pic: Team 100 Prototype/Practice Bot

You may recall this thread.

Cost: $400
Time: 4 Days*
Weight: 25 lbs. with motors, 14 lbs. without motors

Electronics are currently on a separate board for testing. They’ll go on when the programmers are ready.

*Most of the students had never used machine tools before.

You might want to double up the omni wheels in the front or go with different omnis. If there are large gaps between the rollers on the omniwheels then you’re in for a bumpy (and noisy) ride on hard surfaces. It might not be so bad since you have 4 other wheels, spreading the load. Nice frame though.

Nice frame! You may want to consider gusseting it a little… I don’t know how the strength is, but triangle braces for instance would help protect it from damaging impacts
Also, I don’t know how your traction is, but if you need more, a real easy way is to get higher traction wheels for the 4 non-omni wheels.
Overall looks good!

I would also second the gussets. Team 971 did a similar type of frame with 80/20 in 2006. We were fine at SVR, but over the course of the competition the frame had gotten so whacked up that we didn’t fit in the size box at champs.

On the omni wheel note, while more rollers are better and offer a smoother ride, they’re not essential. As long as everything is tightened down well, you shouldn’t have any problems. Team 190’s custom omnis last year weren’t exactly the smoothest ride (5"od, with 10 evenly spaced 1-1/4" rollers. I don’t have a good picture), but they held up for 2 regionals and champs, and it wasn’t noticable when the robot was on the field.

I can’t tell what size chain you’re using, but you should pay close attention to whether the wheels are aligned perpendicular. #35 is more foregiving, but even that will get thrown if the axle blocks aren’t aligned well enough.

The electonics board is a 1/2" thick peice of baltic birch that fits down snug in the bottom. This will prevent it from twisting.

We also bolt some thin plates onto the 80/20 between the omnis and center wheels to prevent the frame from being crushed in on the sides.

We’ve intentionally left these things out to make it more adjustable for the build season. The competition bot will be tougher.

As for the omnis we’ll have to wait and see the game before we decide if smooth rolling is important (only have to wait 24 hours :ahh:). We have some double-wide Kornyak omnis if they are needed.

This is a very adjustable system. We can mount the wheels on one side for 2.5" of ground clearance (perfect for ramps), or on the other side for .5" of clearance (perfect for flat fields). We can also mount 6" wheels or even meccanums if we’re so inclinded (need to build two more trannies in that case).

where did you get those omni wheels?

(EDIT) nvm… searched google…

Single stage reduction of , what, 3.7:1? 4 CIMs direct driving what look to be 5" wheels. With electronics, no more than 50Lbs. We are talking some serious speed!!! :yikes:

I know this is a practice bot, so my suggestion is; Practice, Practice, Practice!

If you read the specs on the other picture, Martin says it clocks in at 11 fps, which isn’t all that fast. There is a chain geardown off of the transmission that accounts for the rest of the reduction.

Total reduction is 7.1:1, with 4" wheels that’s 10.89 fps. A very reasonable speed for a 1-speed robot in my experience.

I agree with you on the practice part. Considering our Freshman driver drove Ballfrog better at CalGames then I ever did, who knows what he’ll be capable of with a little practice :eek: