Thanks for all the positive feedback, especially GeeTwo who really combed through this thing and put a lot of time into making improvements.
Roboting: A Guide for Total Noobs 10.5 (Revision list 11/12/2018)
The following is a list of corrections to be made in the next revision of this document as suggested in this thread.
Note: this does not include photo credits (and text credits, where and if applicable), which will be determined before the next release, after the below changes are made.
• suggest adding flex wheels to the wheel section! They’ve got tons of options in durometers and sizes, and are fantastic for intakes and other roller subsystems.
• I’ve noticed some of my own photos and resources thrown into it (Specifically the latch section and those immediately before and after, as indicated by choice in photos.), as well as that of others that I’ve used in sources I suspect you used.
• You openly admit that it’s incomplete; In a more complete version, do you intend to link / reference the year & team of the robot you’re exhibiting a feature of? I specifically did that myself in my own resources, as I knew that some people wanted to do additional research on their own, and a team number and season is a good starting point.
• Just as a suggestion that will help teams make weight - not all gears need to be steel. My team has found that most gears are fine as 7075 aluminum (a la VEXPro) and typically we only need steel gears for very high loads (ie catapult crank, pinions).
• Also, I highly recommend the pixy (https://pixycam.com/pixy-cmucam5/) as another camera option - its cheap and easy and makes vision tracking very accessible.
• The slide on live vs dead axles is particularly troubling.
• The descriptions of using omni wheels in tank drives seems inconsistent as well with some of your example photos.
• You also mention a limit of only 4 air tanks on a robot that hasn’t been in the rule book for over a decade.
• A lot of FTC specific items get used in example photos that don’t really make sense, like tilerunner.
• Under the wcd you mentioned “held in place by bolt-on stel blocks” none of the designs you showered were steel, and I don’t think anyone has ever used steel in a wcd bearing block
• Motor section under 775pro “Will let out magic smoke if stalled for more than 15-17 seconds.” If you stall anywhere close to full power, it’ll melt in under a few seconds as tested by vex.
• Under “Brushed DC Gearmotors” you have a Neverest 60/Window motors under “higher toques” which also isn’t really true. As any of the common motors will be much more powerful with a gearbox (which are easy to add).
• The NIDEC motor isn’t even close to “lightweight” for the power you get out of it nor “efficient/consistent”…
• 2: table of contents.Not sure if you have enough authoring software, but having links here would be awesome.
• #12, Control System overview - looks like you reused the title from #6. How about “Components which turn the designers’ and driver’s choices into what the robot does.”?
• 14: Make the point here that two support points are needed for cantilevered axles, and that the bolt-on blocks provide these.
• 15: This does not agree with my understanding of “live” vs “dead” axles at all. Your description is of “driven” vs “undriven” wheels. What you show on the left side front and rear is only a “live axle” if the sprocket/pulley drives the axle, and through the axle, drives the wheel. A wheel with a “dead axle” may be driven through a sprocket or pulley coupled to the wheel directly, with the axle only serving as a pivot point for the wheel to spin about. The KoP chassis has what I would consider “dead axles” front and back, though all those wheels are driven.
• 21: Pebbletop is noted primarily as providing a better coefficient of friction in the forward/reverse direction than as a scrub force – ON CARPET. It works as sort of a paddlewheel in a carpet situation.
• 29: Another con of ball casters is that they cannot be driven, or at least not easily.
• 30: Major con of track tank drive is possible inability to turn, esp if track length is nearly as long as or longer than the spacing between the tracks.
• slide 34: I would have three classes: skid/steer (what you call tank, and is also called differential these days), Holonomic (which would NOT include crab/swerve or octanum), and actuated/steered wheel drive trains (crab/swerve, octanum/butterfly, as well as auto/fire truck steering).
• 34+: Another actuated drive type I haven’t seen much lately is “lobster”. This is typically a second set of skid/steer wheels perpendicular to the primary which can be pushed down to lift the main drive off the carpet. Sometimes the motors/gearboxes are re-used through bevel gears or other similar system, sometimes there are duplicate drive trains. There is also a butterfly variant called “grasshopper”.
• 37: 4W tank may be four “solid” wheels, provided that the wheelbase (distance from front to back wheels’ interface with the road/carpet) is less than the track width distance between left and right wheels), assuming the same CoF in the forward vs sideways directions.
• 39: Pro: better at handling ramps and other irregulatities than 6 wheel, less likely to high center. Also: may have wheels on a plane, provided corners are omnis.
• 41: using pebbletop on the corners may also meet this method.
• 44: I think you underestimate the difficulty of programming heres vs holonomic (omni/mecanum) drive trains; you make holonomic sound harder than swerve.
• 45: I would state that this is often called “Killough” in FRC. It is equivalent to Mecanum, apart from the gearing - Killough must be 42% faster to be truly equivalent to mecanum. (Confusingly enough, in FTC and Vex they use Killough to refer to kiwi.)
