24-05-2010 20:20

Re: pic: Schreiber Take on West Coast Drive

If this were reddit, I'd have upvoted this.

24-05-2010 20:24

Dave McLaughlin

Re: pic: Schreiber Take on West Coast Drive

What CAD program did you use to render this?

24-05-2010 20:26

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

NAD 2010

24-05-2010 20:36

rtfgnow

Re: pic: Schreiber Take on West Coast Drive

Have you preformed stress analysis on that frame?

24-05-2010 20:36

ttldomination

Re: pic: Schreiber Take on West Coast Drive

Very concise drawing. Lacks a little finesse, maybe try cardstock later.

Just a quick question, in this layout, is the chaining going on the outside of the chassis or on the inside?

24-05-2010 20:36

NickE

Re: pic: Schreiber Take on West Coast Drive

Some of our team members like to call it NCAD (Not Computer Aided Design)
With dead axles, I would assume that the chain would run on the same side as the wheels (outside).

24-05-2010 20:49

ttldomination

Re: pic: Schreiber Take on West Coast Drive

Oh, did not real the part about the dead axles.

Looks legit.

24-05-2010 20:50

sgreco

Re: pic: Schreiber Take on West Coast Drive

Nice render. I find it very hard to believe that you didn't click the "make it pretty button."

24-05-2010 21:42

Zach O

Re: pic: Schreiber Take on West Coast Drive

Snarky. Although I am a fan of what your showing. We need to stop relying so much on computers to do all the work for us, and knowing how to do it by hand is always a good skill. However, technology is the future. The reason we have these things is so that we don't have to do it by hand anymore. We can have machines do stress analysis for us, saving us time of going though it by hand. However, the skill of calculating things by hand and sketching by hand is something that we should continue to teach the youth (until my netbook can run Inventor )

24-05-2010 22:20

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Yes, the stress did come preformed on the napkin. Upon analyzing it I found it quite pretty and it did an adequate of cleaning up the barbecue sauce.

24-05-2010 22:49

Tom Line

Re: pic: Schreiber Take on West Coast Drive

I'm in total agreement Andrew.

One of the HUGE things that I think the cad monkeys miss out on (and I'm one myself now), is the gut feel you develop of how this stuff works out and the talent of visualizing this stuff in multiple views in your head.

Being able to close your eyes and actually see the views, rotate the components, and then say "yep, that'll work" rather than having to cad it is a talent that is only developed through use.

If you're used to sitting down and drawing something every time, you'll never develope the visualization skills to do it. Heck, I spend nights in bed when I'm falling asleep doing exactly this during first season. Especially with control board layouts.

24-05-2010 23:27

548swimmer

Re: pic: Schreiber Take on West Coast Drive

This is a very good point. Since Ill be training a new CAD team over the summer, Ill try to emphasize visiualization before CADding.

I wouldn't say they all are missing it though. Most of my friends in CAD are equally competent sketchers, they just prefer the completeness you get from CAD. Maybe this has somethig to do with the fact that my school mandates a year of hand drafting before CAD.

I do think visiualizing ideas first is becoming a last art though.

25-05-2010 00:06

Akash Rastogi

Re: pic: Schreiber Take on West Coast Drive

Where's the "like" button?

For anyone else who enjoys detailed hand drawings like I do, I put up this thread a while ago that has some great resources in it.

http://www.chiefdelphi.com/forums/sh...ad.php?t=79220

.

25-05-2010 00:25

kstl99

Re: pic: Schreiber Take on West Coast Drive

I have two thoughts on the value of being able to at least estimate without CAD.

It is very easy to make silly mistakes while using CAD that cause results to be way off. It is quite useful to be able to recognize when things don't make sense.

It is also handy to be able to come up with sensible ideas quickly at the beginning of the build season or of a project at work when many decisions are made without the time to do the CAD.

25-05-2010 04:44

Chris is me

Re: pic: Schreiber Take on West Coast Drive

The funny thing here is that while you're preaching to us how doing the math is better than a pretty render, I think your drivetrain won't perform adequately with the gearing you've outlined. 10 fps with 4 CIMs isn't the best acceleration, and you are nowhere close to traction limited. Pushing matches will probably trip your breaker faster than I would be comfortable with. Your gearing would probably eat through batteries faster than I would want as well. You could increase your reduction a bit to become traction limited at much more feasible currents, while increasing your acceleration enough to virtually make up for the speed loss in a Breakaway like field.

This is assuming you bring your robot to full weight. At the 27 pounds pictured, I bet you would have zero problems.

25-05-2010 13:00

MrForbes

Re: pic: Schreiber Take on West Coast Drive

Chris, the two speed sketch is on the reverse side of the napkin, you can't see it

I like to move straight from NCAD to MAC machining (manual analog control)

25-05-2010 13:04

JamesCH95

Re: pic: Schreiber Take on West Coast Drive

Good stuff. An excellent ME/Designer that used to be my mentor said that if I couldn't design it on a napkin then I couldn't design it at all.

25-05-2010 13:16

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Couldn't or Shouldn't? I know a lot of guys who are of the opinion that if you can't explain the idea using a napkin and a pen you are probably over complicating it.


