pic: VexBot V2

[Arefin Bari]

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[MrToast]

Originally Posted by Arefin Bari

Just modified the arm a bit, added the wedge, limit switch, bumper switches...

Not a wedge. An "active bumper system".

Dave

[sanddrag]

You mentioned building a two speed. I actually don't think it would be that difficult at all. Maybe a little expensive. If you got the pneumatic kit for it, I bet it would be fairly easy to hook up a cylinder to a shaft and have it slide the shaft with the gears on it to make a mesh style shifter. You'd just have to make sure you got two different ratios that have the same number of total teeth between the two meshing gears (same c-c distance). Also, with the relatively slow speeds and loads involved, I bet even those plastic gears could stand up to it.

*Afterthough* Aww heck, now that I think about it, since it is on such a small scale you could probably just use an inexpensive servo and linkage to slide the shaft. QUICK, go buy more gears and frame metal!

[Arefin Bari]

Originally Posted by sanddrag

You mentioned building a two speed. I actually don't think it would be that difficult at all. Maybe a little expensive. If you got the pneumatic kit for it, I bet it would be fairly easy to hook up a cylinder to a shaft and have it slide the shaft with the gears on it to make a mesh style shifter. You'd just have to make sure you got two different ratios that have the same number of total teeth between the two meshing gears (same c-c distance). Also, with the relatively slow speeds and loads involved, I bet even those plastic gears could stand up to it.

*Afterthough* Aww heck, now that I think about it, since it is on such a small scale you could probably just use an inexpensive servo and linkage to slide the shaft. QUICK, go buy more gears and frame metal!

You missed the point. There is a way to do it, but not with the parts that is included in 1 vex kit.

... A demo video of this robot is coming soon. Stay Tuned.

[sanddrag]

[quote=Arefin Bari]There is a way to do it, but not with the parts that is included in 1 vex kit.
QUOTE]What, are you trying to get me to go out and buy one? I was thinking you could just go 36-36 and 12-60 on the gearing. Make the 36-36 shaft slide. But I just remembered, mesh shifters need a wide face gear. Nuts. That means you are right. Because the above arrangement leaves you with only two 12 tooth and two 60 tooth gears left.

I bet with an extra set of gears ($13) it could be done. I wonder if the square hole in the gear is consistent with regard to positioning in relation to the teeth. Does anyone know? What I'm getting at is maybe you can just "stack up" a few gears to make a longer gear.

Or if you are going for some good customization (presumably non rules compliant) you could just buy some stuff from sdp-si.

[Arefin Bari]

Originally Posted by sanddrag

What I'm getting at is maybe you can just "stack up" a few gears to make a longer gear.

Or if you are going for some good customization (presumably non rules compliant) you could just buy some stuff from sdp-si.

If you are asking if you could make a long gear like you have drawn in your three speed transmission, I don't think you can. The hub sticks out from both sides of the gear (about 1/8, a guess). You are thinking about a 2 speed mesh shifter using the vex gears and shafts (if I am not mistaking), which would be pretty cool. Unfortunately in order to do that, you would need to order another servo, few aluminum parts (which I bet you can grab from the robovation kit), and gears.

[Arefin Bari]

As I promised before, here is a video of the robot stacking small tetras. Thanks to Alex Pelan for hosting this video for me.

[sanddrag]

Originally Posted by Arefin Bari

The hub sticks out from both sides of the gear (about 1/8, a guess). You are thinking about a 2 speed mesh shifter using the vex gears and shafts (if I am not mistaking), which would be pretty cool. Unfortunately in order to do that, you would need to order another servo, few aluminum parts (which I bet you can grab from the robovation kit), and gears.

Hrrm, forgot about hubs. It's easy to do this with custom parts and modifying parts, but there's got to be a way to do it within the rules (permitting the rules allow additonal unmodified vex parts). I'm going to go try some stuff with legos since I don't have vex. I'll let you know how it goes. I've got a feeling it might not matter if there is a gap in that "long gear" as long as the teeth are lined up.

