[Ri3D] BOOM DONE. We're not done...

[Ether]

Originally Posted by Joe Johnson

Also, the mecanum wheels were not my favorite choice. And I think I was right. They are scaring me. A number of the small wheels on the 6" mecanum wheels are pretty wobbly already and they don't seem to roll well. Have others had issues with the Vexpro mecanums? do tell...

Could you please update us on what you have found out about this?

[Joe Johnson]

Originally Posted by Ether

Could you please update us on what you have found out about this?

Working with the Vex folk to understand this. Reportedly, they sold a boatload of these last year with no complaints.

I've ordered AndyMark HD's as a backup in case. Backup #2 is to go with all omnis (like JVN's Blitzbuild robot but we have a CIM+MiniCIM per wheel -- shojuld be a screamer).

Dr. Joe

[marccenter]

Dr Joe,

I have tried a couple of times, within the past two hours, to download the Boom Done - MCAD.zip files without success (receive error message). Has anyone else at CD been successful?

Thanks again for a great design. For small resource teams, your design is now our prototype for potential improvement (but don't hold your breathe for too long).

Regards,

FRC3548 Coach Marc Center

[Joe Johnson]

Originally Posted by marccenter

Dr Joe,

I have tried a couple of times, within the past two hours, to download the Boom Done - MCAD.zip files without success (receive error message). Has anyone else at CD been successful?

Thanks again for a great design. For small resource teams, your design is now our prototype for potential improvement (but don't hold your breathe for too long).

Regards,

FRC3548 Coach Marc Center

Hard for me to test because we are all on the same system here. Has anyone else had the same problem?

This is what works for me:

1. Go here (there is some sort or error message here but ignore it)
2. File menu > Download.
3. BOOM DONE.

[magnets]

Originally Posted by Joe Johnson

Hard for me to test because we are all on the same system here. Has anyone else had the same problem?

This is what works for me:

1. Go here (there is some sort or error message here but ignore it)
2. File menu > Download.
3. BOOM DONE.

It works for me from this link. Thanks!

[otherguy]

Dr. Joe,

I've pieced together what I could from the videos, and it sounds like you have a sharp IR sensor on board for ball detection, as well as some kind of acoustic sensor for measuring robot distance to the wall.

I tried digging through the java code you guys posted, but all I saw for distance measurements was based off the camera code/target detection.
If I've overlooked something please feel free to point me to the correct Java Class and I'll re-review.

Would you be able to provide any additional information on the sensor(s) used for ranging. I'm interested in knowing what make/model part was used and any usage notes (e.g. under what conditions did the sensor perform well/poorly).

Thanks, and great work.

[Tom Line]

Originally Posted by Joe Johnson

Working with the Vex folk to understand this. Reportedly, they sold a boatload of these last year with no complaints.

I've ordered AndyMark HD's as a backup in case. Backup #2 is to go with all omnis (like JVN's Blitzbuild robot but we have a CIM+MiniCIM per wheel -- shojuld be a screamer).

Dr. Joe

Joe,

Our sister team from Richmond used Vexpro mechanums last year, and broke an extremely large number of rollers off. In the end they broke so many that they put duct-tape on the things and used them as normal wheels because they were out of spares.

Now, I didn't build their robot so I can't say for certain that they had everything set up right. So I can't necessarily state that they weren't the cause of their own problems.

Are you seeing a lot of fractures at the point where the rollers meet the main body of the wheel?

[annie1939]

We used the the 6" VEXpro mecanums. We did not have any problems through 2 regionals and Worlds. Then we did demos and the wheels started breaking. Once one goes, they all start going. Either the had been weakened or once the one roller went, the others had uneven forces and they would all start breaking. We finally changed the demo bot to 4 standard wheels because we would lose a roller halfway through. At demos, the kids were more likely to run on uneven ground and start the cascade of breakages.

I would think they would last through regionals on even ground, just make sure you have a set of replacement wheels(and design for easy wheel changes) and extra rollers.

[magnets]

Originally Posted by Ether

Could you please update us on what you have found out about this?

The team I'm with used these mecanums last year, and the rollers have a TON of play (more than a new wheel), but they seem to work, so no issue here after ~40 matches.

[Ether]

Originally Posted by magnets

the rollers have a TON of play

axial or radial? or both?

[Joe Johnson]

Originally Posted by geomapguy

What's the tooth count on the top drive sprocket??

Hope to publish more details this weekend.

In the mean time, we used a 2 stage reduction. 2:1 in green cord - search my threads for McMaster part number. 7.5:1 in chain. We made the 120 #25 sprocket -- watch this video

You can make your own too. It is not that hard.

Dr. Joe

[geomapguy]

Originally Posted by Joe Johnson

You can make your own too. It is not that hard.

Dr. Joe

We talked with our machining sponsor about possibly having a sprocket CNC'ed once we finalize our gearing design. (since there's not a large enough COTS sprocket that we can find) All depends on schedule of the CNC production line, G-code, and lead time. So a maybe haha

Thanks

[JohnFogarty]

What was your robot frame's W x L?
Did you go with a 23"x32" long frame or did you make it a bit wider?

What was the final height of your robot?

[Joe Johnson]

Originally Posted by JohnFogarty

What was your robot frame's W x L?
Did you go with a 23"x32" long frame or did you make it a bit wider?

What was the final height of your robot?

26" X 30"

Final height? Not sure, I'll check and get back. We are no where near the 60" limit except when we shoot we get to 58".

Dr. Joe

[Joe Johnson]

Originally Posted by geomapguy

We talked with our machining sponsor about possibly having a sprocket CNC'ed once we finalize our gearing design. (since there's not a large enough COTS sprocket that we can find) All depends on schedule of the CNC production line, G-code, and lead time. So a maybe haha

Thanks

Laser cut ABS is awesome. I suggest finding someone nearby with a Zing cutter. Just works.

See the attached zip package with a bunch of stuff in it.

The 120T #25 sprocket, plus the support, plus the assembly.

I gave you the native files in a student version of SolidWorks 2013/4 ( you can't open them in the non-student version nor in earlier versions of SW).

I have also provided STEP files of the parts and the assembly.

I have also included DXF files of the sprocket and the plate

Most cutters can work with either the DXF or the STEP file.

Note the thicknesses. Also when you make the sprocket you will have to use a file or sand paper to bevel the edges to let the chain sit tight.

I have also I have improved the part from my original, putting holes for easy alignment & clamping using #10 screws.Will I was at it I added the "standard FIRST bolt pattern" in the middle.

Good luck,

Dr. Joe.