Specifically, what part of my math did I do wrong? (Remember folks, I am a programmer, I do this in my spare time) I worked out what the speed of the motor at 40 amps was and based the speed off that. Is a 5.97:1 reduction too little for a 4" wheel?

25-05-2010 15:06

JamesCH95

Re: pic: Schreiber Take on West Coast Drive

Well I suppose one probably could still design it, but like you said, it's probably not an elegant solution.



I think your powertrain calcs are probably fine, and I wouldn't worry too much about acceleration. My freshman year (2001) we ran 2 Bosch drill motors geared for 10ft/s and it worked wonderfully, 4 cims should have plenty of torque to get you by. You probably won't win a pushing match against a hardcore pushing robot, but that's what shifting transmissions are for if you chose to use them.

25-05-2010 15:22

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Yeah, looking into it, interfacing a Super Shifter in there with a 45:20 gear set would be feasible. I may have to buy an extended output shaft. The ratios wouldn't be optimal though. By tweaking the way I drive the center wheel I could also use the Gen 1 shifters which offer slightly better ratios. But that would get pricey real quick.

25-05-2010 15:46

JamesCH95

Re: pic: Schreiber Take on West Coast Drive

What is "optimal" for this robot? IMHO 5-12 ft/s is is a very generous range. Any faster and an operator can't control it too well, any slower and virtually anyone will be able to dodge you. Just a thought.

25-05-2010 15:52

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

That would depend on the game, obviously if it were a game like last year I would say 8fps. For a game like 2008? 10fps seems more than fast enough for me. There are games that I would prefer more oomph (2007) and would settle for 6fps (For reference, in 2007 the team I was on never crossed past midfield) This is one of the major reasons I like AM products, they have a wide range of options that do not change the mounting/interface options. Heck, if I wanted to switch to 6" wheels I could do so relatively easily with a simple swap of gears in the transmission.

25-05-2010 16:14

JamesCH95

Re: pic: Schreiber Take on West Coast Drive

So if I'm understanding you right 5-12fps would cover you, with a reasonable margin, for any game within recent memory I like where your design is going

Just a little thing I gambled on this year that paid off: keep your CG behind the bumper zone, not as low as possible (assuming the bumper zone isn't insanely high, of course). 96.3% of the time robot-robot contact is bumper-to-bumper and having your CG/center of inertia in the bumper zone will help keep your robot from flipping. I'll let you do the fizix.

25-05-2010 16:24

Jared Russell

Re: pic: Schreiber Take on West Coast Drive

Here's how I would design a two-speed transmission. I always try to have specific goals for my low and high gearing to "optimize" the way that I'm using the motors' mechanical power.

LOW GEAR ANALYSIS:
Goal: Be traction limited at 40A per motor
Rationale: This will let us push as hard as we can without ever popping breakers.

Assuming the load is something like 145 lbs (robot+battery+bumpers) and you are using roughtop with a static CoF ~= 1.3, the maximum amount of force that you can transfer to the ground is about 190lbs.

Assuming 4 drive motors (CIMs), and 4 inch wheels, each motor can contribute up to (190 lbs) / (4 motors) * (2 inch wheel radius) = 95 in-lb of torque before you slip your wheels.

Stall torque of a CIM is about 21.5 in-lb (at 133A). Torque at 40A is more like 6.2 in-lb. And then there's gear-train inefficiency - let's say you have a good spur gearbox for a total efficiency of 90%. Now your torque is 5.5 in-lb per motor.

So if you want to be able to push ~190lbs across the floor all the live-long day, a reduction like 95/5.5 = 17.2:1 would get the job done. When not pushing, you would expect to move at a clip of about 4.5-5 fps (I generally find that 80-85% of the "free speed" of the motor, divided by the gear ratio, gives a good top speed estimate. It is never exactly the free speed because of drag in the gear train).

HIGH GEAR ANALYSIS:
Goal: Be traction limited at 75% stall (100A per motor)
Rationale: We will be able to turn in the upper 25% of the motor power curve (since we need to skid our wheels in order to turn in a tank drive). At the same time, our max speed will be very high. We don't worry about the 40A breakers, because they won't trip unless there is a constant (> a couple seconds) heavy draw, and we will downshift if there is a need for that...

Assume all the same things as before...4 CIMs outputting 21.5 oz-in of torque and 190 lbs of total load. But now at 75% stall and 90% efficiency, we expect ~14 oz-in of torque instead of 5.5 as before. 95/14 ~= 6.8:1. We expect a top speed of about 11-12 fps.

Obviously, the goals at each design point will vary widely depending on what you are trying to do - these are only two possible criteria. For a single speed drive, you'd need to trade off between popping breakers/being traction limited and having a good degree of speed and agility.

Likewise, the missing "last step" that I would always go through would be to compare my desired ratios with those that I can easily achieve by utilizing COTS components and my teams' manufacturing capabilities. For example, a SuperShifter (with the last stage removed) can achieve ratios of 10.67:1 and 4.17:1. Coupled with a chain reduction of about 1.6:1, I get 17:1 and 6.7:1, which are pretty close to my theoretical goals using 4 inch wheels.

25-05-2010 16:24

JesseK

Re: pic: Schreiber Take on West Coast Drive

Andrew, I don't know a single employer who would take a napkin sketch and arbitrary numbers over a full CAD given a choice between the two. It's a shame that you're mocking everyone who requests feedback on various frame designs while also learning.

CAD is never a crutch; it's simply one of the many pieces to the equation of a high quality product.

25-05-2010 16:28

AdamHeard

Re: pic: Schreiber Take on West Coast Drive

There are a good amount of people who post pretty renders of designs that aren't even fully functional in my opinion, yet they spent the time to make a pretty render and CAD arbitrary details.

I agree with Andrew, you should be able to plan what actually is going to do the business (and all the details of it) in your head before you start making pretty CAD.

I don't think Andrew intends to go into season with a napkin sketch and machine from there. A nice worked out concept will save much time when it comes to the detailed design in CAD.

973 works the same way; we CAD 100% and machine 100% to print, but almost every system is sketched out by hand, on a whiteboard, made from paper, etc. before we begin designing. We'll often work out ideal ratios, sizes and stages of reduction before CAD even begins; it allows much more efficient design.

25-05-2010 16:34

Jared Russell

Re: pic: Schreiber Take on West Coast Drive

I am struggling with why having a high CoG would prevent you from flipping in the event of a collision.

If anything, lowering the traction of your wheels would seem to do the most good since it would prevent your entire robot from becoming a lever arm rooted in the ground.

25-05-2010 16:38

JamesCH95

Re: pic: Schreiber Take on West Coast Drive

I think the point is that if a designer/engineer has a very clear idea of what an elegant solution is, could be, they should be able to explain or convey the needed information with simple sketches, and then spend a minimum amount of time detailing the design in a CAD program. The N-CAD skill can be invaluable and it seems as if many students are missing it.

As an example: 2 months after I was hired I was responsible for designing a number of replacement parts for a high-g-load testing machine that was not working properly. This machine was too dangerous to run in our main engineering building, so a technician and I were over an hour away from any CAD-capable computer, but only 10 minutes from a machine shop when we were debugging it. My employer was VERY happy for me to make hand sketches of parts to give to the machine shop because saved time and money on the project as the deadline loomed nearer (not to mention many miles on my car!)

25-05-2010 16:39

JesseK

Re: pic: Schreiber Take on West Coast Drive

If you re-read Andrew's post as if you were brand new to these forums, you may find that (specifically) the final paragraph is incredibly off-putting to someone trying to do a CAD by themselves for the first time, not knowing what they're really supposed to know in order to do things correctly. Andrew has exemplified the common CD knowledge paradox. Sure, all of the recent CAD prototypes are 'pretty', and most of them are missing details, yet the negative implications of Andrew's tone are as common as the missing details themselves.

25-05-2010 16:44

548swimmer

Re: pic: Schreiber Take on West Coast Drive

Think about free body diagrams. The forces always go to the center of mass (in this case, gravity), of the object. A CG directly in line with the bumper zone will create a force applied that is parallel to the ground. This eliminates the levering issue, as well as flipping.

25-05-2010 16:49

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Am I looking for a job designing gearboxes? Do I work in that field? No. But I do know that most employers would rather me take the 30 seconds it takes to draw a rough sketch of an idea to make sure it would work than spend 2 hrs in CAD.

Would you call a lot of what has been posted recently full CAD or would you call it a bunch of cookie cutter components tossed together? I would say the latter. And yes, I am going to mock them. I am ok with them learning, heaven knows I still am, but this constant stream of "West Coast Drive" CADs that are only differentiable by their color is irritating. Sure, I could have put more time into my drawing but the important parts are there in my opinion. Wheel placement (having them overhung), chain placement, approximate weight, and a reasonable gearing based upon simple calculations. (Which I will be redoing thanks to Jared's post)

CAD used as a tool to help further a design is a tool. CAD used to assemble parts that you downloaded off the internet and then making a pretty picture without any understanding of what you are doing is a crutch.


Yes, my last paragraph was meant to be that way. I, as a mentor whose job it is to inspire (not teach) students, would be floored if we were to have dozens of students asking how to properly do calculations for drive trains or arms. They have their college years to learn CAD (and will probably have to relearn a different piece of software for their jobs). Instead they are designing systems that, in all likelihood, will not work because they made some mistake that would have been solved had they first taken the time to do a quick sketch on a white board. So, if I turn off a couple people from jumping right into CAD I am fine with that as long as it also gets some people thinking about doing the math.

25-05-2010 17:10

548swimmer

Re: pic: Schreiber Take on West Coast Drive

I know that I posted my designs to receive structural feedback, not feedback involving gear ratios and the math involved in the traction. I'm all for sketching by hand, but there is some structural feed back you just can't get off of a napkin.

25-05-2010 17:14

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Which would be "doing the math" would it not be? I disagree that there is structural feedback you can't get off a napkin since the lightening of 2337's hanging system was a napkin* sketch but I will give you the benefit of the doubt. The ones that bother me are the ones that say, "We go X fps" and then when questioned about that number are unable to tell us their ratios. To me it screams that they pulled a number out of their behind.


