Hello everyone,
I am designing a cube scoring mechanism with a KOP chassis. The first iteration is made of plywood and consists of one spinning roller and a rotating arm.
I am in the progress of building the mechanism and I don’t know how to mount the arm rotational motor. Any ideas?
I have Neo 550s with 100:1 Sport gearboxes and an assortment of different length 15mm HTD Timing Belts. Would also love to know how to CAD the timing belt in Onshape.
Thanks, Adam
There is a hole directly below the rod that the arm rotates about – my suggestion would be to mount a motor and planetary inward from that hole, passing the output shaft through the hole, and then use a chain&sprockets or a belt&pulleys to connect your shafts.
I like your design; if I may offer a thought, if you make the arm longer and mount it to the back of your robot, it might be able to reach the mid and high levels.
Good luck, and please post pictures of your finished creation. We’d love to share in your successful build.
Adding onto this, don’t transfer the arm torque through the hex shaft. Bolt the driven component (sprocket, pulley, or gear) directly to the arm plywood.
Also, are the intake 550s on a 1:1 ratio with the intake? If so I would either switch those to a 3:1 ratio or move to full-size NEOs. 550s don’t produce a lot of torque at low currents and cannot be stalled for very long at medium to high currents.
Thanks for this suggestion. And yes, the 550s are on a 1:1 ratio with the intake. It seems to be sufficient, but probably not the smartest to run long term.
As a rule of thumb we like the linear speed of an intake “wheel” like that to be about 3x our robot’s max forward velocity (so it’s still moving a piece inward if we run into a piece at speed).
A 550’s free speed is something like 11,000rpms and at 1:1 if those stars are 4" diameter they’re going to have a linear velocity of about 180 ft/sec. Assuming a top robot speed of about 20 ft/sec, I would recommend a 3:1 planetary as a starting point to get them to 60 ft/sec.
As John suggested, use a chain and sprocket to get the last part of your reduction ratio. It is much more durable than the gearboxes. This will allow your arm actuation motor to be mounted lower, near the top of the chassis, so it is less prone to damage. You may want to add a protective shield. Is there a reason you are using the NEO 550’s to actuate the arm. My gut feeling is that a NEO would be more appropriate and more durable. We have fried NEO 550’s when they were stalled.
It may be good to add some shielding for the motors for your intake wheel/stars. Is there a reason you are not using a single motor for your intake? The weight of the second set of pulleys, belts and motor controller are easily more than the weight of a larger motor like a NEO.
One quick suggestion is to add some small free spinning omni-wheels to the bottom of the intake. With the omnis touching the ground, the intake/robot will move and turn much more easily. You could just program the intake to never touch the ground or make a hard stop to avoid issues, but the omni-wheels are an easier fix.
I have two questions.
1- Is it accurate when shooting the cube to the top or middle ground?
2- How many millimeters is the compression ratio in Intake?
I love the idea of the omni wheels! I’ll try printing some on my Ender 3. 
Good questions:
1- I’ll start by scoring only low nodes, but could potentially iterate the design to score mid/high. I do not anticipate that this will be accurate/consistent with only one powered roller.
2- No clue… I’m going to guess and check 
(would appreciate suggestions)
Great ideas!
I am using 550s on the arm rotation rather than regular NEOs because I have 100:1 Sport Gearboxes available to me right now. Currently, I have a single NEO 550 powering the roller. While this does technically seem to work, I will definitely swap it for a single NEO instead.
I’ll send a design update soon with physical pictures. My goal is to get this first iteration functioning, and then make improvements from there.
My gut feeling is that you would still want to reduce the speed further, regardless of the motor used, if you are using the 100:1 gearbox.
Plug in the numbers to the recalc online calculator to see what the arm travel time is.
I have no ideas for the rotational arm other then what was said but for the timing belts my team uses two resources. 1. There is a tool in onshape called "FRC belt calculator ", this lets you chose two points on a drawing and tell you what the best common belt is for that distance though you might need to make some changes to get it working perfectly. 2. We also use a belt calculator from West Coast Products to figure out what we need.
The neo 550 is an inadequate engine for the intake system on its own (you will probably smell burning after 2-3 days). I think you should design a gear that fits perfectly on the 550’s cover and proportion it to drive another shaft. You can drive the intake directly from that shaft, it will be more efficient.
This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.