Post details of your 2009 robot!

Now that the 2009 season is offically over, post pictures and details of your robots here or on the wiki. Share with the rest of us your engineering skills in the design and construction of your robot.

A good example of what to show and write about is this post Team 254, The Cheesy Poofs where we get good pictures of the robot and some of the important mechanical details.

I’m just gona through out this URl and leave this at that:

Rice Robots focused on accurate & reliable driving by eliminating backlash from gears.

The arms are fairly simple 11.6:1 ratios with emphasis on reliability and control.

Here are all the detail pictures from building weeks,

How did you eliminate backlash?

Directly connect the VEX motor output to the wheel. We had 4 wheels with a motor attached to each wheel. Backlash will still exist on the motor’s internal gears but you are not allowed to modify the internals of the VEX motors.

Gotcha, I was hoping you had figured out a way to eliminate it when you have something geared but I guess not. The only way I know of and this only works real well on arms is to always have resistence. So if the arm is real light you might attach a rubber band or two to put some downward, or upward, tension on the arm.

We found the majority of the backlash comes from the wheel itself - the plastic hole rounds out over time (or maybe we just have really old wheels :().

I think it’s all the square holes and the axle. The axle has the corners rounded so there is a tiny bit of wiggle in any gear or wheel. When you multiply that by 3 or 4 or more axles and square holes you end up with a decent amount of wiggle. If you buy axle from home depot the edges aren’t rounded and although it’s real hard to get wheels and gears on the axle they don’t wiggle nearly as much.

The 5" wheels (and maybe others) even have tiny plastic ridges (initially) in their square holes. When those ridges wear down, the 5" wheels get really sloppy.

Does this mean that they are not identical to true Vex axles and should be banned from competitions (because they offer an unfair advantage)???


You know I never really thought about it that way. In case you are worried though we stopped buying it after the first couple of times because it was extremely hard to use.

They bend and warp really, really easily, so they also offer an unfair disadvantage.

I agree, 1429 showed me a solution using two square hole bar locks around the wheel to prevent the wheel from being rounded out.

Most people should have bar locks.

These also work great on 84- and 60-tooth gears to prevent both slop and slip.

Here was our final solution to our drive system:

We stacked 2 motors and geared them to drive the rear 2 wheels with twin





The way we overcame the need to put any zip ties on our treads was to re-enforce the treads in the center, and put the smaller omni wheels in the front for pickup and disbursement.


We noticed a lot of “grinding” and “crunching” sounds during the competition as robots were lifting and lowering their arms – painful to the ears! While some of the crunching appeared to be part of “normal operation”, in a couple cases, we noticed that it interfered with ability to lift properly. Although our design isn’t particularly original, we thought a couple pages (1 and 2) from our journal might be of benefit to the community.

We had some similar issues, but made a quick fix with a couple of zip ties. It kept the gears together and eliminated all the grinding. THe new heavy duty gears were awesome too.


We regularly install those on our gears (non heavy-duty), and they seem to work fine, so we won’t be buying any heavy-duty gears until IFI releases a 84- or (dare I say) 108-tooth version.

The 60-tooth gears above our drive train that have screws in them are concealing metal bar locks. The 84-tooth gears on the arm do not, since the slider is screwed straight to the gear - the shaft itself is taking minimal strain.

John, your bot is amazing dude. The design is flawless, original and astoundingly effective from what Ive seen…Kudos my friend, your award was well earned.

I will try to edit my post if i ever get any photos of our robot but basically it was as follows;

SymbiOHSis team 2900a

4 motor 4 wheel drive (with all the wheels and motors on each side geared together so that if we lost a motor we would still move) Gear ratio 60t on motor 36t on wheel.

Defensive robot with expandable cube storage on the back that could hold 34+ cubes (for oppositions cubes, you cant score if you have no cubes:p)

Tank tread gathering system to steal cubes off the ground also equipped with a pneumatic cylinder to steal from auto loaders and to score our own cubes in the 3" goals. The treads were powered by 2 directly driven motors.

The treads also meant we could carry around cubes for us to score with using our claw.

Claw, 1 motor lift 60:12 ratio, fixed length claw with horizontal scissor action to open our gripper with a two way pneumatic cylinder.

Big hurty spinny thing; basically a spinning arm mounted horizontally on the back of the open topped cage, enabled us to back up to the oppositions cubes on op of the bonus cube at the start of the match and sweep most of them into the cage (we had already taken 3 of theirs in autonomous mode).

We made it to semis at the worlds in the science division (something that i never would have dreamed to archive)

Looking forward to clean sweep :smiley:

Here goes: we were allied with 2900a (post above) in the elimination matches. Two New Zealand teams in the same semi final in a rookie year :smiley:

6 wheel, 8 motor drive. each wheel has it’s own motor, but with two motors on each of the middle wheels to provide acceleration (yes, really, this thing takes time to speed up). 3 to 1 gear ratio on 4 inch wheels, for crazy speed.

Arm lifted 7:1 on one motor, one motor for gripper, uses auto loaders.

Plus not enough torqu to make it up the center platform, pretty crazy :stuck_out_tongue:

And i got the joy of trying to drive this thing. At least that went well :slight_smile: