paper: 2014 HOT Tech Notes

[Mike Schreiber]

Originally Posted by Bryce Paputa

Love the design (and the pneumatics), but why only 50 pounds on the springs? Our design uses the same spring style, but 160 pounds which gives us a larger range and a flatter trajectory. Pretty much the same displacement as well. Also, how are your bearings set up? We tested with 80 pounds of springs and had no where near 15 ft of range.

We don't have any reason to shoot from farther out. Our shot gives us a range from about 8-18 feet. We focused on keeping the plunger super light so more of the energy can go into accelerating the ball and is not wasted accelerating the plunger. I'll get a better picture of our bearing setup for you when I'm in the shop, but you can see our outside bearings in the picture on pg 14. They capture the plunger on top and bottom.

[Adam Freeman]

Originally Posted by Adam Freeman

CAD models coming soon...

Finally got around to posting the CAD files: http://frcdesigns.com/designs-2014/

Typical CAD disclaimers apply...not everything is 100% accurate to competition robot.

This is the most complete CAD model we have created. But, most of the robot was designed in AutoCAD then Solidworks models were created to help find integration and assembly issues. We are by no means CAD/modeling experts.

Enjoy!

[g_sawchuk]

Wow, this is a great set of notes. It looks great as well, super attractive cover page. I like how you laid out every step of your process including game analysis, concepts, and design. Fantastic work, and thanks for sharing.

[tim-tim]

Originally Posted by Adam Freeman

Finally got around to posting the CAD files: http://frcdesigns.com/designs-2014/

Typical CAD disclaimers apply...not everything is 100% accurate to competition robot.

This is the most complete CAD model we have created. But, most of the robot was designed in AutoCAD then Solidworks models were created to help find integration and assembly issues. We are by no means CAD/modeling experts.

Enjoy!

Thanks Adam, and HOT! First pneumatics, now CAD. Can't wait to dive into the design.

[notmattlythgoe]

Adam, great robot this year. I look forward to reading through your design process and stealing ideas that we think will improve our process. Hope to see you guys again next year.

[April_robo]

I love that I still read every word of the Tech Notes even though I know most of it. As a new mentor its nice to have these resources around. Thanks Adam love the robot and the team.

[MrRiedemanJACC]

Adam, The step file looks great. Not so sure I'm glad I saw this, I won't be getting much sleep now!

It always amazes me how well designed your robots are and how you can push something right to the limit. The first thing I noticed is that you don't direct drive any of your wheels on the drivetrain. Is there a specific reason for that? Or do you just want to keep the weight of your Cims and gearbox centered?

Also, I am impressed with the 9 mm belts, seems like that is just too close to breaking, but I like that you were able to do that.

In the model it looks like you raised the outerwheels about 1/8"? Is that what you went with or did you need more and shaved the wheels a bit?

Thanks for posting this!

[Adam Freeman]

Originally Posted by MrRiedemanJACC

Adam, The step file looks great. Not so sure I'm glad I saw this, I won't be getting much sleep now!

It always amazes me how well designed your robots are and how you can push something right to the limit. The first thing I noticed is that you don't direct drive any of your wheels on the drivetrain. Is there a specific reason for that? Or do you just want to keep the weight of your Cims and gearbox centered?

Also, I am impressed with the 9 mm belts, seems like that is just too close to breaking, but I like that you were able to do that.

In the model it looks like you raised the outerwheels about 1/8"? Is that what you went with or did you need more and shaved the wheels a bit?

Thanks for posting this!

We've used this chassis setup for a couple of years now, so most of it just carries over from year to year. At the start we decided that it was easier to leave the gearboxes centered for packaging and CG purposes. At this point we are comfortable with the gearing and chain/belt routing that we've just left them there. It helps us get a jump start on the season knowing we can get a chassis design solidified quickly so we can move on to more game specific components of the robot.

We actually switched from the 9mm belts to 15mm belts after we broke a belt practicing before the season. We had quite a bit of practice time on that belt and only one side broke, so I would guess something might have happened to that belt when it was re-installed (we had just replaced wheels before it failed). We ended up using 15mm kevlar re-inforced belts to ensure that we didn't have any drivetrain issues. We had the space and weight, so better safe than sorry.

The only drivetrain issue we experienced this year was picking up some debris in the drive that flipped the belt over and shredded it.

We stayed with the 1/8 raise on the outside wheels. We didn't shave the wheels, but the turning performance did increase as the outside wheels wore down. We had some issues throughout the season with popping the main breaker, which I'm sure the turning scrub had quite a bit of influence.

Overall we weren't extremely happy with the chassis performance from an agility standpoint, getting out of t-bones, avoiding defense, etc. We will probably do a complete re-evaluation of the chassis size, shape, # of wheels for next year.

[Andrew Schreiber]

Originally Posted by Adam Freeman

We've used this chassis setup for a couple of years now, so most of it just carries over from year to year. At the start we decided that it was easier to leave the gearboxes centered for packaging and CG purposes. At this point we are comfortable with the gearing and chain/belt routing that we've just left them there. It helps us get a jump start on the season knowing we can get a chassis design solidified quickly so we can move on to more game specific components of the robot.

We actually switched from the 9mm belts to 15mm belts after we broke a belt practicing before the season. We had quite a bit of practice time on that belt and only one side broke, so I would guess something might have happened to that belt when it was re-installed (we had just replaced wheels before it failed). We ended up using 15mm kevlar re-inforced belts to ensure that we didn't have any drivetrain issues. We had the space and weight, so better safe than sorry.

The only drivetrain issue we experienced this year was picking up some debris in the drive that flipped the belt over and shredded it.

