New AndyMark Product Game Hint??? [Archive]

Sam Skoglund

14-12-2016, 16:48

So this new product (http://www.andymark.com/product-p/am-3462.htm)just popped up on AndyMark today...

Last year they released the track drive and we had to traverse daunting obstacles...

This year they are releasing a wheel that "gives way to allow rigid objects to be manipulated easily. This makes for high-performance intakes and internal conveyors."

Thanks for the hint AndyMark.

Looks to me like we will be handling rigid, chunky shaped coal game pieces this season.

Christopher149

14-12-2016, 16:51

I didn't notice the bit about rigid objects - half the appeal at first glance is that it is like the Entrapption Stars, but with a hex bore.

Edit: are we getting wiffle balls?

bobbysq

14-12-2016, 16:51

I believe this was also around the time that the Rhino Drive was released. I think you're on to something.

Monochron

14-12-2016, 16:52

For picking up cogs and gear game pieces to hang somewhere obviously :D

marshall

14-12-2016, 16:57

For picking up cogs and gear game pieces to hang somewhere obviously :D

Creative reuse of the leftovers from last year's field...

Ty Tremblay

14-12-2016, 16:57

I believe this was also around the time that the Rhino Drive was released. I think you're on to something.

The Rhino Drive was actually a coincidence and had nothing to do with the upcoming 2016 game.

CalTran

14-12-2016, 17:01

Obviously this is a throwback year and we'll be driving over corn again.

Sperkowsky

14-12-2016, 17:03

The Rhino Drive was actually a coincidence and had nothing to do with the upcoming 2016 game.

Do you have proof of this? I know Andymark was aware of atleast the basic game concept early. Even if there was some coincidence and the product was already in development, I have no doubt AM sped up the creation of the product once they knew about the game. The story I have heard was it was for non-frc use and I have a hard time thinking they would spend valuable time around the FRC season spent on a non FRC product.

Do I think these wheels mean the game has a hard object? Not necessarily. These remind me of the conveyor belt wheels or "marshmallow" wheels as I have heard a lot of people call them. I am really happy that these are going to be made now with a 1/2" hex interface as it saves the need for a hub or a broaching operation.

BotDesigner

14-12-2016, 17:04

This sure is reinforcing the idea that some object (or different objects) representing coal are the gamepieces.

Lireal

14-12-2016, 17:07

The Rhino Drive was actually a coincidence and had nothing to do with the upcoming 2016 game.
Do you have proof of this? I know Andymark was aware of atleast the basic game concept early. Even if there was some coincidence and the product was already in development, I have no doubt AM sped up the creation of the product once they knew about the game. The story I have heard was it was for non-frc use and I have a hard time thinking they would spend valuable time around the FRC season spent on a non FRC product.

For this season, FIRST did give some distributors, including Andymark, advanced notice about some qualities of the game. I would not be suprised if they have done the same for the coming season. Read here (https://www.chiefdelphi.com/forums/showthread.php?t=143165) for full information.

SenorZ

14-12-2016, 17:13

Does $6 for a 2" wheel seem a bit steep to anyone else?
[EDIT: just saw how expensive the tear drop flex rollers are!!!]

Seen similar wheels on many 2015 robots for landfill tote gathering.

Ari423

14-12-2016, 17:14

I didn't notice the bit about rigid objects - half the appeal at first glance is that it is like the Entrapption Stars, but with a hex bore.

Edit: are we getting wiffle balls?

I never understood why they were made with a 0.5" square bore instead of hex. I imagine (with absolutely no real-world testing of course) these new wheels won't work as well as the entrapption stars for intakes of spheres, like the boulders this year because the stars can get more than tangential contact. I would love to see AndyMark come with with a v2 of the stars with a 0.5" hex bore just for ease of use.

As for wiffle balls, if you are talking about the am-3364 under "Customers Also Viewed", they are game pieces for FTC this year, not a mistake by AndyMark in releasing FRC game pieces early.

Caleb Sykes

14-12-2016, 17:23

As for wiffle balls, if you are talking about the am-3364 under "Customers Also Viewed", they are game pieces for FTC this year, not a mistake by AndyMark in releasing FRC game pieces early.

We'll know if we discover the game piece by accident because the thread with the discovery will get shut down.:p

AdamHeard

14-12-2016, 17:23

Does $6 for a 2" wheel seem a bit steep to anyone else?
Seen similar wheels on many 2015 robots for landfill tote gathering.

Yes and no, they do appear to be waterjet out of sheet... and the material isn't that cheap. For low qty production the price seems about right.

[QOUTE]I never understood why they were made with a 0.5" square bore instead of hex. I imagine (with absolutely no real-world testing of course) these new wheels won't work as well as the entrapption stars for intakes of spheres, like the boulders this year because the stars can get more than tangential contact. I would love to see AndyMark come with with a v2 of the stars with a 0.5" hex bore just for ease of use. [/QUOTE]

Looks like these would be fairly easy to modify by cutting the ring out and getting 6 point star.

Cothron Theiss

14-12-2016, 17:29

D.Allred

14-12-2016, 17:30

Does $6 for a 2" wheel seem a bit steep to anyone else?
[EDIT: just saw how expensive the tear drop flex rollers are!!!]

Seen similar wheels on many 2015 robots for landfill tote gathering.

Not really. What's your alternative for this application?

I've seen team use something similar to the 4" flex wheel from McMaster (2497K12 for example). Those are $30+.

Another alternative was making your own roller from polyurethane tubing - which isn't cheap either.

David

Ari423

14-12-2016, 17:31

Looks like these would be fairly easy to modify by cutting the ring out and getting 6 point star.

True, but then they wouldn't be COTS. So they take manufacturing time and replacements, which will probably be necessary as they take a beating spinning at high speeds, will count against withholding. Also just the extra effort. Comparatively, I would rather pay an extra dollar or two per wheel/star to get a COTS 0.5" hex star than have to modify it. That's just me coming from a small team with limited manpower and manufacturing capabilities; I imagine for larger teams like 973 that is not a problem.

BumblingBuilder

14-12-2016, 17:40

Does $6 for a 2" wheel seem a bit steep to anyone else?
[EDIT: just saw how expensive the tear drop flex rollers are!!!]

Seen similar wheels on many 2015 robots for landfill tote gathering.

A good "on a budget" alternative to these holed wheels is always the banebot wheel (orange or bue ideally, which are -/+ 5A of these wheels respectively). They worked well in 2015, so I can't imagine them not working well if we're getting rigid game pieces next year

Munchskull

14-12-2016, 17:57

Could just be me never having used the material but .425" seem like it would be fairly extreme for an interference fit.

