15-02-2007 03:27

Gabe

Re: pic: Team 195 driving base 2007

WOW!!! Engine turned finish, full welded frame, anodized custom wheels, custom shifting transmissions...

Can I get a close up of those wheels?


(P.S. Please post more pictures!)

15-02-2007 03:47

Jeffrafa

Re: pic: Team 195 driving base 2007

Are those transmission plates delrin???

If so, that seems to have become a popular choice this year - Suddenly I feel left out with my plain old custom aluminum transmission plates ...

BTW - those wheels really came out nice with some anodizing! I'm still anxiously awaiting what ours will look like (they are going in tomorrow, hopefully)

- Jeff

15-02-2007 07:34

Rosiebotboss

Re: pic: Team 195 driving base 2007

What, no tank treads??

15-02-2007 08:58

Billfred

Re: pic: Team 195 driving base 2007

This plain looks awesome. Seems sort of reminiscent of West Coast Drive, with some requisite east-coast tweaks.

But what I'm really loving is how the CIMs are mounted on the transmissions. We're running the AndyMark two-speeds this season, and fitting them in with everything else has been a little hard at times. (Don't get me wrong, I still think we made the right choice for our situation--it's all part of the challenge.) Should the time come for us to start rolling our own transmissions, this is a picture I'm coming back to.

Hope to see this one in Atlanta!

15-02-2007 10:32

techtiger1

Re: pic: Team 195 driving base 2007

Kudos on the custom wheels and delrin plates very nice. West coast style drive is always a winner I like the modifications to it though you guys have made. 1251 has a similiar drive base this year. Ohh ya the finish on that box tube is sweet,neat touch. Looks like a battle ready base see you guys in Atlanta hopefully.

15-02-2007 11:23

Mike Norton

Re: pic: Team 195 driving base 2007

I think they are also taken on a new look this year. Nice rims I like the blue

15-02-2007 11:42

jjdebner

Re: pic: Team 195 driving base 2007

believe it or not the delrin is only in the temp chain tensioners...
all the black is simply ABS plastic

P.S.
the swirl finish looks really pretty black ;-)

15-02-2007 11:52

Tom Bottiglieri

Re: pic: Team 195 driving base 2007

Meh, I never did like the efficiency of those crash shifters.

Either way, you guys are gonna rock this year. This base looks good, and a practice bot/full playing field doesnt hurt!

(Any other college mentors feel like they got the short end of the stick when they left?)

15-02-2007 12:41

waiakea11

Re: pic: Team 195 driving base 2007

wow 6 wheels? how do you turn?

15-02-2007 14:58

Brandon Holley

Re: pic: Team 195 driving base 2007

cant wait to see this at the scrimmage !!!



tom...you were holding them back...hahaha jk guys

15-02-2007 15:03

Nuttyman54

Re: pic: Team 195 driving base 2007

You lower the middle wheel by a small amount (usually 1/8" to 1/4") so that at any given time your wheelbase is small for easy turning, but you have the stability of a longer wheelbase. Only 4 wheels can contact the ground at any given time (unless you have VERY soft carpet)

15-02-2007 19:02

Heretic121

Re: pic: Team 195 driving base 2007

Yes and thats why i came back =P...

looks great guys cant wait to see you at UTC *ill be scouting all of you for nats!!!*

15-02-2007 19:12

nuggetsyl

Re: pic: Team 195 driving base 2007

Y lower the middle wheel. Makes no sence.

15-02-2007 19:31

Nuttyman54

Re: pic: Team 195 driving base 2007

With any 4 wheel tank-drive wheelbase, long and narrow is much better at going straight, short and wide is better for turning. The problem with the short and wide is that it's easy to tip over in the forward and backwards because of the short wheelbase. The remedy is to take your long and narrow base and put a middle set of wheels that is lower than the rest. This gives you essentially two sets of "short n' wide" wheelbases that you rock between. This makes you hard to tip, but also makes it much more efficient to turn, and gets rid of the characteristic "hop" that many high-traction, 4wd robots have.

another version of the 6wd solution is to keep all the wheels on the same level and replace one or both of the outboard sets with omnis (see 488's robot this year)

15-02-2007 19:35

nuggetsyl

Re: pic: Team 195 driving base 2007

I would have to disagree with your logic. You do make a solid point, but by lowering the middle wheel you lose the whole point of making a 6 wheel drive robot. Think of it like tank treads but no messy tread part.

