pic: Team 195 driving base 2007



Team 195 2007 base
2-speed 6WD
Custom Wheels

First time attempting an aluminum base :slight_smile:

EDIT:
more pictures and videos (sans arm)
http://lovejosh.net/josh/robotics

WOW!!!:smiley: :smiley: :smiley: Engine turned finish, full welded frame, anodized custom wheels, custom shifting transmissions…

Can I get a close up of those wheels? :slight_smile:

(P.S. Please post more pictures!)

:ahh: 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

What, no tank treads??

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!

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.

What, no tank treads??

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

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 :wink:

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?)

wow 6 wheels? how do you turn?

cant wait to see this at the scrimmage !!!

tom…you were holding them back…hahaha jk guys

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)

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!!!

Y lower the middle wheel. Makes no sence. :confused:

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)

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.:ahh:

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.

but by lowering the middle wheel you lose the whole point of making a 6 wheel drive robot.

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

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

longitudinal coefficient of friction x width of wheel base > lateral coefficient of friction (length of wheel base - 4((distance from center of area to center of mass)^2/length of wheel base))

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).

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. =)