Lil' Lavery

14-12-2016, 18:00

Bob Steele

14-12-2016, 18:11

Yes and no, they do appear to be waterjet out of sheet... and the material isn't that cheap. For low qty production the price seems about right.

[QOUTE]I never understood why they were made with a 0.5" square bore instead of hex. I imagine (with absolutely no real-world testing of course) these new wheels won't work as well as the entrapption stars for intakes of spheres, like the boulders this year because the stars can get more than tangential contact. I would love to see AndyMark come with with a v2 of the stars with a 0.5" hex bore just for ease of use.

We used modified entrapption stars that had hex bores to collect the frisbees from the floor in Ultimate Ascent... they worked quite well. We had a friend from Indianapolis make them for us. (Mike Trapp actually) He is a great guy by the way!! An unsung supporter of FIRST and STEM education.

Oblarg

14-12-2016, 18:11

This is arguably consistent with the ball-nonball gamepiece trend, if it is at all indicative of "rigid objects" being game pieces.

AdamHeard

14-12-2016, 18:12

This is arguably consistent with the ball-nonball gamepiece trend, if it is at all indicative of "rigid objects" being game pieces.

Balls can be rigid.

Richard Wallace

14-12-2016, 18:13

Could just be me never having used the material but .425" seem like it would be fairly extreme for an interference fit.

I noticed that as well, but I'm assuming the AndyMark team found it was easy enough to use.

Maybe 0.425" fits tightly on a Churro? If so, then it is even tighter on hex shaft stock.

Oblarg

14-12-2016, 18:19

Balls can be rigid.

Most balls are not, though, thus my inclusion of the word "arguably" ;)

Hitchhiker 42

14-12-2016, 18:22

The word "conveyor" seems to stir up something in my mind... Maybe those fragmented pieces of conveyor belts hidden all over the images they released in the DLC packs?

Richard Wallace

14-12-2016, 18:25

Most balls are not, though, thus my inclusion of the word "arguably" ;)

This is what makes Chief Delphi great! :rolleyes: Argumentation FTW.

Seriously, any particular game is not played with most balls. We'll get the selected balls, or none.

However, if we do get balls and they are rigid, then I really hope they are also very light.

https://www.chiefdelphi.com/media/img/a82/a824bceaf0029434c821c11052af9196_l.jpg

mr.roboto2826

14-12-2016, 18:44

Maybe 0.425" fits tightly on a Churro? If so, then it is even tighter on hex shaft stock.

.425" Seems about right for a "rubber esque" material. 2826 has used a material called linatex in the past which looks almost identical to what is pictured. We often had .125" to .25" of under sizing on our interference fit. I'm sure Andymark can enlighten me as to the actual material, but I', sure they tested if thoroughly.

Nick Lawrence

14-12-2016, 18:54

Ooh, this looks really nice. These wheels would be super helpful for intaking rigid game pieces. At first glace, I was concerned about the hex shaft turning inside of the hex, but .425 is a hilariously heavy interference fit. I do wonder if using Thunderhex with these wheels would pose any issues. I doubt it, but I can't really say for sure.

Emphasis mine.

We actually cut a bunch of samples over the summer in .025" increments to test this size, and found that .425" flat-to-flat is the right number for this specific profile and material combination. This number would change for a harder or thicker material, as well as a part with less holes in it.

-Nick

billbo911

14-12-2016, 18:57

Balls can be rigid.

The Nerf Howler (http://nerf.hasbro.com/en-us/product/nerf-n-sports-vortex-aero-howler-football-green:61511713-5056-900B-108A-4B432DF797AE) is actually quite rigid!

Throw one and see if you hear a Steam Train Whistle!

frcguy

14-12-2016, 19:14

Peyton Yeung

14-12-2016, 21:34

Wish these were out for our FTC robot this year. The particles are really rigid.

sanddrag

15-12-2016, 02:33

I'd pay $7 each if they were black. ;)

Cothron Theiss

15-12-2016, 02:48

I'd pay $7 each if they were black. ;)

Then just anodize them!

But what if da red wunz go fasta!?

Andrew_L

15-12-2016, 02:58

I'd pay $7 each if they were black. ;)

Definitely would appreciate a more neutral color.

Cothron Theiss

15-12-2016, 03:31

Emphasis mine.

We actually cut a bunch of samples over the summer in .025" increments to test this size, and found that .425" flat-to-flat is the right number for this specific profile and material combination. This number would change for a harder or thicker material, as well as a part with less holes in it.

-Nick

Ok, so should we see the hex shaft removing silicone from the inside of the hex when we press it in, or should the material stretch to fit around the hex shaft?

Richard Wallace

15-12-2016, 06:01

Ok, so should we see the hex shaft removing silicone from the inside of the hex when we press it in, or should the material stretch to fit around the hex shaft?

Hmm... How sharp will the hex shaft be?

Do we round off the end of a Churro, and push that through?

Or freeze the part, then push a hex broach through it?

Michael Hill

15-12-2016, 06:22

I'm curious if Thunderhex will be to round to get a good grip.

Nick Lawrence

15-12-2016, 09:22

Ok, so should we see the hex shaft removing silicone from the inside of the hex when we press it in, or should the material stretch to fit around the hex shaft?

The wheel should stretch around the axle.

-Nick

Chris is me

15-12-2016, 09:57

This is a great product that basically didn't exist before and is far cheaper / lighter than the previous COTS solution for this particular product. I think whining that the color isn't perfect is really not productive!

I also don't think this is, necessarily, inspired by the game. Compliant wheels have been gaining traction (heh) for years, for both intakes and shooters; for compliant game pieces or rigid ones. Did I mention the alternative was $30 on McMaster and with a hub weighed like a pound?

I'm curious to see how well these hold up at 5K RPM, and if they slip on the shaft or anything at that high of a speed.

billbo911

15-12-2016, 10:16

... Compliant wheels have been gaining traction (heh) for years, for both intakes and shooters; for compliant game pieces or rigid ones.....I'm curious to see how well these hold up at 5K RPM, and if they slip on the shaft or anything at that high of a speed.

I'm not so sure these are well suited for shooters, but time, and testing, will tell.
AM does recommend them for intakes and conveyors though.
Recommended usage...This makes for high-performance intakes and internal conveyors.

AdamHeard

15-12-2016, 10:50

Hey meme king Wil Payne can you edit the word "trap" to "hint"?

Thanks!

http://i.imgur.com/LaJ9Kmo.gif

Richard Wallace

15-12-2016, 11:02

I'm not so sure theseare well suited for shooters, but time, and testing, will tell. ...

