4 vs 6 wheels (what to choose)

[Teched3]

IMO, mechanum is a difficult task in programming during the build season, even for very experienced teams. Stay within your capabilities. Wheels are available through AndyMark, so the mechanical requirements can be met if you have the funds. Use the offseason to develop new systems and concepts. I have been in this fo 16 years, and am still learning. Just my opinion.

[Grim Tuesday]

You can't strafe with 6WD, you have to tank drive, which if hanging pegs, involves backing up, then turning, then going back.

[apalrd]

Originally Posted by Grim Tuesday

You can't strafe with 6WD, you have to tank drive, which if hanging pegs, involves backing up, then turning, then going back.

Not if you align to the pegs while approaching them, and not after you hit them.

Many people around here seem to be saying "oh, oh, a mecanum is sooo much more maneuverable, omg" when a well-driven 6wd can do everything except strafe, and is easier to build since everything comes in the KOP (and slightly easier to program, although the WPIlib has mecanum code for you)

[AustinSchuh]

Originally Posted by Grim Tuesday

You can't strafe with 6WD, you have to tank drive, which if hanging pegs, involves backing up, then turning, then going back.

If you are within about a foot of the peg, which any respectable driver will be able to do, you can just turn in place and that'll fix any misalignment...

[NyCityKId]

My team is trying out mecanums for the first time this year... mostly because we thought the wheels looked really cool (joking). But really, I've seen a few threads on this forum about 6 wheels vs 4 wheels and I think the problem is that we need to define what maneuverability is once and for all for the purposes of FRC robots. If maneuverability includes strafing then obviously 4 wheel mecanum drive wins, however if u say maneuverability is the ability to have as much control over the robot as possible and get from one point to another as fast as possible and with control and you exclude strafing then the six wheel drive system would be more maneuverable (provided you have some method of preventing the front and/or rear wheels from skipping). All drive trains have they're pros and cons and it comes down to your knowledge of the different type of systems, how you plan to implement the system and your team's strategy for the game.

[PAR_WIG1350]

Maneuverability should be expressed as a quantity of degrees of freedom and the respective qualitative measurements for each. Each degree of freedom is either translative or rotational. Translative measurements should be rated based on acceleration and breaking, in terms of the length (distance) and/or time required to get up to maximum speed from a dead stop, and to stop from maximum speed. Rotational axes should be rated based on angular velocity, and minimum turning radius.

Maximum translative speed is irrelevant to maneuverability (in my opinion) since maneuverability is about controllability, not speed. Acceleration, on the other hand, provides information about how much space and time is required to change directions, which is directly related to controllability. Angular velocity is important since a robot that turns too slow wouldn't be able to react quickly while one that turns too fast would be hard to control.

Even with these measurements, there are still so many factors that are unaccounted for. These really need a little more work.

[dtengineering]

Originally Posted by NyCityKId

My team is trying out mecanums for the first time this year... mostly because we thought the wheels looked really cool (joking).

No joke... that's why we did it. We thought it would offer benefits in "the last tube game" and it did offer some benefits, but at far too high a price.

Where it really paid off was in the experience the team got, and the amazing videos and machine that we were left with afterwards.

Four years later and the wheels are still really cool.

Jason

[firemaster193]

If you want manueverablity with good wieght ditributation i would recommend 6 wheels with either tank drive or skid steer

[MrForbes]

Driver practice has a lot to do with how "maneuverable" either drive platform really is. Getting something put together NOW and on carpet and connected to a working control system might turn out to be a reasonable priority.

Also...designing this year's chassis based on last year's game might not be the best thing to do. Last year was really weird, this year things are back to normal--the kit chassis is plenty strong for a flat playing field.