Mousetrap Vehicle C

[Wabbit]

Am I missing something, or are everyone's cars gonna be super slow this year? With the old track layout, the maximum distance that your car ever had to travel was 10 meters, and because most of that distance was going backwards towards the VTP, you could design your car to take a relatively small number of string wraps around the drive axle and just coast backwards. With the new rules, the maximum distance is 12 meters (states) and 8 of those are going forwards, which means that, at minimum, you're probably going to have to put enough string wraps on the axle to travel ~9 meters.

My initial prototype moves like a snail in comparison to last year's due to larger wheels, longer vehicle body, and smaller axle, and I'm still only barely able to go the necessary distance. Are everyone's cars going to be that slow, or am I missing something? Which one of those three characteristics (wheel size, axle diameter, and car length), do people think makes the most sense to adjust in order to increase travel differences?

(I'm aware that the last question is complex and will require a lot of trial and error in testing to really figure out. I'm just curious if people have initial thoughts on the matter.)

[windu34]

Am I missing something, or are everyone's cars gonna be super slow this year? With the old track layout, the maximum distance that your car ever had to travel was 10 meters, and because most of that distance was going backwards towards the VTP, you could design your car to take a relatively small number of string wraps around the drive axle and just coast backwards. With the new rules, the maximum distance is 12 meters (states) and 8 of those are going forwards, which means that, at minimum, your probably have to put enough string wraps on the axle to travel ~9 meters.

My initial prototype moves like a snail in comparison to last year's due to larger wheels, longer vehicle body, and smaller axle, and I'm still only barely able to go the necessary distance. Are everyone's cars going to be that slow, or am I missing something? Which one of those three characteristics (wheel size, axle diameter, and car length), do people think makes the most sense to adjust in order to increase travel differences?

(I'm aware that the last question is complex and will require a lot of trial and error in testing to really figure out. I'm just curious if people have initial thoughts on the matter.)

Not sure what you think is "super slow". Time scores will definitely be higher, but I dont think 6-7 second times at competitive tournaments is completely unreasonable. 4-5 seconds would be extremely impressive imo. Wheel and axle diameter directly affect the amount of torque you are applying so those will have a large impact. Vehicle length shouldnt have any effect, although mass certainly does

[Wabbit]

Am I missing something, or are everyone's cars gonna be super slow this year? With the old track layout, the maximum distance that your car ever had to travel was 10 meters, and because most of that distance was going backwards towards the VTP, you could design your car to take a relatively small number of string wraps around the drive axle and just coast backwards. With the new rules, the maximum distance is 12 meters (states) and 8 of those are going forwards, which means that, at minimum, your probably have to put enough string wraps on the axle to travel ~9 meters.

My initial prototype moves like a snail in comparison to last year's due to larger wheels, longer vehicle body, and smaller axle, and I'm still only barely able to go the necessary distance. Are everyone's cars going to be that slow, or am I missing something? Which one of those three characteristics (wheel size, axle diameter, and car length), do people think makes the most sense to adjust in order to increase travel differences?

(I'm aware that the last question is complex and will require a lot of trial and error in testing to really figure out. I'm just curious if people have initial thoughts on the matter.)

Not sure what you think is "super slow". Time scores will definitely be higher, but I dont think 6-7 second times at competitive tournaments is completely unreasonable. 4-5 seconds would be extremely impressive imo. Wheel and axle diameter directly affect the amount of torque you are applying so those will have a large impact. Vehicle length shouldnt have any effect, although mass certainly does

I should have said drive arm length rather than vehicle length, though the two are directly correlated. A shorter drive arm will allow for fewer string wraps, but will be significantly faster due to a higher mechanical advantage. Last year, competitive cars were significantly smaller than the 50x50 cm limit as the necessary travel distance was short and didn't require a long drive arm. This year, the maximum size has been decreased to 40x40 cm while the necessary travel distance has increased. I would expect that most cars will utilize the full 40 cm.

The caveat to the 40x40 cm rule is that it includes only the wheels of the car meaning that you could theoretically have a drive arm that was much longer than 40 cm. The issue with this idea is that, because one end of the drive arm must remain no further forward than the drive axle, the arm can only be extended by building past the non-driven wheels (on the side of the car where the mousetraps are). In doing so, the center of gravity of the car is shifted significantly, increasing the likelihood that the drive wheels lift off the ground when released (some teams were having this issue last year even without a shifted center of gravity).

[thewaffleguy]

(In your own opinion) Is it against this years rules to use electric measurement tools to align your vehicle before a run?

[antoine_ego]

Am I missing something, or are everyone's cars gonna be super slow this year? With the old track layout, the maximum distance that your car ever had to travel was 10 meters, and because most of that distance was going backwards towards the VTP, you could design your car to take a relatively small number of string wraps around the drive axle and just coast backwards. With the new rules, the maximum distance is 12 meters (states) and 8 of those are going forwards, which means that, at minimum, your probably have to put enough string wraps on the axle to travel ~9 meters.

My initial prototype moves like a snail in comparison to last year's due to larger wheels, longer vehicle body, and smaller axle, and I'm still only barely able to go the necessary distance. Are everyone's cars going to be that slow, or am I missing something? Which one of those three characteristics (wheel size, axle diameter, and car length), do people think makes the most sense to adjust in order to increase travel differences?

(I'm aware that the last question is complex and will require a lot of trial and error in testing to really figure out. I'm just curious if people have initial thoughts on the matter.)

