Mousetrap Vehicle C

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Re: Mousetrap Vehicle C

Postby dcambrid » Tue Sep 11, 2018 3:11 pm

So I am wondering how teams will align their steering if you use the set steering like EV. You cannot use a digital caliper attached to the vehicle since no electronic parts are allowed. For EV we used a non attached caliper to set the steering, but the rules this year state that you can have an electronic calculator and no other electronic tools, which means no digital calipers that are non attached either. Setting the steering without that degree of accuracy will be difficult. You can use a manual caliper, but that will be tough.

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Re: Mousetrap Vehicle C

Postby windu34 » Tue Sep 11, 2018 7:06 pm

dcambrid wrote:So I am wondering how teams will align their steering if you use the set steering like EV. You cannot use a digital caliper attached to the vehicle since no electronic parts are allowed. For EV we used a non attached caliper to set the steering, but the rules this year state that you can have an electronic calculator and no other electronic tools, which means no digital calipers that are non attached either. Setting the steering without that degree of accuracy will be difficult. You can use a manual caliper, but that will be tough.

Why would that be tough? Dial calipers are used very commonly in industry and have comparable levels of precision
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Re: Mousetrap Vehicle C

Postby 4Head » Wed Sep 12, 2018 1:33 am

windu34 wrote:
dcambrid wrote:So I am wondering how teams will align their steering if you use the set steering like EV. You cannot use a digital caliper attached to the vehicle since no electronic parts are allowed. For EV we used a non attached caliper to set the steering, but the rules this year state that you can have an electronic calculator and no other electronic tools, which means no digital calipers that are non attached either. Setting the steering without that degree of accuracy will be difficult. You can use a manual caliper, but that will be tough.

Why would that be tough? Dial calipers are used very commonly in industry and have comparable levels of precision

they're insanely precise. I'm just worried about the weight. Metal calipers are pretty heavy?
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Re: Mousetrap Vehicle C

Postby Unome » Wed Sep 12, 2018 1:59 am

4Head wrote:
windu34 wrote:
dcambrid wrote:So I am wondering how teams will align their steering if you use the set steering like EV. You cannot use a digital caliper attached to the vehicle since no electronic parts are allowed. For EV we used a non attached caliper to set the steering, but the rules this year state that you can have an electronic calculator and no other electronic tools, which means no digital calipers that are non attached either. Setting the steering without that degree of accuracy will be difficult. You can use a manual caliper, but that will be tough.

Why would that be tough? Dial calipers are used very commonly in industry and have comparable levels of precision

they're insanely precise. I'm just worried about the weight. Metal calipers are pretty heavy?

...oh yeah...

From some quick research, they weigh about 120-150 grams. Clearly a lot more important for this event than for EV.
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Re: Mousetrap Vehicle C

Postby windu34 » Wed Sep 12, 2018 4:02 am

Unome wrote:
4Head wrote:
windu34 wrote:Why would that be tough? Dial calipers are used very commonly in industry and have comparable levels of precision

they're insanely precise. I'm just worried about the weight. Metal calipers are pretty heavy?

...oh yeah...

From some quick research, they weigh about 120-150 grams. Clearly a lot more important for this event than for EV.

There are also plastic dial calipers, although those have a different problem that will need to be overcome
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Re: Mousetrap Vehicle C

Postby MangoTTT » Wed Sep 12, 2018 4:52 pm

I'm really lost how do you use a caliper to adjust the direction the MV moves in? Can someone explain it to me???

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Re: Mousetrap Vehicle C

Postby Aristotle » Wed Sep 12, 2018 8:54 pm

MangoTTT wrote:I'm really lost how do you use a caliper to adjust the direction the MV moves in? Can someone explain it to me???


Basically, drilling a hole in the caliper and fitting a bearing to allow for adjustable steering. Watch this: https://www.youtube.com/watch?v=pKC8MYRgflI

I was interested in what windu said about being more efficient with the mousetraps. I had a few ideas/questions. First, do two mousetraps really provide a double output power compared to one (has anyone actually tested this?). If there's a difference in theoretical vs experimental output, perhaps a lighter car will be more advantageous.

Second, does anyone know about using mousetrap in a series instead of joined together? While this would be harder to do, you could technically have the first mousetrap release halfway and coast (allowing for more power output and speed). The problem would be in timing and deploying the second mousetrap.

Finally, is there an advantage in using a compound lever design? Or maybe having one mousetrap deploy an initial lever and the other mousetrap deploy another one halfway through propelling the string of the first mousetrap. If the goal is to create a more circular arc with multiple compound lever arms, then wouldn't a semicircle cutout like this be more useful? (https://www.youtube.com/watch?v=EWV_VKcS0rk)

Just some ideas, would love to hear thoughts

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Re: Mousetrap Vehicle C

Postby PM2017 » Thu Sep 13, 2018 2:26 am

Aristotle wrote:
MangoTTT wrote:I'm really lost how do you use a caliper to adjust the direction the MV moves in? Can someone explain it to me???


Basically, drilling a hole in the caliper and fitting a bearing to allow for adjustable steering. Watch this: https://www.youtube.com/watch?v=pKC8MYRgflI

I was interested in what windu said about being more efficient with the mousetraps. I had a few ideas/questions. First, do two mousetraps really provide a double output power compared to one (has anyone actually tested this?). If there's a difference in theoretical vs experimental output, perhaps a lighter car will be more advantageous.

