28-06-2010 11:21

Chris is me

Re: pic: 2011 Drive Prototype

A few questions:

1. Are the cam tensioners any different than the standard 254/968 style? Based on their mount location it doesn't look any different, in which case there's not much point to keeping them "a secret".

2. Did you remember to set material properties on the compressor and CIMs? Right now you have 11 pounds in CIMs and 4.3 pounds in the compressor, which means everything else shown weighs only ~18 pounds?

3. What are your transmissions made of that you get them down to 1 pound? I'm curious. I've basically found through CAD that the only way to get a shifter in a similar application down to 1.01 pound would be to switch to suboptimal (as I've been told) parts, or like 1/8th delrin or something ridiculous like that. How'd you get this transmission to 1 pound?

If everything's as it seems and you made a 34 pound chassis that does all that, good job!

28-06-2010 12:09

ttldomination

Re: pic: 2011 Drive Prototype

That's some smexy stuff.

Just a quick question about how the bearing blocks are mounted? I'm not exactly sure how that works.

- Sunny

28-06-2010 12:48

548swimmer

Re: pic: 2011 Drive Prototype

It looks like the frame may be a bit unstable in the short direction. Would it be possible to add some angled supports like you have in the long direction to strengthen the frame?

28-06-2010 13:39

Akash Rastogi

Re: pic: 2011 Drive Prototype

That frame should be perfectly rigid and structurally sound. Its fine as is.

.

28-06-2010 13:40

548swimmer

Re: pic: 2011 Drive Prototype

Why are no angle supports needed for the short direction?

28-06-2010 13:57

Chris is me

Re: pic: 2011 Drive Prototype

There's a belly pan spanning the width of the robot. Generally such pans are used as structural members of the chassis (see 233/254's frames)

28-06-2010 14:06

548swimmer

Re: pic: 2011 Drive Prototype

Maybe I didn't word the question clearly. I was referencing the upper frame's supports, not the lower portion of the chassis.

28-06-2010 14:17

Ether

Re: pic: 2011 Drive Prototype

If there are going to be any large sideways forces acting on the upper frame in the lateral direction (like a "reverse curl" lifter) then some triangulation of the frame in that direction might be warranted.

28-06-2010 15:05

Re: pic: 2011 Drive Prototype

Looks like a nice design. A prototype is a functioning physical mockup or first run mechanism. For reference:

I quite like your modeling work, keep practicing! My suggestions for the design:
-You probably don't need the superstructure.
-Have you taken into account materials? Depending on what thicknesses and alloys you're planning on using, you might be able to save some weight here and there.
-How thick is your belly pan? It seems rather thick. You should be able to go pretty thin, ie .090 or .040 while still maintaining plenty of strength if you're securing it in place correctly.
-"Secret CAM system", huh? Now I'm curious!

28-06-2010 15:57

Akash Rastogi

Re: pic: 2011 Drive Prototype

Yes, you did not word it correctly. But, since superstructures are game-based anyway, you usually don't see many teams using pre-designed superstructures, as is. However, it is a good idea to always keep mounting methods in mind, such as the hole patterns in kit frame rails and 973's frame rails.

.

Great design work, Marcus. You definitely have some nice skills.

28-06-2010 16:18

MWB

Re: pic: 2011 Drive Prototype

Well the cams method of turning are different, not the actual block.

Yes all the materials are set. The reason that it is so light is because the upper-structure is made of 1/16in aluminum

They are made of 1/4in Delrin and 7075 Aluminum

28-06-2010 16:20

MWB

Re: pic: 2011 Drive Prototype

They slide inside of of a square cutout, while a cam (involute of a circle) with lots of tiny ridges sort of ratchets into place. the ridges fit onto the radius of the bearing block. PM Cory if you want to get the total lowdown.

28-06-2010 16:24

MWB

Re: pic: 2011 Drive Prototype

Thanks for the the info! Well the upper-structure is 1/16in. The belly pan could be lighter, but right now it only weighs about 2lbs so if less weight is needed i will change it.

The secret CAM system does not necessarily lie in the blocks or the actual cam, it lies within the method in which the CAMS are turned... Think about it

28-06-2010 16:25

JamesCH95

Re: pic: 2011 Drive Prototype

How are you putting the frame together? Bolts and brackets? Welding? The concept is good (though you should have some additional triangulation as some have mentioned). You just need a little more detailing for it to be 100%.

28-06-2010 16:26

MWB

Re: pic: 2011 Drive Prototype

Thanks Akash

28-06-2010 16:29

Re: pic: 2011 Drive Prototype

Be wary, welding 1/8" wall to 1/16" wall can be entertaining. Are you planning on having a welder do it for you, or will a student be doing the welding? 1/16" wall is veeeeery thin, and can splatter and deform under the hands of a less experienced welder.

28-06-2010 16:30

MWB

Re: pic: 2011 Drive Prototype

Also if anyone hasn't noticed, there are two different heat sinks on the CIMS. Does anyone have any comments and/or preferences.

28-06-2010 16:31

Re: pic: 2011 Drive Prototype

I doubt you'll need much heat work on the CIM's unless you're REALLY overworking them. We never had any heat issues on any of our robots.

28-06-2010 16:40

sgreco

Re: pic: 2011 Drive Prototype

I would agree with your warning. My team bolted our chassis last year, but in 2009 we had a fairly complex chassis of a mix between 1/16 and 1/8, wall tubing. If a professional welder is doing it you have nothing to worry about, but if he's not you have a lot to worry about. I tend to be an aluminum type of guy, but if you don't have an experienced welder, then you could go with steel, and shrink the wall sizes significantly. My team has a mentor who, among othert things, is a very good welder, and we had no problems with our frame, but we have let kids weld on prototypes and such that weren't on the real robot, and it didn't turn out so well.

I like where the model is headed, keep up the good work.

28-06-2010 16:42

MWB

Re: pic: 2011 Drive Prototype

well in the picture you cant see that the 1/16 tubing has a stud sticking inside of it which is welded to the 1/8. it will be held in with a pin.

I will be doing the welding, but i have done 1/16 before so it wont be too hard.

28-06-2010 16:45

MWB

Re: pic: 2011 Drive Prototype

if i am not able to do it, we have a mentor that is an experienced welder.

28-06-2010 16:50

sgreco

Re: pic: 2011 Drive Prototype

I wouldn't worry about heat, I can only speak from personal experiences, but my team has never come close to burning out a CIM. We have had some issues with the Denso motors though. If a CIM overheats, it will likely be a result of multiple matches, and not one tough match. My team leaves a can of Dust-Off on our cart. It's very cold and a quick spray will cool off your CIMS. It is also made for electronic devices, so it can't do damage if it gets into any part of you circuitry. You have time to cool them between matches, even in the finals, and this way you don't have to worry about one extra part on the robot (or fraction of a pound, which we all know means a lot when you go to get inspected).

28-06-2010 16:52

JamesCH95

Re: pic: 2011 Drive Prototype

1/16th isn't bad, just remember that pure tungsten is pure cr*p and 50ar/50he shielding gas is worth its weight in gold. These two things make welding aluminum much much much easier.

Also, I swear by this guy's advice. He really knows his stuff and is super responsive to emails.

Good luck!

28-06-2010 17:20

Cory

Re: pic: 2011 Drive Prototype

We put cross members even when using the "belly pan" design.

For the original poster: How do you intend to manufacture your gears? I'm guessing our 2007 robot was the inspiration for this design based on some of the aspects you've chosen to incorporate. If you've read much about that robot you'll have seen that everyone involved with the robot agrees that it's simply not worth the time and cost to make aluminum gears, for the ~2-2.5 lb weight savings.

Additionally we have moved away from delrin in the past two years. It flexes too much and isn't as durable as aluminum. If you have access to a waterjet it becomes very easy to make pocketed .250" aluminum gearbox plates which will be comparable in weight to .250 delrin but much more rigid. If you have access to a CNC mill, which I assume you do based on your design, it's a little more work, but still fairly simple.

If you intend to make this as a prototype, you should probably understand the basics of how the design actually works. If you're just copying it and drawing it in CAD with no understanding of why things are done the way they are, then what value is that bringing to your team?

28-06-2010 17:37

MWB

Re: pic: 2011 Drive Prototype

Well i just thought that it would be cool to lighten our shifters, then i saw yours and incorporated some of those features into my design.

Delrin is an easier material for us to mill because we do not have access to a vmc yet, just a prototrak machine.

I do understand how the design works, just i did not want to give him wrong information so that i do not confuse him. PM me so that i can explain.

28-06-2010 18:14

Travis Covington

Re: pic: 2011 Drive Prototype

Why the secrecy with the tensioning method? I have to assume that most all of your design inspiration exists because of a lack of secrecy and the willingness of others to share ideas and to develop understanding.

