.
Use standoffs and some c-channels to brace your drivetrain
It’s better to have the crossbar at the ends, but if you can’t have one at both ends, then one in the middle and one on either ends is fine. But if you can’t have a crossbar at either end, then put a crossbar in the middle and connect the outside c-channels with a standoff or a c-channel to stop it from flexing outwards and creating friction.
I would recommend 6 because In my 2 years of VRC I’ve never seen anyone fit everything in 5. It might be doable, but it’ll probably just cause more friction and other problems.
I mean, I could try and switch it to LS gears. I don’t know if they make them in 36 and 48T but I could always just use a hacksaw. I’ll be sure to add some bracing on our next bot.
