Need some suggestions on how to attach our slingshot to the drivetrain. We’re thinking we may need to build a platform of some kind.
You can take the anti-slip mat off of those 1x5 c-channels (as it will create a lot of friction that’ll decrease the range of your triball) and use that as your platform, then mount your puncher out of the way of your flip-out intake.
Nice to see that your bot evolving!
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Banjoes.
By inserting a coupler into a shaft collar, you can create very versatile bracing joints. (see the variety of ways we used them on our robot) The banjo allows you to create braces at odd angles when screwed into a standoff. (the standoff being the primary structural member) If you use two banjoes in tandem, you can mount/brace something at any arbitrary angle… see our first picture.
From our school’s coach:
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If you make banjos you have to tighten the set screw against a short piece of shaft. If the thread is not tight, the loctite won’t cure properly. Tighten against the corner of the shaft, not the flat. When you take the shaft out, a short twist will loosen it. Then you have to run a drill through the hole to clean it up. It takes a numbered drill. #19, I think. You want the size that just matches the ID of the shaft collar.
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Use red locktite, and let it cure for at least 24 hours.
I prefer using banjo-standoff bracing as opposed to something like the below image. In the case of the below image, the use of bar is not bad since the bar(s) will only be under tensile stress. Banjo-standoff combos on the other hand, have great tensile strength aaaand a decent amount of compressive strength (though not nearly as much as the tensile)
View of rubber bands on a catapult, courtesy of 99904A – taken from BLRS Wiki.
Of course, there are probably a couple of other ways you could do this… but I figured I would let you know it’s an option – they could com in handy to you later on.
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So your saying mount the rear of the slingshot where the motor is mounted to the platform with the kicker pointing towards the intake? Two thoughts I have. Will we still be able to go under the barrier? And will it have enough arc to kick the triball far enough?
Sorry if it was confusing, but I was thinking a position similar to this:
The match loaded triball would be placed where the green triangle is. If you’re concerned about the arc, you can put a ramp here so when the triball contacts it the ramp “kick” up its arc.
For mounts, put screws through this stationary c-channel onto those 1x5 c-channels and use standoffs to connect various other parts of the slingshot to your drivetrain.
However, do take this all with a grain of salt. I can’t really help build well without physically being there.
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It makes more sense. It’ll be later this week before we can continue working on this project. The next issue will be whether we can operate the arm/intake without interfering with the slingshot. The arm/intake has to be in the upright position for the inspection.
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Replaced the platform where the triball will go. Still not sure how I’m going to attach the slingshot.
Why are you using the hero bot? Just asking. Those hero bots have never been effective in my years of vex.
“By inserting a coupler into a shaft collar,” Just to be clear, is this a screw with the head cut off?
Also by drill the hole do you mean to drill the hole where the shaft goes?
Yes and no. Vex sells couplers, but yes they are basically topless screws. However, they do have an imprint in the middle that allows you to tighten them with allen wrenches/screwdrivers, which is a lot better than my last year’s sister team that tightened a screw and cut the top(and now we have no idea how to get the body off).
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We started at the beginning of the year with a hero bot since we are a first year robotics team. Since then the team has been working on modifications. They thought that would be the quicker option instead of starting over from scratch.
Essentially, yes.
The only difference between a screw with its head cut off and a purpose-made coupler is that the coupler will have a tiny t-8 (or hex) socket in the head:
the socket allows you to tighten the coupler against something.
Here is the product on the VEX Store:
Also yes. 
After removing the shaft by twisting the shaft (don’t loosen the coupler, that undermines the purpose of using Loctite)… the end of the coupler will be blocking the hole the shaft was in. It isn’t blocking it by very much, but it is enough to prevent the banjo from being used. To clean up the hole, we simply drill it out – knocking off the tip of the coupler.
We are on a time crunch. Our next competition is next Saturday. Besides using Couplers, what other options do you think we have to attach the sling shot?
Ahh. Honestly, I recommend just building a simple 6 motor 333 or 360 RPM drive train for beginning teams. They balance good speed and good torque. This season we started with a 4 motor 333 RPM drive and it had no pushing power. (Because of the 4 motors)
Good point. Beginning teams should also build 2 simple sets of wings, a simple lift-kicker, and a simple intake. They should also code a simple 6-triball auton and a solo AWP auton.
What I’m trying to say is that as you get better in VEX, things you feel are simple now are more complicated to less experienced teams. I’m not trying to say that building a 360 RPM drive is hard per se, but just that it can be overwhelming to new teams.
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Awesome, i figured that was the reason I just wanted to clarify verbiage. Thank you!
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Slingshot is attached. Low enough to go under barrier. Two issues, not enough power to launch triballs over barrier. 2. Need to slow it down.
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What cartridge is inside the motor? (Red, green, blue). Those two problems are a result of a bad gearing. Try using a bigger size gear for your slip gear (pulls back more) and adding 2 more bands.
We’re using 11 watt motor, I believe it’s green. Not at at school right now to look at it. We thought about adding a larger slip gear. We tried adding more rubber bands, but it won’t do anything with too many rubber bands.
Try using a red cartridge.
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