28-06-2010 18:19

MWB

Re: pic: 2011 Drive Prototype

Well we are happy to share it during the build season, but not before. And anyways its only a prototype or a design. So we might not even end up doing the design.

28-06-2010 20:21

Chris is me

Re: pic: 2011 Drive Prototype

You shouldn't need either, and if I correctly understand how the CIMs dissipate heat from what I've been told by people smarter than me, they won't make much of a difference. Your CIMs shouldn't be burning hot at the end of a 2 minute match; if they are, you probably have bigger problems with drawing tons of current and draining right through batteries.

28-06-2010 20:23

MWB

Re: pic: 2011 Drive Prototype

OK, thanks for all the help. ill remove them right now.

28-06-2010 22:16

Brandon Holley

Re: pic: 2011 Drive Prototype

We make 100% of all our CNC milled parts on a ProtoTrak. We have absolutely no problems cutting any kind of aluminum. What sort of problems are you having?


Also, about the tensioning system...it seems extremely similar to 254s, why are you keeping it secret?

-Brando

28-06-2010 22:55

MWB

Re: pic: 2011 Drive Prototype

Its the programming of pocketing that is hard, not the actual cutting.

Well its the way the cams are turned, not the actual system.

29-06-2010 03:11

Cory

Re: pic: 2011 Drive Prototype

What CAM package are you using?

29-06-2010 03:43

sdcantrell56

Re: pic: 2011 Drive Prototype

This looks to me like a redrawing of a 254/968 robot. WHile good for developing CAD skills, it is only probably 10% of the actual design process. The secrecy about the cam is particularly bizarre. I can't imagine anything you have done to drastically change the already mentioned cam method of tensioning that you wouldn't even know about without the free sharing that 254/968 participate in.

It's a bit disheartening to see all this "design" and "prototype" being claimed as your own, when it is clearly a near carbon copy of an already existing design although not even the most recent version of the drivetrain that they use.

I am a bit worried about the amount of people posting "west coast" drive "designs" lately that clearly dont understand the actual intricacies involved with the design and instead of taking the time to figure out the chain runs, bearing blocks, tensioning, etc, spend the time focusing on making "cool" renders. When it comes to how the robot functions, the quality of the render will have absolutely no correlation.

29-06-2010 16:18

MWB

Re: pic: 2011 Drive Prototype

Sir in no way is this a copy of 254's robots, it may look similar as a lot of robots made of 2x1 and 1x1 do. but all the dimensions and shapes are way different than 254's. The person that showed me how to make a cam isn't even from 254. Also, i did spend time mapping the chain runs and making sure the bearing blocks worked correctly. And anyways the render took me 5 min to make and less time to setup, the only reason i put a render up is so that there weren't a whole bunch of black lines and little colors.

29-06-2010 16:19

MWB

Re: pic: 2011 Drive Prototype

The machines cam is an old style acer not sure how to describe it, but you plug numbers into the machine and it goes to those points.

29-06-2010 21:22

Brandon Holley

Re: pic: 2011 Drive Prototype

Well cmon then!! Your machine is more than capable of doing it, so why sell yourself short?? Just about any CAM system will allow you to program the pockets with relative ease.

-Brando

29-06-2010 22:18

MWB

Re: pic: 2011 Drive Prototype

i guess that its not really worth the time, but i will think about it

30-06-2010 04:26

Cory

Re: pic: 2011 Drive Prototype

Neither is making aluminum gears

If you don't feel it's worth the time and effort it takes to put some pockets in a gearbox plate, I really don't think you're going to want to go to the extreme level of effort it takes to make that happen.

30-06-2010 16:16

MWB

Re: pic: 2011 Drive Prototype

This is true... i guess we will buy the gears from AM then put them on weightwatchers.

Also can you or Nick Eyre please show me how to pocket the plates like 254 does it Cory? because the only pocketing that i know how to do is by cutting triangles.

01-07-2010 13:00

Triple B

Re: pic: 2011 Drive Prototype

nice chassis, i like it
mike d

01-07-2010 13:08

Akash Rastogi

Re: pic: 2011 Drive Prototype

Just wondering, by any chance were RC or Eugene Fang helping you out with this?

01-07-2010 16:37

MWB

Re: pic: 2011 Drive Prototype

Eugene explained what WCD was and RC explained how the cam lock tensioning system worked... Oh yeah and RC told me how much my renders sucked haha.

