Scioly.org

to: gh

do you mind sharing what company/where you ordered the planetary gear boxes you used in your bot harpy? the only source i have been able to find has been those sold at bane bots, and those are too heavy for my tastes.

MoneyMonger wrote:to: gh

do you mind sharing what company/where you ordered the planetary gear boxes you used in your bot harpy? the only source i have been able to find, has been those sold at bane bots, and those are to heavy for my tastes.

Using a prebuilt kit is not the best way to go.
I made my robot from scratch, and we got first at regionals. We beat all of the kit builders.

I think the ring should be set at 6 by 6. Do you?

paleonaps95 wrote:

MoneyMonger wrote:to: gh

do you mind sharing what company/where you ordered the planetary gear boxes you used in your bot harpy? the only source i have been able to find, has been those sold at bane bots, and those are to heavy for my tastes.

Using a prebuilt kit is not the best way to go.
I made my robot from scratch, and we got first at regionals. We beat all of the kit builders.

I think the ring should be set at 6 by 6. Do you?

please excuse my vagueness however i was not asking for any info on a kit but on where to acquire gearboxes that are as of the moment instrumental for a few ideas i have to come to fruition.

in regards to the size of the ring, this is the first year that sumo has been a trial event in my state so my experience is VERY limited. However it appears to me that a larger ring allows more tactics to get involved rather than just head on pushing. but again remember my experience is very limited and therefore should be taken with a grain of salt.

Oh, you wanted the specific gearboxes I had. Well, that's kind of an issue, because they've been out of manufacture for I'd say 3 years now (they were passed down to me, heh). At that time, BaneBots also manufactured inline aluminum-cased 550 gearmotors like that as well, but of course they have the square gearboxes now. I got mine from Lynxmotion (link).

I'd say that my motors were fairly oversized compared to those of the vast majority of the competition, and didn't really make my bot better. They were capable of delivering enough torque that the driving force at the tires was about 10 times what the tires themselves could push without slipping (given the 2009 rules' 2.5kg), so there was just way more power than I needed. Their size and weight precluded the design having four wheels, which I rather wanted. Also, I had to make some completely ridiculous wheels that swept over the gearhead in order for the wheels to not exceed the max width requirement.

If you decide you want motors of similar power, Robot Marketplace has some in the same ballpark... ish. Hard to find motors that great these days. :)
http://www.robotmarketplace.com/products/0-B16.html
http://www.robotmarketplace.com/products/0-BPK27.html

Also, some individuals doing FIRST mentioned to me that my gearmotors had some resemblance to Fischer-Price planetary gearheads or gearmotors that were popular in FIRST a few years back. I don't know what that's about.

I can also vouch for the Maxon 17:1 gearmotor, a specific combination of Maxon motor and 17:1 gearbox that was popular with robot people... also a couple of years ago. Actually, just pretend all the advice I give is outdated. Anyways, this motor is freakish fast, very light, and quite efficient: link. You would need at least four of these; they're still plenty available on eBay. They're used quite successfully in 500g autonomous sumos (eg ExSpurt) and in beetleweight BattleBots.

As for the ring, I like to show this video to anyone getting started: http://www.youtube.com/watch?v=gIYMAymGzdI

It's the way all non-SO sumo bot competitions are done (though American robot sumo is extremely tame in comparison to what's in the video). Note that the ring is circular and raised far off of the ground so that robots falling off is very obvious and there's no way for them to get stuck at a corner of the ring. It's also black and white, so as to allow autonomous builders to have a fighting chance. In fact, if our rings were like that, I probably would have built autonomous behavior into my bots to help with the reaction times.

Also note that the robots start close to the center of the ring, but with room in every direction to maneuver. This makes the first move kind of Russian chess-like; you have guess what your opponent's first move is and try to come up with a counter that seems logical.

is it better to have 4 wheels, 2 wheels or 6 wheels?

iYOA wrote:is it better to have 4 wheels, 2 wheels or 6 wheels?

The more wheels, the more friction, the better. You don't need six separate motors, but having extra wheels on each axle will help a lot.

It's a tradeoff.

More wheels mean that less weight rests on the scoop. The scoop does not contribute to pushing power, so weight resting on it is weight wasted.

Having more wheels generally means that you will have wheel slip when turning. This happens when the wheel isn't pointing in the same direction as its motion, such as in a four wheeled robot turning about its center. All wheels are pointed forward or backwards, but their direction of travel is tangent to circles centered at the turning point.

Either will contribute to significant loss of pushing force; the first for obvious reasons and the second because it will cause the wheel and the ground to engage in kinetic friction instead of the static friction of a wheel rolling on the ground.

gh wrote:It's a tradeoff.

More wheels mean that less weight rests on the scoop. The scoop does not contribute to pushing power, so weight resting on it is weight wasted.

Having more wheels generally means that you will have wheel slip when turning. This happens when the wheel isn't pointing in the same direction as its motion, such as in a four wheeled robot turning about its center. All wheels are pointed forward or backwards, but their direction of travel is tangent to circles centered at the turning point.

Either will contribute to significant loss of pushing force; the first for obvious reasons and the second because it will cause the wheel and the ground to engage in kinetic friction instead of the static friction of a wheel rolling on the ground.

The loss incurred by having lots of wheels can be lessened by good driving, but good driving can't do anything for a scoop with too much weight on it.

i am not in NY but this sounds awesome! its like the one show that Grant Imahara won (i think i spelled his name wrong) Robot Wars i think, but div C in California also get really lame trial events..