Scioly.org

The University of Michigan Invitational put together a video with highlights from their Invitational. There are 2 mousetrap vehicles shown. The first vehicle shown took first place.

viewtopic.php?f=267&t=11006&start=60

Hey, sorry if this has been asked before: could someone explain to me more in depth about how the first place car in 2010 works?

Ten086 wrote:Hey, sorry if this has been asked before: could someone explain to me more in depth about how the first place car in 2010 works?

Was just about to ask the same question lol

PM2017 wrote:

Ten086 wrote:Hey, sorry if this has been asked before: could someone explain to me more in depth about how the first place car in 2010 works?

Was just about to ask the same question lol

I believe that ideally, you want the string to "wrap" through the path of the tip of the lever arm; The tip of the lever arm traces an arc through the air. AFAIK currently the maximum usable string length is 2x the length of the lever arm.

However, if you can get the string to pass through the arc (think of instead of a lever arm, there's a huge disc with a radius of the lever arm, and the string wraps around the edge of the disc) then the usable string length is lever arm * pi, giving you about 150% more length.

They added in extra lever arms to more closely approximate that disc; as the first lever arm reaches 60 degrees, it snags the next lever arm, and so on.

Also, this makes it so that the torque from the mousetrap's spring is more directly translated into a force pulling on the string; as the lever arm gets further away from the drive axle, less and less of the mousetrap's force goes into pulling the string.

killer225whale wrote:

PM2017 wrote:

Ten086 wrote:Hey, sorry if this has been asked before: could someone explain to me more in depth about how the first place car in 2010 works?

Was just about to ask the same question lol

I believe that ideally, you want the string to "wrap" through the path of the tip of the lever arm; The tip of the lever arm traces an arc through the air. AFAIK currently the maximum usable string length is 2x the length of the lever arm.

However, if you can get the string to pass through the arc (think of instead of a lever arm, there's a huge disc with a radius of the lever arm, and the string wraps around the edge of the disc) then the usable string length is lever arm * pi, giving you about 150% more length.

They added in extra lever arms to more closely approximate that disc; as the first lever arm reaches 60 degrees, it snags the next lever arm, and so on.

Also, this makes it so that the torque from the mousetrap's spring is more directly translated into a force pulling on the string; as the lever arm gets further away from the drive axle, less and less of the mousetrap's force goes into pulling the string.

couldn’t have said it better myself. My initial design involved an arch that would support the string as the arm moved in the arc, but it would have added too much weight. I tried a single extra arm and it ended up being basically the same speed as when I ran without it.

The benefit of the compound arm is mostly more distance, and a single arm is more than sufficient for this year’s distance. Not only that but the reversal evens out a lot of the time advantage it would give. It’s a better idea to try and reduce unnecessary weight and optimize the other parts of the vehicle.

4Head wrote: couldn’t have said it better myself.

That's why he's the National Event Supervisor for this event

I miss EV and the nice smooth floors we ran on: http://www.lmsal.com/pub/markn/EV-NorCa ... onship.mov

mnoga wrote:I miss EV and the nice smooth floors we ran on: http://www.lmsal.com/pub/markn/EV-NorCa ... onship.mov

Very nice run! What was up with those cans though, they looked giant? I don't understand why some ES decide to be tricky and try to cross people up. Just use a couple cans of corn.

4Head wrote:

killer225whale wrote:

PM2017 wrote: Was just about to ask the same question lol

I believe that ideally, you want the string to "wrap" through the path of the tip of the lever arm; The tip of the lever arm traces an arc through the air. AFAIK currently the maximum usable string length is 2x the length of the lever arm.

However, if you can get the string to pass through the arc (think of instead of a lever arm, there's a huge disc with a radius of the lever arm, and the string wraps around the edge of the disc) then the usable string length is lever arm * pi, giving you about 150% more length.

They added in extra lever arms to more closely approximate that disc; as the first lever arm reaches 60 degrees, it snags the next lever arm, and so on.

Also, this makes it so that the torque from the mousetrap's spring is more directly translated into a force pulling on the string; as the lever arm gets further away from the drive axle, less and less of the mousetrap's force goes into pulling the string.

couldn’t have said it better myself. My initial design involved an arch that would support the string as the arm moved in the arc, but it would have added too much weight. I tried a single extra arm and it ended up being basically the same speed as when I ran without it.

The benefit of the compound arm is mostly more distance, and a single arm is more than sufficient for this year’s distance. Not only that but the reversal evens out a lot of the time advantage it would give. It’s a better idea to try and reduce unnecessary weight and optimize the other parts of the vehicle.

Do you know how it is able to reverse with 2 mousetraps in a "serial" configuration?

dcambrid wrote:

mnoga wrote:I miss EV and the nice smooth floors we ran on: http://www.lmsal.com/pub/markn/EV-NorCa ... onship.mov

Very nice run! What was up with those cans though, they looked giant? I don't understand why some ES decide to be tricky and try to cross people up. Just use a couple cans of corn.

At the Golden Gate Invitational we encountered empty cans. One of the Troy teams hit a can but their car ended up only 3 cm from the target point. At the NorCal State Championship the cans contained liquid so if you hit one your car was toast.