Drive Train/Gearbox

[nathanv]

Going into our teams second season, we had a few questions on what to use for our drive train and gearboxes.

1. What are the pros/cons of using the WCP VersaChassis over the kitbot?

2. Is it worth using all 6 of your CIM motors for your drive train because this is something we want to decide before the season but we probably can't buy both.

3. Is a shifter useful? Sharing past experiences would help.
-If so, dog style or ball shifter?
Thanks for your help!

[thatprogrammer]

1. MUCH easier to change wheels, and can be lighter. You can also adapt it to a hex chassis, giving you a really big bellypan while staying within 112". http://www.chiefdelphi.com/media/photos/40862?

2. Depending on what you want, this may be beneficial. We don't know if we'll be allowed to use 6 CIM's next year, and they can end up weighing a lot more than a 4 CIM drive train. The additional torque can be used for faster acceleration and better pushing, but those might not be big priorities next year. Team 254 used 6 CIM's so they could blast past the field, but that kind of speed requires lots of driver practice. Keep in mind that a 6 CIM system has some extra maintenance. (Cooling the main breaker, and limiting deceleration.

3. Shifters can be VERY useful depending on the situation. The ability to push as well drive pass the field quickly is very useful. The additional weight can be a turn off. Again, this depends on what you want to do with your bot. Keep in mind that a versa chassis will make it very easy to incorporate a shifter set up, but so will the KOP chassis.

[nathanv]

Originally Posted by thatprogrammer

1. MUCH easier to change wheels, and can be lighter. You can also adapt it to a hex chassis, giving you a really big bellypan while staying within 112". http://www.chiefdelphi.com/media/photos/40862?

2. Depending on what you want, this may be beneficial. We don't know if we'll be allowed to use 6 CIM's next year, and they can end up weighing a lot more than a 4 CIM drive train. The additional torque can be used for faster acceleration and better pushing, but those might not be big priorities next year. Team 254 used 6 CIM's so they could blast past the field, but that kind of speed requires lots of driver practice. Keep in mind that a 6 CIM system has some extra maintenance. (Cooling the main breaker, and limiting deceleration.

3. Shifters can be VERY useful depending on the situation. The ability to push as well drive pass the field quickly is very useful. The additional weight can be a turn off. Again, this depends on what you want to do with your bot. Keep in mind that a versa chassis will make it very easy to incorporate a shifter set up, but so will the KOP chassis.

Do you recommend a DOG shifter from WCP or a ball shifter from VEX?

Originally Posted by nathanv

Going into our teams second season, we had a few questions on what to use for our drive train and gearboxes.

1. What are the pros/cons of using the WCP VersaChassis over the kitbot?

2. Is it worth using all 6 of your CIM motors for your drive train because this is something we want to decide before the season but we probably can't buy both.

3. Is a shifter useful? Sharing past experiences would help.
-If so, dog style or ball shifter?
Thanks for your help!

1. Pros/cons of WCP VersaChassis and kitbot:

Pros of WCP VC:
-Simple
-Reliable
-Requires little to no resources to do well
-Serviceable
-Fully customizable
-Extremely competitive drivetrain even in its most basic form

Cons of WCP VC:
-Higher cost
-No set of instructions (the point is you make your own chassis, so it's not cookie-cutter like the kitbot)

Pros of kitbot (as of previous years - we don't know much about 2015 kitbot):
-Simple
-Reliable
-Comes in the kit with all pieces you need
-Cheap
-Comes with instructions (which for newer teams who still aren't masters of the engineering process is a godsend)

Cons of kitbot:
-A solid drivetrain, but takes some custom add-ons to make it extremely competitive (as of previous years, again this has no bearing on what the AM14U2 for 2015 will be like)
-Very few configurations

In the end, there is no "better" solution - it's what works best for your individual team. The WCP VersaChassis is better suited for teams who have the budget to make a more competitive drivetrain but cannot or do not want to allocate more resources to designing custom parts. The kitbot can be done well by anybody, but can be extremely limiting once a team tries to expand past the "average" drivetrain boundaries and make theirs better. My advice to you is to consider which fits your resources the best and which you can build the fastest. Driver practice is everything. While quality and performance wise your average WCP VC will be better than your average kitbot, a kitbot with driver practice beats a VersaChassis without driver practice, and that should be your number one priority (though a VersaChassis with driver practice beats both any day ).

