4 wheels v. 6 Wheels
 

My team has done 6 wheels the past 4 years of the frc season. Last year we used 4 6'' treaded metal wheels with 2 6'' dual omni wheels. This year we are debating to only use 4 6'' treaded wheels instead of 6. We need more opinions on what are the benefits of each one are. Teams that have experience in both would help. Thanks!

Re: 4 wheels v. 6 Wheels
 

Portabella or Vidalia?

Re: 4 wheels v. 6 Wheels
 

Spelling mistakes aside, a little more information would be helpful.

I assume your robot was set up something like:
t------t
|........|
o------o where t is a traction wheel and o is an omni?
|........|
t------t


What was the wheel setup?

Is that 4 6" wheels with tread instead of 6 identical wheels or instead of the 4 tread/ 2 omni configuration you had last year?

Re: 4 wheels v. 6 Wheels
 

I'm presuming that your setup last year looked like this:

T - T - O
|--------|
T - T - O

If you'd dropped the center wheel sufficiently, the omniwheel did nothing for you. If you didn't drop the center wheel, the omniwheel made it possible for your robot to turn.

If you were to instead build a drive that looked like this:

T - - - T
|-------|
T - - - T

...you'll likely find that you're unable to turn effectively.

You should not make decisions based upon opinion. You should strive to understand the science that led to the prevalence of 6WD robots in FRC and extrapolate the answers to your questions from that.

In your case -- the important factors to consider are the wheelbase, the available torque at the wheels and the coefficient of friction between your wheels and the carpet. With that information, you can calculate whether or not the drive you're contemplating will work.

Re: 4 wheels v. 6 Wheels
 

As far as number of wheels, 6 has been a very reliable number for many teams. The difference is that 6 allows the robot to turn a lot easier than 4. Just remember to add a .125" to .187" drop on the center wheel so that only 4 wheels are on the ground at once.

Many teams have also run 8 wheels, with the center 4 wheels dropped. In both scenarios all the wheels are traction.

Re: 4 wheels v. 6 Wheels
 

Why did you assume that?

Re: 4 wheels v. 6 Wheels
 

I'm a bit of a newbie to all this, but from what I have observed (and correct me if I'm wrong) six wheels might be the best option for this year's game. The setup provides better mobility and possibly more speed than the traditional four-wheel setup. It would also be more stable and harder to tip over. But if you're still unsure, you should try to test each setup in small scale if possible.

Re: 4 wheels v. 6 Wheels
 

I have no idea why that made sense to me in my head. Changed my first post to just ask what the setup was.

Re: 4 wheels v. 6 Wheels
 

Are you driving in a wide configuration or a narrow configuration? The wheel base distance bakes a huge difference in whether you can turn well with four wheels.

Re: 4 wheels v. 6 Wheels
 

We are switching from 6 identical wheels, which is what we used last year, to 4 6" wheels with tread.

Re: 4 wheels v. 6 Wheels
 

Sorry for me putting opinion, but yes our team makes every decision based off how it will benefit us and what we are trying to achieve. We always go for making a robot that can push other robots out of the way if we need.

And also we are used to build 6 WD robots, and that's what we know how to do pretty well for the most part.

Re: 4 wheels v. 6 Wheels
 

When we had all 6 wheels treaded and we did lower the center an 8th. So make the robot only on 4 wheels at one time.

Re: 4 wheels v. 6 Wheels
 

Haha funny. If anything Portabella.

Re: 4 wheels v. 6 Wheels
 

Do this then. The less time you spend on a drivetrain, the more time you spend on manipulators.

Re: 4 wheels v. 6 Wheels
 

My team has had a love affair with 4 wheels since 2012. This year is no different, and this year all 4 are direct-drive. It's so simple: no chain/belts to haggle with, high quantities of hubs to worry about or extra axles to lathe.

The wheel base (width x length) is ~28"x17". The robot would normally be 'tippy', but we have a plan for c.g. and we're going to have ~1/4" ground clearance overall for the frame. This means that the outer edges of the frame will prevent us from going all the way over in the event of a hard stop. Sure, we could put another 2 wheels in to do that for us - but why?

Re: 4 wheels v. 6 Wheels
 

We stick with treaded 6 wheel drive drop center, all year every year unless if the game involves something where a 6 wheel drop center would cause us to be at a disadvantage, which is not often.

We try to go for the same drive system every year so we don't waste any of our build season contemplating other designs, when we know that we have a drive system that is reliable and low maintenance. Saves us time for prototyping if the drive base is built before build season, too. Then we just build another identical one for our final bot. It's just easier that way. Boom done.

During the off season, we do want to try some swerve prototyping.

Re: 4 wheels v. 6 Wheels
 

6 wheels means a small turning radius if you have a drop center... I think that 6 wheels is the way to go if your doing tank unless you have a very specific reason not to. Last year our team did 6 wheels and was able to turn on a dime. Its also a lot of fun to play with :)

Re: 4 wheels v. 6 Wheels
 

Mushroom OR Onion? I prefer AND.

http://www.tasteofhome.com/recipes/p...oom-onion-soup

not often that I get to poke at Ether.....

Re: 4 wheels v. 6 Wheels
 

This is a popular design choice for robots. Last year for the 2013 game, Team 935 had a wheel drop. I want to say the final drop height was less than 1/8" (I'll check when I go over today and subsequently edit this post).

I remember a lot of problems when our robot came to a sudden stop while testing with a 1/8" drop. It would rock to rest on the two front or back wheels, depending on which direction the robot was going when it stopped. This would cause the Frisbee launch angle to lower -- or rise -- causing us to incorporate an angle of launch error to our shooting calculations. Just something you should pay attention to. Not having a drop on a six wheel is counterproductive to its design intent however. Again, I'll update when I run in today.

Re: 4 wheels v. 6 Wheels
 

1/4" ground clearance may be too low. There are often cables or other small bumps in the field that are not in the drawings. This year there are not any obvious field parts that would need power, but you never know. What about field debris?