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

[Joe Johnson]

Well, we ARE done, in that we've put out our reveal video (watch it here (http://www.youtube.com/watch?v=ST8ixUmxmes&feature=c4-overview-vl&list=PLpJRpRT0xvIhC6WRqjC6T4Z5n3Su78bEO))) but we are not done in that we are still planning to put out more how to videos, CAD data drop, CODE drops, improve the performance,... Stay tuned...

If you watch our reveal video: caution I have to speak fast to get in all the cool features of this robot.

Highlights of our robot:

A robot that (I believe) could pass inspection at a FIRST Competition (only known violations I am aware of is that we didn't build a red bumper and I forgot to order one of those indicator lights that are required on every robot)
Catapult. Motor powered, HIGH Release (a.k.a it can shoot over robots trying to push you away from the goals) with programmable range. We can vary release speed & release angle. Two distances are programmed now. More are just a matter of time and tuning.
Vision system (working! really, working in 3 days!) to do a killer autonomous (using RoboRealm + camera to sense hot goal and provide range to goal).
Acoustic Range To Target (again, also done in 3 days. We had not even touched the sensor until kickoff, Scout's honor).
LARGE 3 Digit ON ROBOT display which (currently) lets us show time left in match and distance to goal wall, but it can be used for many more purposes (e.g, motor current or battery voltage). Being on the robot gives the drivers useful info while keeping their eyes where they belong (again, none of this was done before kickoff)


In short, I think BOOM DONE. has earned your vote as the best Ri3D Team & Robot.
If you agree, please, vote BOOM DONE. (http://www.robotin3days.com/VoteNow/) ... NOW


Joe J.

[JB987]

Kudos to you and team! Inspiring, to say the least. Would you please share what the wrap on your el torro sticks is?

[David Brinza]

Great job, Joe!

I really like the idea of a combo range display/timer on the robot!

The motorized catapult is very cool, too! It avoids having a lot of potentially unsafe stored energy found in spring-powered catapults.

You've probably already heard enough about building a robot with an arm tied behind your back, so I won't go there. :D

[JohnSchneider]

Does your number display interface directly with the sidecar, or what kind of magic are you using?

[Brandon Holley]

I was mega impressed with BOOM. DONE.

The robot appears to play the game quite well, and the amount of sensor integration and "extra features" was impressive for a 3 day build!

We may be borrowing a few of your ideas :)

-Brando

[Joe Johnson]

We may be borrowing a few of your ideas :)

-Brando

I'll be crushed if people don't build on these ideas. Borrow away.

Joe J.

[Joe Johnson]

Does your number display interface directly with the sidecar, or what kind of magic are you using?

It can be done 10,000 ways but we settled on an Arduino looking at pins on the Digital Side Car. We put the range finder software in the Arduino (could be otherwise but we were out of analog pins on the CRIO). So the CRIO wiggles pins to tell the Arduino to sync the count down and/or display the range data.

More info on this to come - part numbers, code, wiring diagrams, board layouts (if you want to make a PCB -- you don't have to).

Joe J.

[MrRiedemanJACC]

You guys did an outstanding job! And no offense to your team members, but you had a lot of rookies! Congrats and thank you!

[wilsonmw04]

about the camera:
Are you using the driver station to process the images? If so, how are you dealing with the bandwidth limit?

[JohnFogarty]

Will you release your robo-realm settings? I really would like to know how you tuned it to work well in finding the hot goal.

[Joe Johnson]

about the camera:
Are you using the driver station to process the images? If so, how are you dealing with the bandwidth limit?

I have heard mixed reports with respect to bandwidth affecting processing on the driver station. Sorting through it all, I believe that this is no longer a major issue.

BUT, even if it IS an issue, the HOT or NOT call is an application where we will have time to make a decision. We have odometry from the wheel plus range finding via sonar to get our distance right (and detect a blocker in front of us -- which we can avoid using our gryo-stabilized omni-motion provided by our mecanum wheels -- have I told you how much i LOVE the feature set we put together on this robot ;-)

Joe J.

