Mousetrap Vehicle C

[Otkrlj]

I know this is a stuped question, but troy is in the black cloths withs the red letters right?

[PM2017]

I know this is a stuped question, but troy is in the black cloths withs the red letters right?

Yes. Yes they are. (It stands out so much if I recall correctly)

[nicholasmaurer]

The method you describe - launching the cup across the line while the vehicle immediately goes backward - is in violation of the rules. Rules 1. and 3.c. clearly indicate the vehicle must move one direction, and then reverse.

I believe the workaround addressed earlier was to have the vehicle move a tiny bit forward and then reverse. (I don’t know if this is legal, but it was discussed)

I have been trying to secure an FAQ, but the Ohio SES (who is involved with the event nationally) believes this violates the spirit of the problem. Others involved at the national level have given me a different interpretation. It's not clear without an FAQ what will actually be enforced in individual states, so I would recommend against this design.

EDIT: The post above was revised to reflect I have now received conflicting reports.

Update for everyone: there is now a national FAQ on this issue. As I originally stated, the cup "launcher" is NOT legal.

[DarthBuilder]

Is there a link to the response?

[PM2017]

Is there a link to the response?

https://www.soinc.org/mousetrap-vehicle.

[Kenshi Takahashi]

In Mark Rober's video, he mentioned that an MTV built for speed should have smaller wheels because you don't need rotational inertia for distance. However, does the benefit of larger diameter wheels (and thus farther distance travelled per axle rotation) balance this out, or would it be wise to invest in smaller wheels?

[4Head]

In Mark Rober's video, he mentioned that an MTV built for speed should have smaller wheels because you don't need rotational inertia for distance. However, does the benefit of larger diameter wheels (and thus farther distance travelled per axle rotation) balance this out, or would it be wise to invest in smaller wheels?

TL:DR there are too many factors for such and overarching statement to be made

Small wheels arent better for speed. They will generally lower the time score though. Consider the equation (I = mr^2 with the coefficient somewhere between 0.5 and 1). If we consult this it’ll be obvious that small wheels will accelerate the vehicle faster. Larger wheels, like you said, will have a higher top speed but given the track size will probably never be able to reach it. They also slow the reversal down a ton.

So now we know that for time score small wheels will generally win because quickly speeding up and reversing direction is more valuable than having a higher potential top speed. The problem is we’re assuming the lever arm length stays constant, which it won’t. To travel the full length of the track we will have to lengthen the lever arm as the wheels get smaller, which decreases the force applied to the axle, which increases the run time again. Not to mention axle thickness which varies the torque the axle receives also.

Fiddling with all these factors will take a lot of experimenting, unless there’s an easy way to calculate the optimal setup. I’d suggest buying a pair of mid sized wheels with reasonable mass first and optimizing your vehicle around those. Don’t consider the rotational inertia too much because you can compensate largely with lever arm length and axle thickness. In my experience picking the wheels out first has been easiest because changing wheel size implies buying an entire new set of wheels while varying the other two factors are much easier.

[Alex-RCHS]

In Mark Rober's video, he mentioned that an MTV built for speed should have smaller wheels because you don't need rotational inertia for distance. However, does the benefit of larger diameter wheels (and thus farther distance travelled per axle rotation) balance this out, or would it be wise to invest in smaller wheels?

TL:DR there are too many factors for such and overarching statement to be made

Small wheels arent better for speed. They will generally lower the time score though. Consider the equation (I = mr^2 with the coefficient somewhere between 0.5 and 1). If we consult this it’ll be obvious that small wheels will accelerate the vehicle faster. Larger wheels, like you said, will have a higher top speed but given the track size will probably never be able to reach it. They also slow the reversal down a ton.

So now we know that for time score small wheels will generally win because quickly speeding up and reversing direction is more valuable than having a higher potential top speed. The problem is we’re assuming the lever arm length stays constant, which it won’t. To travel the full length of the track we will have to lengthen the lever arm as the wheels get smaller, which decreases the force applied to the axle, which increases the run time again. Not to mention axle thickness which varies the torque the axle receives also.

Fiddling with all these factors will take a lot of experimenting, unless there’s an easy way to calculate the optimal setup. I’d suggest buying a pair of mid sized wheels with reasonable mass first and optimizing your vehicle around those. Don’t consider the rotational inertia too much because you can compensate largely with lever arm length and axle thickness. In my experience picking the wheels out first has been easiest because changing wheel size implies buying an entire new set of wheels while varying the other two factors are much easier.

Actually, unless you’re using ridiculously large wheels the rotational energy invested in the wheels accounts for very little of the vehicle’s energy. The main issue is how the spring energy is distributed over the course of the run. Our situation of having a distinct (mostly) set distance means that the energy should be distributed mostly equally between the forward run and the reverse, which you can control via the lever arm length and wheel/axle ratio.

[DarthBuilder]

Do you guys think drilling 2-7/8 T40 banebot wheels is a good idea?

[Kenshi Takahashi]

In Mark Rober's video, he mentioned that an MTV built for speed should have smaller wheels because you don't need rotational inertia for distance. However, does the benefit of larger diameter wheels (and thus farther distance travelled per axle rotation) balance this out, or would it be wise to invest in smaller wheels?

TL:DR there are too many factors for such and overarching statement to be made

Small wheels arent better for speed. They will generally lower the time score though. Consider the equation (I = mr^2 with the coefficient somewhere between 0.5 and 1). If we consult this it’ll be obvious that small wheels will accelerate the vehicle faster. Larger wheels, like you said, will have a higher top speed but given the track size will probably never be able to reach it. They also slow the reversal down a ton.

So now we know that for time score small wheels will generally win because quickly speeding up and reversing direction is more valuable than having a higher potential top speed. The problem is we’re assuming the lever arm length stays constant, which it won’t. To travel the full length of the track we will have to lengthen the lever arm as the wheels get smaller, which decreases the force applied to the axle, which increases the run time again. Not to mention axle thickness which varies the torque the axle receives also.

Fiddling with all these factors will take a lot of experimenting, unless there’s an easy way to calculate the optimal setup. I’d suggest buying a pair of mid sized wheels with reasonable mass first and optimizing your vehicle around those. Don’t consider the rotational inertia too much because you can compensate largely with lever arm length and axle thickness. In my experience picking the wheels out first has been easiest because changing wheel size implies buying an entire new set of wheels while varying the other two factors are much easier.

Actually, unless you’re using ridiculously large wheels the rotational energy invested in the wheels accounts for very little of the vehicle’s energy. The main issue is how the spring energy is distributed over the course of the run. Our situation of having a distinct (mostly) set distance means that the energy should be distributed mostly equally between the forward run and the reverse, which you can control via the lever arm length and wheel/axle ratio.

OK great. There were also a lot of people talking about making an axle thicker with tape and I was little confused on what that did or why you would do that.