Chief Delphi - Mecanum Drive

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Re: Mecanum Drive - Help

With a mecanum drivetrain is driving sideways (along the Y axis below), there are four force vectors (one from each wheel) directed at 45 degree angles:

The Y components of the force vectors make the robot move in the Y direction, and are each equal to sin(45)*F=0.707*F. The X components, which are also equal to .707*F, cancel each other out.

Therefore, the robot will have .707 the force driving its sideways movement as it will driving its forward movement.

Re: Mecanum Drive - Help

Quote:

Originally Posted by ahecht (Post 655293)

With a mecanum drivetrain is driving sideways (along the Y axis below), there are four force vectors (one from each wheel) directed at 45 degree angles:...

Now draw the diagram again for the situation where the drivetrain is moving forward. I think you'll find the resulting vectors will add up to something surprising.

Re: Mecanum Drive - Help

Quote:

Originally Posted by squirrel (Post 655280)

Let's see if I understand it.....going forward or backward (in the direction of the wheels), the rollers do not need to turn relative to the wheels. Going sideways (perpendicular to the direction of the wheels), the rollers always need to turn relative to the wheels.

The "lost motion" of the rollers turning when going sideways, indicates to me that this is a less efficient way to move, compared to going forward/backwards with the rollers just "going along for the ride".

Do I have it right? My old brain has trouble grasping new concepts, so I would not be surprised if I don't understand it all....but I do have a little mecanum wheel here to play with.

I think this wraps it up pretty well.

Re: Mecanum Drive - Help

Quote:

Originally Posted by Smoking_Gun (Post 655072)

Hi,
Our team wants to use Mecanum Drive this year!
We have a few questions to ask before we could buy this.
We would appreciate if a team that has used this drive system would contact us by email (dark_key@walla.com) or post thiers in here.

Thanks!
Tal Saiag #Neat-Team 1943

While I appreciate the "wait for kickoff" notices, I also note that overseas shipping will be involved. Even shipping to Canada takes extra time, extra money (both for shipping and brokerage fees) and has the potential for delays at the border. Rush orders really start to become expensive. It is easier to "wait for the kickoff" when you know the parts that you order will show up a couple of days after you place the order. Ordering in advance may well be a prudent decision for overseas teams, although it does entail the risk of having to build your strategy around your technology rather than around the game. You are in the best decision to balance that risk against the risk of shipping delays and expeses.

It is also possible that buying in advance makes sense if your currency is high vs. the US dollar. I wish I had paid our entry fees and bought a couple super shifters a month ago... the team would have saved about $1,000 compared to the cost of those items today.

As for a discussion of the technology, or hearing from teams that have used it, there are numerous threads that you can find by searching the forums. I have posted regarding our team's (positive) experience with mecanums (and the challenges we faced by choosing to use them) to this thread. Try searching for "mecanum", "meccanum", or "mechanum" as those are common mis-spellings of the word. There is also a great entry on mecanum in wikipedia with links to videos of forklifts and manlifts using the technology.

Jason

P.S. Some video of our robot and R&D is on line.

Re: Mecanum Drive - Help

One point to throw out there is that mecanum robots still have a really hard time against a defensive robot. Even with a driver who uses the side to side motion well its still very hard to avoid defense. Also you are not going to win any pushing battles. But so far I have only seen a few robots who are able to score well with a defensive bot on them.

Re: Mecanum Drive - Help

If you absolutely had to lock in your drivetrain right now during the preseason, I'd say do not go with mecanum. Do not even consider it. A game like 2006 where a mecanum could be pushed from scoring very simply would be terrible. Even more terrible would be a 2002/2003esque game.

Re: Mecanum Drive - Help

Just because someone has Mecanum wheels does not mean that they can't play defense or push. I am a part of team 357 who had the jester drive system. We had this drive train in 2006 and became a defending robot by pushing. Depending on how well they are designed, Mecanum wheels can also be extremely good at climbing inclines. In 2006 again we made it up the ramp easily, which was often better than the teams we were playing with/against.

Re: Mecanum Drive - Help

Thanks for all the help!:)

I feel I need to clarify a few things:
1. The Mecanum Drive is only one of three driving methods our team is testing before the kickoff. We will decide which one to use after deciding the strategy.
2. Note that overseas shipping will be involved (to Israel).

Nevertheless, all the things said will be taken into consideration when deciding this year's drive method.

Thanks again!:)
Tal Saiag #1943 "Neat-Team"