pic: Doubble-wishbone Crab fender
 

:)
 

That's a great idea, but would you use it on a robot?

I have to admit I have NEVER seen that combo before.

Tytus,

I deffinatly give you a A+ for creativity.

Some problems that i see, your robot "chassis" is going to be very small, becaus those suspension stuts are going to take up a big chunck of space. also how are you going to rotate each pod? i noticed that each drive module is powered by one shaft out the top. are you going to attach 1 drive motor to run all those pods or are you going to have individual wheel w/ a motor?


Thats a really good idea, run with that

You need for the wheels in each module to be pointing in the same direction to work, obviously. It appears as if you planned on using belting that's common to two or more modules to achieve that.

I hope you've considered timing belt as an option or something else than won't slip. Slipping, over time, will throw off the alignment of your modules relative to one another.

More importantly, I don't understand how that belting is supposed to remain attached to a crab module that's going up and down on a suspension. Perhaps a better explanation of how the belting would interact with the frame and other modules would reveal how this works?

Why do you need a suspension? For more tire contact at all times? Surface area doesn't affect traction.

im thinking of going in the Half-shaft direction instead of the Kevlar for Propultion, the steering could be all linked for simplicity or all indivdual steeper-motors for some crab,Quadrosteer,and other wikid cool tricks. Please Feel free to throw your own ideas in there, it would look kinda like a starfish with 4 points, i know Its dard to Keep track of the scale of things in 3DS-MAX

Yes, it does. Search around CD for a bit and you'll see that we've beaten this into the ground. In fact, there's a whitepaper that shares some experimental results that were ascertained by a SPAM member (or family member, if I recall correctly.)

Don't ignore deformation.

mmkay, here goes:

Originaly posted by you, M:
If your wheel is a smooth surface (i.e., aluminum, two wheel chair wheels), double the area will do nothing to aid your traction at all. It will increase by a factor of 1.

So you are saying that on a smooth regular surface, the surface area doesn't matter.

Ok, so how about an irregular surface where the tire and and surface can intermesh, say on carpet?

From the whitepaper,: When the surface area went down the friction increased

Wait, is this saying that not only did the traction not go down, it went up?

Hmmm....

I'm sorry, but didn't you just establish a correlation between surface area and traction? It seems to me that you did. Never did I say that increasing your surface area increases your traction because that's simply not true in all cases.

However, it can be true and has been true in FIRST in the past. How do I know? I designed a drivetrain that was, apparently, stronger than 250 or so others and it was based entirely on deformation and the meshing of irregular surfaces.

Traction can go both ways with surface area. Rock crawler 4x4s (and sand vehicles) air down their tires for a bigger footprint. More suface area and more traction. But some 4x4 mudders (and snow vehicles) use really skinny tires so they can sink into it and get a bit on what's on the bottom rather than float over on top. I know this isn't really about traction on FIRST robots but it was the first example I could think of. There are just so many variables involved that it really depends on the exact materials and the exact situation.

Traction is such a complex issue that it's really not worth debating about because everyone is right and wrong, just in different ways. There are so many factors involved: tread, interlocking surfaces, surface area, friction, composition of both tractive surfaces, stickyness, softness of both surfaces, gravity, and that's just the beginning of them. Nascars have smooth tires on a very smooth surface but get incredibly good traction. 4x4s have very aggressively treaded tires on very uneven surfaces but get incredibly good traction. There is a different kind of tractive surface that works best for every terrain. And it being the best is only in the eyes of the operator. There are way too many things that make up traction for any one person to be right about what works the best for everyone. Just do what you think works good and let everybody else do what they think works good.

Problem solved.

Very impressive Tytus.

Only downside I see is it's size. If you wanted to put that on a FIRST bot you might want to shrink it down, so that you have more room available for electronics and any other mechanisms.

Keep up the good work

Its very hard to keep track of scale with 3ds-max its not in measuring units, its in standard numbers with no realitivty

The reason I think it looks big is because I'm imagining a wheel the size of the wheels in the kit as the wheel in your design, which is what, 6 or 8in diameter?

Hopefully you can build one sometime, I'd love to see a bot with that on it.

the skyway wheels are about 9.5 inches in diamater, I know itS WAY off scale

Tytus,
You can change the units on 3dsmax to inches and feet under the customize menu I think it is. On that menu is a units setup.
Eric

Amazing tutus.. that looks nearly like the suspension I drew up for my mentors..

1 question tho.. how do you plan on keeping any chains or kevlar intact.. in your design you have no motors showing so I assume the drive source is elsewhere. What happens ( and this may rarely happen in FIRST application.. but just a question ) when 1 side goes up and the other goes down.. you will have cause your chain to be on a angle to the drive. and run a high risk of it to come off.. or snap.. or not mesh with the sprockets correctly. The gear box would have to move in sink the wheel well dealio.. or.. it would have to be mounted on the wheel itself.. which in your situation would be best... However.. you could use U-Joynts and a drive shaft.. but then that would kinda defeat the purpose of crab.. and you would be way too inefficient

only problem we discovered with crab + suspension would be keeping it light enough yet strong enough so that in constant highspeed ramming matches ( which is first ) your suspension would not snap and your wheels fall to the floor.

Dan

Tytus,
What benefit do you get from putting your swerve module on some suspension? It seems like a significant amount of added complexity/weight/space for very little gain.

These kind of considerations are things you should think about while designing.

What will I get out of this?
What is it going to cost me?
Is it worth it?

Based on the historical FIRST games, I don't see any pressing need for a suspension system on a robot. Maybe if we went to a really rough/bumpy field.... but otherwise... you'd be better off spending the weight on the "ball mechanism" on top of the robot. :D ;)

It still looks cool.
A "coax swerve" is something I've been playing with for a while now. It gives you the option to use a CVT/Shifting Swerve drive.
If you are interested, check out team 998's bot from 2003. They had a working version of this.

Keep designing, keep thinking of new ideas, and good luck.

John

The suspension would have been of great use on this years game.. it would have kept all 4 wheels in contact with the surfaces at all times.. while battling on the edge of the ramp ( at carpet and the top ) many times whoever got most traction could win.. no matter how strong the drive train. This sort of suspension would be of great gain in that situation

actually, the easiest way to do that would not be a suspension per se, but merely have one of the axles on a pivot of some sort. If you don't quite understand what i'm getting at, take a quick glance at the back two wheels of this robot. They pivot freely so as to always keep surface contact.

There were a couple robots that i remember at nationals that had similar designs (can't remember numbers though). It could be done with a swerve drive like this (since it is coaxial, you shouldn't run into chain or motor alignment problems). The advantage of a pivoting system like this is that it will always keep the weight equally devided among the four wheels. A traditional suspension will keep all wheels on the ground, but different wheels will apply differing amoungts of force to the ground (making it less efficient.