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

[Joe Johnson]

Originally Posted by geomapguy

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

Ratio is not fully optimized imho, but this is what we have now on each wheel:
CIM + Mini-CIM
CIMpleBox: 12:56
#35 Chain: 12:24
6" Vexpro Mecanum

Some notes:
The JVN spreadsheet (Very useful) puts the top at 12 to 15 ft per second (going forward, not crabbing).

In practice, I think we are a bit slower than I'd like to be if we are going to be a fast nimble robot rather than a pushing robot. So, I would am probably going to push for a lower ratio (more speed) by going to a 16T sprocket rather than the 12T.

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...


Dr. Joe.

[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

[Calvin Hartley]

Originally Posted by Joe Johnson

lso, 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...

We used them for part of our season last year. We really liked them, and they held up to use well. However, part way through the summer during demos and whatnot, the rollers started to break off. They worked great for us through the season, but many rollers broke within a short time once they did start breaking.

Hope this helps, I know it's not very specific nor detailed information...

[Joe Johnson]

Originally Posted by Calvin Hartley

We used them for part of our season last year. We really liked them, and they held up to use well. However, part way through the summer during demos and whatnot, the rollers started to break off. They worked great for us through the season, but many rollers broke within a short time once they did start breaking.

Hope this helps, I know it's not very specific nor detailed information...

Is this other folk's experience as well? I it doesn't seem to me that we are abusing them so I am kind of freaked out.

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?

[coalhot]

Originally Posted by MrRiedemanJACC

How did you handle the Max RPM difference between the CIM and Minicim? Did you do anything or are they close enough to be interchangeable?

There's a post (by either JVN or Paul Copioli) talking about the minicims being a drop in replacement for the CIM, even with the free RPM difference. Don't feel like dragging through a whole bunch of threads to find it, but it's there.

It's actually a very useful piece of info that not many people knew when the minicims were released last year. However, it is mentioned on the VEX site

[geomapguy]

Originally Posted by coalhot

It's actually a very useful piece of info that not many people knew when the minicims were released last year. However, it is mentioned on the VEX site

From VexPro Website

The Mini CIM has 2/3 the power of a CIM motor, in a similar form-factor and with the same mounting. Similar output speeds allow Mini CIM motors to be combined in mechanisms with full-size CIM motors using the same gearing. Use this motor interchangeably with CIMs in your designs, then swap them in and out to put your power where you need it most.

[Ether]

Originally Posted by MrRiedemanJACC

How did you handle the Max RPM difference between the CIM and Minicim? Did you do anything or are they close enough to be interchangeable?

This thread may give some insight into the physics and math of combining motors:

http://www.chiefdelphi.com/forums/sh...d.php?t=123424

[Ben_R]

I am amazed at what everyone at Boom Done achieved over the three day period. The result is an epic robot!

Dr Joe, I have one question about the bull horns. What is the red material that is wrapped around the PVC of the horns? My first guess is some sort of high friction strip material.....

[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.

[Joe Johnson]

Originally Posted by Ben_R

I am amazed at what everyone at Boom Done achieved over the three day period. The result is an epic robot!

Dr Joe, I have one question about the bull horns. What is the red material that is wrapped around the PVC of the horns? My first guess is some sort of high friction strip material.....

Rubber wrap answered here. Here is info about the gearmotors. Here is info about the sticks.

ALSO, go vote for Team BOOM DONE. we are currently behind in the voting, which, while I like the other Ri3D robots, I feel pretty strongly that BOOM DONE. should be winning this vote.

Dr. Joe
_

[idahorobot]

Regarding the "Toro Sticks", how do you think they will hold up to being hit? Is there some flex or would they snap?

[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?