01-07-2010 17:07

AdamHeard

Re: pic: 2011 Drive Prototype

To deny this is a copy of 254's (and 60's and so on) design is simply disrespectful.

There is nothing wrong with copying someones design and using them for inspiration; It's only wrong to deny it.

01-07-2010 17:45

MWB

Re: pic: 2011 Drive Prototype

I meant that it is not a "Carbon Copy" as he called it, it is a copy of the concept but not the total design.

01-07-2010 17:54

Re: pic: 2011 Drive Prototype

Hm. Really?
- Cam actuated tensioners? Check.
- Self locking style cams? Check.
- 2x1 frame members surrounding semi-elliptical bearing blocks? Check.
- External cantilevered wheels? Check.
- Center wheel direct driven? Check.
- Two speed custom gearbox? Check.
- Belly pan for electronics, cut on a waterjet/laser? Check.
- Welded sheet battery box? Check.

I could keep going on. Are you SURE it's not a copy of the 254/968 system?

01-07-2010 18:08

MWB

Re: pic: 2011 Drive Prototype

Ok #1 Its the concept that i copied, not the design. there are many differences in my design versus 254's. While the design was heavily inspired by 254, it is not a copy. What i did was i took the concept and adapted it to suit my own needs. The Belly pan's cut out pieces are different sizes, the bearing blocks are different dimensions, work a little differently and have smaller radiuses... Pretty much all the things that you listed were concepts not total designs. Anyways who hasn't used a 254 concept in their career in FIRST.

01-07-2010 18:22

Cory

Re: pic: 2011 Drive Prototype

That would be a 233 design cue. Far too many people see our robots from the last 2 years and think it's our idea. Just one of the many we've borrowed from other great teams over the years.

01-07-2010 18:25

MWB

Re: pic: 2011 Drive Prototype

Don't you even use 233's Water jet? So technically you're borrowing their machines too!

01-07-2010 18:31

Eugene Fang

Re: pic: 2011 Drive Prototype

Having talked to Marcus and seen many of his design iterations before this post, I know he understands many of the intricacies and benefits of a WCD design. True, there have been many posts on CD lately of "pretty renders" of chassis designs that seem to have very little thought put into working out any of the details, but I can assure you this is not one of them.

Sorry Marcus, I will have to agree that this design is heavily inspired by 254/968, and you should own up to it. But to everyone else, while Marcus has not created an entirely new chassis design, I am glad that he has taken the time to actually analyze 254/968's design and ask himself why certain things are done the way they are (for example, why the cams are tensioned counterclockwise as opposed to clockwise) and do proper drive train calculations.

I think that a perfect place to start is to look at examples from great teams like 254/968 and try to figure out the thought process that led them to their final design. Only then can someone start to be innovative. And as a first year FRCer, I think Marcus is doing a great job at that.

Now let's get back to some constructive criticism.

01-07-2010 18:45

Re: pic: 2011 Drive Prototype

Good to know. We've done some kind of belly pan since 2005, but never has it been waterjetted to such accuracy.

01-07-2010 18:49

Cory

Re: pic: 2011 Drive Prototype

That's correct. 233 has waterjetted numerous parts for us the last two years and we help them out by making things for them whenever possible.

01-07-2010 18:53

MWB

Re: pic: 2011 Drive Prototype

Like wheels for their practice bot... right?

01-07-2010 18:55

Cory

Re: pic: 2011 Drive Prototype

We manufactured a number of drivetrain components for them this year.

01-07-2010 20:32

MWB

Re: pic: 2011 Drive Prototype

Why was that? Was it because you used similar components and you already had the g-code written. So it was faster and more efficient to do them all at once?

01-07-2010 22:40

548swimmer

Re: pic: 2011 Drive Prototype

You seem to be missing the point. What style of bearing block you use or how big the cutouts are doesn't matter in the grand scheme of the design. If I took this design, changed around what type of bearing blocks were used, changed the shape of the lightening holes in the belly pan, and used a different shaft size, would it be a different design?

01-07-2010 22:46

MWB

Re: pic: 2011 Drive Prototype

Yes, it would be a different design. I never said that i didn't get inspiration from 254 or that it wasn't their concept i just meant that it's my version of their design.

01-07-2010 22:53

548swimmer

Re: pic: 2011 Drive Prototype

Alright, I would personally view it (and it appears several others do as well) as the same design. I accept that you think of it as a different design though.