[wilsonmw04]

Dr. Joe,
Thanks for spending the time answering all these questions. I have on more: what us your current weight of the robot as it stands right now?

[Joe Johnson]

Dr. Joe,
Thanks for spending the time answering all these questions. I have on more: what us your current weight of the robot as it stands right now?

109 lbs WITH the battery & bumper so we are 40-50 lbs under the limit.

Oh a clarification. Someone asked on Twitter if the bumpers were removable. Yes, the are (or would be if we had guarded the pop rivet gun from Nate -- we'll have to drill out the one rivet he got off before I smacked him upside the head -- we were almost all rookies on the team after all ;-)

Joe J.

[pilum40]

Dr. Joe:
I'm the coach for Team 3355 in Arlington, Texas. My team is frankly open mouthed about Boom Done. We did have a couple of questions please...for now...:)
1. When you use "green cord" in your shooter", what kind of cord do you use? Did you custom make the pulley for this cord or is it off the shelf?
2. What was the gauge of wire you used for your catapult/shooter? Did you hand form it or have it made?
3. What was the material you used for the "Toro Horns" please? We have a running bet (lunch) that it was rough sports tape or something similar. Please let us know, we're all hungry!!

Thanks in advance!

Steve Miller-Coach
The Purple Vipers

[magnets]

Wow. I'm really, really impressed. For three days, and a crew of non FIRST engineers, you guys did an epic job. All aspects of the robot are incredibly innovative, and I think, the most impressive of the RI3D teams. Even though your team came into this with little FRC experience, your design is refined and seems really durable.

I'm a massive fan of the bumper/frame design, as well as the pickup. I think we'll see a large number of these out on the field this year, because they really are a great solution.

I'm also blown away with the software that you guys have going with the camera and the arduino rangefinder display thing, which is super neat.

[Sean Raia]

I am still in awe as to how you guys pulled this off. This robot looks like it can compete with the best of them.

I really like the acquiring system and the consistent catapult. And Im baffled at the amount of electronic features this robot has built into it.

A sure winner of the Ri3D lot if you ask me.

[Joe Johnson]

Dr. Joe:
I'm the coach for Team 3355 in Arlington, Texas. My team is frankly open mouthed about Boom Done. We did have a couple of questions please...for now...:)
1. When you use "green cord" in your shooter", what kind of cord do you use? Did you custom make the pulley for this cord or is it off the shelf?
2. What was the gauge of wire you used for your catapult/shooter? Did you hand form it or have it made?
3. What was the material you used for the "Toro Horns" please? We have a running bet (lunch) that it was rough sports tape or something similar. Please let us know, we're all hungry!!

Thanks in advance!

Steve Miller-Coach
The Purple Vipers

Green Cord. It is the metric size solid core urethane round belt on this page from McMaster (http://www.mcmaster.com/#urethane-round-belts/=q5yxeg) I use a ton of the 6mm (8112K33), but the 4mm stuff is also great. Run it around the pulleys to get a free length, cut the belt 3-6% short, use a lighter to melt the end (act like you are making a golden brown marshmallow), press together the ends, hold til cool, trim the joint with a side cutter. It is a REALLY useful way to spin something at a distance.

Pulleys are laser cut acrylic 1/8th thick. We cut a ton of these with a "FIRST standard" bolt hole pattern 1/2" increments. We then can stack up plates to make pulleys. These are not just good for actual robots but especial for prototyping.

Loop Gauge of wire is 1/4" steel. We had it laying around the shop.

Toro Horns. You are not going to believe it: Schedule 80 PVC (thicker wall than Schedule 40). I heated up some 1/2" hex shaft and melted it in place so that a Versaplanetary shaft fits tight inside.

Dr. Joe


* which roughly stated is (6) #10 holes on a 1.875" bolt circle with a 1.125" center hole.

[Ernst]

Does Ri3D give an "Innovation in Control" award? If so, you nailed it.

