Mousetrap Vehicle C

terence.tan
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Re: Mousetrap Vehicle C

Postby terence.tan » April 8th, 2018, 1:52 pm

Fridaychimp wrote:
MangoTTT wrote:Hey any prediction on rules for next year for mousetrap? I feel there's not a lot to add...

I guess they could make the cup target line variable as well.

that would be very interesting

and lets say they do the center line can, would it be even possible to make a slight turn mid run. I cant really think of a mechanism that is capable of doing that
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Re: Mousetrap Vehicle C

Postby PM2017 » April 8th, 2018, 1:59 pm

terence.tan wrote:
Fridaychimp wrote:
MangoTTT wrote:Hey any prediction on rules for next year for mousetrap? I feel there's not a lot to add...

I guess they could make the cup target line variable as well.

that would be very interesting

and lets say they do the center line can, would it be even possible to make a slight turn mid run. I cant really think of a mechanism that is capable of doing that

I can think of one but its overly complicated. Instead it should probably be going in an arc rather than a line with a bump.
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Re: Mousetrap Vehicle C

Postby PM2017 » April 8th, 2018, 2:04 pm

What about a game where you there is also a horizontal aspect to it. Like you go a certain distance straight forward to get points, then you have to turn to go diagonally.
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Re: Mousetrap Vehicle C

Postby Nletts19 » April 9th, 2018, 11:04 am

I'm hoping we don't have a center line can, it makes testing miserable.

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Re: Mousetrap Vehicle C

Postby DarthBuilder » April 9th, 2018, 12:29 pm

But if anything, I can see this happening the most


Just a simple start line and the target point is 7-9 meters
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Re: Mousetrap Vehicle C

Postby Alex-RCHS » April 9th, 2018, 4:38 pm

Our team has been having an issue where the car rolls perfectly straight on the route forward, but is off by a substantial distance on the route back. We think that either:
A. The car "shifts" on the reversal and, as a result, is at an angle to the center on the route backward
OR
B. The car somehow runs on a perfectly straight line on the forward route but runs on a slight curve on the route backward (without any shift).
Or there's some other issue that I haven't considered.

Our car has Banebot 2 7/8 inch diameter wheels with ball bearings. It weighs 370g and we have been achieving times of about 9-10 seconds.

I would love any and all help!
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Re: Mousetrap Vehicle C

Postby terence.tan » April 9th, 2018, 5:15 pm

Alex-RCHS wrote:Our team has been having an issue where the car rolls perfectly straight on the route forward, but is off by a substantial distance on the route back. We think that either:
A. The car "shifts" on the reversal and, as a result, is at an angle to the center on the route backward
OR
B. The car somehow runs on a perfectly straight line on the forward route but runs on a slight curve on the route backward (without any shift).
Or there's some other issue that I haven't considered.

Our car has Banebot 2 7/8 inch diameter wheels with ball bearings. It weighs 370g and we have been achieving times of about 9-10 seconds.

I would love any and all help!


So i had the same issue at first. What i did was angle the mtv a bit to the opposite direction of where it curved on the way back when setting it up. This will cause your mtv to curve when going foward but then straighten out when going back. You should keep testing until you find the sweet spot. hope this helps

Also how are your times 9 sec. how long is your lever arm?
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Re: Mousetrap Vehicle C

Postby Alex-RCHS » April 9th, 2018, 5:56 pm

terence.tan wrote:
Alex-RCHS wrote:Our team has been having an issue where the car rolls perfectly straight on the route forward, but is off by a substantial distance on the route back. We think that either:
A. The car "shifts" on the reversal and, as a result, is at an angle to the center on the route backward
OR
B. The car somehow runs on a perfectly straight line on the forward route but runs on a slight curve on the route backward (without any shift).
Or there's some other issue that I haven't considered.

Our car has Banebot 2 7/8 inch diameter wheels with ball bearings. It weighs 370g and we have been achieving times of about 9-10 seconds.

I would love any and all help!


So i had the same issue at first. What i did was angle the mtv a bit to the opposite direction of where it curved on the way back when setting it up. This will cause your mtv to curve when going foward but then straighten out when going back. You should keep testing until you find the sweet spot. hope this helps

Also how are your times 9 sec. how long is your lever arm?

Thanks for the help. We’ve already tried offsetting the cars angle at launch — it helps but it’s a bit inconsistent. I was hoping to find a way to make it actually shoot straight.

As for the lever arm, it’s about 17cm.
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Re: Mousetrap Vehicle C

Postby terence.tan » April 9th, 2018, 6:13 pm

Alex-RCHS wrote:
terence.tan wrote:
Alex-RCHS wrote:Our team has been having an issue where the car rolls perfectly straight on the route forward, but is off by a substantial distance on the route back. We think that either:
A. The car "shifts" on the reversal and, as a result, is at an angle to the center on the route backward
OR
B. The car somehow runs on a perfectly straight line on the forward route but runs on a slight curve on the route backward (without any shift).
Or there's some other issue that I haven't considered.

Our car has Banebot 2 7/8 inch diameter wheels with ball bearings. It weighs 370g and we have been achieving times of about 9-10 seconds.

I would love any and all help!


So i had the same issue at first. What i did was angle the mtv a bit to the opposite direction of where it curved on the way back when setting it up. This will cause your mtv to curve when going foward but then straighten out when going back. You should keep testing until you find the sweet spot. hope this helps

Also how are your times 9 sec. how long is your lever arm?

Thanks for the help. We’ve already tried offsetting the cars angle at launch — it helps but it’s a bit inconsistent. I was hoping to find a way to make it actually shoot straight.

As for the lever arm, it’s about 17cm.

There is no quick fix to this problem. So if you have a competition soon you should practice offsetting the mtv. Because i didnt know how to fix this problem so i spent a lot of time just testing, until offsetting it consistently became a second nature and i got really good at it. My distance scores on average are less than 2, so you should give it a try

Also how thick is your driver axle ?
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Re: Mousetrap Vehicle C

Postby Alex-RCHS » April 9th, 2018, 6:31 pm

terence.tan wrote:
Alex-RCHS wrote:
terence.tan wrote:
So i had the same issue at first. What i did was angle the mtv a bit to the opposite direction of where it curved on the way back when setting it up. This will cause your mtv to curve when going foward but then straighten out when going back. You should keep testing until you find the sweet spot. hope this helps

Also how are your times 9 sec. how long is your lever arm?

Thanks for the help. We’ve already tried offsetting the cars angle at launch — it helps but it’s a bit inconsistent. I was hoping to find a way to make it actually shoot straight.

As for the lever arm, it’s about 17cm.

There is no quick fix to this problem. So if you have a competition soon you should practice offsetting the mtv. Because i didnt know how to fix this problem so i spent a lot of time just testing, until offsetting it consistently became a second nature and i got really good at it. My distance scores on average are less than 2, so you should give it a try

Also how thick is your driver axle ?

4mm.
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Re: Mousetrap Vehicle C

Postby dcambrid » April 15th, 2018, 11:19 am

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

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Re: Mousetrap Vehicle C

Postby Ten086 » April 15th, 2018, 9:41 pm

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?
Just trying my best...

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Re: Mousetrap Vehicle C

Postby PM2017 » April 15th, 2018, 10:35 pm

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
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Re: Mousetrap Vehicle C

Postby killer225whale » April 17th, 2018, 9:41 am

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.

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Re: Mousetrap Vehicle C

Postby 4Head » April 17th, 2018, 8:59 pm

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.
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