Mecanum wear and dirt resistance

[Ether]

Originally Posted by Hawiian Cadder

They were the newer 8 inch mechanisms with the Grey rollers.

I did a shadow-graph of that design several months ago, and there is a slightly bumpy transition (circumferencial gap) from one roller to the next. I wonder if a mec with a continuous transition would make any difference.

Originally Posted by Hawiian Cadder

The wheels were all free spinning

Long shot I know, but did you happen to measure the axial free-play of the rollers?

[Garret]

Our Mecanum Robot leaves massive skid marks when it drives sometimes. My main guess is that it is attempting to accelerate too fast and the wheels are slipping. I think part of this is due to the dusty shop floor (robot slips more easily) we drive on and the fact that our team tends to drive the mecanum robot pretty hard (accelerates too fast).

[blackflame2996]

Originally Posted by flameout

I am considering presenting the idea of switching our T-shirt launcher over to mecanum to Team 957. Before doing so, I would like to have a definite list of pros and cons (as we have never done mecanum before).

While there are many threads discussing mecanums in the context of competition, I have a few concerns specific to this robot that I have not found adequate information on.

Here are my primary concerns:

1) Wear. We will be running this bot a lot, often on asphalt and other abrasive surfaces. We'd rather not have to periodically replace wheels (even once a year would be too much), although, if necessary, we might be willing to switch out the rollers (if they can be made/obtained cheaply) every year or so.

2) Resistance to dirt. We do not always run the robot inside, and it is not uncommon to have it running right on dirt (or being pushed over the dirt). I'm afraid that the dirt may gum up the bearings.

3) They must not damage gym floors. We often run our robots on gym floors -- the kitbot wheels work fine for this, but other types damage the flooring. This is likely to be a smaller issue than the others (as mecanums don't typically skid very much), but it's still a consideration.
EDIT: Let's remove this from the topic of this conversation, as mentioned in post #3 -- we'll do our own testing to verify that a specific roller material does not damage the floors prior to ordering a set of wheels.

In terms of machining (for creating replacement rollers if it's necessary), our team isn't very capable. We have neither a lathe nor a mill, and have no experience with casting parts. However, we have a sponsor with a high level of machining capability who would be able to machine roller casts for us, as long as it is a one-time deal.

How valid are each of these concerns (particularly 1 & 2)? Do you have a recommendation for a particular style of mecanum (with respect to these concerns)?

Please don't discuss mecanum vs. tank-style drivetrains -- let's keep this thread centered on the practicality and implementation of mecanum on a robot with the usage scenarios outlined above.

Thank you.

The pro's would obviously be manuvarability. However, mecanum wheels are not great durability-wise, especiallily off of the field. Doing demos in the off-season with our mecanum-driven robot from breakaway tore them apart. they are more expensive, so keep in mind that they will not last very long on aspault.

[lcoreyl]

Originally Posted by flameout

I am considering presenting the idea of switching our T-shirt launcher over to mecanum to Team 957. Before doing so, I would like to have a definite list of pros and cons (as we have never done mecanum before).

While there are many threads discussing mecanums in the context of competition, I have a few concerns specific to this robot that I have not found adequate information on.

Here are my primary concerns:

1) Wear. We will be running this bot a lot, often on asphalt and other abrasive surfaces. We'd rather not have to periodically replace wheels (even once a year would be too much), although, if necessary, we might be willing to switch out the rollers (if they can be made/obtained cheaply) every year or so.

2) Resistance to dirt. We do not always run the robot inside, and it is not uncommon to have it running right on dirt (or being pushed over the dirt). I'm afraid that the dirt may gum up the bearings.

3) They must not damage gym floors. We often run our robots on gym floors -- the kitbot wheels work fine for this, but other types damage the flooring. This is likely to be a smaller issue than the others (as mecanums don't typically skid very much), but it's still a consideration.
EDIT: Let's remove this from the topic of this conversation, as mentioned in post #3 -- we'll do our own testing to verify that a specific roller material does not damage the floors prior to ordering a set of wheels.

In terms of machining (for creating replacement rollers if it's necessary), our team isn't very capable. We have neither a lathe nor a mill, and have no experience with casting parts. However, we have a sponsor with a high level of machining capability who would be able to machine roller casts for us, as long as it is a one-time deal.

How valid are each of these concerns (particularly 1 & 2)? Do you have a recommendation for a particular style of mecanum (with respect to these concerns)?

Please don't discuss mecanum vs. tank-style drivetrains -- let's keep this thread centered on the practicality and implementation of mecanum on a robot with the usage scenarios outlined above.

Thank you.

You are leaving out a MAJOR factor which IMO is VERY important: Mecanum wheels are SWEET!! In particular, if you are doing this at a place where many spectators have no idea what is happening, this will look like straight up MAGIC!!! Isn't the point of a T-shirt shooter to make more people aware of your robotics team? If so, why not make them AMAZED at how you can drive STRAIGHT SIDEWAYS!!! I'm serious. non-robotics people are ALWAYS amazed by this... As far as the mecanum vs. 6WD debate, I wonder how the debate would go if the only question was "which looks more awesome??"