Custom West-Coast Design Feedback

[daliberator]

Originally Posted by BrendanB

I apologize for the double post.

That's a very unique design you have their but unique designs are good! Exploring something new is a fun experience.

Before you settle on one style of drivebase, would you care to explain how your team decided that building a WCD style base was the right ones for you? What type of advantages do you see in building one? What are your design criteria(s) such as lightest, simplest, ease to build, ease to swap out parts, space efficient, etc.

Our team listed out what we wanted to see in a drivebase separate from a certain type of base and in the end we came up with a very decent solution that was extremely easy for us to build based on our immediate resources, was highly reliable considering it hasn't broken since we assembled it and put it through 6 competitions, and highly competitive as it gave is a good high speed our driver could control coupled with nice traction wheels and low gear for pushing through defenders.

Thanks for the reply!
We're not quite done deciding, but we really liked how the west coast robots performed at the events we were at. We have fairly good machining resources, so it seemed like a logical step up from our KoP drive this year.

As for my design, after what I have seen in this thread, I have gone supports crazy. I grossly overestimated the amount of structural elements I need, as well as the fact that steel may be way overboard. I'm working on a new design that will feature aluminum. Are there any other changes you could reccomend?

Thanks,
daliberator

[BrendanB]

Originally Posted by daliberator

Thanks for the reply!
We're not quite done deciding, but we really liked how the west coast robots performed at the events we were at. We have fairly good machining resources, so it seemed like a logical step up from our KoP drive this year.

As for my design, after what I have seen in this thread, I have gone supports crazy. I grossly overestimated the amount of structural elements I need, as well as the fact that steel may be way overboard. I'm working on a new design that will feature aluminum. Are there any other changes you could reccomend?

Thanks,
daliberator

Yes, WCD style bases many times lend to perform better but this is typically from the components they are using such as wheels, motors, no. of motors, gearboxes, wheel type/tread, wheel layout 6wd vs. 8wd, driver skill, etc among many other little details. WCD does give you some advantages in how you package these items to be lighter, take up less space, and provide a more efficient setup.

I personally have never built a WCD base only designed a few in Inventor. Some of the reasons teams jump to do a WCD is because its easy to change out a wheel and if you use bearings blocks you have integrated chain spacing which were two features that stuck out to our team a lot after last year. In the end we opted over building a WCD to try new products/techniques while improving performance. For instance we used solid rubber Colson wheels for our drive wheels and found a C-C chain spacing calculator from team 1640 to calculate the space between each wheel to eliminate chain tensioners (we used #35 chain). These two decisions allowed us to never touch the base and accomplished our two main reasons for looking at a WCD which is why we haven't made one. Our base was really easy to make and it built off of what we were comfortable with.

Its just always good to discuss why you intend to build something compared to doing something that a majority of high performing teams do just because they do it. Yes their WCDs are very, very good drivebases but their drivers are what really make them shine and that goes for every team. WCDs aren't very popular up here in New England but we do have our share of extremely good base drivers that can compete with the best. Most notably, team 195 the Cyberknights driver destroys the playing field to be honest. He is very in tune with the match play and more importantly how his robot best moves on the field. He does all this with just a modified kitbot. They swapped the front wheels for omnis and upgraded the gearboxes to 3 CIM single speeds and he uses them to the full potential which is something a lot of teams overlook. I use 195 as one of the many examples we have up here but a little goes a long way.

If its performance you are looking for make some small mechanical tweaks but really give your driver that time to practice especially in the offseason. That is what makes good drivebases.

[highlander]

Originally Posted by BrendanB

Yes their WCDs are very, very good drivebases but their drivers are what really make them shine and that goes for every team. WCDs aren't very popular up here in New England but we do have our share of extremely good base drivers that can compete with the best.

If its performance you are looking for make some small mechanical tweaks but really give your driver that time to practice especially in the offseason. That is what makes good drivebases.

+1. A lot of people overlook the fact that the driver is at least 50% of how well you do at competition. A lot of the top teams spend years training their drivers before they even get to drive at competition. Make sure to chunk in time in your schedule to practice with your drive base.

[asid61]

Originally Posted by highlander

+1. A lot of people overlook the fact that the driver is at least 50% of how well you do at competition. A lot of the top teams spend years training their drivers before they even get to drive at competition. Make sure to chunk in time in your schedule to practice with your drive base.

Totally true. Driver practice is the bomb.

[highlander]

Originally Posted by daliberator

Hey CD!
I didn't know exactly how much to drop the center bearings, so I just guessed at 3/16ths of an inch.

daliberator

Having 1/8" of drop is pretty standard, +/- how much sponginess your tread will have. 3/16" should be ok for most drivetrains, although I don't know what tread you are using.

Originally Posted by highlander

Having 1/8" of drop is pretty standard, +/- how much sponginess your tread will have. 3/16" should be ok for most drivetrains, although I don't know what tread you are using.

A rule of thumb I've always followed is 1/8" for flat wheels (ie colsons, kit wheels, etc), and 5/32" or 3/16" for blue nitrile. The properties of the blue nitrile tread allow for even the slightest amount of contact to affect turning, and because they grip the carpet so well the increased drop is sometimes needed to ensure there is no contact.

