Robot Weight

[crimsonjake]

Just wondering how many teams will be shooting for the 120 weight limit! With the bridge being as tight as it will be with either 2 or 3 robots, I was thinking that all the robots on the alliance will need to be relatively the same weight.

[Polaris395]

I think it will be pretty safe to assume that everyone is +/- 10 pounds from 110lbs.

[crimsonjake]

That's what I'm hoping. With the point value of 3 robots on the bridge in the elimination rounds it could be a game-changer, but the bridge size may hold a lot of alliances back. Even if all the robots on the alliance are built "the short way," balancing will be hard to coordinate unless they are all weighted the same. I haven't done the calculations as to how much leeway we get, but I'm assuming it is pretty small.

[AlecMataloni]

Where's the "drill enough weight holes so we're barely under 120lbs" option?
;-)

[MrForbes]

We're shooting for making the "upper" part of the robot as light as possible, and we're not concerned about the bottom part. But we'll make sure it's less than 120 on bag day

[Jon Stratis]

It might not be a bad idea for a team to make their robot weight adjustable. Have some way to increase/decrease your weight by ~1 lb increments so you can match your alliance partners. "Our weight is adjustable. Robot A goes in the middle, we'll go opposite robot B and we've already calibrated our weight to 117lbs to match". Say that to a potential alliance before eliminations, and it could sway them to picking you!

[rsegrest]

We're with Squirrel. Low center of gravity is going to be critical when traversing the ramp so as long as our weight is at the bottom of the bot we're happy. Probably going to be close to the 120 but not neccessarily shooting for right at it.

[crimsonjake]

Another thing that could play a factor (a very, very small factor) would be the unequal distribution of weight upon each wheel.

i.e. the front of the robot has more weight on its wheels than the back.

Just to keep in the back of your mind!

[Pjohn1959]

Where's the "drill enough weight holes so we're barely under 120lbs" option?
;-)

Or: "My hacksaw is my best friend..."

[Aren Siekmeier]

We'll build the entire robot as light as possible, then add solid steel to very bottom until we hit 120.

[Phyrxes]

We are going for the holesaw and sawzall it down to 120 but keep the CG as low as possible.

[MrForbes]

Another thing that could play a factor (a very, very small factor) would be the unequal distribution of weight upon each wheel.

i.e. the front of the robot has more weight on its wheels than the back.

We'll definitely do this, we will rearrange where things go to keep the center of mass centered between the front and back. Side to side is not too much of an issue....since we're planning a "wide" robot.

[Taylor]

As we understand this game, it's about speed. We'll keep our robot as light as possible. With a 35x27 frame and 8" wheels, we ought to be able to 'spin' on the bridge and change our orientation to perpendicular to the bridge, allowing our partners to climb up on the ends.

[Flimsor]

We'll be shooting for lower than 120 but you always seem end up at the limit.

[DarkByakko]

Our team is on the fence with this. Assuming the majority of the teams competing are shooting for a weight near or equal to 120 lbs, we're more comfortable trying for a heavier bot due to the inevitable fact that if there are more heavy bots competing, a light bot would be pushed around.

We had this problem in the last competition, wherein our bot was lighter than the others, and the other heavier bots tended to push ours right out of the way.

It's a hard decision to make; sacrifice endurance for speed, or increase the weight for steadier shooting at the cost of a slower robot.

[Andrew Lawrence]

We're aiming for 120. That way since most teams are around that weight, it'll be easier to balance the bridge. Only thing now is to start drilling holes! :p Actually, we may come in a littl under this year. We'll then need to pack on extra stuff to get to 120!

[MrForbes]

We're aiming for 120 and on course for 130 :)

Bare frame, pretty much complete with all the mounting brackets for everything, is 27 lbs.

[Mr. Rogers]

We're at 118 lbs, but a few small components still need to be added. That's too bad, now we'll have to water jet our logo out of some parts of the robot. :rolleyes:

[thefro526]

I think it will be pretty safe to assume that everyone is +/- 10 pounds from 110lbs.

This is a dangerous assumption to make, IMO. Last year, there were 'competitive' robots as light as 90lbs without bumpers and batteries. This year, I'd imagine that there will be a robot or two at each event that are well underweight.

Personally, we're shooting for as low of a weight as is reasonable with the intent of being able to ballast ourselves (method tbd) up to the weight that balances best with our partners, though some testing that teams have done may have proven that this might not be needed.

[davidthefat]

Our drive alone is 86 lb... I am worried...

[Grim Tuesday]

Our drive alone is 86 lb... I am worried...

That is actually something to be worried about. Ours was ~65 last year, and we had dual layers of T-Slot and tubing, along with 8 idlers and tank treads. This year, we're down to ~50, after beginning the transition to sheet metal construction by water-jetting our side panels out of 3/16th plate. What are you guys doing that requires 86 lbs? Unless its two drive trains for going X and Y, you might want to get out the drill.

[davidthefat]

That is actually something to be worried about. Ours was ~65 last year, and we had dual layers of T-Slot and tubing, along with 8 idlers and tank treads. This year, we're down to ~50, after beginning the transition to sheet metal construction by water-jetting our side panels out of 3/16th plate. What are you guys doing that requires 86 lbs? Unless its two drive trains for going X and Y, you might want to get out the drill.

I warned everyone about it, but they went with the 14 inch wheels. In order to support those 14 inch wheels, one of our mentors had to make a brace for the sprocket. In order to chain them up, 4 big metal plates are required for the gearboxes. It is slow, sluggish and cumbersome. It was designed to to over the bump, but it flips over.