[AllenGregoryIV]

Great job, I love how you all managed to innovate in such a short amount of time.

What was the final gear ratio for shooter?

[Henrique Schmit]

Bravo, my new favorite RI3D team, i'd not be surprised to see this robot in the championship finals.
I really loved that bumper idea and you really innovated with the control stuff and sensors. Are you going to post the cad models and code you used? Where?

[Joe Johnson]

Great job, I love how you all managed to innovate in such a short amount of time.

What was the final gear ratio for shooter?

Working on a spec page but 15:1 is the short answer.

[mbshark]

Will there be a vid on the youtube channel or twitter or something on robotin3days.com when you guys put up a cad? Right now each team's blog is just bios of you guys like its been for forever and the only place where you see new stuff is youtube and twitter. Also the only CAD for Ri3D that I found was team Andymark and it was on a CD post - Are there any more currently available?

[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?

[Shmuel]

15:1
Is that gear ratio including the sprocket, or just the gear box?
Also thank you for what you are doing, your robot is really amazing.

[billbo911]

I'm completely in awe of this "3 day robot", Amazing!!

We are planning on doing a similar process with a range finder + display, though it will be with our own twist of course.
We too plan on using a couple of onboard co-processors to do this work. Arduino for display and PCDuino for vision. This will eliminate the need for any additional WiFi bandwidth.

I would love to see the Arduino code you are using and any specs you might have on the US sensor you used.

What, if any, protocol are you using to communicate between the Arduino and the cRio?

[Joe Johnson]

I'm completely in awe of this "3 day robot", Amazing!!

We are planning on doing a similar process with a range finder + display, though it will be with our own twist of course.
We too plan on using a couple of onboard co-processors to do this work. Arduino for display and PCDuino for vision. This will eliminate the need for any additional WiFi bandwidth.

I would love to see the Arduino code you are using and any specs you might have on the US sensor you used.

What, if any, protocol are you using to communicate between the Arduino and the cRio?

Working on publishing this. Stay tuned.

Joe J.

[msaunders]

Very Nice.
What is the reduction used for the macanum's?

[geomapguy]

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

[bhsrobotics1671]

Green Cord. It is the metric size solid core urethane round belt on this page from McMaster (http://www.mcmaster.com/#urethane-round-belts/=q5yxeg) I use a ton of the 6mm (8112K33), but the 4mm stuff is also great. Run it around the pulleys to get a free length, cut the belt 3-6% short, use a lighter to melt the end (act like you are making a golden brown marshmallow), press together the ends, hold til cool, trim the joint with a side cutter. It is a REALLY useful way to spin something at a distance.

Pulleys are laser cut acrylic 1/8th thick. We cut a ton of these with a "FIRST standard" bolt hole pattern 1/2" increments. We then can stack up plates to make pulleys. These are not just good for actual robots but especial for prototyping.

Loop Gauge of wire is 1/4" steel. We had it laying around the shop.

Toro Horns. You are not going to believe it: Schedule 80 PVC (thicker wall than Schedule 40). I heated up some 1/2" hex shaft and melted it in place so that a Versaplanetary shaft fits tight inside.

Dr. Joe


* which roughly stated is (6) #10 holes on a 1.875" bolt circle with a 1.125" center hole.

I am assuming this is in the works as well, but we are really curious on the reduction used for the Toro Horns and if you feel that was the optimum reduction or would have used something else if you had access to it?

[geomapguy]

I am assuming this is in the works as well, but we are really curious on the reduction used for the Toro Horns and if you feel that was the optimum reduction or would have used something else if you had access to it?

http://www.chiefdelphi.com/forums/showpost.php?p=1323987&postcount=54

[Joe Johnson]

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]

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 (http://www.youtube.com/watch?v=NqgDXPfyA2o)

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

Dr. Joe

[Calvin Hartley]

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]

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]

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]

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 (http://www.vexrobotics.com/vexpro/motor-controllers/217-3371.html)

[geomapguy]

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 (http://www.vexrobotics.com/vexpro/motor-controllers/217-3371.html)

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]

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/showthread.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]

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]

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]

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 (http://www.chiefdelphi.com/forums/showpost.php?p=1323754&postcount=41). Here is info about the gearmotors (http://www.chiefdelphi.com/forums/showpost.php?p=1323987&postcount=54). Here is info about the sticks (http://www.chiefdelphi.com/forums/showpost.php?p=1323966&postcount=17).

