29-04-2007 22:38

Aren_Hill

Re: pic: A more standard aproach

Are you sure you want to commit 8motors to your drive train? ours the steering was all linked so we could tank steer which only took 5 motors you have that option by replacing all of the banebots with sprockets and have 1 motor drive them. I know las guerillas (469) went the 8 motor route and it was pretty crazy to watch.

amazing weight too especially for a swerve drive

30-04-2007 07:33

Al Skierkiewicz

Re: pic: A more standard aproach

I agree with Aren, although we use two Globes for steering. I would stay away from the Banebot transmissions that appear in the steering motors. They might not be able to handle the rough treatment when your robot gets hit from the side or bangs into something.

30-04-2007 07:52

Qbranch

Re: pic: A more standard aproach

FIRST off, if you need any help with G-Code programming or machining in general just hit me up...

I'm wondering... does that 64:1 gearbox with the mabauchi motor have enough torque to turn the wheel under load?

A suggestion to save weight, for 1/8" polycarbonate you can use a large pop rivet to save weight as well, not to mention the higher population of fasteners will more evenly distribute the forces on the stiffening plate over a larger portion of its perimeter.

Very nice lightweight design, have to say, amazed that all those gears for four wheels only weigh 35lbs.

-q

30-04-2007 07:59

Rich Ross

Re: pic: A more standard aproach

Any particular reason why you ditched the suspension? I think some teams have built suspensions in previous games... (i know a former mentor does but i don't have the link) I'm pretty sure its possible to do with a couple long pieces of shaft.

30-04-2007 08:42

whytheheckme

Re: pic: A more standard aproach

Quote:

Originally Posted by Alex.Norton loading photo ...

30-04-2007 11:09

Alex.Norton

Re: pic: A more standard aproach

I'm using 8 motors in the drive for a couple of reasons. I like the idea of the extra maneuverability and control that is provided, i know that this is more complicated program wise but it is less complex mechanically and is lighter. Two motors weighs less than a chain tensioner plus chain and sprockets. Mechanically it is much easier cause I don't have to mount everything separately and all the pieces are the same and there are fewer of them.

The motors would be two Fischer Price and two BaneBots (don't know if we have all these next year so...). I'm pretty sure that the trans could handle the load because there is a bearing at the bottom that all upward force and most lateral force would go into. I would worry a little about the carrier plate but if the modules are well protected I don't think it would be a huge problem.

I got rid of the suspension cause of weight and the suspension is really complicated. I really liked the idea but it didn't seem needed for an actual first robot, plus this is much lighter and more importantly costs about half as much. The wheels cost $2.75 each instead of $100 each. And when I say "that which is shown" I forgot that I was only showing half of the bot. The entire thing, modules, motors, frame, everything weighs only 35 pounds. Of course with electronics this could be 10 pounds heavier but that still leaves much more than half the allowed weight to build on top of.

Orders... jee hadn't thought of that.
Thanks for the offer of help but I think I can handle it, however if I do need help. If you would like to CAD files just ask.

Thanks very much for all the input.

30-04-2007 11:36

Al Skierkiewicz

Re: pic: A more standard aproach

Alex,
One thought I had after my intitial post is the problem of keeping the steering motors in alignment. It is an issue using two motors and chain for us. To keep all four tracking is going to take some processing power and sensors.

30-04-2007 21:54

Dave McLaughlin

Re: pic: A more standard aproach

Just out of curiousity, how do you keep the wires on the drive motors from tangeling around the sverve module?

30-04-2007 22:24

Al Skierkiewicz

Re: pic: A more standard aproach

Quote:

Originally Posted by Dave McLaughlin Just out of curiousity, how do you keep the wires on the drive motors from tangeling around the sverve module?

30-04-2007 23:04

Alex.Norton

Re: pic: A more standard aproach

I was actually worried about how to keep the tubes in alignment. I was thinking of adding some sheets to the frame that would brace between the tubes vertically. And now that you mention it that is another good reason to use four motors, there is again less precision needed. While I do need precision to attach the motor mounts, I can think of an easy way to do that.

In this case since the module turning comes down through the top I can't run the wires through the bearing. I would run the wires up the inside of the module and then leave a large loop of wire to allow for turning before attaching directly above the module. I would also limit the turning of the module to keep the wire from tangling.

01-05-2007 20:29

tdlrali

Re: pic: A more standard aproach

char encoder_turns(int pot, int last, int window) {
    if(pot - last > 1023 - window)
        return -1;
    else if(last - pot > 1023 - window)
        return 1;
    return 0;
}

01-05-2007 21:44

DonRotolo

Re: pic: A more standard aproach

Seems to me that window lift motors - or a similar worm drive system - might be better for the steering motors. They rotate slowly - but maybe not slow enough - and have significant torque, and take the bumps pretty well. Plus, they are available cheap in surplus and reasonable in new.

Some newer types sometimes have integrated quadrature sensors (used for detecting objects during auto-close of the windows) that are sensitive and can be used to maintain steering alignment (along with a 'home' switch for recalibration).

Some idle thought, is all.

Don