*Actually, I think Spaz Dad used the back of another sheet of paper

25-05-2010 17:15

AdamHeard

Re: pic: Schreiber Take on West Coast Drive

I disagree there as well. A good, clean, efficient design should have a frame that can be sketched by hand and explained in 30 seconds or less.

A frame can still be strong if it doesn't meet that requirement, but that means it's probably pretty inefficient and complex.

25-05-2010 19:18

548swimmer

Re: pic: Schreiber Take on West Coast Drive

I agree that things such as lightening patterns can be done easily on sheets of paper, but more complex mechanisms such as our kicker pull-back mechanism should be done primarily in CAD.

25-05-2010 19:21

Chris is me

Re: pic: Schreiber Take on West Coast Drive

You can make a winch on paper...

25-05-2010 19:34

EricH

Re: pic: Schreiber Take on West Coast Drive

You'd be surprised at how many things can be done on paper quickly, including "complex" mechanisms like kicker pull-backs.

Let's go back in time a few years, to the airplane and tank designs of WWII. Did they have computers? No. At least, not that were capable of running CAD programs other than number-crunching to do analysis and things of that nature. So, how do you think they designed all their engines, landing gear, treads, guns, turret-turning devices, and all that sort of thing to create the given airplane or tank?

Yep, on paper, with enough accuracy to use them to make and assemble parts that worked, a few thousand times over per part.

How about the interrupter gear in WWI, which allowed a plane to shoot through its own propeller without damaging itself? Paper, and relatively complex. And I'd be willing to bet that Mr. Fokker, if placed in the modern world and told to sketch the interrupter gear, or even create a production drawing of it, could do it faster and just as accurately as a good CADder.

The point is, while CAD is nice because it can quickly turn a part model into a machining drawing (or, with assistance from other programs, into code for a CNC to make the part), pencil and paper is just as effective in the hands of someone who knows how to use it well.

"Don't underestimate the ability of a highly skilled technician with simple tools..." --Dave Lavery, in response to someone saying something about not having good enough tools in http://www.chiefdelphi.com/forums/sh...661#post119661

25-05-2010 19:36

548swimmer

Re: pic: Schreiber Take on West Coast Drive

How long would it take you to change the spacing of your sprockets used in the pull back on paper?

How long would it take to create a piece you can water-jet with your paper sketch? About as long as it would take you to just CAD it originally.

I'm all for conceptual sketches being done on paper, but it seems unintelligent to not utilize all of your resources (CAD).

25-05-2010 19:39

548swimmer

Re: pic: Schreiber Take on West Coast Drive

Didn't see this when I hit reply...

Paper and pencil is to those times as CAD is to modern times. Sure, there are still uses for hand drafting in today's environment, but CADding is becoming more and more important. I'm not suggesting you eliminate all drafting instruction, but that you consider what will be most useful in the future.

25-05-2010 19:44

Mike Schreiber

Re: pic: Schreiber Take on West Coast Drive

I don't know a single employer who would hire someone based on a full CAD with no explanation and no knowledge of how it works. It's all about the interview and if you can't explain/justify your design decisions you're not getting that job.

25-05-2010 19:51

548swimmer

Re: pic: Schreiber Take on West Coast Drive

Why would you think that someone who knows only CAD would have no knowledge of how to design (I'm assuming this is the "it"). I would be highly surprised if anyone who knows only CAD would have an issue making a pencil sketch such as the picture for this post. Many of the drivetrain ideas posted on here are done in CAD simply because it takes more time. I work on new ideas instead of doing my homework, so if pencil sketches let me get back my homework in five minutes, I'd rather spend an hour CADding.

25-05-2010 19:53

ttldomination

Re: pic: Schreiber Take on West Coast Drive

If you don't know how it works, how did you create the CAD in the first place?

The argument here is the base definition of pointless. One side is arguing that simple tools are alright as long as you have the skills to implement your goals, while the other sides is arguing that the tools are needed as well.

I guess I'm an alumni now, so I would prefer the students on my team have the know how of the skills and the ability to present their ideas/skills in a professional manner.

- Sunny

25-05-2010 20:00

548swimmer

Re: pic: Schreiber Take on West Coast Drive

Thank you!

25-05-2010 20:03

Chris is me

Re: pic: Schreiber Take on West Coast Drive

I've seen plenty of chassis CADed with gearboxes just dropped in place, without any thought to the gearing whatsoever. There are things you can make CAD of without understanding.

25-05-2010 20:07

AdamHeard

Re: pic: Schreiber Take on West Coast Drive

There is an awful lot of "what" with no "why".

25-05-2010 20:09

MrForbes

Re: pic: Schreiber Take on West Coast Drive

In the old days, there was a difference between a draftsman and an engineer. I think there still is.

25-05-2010 20:18

Madison

Re: pic: Schreiber Take on West Coast Drive

I think singling out that the students are rendering pictures of their models is a pointless exercise. That process takes a small fraction of time compared to what likely goes into modeling and constraining the parts in the first place.

I think, in reality, a point that can be successfully made is that a lot of these designs are built upon completely arbitrary criteria that have no real-world implications. They all mimic one another and those that have been successful before them, but they're not designed for any other particular purpose. Teams have had success copying 60/254/968, 148/217, et. al., but they never really grasp what makes these teams opt for certain methods or materials. That's something of a problem.

I can assure you that there are many more people that know how to operate CAD than can design effectively. We have tremendous trouble where I work finding people that are qualified to do both and frequent trouble finding people qualified to do even one or the other.

All of that being said, I learned a lot of what I know about design and all of what I know about CAD from messing around and trying to improve upon things I saw here and at competitions. With time, I grew to understand more about why certain designs worked and why others didn't and experienced a fair share of failures. I've been working as a design engineer for about four years now and am pretty damned good at it as a result of what I learned here. I think these forums can continue to be useful to new people in that regard if they're clear about the intent of their design.

When folks post a new picture or idea, it'd be amazing if they also outlined the constraints they worked under while designing and evaluated if they met those goals. Allow yourselves a hard limit on weight or materials or resources and see what you come up with.

25-05-2010 20:29

EricH

Re: pic: Schreiber Take on West Coast Drive

Pencil sketches can get you back to homework in under 5 minutes. The hour CADding without doing your homework, however, we BOTH know is an hour that could be better spent. [Insert discussion on how school is more important than refining CAD skills--for now--here.]

I can get you a concept drawing, by hand, on a letter-size piece of paper, in about 15 minutes. CAD for the same thing (concept) would take me about half an hour, if I was willing to fudge some things like basic shapes. Detailed CAD would take at least a week fitting it around homework; a more detailed hand drawing could between an hour and 3-4 hours, depending on the level of detail required--with fitting around homework, call it a couple of days.

I once spent about 3 days CADding something that the concept sketches took mere minutes to do. It's a lot more time intensive to CAD something.

What Andrew showed was a concept sketch. That's how you sell a product to investors or your company, or rough out an idea. When people post CAD pictures on here, they're posting production material--what will eventually be used to build the part. Could you use production material for a concept sketch? Sure, given enough time. But when the deadline's in a couple of hours, and you need to explain something, two or three concept sketches that are on time can be worth every part in the production CAD assembly, two months after the deadline.

25-05-2010 20:34

CENTURION

Re: pic: Schreiber Take on West Coast Drive

Hahaha I usually end up doing pages and pages of sketches before even presenting an idea to my team ( I have too much free time at school )

Half of them end up being junk of course, and I can't do any of those kinds of advanced calculations (Yet), but my study hall time usually yields some pretty crazy stuff. and then if I like it enough, I'll do a quick Google Sketchup model or something on my laptop (I'm still learning "real" CAD, but have gotten quite proficient with Sketchup)

Over the past year that I've been on the team, I've been trying to get other students do do more sketches, it seems they just want to wing it, and build as they go

25-05-2010 20:51

R.C.

Re: pic: Schreiber Take on West Coast Drive

Madison,

I agree with you here. Rendering doesn't take that much longer. Most of the time goes into making the model and only a fraction goes into rendering. Well most of the rendering process is just letting it do its own thing. It's pretty interesting to see elegant renders that show a lot of detail aka Lewis comes to mind (roboticwanderor).

Also most drawings are just copied and re-iterated. Some are just bandwagon drawings. Such as swerves and sheet. Sometimes I wish people actually thought about x resources they have and then try to improve their design based off their resources. For our team is it really really retarded to design sheet parts, but for teams like 148 its amazing since they have the ability to.

Over the years as a CAD person on CD I have learned that most of my ideas don't work and if they do, not well. These forums have taught me a lot about material properties, clean design, and working toward simplicity. It just takes some patience and the right people to help you understand what your doing wrong.

Andrew I love your napkin sketch. Most if not all my drawings are roughly sketched in my notepad and drawn over and over till I find "THAT" model. It saves a lot of time already having something to base your CAD off of. I'm sure a lot of teams take this approach already: Napkin -> Whiteboard -> Paper -> CAD -> CAM or Sponsor -> Part.

-RC

25-05-2010 21:02

sdcantrell56

Re: pic: Schreiber Take on West Coast Drive

I am echoing a lot of the sentiments voiced on here. Too many people seem to be designing things without really thinking about what their team can actually produce and what would be the best for them. Specifically, all the sheet metal and west coast style drivetrains lately. While I agree many of the teams that do west coast and sheet metal drive trains do very well with them, it is because they understand all of the intricacies of the design and have the resources to implement it properly. Teams should do like RC says and really focus on designing for their resources and for their goals. While I greatly admire the "simplicity: of west coast drives and love the integrated design of the 148 style sheet chassis, chances are you will not see a 1771 chassis out of anything but wood. We have tried other things and for us we can achieve the most optimized chassis building with laser cut plywood.

Secondly, the idea that Andrew brought up about people spending so much time on CAD and not actually thinking through the design is alarming. The design that comes to mind right now is a west coast one seen in the past week that is beautifully rendered and has jags, battery, etc included but doesnt have any bearing blocks, axles, or tensioners. Basically it is missing all of the crucial parts of a chassis and the most important parts of a drivetrain. The time spent plugging in all the existing models would be much better spent actually figuring out the drive train specifics.

25-05-2010 21:23

Re: pic: Schreiber Take on West Coast Drive

We at 114 try to use WAD (Whiteboard Aided Design) before we move to the computers. Once students can understand the goal of their design, they use CAD for what it is: A tool to enact a design. CAD is simply a step that is used to bring a design to reality, and nothing more.

The design is more than the CAD. The design is the thought, the sketches, and the math involved in bringing the mechanism to reality.

25-05-2010 21:44

kgzak

Re: pic: Schreiber Take on West Coast Drive

That is pretty much what I have done for everyone of my designs except I use paper and a pencil. I only recently learned CAD so Most of my ideas have had to be given to CAD people. In my opinion that helped because my drawings had to be done so that others could turn it into CAD.

25-05-2010 22:25

Mike Schreiber

Re: pic: Schreiber Take on West Coast Drive

My argument is that if you say it goes this fast and they say how'd you get that number and you are stumped, what have you accomplished? You aren't getting that job.

The students who post well thought out designs with chain runs planned, ratios thought out, structural consideration, etc. are doing wonderful. They know how it works. I'm not saying you need every number, but if there's a number given it needs to be backed up. Pulling 11ft/sec out of nowhere is pointless. There are people who don't know how it works who are posting stuff. As Chris said:

Chris' situation is what I'm referring to as the base definition of pointless. The students who learned mate and downloaded a bunch of stuff of AM...

Yes learning the basics of CAD is important. But there aren't many people who sit around and CAD all day without knowing anything about what they're drawing. There's a lot of those on CD.

As Adam said...A lot of "what" and very little "why"

Do I believe saying anything about these students posting random things will do anything? Not even the slightest.

26-05-2010 09:31

IKE

Re: pic: Schreiber Take on West Coast Drive

If it is not hurting their grades, then what is really the issue with people cadding up ideas and submitting them for criticism and critique. Granted about 50% of the responses could be run from Auto-pilot, but so be it. I am sure that each one fo the students that threw their hat in the ring got some good advice. I really like Schreiber's sketch because it reminds us to do some figuring first, but we should all turn the snarkiness down just a bit on students that are excited about drawing up their ideas. While most would pass as loose interpretations of role model designs, they have brought up a lot of good responses like chain tensioner planning and design, chassis stiffness, how to make your chassis rock...
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Warning: Slight thread Hijack

Maybe those that are tired of seeing renders should work on a compliation paper of different 6WD designs, fabrication techniques, andd what teams love and hate about them. I know a couple posters in this thread have already done some great work on this material. Adding to their material and other presentations like Patton's and a few others would be great.

SAE will often do a compiling of papers on subjects that have a common theme and individually are good, but as a whole are more powerful than the sum of their parts. Imagine a 6+WD Chassis book that showcases/benchmarks some of the different ways about doing a 6+WD. Talk with the teams that have these and what they like and dislike about them. You could compile a nice set of papers on:

Architectures: Basic architectures and benchmarking. 6, 8, 10+ WD architectures. Live or dead axles. Cantilevered or fully supported. Direct Drive or chain...
Chain tensioners: types and the pros/cons of different tensioning systems along with the importance of having just the right tension.
Chassis Dynamics: the "why won't my bot turn?" paper along with several others. Pros&Cons of chassis Flex.
Construction and Fabrication techniques: KOP, Sheet metal, welded frame, 8020 frame, wood, plastic...
Power Transmission: Design guidelines for speed/traction philosophies. Designing powertrains with COTS. Custom gearboxes. Chains vs. Belts vs. Geardives.

If this book or collection existed, then you could just point up&coming chassis designers to the collection and off they can go.

IKE

26-05-2010 11:16

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Oh, I am not arguing that the tools are pointless. I am arguing that the tools are pointless without the skills and knowledge to use them. The word I used, crutch, implies that it is an aid. There are times when a crutch is the appropriate solution to a problem. There are also times when you don't need one.

I would also like to point out a drawing that caught a bit of attention in 2006. http://www.chiefdelphi.com/media/photos/22693 Anthony didn't draw the detail of a spur gear and caught a bit of flack for saying it was frivolous. Why should we have to design every single gear tooth in cad? You know the size of the gear what is the issue?

My point is, use the right tool for the job. For me sketching a quick idea was the right tool at the time. I wasn't really sure how I wanted to position things. I did a couple other sketches that you don't see. On one I don't direct drive the middle wheel. A couple where I sketched in the battery. You know, I did about 4 different sketches in about 7-10 minutes. Would it be possible in CAD? Sure, but it would take me a bit longer, heck, 2 minutes of that would be loading Solidworks.

26-05-2010 22:28

Tom Bottiglieri

Re: pic: Schreiber Take on West Coast Drive

So if one of the students you 'mentor' was excited enough about their team to CAD up a full robot component, you would also scold them with sarcastic put downs... right?

26-05-2010 22:35

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Depends, if they brought it to me and said, "How do I figure out how I should drive the wheels?" I would be happy and bend over backwards to help them out. If they brought something to me making wild claims with no facts, yeah, I would be irritated by them, depending on the student I may make snide remarks.

27-05-2010 00:39

Chris is me

Re: pic: Schreiber Take on West Coast Drive

Well, they're getting excited about using science and technology to solve a tough problem...

27-05-2010 09:14

Nikhil Bajaj

Re: pic: Schreiber Take on West Coast Drive

See below

27-05-2010 09:20

Nikhil Bajaj

Re: pic: Schreiber Take on West Coast Drive

While I somewhat agree with the sentiment that, "Hey, maybe we should encourage kids who are making these CAD drawings to learn how to do some of the math, too..." I do have some reservations about some of the ideas here.

First of all, as mentors, it is our job to encourage students to pursue these avenues. Anyone who can think logically and do multiplication and division can do gear ratio calculations. I don't know why we're making such a big deal about this, because they are pretty trivial. There's no calculus involved, and the physics typically utilized by most FRC teams to make such decisions are really simple. That's fine--that's all the math it requires. Any high school student with a geometry/trigonometry background and encouragement and support from a mentor should be able to do it. So we can just tell them that the math is easy to do for these things, and give them an idea of how to do it. Then they will think for other systems that the math may be similarly easy, and give it a shot themselves.

In fact, I'd argue, as someone who has been involved in solid and structural mechanics over the past few years, that those who CAD chassis, etc. and put them up for review could be the wiser ones. Structural systems are much harder to "do the math" for. I would not expect someone without three or four semesters of engineering/technology college education to do much more than get an intuitive understanding, much less "run the numbers" or "do the math." It would be difficult to teach this material to high school students, and it is unlikely that even the minority of mentors in FRC would be able to do a good job of much more than an intuitive understanding. Sure, Inventor/Solidworks/ProE etc. do supply finite element method capability, but the variability in those results is so great when in the hands of a novice that one should give those factors of safety a wide berth. They should still be performed though, but the factors of safety should be held a little suspect.

The students who are posting these things here are probably not from teams where their mentors have proclaimed an aversion to "not doing the numbers" or whatever, and probably have not been directly encouraged to "do the math first." So why be snarky or sarcastic about it? I know it is well-meaning, but it is pretty off-putting, especially for me as a fellow mentor. Instead just encourage them to "do the numbers," post up a white paper and refer people to it every so often, and that's it. I liked IKE's idea of the paper compilation, and especially that he restricted the scope to 6+WDs, so that the topic wouldn't get diluted and people could get a lot of detail out of it. You could even just give a horror story of when someone didn't use the numbers, and tell them to be careful. But there's no need for snarkiness/sarcasm, especially in a public forum.

CAD is a useful tool, and those who post their designs and work here are pretty brave to do so. I'm just glad they are learning something, and trying to learn from others in the forums. We can be snarky and off-putting in the way we respond to them in an attempt to improve their designs and methods, or we can...just tell them directly and be nice about it.

You catch more flies with honey...

27-05-2010 10:45

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

If the math is so easy why do so many people not do it? I agree it is easy but I also feel it is easy to fall into the trap of it being so trivial that you assume your gut instincts are satisfactory. Just because something is easy doesn't mean it isn't still important.

I disagree that there is no need for sarcasm. I can either be nice and try to be subtle in getting people to think through what they are doing instead of posting "me-too" cads and some of them might pick up on it or I could be sarcastic. They could join me in a laugh at the anonymous person I am making fun of and realize how stupid it is not to do some simple thinking about your design.

I see too much form over function on these boards. Last year I saw a robot that didn't move much of its first competition but gosh darn it was painted pretty! If that is supposed to be inspiring then we all must have some pretty low standards. I guess I just hold a higher opinion of people, I assume they can take some criticism and I don't have to always tell them what a wonderful job they did even if it is a complete and utter lie.


Yeah, I'll tone down the sarcasm in the future. No I will not lie to a student telling them to keep up the good work if they are doing crap work. No I will not stop asking people not to post things until they are at a point where community criticism will help make it better. (And yes, I consider a napkin drawing that point in some cases) And there is no way that I will stop criticizing people for making pretty renders of things they didn't think through.

27-05-2010 11:05

Ryan Dognaux

Re: pic: Schreiber Take on West Coast Drive

I don't think laughing at people, even if they are anonymous, is a very constructive way to mentor students. Since when was publicly making fun of people in FIRST, even if they are anonymous, an okay thing to do?

I understand the point of this thread, but it could have been handled in a way more constructive manner.

27-05-2010 13:19

IKE

Re: pic: Schreiber Take on West Coast Drive

I would recommend shying away from can't, won't, and never... and save those for morals and beliefs rather than mentoring techniques.

Different students (and mentors) require different techniques. While some really need a firm hand (that sarcasm may actually be the best tool), others need support and guidance and tons of encouragement.

While I agree that you can't inspire greatness with Mediocrity, we are not always looking for greatness (initially). Every great runner begins life taking baby-steps.

CAD/drawing and Speed Ratio calcs are basis/foundation from which you can build upon. Essentially they are math and geometry. Once they have a strong foundation, ask the student to continue to explore. For drivetrains, it is torque and traction and learning to estimate "static" loads anlong with geometry based stiffness techniques. Once they have a firm grasp of that, you can begin to discuss dynamic loading and structural analysis (Most teams never get this far). You can also discuss system and power constraints and short-term vs. long term current draws.

While sarcasm can be a good motivator and build bonds with some students, it can be off-putting to someone with lower self esteem or thinner skin. In a public forum, we should probably err towards the Kindest Common Denominator. This doesn't mean lying or coddling, but it does mean deburring the edges and rounding the corners on your support pieces.

