6 wheel drive with chain tensioners and shifting

[Edoc'sil]

1. Ok, no problem

2. Back wheel is in the output shaft of the gearbox. Traction is connected to both omnis.

3. We had a REALLY bad experience with them this year,we did everything right, lowered the middle wheel and all, eventually remove the plactions farthest from the front, but no mater what we did it was slow forward/back and could not turn. Especially because we ar losing over a third of are team this year due to graduation I wanted to leave the other students with a good, simple, working concept for next year.

4. Upper runs have our electronic mounted on plywood, though it may be redone with pegboard to make wiring neater. I did not include it in the renders because it covered up most of the interesting mechanical stuff.

5. Battery and pnuematic stuff (compressor, cylinders and anything else heavy we can stick down in there) are all mounted just in front of the motors underneath the electronics. Due to the pit we built this year it is quite easy to access the underside of the bot.

6. We didn't include bumper mounts because we have no good guess as to what their height would be and we would like to see what the game is before we really design the entire DT. Likely the vertical portions of flexmation will be extended and a second level to mount the bumpers will be built, but it depends on the game.

7. 1/2 aluminum. Ya, ya it's supposed to be heavy, but its dirt cheep, like 1.20 a foot and we have a CNC mill to mill the squares out easily. Each aluminum panel weighs 1.6 lbs so the weight isn't horrible, and they are fairly robust, similar but larger ones were used this year and we had no problems with durability.

[Edoc'sil]

Just some additional info, in low gear the bots speed is 5.6 fps and in high gear it is 14.3 fps.

Could really use some some additional feedback.

[nnfuller]

1) Why motors in back? if you want the robot to pivot around the center anyway might as well try to focus your weight there?

2) What wheels are you using? Six AM Performance Wheels worked wonders for team 8 this year...

3) why not make it a little faster?

[Edoc'sil]

1. It is preference, it seems to lave a bit more room for other things like electronics and a manipulator.

2. Omnis in the corners plactions in the middle. We would mount heavy components in the middle (battery, compressor) and that combined would the low side to side friction omnis should make us pivot around our center, because you are absolutely right to suggest to make the robot pivot around its COA.

3. Faster then 14 fps? 14 is a jump up from what we did last year, but if other people feel the same I will certainly look at implementing it.


A question then? what kind of fps do people aim for when they are designing a DT?

[nnfuller]

Well having only driven in two years of FRC, I can only speak limitedly on speed. However, when designing a robot you have to look at what you want it to do so the speed you want may be determined by the game... but in my experience, 4 CIMs can easily drive a 6 wheel drive train at about 16 fps, and if your shifting you really don't need to worry about lots of torque in high gear. Especially with the four omni's giving you almost no resistance to turning. In one of our off season bots we had it so that we limited speed through software and we could pull both triggers to open up the full 100% of the speed. Your sacrificing weight for Supershifters, use them to their complete advantage.
Also, Servo or pneumatic shifting?

[Edoc'sil]

Pneumatics, servos suck. With the gearbox being a direct drive I don't think I will try to squeeze out the extra foot or two per second, the best i could do would be change the gearbox from a 9 to 1 to a 7.5 to 1, and that is to little of a reduction.

[M.Wong]

If you really want to shed a ton of weight, switch from 80/20 to 1"x1"x1/16" aluminum tubing. You can easily connect pieces using nylon inserts.

[Edoc'sil]

Do you suppose you could post a link? I am not familiar with the inserts.