15-02-2007 20:02

Nuttyman54

Re: pic: Team 195 driving base 2007

I won't repeat all the arguments here, but you can find discussion about it here, and it would appear that a few of your mentors are quite familiar with 6wd systems. You'll also notice that most well-designed tank tread robots have a middle wheel that's slightly lower than the outer wheels, making it essentially a "lowered wheel" 6wd system

There is nothing here that says this is the ONLY way to do 6wd. Your team is living proof of that. I'm just trying to present the reasoning behind the lowered wheel. Many MANY teams use this design, so they can't all be wrong.

15-02-2007 20:15

Mike Norton

Re: pic: Team 195 driving base 2007

http://www.chiefdelphi.com/media/photos/26869

We only been doing wheel for two year so I am no expert but this system works. it is lowering the center wheel a little.

We did tank track before that and also had a center wheel

http://www.chiefdelphi.com/media/photos/18792

I think our robots has proven to have power

so what he is doing is a good way

16-02-2007 01:01

Lil' Lavery

Re: pic: Team 195 driving base 2007

In order to ensure better turning, the following relationship is key.

Or simply put, there are a few ways to improve turning. Shorten the wheel base, widen the track width, reduce lateral friction while keeping longitudinal friction high, and moving the center of mass away from the center of the wheelbase.
By lowering the center wheel, you effectively create two 4WDs with a shared center wheel. Each of these has a wheelbase roughly 1/2 of that of the same drivetrain with coplanar wheels. Also, closer the center of mass of your robot is to the center wheel, further it is away from the center of area of both of the wheelbases. Additionally, the traction and width factors should be the same as if you had a coplanar 6WD, and you still achieve many of the other benefits of a 6WD.

(Thanks to Chris Hibner for this terrific white paper on the physics of turning with a 4WD).

16-02-2007 01:29

Arefin Bari

Re: pic: Team 195 driving base 2007

Alright, I am going to use your team as an example. I can only assume and guess. I know you guys don't lower your middle wheels. Why? I have never been able to get a straight answer from anyone. You guys play around with your tread patterns a lot.

On the other hand, when you do a 6wd and don't lower your middle wheel, the robot is trying to turn on 6 different points. Depending on the friction you create with the wheel/tread you are using, it is very hard to turn unless you lower your middle wheel. While lowering the middle wheel, lots of team work on their CG. If the CG is low and the weight is distributed properly throughout the robot, while turning, the robot turns on 2 (middle) or 4 wheels (using only 4 different points to turn), creating less friction. At the same time, there are always 4 wheels touching the ground. I know wedgetop compresses, so if the weight is distributed properly, you get all 6 wheels touching the ground while going straight or back even if you lower your wheel. It also depends on the team how much they lower their middle wheels. I have seen teams do 1/16, 1/8, 3/16, 1/4, even 3/8 and lot of teams have been successful doing it too.

I sure would like to know how does a team turn without lowering their middle wheels. If there is anyone out there with a proper answer with reasonings behind it, please post.

Now back to topic...

As always, 195's chassis looks awesome. I am digging those wheels. Can't wait to see you guys in person. Let's not burn a victor out right before the final match this time. =)

27-02-2007 18:03

zander_108

Re: pic: Team 195 driving base 2007

I strongly agree with your argument. For your question, the Best example of a non-lowered center wheel robot that i can think of is 25 this year. And not only is it 6wd, its 8... If any members from 25 are reading... Enlighten us?

27-02-2007 18:15

meatmanek

Re: pic: Team 195 driving base 2007

Team 868 did a 4 wheel, long drivetrain in 2005. How did we turn? Very slowly. But we did drive in a straight line very nicely, something that mecanum and 2WD drives aren't able to do without software help.

What I'd really like to see is an eight wheel drive, with 4 centralized drive wheels that are in contact with the ground all of the time, except when accelerating hard in one direction, or pushed from the top. The front 2 and back 2 would be raised up a bit (1/8" or so), be smaller (to reduce weight), and probably unpowered. This would have the benefits of a long drivetrain, be stable (none of the rocking back and forth I'm guessing you get with a 6WD), and have a more predictable center of turning.

27-02-2007 18:21

lukevanoort

Re: pic: Team 195 driving base 2007

Psst, Arefin, read Dr. Joe's post here.