Robots tilt

[lrdblaster03]

so you mean
regular wheels being like this (vertical) | |
and your tilted wheels being like this / /
or this /
or this /

hope that helps

edit:
i am saying / /, / \,\ / because certain machines tilt their wheels like that.

[B. Flaherty]

I think what lrdblaster03 is talking is something on ATV's. If you notice in this pic, the front wheels are mounted on an angle. So the real question I think is do you mean lowered wheels as in a 6wd configuration, or do want angled wheels for easier turning?

[sanddrag]

I'm not really sure how angled wheels would provide easier turning (I have seen teams do this for some odd reason I've yet to understand), but in a 6wd setup, many teams choose to lower the center wheel so that there can be at most 4 wheels on the ground at any given time. I've found 3/16" offset to be sufficient. Personally, the rocking (tilting) with 3/16" offset was a bit of an annoyance for me. But this was for the Triple Play game where we were trying to place a tetra with a long arm. I'd split the difference between 3/16" and 1/8" and set it at 5/32" (if you keep tolerance on these sort of things to that small). Of course it somewhat depends on what tires/tread you are running. Anything over 3/16" I think would be excessive and anything below 1/8" would be too small.

[Booger]

no no no...Arefin Bari had it right. Im not tilting the wheels im lowering the middle wheel so the robot can tilt

[RyanN]

Originally Posted by Booger

no no no...Arefin Bari had it right. Im not tilting the wheels im lowering the middle wheel so the robot can tilt

We have done this for the past two years with great success. Our
2004 robot had a four wheel design with 4WD, and we had many problems with turning. Our 2005 and 2006 robots
had 6WD with the center wheel slightly lower than our two outer wheels. If you use a pneumatic wheel for the center, you can adjust how offset the center wheel is.

[Madison]

Originally Posted by B. Flaherty

I think what lrdblaster03 is talking is something on ATV's. If you notice in this pic, the front wheels are mounted on an angle. So the real question I think is do you mean lowered wheels as in a 6wd configuration, or do want angled wheels for easier turning?

This is called camber and it's present on most (if not all?) cars as well. Varying the camber can affect the over- or understeer of the car, but I can't see it having any use on a robot that skid steers.

[henryBsick]

Originally Posted by M. Krass

This is called camber and it's present on most (if not all?) cars as well. Varying the camber can affect the over- or understeer of the car, but I can't see it having any use on a robot that skid steers.

What about 116's beautiful implementation of camber (I think that would fit the definition)? They used an extreme angle for their 4 omni wheels in two axis per wheel making the point of the omni in contact with the ground closer to the corners of the physical machine thus providing a much greater footprint for their wheelbase.

I know the middle wheel drop has been established as the thread's intent. I just thought I would throw this out there.

[Dan Petrovic]

Didn't 229 have something similar to this with 8WD? The two inner-most sets of wheels were lower than the front and back set.

[Mike Schroeder]

25 Doesnt lower their middle wheels at all....

[EHaskins]

This year we lower the center wheels about a quarter inch, but also ran a lower pressure in the outer wheels.

[Donut]

60 and 254 both did this for their 2004 machines. Not sure if they still use it but their current drive systems are similar.

[Andy Baker]

Originally Posted by Big Mike

25 Doesnt lower their middle wheels at all....

That's because 25 runs their wheels along the short side of the robot. For robots who run theirs along the long side of the robot, then I suggest a 0.125" to 0.20" drop in the center wheel.

Andy B.

[henryBsick]

Originally Posted by Andy Baker

That's because 25 runs their wheels along the short side of the robot. For robots who run theirs along the long side of the robot, then I suggest a 0.125" to 0.20" drop in the center wheel.

Andy B.

Andy, I agree with you for their 2003 year, but...

03 short side
04 Long side, without full use of entire side due to step pop up mechanism.
05 long side
06 long side

Edit:
Source

[Booger]

i put a 1/4" space between the outside and inside wheels is that enough/too much?

[Andy Baker]

Originally Posted by Henry_222

Andy, I agree with you for their 2003 year, but...

03 short side
04 Long side, without full use of entire side due to step pop up mechanism.
05 long side
06 long side
Edit:
Source

Yes, I spoke too soon. Big Mike AIMed me with a correction also.

Originally Posted by Booger

i put a 1/4" space between the outside and inside wheels is that enough/too much?

In a general sense, I would suggest less. 0.2" should be fine for most cases.

This situation REALLY depends on the robot's Center of Gravity (Cg). Again, generally speaking, a robot with a higher Cg needs more "tilt" difference between the vertical location of the outside wheels and the inside wheel. Robots with a lower Cg will turn OK without a difference, but robots with higher Cg will jump and wobble as they try to turn with no difference.

AB