[EWCP]-11-27-11 Drivetrain Design

[Akash Rastogi]

The next EWCPCast will be about how FRC drivetrains have evolved over the years, including the change after the inception of AndyMark and the kit chassis. We will discuss decision making for drivetrains as well as the evolution of drivetrains in FIRST.

We have arranged for Aren Hill (1625 alum, 3928 mentor), Ranjit Chahal AKA R.C. (1323), Adam Heard (973) to join us for this cast. We are still waiting on a few others to confirm their availability.

Our very special guest will be the man, the myth, the legend who invented swerve/crab drive in FRC, Dr. Joe Johnson (former 47 mentor, 3958 mentor).

Once again we are asking for your input, what should we ask our panel of distinguished guests?

The cast will be the usual time on Sunday November 27th (9pm EST) at the usual place. Hope to see you there. We will post links and other documents as we develop them with the panel of guests and as you all post your questions here.

Please present questions in a coded or bullet list.

And, as always, if you have an idea for a cast or would like to help us in any way please contact us here via PM, at our Facebook page.

[rsisk]

• It would be nice to know what a typical strategy design session was like pre AM days, how much strategy went into the drivetrain
• Also would be nice to hear Dr. Joe's thoughts about how he would have designed for 09 Lunacy

[jwfoss]

I'd like to hear some discussion of the following:

• Materials selection for chassis construction
• Choosing the "right" wheels (size and type)
• COTS vs. Custom (chassis, transmissions, wheels)
• Single speed vs. Multi-speed Drivetrains
• Gearing limitations (speed, power consumption)
• Building within your means
• Knowing your "customers"
• Innovations and new ideas

and, if possible...

• An intelligent debate on the omnidirectional/mecanum vs. traction based drives

[thefro526]

Originally Posted by jwfoss

and, if possible...

• An intelligent debate on the omnidirectional/mecanum vs. traction based drives

I will ensure that we spend about 15 minutes or so discussing this topic.

(sweet, 2000th post)

[Taylor]

Originally Posted by thefro526

I will ensure that we spend about 15 minutes or so discussing this topic.

(sweet, 2000th post)

Good, because I'm curious what Picone thinks of mecanum. He's such a shy fella. (congrats on 2K)

If he's available, I think it would be cool if Ether joined in this cast.

I'd also like to hear how teams determine a suitable weight for their drivetrain - if it's a hard number (i.e. no more than 60 lbs no matter what) or a percentage of their overall estimated design weight.

[Andrew Schreiber]

Originally Posted by Taylor

Good, because I'm curious what Picone thinks of mecanum. He's such a shy fella. (congrats on 2K)

If he's available, I think it would be cool if Ether joined in this cast.

I'd also like to hear how teams determine a suitable weight for their drivetrain - if it's a hard number (i.e. no more than 60 lbs no matter what) or a percentage of their overall estimated design weight.

We are concerned about the number of panelists in this cast. We are constrained by time because we have found that longer casts general dissuade people from listening because not all of it is relevant to their interests.


I will work on a solution so that we can talk about the pros and cons of every drive system in some form or another. One idea is to prerecorded discussions about the major systems (6+ wheel skid steer, crab, H, kiwi, mecanum, hybrids) with experts and posting them as EWCPShorts or something. If you have any ideas feel free to PM me.

[JohnSchneider]

How can you do a drivetrain presentation without JVN of 148? I mean 148 won worlds with a non-skid drivetrain, which in itself is impressive if you look at history - but on top of that they invented 9 wheel drive and helped spearhead the new articulating drive method. 148 and JVN work with IFI who designed and makes the most popular traction wheels available. I'm not trying to put them on a pedestal, but I feel like having them in the discussion would be beneficial.

[Andrew Schreiber]

JVN, don't take this the wrong way, just listing some of the giants whose shoulders we all stand on now. If you'd be interested in joining us for a cast post Kickoff (we are pretty well booked through then) let one of us know and we would love to put something together.

Originally Posted by animenerdjohn

How can you do a drivetrain presentation without JVN of 148? I mean 148 won worlds with a non-skid drivetrain, which in itself is impressive if you look at history - but on top of that they invented 9 wheel drive and helped spearhead the new articulating drive method. 148 and JVN work with IFI who designed and makes the most popular traction wheels available. I'm not trying to put them on a pedestal, but I feel like having them in the discussion would be beneficial.