Second, does anyone know about using mousetrap in a series instead of joined together? While this would be harder to do, you could technically have the first mousetrap release halfway and coast (allowing for more power output and speed). The problem would be in timing and deploying the second mousetrap.

Finally, is there an advantage in using a compound lever design? Or maybe having one mousetrap deploy an initial lever and the other mousetrap deploy another one halfway through propelling the string of the first mousetrap. If the goal is to create a more circular arc with multiple compound lever arms, then wouldn't a semicircle cutout like this be more useful? (https://www.youtube.com/watch?v=EWV_VKcS0rk)

Just some ideas, would love to hear thoughts

Ok, as for your last statement, because the car was to travel a significant distance, including a change in direction, the lever arm would need to be longer. Thus, the semicircle cut-out would need to be larger, adding weight proportional to the square of the increased distance.

Also, if you think about it, the semicircle cutout, which starts being only useful halfway through, gives you a string multiplier of (pi/4+sqrt(0.5^2+0.5^2), because that is the arc length of a quarter circle of diameter of 1 added to an isosceles triangle with length 0.5. This yields a raw value of about 1.49 times. The three lever arm design basically creates a half hexagon which is 1 inch from one corner to the opposite corner. The side length of a regular hexagon is the same as its radius. (you can verify this here: https://www.mathopenref.com/polygonradius.html. So, with you get a string multiplier of (0.5/side*3sides), which is 1.5. This is slightly greater than that of the semicircle, and adds less weight.

Now if you could make a telescoping arc that is connected to the lever arm, and attaches right next to the axle, that would get you basically as close as possible to the pi/2 = 1.57 multiplier maximum.
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Re: Mousetrap Vehicle C

Postby DarthBuilder » Thu Sep 13, 2018 10:10 pm

Has there been any clarification of the track or is the one posted earlier in this thread is pretty accurate?
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Re: Mousetrap Vehicle C

Postby windu34 » Fri Sep 14, 2018 5:57 pm

PM2017 wrote:Ok, as for your last statement, because the car was to travel a significant distance, including a change in direction, the lever arm would need to be longer. Thus, the semicircle cut-out would need to be larger, adding weight proportional to the square of the increased distance.

Why are you assuming the semicircle has to be a solid piece of material? You could hollow out the wooden piece in the video or use a different method to create the same effect
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Re: Mousetrap Vehicle C

Postby PM2017 » Sat Sep 15, 2018 12:23 am

windu34 wrote:
PM2017 wrote:Ok, as for your last statement, because the car was to travel a significant distance, including a change in direction, the lever arm would need to be longer. Thus, the semicircle cut-out would need to be larger, adding weight proportional to the square of the increased distance.

Why are you assuming the semicircle has to be a solid piece of material? You could hollow out the wooden piece in the video or use a different method to create the same effect

Oops, I realized that after I wrote my post, and forgot to edit it. Actually, I can see this working really well.
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Re: Mousetrap Vehicle C

Postby antoine_ego » Sat Sep 15, 2018 12:52 am

Instead of doing a semicircle, you might try using swinging arms. This gives the same effect as the semi circle, but you won't have to have some sort of horizontal bar near the tip. The catch is that the swinging arms are kinda hard to make.
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Re: Mousetrap Vehicle C

Postby PM2017 » Sat Sep 15, 2018 1:47 am

antoine_ego wrote:Instead of doing a semicircle, you might try using swinging arms. This gives the same effect as the semi circle, but you won't have to have some sort of horizontal bar near the tip. The catch is that the swinging arms are kinda hard to make.

This whole conversation was in response to someone asking why you couldn't use a semicircle instead of the arms.
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Re: Mousetrap Vehicle C

Postby astro12345 » Sun Sep 16, 2018 12:26 am

Are people using front axle braking systems or back axle braking systems this year? With the addition of adjustable curved steering I feel like a front axle braking system might be harder.

I was thinking of trying to use a back axle breaking system, but unless I drastically change the torque on the wheel or find axles with more threads per inch I won't be able to have the power system in the center of the axle. Has anyone tried having the area where the string wraps around the axle be way to the edge? if so, did it work?

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Re: Mousetrap Vehicle C

Postby retired1 » Sun Sep 16, 2018 9:08 pm

astro12345 wrote:Are people using front axle braking systems or back axle braking systems this year? With the addition of adjustable curved steering I feel like a front axle braking system might be harder.

I was thinking of trying to use a back axle breaking system, but unless I drastically change the torque on the wheel or find axles with more threads per inch I won't be able to have the power system in the center of the axle. Has anyone tried having the area where the string wraps around the axle be way to the edge? if so, did it work?


Major problem with enough string to go all of the way to the edge for many.It is not easy to not have the string overlap at any point as this changes the diameter of the axle.

Common axle material that is threaded would be 1/4 20, 1/4 28 . Would have to look up 3/16, 1/8 TPI. 4 40 is available but it bends much easier and is commonly brass rather than a harder material.
Metric sizes are available but tend to cost more and are typically harder to find.

If you do not need threads, brass tubing is available in many diameters.

There are several ways to attach the wheels.


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