# Motion of rotating and sliding metal bar for robot combat

• cjk2
In summary, the conversation discusses a novel idea for a robot combat weapon that involves spinning a metal blade with a rounded slot cut off center. The blade would slide when bumped, causing an unbalanced and larger effective radius. However, there is a problem with the blade not sliding enough in the short time it has before hitting the enemy robot. The conversation also mentions the weight and dimensions of the blade, as well as the attempt to solve the problem using a formula.

#### cjk2

For those who don't know there exists a sport called robot combat. Two robots enter an area and fight until one is unable to move anymore or its owner taps out. I have a novel idea for a weapon for a robot but I am unsure if the maths works out so that it will be practical.

Here is the problem: I built a prototype of this device and it seems that sometimes the blade does not slide much in the half a revolution it has before it hits the enemy robot. At 12000rpm the blade only has 0.0025 seconds between initial tap and huge whack. Suppose the blade is initially knocked in 0.01 inchs with respect to the hub. If the blade weighs 60 grams how far will it advance in the 0.0025 seconds before the business end makes it half a turn around that hits the other robot? I suspect for my purposes some simplifications to the problem can be made as I do not need absolute accuracy. For example we can probably assume the speed of the blade does not vary and the tips of the blade always see 10000G.

The blade is 6 inches long, 0.094 inches thick and 1 inch wide. It weighs about 60 grams and is made of carbon steel. It does have some holes it it make it lighter but they are not near the ends.

I hope I have explained this well enough to be understood. Please see the attached drawing for additional clarification.

My attempt to solve this problem so far has been met with failure. I tried to approximate a solution using the formula D=0.5*a*t^2 but this does not account for the fact that as the bar slides the imbalance becomes greater and greater. I suspect the solution will have a t^3 term in it. I think this problem is similar to a situation where a weight is dropped but the gravity becomes stronger the further it falls.

http://i.imgur.com/iDdQ4z5.png

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I just attempted a solution but am not sure it is right.

I calculated that 0.25mm of displacement of the blade causes about 20 Newtons for force. This means that F = 80000 Newtons per meter displacement. Let's called the displaced distance W. Then F = 80000 * W. We know that F=MA. So W*80000=MA. But A = W'' (right?) and M = 0.06 KG So W(t)*80000=0.06*W''(t). I plugged that into wolfram alpha and asked it solve for W(0)=0.00025 and W'(0)=0. The result is W(t)=e^(-1154.7 t) (0.000125+0.000125 e^(2309.4 t)). This seems somewhat realistic. For example if t = 0.0025 seconds for half a revolution then W = 2.2mm. This roughly agrees with my experiment.

## 1. What is the purpose of the motion of rotating and sliding metal bar in robot combat?

The purpose of the motion of rotating and sliding metal bar in robot combat is to create a powerful and effective weapon that can damage or disable the opponent's robot. The rotating motion adds momentum and force to the bar, while the sliding motion allows for more precise and targeted strikes.

## 2. How is the motion of the rotating and sliding metal bar controlled in a combat robot?

The motion of the rotating and sliding metal bar is controlled through a motor or servo attached to the bar. This motor or servo is controlled by a remote or programmed instructions, allowing the operator to control the speed and direction of the bar's motion.

## 3. What materials are typically used for the rotating and sliding metal bar in robot combat?

The rotating and sliding metal bar is typically made of a strong and durable material such as steel or aluminum. These materials are able to withstand the impact and force of combat without breaking or bending.

## 4. How does the motion of the rotating and sliding metal bar affect the overall performance of a combat robot?

The motion of the rotating and sliding metal bar greatly affects the performance of a combat robot. It provides a powerful and precise weapon that can cause significant damage to the opponent's robot. The motion also adds maneuverability and versatility to the robot, making it more competitive in combat.

## 5. Are there any safety concerns or regulations regarding the motion of rotating and sliding metal bar in robot combat?

Yes, there are safety concerns and regulations regarding the motion of rotating and sliding metal bar in robot combat. These include ensuring that the bar is securely attached to the robot to prevent it from flying off and causing harm, as well as adhering to weight limits and design guidelines set by the competition organizers. It is important to follow these regulations to ensure a safe and fair competition for all participants.