I think these might be good for shooting some things. Maybe wiffle balls?

But the GDC would never do that to us, right? :confused:

jamesmcip

15-12-2016, 11:06

The Nerf Howler (http://nerf.hasbro.com/en-us/product/nerf-n-sports-vortex-aero-howler-football-green:61511713-5056-900B-108A-4B432DF797AE) is actually quite rigid!

Throw one and see if you hear a Steam Train Whistle!

That shape is disturbingly close to the blimp flying at the top of the Steamworks trailer...

AdamHeard

15-12-2016, 11:08

I think these might be good for shooting some things. Maybe wiffle balls?

But the GDC would never do that to us, right? :confused:

I have said GDC won't give us shooters next year before each of the following year;
2013
2014
2016

BumblingBuilder

15-12-2016, 11:26

But what if da red wunz go fasta!?

I can attest to the fact that red DOES make things go faster

rlance

15-12-2016, 11:42

That shape is disturbingly close to the blimp flying at the top of the Steamworks trailer...

This recently posted video does show a team having a robot load a Nerf football into their robot. Maybe they know something....

https://www.youtube.com/watch?v=xE3RIf0Xjfs

electroken

15-12-2016, 11:46

I think these might be good for shooting some things. Maybe wiffle balls?

But the GDC would never do that to us, right? :confused:

I drive past the one and only Wiffle factory every day and I've noticed no unusual activity lately. Plus, I probably would have heard something unless they're VERY good at keeping secrets. The place is smaller than most would think, considering every real Wiffle ball anyone has ever seen came from that little building.

Jon Stratis

15-12-2016, 11:59

The Nerf Howler (http://nerf.hasbro.com/en-us/product/nerf-n-sports-vortex-aero-howler-football-green:61511713-5056-900B-108A-4B432DF797AE) is actually quite rigid!

Throw one and see if you hear a Steam Train Whistle!

My team has actually been playing with these this fall... I wanted something challenging for them to prototype around, and these fit the bill when I saw them. At Target. First prototype shooter went about 15 feet run off a drill, could definitely go full length if we spun it up to CIM speed!

mrnoble

15-12-2016, 12:09

I agree with the several of you who don't believe that this is some sort of game reveal. These wheels have been showing up on amazing robots for at least the past several years, so it is consistent with many other FRC products that get designed, developed or implemented with high level teams and eventually become COTS. My team was developing something similar within the past year, to be 3D printed using NinjaFlex. This new product makes that effort kind of obsolete.

chandrew

15-12-2016, 12:22

Frisbee intake wheels?

BMiller2559

15-12-2016, 12:37

Well if we truly believe these are specifically designed for this year's game they should be sold out within the week and will not be back in stock until mid to late March. :ahh:

Peyton Yeung

15-12-2016, 13:40

bobbysq

15-12-2016, 14:15

Frisbee intake wheels?

Shoutouts to Team Botman's 2014 bot, which used frisbees as a grabber.

IndySam

15-12-2016, 14:51

Back in the day when Mike invented these stars for Breakaway soccer balls they worked great. We also made a version with a plastic center hub to stop the problem with rounding out the square hole, these were never released to the public.

They did solve the problem of rounded holes but that little change stiffened them up a little tiny bit and made them less effective. I was pretty amazed how that little change made such a big difference.

pfreivald

15-12-2016, 15:02

The Nerf Howler (http://nerf.hasbro.com/en-us/product/nerf-n-sports-vortex-aero-howler-football-green:61511713-5056-900B-108A-4B432DF797AE) is actually quite rigid!

Throw one and see if you hear a Steam Train Whistle!

The Nerf Howler is also in stock and readily available from Amazon.co.uk, Amazon.co.au, and elsewhere...which, combined with an earlier not-supposed-to-be-a-hint-but-was-totally-a-hint, tells me the Nerf Howler is not the game piece.

(Of the four possible hints--if you count this as one--that point to the game piece being a standard regulation football, it's the "First Choice Points to get some shipped, International Teams Only" that seals the deal in my mind. There is literally no other playing piece I can think of that is ubiquitous in the US but difficult to obtain elsewhere. I've been pretty good at guessing overall game themes most years, and game elements some years, and I've never been as convinced I'm right as I am this year.... That said, it'll be fun to be right, and as fun to be wrong.)

Branden2648

15-12-2016, 15:19

Andymark just uploaded a new video on Facebook with the following http://imgur.com/a/PHbIB

Munchskull

15-12-2016, 16:38

Andymark just uploaded a new video on Facebook with the following http://imgur.com/a/PHbIB

WHEELS!

Michael Hill

15-12-2016, 16:38

New LED Strips at AndyMark (WITH CONNECTORS EVEN!). What could this mean?

http://www.andymark.com/product-p/am-3543.htm

Lil' Lavery

15-12-2016, 16:41

(Of the four possible hints--if you count this as one--that point to the game piece being a standard regulation football, it's the "First Choice Points to get some shipped, International Teams Only" that seals the deal in my mind. There is literally no other playing piece I can think of that is ubiquitous in the US but difficult to obtain elsewhere. I've been pretty good at guessing overall game themes most years, and game elements some years, and I've never been as convinced I'm right as I am this year.... That said, it'll be fun to be right, and as fun to be wrong.)

That international game piece option was available in 2016, as well.

mrnoble

15-12-2016, 16:55

That international game piece option was available in 2016, as well.

Yeah, that's just a good response to the years of problems with international teams being unable to get the most basic stuff to compete. I agree that it doesn't give anything away.

mrnoble

15-12-2016, 17:18

Of the four possible hints

Sorry, I'm out of it. What are these hints? I am aware of the dirigible in the teaser video, but I have yet to see any other hints. I haven't been sauntering through CD very much lately, though, so I am sure I've missed it here. Would you mind terribly sharing what the possible "hints" were? Thanks.

pfreivald

15-12-2016, 17:18

That international game piece option was available in 2016, as well.

I wasn't aware of that.

Ah, well. Back to the speculation that I'm probably wrong.... :D

ctt956

15-12-2016, 17:49

But what if da red wunz go fasta!?

Add a few flame stickers. Problem solved! :p

Andymark just uploaded a new video on Facebook with the following http://imgur.com/a/PHbIB

I started to think that dice(any size) might be game pieces. I see a Rubik's Cube in that picture...Vex Starstruck has a cube-shaped game piece... There's also a small toy robot between the large grey wheel and the stack of wheels. Minibot hint?

nuclearnerd

15-12-2016, 18:08

Commander Canada wishes all of our friends across the world a wonderful holiday season. #omgrobots #WeWouldntDareDoATeaserInThis #NahWeWould

https://twitter.com/andymarkinc/status/809484665857986560

What Christmas goodies has Nick been baking for us?