• 47: I think you’re understating the “pros” of having three wheels. Kiwi is remarkably insensitive to irregularities in the drive surface, compared to mecanum or Killough/X drive.
• 48: Slide drive - Based on experience in 2015, I would never recommend a “fixed location” strafe wheel. Find a way to define how much weight the strafe wheel supports, e.g. through a pneumatic cylinder.
• 49: I would consider Octanum/Butterfly less complex than crab/swerve.
• 50: Here is where the rubber meets the road on Holonomic vs steering wheel drive systems. Steering wheels (swerve and crab) do NOT experience reduced pushing power. Their complexity, however, is even greater than holonomic
• 54: Cons: can be hard to work on in the pits. Let me point you to a couple of mitigations I posted here: https://www.chiefdelphi.com/forums/s...d.php?t=166642 to simplify wheel and motor replacement.
• 59: Should also note that welded joints are not repairable at competition.
• 63, and nearby: 6063 (and 6061) are best noted for extrusions, and 5052 for sheet metal parts. 5052 is capable of being welded or bent without losing much strength, but the strength of 6061 and 6063 are greatly dependent on annealing and are reduced by bending and welding. 6061 is generally what you’ll get at hardware stores and home centers; it is better at corrosion resistance, but less machinable than 6063, which is generally preferred for robots.
• Let me state that I do not have a lot of info on plastics, so I have let this section go.
• 95: Scissor lefts can be made far more linear (bypassing the problem you note that “loads very high to raise at beginning of travel”) by lifting at a different pivot point. If you lift at the pivot directly above the fixed point, the leverage/gear ratio becomes constant.
• 99-101: I’m not entirely sure what point you’re trying to make here.
• 104, etc - I noted a low emphasis on “intake mechanisms.” These are usually at least as important as “moving” and “shooting” mechanisms.
• 106: note that if your claw has rollers on both sides, they must move in opposite directions, requiring either two motors or a bit more complex gearing.
• 112: note that intakes and shooters may sometimes be the same mechanism.
• 121: I didn’t get quite what the point of this one was.
• 125: 1.0 gallon air tank max? where is this from?
• 126: Max of 4 tanks? where is this specified? 3946 used 7 tanks this size in 2013, and I saw more on other robots then and in 2015.
• 128: Most solenoid valves are “air piloted” - this means that air actually does the main switching, so they need a minimum supply air pressure (typically 30 psi) to function properly.
• 131: Would emphasize Pro #6, “can maintain position at stall without failure”.
• 137: last bullet: Rules require one ESC per motor capable of 100+ watts of power. (Note 100W is not the way the rules are stated, but this is effectively what they are according to the motor/controller lists)
• 138/39: A bit out of date - the motor normally preinstalled on AM PG motors has always been an RS775-15, though the 9015 (RS500) was available as an option. AndyMark doesn’t sell the 9015 any longer.
• 157: introduction of planetaries with no reason as to why these are not mormally used for drivetrains. One of the big ones is that they are rather sensitive to transverse loads on the output shaft, and another is that most PG gearboxes used in FIRST use the smaller 32dp gears. Planetaries are more sensitive to radial forces because they usually only have a single bearing at the output, or perhaps two bearings next to each other. Providing a bearing at the end of the shaft would definitely mitigate this problem, but would not resolve the issue that 32dpi teeth are smaller and thus more sensitive to shock loads breaking them than 20dpi teeth, other things being equal.
• 163+: transmission - no reference to using a shaft to transmit power
• 166: reference to #35 as “standard bike chain”. Bike chain is 1/2" pitch (#40), #35 is 3/8" pitch.
• 168: “[belt] does not stretch like chain.” Chain doesn’t actually stretch, but rollers do wear in, which results in chain appearing to “stretch”.
• 171: cool - wasn’t familiar with this at all!
• 185: I think the title should be CAN motor controller. Bullets 3 - suggest “as an alternative” rather than “as well”, which implies it can do both at the same time.
• 186-7-8: way more detail than most will need; I suggest some TLDR tags.
• 206: here, when covering wire gauge would be a good time to talk about sizing wires to breakers and fuses (2018’s R59). Even if they don’t remember specifics, team members need to know this rule exists, and is for safety.
• 222: single turn potentiometer shown; multi-turn potentiometers usually have the wipe at the end farthest from the shaft.
• 224: TLDR: Actually, I think it’s more like couting spokes as most encoders count many times per revolution.
• 232/234: I would also include non-laser IR sensors. At short ranges (up to about a foot), they work great and are much less expensive than short-range ultrasonics or LIDAR. Sharp (the copier company) makes some great, dirt cheap (many less than $5) IR sensors of both the beam break and rangefinder style. Sparkfun, Pololu, Adafruit, and RobotShop all carry many of these, sometimes with carriers to simplify connecting them to a DIO or Analog Input.