Swerve Drive vs Mecanum Wheel drive?

[efoote868]

Originally Posted by lopsided98

As a mecanum lover, it really annoys me when people automatically rule out mecanums when the really don't know what they are capable of. Our robots in 2010 (http://youtu.be/rdAKiuimaY4?t=58s) and 2012 (http://youtu.be/tdAncHeHOEQ?t=1m36s) had mecanums and they could traverse the bump and balance on the bridge.

Yep. Same with my old team, and we were very competitive those years.

[XaulZan11]

Originally Posted by efoote868

we were very competitive those years.

I'd agree with this 100%. But, at least in 2012, I think you were competitive because of your accurate shooter and probably not your drive train (I wonder if you would have been better on bridges with a traction drive). Like you mentioned earlier with the good teams that build swerve probably are the teams with good scoring mechanisms and good team organization. These teams will be competitive no matter what drive train they select. Drive train selection is even more important for the fringe competitive teams; teams who may or may not have consistent scoring mechanisms or who may or may not have ample time to practice. The competitive teams that will have consistent scoring mechanisms and gave their drivers enough practice will be competitive with a swerve, tank or mecanum drive.

[The Doctor]

My experience with mecanum is that it causes a serious power drain when strafing (going sideways). Our battery is usually at 11.5v when going forward (using 4 CIM motors & Toughboxes), but it drops to 8v when strafing.

[Ether]

Originally Posted by The Doctor

My experience with mecanum is that it causes a serious power drain when strafing (going sideways). Our battery is usually at 11.5v when going forward (using 4 CIM motors & Toughboxes), but it drops to 8v when strafing.

Too much friction in the rollers.

It can be quite tricky to obtain an acceptably small level of roller friction in the affordable COTS mecanum wheels used by most FRC teams.

[kk052]

this year was our first time of swerve, that said it saved our robot, it defenetly has its benifits, and if you where just given both drives on the feild without the need to make or program them, swerve will usually win over machanum. but there are businesses that sell machanum (get them from andymark), but there are none that sell full swerve drives, even though you could buy the lower end of the andymark crab drive, so it will come to desighn, if you biuld a good working swerve, it will beat mach, but if your swerve isn't well made, like how our encoders would slip on our's (locktite fixed that) it will not even move. i would recommend adding a third option of a dual drive/octanum, for a well made swerve will nearly always win a machanum.

[asid61]

The problem with mecanum IMO is that they are basically the end. Apart from octacanum drives, mecanums don't have many places to go to design-wise. I think they will remain the same for a long time.

Swerve and tank drives, on the other hand, have a room for improvement. 221's Revolution Swerve weighs only a couple pounds per wheel, and their in-wheel Wild Swerve is fantastic. However, I still think that there is room for improvement- nobody's just found it yet.
Tank drives have changed little over the past few years, but gearboxes get more interesting every year.

[Alan Anderson]

Originally Posted by asid61

The problem with mecanum IMO is that they are basically the end. Apart from octacanum drives, mecanums don't have many places to go to design-wise. I think they will remain the same for a long time.

I can think of several directions for improvement of mecanum-style wheels. Figuring out a way for the rollers to never stick would be at the top of my list, followed by a simple roller lock to improve the maximum forward torque before losing traction, and eventually adding powered rollers to give better sideways power.

Optimizing mecanum material selection and mechanical design isn't done at all. Just increasing robustness while decreasing weight would go a long way toward making mecanum wheels better for FRC team use.

[asid61]

Originally Posted by Alan Anderson

I can think of several directions for improvement of mecanum-style wheels. Figuring out a way for the rollers to never stick would be at the top of my list, followed by a simple roller lock to improve the maximum forward torque before losing traction, and eventually adding powered rollers to give better sideways power.

Optimizing mecanum material selection and mechanical design isn't done at all. Just increasing robustness while decreasing weight would go a long way toward making mecanum wheels better for FRC team use.

It's been a while, but I'll reply anyway...

While it's true that you can make improvements like these, they are more design solutions and optimizations rather than conceptual changes. A mecanum wheel, no matter how well deisgned, will still be just that: a mecanum wheel. Rollers tilted at 45* angles on a wheel. There can't be any kind of mecanum revolution unless somebody figures out how to lock the rollers without wasting weight.
This is not a bad thing, as optimization is a very good thing and makes good ideas better, but it does show inherent limitations in mecanums. Other kinds of drives can be done in many different ways by comparison.

[EDesbiens]

I think its all about the drivers... I never drove a robot on swerves but I know how mecanums feel... If you are able to drive correctly, you don't need power. You only need to know your robot and how to counter the other team.

It's all about strategy and logic, it's not material...

[kuraikou]

From what I have seen mechanum has 3 problems.

1: Almost every time I see a team with mechanum I see the having issues with being pushed around and playing bad defense because they can be easily moved.

2: Drifting, I guess drifting can be good sometimes but when you are drifting every time you do a turn at high speed then I can see it being a problem.

3: From what I have heard from people on my team, (maybe true maybe not) they cannot go as fast because their speed is limited.

the third problem may not exist, but I think it does because I trust my teammates.

[ekapalka]

Originally Posted by kuraikou

3: From what I have heard from people on my team, (maybe true maybe not) they cannot go as fast because their speed is limited.

the third problem may not exist, but I think it does because I trust my teammates.

The third one is both true and false :) The speed is equal to the speed of any other wheel of the same diameter when traveling forwards/reverse, but the speed when just strafing is only sqrt(2)/2 times the maximum forward speed (I believe... its definitely less than 1). Tank doesn't have this option in the first place, and swerve has 100% of its forward speed when traveling sideways.

[Ether]

Originally Posted by ekapalka

the speed when just strafing is only sqrt(2)/2 times the maximum forward speed

The theoretical strafing speed is the same as the forward/reverse speed. There is no sqrt(2) factor.

The reason most mecanums have noticeably slower strafing speed is due to roller friction, roller axial free play, and floor surface compliance.

[Jalerre]

I haven't used both but I say choose swerve over mecanum. Mecanums don't have as much power and most teams write them automatically and will be hesitant when choosing a team with mecanum drive train for an alliance. However, don't listen to those people who that say mecanums are horrible. We've used them before in the past and their not that bad. They are much easier much to build and program than swerve.

[JohnM]

This year is our first year using mecanum wheels, and I have to tell you, I love them. I'm not a big fan of trying to switch to swerve drive next year because we still have not mastered mecanum wheels.

John M

[Spencer Chinske]

Our team is currently going through a similar debate. We think a swerve drive is great but are unsure if we can get one working reliably over the summer. In the event that we can't, we will be trying an octacanum drive train. For those of you who don't know, with an octacanum drive train you can toggle between high grip wheels and mecanum wheels. Secret city wildbots (4265) built a fabulous octacanum chassis this year. I would possibly look up an octacanum drivetrain because you can get the pushing power of a standard drive with the maneuverability of an omnidirectional drivetrain like a swerve or mecanum. Secret city wildbots (4265) can be found on YouTube under "dragonfly reveal".