For the servos, I bet you could do it with one if you keep the two trannies in line. For linkage, I haven't seen all the vex parts but maybe you can use the "wire ties" or "threaded rods"

[Arefin Bari]

Originally Posted by sanddrag

Hrrm, forgot about hubs. It's easy to do this with custom parts and modifying parts, but there's got to be a way to do it within the rules (permitting the rules allow additonal unmodified vex parts). I'm going to go try some stuff with legos since I don't have vex. I'll let you know how it goes. I've got a feeling it might not matter if there is a gap in that "long gear" as long as the teeth are lined up.

For the servos, I bet you could do it with one if you keep the two trannies in line. For linkage, I haven't seen all the vex parts but maybe you can use the "wire ties" or "threaded rods"

You got a point and you are right. Yes, there is a way to do it, maybe you have to make some custom parts (small linkages and such, which is not hard). Tell you the truth, I don't think the gap between the gears will really matter. Just like Jaine pointed out, you can always sand the hubs down.

[Jaine Perotti]

Originally Posted by Arefin Bari

As I promised before, here is a video of the robot stacking small tetras. Thanks to Alex Pelan for hosting this video for me.

The video is great, Arefin! You have done a wonderful job on this project. I don't know how you have managed to pull this of in the midst of all the work you are doing for your offseason. I am quite impressed. I only wish I could do half as good a job on the projects i take on independantly (lol).

Awesome job,

-- Jaine

[sanddrag]

You've really got me interested now. I want to see a shifting Vex bot. Maybe instead of shifting gears, you can shift wheels. I bet you could do that with the parts from one kit. You could maybe slide a gear that either engeages a shaft which a small wheel is on or a shaft which a large wheel is on. For example when the gear is mating with the gear on the large wheel shaft, the small wheel shaft freewheels.

Anyone with a Vex kit willing to try it?

I was even thinking of raising and lowering wheels. But you'd have to raise and lower both sets (large and small) which would be hard with one servo.

[Arefin Bari]

Originally Posted by sanddrag

I was even thinking of raising and lowering wheels. But you'd have to raise and lower both sets (large and small) which would be hard with one servo.

I was just thinking the SAME thing. Tell you the truth, it wouldn't be that hard with one servo motor (modified motor is better). The arm that I have right now picks up the whole robot. I use the arm to climb up things which is pretty fun to watch. It might be a problem since only small wheels are there in a set of 4, other wheels are different sizes. There are 2 medium wheels and 2 large wheels. You can find all the parts that come in a vex kit on their site.

[sanddrag]

You could have a robot with two small wheels and two big wheels and they are geared with the same ratio except when one is engaged, the other is disengaged. All 4 would always be in contact with the ground but yu'd only have 2 wheel drive at any time.

Anyway, I just tried mesh shifting with lego gears and it is flawless. The + shaped holes in the lego gears are extremely consistent with positioning with respect to the teeth. The gears are probably totally molded and it is all the same operation. I don't know if the Vex gears are made that way. Can you confirm or deny if the teeth line up when gears are next to each other? The Lego gears have a good amount of backlash which makes shifting easy; I'm not sure how much Vex gears have. The "gap" in the long gear will not be a problem at all because going over that gap is just like mesh shifting.

Now you are really making me want one of these Vex doodads, but although it is an extremely good deal, it is still a good chunk of money.

[tiffany34990]

well good job my friend... and i dont' see how you needed my help to figure this stuff out..you can always handle all of this stuff...

how about the next step making your tetras look better

and the next kit most def. surely you we all can come up with multi speeds... it's just the first generation....always more to come...as the always say...rome wasn't built in a day....

great job again Arefin...

[Arefin Bari]

Originally Posted by tiffany34990

well good job my friend... and i dont' see how you needed my help to figure this stuff out..you can always handle all of this stuff...

how about the next step making your tetras look better

and the next kit most def. surely you we all can come up with multi speeds... it's just the first generation....always more to come...as the always say...rome wasn't built in a day....

great job again Arefin...

I thought that I wouldn't have a chance to play with the vex kit until a day or 2 before the offseason, because I need a demo bot there. But, I did have the chance to go over the manual myself which is why I didn't ask you for help anymore. I thought I would be in a rush to build this. But I do appreciate your willingness to help me.