ALSO, go vote for Team BOOM DONE (http://www.robotin3days.com/VoteNow/). 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]

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]

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]

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:

Go here (https://docs.google.com/file/d/0B7ZuWrzk1wi3alkzSnFOSTkxQ1U/edit)(there is some sort or error message here but ignore it)
File menu > Download.
BOOM DONE.

[magnets]

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:

Go here (https://docs.google.com/file/d/0B7ZuWrzk1wi3alkzSnFOSTkxQ1U/edit)(there is some sort or error message here but ignore it)
File menu > Download.
BOOM DONE.


It works for me from this link. Thanks!

[magnets]

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.

[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.

[David Brinza]

Dr. Joe,

Congrats on winning the poll for best Ri3D robot!

The final vote was too close for comfort, given the capabilities you both demonstrated and explained.

I should have taken a class in marketing, because the second place robot certainly had a "wow" factor in their release video (cool lights, sound track, slow-motion). "Form before function?"

BTW, we're also interested in the sonar sensor you used. We've had mixed results with the Maxim devices (although we figured out some of the pitfalls).

[Ether]

the rollers have a TON of play

axial or radial? or both?

[Joe Johnson]

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.

All the sonar stuff is on the Arduino. We currently don't send the distance data anywhere but the display. This was just an interim solution. Long term we want the CRIO to have access to the distance data. We also are thinking about some interference detection/avoidance methods. Stay tuned...

Dr. Joe

[billbo911]

All the sonar stuff is on the Arduino. We currently don't send the distance data anywhere but the display. This was just an interim solution. Long term we want the CRIO to have access to the distance data. We also are thinking about some interference detection/avoidance methods. Stay tuned...

Dr. Joe

We will be doing a similar approach, but a bit backward to your approach. We already have the Arduino running the US sensor and displaying the relative distance via an addressable LED strip.
Our final design will have the cRio doing the actual distance measurements, that way it can position accurately by itself, and passing the distance info to the Arduino to display info to the driver. The display may end up on the Driver's Station, or on the robot, or both. All is still TBD.

[MikeZ]

All the sonar stuff is on the Arduino. We currently don't send the distance data anywhere but the display. This was just an interim solution. Long term we want the CRIO to have access to the distance data. We also are thinking about some interference detection/avoidance methods. Stay tuned...

Dr. Joe

Dr Joe

Great job and thanks for your posts. Question on the sonar. I noted in your specs and capability document a reference to a sonar horn/cone made from sheet metal. We have tried the same ultrasonic sensor will mixed results so would appreciate if you could elaborate a bit on your cone design and how it enhanced sensor performance. Many thanks.

[Tom Line]

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.

[ekapalka]

Working on a spec page but 15:1 is the short answer.
Please excuse my lack of intelligence, but aside from using the Green Cord to spare your motors, what stopped you from simply using AndyMark gearboxes with that or a similar reduction (like a pair of 8.75:1 toughboxes with reduces by 2:1 on the output)? Is there some other mechanical advantage to using the gigantic sprockets? Thanks!

[JohnFogarty]

Toro Horns. You are not going to believe it: Schedule 80 PVC (thicker wall than Schedule 40). I heated up some 1/2" hex shaft and melted it in place so that a Versaplanetary shaft fits tight inside.

Dr. Joe


* which roughly stated is (6) #10 holes on a 1.875" bolt circle with a 1.125" center hole.

So. We're in our shop today trying to figure out a way to expand the 1/4" Schedule 80 PVC to fit onto the 1/2" hex shaft and it seems to be quite a challenge. How did you do it?

[AllenGregoryIV]

So. We're in our shop today trying to figure out a way to expand the 1/4" Schedule 80 PVC to fit onto the 1/2" hex shaft and it seems to be quite a challenge. How did you do it?

We played around with it too, it's pretty easy if you heat up the 1/2" hex shaft.

We just clamped a 1/2" hex shaft in a vise sticking straight up. Then we just heated it with a heat gun, didn't even need to use a torch. Then just press the 1/2" Schedule 80 PVC on to the hex shaft. We just pressed it by hand, it wasn't easy but it wasn't that difficult.

[JohnFogarty]

Our problem is we have been heating up the PVC. We've decided on a different way to secure the tubing to the hex shaft that will work just as well I think.

[Joe Johnson]

We played around with it too, it's pretty easy if you heat up the 1/2" hex shaft.

We just clamped a 1/2" hex shaft in a vise sticking straight up. Then we just heated it with a heat gun, didn't even need to use a torch. Then just press the 1/2" Schedule 80 PVC on to the hex shaft. We just pressed it by hand, it wasn't easy but it wasn't that difficult.

Yes, this is exactly what we did. Heat one end of a small (~6") hex shaft -- the other end in a vice. Get it hot and then just push the PVC tube onto the hot hex shaft.

Worked great for us.

Note. It is the size Schedule 80 that has a hole of a little bigger than 1/2"

That is the beautiful thing about Schedule 80 (rather than Schedule 40 available at Home Depot, Lowes, ...): you can get them in sizes with IDs just a hair bigger than 1/4", 3/8", & 1/2". That makes the perfect for making spacers for 1/4", 3/8", & 1/2" shafts.

FWIW.

Dr. Joe

[Joe Johnson]

Please excuse my lack of intelligence, but aside from using the Green Cord to spare your motors, what stopped you from simply using AndyMark gearboxes with that or a similar reduction (like a pair of 8.75:1 toughboxes with reduces by 2:1 on the output)? Is there some other mechanical advantage to using the gigantic sprockets? Thanks!

I was scared of the impact loads we were going to put into the arm. So, I worried about going with a "live axle" where we transmit the torque to the arm via a hex shaft (or worse, a 1/2" round with a single key).

So... ...we went with a larget sprocket on the last stage because then we get to transfer the torque to the arm out at a nice (6" in our case) radius. Also, we have all those teeth engaged rather than just a tooth or two.

We went with the green cord on the first stage because it is springy and it can slip. This lets the energy in the armatures go someplace other than into breaking gear teeth and/or snapping chain.

COULD we make a Toughbox work? Maybe yes. But, we made the thing we had work so, I have an existence proof the system with chain and green cord working. I like that the loads are lower and the energy has someplace to go. So... ...unless I had a compelling reason to go another way, I wouldn't change.

Dr. Joe

[Team1339]

We are going to be using the 7 segment display and the rangefinder and we wanted to know how you mounted them.

Thank you!

[nxtmonkeys]

My team is in its rookie year, and we were sooo glad that there were RI3D teams such as Boom Done this year. Without them, we would probably not be anywhere close to where we are now with our bot. Thanks!


We used #35 chain on our sprockets, so we don't have to worry about the chain breaking at all. :]

[discobrisco]

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.


I was looking at this and I thought id add we had to switch to andymark mecanums because in one of our rounds we literally broke off half of our rollers on one of the vex. Andymark haven't had any problems yet. Also, is it legal to have 4 mini cims with 2 bags? Rules seemed to make it seem like it was up to 4 total instead of each.

[Whippet]

Rules seemed to make it seem like it was up to 4 total instead of each.

The FRC Manual states any combination of up to four VEX BAG and/or mini-CIM motors may be used, per R29. This means that you can have two mini-CIMs and two BAGs, three mini-CIMs and one BAG, four mini-CIMS and no BAGS, etc. Your stated configuration would be illegal because it totals greater than four of the stated motors.