Robot coming along - slowly - but we are making progress. So we are having a discussion. Our robot will be (hopefully) able to perform all the tasks if everything works out as engineered. Now right now our estimates are that at the low end we can come in at about 70-80 lb (without bumpers and battery), So the question is to run an that weight or slap about 40-50lb of extra weight on it to come close to the 125 lb? Or get it weight multiple times at the competition and be weight flexible based on the needs we believe the next match will require.
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100 pounds is the sweet spot to be able to balance with almost anyone. I’d weight yourself up a bit, but not too much.
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I believe weight should be more or less reduced as much as possible, or at the very least unnecessary weight should be avoided. Though, it is still viable to have a heavy bot for defense. It really depends on your circumstances and how you want to play the game. Personally, being light weight and having good mobility for field traversing is a priority.
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Depending on your climb mechanism, general weight distribution of your robot, requirements on acceleration, you may really want to design extra weight spots in where you can.
For example, our team is definitely adding weight to lower portions of the robot if we have some spare weight (and right now, we do!) because we’ve got a big ol set of flywheels up high on the robot.
@BordomBeThyName 100LBS of just robot weight or is that including battery and bumpers?
Robot weight. It’s a ballpark figure, but 100lbs gives you a bit of leeway to be off-center from your side of the bar a bit, and to climb with robots of differing weights.
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Yep, gotcha. I’d figured, but you know what they say about people who assume things…
Our climb mechanism should be able to handle it either way. But I personally lean more towards light and nimble. Just looking for presenting some pros and cons to the team
My doctor once told me “It’s easier to add weight than remove it”. I don’t think he was talking about FRC, but it seems to apply.
Heavy doesn’t always mean better. 971’s Tachyon was undoubtably one of the best Deep Space robots out there, and it only weighed 92 with batteries and bumpers, where most robots weight around 150lbs in that configuration. If adding weight causes your cycle times to tank, it isn’t worth it. So long as you can coordinate with your alliance partners to get the balance right, I wouldn’t add ballasts.
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Yep, and to build off of this (more realistically, to dial in on one of the things @Maxcr1 is saying here), the lighter your robot, the better your acceleration’ll be, meaning faster cycle times as he said.
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Glad I was beaten to it here; lighter robots can go faster.
That said, I wouldn’t blame anyone for having a couple 5-pound dumbbells to strap onto their robot (or loan to a partner) in some matches for more fudge factor. 2815 used similar weights in 2012 (probably also from a Walmart, we were in a rush) when we found ourselves to be a little tippy on the bridge, and the shape is easy to secure to a robot frame.
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We’re weighing in pretty light right now too, but we’ll be adding weight (steel bar stock attached to the underside of the frame) to bring us up to about 110lbs or so for official weight (minus battery and bumpers) because we see one of our major roles as defensive and want the weight. But we’ll also be using our weight padding to balance our robot for the climb, making sure that the center of gravity is exactly where we want it to be. It will let us smooth out those little variations that otherwise might make getting a balanced hang more difficult.
We weighed last night. We’re sitting just under 95 lbs with everything on the practice robot. The competition robot has a few small differences, plus it’ll have sponsor panels on it, so maybe closer to 100 lbs. We also looked at weight distribution (with bumpers and battery in the robot!), and could be adding 7-10 lbs to the front to balance out the weight for a more level climb. It actually came out a lot more balanced than I expected!
You should never add weight to just add weight. It should always have a purpose. That purpose can be simple though:
Does your robot tip slightly when you accelerate? Add some weight to lower your CG.
Is your robot skewed when it hangs? Add some weight to straighten it out.
We’ve been talking about a scale, but no one has been brave enough to actually bring one to school to weigh the robot.
We go for light, but we don’t work very hard at it.
Depends on your strategy and robot priorities. Do you need to be able to hold your position in a pushing match, either as a defender or against defense? Then weight will increase your normal force and available traction. Are you aiming to optimize for acceleration to shave a second off your cycle time? Lower weight will help increase your acceleration. Do you want to be able to balance with an arbitrary robot on the other side of the generator switch? Then maybe you should aim for somewhere between the two extremes.
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