Christopher149

15-12-2016, 18:20

New LED Strips at AndyMark (WITH CONNECTORS EVEN!). What could this mean?

http://www.andymark.com/product-p/am-3543.htm

That FTC teams want lights?

Vyrotek

15-12-2016, 19:03

Munchskull

15-12-2016, 19:29

https://twitter.com/andymarkinc/status/809484665857986560

:ahh: What the heck is holding up the Canadian flag right at the beginning? That seems to resemble a pole climbing or zipline minibot/mechanism of some sort...

I don't know what it is but I don't like it...I have heard the whispers or horror stories of mini bots.

Andrew_L

15-12-2016, 20:45

http://i.imgur.com/d9RhYmy.png

I hate to say it, but that's definitely a pole-climbing minibot. You can see the two motors (top one on the left side of the chassis, bottom one on the right side of the chassis), and the power connector wires falling underneath the frame. The frame has cutouts to guide the minibot along the pole near the top.

Sperkowsky

15-12-2016, 21:03

frcguy

15-12-2016, 21:07

The Nerf Howler is also in stock and readily available from Amazon.co.uk, Amazon.co.au, and elsewhere...which, combined with an earlier not-supposed-to-be-a-hint-but-was-totally-a-hint, tells me the Nerf Howler is not the game piece.

An item's availability on Amazon and other retailers is not a very good indicator of it being used as a FRC game piece, especially since FIRST almost always has game pieces made with some kind of branding on them.

Andrew_L

15-12-2016, 21:08

What do you think the limit switch at the top is for? Seeing if the minibot hits the top?

For you youngin's that weren't around in 2011, a common minibot design included a limit switch at the top to cut power to the motors as soon as the minibot impacted the plate at the top of the pole.

frcguy

15-12-2016, 21:09

For you youngin's that weren't around in 2011, a common minibot design included a limit switch at the top to cut power to the motors as soon as the minibot impacted the plate at the top of the pole.

What are the chances that the minibot shown is from 2011 and AndyMark is just messing with us?

Andrew_L

15-12-2016, 21:10

What are the chances that the minibot shown is from 2011 and AndyMark is just messing with us?

Almost 100%.

EDIT: 100% chance that it's a minibot from 2011. Whether AM is just trolling or not I don't know, nor is it late enough in December for me to actually care. :rolleyes:

Knufire

15-12-2016, 22:44

What are the chances that the minibot shown is from 2011 and AndyMark is just messing with us?

Because of how overvalued minibots were, the top teams iterated on these until there was pretty substantial design convergence to the minibot you saw in the video. Very similar to the arms race of can grabbers in 2015.

Lil' Lavery

16-12-2016, 01:23

I'm far more interested to know what's in Lawrence of Canadia's hand in that video.

Andrew_L

16-12-2016, 01:35

I'm far more interested to know what's in Lawrence of Canadia's hand in that video.

Looks like a DOG shifter.

frcguy

16-12-2016, 01:37

I'm far more interested to know what's in Lawrence of Canadia's hand in that video.

Looks like a dog gear (http://www.andymark.com/Gear-p/am-0020.htm), although I'm not certain.

Nick Lawrence

16-12-2016, 09:05

I'm far more interested to know what's in Lawrence of Canadia's hand in that video.

Woof.

-Nick

marshall

16-12-2016, 09:33

Woof.

-Nick

https://www.youtube.com/watch?v=2AkLE4X-bbU

Andrew_L

16-12-2016, 11:45

Woof.

-Nick

This chassis was equipped with a pneumatic system with two 35 CI Clippard tanks to run new prototype shifting transmissions, with a high frequency of shifting cycles.

-Nick

Come on Nick, show us the 1.5 lb flipcim shifting transmission. ;)

jwfoss

16-12-2016, 11:48

Come on Nick, show us the 1.5 lb 3 flipcim shifting transmission. ;)

Fixed it for you.

Andrew_L

16-12-2016, 12:39

Come on Nick, show us the 1.5 lb 3 flipcim shifting brownout transmission. ;)

Fixed it for you.

Still seems a bit overkill to me.

The_ShamWOW88

16-12-2016, 13:19

I can attest to the fact that red DOES make things go faster

Most car insurance companies would agree with you

GeeTwo

16-12-2016, 21:35

Because of how overvalued minibots were, the top teams iterated on these until there was pretty substantial design convergence to the minibot you saw in the video. Very similar to the arms race of can grabbers in 2015.

I never heard of anyone treating motors with liquefied gasses in 2015. My understanding is that the 2011 minibot arms race was steeper than the 2015 grabbers. What surprised me when I went back and read about it was that no one (as far as I found) had implemented an ultra-simple CVT (continuously variable transmission) nor taken advantage of the ability of the minibot to have a mobile center of gravity.

Wait, what? Ultra-simple CVT? That can't be!
Actually, for a short, drag-race type run, there IS an ultra-simple CVT design. Don't think of doing this in gears, but in the diameter of the wheel. That is, start with a rather small wheel engaging the climb shaft, but with a bit of tread wrapped around it so that the wheel diameter increases (and therefore the effective gear ratio decreases) as the mini-bot completes its run. With proper design of the initial wheel shape, this transition can be continuous.

Mobile Center of Gravity? Whachu Talkin' 'bout, Willis? While it was a while back that I looked at the mini-bot rules, it seemed to me that a mini-bot was allowed to be about three times as tall as it actually had to be. So -- build the mini-bot to the shortest length possible, then stand it on a "rack" which raises it to the highest initial altitude allowed. As the robot climbs, the "rack" automatically climbs relative to the robot weight, until, at the top of the climb, the rack reaches the roof to signal contact, though the "real minibot" is still several inches lower.

Billfred

16-12-2016, 21:52

I never heard of anyone treating motors with liquefied gasses in 2015. My understanding is that the 2011 minibot arms race was steeper than the 2015 grabbers. What surprised me when I went back and read about it was that no one (as far as I found) had implemented an ultra-simple CVT (continuously variable transmission) nor taken advantage of the ability of the minibot to have a mobile center of gravity.

Wait, what? Ultra-simple CVT? That can't be!
Actually, for a short, drag-race type run, there IS an ultra-simple CVT design. Don't think of doing this in gears, but in the diameter of the wheel. That is, start with a rather small wheel engaging the climb shaft, but with a bit of tread wrapped around it so that the wheel diameter increases (and therefore the effective gear ratio decreases) as the mini-bot completes its run.

Mobile Center of Gravity? Whachu Talkin' 'bout, Willis? While it was a while back that I looked at the mini-bot rules, it seemed to me that a mini-bot was allowed to be about three times as tall as it actually had to be. So -- build the mini-bot to the shortest length possible, then stand it on a "rack" which raises it to the highest initial altitude allowed. As the robot climbs, the "rack" automatically climbs relative to the robot weight, until, at the top of the climb, the rack reaches the roof to signal contact, though the "real minibot" is still several inches lower.

The arms race in 2011 was absolutely real, and way more expensive since you were using Tetrix battery packs (and of course you have more than one) and probably smoking Tetrix motors pretty regularly at the higher levels. 2815 may have won two regionals that year, but without a minibot deployment system we were there for fun and the Black Eyed Peas concert. (We actually ditched our tube claw to try to make a mechanism. Wasn't pretty.)

I'd venture a few things set minibots on their path:

1) The restrictive materials rules.
2) The packaging needs of a robot that also (usually) had to hang tubes up high too.
3) Because there was such a huge cost for a botched deployment, you had to get something in the air every match.
4) With the limited power of a Tetrix motor, anything extraneous added mass that then had to be powered upward.

I'd love to know what other teams had developed to the point of sticking on a pole, but I doubt any of them deviated far from the formula by the later weeks of events.

Bryce Clegg

16-12-2016, 21:57

Speaking of Andymark, here's a possible game hint: https://twitter.com/andymarkinc/status/809484665857986560

I saw a Rubik's Cube with red on one side, blue on another, and yellow on top. Return of coopertition?

Taggerun

16-12-2016, 22:25

I believe this was also around the time that the Rhino Drive was released. I think you're on to something.

Have to agree... I think the 4 year unusual game piece cycle is going to come true.
Can't wait to see,
Taggerun

P.S. The totes from 2015 do NOT count as unusual game pieces. They are more normal than a frisbee.

mrnoble

16-12-2016, 23:43

I'm far more interested to know what's in Lawrence of Canadia's hand in that video.

On my tiny phone screen it looked like a really small Omni wheel.

Mr V

17-12-2016, 04:35

I never heard of anyone treating motors with liquefied gasses in 2015. My understanding is that the 2011 minibot arms race was steeper than the 2015 grabbers. What surprised me when I went back and read about it was that no one (as far as I found) had implemented an ultra-simple CVT (continuously variable transmission) nor taken advantage of the ability of the minibot to have a mobile center of gravity.

Wait, what? Ultra-simple CVT? That can't be!
Actually, for a short, drag-race type run, there IS an ultra-simple CVT design. Don't think of doing this in gears, but in the diameter of the wheel. That is, start with a rather small wheel engaging the climb shaft, but with a bit of tread wrapped around it so that the wheel diameter increases (and therefore the effective gear ratio decreases) as the mini-bot completes its run. With proper design of the initial wheel shape, this transition can be continuous.

Mobile Center of Gravity? Whachu Talkin' 'bout, Willis? While it was a while back that I looked at the mini-bot rules, it seemed to me that a mini-bot was allowed to be about three times as tall as it actually had to be. So -- build the mini-bot to the shortest length possible, then stand it on a "rack" which raises it to the highest initial altitude allowed. As the robot climbs, the "rack" automatically climbs relative to the robot weight, until, at the top of the climb, the rack reaches the roof to signal contact, though the "real minibot" is still several inches lower.

With the minibot drag races it came down to reducing drag and weight as much as possible. Once FIRST said the transmissions could be modified it was quickly figured out how to remove stages, both to reduce the power loss in the transmission and allow smaller diameter wheels with less rotational inertia and overall weight. Then once FIRST clarified that you could toss the transmission that weight went out the window and the wheels became aluminum rod with some sort of tread, my team used the black surgical tubing turned inside out and carefully cleaned on 1/4" rod drilled and pressed onto the shaft. Then to get it in the power band off the line as quick as possible launch it horizontally so it wasn't fighting gravity and create a ramp so it hit the pole at peak power. Anything that added more than a couple of ounces beyond the battery, motors and the switch to turn it off at the top was at a big disadvantage.

Taggerun

17-12-2016, 09:30

On my tiny phone screen it looked like a really small Omni wheel.

It looked like a bushing to me.
Just a thought,
Taggerun

ollien

24-12-2016, 13:07

Emphasis mine.

We actually cut a bunch of samples over the summer in .025" increments to test this size, and found that .425" flat-to-flat is the right number for this specific profile and material combination. This number would change for a harder or thicker material, as well as a part with less holes in it.

-Nick

Sorry to revive a dead-ish thread, but over the holidays I'm training some new programmers with a kitbot we assembled before the break. I am happy to report that these do fit on .5" hex shafts very well, and without much effort!

http://i.imgur.com/5maN96f.png

Cothron Theiss

24-12-2016, 13:56

Sorry to revive a dead-ish thread, but over the holidays I'm training some new programmers with a kitbot we assembled before the break. I am happy to report that these do fit on .5" hex shafts very well, and without much effort!

http://i.imgur.com/5maN96f.png

Did you get to actually try it out on an intake? And thanks for this. I'll try and twist my team's arm and get them to buy some of these.

ollien

24-12-2016, 14:18

Did you get to actually try it out on an intake? And thanks for this. I'll try and twist my team's arm and get them to buy some of these.

I didn't. I don't actually have any hex shaft stock in my house (I live in an unusual household). That being said, I do have a couple of creative ideas using what I have on hand. I'll see if my programmers and I can whip something up when we meet.

R.C.

24-12-2016, 15:08

I didn't. I don't actually have any hex shaft stock in my house (I live in an unusual household). That being said, I do have a couple of creative ideas using what I have on hand. I'll see if my programmers and I can whip something up when we meet.

Is the overall width on that 1/2 or 1"? Thanks!

Bryce2471

24-12-2016, 15:11

Is the overall width on that 1/2 or 1"? Thanks!
Depth: 1/2"
This is my guess.

GeeTwo

24-12-2016, 15:27

Yes, I measured it at 1/2" thick.

And OBTW, you can dummy a 1/2" hex shaft with some 5/16" nuts and a bolt.

R.C.

24-12-2016, 17:45

This is my guess.

Downloaded the model last night and it was 1". Layout drawing and site say 1/2". Just wanted to verify with someone who has one. Thanks again.

ollien

24-12-2016, 18:15

Downloaded the model last night and it was 1". Layout drawing and site say 1/2". Just wanted to verify with someone who has one. Thanks again.

I'm out at the moment, but if memory serves correctly, it was thinner than 1". I'll double check when I'm home.

Cory

24-12-2016, 18:18

I'm curious to see how well these hold up at 5K RPM, and if they slip on the shaft or anything at that high of a speed.

I have similar concerns about the wheel slipping on the hex at high speeds but I think a pair of plates will keep the rubber from expanding near the hex.

There's no way this wheel is going to work well at 5000 rpm. You wouldn't even want to use it as a shooter wheel. It's too compliant and it will buckle (that is if it doesn't explode).

Stick with the McMaster wheels if you want a nice compliant shooter wheel that isn't going to deform like crazy/explode on you.

Cothron Theiss

24-12-2016, 18:25

There's no way this wheel is going to work well at 5000 rpm. You wouldn't even want to use it as a shooter wheel. It's too compliant and it will buckle (that is if it doesn't explode).

Stick with the McMaster wheels if you want a nice compliant shooter wheel that isn't going to deform like crazy/explode on you.

Ok, so does anyone have any recommendations for shooter wheels that aren't $30 each? Are Colsons the best cheap alternative?

dradel

24-12-2016, 18:31

We used 4" kop wheels last year on our shooter, were only $6.00 each if I remember right

Munchskull

24-12-2016, 19:38

R.C.

24-12-2016, 19:45

AdamHeard

24-12-2016, 20:01

Ok, so does anyone have any recommendations for shooter wheels that aren't $30 each? Are Colsons the best cheap alternative?

At a certain point you'll have to spend some money with some game objects.

Colsons worked for us in 2016, but in many other years didn't work nearly as well as more expensive options.

Considering the base price per axis in terms of speed control and motor, $30 per wheel really isn't that bad.

Knufire

24-12-2016, 20:03

Ok, so does anyone have any recommendations for shooter wheels that aren't $30 each? Are Colsons the best cheap alternative?

Man, what's the point of teaser videos if nobody looks closely at them. :yikes:

Richard Wallace

24-12-2016, 20:06

Considering the base price per axis in terms of speed control and motor, $30 per wheel really isn't that bad.

Yes, if you already know the wheel is going to do the job as expected.

$30/ea for trial and error can get expensive.

IndySam

24-12-2016, 20:10

Ok, so does anyone have any recommendations for shooter wheels that aren't $30 each? Are Colsons the best cheap alternative?

Depends on what you are shooting. I saw some pretty good shooters made from $5 AM stealth wheels this year.

Cothron Theiss

24-12-2016, 20:11

Man, what's the point of teaser videos if nobody looks closely at them. :yikes:

Are you referring to this wheel in the AndyMark teaser? That hex bore looks pretty small. Is that a wheel AndyMark just had laying around, or do you think that's an upcoming product?

ollien

24-12-2016, 20:12

Man, what's the point of teaser videos if nobody looks closely at them. :yikes:

Hm... What's that plastic bit in the middle of the wheel? I hope it has some way to interface with a hex shaft nicely.
http://i.imgur.com/V7aySEb.png

Cothron Theiss

24-12-2016, 20:18

Hm... What's that plastic bit in the middle of the wheel? I hope it has some way to interface with a hex shaft nicely.
http://i.imgur.com/V7aySEb.png

It looks to me like a .375 or even .25" hex bore.

pilleya

24-12-2016, 20:34

It looks to me like a .375 or even .25" hex bore.

Looks like it is the FTC bolt pattern so probably 6mm round or D bore with 6-32 bolts on a 16mm bolt circle. Most likely compatible with the new AM Nubs: http://www.andymark.com/AndyMark-Nub-p/am-nub.htm

Richard Wallace

24-12-2016, 20:45

Looks like it is the FTC bolt pattern so probably 6mm round or D bore with 6-32 bolts on a 16mm bolt circle. Most likely compatible with the new AM Nubs: http://www.andymark.com/AndyMark-Nub-p/am-nub.htm
I think you are right. That is likely an 8 mm (5/16") hex bore, so a nub would pilot in it.

ollien

24-12-2016, 20:51

I think you are right. That is likely an 8 mm (5/16") hex bore, so a nub would pilot in it.

Doesn't look like there's a nice way to adapt this to hex though :/

Richard Wallace

24-12-2016, 21:08

Doesn't look like there's a nice way to adapt this to hex though :/

What "this" are you referring to?

I was looking at the hex bore in the white plastic hub. It appears to be 8 mm or 5/16" across the flats. If so, it will pilot on a nub's 8 mm boss. It also seems to have the 16 mm circle pattern of four holes that would suit a #6 screw.

So you could drive the wheel using 6 mm shaft through a nub, or you could drive it directly using 8 mm (5/16") hex shaft.

Or were you thinking about 3/8" hex?

pilleya

24-12-2016, 21:08

Doesn't look like there's a nice way to adapt this to hex though :/

Definitely not enough meat in the center to be able broach out to 1/2inch hex. The holes on the 16mm bolt circle would also clash with the points of the shaft.

Surely if you need to adapt it to use it, you might as well just make a hub from scratch.

Lireal

24-12-2016, 21:09

Doesn't look like there's a nice way to adapt this to hex though :/

It looks like there should be enough clearance to broach it.

pilleya

24-12-2016, 21:21

It looks like there should be enough clearance to broach it.

It would end up looking like this if you tried to broach it to 1/2inch hex.

http://i.imgur.com/bWaM6eE.png

Cory

24-12-2016, 21:40

It would end up looking like this if you tried to broach it to 1/2inch hex.

http://i.imgur.com/bWaM6eE.png
That would work just fine.

ollien

24-12-2016, 22:33

Downloaded the model last night and it was 1". Layout drawing and site say 1/2". Just wanted to verify with someone who has one. Thanks again.

Definitely half inch.
http://i.imgur.com/RR0o5pn.jpg

bdaroz

24-12-2016, 22:36

Woah.... might want to resize that, or make it a link...

Billfred

24-12-2016, 22:41

Downloaded the model last night and it was 1". Layout drawing and site say 1/2". Just wanted to verify with someone who has one. Thanks again.

Checked with our engineers--we goofed on that. Updated CAD will go out next week.

ollien

24-12-2016, 22:53

Checked with our engineers--we goofed on that. Updated CAD will go out next week.

Engineers are available on Christmas Eve? Jeez!

bdaroz

25-12-2016, 11:26

Checked with our engineers--we goofed on that. Updated CAD will go out next week.

Come on... We know they didn't goof. They over designed. :D :D :D

Richard Wallace

25-12-2016, 13:50

There is a very old principle of engineering at work here:

When the print does not match the part, change the print. The part is always right.

IndySam

25-12-2016, 14:58

There is a very old principle of engineering at work here:

When the print does not match the part, change the print. The part is always right.

As builts.

grem110

25-12-2016, 15:07

Yikes! These are already gone.

Any idea when they'll be back in stock?

WSiggs

25-12-2016, 20:36

Man, what's the point of teaser videos if nobody looks closely at them. :yikes:

Is there something in the FRC teaser we have all been missing? Something in the AM twitter "teaser"? Is this whole discussion of shooters useless because there's something obvious we're missing?

Knufire

25-12-2016, 20:43

Is there something in the FRC teaser we have all been missing? Something in the AM twitter "teaser"? Is this whole discussion of shooters useless because there's something obvious we're missing?

Nah, I was just referring to the wheel that looked very similar to the McMaster sure-grip wheels that were the topic of conversation at the time.

ratdude747

27-12-2016, 00:47

There is a very old principle of engineering at work here:

When the print does not match the part, change the print. The part is always right.

(somewhat off-topic: )

Or at my company, if the drawing doesn't match the CAD, change the drawing as CAD is master (unless the marketing department tosses back one's plans to make said part because "the CAD is wrong" :mad: ).

Sadly in manufacturing as supplier (in my case, to Toyota), that old principle doesn't fly for parts being sold to a customer. If you're not meeting the spec, too bad, no good. We've had to toss hundreds of trial parts over changed drawings and related sillyness... but they're the customer, and they're always (usually) right.

Billfred

27-12-2016, 09:21

Engineers are available on Christmas Eve? Jeez!

Engineers? Where?! (http://moore.sc.edu/)

;)

Richard Wallace

27-12-2016, 10:28

Engineers? Where?! (http://moore.sc.edu/)

;)Thank goodness there are people in this world who refuse to let physics and calculus ruin a good story.

Billfred

27-12-2016, 17:13

Thank goodness there are people in this world who refuse to let physics and calculus ruin a good story.

Thank goodness there are people in this world who refuse to let 2" wheels have all the fun.

http://www.andymark.com/product-p/am-3480_60.htm
http://www.andymark.com/product-p/am-3480_50.htm

(CAD coming soon on the website--we were too excited to let these sit on the shelf.)

marshall

27-12-2016, 19:57

Thank goodness there are people in this world who refuse to let 2" wheels have all the fun.

http://www.andymark.com/product-p/am-3480_60.htm
http://www.andymark.com/product-p/am-3480_50.htm

(CAD coming soon on the website--we were too excited to let these sit on the shelf.)

https://www.youtube.com/watch?v=85cL1HisrNc

Ari423

27-12-2016, 21:22

https://www.youtube.com/watch?v=85cL1HisrNc

I'd buy that for $8 :D

Thank you AndyMark for another great COTS product!

RoboChair

27-12-2016, 22:22

Any tips on how to adapt them for hex shaft?

I think the bore is 1", in the past we just made an aluminum hub that was .001 or so oversize and just pressed it in. You can probably take a colson hub or versahub and shave it down to size if you don't want to make a hub from scratch.

We had good success with Delrin hubs in our shooter wheels this year. Went with around 0.004" over size press, some may have been more like 6 >_>. We have a big arbor press and I may have gotten a little carried away with the interference #SorryNotSorry.

Lil' Lavery

27-12-2016, 22:32

Ok, so does anyone have any recommendations for shooter wheels that aren't $30 each? Are Colsons the best cheap alternative?

http://www.banebots.com/category/WHEELSHUBS.html

Much lower durometer than Colson wheels, but not as compliant as the teardrop rollers from McMaster. Prices range from $2.50-$5.00ea (not counting hubs, which are only necessary for applications other than 0.500hex). 4 durometer options and numerous size options.

Munchskull

28-12-2016, 00:13

AlexanderLuke

28-12-2016, 03:00

Ari423

28-12-2016, 05:49

Beyond the 2" sizing, this one has a black color option too! ;)

*redesigns robot to match color scheme*

Andy Baker

28-12-2016, 08:30

Hope that you will have enough stock of all four of the wheels.

Keeping stock for plastic molded AndyMark products is not a problem. Our mold shop is about 5 miles away, and they provide fast service. We don't have to keep gobs in stock, due to quick production runs.

We may run out of stock for a molded item for a few days, but it's always back in stock soon.

This is reason #3480 we don't buy molded parts from distant lands.

Sincerely,
Andy B.

marshall

28-12-2016, 08:40

Keeping stock for plastic molded AndyMark products is not a problem. Our mold shop is about 5 miles away, and they provide fast service. We don't have to keep gobs in stock, due to quick production runs.

We may run out of stock for a molded item for a few days, but it's always back in stock soon.

This is reason #3480 we don't buy molded parts from distant lands.

Sincerely,
Andy B.

Fun fact, at size 12 single spaced Times New Roman with 1 inch margins, you can get ~46 lines on a page so the AndyMark handbook for buying molded parts must be at least 76 pages assuming each reason is at least a single line.

I'm guessing Andy uses that handbook to keep his desk level. ;)

Billfred

28-12-2016, 09:21

Fun fact, at size 12 single spaced Times New Roman with 1 inch margins, you can get ~46 lines on a page so the AndyMark handbook for buying molded parts must be at least 76 pages assuming each reason is at least a single line.

I'm guessing Andy uses that handbook to keep his desk level. ;)

/r/theydidthemath

Also, the entire AndyMark employee handbook is only 15 pages. (I just checked.) Aside from FIRST's game manuals, I can't think of any company-guiding documentation that comes in at 50+ pages. ;)

Also, you think Baker can't build a level desk?

marshall

28-12-2016, 23:03

/r/theydidthemath

Also, the entire AndyMark employee handbook is only 15 pages. (I just checked.) Aside from FIRST's game manuals, I can't think of any company-guiding documentation that comes in at 50+ pages. ;)

Also, you think Baker can't build a level desk?

LOL. Now people are going to be looking at that desk for teasers. :)

Baker can't use you to defend his honor! He better provide a video using a NavX to show how level that desk is without a stack of paperwork under those wheels!

GeeTwo

29-12-2016, 00:26

Baker can't use you to defend his honor! He better provide a video using a NavX to show how level that desk is without a stack of paperwork under those wheels!

Marshall, don't spit into the wind. Even I can cut and drill pieces off site for an outdoor workbench to be used from a boardwalk and have it come out level at the right altitude (and be more solid than the boardwalk). Baker's so got an indoor desk that it's not funny.

marshall

29-12-2016, 10:32

Marshall, don't spit into the wind. Even I can cut and drill pieces off site for an outdoor workbench to be used from a boardwalk and have it come out level at the right altitude (and be more solid than the boardwalk). Baker's so got an indoor desk that it's not funny.

That desk has wheels and is clearly meant to be rolled outdoors into the rain. #WaterGameConfirmed

At this point I'm just trying to see how absurd I can make this thread prior to kickoff. I'm waiting on Nate to drop a memey gif in here next.

nathannfm

29-12-2016, 14:27

I'm curious to see how well these hold up at 5K RPM, and if they slip on the shaft or anything at that high of a speed.
There's no way this wheel is going to work well at 5000 rpm. You wouldn't even want to use it as a shooter wheel. It's too compliant and it will buckle (that is if it doesn't explode).

We are rating the 2 inch wheels at 6000 RPM, or "don't go any faster than direct drive off a Mini CIM" below that speed it will not significantly expand (~1mm) but above that speed it becomes unstable and different parts expand at different rates. Interestingly, even at ludicrous speeds (+10,000 RPM) the hex will stay aligned if nothing touches it. When subjected to hard impacts at any speed the hex will slip (game piece, compression, and RPM dependent) but for the application it is designed for, that isn't really a problem. Even if it were used as an FTC shooter wheel for this years game it would probably function pretty well since the balls are light and only have to go a few feet. I can also say with confidence that it will not explode below 6000 RPM. I am unable to do any damage to it by hand, and it took putting pins between the spokes and stretching it by mechanical means so that the pins were over 13 inches apart before it tore.

Also, they are back in stock, so BUY BUY BUY!

Stick with the McMaster wheels if you want a nice compliant shooter wheel that isn't going to deform like crazy/explode on you.
Or one of our even newer 4" compliant wheels rated to Over 9000 (https://www.youtube.com/watch?v=SiMHTK15Pik) RPM :D
Also an expansion vs RPM table should be up on the site soon (along with more stock :P )

Billfred

29-12-2016, 14:36

Or one of our even newer 4" compliant wheels rated to Over 9000 (https://www.youtube.com/watch?v=SiMHTK15Pik) RPM :D
Also an expansion vs RPM table should be up on the site soon (along with more stock :P )

Citation (http://conta.cc/2iioK5s), while the page is being updated.

Headline GIF:

http://i.imgur.com/qLQQiXQ.gif

AdamHeard

29-12-2016, 17:52

Citation (http://conta.cc/2iioK5s), while the page is being updated.

Headline GIF:

http://i.imgur.com/qLQQiXQ.gif

That number seems DANGEROUSLY high to tell general case to team's at large.

With compression and a high number of shots, I'd be very concerned running at that number.

Lireal

29-12-2016, 18:10

http://i.imgur.com/qLQQiXQ.gif

What is on the paper that says product teaser?

WSiggs

29-12-2016, 18:32

What is on the paper that says product teaser?

A product teaser.

In all seriousness though it looks kindof like someone took apart a motor (http://www.andymark.com/product-p/am-2938.htm) and spread it out.

Billfred

29-12-2016, 20:36

That number seems DANGEROUSLY high to tell general case to team's at large.

With compression and a high number of shots, I'd be very concerned running at that number.We tested them pretty thoroughly with old FTC balls, including a 1" practice golf ball that has basically zero squish of its own, and the engineers derated it to a number they were confident in. Obviously, anyone running any crazy-high-speed system should inspect those wheels early and often.

Nathan did the actual testing, and he may be able to provide more detail.

What is on the paper that says product teaser?

A product that we want to tease. ;)

bdaroz

29-12-2016, 21:18

A product that we want to tease. ;)

And on the back of the paper is the 2018 water game field element CAD drawing.... come on, we know... :)

AdamHeard

29-12-2016, 21:59

We tested them pretty thoroughly with old FTC balls, including a 1" practice golf ball that has basically zero squish of its own, and the engineers derated it to a number they were confident in. Obviously, anyone running any crazy-high-speed system should inspect those wheels early and often.

Nathan did the actual testing, and he may be able to provide more detail.

A product that we want to tease. ;)

As of right now the site still shows 9001 RPM.

What is pretty thoroughly? 1000 shots? 10000?

I know some of the teams running the fairlane teardrop wheels in 2013 replaced them a few times over the season due to tears propagating.

Lil' Lavery

29-12-2016, 22:06

snoman

29-12-2016, 22:18

Has any one tried 3d printing there own wheel of this type? I have a spool of a flexible material I have been wanting to try out.
https://ninjatek.com/products/filaments/ninjaflex/

RoboChair

29-12-2016, 22:26

My only comment with the "9001" rating is that carrying things to that amount of significant figures implies strong confidence in that specific number. While I certainly get the "over 9000" meme, many FIRST mentors (especially those over the age of 35 or so) aren't going to, and may interpret that 9001 figure to be a more scientifically approached limit given the specificity to 4 sig figs.

You are assuming that the zeroes are not significant figures already. Zeros can be significant.

Tell a machinist to make a part with a dimension of 1.00000" and see how hard they hit you. Whereas 1.00" and they won't bat an eye.

Lil' Lavery

29-12-2016, 22:28

You are assuming that the zeroes are not significant figures already. Zeros can be significant.

Tell a machinist to make a part with a dimension of 1.00000" and see how hard they hit you. Whereas 1.00" and they won't bat an eye.

Oh, I agree. But these aren't zeroes beyond the decimal point. The zeroes in "9000" could be significant, or they could be placeholders for the proper unit value. However, the zeroes in "9001" are definitely significant.

Richard Wallace

29-12-2016, 22:34

My simple minded calculation of stress on the 4" wheel in question:

The wheel's outer section ("rim") is about 5 mm thick, 25 mm wide, and 320 mm long. Its volume is about 40 cc. Assume its density is about 1.5 g/cc so its mass is about 60 gram or 0.13 lb.

At 9000 rev/min, the "rim" has ~4400g centripetal acceleration, or ~570 lb. centripetal load. This stress acts on the spokes and is divided equally among them, at least until the wheel loses symmetry by deforming. So each spoke takes one-eleventh of the centripetal load, or 52 lb. That spoke stress is born by the same cross-section as the rim, or about 0.2 square inch, so the material must withstand ~ 260 PSI.

Neoprene yields somewhere above 500 PSI. How much higher? Probably depends on the durometer.

Please, will a real mechanical engineer check this for me? I know it ignores stress-rise in corners, for example. Those will be more significant for the AM design than for the tear-drop spoke flex-grip rollers we've bought from McMaster-Carr.