8 MINI-CIM SWERVE

[AdamHeard]

Originally Posted by Electronica1

But that would not allow you to have similar power to a 6 cim tank drive, which is the point of the 8 mini-cim argument right? (I might be missing something) You could have more than 4 modules in order to match the 6 cim power I guess.

You could do a swerve using those fancy mercury free mechanical slip rings and put the motors where they belong (external to the module), and easily do 2 per wheel.

[Max Boord]

Originally Posted by Electronica1

How would you fit two motors inside a wheel?

6 inch wheels. Baxter Bomb Squad already uses them and it would give you 1/2 inch of clearance on ether side. How the gearing would work is a totally different story.

Originally Posted by AdamHeard

You could do a swerve using those fancy mercury free mechanical slip rings and put the motors where they belong (external to the module), and easily do 2 per wheel.

But THIS

[EricH]

Originally Posted by Max Boord

But THIS

But this nuttin'. Try one of THESE! (Just swap the FPs for more CIMs.)

It's not about more/less points of contact with the ground, or about how much power you can put into the drivetrain, or how much traction a given wheel has. It's the balance of all of the above. I don't think that adding two more motors will do all that much--just make ya more likely to be traction-limited instead of torque-limited.

[Tyler2517]

Originally Posted by EricH

But this nuttin'. Try one of THESE! (Just swap the FPs for more CIMs.)

It's not about more/less points of contact with the ground, or about how much power you can put into the drivetrain, or how much traction a given wheel has. It's the balance of all of the above. I don't think that adding two more motors will do all that much--just make ya more likely to be traction-limited instead of torque-limited.

Look at what happen with the change from 4 cim drives to 6 cim drives. They are classes of there own.

[Max Boord]

Originally Posted by EricH

But this nuttin'. Try one of THESE!

Upgraded.

[JesseK]

2 extra motor controllers, 2 fewer available 40A ports on the PDB - 8 Mini CIMs vs 6 CIMs is a lose IMO.

[nuclearnerd]

Originally Posted by JesseK

2 extra motor controllers, 2 fewer available 40A ports on the PDB - 8 Mini CIMs vs 6 CIMs is a lose IMO.

For me too, but If another team decides they would rather have all 40A circuits going to the drive, and only use lower power circuits for the rest of the bot, why should the rules keep them from making that trade-off on their own?

[JesseK]

Originally Posted by nuclearnerd

For me too, but If another team decides they would rather have all 40A circuits going to the drive, and only use lower power circuits for the rest of the bot, why should the rules keep them from making that trade-off on their own?

Drive trains are easy to build. Without understanding the fundamentals, drive trains are very hard to perfect as part of a greater robot with other mechanisms. I feel that increasing the amount of power through to the drive trains is a cop-out low & mid-tier teams who don't bother to try to perfect their drive train. I'd much rather the GDC limit total electric power through the drive train if there were any rule changes in that respect. It would force the trade-offs to be actual engineering decisions rather than "BIGGER IS BETTER RAWR!1".

On top of that, I feel that anyone who mentions 6 CIMs as what led to success in an anecdote should have a gigantic caveat stickied across their post. I don't know about the exact wording, but perhaps it could say something like

Dear FRC participant, 6 CIM drive trains (or 8 MiniCIMs) may lead to some nice zippy acceleration if you "like to go fast". Yet here are some side effects you should consult your robot engineers about:

• Your drivers keep getting penalties for high-speed ramming
• Your robot "passes out" for about 30 seconds after getting into a pushing match
• Your batteries from last year's competition no longer hold a charge for the entire match
• Your other motor-driven subsystems are noticeably slower towards the end of a match
• The tread constantly strips off of your wheels when merely grazing another robot
• Your aluminum output shaft shears
• The chains snap apart at the master link or eat the teeth off of the sprockets after a quick reverse

These were witnessed, BTW.

Full disclosure, 1885 took a beating by powerful drivetrains at champs this past year. Getting double-teamed as a single-speed 11ft/s drive train got very aggravating very quickly. We endured, had some great matches and I know what to do for next year. We even had our very first actual zero-maintenance and very agile drive train this year across 4 competitions. Hopefully I've presented this in such as way that shows more thought has gone into it based upon several years of drive train design experience, rather than a single competition's worth of bias.

[Oblarg]

Originally Posted by JesseK

On top of that, I feel that anyone who mentions 6 CIMs as what led to success in an anecdote should have a gigantic caveat stickied across their post.

4464 used a 6-CIM drive last year, and I'd be the first to add caveats when we talk about the success it brought us (I've detailed the problems we encountered several times on these boards), but it is important to recognize that every single problem you've mentioned is something that can be either mitigated or avoided completely with proper diligence.

Yes, a young, inexperienced team naively going "MORE IS BETTER!" and mindlessly adding motors to their drive can easily do more harm than good, and designing a 6 CIM drive in a way that doesn't run into the mentioned problems is nontrivial (we had to swap our gearing before champs last year, and it wasn't because we hadn't put a lot thought into the gearing we originally had), but I don't think that every 6 CIM success story is necessarily ignoring or downplaying the negatives, or overstating the positives.

[SoftwareBug2.0]

Originally Posted by Nuttyman54

Lastly, it is possible to get 6 CIM power with swerve-style drive, but you can't do it with a module swerve. Concentric swerves that distribut power from two (or even one) gearbox to multiple swerve wheels but are steered independently is a way to do it.

There are no limits on the number of swerve modules allowed. How about six?

[EricH]

Originally Posted by SoftwareBug2.0

There are no limits on the number of swerve modules allowed. How about six?

Winnovation already did that one. As I recall... they had a remarkable run that year, and then decided afterwards that they just might have made a mistake. (This was coming from a team that made it to Einstein with a 6-wheel swerve, if memory serves.)

The mistake in question, as I recall, was something to the effect of "Ya know, we didn't REALLY need a 6-wheel swerve for this game."

[Chadfrom308]

It would be hard and heavy to make us a 4 CIM, 8 Mini-CIM mechanum drivetrain. But, not impossible.


We will just keep adding motors to our drivetrain until we blow a breaker just by accelerating

[EricH]

This little challenge has been posed before, but I think it's worth posing again.


Use every motor allowed (or as many as needed) in ONE gearbox. This gearbox could then shunt power to any use on the robot--drivetrain, shooter, arm, intake, whatever--via gears and belts. Imagine having 6 CIMs, a bunch of 775s and/or 550s, the full complement of BAGs, and some PG71s all powering drivetrain... or arm... or whatever...


This is, after all, the sort of thing used to power machine shops in the way olden times: one power source, every tool has a belt off of that source and a clutch to disengage itself...

[RyanShoff]

http://gallery.marswars.org/2014-bui...G_3784.JPG.php

Our swerve was originally setup for 1 cim and 1 mini-cim per module. Ultimately we ended up cutting off the extra spot. Mostly because we wanted to use slip rings and not worry about ripping up wires.

[asid61]

8 mini-cim swerves would be pretty cool, but thinking about it, what advantage does more mini-cims allow?
A swerve drive that is compatible with 2 mini-cims is probably compatible with a cim and a mini-cim, because the mounting and speeds are similar.
So I don't think adding more mini-cims would be useful.