148 was not the first team to win with a non-skid drivetrain. 111 won in 2003 with a crab drive and StangPS. 67 won in 2005 with a 3 wheel flopping swerve which was all sorts of crazy. And as far as talking about swerve style drives, we have the father of swerve, Dr Joe Johnson who was with 47 when they pioneered steered wheel systems back in the late 90's.

Articulating drives predated JVN, in fact, they were often used for shifting before the dog-gear style shifters appeared. In fact I seem to recall the predecessors to octanum and the ilk showing up on CD in 2006/2007.

Plus, John has spoken about FRC drive systems in the past, he's pretty open about it. We are trying to bring in people who don't usually talk to most teams and encourage them to share their knowledge. (Oh, and Andy Baker but we couldn't pass up him since he is sort of a personal hero to all of us)

While I do agree that JVN is an incredible engineer, I am really proud of the group we've put together for this cast and I think they will provide fresh content to the community. I hope he and the other experts don't take this as a snub that we aren't inviting them to join, we just have a limit to the number of people we can bring in at any one time.

YAY! Drivetrains! My favorite subject!

Some interesting topics to be spoken about:

-Wheel size, including the advantages/disadvantages of each size, and the best use for each sized wheel.
-Andymark's new Pneumatic tires, the possible applications for that, and what kinds of drives could use it.
-Mecanum vs. Swerve vs. 6WD
-4 wheeled swerve vs. 6 wheeled swerve
-Gearboxes, Which is best for which job, and the new worm gearbox
-Time spent on drive train in beginning of build season, how much time should teams spend on their drive train to get it moving, etc.
-Brake vs. Coast vs. 1 motor break and 1 motor coast
-Cantilevered vs. not
-The standard kitbot vs. The Kitbot on Steroids vs. "other" drives
-Drives that can switch between traction and mecanum wheels

And many more things that I don't have the time to write down.

Can't wait for this cast!

[thefro526]

After Discussion between Andrew and I, we've come up with what we think is the best way to approach this cast.

~15 Minutes talking with Dr. Joe about the History of FRC Drives.
~15 Minutes talking with Aren Hill, Dr. Joe and Adam about Swerve Drives (Arguably the most advanced drive in FRC)
~15 Minutes talking with those on the call about 'standard' FRC drives - Dropped Center 6WD's and 8WD's.
~15 Minutes talking about the advantages of an omni-directional drive vs a standard skid steer and the inverse.

The Rest of the time will be spent discussing good practices for FRC Drive Design. What wheels to use where & when, what speed to gear for, appropriate offset, wheel size vs. obstacles, proper material utilization etc. (Many of the questions asked in this thread should be answered here).

From there, Andrew and I will be doing 15 minute mini-casts with a few different guests as we find them to go more in depth on various drive types - if there is interest in these mini-casts. (Drive types being Mecanum, Killough, Kiwi, Octocanum, 4WD, etc.)

Thoughts?

[MattC9]

Could some one please go in depth on chain tesioning? And different methods to do so? PLEASE

[XaulZan11]

Originally Posted by thefro526

~15 Minutes talking about the advantages of an omni-directional drive vs a standard skid steer and the inverse.

Good luck editing the hours of video of mecanum driving circles around traction drive to just 15 minutes!

I like the idea of having a main show and then mini-shows more more indepth on spefic drivetrains for those interested.

[Andy Baker]

Many of us have learned tons from Dr. Joe over the years, and it is very exciting to see him back as an FRC mentor. Having him on this cast as a guest is outstanding. I would like to hear his answers to these things:

1. What was the design process for (arguably) the best FRC robot ever, ChiefDelphi's 2000 robot?
2. Why did ChiefDelphi choose to design (arguably) the most complex, convoluted drive train in 2001?

I'll have my popcorn ready, listening for "what to do" and "what not to do".

Andy B.

[sdcantrell56]

Originally Posted by animenerdjohn

How can you do a drivetrain presentation without JVN of 148? I mean 148 won worlds with a non-skid drivetrain, which in itself is impressive if you look at history - but on top of that they invented 9 wheel drive and helped spearhead the new articulating drive method. 148 and JVN work with IFI who designed and makes the most popular traction wheels available. I'm not trying to put them on a pedestal, but I feel like having them in the discussion would be beneficial.

I wish I could find a facepalm picture real quick but unfortunately can't. I don't even know where to begin to start with responding to this though...yikes!

[ttldomination]

Originally Posted by sdcantrell56

I wish I could find a facepalm picture real quick but unfortunately can't. I don't even know where to begin to start with responding to this though...yikes!

Got you covered bud.



- Sunny G.