01-07-2010 23:05

EricH

Re: pic: 2011 Drive Prototype

Grandfather's axe is handed down from generation to generation. Every now and again, the head or the handle is replaced due to normal wear and tear of use, with a slightly differently shaped head or handle. At what point does it stop being Grandfather's axe?

I'm not going to say that you didn't get inspiration from 254. I don't think anyone ever did say that. What got people annoyed was that you made mostly cosmetic changes, and then appeared to claim that because you made some small changes, it was your design, not 254's. Again, this is simply the impression I got. See the Grandfather's axe answer area above--I think we're on two different answers here.

BTW, 330 has yet to use a WCD design. 6WD? Yes. Shifting? Yes. Direct drive to the center wheel? I can't say I remember one--possibly in 2009, which wasn't a WCD design any way you look at it. Cantilevered? Nope, I can't think of a single 330 robot using a cantilevered wheel. Battery box? A couple of times, but I don't remember materials, etc. Belly pan? Well, we do use a plywood base for strength and mounting stuff... But no tensioners of the cam style, let alone embedded in the frame rails. Elements, we've used. Design, we haven't.

02-07-2010 02:48

Cory

Re: pic: 2011 Drive Prototype

For a number of reasons. We had wanted to do some sort of collaboration with them on a summer project for years but had never been organized enough to make it happen. We both were going to make similar drivetrains and we were already making about 8 sets of everything so it didn't make it any more difficult for us to make 10 of the components common to both teams.

02-07-2010 10:56

Triple B

Re: pic: 2011 Drive Prototype

and cause 233 is just plain lazy

02-07-2010 13:34

Mike Soukup

Re: pic: 2011 Drive Prototype

To all of you pontificating that Marcus copied the design of 254 & 968, I ask who cares? We have a student using Inventor to design a drive base instead of wasting his time playing video games. I see nothing wrong with that.

I find all the recent berating replies to student designed components counter-productive. Shouldn't we be encouraging exploration instead of repeatedly beating it with a stick? Spend some time giving constructive feedback instead.

02-07-2010 14:06

JamesCH95

Re: pic: 2011 Drive Prototype

^^ Exactly. I'm sure many chain-drive 6wd designs look a lot like Team 95's robot Archimedes from 1998 which had a dropped-center 6WD. I'm sure many omni-wheel drives look similar to 95's 1999 robot Mac. It's likely that these designs looked an awful lot like ones that came before them.

It's very rare that designs change radically and immediately. Look at the evolution of cars, or bicycles, or...

02-07-2010 14:45

Chris is me

Re: pic: 2011 Drive Prototype

I don't think anyone minded the inspiration from 254 and 233, until he claimed it was an original design. Regardless, you have a perfectly valid point.

02-07-2010 16:44

gallo26

Re: pic: 2011 Drive Prototype

I don't get the problem here. He's taking the time to design something during the off-season to take a chance and inspire his team to use something they never have before. FIRST is all about teams sharing ideas and collaborating. If there was a team against that theory I'm positive they would not be a part of it. James is right in saying its VERY rare to see anything original anymore.

Copying someone's design is taking their work, piece by piece, and calling it your own. BUT, if you take someone else's design and modify it to accommodate any changes you might like, it becomes an original design. The Car, it has 4 wheels, a power source, steering wheel, and seats. It's been done. Companies design new cars everyday. Same concept. same core pieces, but small parts are modified. They patent that design and call it an original design.

I should be able to say that Krab Drive was designed completely by Team 79. But look through the history of FIRST, it's been done. But what we DID do is take the swerve drive, modify the modules to what we found best, fit the design into a chassis we can work with, and built a robot with it. This became an original design that no one else in the world has. If you can show me another robot that is EXACTLY, piece for piece, the same, I'll take back everything I have said.

Chief Delphi has always been a place where students and mentors can come together and share experiences, share designs, and communicate on how to better their knowledge. Lately I have found it to be filled with harsh critical comments which have nothing to do with the design themselves. It shocks me to know that people have started to use CD as a way to bring people down instead of building them up. It seems that we have forgotten the saying "If you have nothing nice to say, say nothing at all"

With all of that aside, I would like to commend you on such a design. It's very well put together, and I love the idea of having an easy-to-use chain tensioner. This is a very nice building block to many robot designs you could invent in the future. Continue the great work! If you follow through with this kind of design as an off-season test platform, I would love to see how it turns out.

Bryan Gallo