Martin's virtual NBN 18'' robot -- Shifter

Martin’s virtual NBN 18’’ robot – Shifter

– This is a virtual robot design reveal thread, you can directly skip to the images if you don’t feel like reading my thoughts, which is completely okay. –

So after 2015 worlds, I was struggling about whether to open up Inventor and design a robot or not. On one hand, I have these ideas about flywheel and transmission that I wanna at least simulate in computer; on the other hand, I am well aware that probably I am never going to build this design in reality, because the chance of me going into VEXU this year is, well, very slim. Sometimes I fail to find the meaning of me designing a machine that will never be built and tested. However, I still feel that although this is not as fun as actually competing, this might be a good way to give some new people some ideas about designing their robot. Or even some Inventor design tricks. Also, this is more fun than just doing nothing in summer.

I started to mess around with Inventor a while ago and found much frustration. Back then my inventor skill was still limited to just stacking one part on another in a way that changing one part would mess up everything else. Which is not a particularly helpful method when I have no physical parts in reach, and the only thing I can do is to imagine and sketch.

So a few days ago I figured out and picked up some more decent designing skills. More specifically, using a master sketch and try to utilize the origin geometry of parts as much as possible, in order to make parts more independent of each other. Knowing how to do these, designing completely out of nothing is made easier, and some of my ideas are becoming manageable in the design window.

Enough about Inventor, let’s talk about the NBN robot I’m about to make. Pretty soon after NBN came out I decided to fix my design on flywheel, because it’s more of a challenge – a speed never before achieved in VEX. I am aware that flywheels with speed like 20 or 30 RPS will probably need a lot of power, which means they need motors. Also the base needs power, because possibly we might see robots pushing each other to get into that ideal sweet shooting spot or to interrupt an opponent’s shooting.

Well all of the above is probably not the most accurate analysis of the competition environment – I am aware that by the end of season we might find that we never need to push anybody. Or that maybe flywheels are not the best choice. I mean, for me, VEX is just a journey of pursuing one cool thing after another. So far I have done wireframe scissor lift and double reverse six bar, which are decently cool. I have not yet made a transmission or a launcher. And that’s perhaps the main reason I want to design a crazy transmission and a flywheel so bad.

Okay. Enough of why I wanna make this. Let’s look at my straight-forward idea:

Base: 4 motors, torque gearing. A pneumatic transmission shifts it between 3:5 and 5:3.

Flywheel: 4 inch diameter flywheels, vertically placed, 45 degree trajectory angle. powered by 4 393 motors, torque gearing, 1:15 external gearing. Has a ratchet and pawl. Has a ball feeder window that can be opened by pneumatics.

Transmission: two sets of pneumatic gear shifters can detach the flywheel motors from the flywheel and hook them up with the base.

Intake: 2 motor regular top roller intake and conveyor ball feeder.

Pneumatic brake: I wanted to do a 4 piston complete lockdown… but considering how much air I am consuming already I’ll make do with whatever brake.

Okay, I think I have done enough talking… Now let’s bring on the pictures:

The base transmission. I think… I may have posted it a while ago?

Powering motors of the base are directly attached to the gear that’s sketched out but not put in.
transmission 2.JPG
transmission #1.JPG
transmission with sketch.JPG

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The launcher/transmission design:

The big 84 tooth gear on the top is the ratchet. The 84 tooth high strength in the middle is where the flywheel/base motors will go. The 36 tooth and 60 tooth directly above and below it are the shifting gears – when one hooks up something, either the base or the flywheel, the other idles.

Notice that I have not yet put in a lot of structures, just the gears lined up on the axes in the sketch file. This is the method I found very helpful – making gearing precede structure design, and making them independent from each other.

Structure is the thing I hate the most in VEX, because it always drives me crazy… the c channel’s total thickness is always 0.5 + 0.063 inch, which can drive me into nuts sometimes. I find that making the structure first, then putting gears in the holes a very stupid idea. Because structure design is something you need to spend time to ensure the strength and efficiency. You need to change it a lot as time goes.

Before you know where the gear tower should be, model where the gear should be and then design gear tower accordingly. That’s my tip of designing in inventor.
bot #3.JPG
bot #1.JPG
bot #2.JPG

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This is a very interesting design Martin. If you decided to not use the pneumatics with your design, what would you use the other two motors for?

We have a meeting tomorrow and I am still trying to figure out which option I should stick with for the early season!

So I have to say, I built my first transmission this year and they are tough. I designed it to be powered by 3 motors pet side with a pneumatic shift. I’ve never had so much issue with connecting 3 motors to one output gear. Just a tip, I’d keep everything linear. The transmissions have a lot of slack in them too. Meaning the wheels can move another inch because all the axels are finally locked in each gear. I’m hoping the added advantage of speed and power work well this year and I wish you the best of luck with your design.

Hi, how are you guys planning on lifting robots?

I like the idea of a vertical flywheel design, have you tried using different types of spin by speeding up or slowing down one of the flywheels?

I’m also collecting data on the accuracy of different launcher designs, do you have data on shots hit over total shots taken?