[Boe]

Originally Posted by Andrew Lawrence

A rule of thumb I've always followed is 1/8" for flat wheels (ie colsons, kit wheels, etc), and 5/32" or 3/16" for blue nitrile. The properties of the blue nitrile tread allow for even the slightest amount of contact to affect turning, and because they grip the carpet so well the increased drop is sometimes needed to ensure there is no contact.

We ran 1/8 drop with blue nitrile in both 2013 (6 wheel WCD long base) and 2012 (10 wheel center 6 dropped wide base) and ran it with a 1/16 drop this year (wide base 6 wheel WCD) all wheels being between an inch and an inch and a quarter. We haven't experienced any turning problems, but one of the things we are hoping to look into this summer is playing around with the drop amount.

Originally Posted by Boe

We ran 1/8 drop with blue nitrile in both 2013 (6 wheel WCD long base) and 2012 (10 wheel center 6 dropped wide base) and ran it with a 1/16 drop this year (wide base 6 wheel WCD) all wheels being between an inch and an inch and a quarter. We haven't experienced any turning problems, but one of the things we are hoping to look into this summer is playing around with the drop amount.

I'm surprised you could get to 1/16 drop without experiencing drag. The diffierence between 5/32 drop and 1/8 becomes more apparent in 1.5" - 2" wide wheels, but it should still be a factor in 1" wheels. Could you provide more information (pictures or CAD models, maybe?) on your 2013 and 2014 drives?

[Chris is me]

Originally Posted by Andrew Lawrence

I'm surprised you could get to 1/16 drop without experiencing drag. The diffierence between 5/32 drop and 1/8 becomes more apparent in 1.5" - 2" wide wheels, but it should still be a factor in 1" wheels. Could you provide more information (pictures or CAD models, maybe?) on your 2013 and 2014 drives?

The new chassis size restrictions of the last 2 years have changed the dynamics of drop center drives a lot. The old rules of thumb kind of go out the window. As chassis tend to be squarer rather than longer, the need for drop is substantially less than in previous years. With the right wheels you can probably get away with 6WD no drop in a square configuration and still turn fine. Maybe you still need a bit of drop for wide roughtop, though.

We ran 1/8" drop this year on Colsons and that was probably too much. I'd rather have gone 1/16".

Originally Posted by Chris is me

We ran 1/8" drop this year on Colsons and that was probably too much. I'd rather have gone 1/16".

Did you cut tread into your colsons?

[Chris is me]

Originally Posted by Andrew Lawrence

Did you cut tread into your colsons?

We left them untreaded for one event and cut treads in them for our second event. Turned great both times but was a bit rockier than I wanted. Perhaps that's just the tradeoff one has to make.

Back in 2011, 1/8" was just right for a long base with Colsons.

Originally Posted by Chris is me

We left them untreaded for one event and cut treads in them for our second event. Turned great both times but was a bit rockier than I wanted. Perhaps that's just the tradeoff one has to make.

Back in 2011, 1/8" was just right for a long base with Colsons.

For clarification - was it rocky both times because of the drop, or was it rocky after you cut the treads? Also, did the treads affect the smoothness of the wheel's ride (did driving feel more bumpy)?

[Boe]

Originally Posted by Andrew Lawrence

I'm surprised you could get to 1/16 drop without experiencing drag. The diffierence between 5/32 drop and 1/8 becomes more apparent in 1.5" - 2" wide wheels, but it should still be a factor in 1" wheels. Could you provide more information (pictures or CAD models, maybe?) on your 2013 and 2014 drives?

I dont have easy access to all the CAD right now but here's some more information on the two drives.

2013:
6 wheel WCD with two speed 4 CIM custom shifters geared for 9/19 fps before frictional losses. The wheels were 6inch custom 3d printed and if memory serves they were 1 inch wide. The robot frame was 30"x24", dont rember wheel spacing exactly but it was ~11 inches give or take. Here's a CAD render of it.

2014:
6 wheel WCD with two 3 CIM Ballshifters geared to 6/16 fps before losses. The wheels were the 4 inch AM performance wheels and the frame was 23.5"x32" with about 8" between wheels. We almost went with no drop on this but decided to go with a very slight drop to be safe. Wheel also almost made it a four wheel WCD but decided against it. Here's a render of the robot.

Originally Posted by Boe

I dont have easy access to all the CAD right now but here's some more information on the two drives.

2013:
6 wheel WCD with two speed 4 CIM custom shifters geared for 9/19 fps before frictional losses. The wheels were 6inch custom 3d printed and if memory serves they were 1 inch wide. The robot frame was 30"x24", dont rember wheel spacing exactly but it was ~11 inches give or take. Here's a CAD render of it.

2014:
6 wheel WCD with two 3 CIM Ballshifters geared to 6/16 fps before losses. The wheels were the 4 inch AM performance wheels and the frame was 23.5"x32" with about 8" between wheels. We almost went with no drop on this but decided to go with a very slight drop to be safe. Wheel also almost made it a four wheel WCD but decided against it. Here's a render of the robot.

Very interesting. And very beautiful robots as well - thank you got sharing. As Chris said above, with the new frame perimeter, it appears less drop can be run with these wheels than before.

[RKazmer]

2363 over the past year used a 1/4" holed lexan (the holes were put there in the manufacturing). It was easier for the team to use that for wiring and with weight. In 2013, we used garalite, but found it too fragile and would shatter easily.