We stayed with the 1/8 raise on the outside wheels. We didn't shave the wheels, but the turning performance did increase as the outside wheels wore down. We had some issues throughout the season with popping the main breaker, which I'm sure the turning scrub had quite a bit of influence.

Overall we weren't extremely happy with the chassis performance from an agility standpoint, getting out of t-bones, avoiding defense, etc. We will probably do a complete re-evaluation of the chassis size, shape, # of wheels for next year.

Was this a VP belt that snapped? I ask because we ran belts on our intake this year and ended up having to replace every single VP belt at least once. We had one non VP belt from a different supplier (SDP-SI?) and it survived the entire season. Trying to see if our experience was unique or if others have seen that the VP belts have a shorter lifetime than those of other suppliers or if there was something different between the runs.

* And anyone who is worried, VP belts are probably fine for anyone who does a sane season. 125's was NOT sane.

[DampRobot]

Originally Posted by Andrew Schreiber

Was this a VP belt that snapped? I ask because we ran belts on our intake this year and ended up having to replace every single VP belt at least once. We had one non VP belt from a different supplier (SDP-SI?) and it survived the entire season. Trying to see if our experience was unique or if others have seen that the VP belts have a shorter lifetime than those of other suppliers or if there was something different between the runs.

* And anyone who is worried, VP belts are probably fine for anyone who does a sane season. 125's was NOT sane.

We had frequent 9mm belt snaps in our drivetrain, and heard similar things from other CA teams.

[Adam Freeman]

Originally Posted by Andrew Schreiber

Was this a VP belt that snapped?

Yes, it was a VP belt.

We ran at least 6 other 9mm VP belts/robot that survived an entire season (2 on intake, and 4 on outer drive wheels).

I'm pretty confident that something else happened to the one belt that snapped. We had just replaced the wheels that afternoon. Right after that, they called me and said the belt broke. I think they tried to roll the belt on to the pulley and cut it, instead of assembling it correctly with the belt on the pulley.

[JohnFogarty]

I've been analysing a lot of drive train design this summer and I've been meaning to ask since watching this year's Einstein matches. Where It seemed your drive had the worst time in escaping t-bone pins. Do you think there is a simple method to improving an 8WD to escape t-bone pins so that the power and robustness of the drive can be maintained.

The drop-down wheels that have begun popping up on various team's drives offers an interesting solution, but I'd just like to hear what you think.

[waialua359]

Originally Posted by JohnFogarty

Do you think there is a simple method to improving an 8WD to escape t-bone pins so that the power and robustness of the drive can be maintained.

The drop-down wheels that have begun popping up on various team's drives offers an interesting solution, but I'd just like to hear what you think.

We had an 8WD setup as well and T-bone pins were a problem at times. Besides the drop-down wheels solution, others employed the "hexagon" shaped frame perimeter. We plan to look at the drop down wheels as our 1st option for next season, if necessary.

[Adam Freeman]

Originally Posted by JohnFogarty

I've been analysing a lot of drive train design this summer and I've been meaning to ask since watching this year's Einstein matches. Where It seemed your drive had the worst time in escaping t-bone pins. Do you think there is a simple method to improving an 8WD to escape t-bone pins so that the power and robustness of the drive can be maintained.

The drop-down wheels that have begun popping up on various team's drives offers an interesting solution, but I'd just like to hear what you think.

I agree with your assesment... I think we were extremely bad at getting out of t-bone pins.

I'm not sure there is a simple solution to the problem. I don't think the issue was only b/c of the 8WD drivetrain setup. I think that the combination of the 8WD, long chassis, rectangular chassis shape, and driver ability all resulted in us getting stuck in a lot of t-bones.

Drop down omnis are becoming more and more common. We entertained adding breifly them during the season (after MSC), but never really pursued it to far. It would have require quite a bit of designing and changes that would have only resulted in marginal gains at Champs.

We actually started running different combination of omni wheels in the offseason that helped a little bit, but we still had issues with pins.

As Glen mentioned, we will probably evaluate different chassis shapes to help lower the chances of a full on side pin. I think it will be a point of focus for our chassis design next season.

I don't think we are ready to add in drop down wheels to our drive system. Teams like 469 and 254 did pretty well without them on a standard 6/8WD setup. I'd like to see more of a square chassis setup next year and some better driving to avoid defense. We haven't entertained switching to 6WD much in the past couple years, but it might be something to look into next year.

[AdamHeard]

Originally Posted by Adam Freeman

I agree with your assesment... I think we were extremely bad at getting out of t-bone pins.

I'm not sure there is a simple solution to the problem. I don't think the issue was only b/c of the 8WD drivetrain setup. I think that the combination of the 8WD, long chassis, rectangular chassis shape, and driver ability all resulted in us getting stuck in a lot of t-bones.

Drop down omnis are becoming more and more common. We entertained adding breifly them during the season (after MSC), but never really pursued it to far. It would have require quite a bit of designing and changes that would have only resulted in marginal gains at Champs.

We actually started running different combination of omni wheels in the offseason that helped a little bit, but we still had issues with pins.

As Glen mentioned, we will probably evaluate different chassis shapes to help lower the chances of a full on side pin. I think it will be a point of focus for our chassis design next season.

I don't think we are ready to add in drop down wheels to our drive system. Teams like 469 and 254 did pretty well without them on a standard 6/8WD setup. I'd like to see more of a square chassis setup next year and some better driving to avoid defense. We haven't entertained switching to 6WD much in the past couple years, but it might be something to look into next year.

This is all conjecture, but it looks like your chassis might have the ability to twist some vertically.

I've had a running theory for a while that a chassis such as that gets shoved into the carpet a bit odd under high defensive forces, contributing to the "locking up" affect.

Any thoughts?