2. Is it worth using all 6 CIMs in your drivetrain?

Once again there is no yes or no absolute answer. You need to do your own designing and testing to see for yourselves what you want through game analysis on kickoff day. That being said I have done extensive work in the theoretical and mathematical side of this field these past few months and have come to the conclusion that the team I am working with - who has a lot of resources and a lot of experience - probably will not be using 6 motors in our drivetrain in 2015 because we have found the advantages to be marginal, and the potential disadvantages to outweigh the positives. Take this with a grain of salt, as it is just the work I've done and I'm just some guy writing a forum post on the internet, but I figured I'd tell you my findings. I won't go into the details of how I determined it was not worth it for our team to use more than 4 drive motors for the sake of keeping on task, but if you'd like to know pm me and I will be more than happy to explain my reasoning behind it. A note: If money is a concern you really need to either start fundraising your asse(t)s off right now or understand that your budget will be driving a lot of your decisions this coming season. Money talks, and if it's an issue it's in your team's best interests to listen to your budget.

3) Is a shifter useful?

A shifter is extremely useful, and for any team in almost any game I would argue having the ability to shift should be high on the priority list, solely for the reason of being chosen to play defense in low gear during eliminations. The speeds and the spreads you choose are also important, but since you did not ask about them I will not go into too much detail (again private message me and I'm always happy to share knowledge of these things). Between DOG shifting and Ball shifting, there is not one that is "better" than the other. It all depends on your preferences. Ball shifting is gaining popularity because it's a bit thinner than a DOG shifter and the VEXPro Ballshifter is a bit less expensive than the WCP DOG shifters. DOG shifters on the other hand have been used for years the most because they're the most reliable (there have been issues in previous years with Ballshifters falling apart). Personally I prefer DOG shifters, but in the end the type of shifting transmission isn't as important as it is that you have the ability to shift.

I hope these answer your questions. Like I said earlier please do not hesitate to contact me via pm if you have any more questions about drivetrains. I have focused my FRC study on drivetrains and mobility systems for the past 4.5 years now, and while I'm definitely not an expert I do have a small bit of knowledge I've accumulated over the years that I'm always happy to share.

[EricH]

If it was up to me... I'd simply take the Kitbot, swap the stock gearbox for a shifting one, ratio TBD after Kickoff (and, as well, type and supplier TBD after Kickoff--don't forget AndyMark in there!), and spend the rest of the 6 weeks working on the gamepiece manipulation system that goes on top, or getting driver practice, or programming, or all three. You could even play around with the kit gearboxes prior to getting the package with the new ones and spend about a meeting or two swapping the new ones in later.

My reasoning is that I don't put all that much stock in 6-CIM drivetrains. Sure, they've got more available power, but as noted above me, they've got some drawbacks, and more to the point, in most years they aren't exactly required. Using only 4 CIMs also gives two for use elsewhere, where I might need a lot of power that I can rely on.

[Lil' Lavery]

For a second year team, or really a very large contingent of teams, I would argue against a shifting drivetrain. It's awesome in theory, but in practice, most teams don't really utilize them well or frequently, and their resources could be better spent elsewhere. Considering the OP has already alluded to budget concerns, shifters are an expensive commitment, and the team would likely get a lot more utility investing that money and effort elsewhere.

[safiq10]

Originally Posted by Andrew Lawrence

1. Pros/cons of WCP VersaChassis and kitbot:

-No set of instructions (the point is you make your own chassis, so it's not cookie-cutter like the kitbot)

Well I wouldn't say that their are no instruction available. Their is just very few, Our team is planning on building a WCD and we plan on using this walk-through for our first time making it. I would recommend reading this if you plan on building a WCD.

Originally Posted by safiq10

Well I wouldn't say that their are no instruction available. Their is just very few, Our team is planning on building a WCD and we plan on using this walk-through for our first time making it. I would recommend reading this if you plan on building a WCD.

The point was that there is no finite way to make it. You make your own dimensions, you choose how many wheels you want and what kind, you choose your own transmission and how you want it set up, etc. There is no set way of doing things. It's so versatile.

[safiq10]

Originally Posted by Andrew Lawrence

The point was that there is no finite way to make it. You make your own dimensions, you choose how many wheels you want and what kind, you choose your own transmission and how you want it set up, etc. There is no set way of doing things. It's so versatile.

Alright I see what you were saying. I wish I would have understood it the FIRST time, so I wouldn't be making a fool of myself. All jokes aside WCD is very versatile and if you have the resources and the time during the offseason I would recommend building a test bot with it for practice.