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Even Woodie Flowers has given talks on "False Engineering", so Schreiber's thread is really quite important, he just forgot the KCD function.

27-05-2010 14:26

JaneYoung

Re: pic: Schreiber Take on West Coast Drive

What part of getting people to join you in a laugh at someone that you are making fun of has anything to do with mentoring or with the purpose of Chief Delphi?

A person, anonymous or not, may or may not realize how stupid it is not to do some simple thinking about a design, whether sarcasm is used or not. That's what is so special about the mentoring process - is being a part of the development of thinking and decision-making of a team and encouraging team members to pay attention to those areas of the process. Same thing when participating in discussions in Chief Delphi. There's no guarantee that there will be development but it is always very cool when there is. Madison's post reflects the value of what can be gained here in Chief Delphi and how it will impact an education and a career.

Mentors gather and collect mentoring tools during their time as FIRST mentors. The toolbox where they keep their mentoring tools varies in size, shape, and depth. The condition the tools are in varies depending on the mentor. The tools can be somewhat rusty or can be very clean and prepared for immediate use, as needed. The tools can be in need of some polishing or refurbishing, depending on where the mentor is on the journey of mentoring. In toolboxes, there can be a lot of organization and order or there can be a messy collection/mix of different tools all thrown together. In a mentoring toolbox, sometimes the search for the right set of tools for the job takes a while to sort out when making the wisest selection. The wisdom of continuing to keep the mentoring toolbox updated and organized allows for all of the different possibilities and opportunities of achieving the goal. If a mentor only makes use of one skill that he or she perceives to be a mentoring tool, such as sarcasm, then the possibilities and opportunities become limited and the tool loses its proper use.

.02,
Jane

28-05-2010 00:41

Mike Schreiber

Re: pic: Schreiber Take on West Coast Drive

So you admit it is stupid

Isn't that exactly what this thread is doing? While the methods are not conventional whose to say they are not effective.

Sarcasm CAN be a great mentoring skill if applied to the right students who have self confidence and can take a joke. No one is using ONLY sarcasm. It was used in this case because that's what was believed to be the most effective. Yes, not every mentoring technique works on every student and I don't believe anyone would disagree with that. I prefer an organized toolbox where I can find what I'm looking for quickly and use the correct tool for the job.

28-05-2010 09:47

JaneYoung

Re: pic: Schreiber Take on West Coast Drive

I'm not a fan of the word, stupid. It is a heavy word that has been lobbed at many young people's heads over time and I've been around to see the resulting effect, beginning in an elementary math class. I'll never forget the look on my classmate's face when our teacher used it on him, followed by a ruler to the palms.

This is a good thread. The topic is excellent and it is wonderful to listen in and find nuggets of wisdom in the posts. Some of the responses have triggered another topic and that is regarding the use of sarcasm when mentoring. I've found that those who use it, defend and support it. I've also found that sarcasm can create misunderstandings and defensive stances. If that is the goal of the mentor, then I ask why? If the use of sarcasm as a mentoring tool opens up thought processes and encourages development in the area of thinking and using common sense, then the mentor who wields the tool is wise and careful with its use.

One of the skills that I do appreciate is the use of humor as a mentoring tool. It, too, can be applied in a heavy-handed manner that shuts down communication or, it can be applied with a deftness and skill that leaves an impression much like an, 'aha, why didn't I think of that', moment.

Regarding the word, stupid. I like the word, awareness. Lack of awareness and understanding moving towards becoming more aware and working towards a deeper understanding. This thread is creating that opportunity.

Jane

28-05-2010 16:40

Andrew Schreiber

Re: pic: Schreiber Take on West Coast Drive

Stupid is a harsh word. Calling a specific student (who does not know me well) stupid is something I strive not to do. Sarcasm, however, is a tool I tend to employ when working with students. I think sometimes students need that humorous response to take criticism. Yes, sometimes students can't handle the sarcasm because they think I am mocking them rather than showing them to laugh at their own mistakes and then move on. Those students need to learn that lesson most of all.

Additionally, sometimes a defensive stance is a good thing. A student should be able to defend their design. More often than not I will tell a student to prove that something will work. I make them defend their logic and explain their thought process. Even if I know they are right or wrong they usually discover the answer to the question, "will this work" on their own. My sarcastic response of "prove it" usually leads to a much better understanding of a concept than me taking the time to explain.


(Obviously, this does not work on all students all of the time. There is a fine line between educating and frustrating.)

23-08-2010 00:36

roboticWanderor

Re: pic: Schreiber Take on West Coast Drive

you should see my sketch books from FIRST, i had more pages of gear calculations, BOMs, and math than i did sketches of actual parts. i ended up sketching out my gearboxes with a compass before i even touched solidworks.
HOWEVER.....
using SW to put hard numbers on your designs, and figure out the nitty gritty is much more work than the napkin sketches you use to jot down ideas. to go from sketch to product (especially in real world engineering) takes a lot more professionalism, thoroughness, and precision than a napkin can provide.

BOTH the innovation for a elegant design and the know-how to make it work are required to make ideas reality. Otherwise your just a drafter or a dreamer