[Hawiian Cadder]

That is actually something to be worried about. Ours was ~65 last year, and we had dual layers of T-Slot and tubing, along with 8 idlers and tank treads. This year, we're down to ~50, after beginning the transition to sheet metal construction by water-jetting our side panels out of 3/16th plate. What are you guys doing that requires 86 lbs? Unless its two drive trains for going X and Y, you might want to get out the drill.


I second this, our 2012 robot was 78 lbs with the drive-train, and while making weight wasn't all that hard It was very limiting to us and caused a lot of stress. I would try to cut weight wherever you can, learning from last year we managed to got our 2012 robot down to 51 Lbs without any worries about structural strength. If you need more than 30LBS for a frame, you are doing something wrong.

[Andrew Lawrence]

That is actually something to be worried about. Ours was ~65 last year, and we had dual layers of T-Slot and tubing, along with 8 idlers and tank treads. This year, we're down to ~50, after beginning the transition to sheet metal construction by water-jetting our side panels out of 3/16th plate. What are you guys doing that requires 86 lbs? Unless its two drive trains for going X and Y, you might want to get out the drill.

Our drive this year along with our ball sucker and motors are about 48 pounds, and our ball elevator and shooter are about 50, leaving us about 30 pounds for our bridge manipulator. :)

[BJC]

We weighed in at 97.5lbs tonight with mostly everything. We'll probably be at least 110 before everything is on then we'll slap a 9.4lbs steel bellypan on the bottom. :rolleyes: But seriously, I'm pulling for it..

In any case, we'll be 119.9lbs like every year by the time we bag it.

[DampRobot]

Our team typically doesn't try to make it's robot exactly 120 pounds--it just sometimes ends up that way. However, when the robot it underweight (ie more than a few pounds below 120) we don't go out of our way to add weight.

Remember, although it is true that a heavier robot is harder to push around, a lighter robot has a number of advantages. A lighter robot can accelerate and travel a lot faster, is easier to turn, and is more maneuverable. I've heard that 254 keeps their robot at 90lbs for the extra performance.

Edit: Thats 120, not 1220 lbs. Thanks SuperNerd

[Andrew Lawrence]

Our team typically doesn't try to make it's robot exactly 120 pounds--it just sometimes ends up that way. However, when the robot it underweight (ie more than a few pounds below 1220) we don't go out of our way to add weight.

Remember, although it is true that a heavier robot is harder to push around, a lighter robot has a number of advantages. A lighter robot can accelerate and travel a lot faster, is easier to turn, and is more maneuverable. I've heard that 254 keeps their robot at 90lbs for the extra performance.

Well I hope your robot us under 1220! :p While a light robot has its obvious advantages, heavier robot's advantages are often overlooked. The huge one (pushing power, and harder to push) are not the only advantages of being exactly 120 pounds. A great example is this year. If both robots are 120 pounds (most of them will be), then it'll be much easier to balance on the bridge verses a 120 pound robot and a 90 pound robot (Not saying 254 shouldn't pick us if they're going for 90 pounds. We'd work great together in the elimination rounds! :D)

[pfreivald]

Our drive train, including electronics and pneumatics, is ~80 lbs. Piling on every component we think we're going to need we get to 107 lbs. Assuming some additional support struts and little wibblybits we haven't made yet and some lexan side panels make up the rest of that weight, we're on target for 120 lbs, maybe a little less -- which we will make up for with ballast.

One goal for us is to keep our CG in the very, very center of the horizontal cross section of the robot and at or below the plane of the frame -- and it looks like that's going to happen!

On a side note, I don't buy that 90 lb robots are inherently faster than 120 lb robots. Depending on the drive train, acceleration can be torque-limited or traction-limited, speed depends on gearing, and turning ability depends on a whole lot more than weight.

[Akash Rastogi]

Our drive this year along with our ball sucker and motors are about 48 pounds, and our ball elevator and shooter are about 50, leaving us 30 pounds our bridge manipulator. :)

Just incase you end up messing yourself up on robot weight, I should point this out now.
http://blogoscoped.com/files/google-math-poster.png

[Andrew Lawrence]

Just incase you end up messing yourself up on robot weight, I should point this out now.
http://blogoscoped.com/files/google-math-poster.png

lol. As for the math, 48 + 50 = 98. That means we have about 30 pounds for our bridge manipulator, though it won't weigh that much.

I put in the about to make it more accurate. 50 + 48 + 30 ≠ 120, but 50 + 48 + 30 ≈ 120

[Dancin103]

We put the bot on the scale yesterday and without one small thing, ironically, it weighed 103. :)

[AcesJames]

We're sitting at about 62lbs right now. That's the rolling chassis (wheels, chains, motors, gearboxes, axles), super structure, and bridge manipulator mechanism. We've still got to add the elevator assembly, shooter, and some more electronics. I think we're looking at about 115lbs total.

[Aren Siekmeier]

Now that the CAD is finally reflecting most of the robot's features (still a gearbox or two, some small frame members, etc. to add in) we're sitting at 82lbs with drive, bridge/bump crossing, ball intake/storage, and shooter. Haven't checked that the mass properties are all set properly, and of course there's more to be added in, so I'd put us at 100lbs when it's all said and done. And then of course we'll be tossing in 20lbs of steel for good measure.

Not worried about passing inspection in that regard at all. Or the size constraints for the matter...

[c.shu]

As we understand this game, it's about speed. We'll keep our robot as light as possible. With a 35x27 frame and 8" wheels, we ought to be able to 'spin' on the bridge and change our orientation to perpendicular to the bridge, allowing our partners to climb up on the ends.

With over 120lbs on one end of the bridge, how can the third robot even attempt to lower the other end of the bridge? Unless you can easily be pushed sideways I dont see this as a possible solution.