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Re: Mousetrap Vehicle B

Posted: December 21st, 2012, 8:48 am
by Daniel1224
In the past we just tied the two mousetraps together and one trigger was able to hold both springs, so just don't set one of them and it should be fine.
My parter and I are trying this with our car, and we are just setting the left mousetrap. It holds just fine, but when the car is set off, it jerks to the left a bunch and doesn't go straight. Is there a way to center the area where the traps are released to avoid this? PLEASE HELP

Re: Mousetrap Vehicle B

Posted: December 21st, 2012, 6:06 pm
by Gemma W
We haven't actually built our car yet, so I'm not sure if this would actually work or not, but it seems like it - you could make the extension bar actually like a rectangle with only 3 sides, so that it attaches to the outer side of each mousetrap and forms a sort of loop. That way, even if only one mousetrap is set, the connection is such that they both move together. Not sure if I'm being clear or not, but that's the idea - tell me if it works!

Re: Mousetrap Vehicle B

Posted: December 22nd, 2012, 8:27 am
by InfiniCuber
We haven't actually built our car yet, so I'm not sure if this would actually work or not, but it seems like it - you could make the extension bar actually like a rectangle with only 3 sides, so that it attaches to the outer side of each mousetrap and forms a sort of loop. That way, even if only one mousetrap is set, the connection is such that they both move together. Not sure if I'm being clear or not, but that's the idea - tell me if it works!
This is exactly what Daniel said, but you just made the extension longer around... he already has an extension rod connected to the 2 mousetraps... just in between the two... so it is the same....just sayin :geek:

Re: Mousetrap Vehicle B

Posted: December 22nd, 2012, 9:05 am
by retired1
That is something that would have to be tried. Part of me thinks that there would be less flexing if the kill bar extension if it were put between the inner arms of the kill assembly. I doubt if you would want to run this loop out the several inches of the extension as it adds a fair bit of weight that might not be necessary.
It might not matter as bearings, axles, brakes and directional accuracy are far more important that speed--until you have all of those very good would weight be a factor.

Re: Mousetrap Vehicle B

Posted: December 25th, 2012, 12:41 am
by _HenryHscioly_
With two mousetrap together pulling same direction,
There is more force at the beginning since the spring is wound up more.
However, at the end, more spring angle(potential energy?) is used to pull the same amount of string at the beginning.
I was initially inclined to believe the mousetrap would have higher acceleration at the beginning since there is higher force, but my mousetrap seems to do better near the end.

Re: Mousetrap Vehicle B

Posted: December 25th, 2012, 1:19 pm
by retired1
That is the difference between acceleration and speed. It does not take much force to keep it going, but it takes much more to have it accelerate. Initially, you are starting at zero speed. With good bearings and axles, you will at a minimum maintain speed as you near the end of the string.

Re: Mousetrap Vehicle B

Posted: December 25th, 2012, 3:11 pm
by _HenryHscioly_
sorry that I might be answering my own question, it just suddenly jumped to my mind this morning.
When doing my theoretical calculations, I ignored sin(theta) in: torque = sin(theta) * f * r
Now that I plugged that component into my excel chart, I see that the force of the string pulling on the axle initially decreases since the decrease in torque outweighs the increase in force due to the decrease in angle between the string and the lever. However, after about 45% of the run, the force begins to increase.
But, where I want it to reverse, the force is low....I'll try to lighten up my vehicle.

Does spraying the mousetrap spring with lubrication help with decreasing friction when it release its potential energy?..or would this be considered modification of the mousetrap.

Re: Mousetrap Vehicle B

Posted: December 25th, 2012, 3:41 pm
by retired1
That lost me a bit.
The angle of the string at the axle remains close to 90 degrees through out the run. The angle that it makes with the kill bar extension should not matter as the amount of "pull" remains the same. I guess that it would make a difference if you consider the vector, but does that apply here??
Two things do change. The amount of power as the spring unwinds and the distance that the kill bar tip has to travel to get a unit of string movement at the axle.
The effectiveness of the mousetrap drops way off after the 90 degree point. The tip has to move so far to get 1 cm of distance on the string.

Re: Mousetrap Vehicle B

Posted: December 27th, 2012, 12:01 am
by _HenryHscioly_
I see that the amount of string pulled is less/angle-the-mousetrap-spring-goes-through near the end, but the force of the string on the axle will be higher near the end..maybe?

my attempt to explain:

force: tension of string; r: radius of axle; alpha: angle between string and radius of axle
torque of axle/wheel = force * r * sin(alpha)

r and alpha stay the same throughout the run
but force will not because:

radius: distance string is attached on lever from the spring; theta: angle between the force(string) and the radius(lever)
torque of mousetrap = force * radius * sin(theta)
radius/lever-length stays the same, torque of mousetrap decreases somewhat linearly, sin(theta) will decrease to zero, so force will increase significantly as sin(theta) becomes small/near-zero

Re: Mousetrap Vehicle B

Posted: December 27th, 2012, 4:15 pm
by Beastybob12345
Anyone know the best mousetrap on the market right now?
:?: