Chief Delphi - pic: Whats going on HERE?

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Extra Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=68)

- - pic: Whats going on HERE? (http://www.chiefdelphi.com/forums/showthread.php?t=71842)

Akash Rastogi

10-01-2009 20:49

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798063)

another reason for the swerve drive is that a tank drive wont turn the robot(so we thought why turn the robot, when we could turn the wheels?)

Don't know how you tested that statement but it is quite incorrect.
Tank drive turns just fine for us....not to mention many others.

gorrilla

10-01-2009 20:51

Re: pic: Whats going on HERE?

Quote:

Originally Posted by Akash Rastogi (Post 798067)

Don't know how you tested that statement but it is wrong.

Tank drive turns just fine for us....

on the FRP? with the trailer?

our 2007 robot wouldent turn at all.......maybe its just us....

Akash Rastogi

10-01-2009 20:54

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798069)

on the FRP? with the trailer?

our 2007 robot wouldent turn at all.......maybe its just us....

Yup and yup.

Did you have your weight distributed properly across the entire base and over the four wheels? If not, then that's part of the problem. I'd suggest retrying that before you take a drastic design risk such as this. But that is just a suggestion.

Dominicano0519

10-01-2009 20:55

Re: pic: Whats going on HERE?

you know thats not bad if you use those in the front to start and then kick in two cims after you get some speed to avoid doing a burnout almost like a two speed tranny

let me just take a guess
since cims are designed to continously run and window motors are not i would guess that you are using the cims to run a ball herding mechanism and using the window motors for drivetrain

Dominicano0519

10-01-2009 20:57

Re: pic: Whats going on HERE?

Quote:

Originally Posted by Akash Rastogi (Post 798073)

you could just back up into the trailer and have the bumpers start the turn for you

gorrilla

10-01-2009 20:58

Re: pic: Whats going on HERE?

Quote:

Originally Posted by Akash Rastogi (Post 798073)

yes we did,

we had it in low gear(AM Gen2's) the wheels were just spinning(tried slowly accelerating and getting up to speed and trying to whip it around, to no avail)may be some other factor we're missing?

Akash Rastogi

10-01-2009 21:00

Re: pic: Whats going on HERE?

Quote:

Originally Posted by Dominicano0519 (Post 798076)

you could just back up into the trailer and have the bumpers start the turn for you

Hehe, or that.
Depends on the trailer orientation too.

gorrilla

10-01-2009 21:00

Re: pic: Whats going on HERE?

Quote:

Originally Posted by Dominicano0519 (Post 798076)

you could just back up into the trailer and have the bumpers start the turn for you

we cant get any pool noodles as its winter and there out of season....though when we did back up it jackknifed and made it slowly(SLOWLY) turn around halfway before it got in line with the robot

thefro526

10-01-2009 21:01

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798063)

on the prototype there are(sorry if i dident make that clear)

the window motors are 90pm and the other ones are like 85 so it shouldent make that much of a difference(i hope) any suggestions?

we could also use the globe motors if we have to.....

just what we had lying around is what we used...the final version will absolutely be legal...

another reason for the swerve drive is that a tank drive wont turn the robot(so we thought why turn the robot, when we could turn the wheels?)

Let's put it this way, you might want to write off this design while you still have the chance. This drive train will be very inefficient with two different kinds of drive motors thats aren't linked together to equalize the power. If you really want to build a swerve with window motors as the drive motors then I'd use a coaxial swerve with centralized gearboxes to equalize the output.

Also something else to think about is that your robot is going to travel at about 2fps if you direct drive off of the window motors.

gorrilla

10-01-2009 21:04

Re: pic: Whats going on HERE?

Quote:

Originally Posted by thefro526 (Post 798081)

actually more like 4-6(we actually put them on a 2x4 and clamped them underneath our 2008 robot and drove it on the FRP and clocked the speed....

anyways.....its still a prototype

Akash Rastogi

10-01-2009 21:07

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798086)

actually more like 4-6(we actually put them on a 2x4 and clamped them underneath our 2008 robot and drove it on the FRP and clocked the speed....

anyways.....its still a prototype

Still don't see the point in this design.

This year's game does not benefit from torque...like, at all.

Just explain the purpose of this to me. Thanks.

If you decide to continue with the prototype or follow through with it, then I wish you good luck.

Ian Curtis

10-01-2009 21:07

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798077)

Approximately how far apart are your wheels on the frame? With a 4 wheel drive skid steer, with the wheel centers about 30ish inches apart on the axis on the long dimension, and 22ish on the width dimension, our robot turned. We too had AM Gen2 shifters in low gear. We tried both pinning it and a gradual acceleration. In both cases it turned, although not particularly well. (Gradual acceleration turned better than pinning it)

m^3	10-01-2009 21:08

Re: pic: Whats going on HERE?

We have a 4wd long test base and it turns fine on linoleum floor (no regolith); just make sure the wheels aren't spinning before executing a tight turn. I cut throttle before turning, can easily do a 180+ spin. We don't have a trailer yet but Dave Lavery made a post on here about exploiting the trailer to turn quickly.

Quote:

And don't make a decision too early - a driver with about an hour of practice will learn how to use the Trailer to spin the Robot through turns and pivots with a lot more agility than may have originally been anticipated.

As one benchmark, after a bit of practice I was able to take a standard kit-bot system with trailer attached and run it from one end of the Crater (starting with the Trailer touching the Alliance Station Wall) to the far end, execute a 180-degree turn and make contact with the far wall, and run back to the starting wall in about 12 seconds. This was repeatable several times.

-dave

I think there is a definite advantage to a swerve drive, just questionable whether it's worth it this year and how well this setup would work. edit: our team decided the extra practice time with 4wd would be worth more than time spent designing/building/testing a swerve drive.

thefro526

10-01-2009 21:09

Re: pic: Whats going on HERE?

Quote:

Originally Posted by gorrilla (Post 798086)

actually more like 4-6(we actually put them on a 2x4 and clamped them underneath our 2008 robot and drove it on the FRP and clocked the speed....

anyways.....its still a prototype

If you're using a 6" wheel and your motor spins at ~90rpm like you said then the math says that it should go about 2fps... ((18.84" cicumference) x (1.5rev. per second))/12 = 2.3.... FPS.

But even if thats wrong 4-6fps is still really slow for an FRC field. It would take you 10 seconds or more to cross the field at that speed

Akash Rastogi

10-01-2009 21:11

Re: pic: Whats going on HERE?

Quote:

Originally Posted by thefro526 (Post 798098)

But even if thats wrong 4-6fps is still really slow for an FRC field. It would take you 10 seconds or more to cross the field at that speed

Plus the factor of ridiculously slick wheels.

btw, I checked Dustin's math...and its correct.

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