Not sure what you think is "super slow". Time scores will definitely be higher, but I dont think 6-7 second times at competitive tournaments is completely unreasonable. 4-5 seconds would be extremely impressive imo. Wheel and axle diameter directly affect the amount of torque you are applying so those will have a large impact. Vehicle length shouldnt have any effect, although mass certainly does

Personally, I think that the minimum times will be around 10 seconds, and even this might be an underestimate. At Nationals last year where we traveled around 7 meters total, the fastest runs were about 8 seconds, with only one exception that used extremely strong, though still legal traps.

However, note that instead of having to travel only about 3-4m with the power of the traps, unless someone comes up with something really clever, a team needs to travel a minimum 9 meters. This means that the power of the traps needs to be spread out over a longer distance, reducing the speed substantially. Hence, I think that 7 second times are pretty much impossible.

[chrroh]

I know I'm a bit late on this, but I still can't figure out how to get my vehicle to stop (due to the new track design and the old wing nut system therefore being useless). I read the ideas earlier on the forum and I'm still lost. Does anyone have any ideas on how you're going to make your vehicle stop? Any videos or photos of your ideas?

Also, correct me if I'm wrong, but the Cup Distance Points are worth twice as much as the Vehicle Target Points, right? So I had the idea of adjusting the steering of my Mousetrap Vehicle (like what many did two years ago in Electric Vehicle) and prioritize having the cup touch the CTP over the vehicle touching the VTP. Is that going to be the best approach this season? Mainly because I can't see how any vehicle can get both points on the dot.

[antoine_ego]

I know I'm a bit late on this, but I still can't figure out how to get my vehicle to stop (due to the new track design and the old wing nut system therefore being useless). I read the ideas earlier on the forum and I'm still lost. Does anyone have any ideas on how you're going to make your vehicle stop? Any videos or photos of your ideas?

Also, correct me if I'm wrong, but the Cup Distance Points are worth twice as much as the Vehicle Target Points, right? So I had the idea of adjusting the steering of my Mousetrap Vehicle (like what many did two years ago in Electric Vehicle) and prioritize having the cup touch the CTP over the vehicle touching the VTP. Is that going to be the best approach this season? Mainly because I can't see how any vehicle can get both points on the dot.

I'll try to clarify what the others were saying regarding the braking system.

Suppose you have a wingnut on an axle, and nothing holding the wingnut. When you rotate the axle, the wingnut moves with it (try it yourself). Now let the wingnut ride along one side of a beam parallel to the axle. When you're going in one direction, the wingnut'll press against the beam, and travel horizontally, for example to the left. When the vehicle reverses direction, so does the axle's rotation. Now there's nothing for the wingnut to ride along, so it then rotates with the axle until it hits the other side of the beam. Now, after the reversal, the wingnut'll be traveling right, just on the other side of the beam. If you put something to stop it on that side, voila, you have a braking system!

I think it's definitely possible to get the CTP dead on since you have a decently sized cup to work with, however, getting the VTP is essentially going to be very luck based is my general feeling. Last year, very few teams could get within 1 cm consistently (I was only able to get within 2cm). However, that was with half the total distance traveled with no curve. So, I would definitely first concentrate on the cup, then work on the VTP.

[chrroh]

I know I'm a bit late on this, but I still can't figure out how to get my vehicle to stop (due to the new track design and the old wing nut system therefore being useless). I read the ideas earlier on the forum and I'm still lost. Does anyone have any ideas on how you're going to make your vehicle stop? Any videos or photos of your ideas?

Also, correct me if I'm wrong, but the Cup Distance Points are worth twice as much as the Vehicle Target Points, right? So I had the idea of adjusting the steering of my Mousetrap Vehicle (like what many did two years ago in Electric Vehicle) and prioritize having the cup touch the CTP over the vehicle touching the VTP. Is that going to be the best approach this season? Mainly because I can't see how any vehicle can get both points on the dot.

I'll try to clarify what the others were saying regarding the braking system.

Suppose you have a wingnut on an axle, and nothing holding the wingnut. When you rotate the axle, the wingnut moves with it (try it yourself). Now let the wingnut ride along one side of a beam parallel to the axle. When you're going in one direction, the wingnut'll press against the beam, and travel horizontally, for example to the left. When the vehicle reverses direction, so does the axle's rotation. Now there's nothing for the wingnut to ride along, so it then rotates with the axle until it hits the other side of the beam. Now, after the reversal, the wingnut'll be traveling right, just on the other side of the beam. If you put something to stop it on that side, voila, you have a braking system!

I think it's definitely possible to get the CTP dead on since you have a decently sized cup to work with, however, getting the VTP is essentially going to be very luck based is my general feeling. Last year, very few teams could get within 1 cm consistently (I was only able to get within 2cm). However, that was with half the total distance traveled with no curve. So, I would definitely first concentrate on the cup, then work on the VTP.

Ahhh, I get it now! Thanks for the advice, it helps A LOT.

[Otkrlj]

Hey what material do you think is going to be best for building the body this year. I would assume balsa wood or carbon fiber, but with the weird rules this year, I wanted to make sure those were still viable.

[PM2017]

Hey what material do you think is going to be best for building the body this year. I would assume balsa wood or carbon fiber, but with the weird rules this year, I wanted to make sure those were still viable.

I would be wary of balsa, simply because steering has to be adjustable, and I would want to minimise weird torsion on my car. The one I'm currently buidling uses CF.

(In your own opinion) Is it against this years rules to use electric measurement tools to align your vehicle before a run?

I would say no (they are not allowed), since the rules are very specific as to what electronic devices may be used for. Someone should probably submit an FAQ regardless.