What the title says. Is it like the scale where a slight touch will cause rotation, or more like what I assume the control panel this year is like (harder to rotate)?
It’s hard to say without a real field or even a practice field experience, but this video (minute 1:44) might give you some intuitive sense.
That calculator is for balancing, whereas OP is asking about friction/ease of movement
2 Likes
If I read it correctly, the team version field drawings basically say to wrap the pipe in a couple layers of duct tape or electrical tape or gaffer’s tape and then U-bolt over it. Kinda janky and not very specific. I’m not sure what the actual pivoting interface is on the real thing. Anyone know?
That’s to hold the pipe rigidly against the frame, in place of using a proper 90* coupling.
You could read the Field Drawings 
https://www.firstinspires.org/robotics/frc/playing-field#FIRSTdrawings
The pivot motion is contained at the interface from the large sheetmetal structure to the 1.5" powdercoated steel tube, with an Igus slip bearing (PN in the drawing set) inserted at all points of contact.
In the team version, the black pipe rotates against plywood. First order guess, that’ll be similar to powdercoat with IGUS bearing - similar enough that the home field might have more friction than a comp field.
I’m pretty confident making our Practice Field out of galvanized pipe with direct plywood to pipe contact will yield a more-slippery joint than the real field, and I prefere to make the challenge harder for us at home and easier at comp.
(And I’ve already bought a galvanized pipe, it was easier to source than black 
)
The drawings are here.
The hanger pivots on 1.820 - 1.825 diameter thru holes in 0.18 thick 5052 aluminum sheet (GE-20010-01). The hanger is supported on a pivot pole made from 1.5" o.d. DOM (steel) that is powder coated to 1.525 max. o.d. (GE-20013). The space between hole and pole is filled with an IGUS bearing (GE-20021, IGUS part MFI-2428-12). The complete assembly (GE-20020) includes six of those bearings.
EDIT: checking the IGUS datasheet, it appears we can expect CoF about 0.3 un-lubed, decreasing to about 0.1 if greased. Guessing that the hanger assembly weighs about 83 lb (one hanger GE20010 @ 67.14 lb plus two GE-20011 braces @ 7.63 lb/ea), the friction force on bearings will be about 25 lb un-lubed, and corresponding damping torque will be about 18.5 lbf-in.
The other factor influencing “touchiness” of the hanger is its moment of inertia, which is best calculated using the CAD model (I don’t have that handy now).
3 Likes
This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.